Oligothiophenes with specific photophysical properties and molecular organization are of great interest, since this class of materials are used in organic electronics and bioelectronics, as well as biosensing. Herein, 8 different pentameric oligothiophenes, denoted proteophenes, with different amino acid substitution patterns at distinct positions along the thiophene backbone were investigated. Spectroscopic and microscopic studies of the ligands revealed the formation of optically active self-assembled materials under acidic or basic conditions. The distinct photophysical characteristics, including induced circular dichroism, as well as the supramolecular structures of the assemblies deduced from light scattering and transmission electron microscopy, were highly influenced by the positioning of distinct amino acid moieties along the thiophene backbone. Proteophenes functionalized with only glutamate residues or these functionalities in combination with hydrophobic valine moieties formed fibrillar structures with excellent chiroptical properties under acidic conditions. In addition, the amino acid functionality at the beta-position of distinct thiophene moieties influenced the induced circular dichroism pattern observed from the proteophenes. Overall, the obtained results demonstrate how changes in the position of various amino acid functionalities, as well as the chemical nature of the amino acid side chain functionality greatly affect the optical properties as well as the architecture of the self-assembled materials. Self-assembled Proteophenes. Oligothiophenes with distinct amino acid side-chain functionalities along the conjugated backbone displayed distinct chiroptical and structural properties in acidic or alkaline solutions. The distinct photophysical characteristics, as well as the supramolecular structures of the assemblies were highly influenced by the chemical nature of the amino acid, as well as the positioning of distinct amino acid moieties along the thiophene backbone.image

The amyloid beta (A beta) peptide has a central role in Alzheimer's disease (AD) pathology. The peptide length can vary between 37 and 49 amino acids, with A beta 1-42 being considered the most disease-related length. However, A beta 1-40 is also found in A beta plaques and has shown to form intertwined fibrils with A beta 1-42. The peptides have previously also shown to form different fibril conformations, proposed to be related to disease phenotype. To conduct more representative in vitro experiments, it is vital to uncover the impact of different fibril conformations on neurons. Hence, we fibrillized different A beta 1-40:42 ratios in concentrations of 100:0, 90:10, 75:25, 50:50, 25:75, 10:90 and 0:100 for either 24 h (early fibrils) or 7 days (aged fibrils). These were then characterized based on fibril width, LCO-staining and antibody-staining. We further challenged differentiated neuronal-like SH-SY5Y human cells with the different fibrils and measured A beta content, cytotoxicity and autophagy function at three different time-points: 3, 24, and 72 h. Our results revealed that both A beta 1-40:42 ratio and fibril maturation affect conformation of fibrils. We further show the impact of these conformation changes on the affinity to commonly used A beta antibodies, primarily affecting A beta 1-40 rich aggregates. In addition, we demonstrate uptake of the aggregates by neuronally differentiated human cells, where aggregates with higher A beta 1-42 ratios generally caused higher cellular levels of A beta. These differences in A beta abundance did not cause changes in cytotoxicity nor in autophagy activation. Our results show the importance to consider conformational differences of A beta fibrils, as this can have fundamental impact on A beta antibody detection. Overall, these insights underline the need for further exploration of the impact of conformationally different fibrils and the need to reliably produce disease relevant A beta aggregates.image

Amyloid plaques composed of fibrils of misfolded A beta peptides are pathological hallmarks of Alzheimer's disease (AD). A beta fibrils are polymorphic in their tertiary and quaternary molecular structures. This structural polymorphism may carry different pathologic potencies and can putatively contribute to clinical phenotypes of AD. Therefore, mapping of structural polymorphism of A beta fibrils and structural evolution over time is valuable to understanding disease mechanisms. Here, we investigated how A beta fibril structures in situ differ in A beta plaque of different mouse models expressing familial mutations in the A beta PP gene. We imaged frozen brains with a combination of conformation-sensitive luminescent conjugated oligothiophene (LCO) ligands and A beta-specific antibodies. LCO fluorescence mapping revealed that mouse models APP23, APPPS1, and App(NL-F) have different fibril structures within A beta-amyloid plaques depending on the A beta PP-processing genotype. Co-staining with A beta-specific antibodies showed that individual plaques from APP23 mice expressing A beta PP Swedish mutation have two distinct fibril polymorph regions of core and corona. The plaque core is predominantly composed of compact A beta 40 fibrils, and the corona region is dominated by diffusely packed A beta 40 fibrils. Conversely, the A beta PP knock-in mouse App(NL-F), expressing the A beta PP Iberian mutation along with Swedish mutation has tiny, cored plaques consisting mainly of compact A beta 42 fibrils, vastly different from APP23 even at elevated age up to 21 months. Age-dependent polymorph rearrangement of plaque cores observed for APP23 and APPPS1 mice >12 months, appears strongly promoted by A beta 40 and was hence minuscule in App(NL-F). These structural studies of amyloid plaques in situ can map disease-relevant fibril polymorph distributions to guide the design of diagnostic and therapeutic molecules.

The amyloidoses are diseases caused by accumulation of amyloid fibrils from over 40 different human misfolded proteins in various organs of the body depending on precursor protein. Amyloidogenesis is a self-perpetuating reaction with deleterious consequences causing degeneration in cells and organs where depositions occur. Transthyretin, TTR, is an amyloidogenic protein causing sporadic disease from the wild-type protein during aging and from numerous different autosomal dominant familial mutations at earlier ages depending on the sequence of the hereditary variant. Until recently the disease process was poorly understood, and therapies were scarce. Over the past decades, spurred by clinical data, using chemical biology research, the mechanisms of TTR production and misfolding have been elucidated affording almost complete coverage of the TTR amyloidogenesis pathway to be targeted. This translational science success has provided a plethora of therapeutic options for the TTR amyloidoses providing an inspiring example for success in previously intractable diseases. image

Misfolding and aggregation of transthyretin (TTR) causeseveralamyloid diseases. Besides being an amyloidogenic protein, TTR hasan affinity for bicyclic small-molecule ligands in its thyroxine (T4)binding site. One class of TTR ligands are trans-stilbenes. The trans-stilbenescaffold is also widely applied for amyloid fibril-specific ligandsused as fluorescence probes and as positron emission tomography tracersfor amyloid detection and diagnosis of amyloidosis. We have shownthat native tetrameric TTR binds to amyloid ligands based on the trans-stilbenescaffold providing a platform for the determination of high-resolutionstructures of these important molecules bound to protein. In thisstudy, we provide spectroscopic evidence of binding and X-ray crystallographicstructure data on tetrameric TTR complex with the fluorescent salicylicacid-based pyrene amyloid ligand (Py1SA), an analogue of the Congored analogue X-34. The ambiguous electron density from the X-ray diffraction,however, did not permit Py1SA placement with enough confidence likelydue to partial ligand occupancy. Instead, the preferred orientationof the Py1SA ligand in the binding pocket was determined by moleculardynamics and umbrella sampling approaches. We find a distinct preferencefor the binding modes with the salicylic acid group pointing intothe pocket and the pyrene moiety outward to the opening of the T4binding site. Our work provides insight into TTR binding mode preferencefor trans-stilbene salicylic acid derivatives as well as a frameworkfor determining structures of TTR-ligand complexes.

Background: Early detection of amyloid-beta(A beta) aggregates is a critical step to improve the treatment of Alzheimers disease (AD) because neuronal damage by the A beta aggregates occurs before clinical symptoms are apparent. We have previously shown that luminescent conjugated oligothiophenes (LCOs), which are highly specific towards protein aggregates of A beta, can be used to fluorescently label amyloid plaque in living rodents. Objective: We hypothesize that the LCO can be used to target gadolinium to the amyloid plaque and hence make the plaque detectable by T-1-weighted magnetic resonance imaging (MRI). Methods: A novel LCO-gadolinium construct was synthesized to selectively bind to A beta plaques and give contrast in conventional T-1-weighted MR images after intravenous injection in Tg-APPSwe mice. Results: We found that mice with high plaque-burden could be identified using the LCO-Gd constructs by conventional MRI. Conclusion: Our study shows that MR imaging of amyloid plaques is challenging but feasible, and hence contrast-mediated MR imaging could be a valuable tool for early AD detection.

The orientations of ligands bound to the transthyretin (TTR) thyroxine (T4) binding site are difficult to predict. Conflicting binding modes of resveratrol have been reported. We previously reported two resveratrol based trans-stilbene fluorescent ligands, (E)-4-(2-(naphthalen-1-yl)vinyl)benzene-1,2-diol (SB-11) and (E)-4-(2-(naphthalen-2-yl)vinyl)-benzene-1,2-diol (SB-14), that bind native and misfolded protofibrillar TTR. The binding orientations of these two analogous ligands to native tetrameric TTR were predicted to be opposite. Herein we report the crystal structures of these TTR:ligand complexes. Opposite binding modes were verified but were different than predicted. The reverse binding mode (SB14) placing the naphthalene moiety toward the opening of the binding pocket renders the fluorescent ligand pH sensitive due to changes in Lys15 amine protonation. Conversely, the forward binding mode (SB-11) placing the naphthalene inward mediates a stabilizing conformational change, allowing intersubunit H-bonding between Ser117 of different monomers across the dimer interface. Our structures of TTR complexes answer important questions in ligand design and interpretation of trans-stilbene binding modes to the TTR T4 binding site.

The crosstalk between viral infections, amyloid formation and neurodegeneration has been discussed with varying intensity since the last century. Several viral proteins are known to be amyloidogenic. Post-acute sequalae (PAS) of viral infections is known for several viruses. SARS-CoV-2 and COVID-19 implicate connections between amyloid formation and severe outcomes in the acute infection, PAS and neurodegenerative diseases. Is the amyloid connection causation or just correlation? In this review we highlight several aspects where amyloids and viruses meet. The evolutionary driving forces that dictate protein amyloid formation propensity are different for viruses compared to prokaryotes and eukaryotes, while posttranslational endoproteolysis appears to be a common mechanism leading up to amyloid formation for both viral and human proteins. Not only do human and viral proteins form amyloid irrespective of each other but there are also several examples of co-operativity between amyloids, viruses and the inter-, and intra-host spread of the respective entity. Abnormal blood clotting in severe and long COVID and as a side effect in some vaccine recipients has been connected to amyloid formation of both the human fibrin and the viral Spike-protein. We conclude that there are many intersects between viruses and amyloids and, consequently, amyloid and virus research need to join forces here. We emphasize the need to accelerate development and implementation in clinical practice of antiviral drugs to preclude PAS and downstream neurological damage. There is also an ample need for retake on suitable antigen targets for the further development of next generation of vaccines against the current and coming pandemics.

SARS-CoV-2 infection is associated with a surprising number of morbidities. Uncanny similarities with amyloid-disease associated blood coagulation andfibrinolytic disturbances together with neurologic and cardiac problems led us to investigatethe amyloidogenicity of the SARS-CoV-2 spike protein (S-protein). Amyloidfibril assays of peptide library mixtures and theoreticalpredictions identified seven amyloidogenic sequences within the S-protein. All seven peptides in isolation formed aggregates duringincubation at 37 degrees C. Three 20-amino acid long synthetic spike peptides (sequence 192-211, 601-620, 1166-1185) fulfilled threeamyloidfibril criteria: nucleation dependent polymerization kinetics by ThT, Congo red positivity, and ultrastructuralfibrillarmorphology. Full-length folded S-protein did not form amyloidfibrils, but amyloid-likefibrils with evident branching were formedduring 24 h of S-protein coincubation with the protease neutrophil elastase (NE)in vitro.NEefficiently cleaved S-protein, renderingexposure of amyloidogenic segments and accumulation of the amyloidogenic peptide 194-203, part of the most amyloidogenicsynthetic spike peptide. NE is overexpressed at inflamed sites of viral infection. Our data propose a molecular mechanism forpotential amyloidogenesis of SARS-CoV-2 S-protein in humans facilitated by endoproteolysis. The prospective of S-proteinamyloidogenesis in COVID-19 disease associated pathogenesis can be important in understanding the disease and long COVID-19.

Neurodegenerative diseases (NDs) are associated with accumulated misfolded proteins (MPs). MPs oligomerize and form multiple forms of amyloid fibril polymorphs that dictate fibril propagation and cellular dysfunction. Protein misfolding processes that impair protein homeostasis are implicated in onset and progression of NDs. A wide variety of molecular chaperones safeguard the cell from MP accumulation. A rather overlooked molecular chaperone is HSP10, known as a co-chaperone for HSP60. Due to the ubiquitous presence in human tissues and protein overabundance compared with HSP60, we studied how HSP10 alone influences fibril formation in vitro of Alzheimers disease-associated A beta 1-42. At sub-stoichiometric concentrations, eukaryotic HSP10s (human and Drosophila) significantly influenced the fibril formation process and the fibril structure of A beta 1-42, more so than the prokaryotic HSP10 GroES. Similar effects were observed for prion disease-associated prion protein HuPrP90-231. Paradoxically, for a chaperone, low concentrations of HSP10 appeared to promote fibril nucleation by shortened lag-phases, which were chaperone and substrate dependent. Higher concentrations of chaperone while still sub-stoichiometric extended the nucleation and/or the elongation phase. We hypothesized that HSP10 by means of its seven mobile loops provides the chaperone with high avidity binding to amyloid fibril ends. The preserved sequence of the edge of the mobile loop GGIM(V)L (29-33 human numbering) normally dock to the HSP60 apical domain. Interestingly, this segment shows sequence similarity to amyloidogenic core segments of A beta 1-42, GGVVI (37-41), and HuPrP90-231 GGYML (126-130) likely allowing efficient competitive binding to fibrillar conformations of these MPs. Our results propose that HSP10 can function as an important molecular chaperone in human proteostasis in NDs.

Aim: To propose a new multimodal imaging agent targeting amyloid-beta (A beta) plaques in Alzheimers disease. Materials & methods: A new generation of hybrid contrast agents, based on gadolinium fluoride nanoparticles grafted with a pentameric luminescent-conjugated polythiophene, was designed, extensively characterized and evaluated in animal models of Alzheimers disease through MRI, two-photon microscopy and synchrotron x-ray phase-contrast imaging. Results & conclusion: Two different grafting densities of luminescent-conjugated polythiophene were achieved while preserving colloidal stability and fluorescent properties, and without affecting biodistribution. In vivo brain uptake was dependent on the blood-brain barrier status. Nevertheless, multimodal imaging showed successful A beta targeting in both transgenic mice and A beta fibril-injected rats.

Cerebrospinal fluid (CSF) biomarkers play an important role in diagnosing Alzheimers disease (AD) which is characterized by amyloid-beta (A beta) amyloidosis. Here, we used two App knock-in mouse models, App(NL-F/NL-F) and App(NL-G-F/NL-G-F), exhibiting AD-like A beta pathology to analyze how the brain pathologies translate to CSF proteomes by label-free mass spectrometry (MS). This identified several extracellular matrix (ECM) proteins as significantly altered in App knock-in mice. Next, we compared mouse CSF proteomes with previously reported human CSF MS results acquired from patients across the AD spectrum. Intriguingly, the ECM protein decorin was similarly and significantly increased in both App(NL-F/NL-F) and App(NL-G-F/NL-G-F) mice, strikingly already at three months of age in the App(NL-F/NL-F) mice and preclinical AD subjects having abnormal CSF-A beta 42 but normal cognition. Notably, in this group of subjects, CSF-decorin levels positively correlated with CSF-A beta 42 levels indicating that the change in CSF-decorin is associated with early A beta amyloidosis. Importantly, receiver operating characteristic analysis revealed that CSF-decorin can predict a specific AD subtype having innate immune activation and potential choroid plexus dysfunction in the brain. Consistently, in App(NL-F/NL-F) mice, increased CSF-decorin correlated with both AP plaque load and with decorin levels in choroid plexus. In addition, a low concentration of human A beta 42 induces decorin secretion from mouse primary neurons. Interestingly, we finally identify decorin to activate neuronal autophagy through enhancing lysosomal function. Altogether, the increased CSF-decorin levels occurring at an early stage of A beta amyloidosis in the brain may reflect pathological changes in choroid plexus, present in a subtype of AD subjects.

Amyloid beta (A beta) deposition in the neocortex is a major hallmark of Alzheimers disease (AD), but the extent of deposition does not readily explain phenotypic diversity and rate of disease progression. The prion strain-like model of disease heterogeneity suggests the existence of different conformers of A beta. We explored this paradigm using conformation-dependent immunoassay (CDI) for A beta and conformation-sensitive luminescent conjugated oligothiophenes (LCOs) in AD cases with variable progression rates. Mapping the A beta conformations in the frontal, occipital, and temporal regions in 20 AD patients with CDI revealed extensive interindividual and anatomical diversity in the structural organization of A beta with the most significant differences in the temporal cortex of rapidly progressive AD. The fluorescence emission spectra collected in situ from A beta plaques in the same regions demonstrated considerable diversity of spectral characteristics of two LCOs-quatroformylthiophene acetic acid and heptaformylthiophene acetic acid. Heptaformylthiophene acetic acid detected a wider range of A beta deposits, and both LCOs revealed distinct spectral attributes of diffuse and cored plaques in the temporal cortex of rapidly and slowly progressive AD and less frequent and discernible differences in the frontal and occipital cortex. These and CDI findings indicate a major conformational diversity of A beta accumulating in the neocortex, with the most notable differences in temporal cortex of cases with shorter disease duration, and implicate distinct A beta conformers (strains) in the rapid progression of AD.

CBD-2115 was selected from a library of 148 compounds based on a pyridinyl-indole scaffold as a first-in-class 4R-tau radiotracer. In vitro binding assays showed [H-3]CBD-2115 had a K-D value of 6.9 nM and a nominal B-max of 500 nM in 4R-tau expressing P301L transgenic mouse tissue. In binding assays with human brain tissue homogenates, [H-3]CBD-2115 has a higher affinity (4.9 nM) for progressive supranuclear palsy specific 4R-tau deposits than [H-3]flortaucipir (45 nM) or [H-3]MK-6240 (>50 nM). [F-18]CBD-2115 was reliably synthesized (3-11% radiochemical yield with molar activity of 27-111 GBq/mu mol and >97% radiochemical purity). Dynamic PET imaging was conducted in mice, rats, and nonhuman primates, and all species showed initial brain uptake of 0.5-0.65 standardized uptake value with fast clearance from normal tissues. [H-3]CBD-2115 could be a useful lead radioligand for further research in 4R-tauopathies, and PET radiotracer development will focus on improving brain uptake and binding affinity.

Microtubule Associated Protein Tau (MAPT) forms proteopathic aggregates in several diseases. The G273R tau mutation, located in the first repeat region, was found by exome sequencing in a patient who presented with dementia and parkinsonism. We herein return to pathological examination which demonstrated tau immunoreactivity in neurons and glia consistent of mixed progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) features. To rationalize the pathological findings, we used molecular biophysics to characterize the mutation in more detail in vitro and in Drosophila. The G273R mutation increases the aggregation propensity of 4-repeat (4R) tau and alters the tau binding affinity towards microtubules (MTs) and F-actin. Tau aggregates in PSP and CBD are predominantly 4R tau. Our data suggest that the G273R mutation induces a shift in pool of 4R tau by lower F-actin affinity, alters the conformation of MT bound 4R tau, while increasing chaperoning of 3R tau by binding stronger to F-actin. The mutation augmented fibrillation of 4R tau initiation in vitro and in glial cells in Drosophila and showed preferential seeding of 4R tau in vitro suggestively causing a late onset 4R tauopathy reminiscent of PSP and CBD.

Amyloid specific fluorescent probes are becoming an important tool for studies of disease progression and conformational polymorphisms in diseases related to protein misfolding and aggregation such as localized and systemic amyloidosis. Herein, it is demonstrated that using the amyloid specific fluorescent probes pFTAA and benzostyryl capped benzothiadiazole BTD21, structural polymorphisms of insulin amyloids are imaged in localized insulin-derived amyloid aggregates formed at subcutaneous insulin-injection sites in patients with diabetes. It is also found that pFTAA and BTD21 could discriminate structural polymorphisms of insulin amyloids, so called fibrils and filaments, formed in vitro. In addition, it is shown that insulin drug preparations used for treating diabetes formed various types of amyloid aggregates that can be assessed and quantified using pFTAA and BTD21. Interestingly, incubated pFTAA-positive insulin preparation aggregates show cytotoxicity while BTD21-positive aggregates are less toxic. From these observations, a variety of amyloid polymorphic structures with different cytotoxicities formed both in vivo and in vitro by various insulin preparations are proposed.

Control over the photophysical properties and molecular organization of pi-conjugated oligothiophenes is essential to their use in organic electronics. Herein we synthesized and characterized a variety of anionic pentameric oligothiophenes with different substitution patterns of L- or D-tyrosine at distinct positions along the thiophene backbone. Spectroscopic, microscopic, and theoretical studies of L- or D-tyrosine substituted pentameric oligothiophene conjugates revealed the formation of optically active pi-stacked self-assembled aggregates under acid conditions. The distinct photophysical characteristics, as well as the supramolecular structures of the assemblies, were highly influenced by the positioning of the L- or D-tyrosine moieties along the thiophene backbone. Overall, the obtained results clearly demonstrate how fundamental changes in the position of the enantiomeric side-chain functionalities greatly affect the optical properties as well as the architecture of the self-assembled supramolecular structures.

Over the past several years, the toxic mechanism of proliferating misfolded proteins (MPs) as initiators and drivers of neurodegeneration has gained momentum. Nonetheless, the notion of selective vulnerability of specific cell types in neurodegenerative diseases (NDs) is largely uncharted territory. NDs show vast variations in disease onset and clinical phenotype depending on culprit MP and cell type involved. Many researchers in the field aim to target MP spreading to mitigate neurodegeneration. But there are outstanding questions:

How can NDs stay dormant for decades before presenting clinical symptoms?How can certain patients carry large loads of MPs without showing symptoms? 

Amyloid fibrils and oligomers are structurally heterogeneous showing conformational and ultrastructural polymorphism. This poses a challenge both for diagnostics and for therapeutic interventions. This polymorphism likely contributes to variable disease progression because protein structure determines function. Furthermore, various cell types show different sensitivity towards distinct MPs and fibril polymorphs. Unravelling how CNS support cells, glia, versus neurons handle MPs, especially Aβ amyloid linked to Alzheimer’s disease has been hampered by the fact that transgenic (tg) mice (overproducing human Aβ) show very little neurodegeneration. The situation is dramatically different in tg-Drosophila. Here, Aβ1–42 is a potent neurotoxin and is therefore arguably a more suitable model animal for such studies [1]. We addressed the question if cell toxicity is cell type and amyloid polymorph dependent.

Emerging data reveal that amyloid fibrils possess intrinsic photonic activity, showing luminescence over a wide range of the electromagnetic spectrum from the ultraviolet to the near-infrared.

Misfolding and aggregation of the human prion protein (PrP) cause neurodegenerative transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease. Mature native PrP is composed of 209 residues and is folded into a C-terminal globular domain (residues 125-209) comprising a small two-stranded beta-sheet and three alpha-helices. The N-terminal domain (residues 23-124) is intrinsically disordered. Expression of truncated PrP (residues 90-231) is sufficient to cause prion disease and residues 90/100-231 is comprising the amyloid-like fibril core of misfolded infectious PrP. During PrP fibril formation under native conditions in vitro, the disordered N-terminal domain slows down fibril formation likely due to a mechanism of initial aggregation forming morphologically disordered aggregates. The morphological disordered aggregate is a transient phase. Nucleation of fibrils occurs from this initial aggregate. The aggregate phase is largely circumvented by seeding with preformed PrP fibrils. In vivo PrP is N-glycosylated at positions Asn181 and Asn197. Little is known about the importance of these positions and their glycans for PrP stability, aggregation and fibril formation. We have in this study taken a step towards that goal by mutating residues 181 and 197 for cysteines to study the positional impact on these processes. We have further by organic synthetic chemistry and chemical modification generated synthetic glycosylations in these positions. Our data shows that residue 181 when mutated to a cysteine is a key residue for self -chaperoning, rendering a trap in the initial aggregate preventing conformational changes towards amyloid fibril formation. Position 197 is less involved in the aggregate trapping and is more geared towards beta-sheet structure conversion within amyloid fibrils. As expected, synthetic glycosylated 197 is less affected towards fibril formation compared to glycosylated 181. Our data are rather compatible with the parallel in-register intermolecular beta-sheet model structure of the PrP90-231 fibril and sheds light on the misfolding transitions of PrP in vitro. We hypothesize that glycosylation of position 181 is a key site for prion strain differentiation in vivo.

A fluorescent bis-styryl-benzothiadiazole (BTD) with carboxylic acid functional groups (X-34/Congo red analogue) showed lower binding affinity toward A beta 1-42 and A beta 1-40 fibrils than its neutral analogue. Hence, variable patterns of neutral OH-substituted bis-styryl-BTDs were generated. All bis-styryl-BTDs showed higher binding affinity to A beta 1-42 fibrils than to A beta 1-40 fibrils. The para-OH on the phenyl rings was beneficial for binding affinity while a meta-OH decreased the affinity. Differential staining of transgenic mouse A beta amyloid plaque cores compared to peripheral coronas using neutral compared to anionic bis-styryl ligands indicate differential recognition of amyloid polymorphs. Hyperspectral imaging of transgenic mouse A beta plaque stained with uncharged para-hydroxyl substituted bis-styryl-BTD implicated differences in binding site polarity of polymorphic amyloid plaque. Most properties of the corresponding bis-styryl-BTD were retained with a rigid alkyne linker rendering a probe insensitive to cis trans isomerization. These new BTDbased ligands are promising probes for spectral imaging of different A beta fibril polymorphs.

Amyloid-β (Aβ) pathology in Alzheimer's disease (AD) is characterized by the formation of polymorphic deposits comprising diffuse and cored plaques. Because diffuse plaques are predominantly observed in cognitively unaffected, amyloid-positive (CU-AP) individuals, pathogenic conversion into cored plaques appears to be critical to AD pathogenesis. Herein, we identified the distinct Aβ species associated with amyloid polymorphism in brain tissue from individuals with sporadic AD (s-AD) and CU-AP. To this end, we interrogated Aβ polymorphism with amyloid conformation–sensitive dyes and a novel in situ MS paradigm for chemical characterization of hyperspectrally delineated plaque morphotypes. We found that maturation of diffuse into cored plaques correlated with increased Aβ1–40 deposition. Using spatial in situ delineation with imaging MS (IMS), we show that Aβ1–40 aggregates at the core structure of mature plaques, whereas Aβ1–42 localizes to diffuse amyloid aggregates. Moreover, we observed that diffuse plaques have increased pyroglutamated Aβx-42 levels in s-AD but not CU-AP, suggesting an AD pathology–related, hydrophobic functionalization of diffuse plaques facilitating Aβ1–40 deposition. Experiments in tgAPP_Swe mice verified that, similar to what has been observed in human brain pathology, diffuse deposits display higher levels of Aβ1–42 and that Aβ plaque maturation over time is associated with increases in Aβ1–40. Finally, we found that Aβ1–40 deposition is characteristic for cerebral amyloid angiopathy deposition and maturation in both humans and mice. These results indicate that N-terminal Aβx-42 pyroglutamation and Aβ1–40 deposition are critical events in priming and maturation of pathogenic Aβ from diffuse into cored plaques, underlying neurotoxic plaque development in AD.

The basis for selective vulnerability of certain cell types for misfolded proteins (MPs) in neurodegenerative diseases is largely unknown. This knowledge is crucial for understanding disease progression in relation to MPs spreading in the CNS. We assessed this issue in Drosophila by cell-specific expression of human A beta 1-42 associated with Alzheimers disease. Expression of A beta 1-42 in various neurons resulted in concentration-dependent severe neurodegenerative phenotypes, and intraneuronal ringtangle-like aggregates with immature fibril properties when analyzed by aggregate-specific ligands. Unexpectedly, expression of A beta 1-42 from a pan-glial driver produced a mild phenotype despite massive brain load of A beta 1-42 aggregates, even higher than in the strongest neuronal driver. Glial cells formed more mature fibrous aggregates, morphologically distinct from aggregates found in neurons, and was mainly extracellular. Our findings implicate that A beta 1-42 cytotoxicity is both cell and aggregate morphotype dependent.

Aggregation is a sequence-specific process, nucleated by short aggregation-prone regions (APRs) that can be exploited to induce aggregation of proteins containing the same APR. Here, we find that most APRs are unique within a proteome, but that a small minority of APRs occur in many proteins. When aggregation is nucleated in bacteria by such frequently occurring APRs, it leads to massive and lethal inclusion body formation containing a large number of proteins. Buildup of bacterial resistance against these peptides is slow. In addition, the approach is effective against drug-resistant clinical isolates of Escherichia coli and Acinetobacter baumannii, reducing bacterial load in a murine bladder infection model. Our results indicate that redundant APRs are weak points of bacterial protein homeostasis and that targeting these may be an attractive antibacterial strategy.

The accumulation of misfolded proteins (MPs), both unique and common, for different diseases is central for many chronic degenerative diseases. In certain patients, MP accumulation is systemic (e.g. TTR amyloid), and in others, this is localized to a specific cell type (e.g. Alzheimers disease). In neurodegenerative diseases, NDs, it is noticeable that the accumulation of MP progressively spreads throughout the nervous system. Our main hypothesis of this article is that MPs are not only markers but also active carriers of pathogenicity. Here, we discuss studies from comprehensive molecular approaches aimed at understanding MP conformational variations (polymorphism) and their bearing on spreading of MPs, MP toxicity, as well as MP targeting in imaging and therapy. Neurodegenerative disease (ND) represents a major and growing societal challenge, with millions of people worldwide suffering from Alzheimers or Parkinsons diseases alone. For all NDs, current treatment is palliative without addressing the primary cause and is not curative. Over recent years, particularly the shape-shifting properties of misfolded proteins and their spreading pathways have been intensively researched. The difficulty in addressing ND has prompted most major pharma companies to severely downsize their nervous system disorder research. Increased academic research is pivotal for filling this void and to translate basic research into tools for medical professionals. Recent discoveries of targeting drug design against MPs and improved model systems to study structure, pathology spreading and toxicity strongly encourage future studies along these lines to provide an opportunity for selective imaging, prognostic diagnosis and therapy.

Luminescent conjugated polythiophenes bind to amyloid proteins with high affinity. Their fluorescence properties, which are modulated by the detailed conformation in the bound state, are highly sensitive to structural features of the amyloid. Polythiophenes therefore represent diagnostic markers for the detection and differentiation of pathological amyloid aggregates. 560 We clarify the binding site and mode of two different polythiophenes to fibrils of the prion domain of the HET-s protein by solid-state NMR and correlate these findings with their fluorescence properties. We demonstrate how amyloid dyes recognize distinct binding sites with specific topological features. Regularly spaced surface charge patterns and well-accessible grooves on the fibril surface define the pharmacophore of the amyloid, which in turn determines the binding mode and fluorescence wavelength of the polythiophene.

We revisited the Congo red analogue 2,5-bis(4-hydroxy-3-carboxy-styryl)benzene (X-34) to develop this highly fluorescent amyloid dye for imaging Alzheimers disease (AD) pathology comprising A beta and Tau fibrils. A selection of ligands with distinct optical properties were synthesized by replacing the central benzene unit of X-34, with other heterocyclic moieties. Full photophysical characterization was performed, including recording absorbance and fluorescence spectra, Stokes shift, quantum yield and fluorescence lifetimes. All ligands displayed high affinity towards recombinant amyloid fibrils of A beta 1-42 (13-300nmK(d)) and Tau (16-200nmK(d)) as well as selectivity towards the corresponding disease-associated protein aggregates in AD tissue. We observed that these ligands efficiently displaced X-34, but not Pittsburgh compound B (PiB) from recombinant A beta 1-42 amyloid fibrils, arguing for retained targeting of the Congo red type binding site. We foresee that the X-34 scaffold offers the possibility to develop novel high-affinity ligands for A pathology found in human AD brain in a different mode compared with PiB, potentially recognizing different polymorphs of A fibrils.

Prions typically spread into the central nervous system (CNS), likely via peripheral nerves. Yet prion conformers differ in their capacity to penetrate the CNS; certain fibrillar prions replicate persistently in lymphoid tissues with no CNS entry, leading to chronic silent carriers. Subclinical carriers of variant Creutzfeldt-Jakob (vCJD) prions in the United Kingdom have been estimated at 1:2000, and vCJD prions have been transmitted through blood transfusion, however, the circulating prion conformers that neuroinvade remain unclear. Here we investigate how prion conformation impacts brain entry of transfused prions by challenging mice intravenously to subfibrillar and fibrillar strains. We show that most strains infiltrated the brain and caused terminal disease, however, the fibrillar prions showed reduced CNS entry in a strain-dependent manner. Strikingly, the highly fibrillar mCWD prion strain replicated in the spleen and emerged in the brain as a novel strain, indicating that a new neuroinvasive prion had been generated from a previously non-neuroinvasive strain. The new strain showed altered plaque morphology, brain regions targeted and biochemical properties and these properties were maintained upon intracerebral passage. Intracerebral passage of prion-infected spleen re-created the new strain. Splenic prions resembled the new strain biochemically and intracerebral passage of prion-infected spleen re-created the new strain, collectively suggesting splenic prion replication as a potential source. Taken together, these results indicate that intravenous exposure to prion-contaminated blood or blood products may generate novel neuroinvasive prion conformers and disease phenotypes, potentially arising from prion replication in non-neural tissues or from conformer selection.

Two analogues to the fluorescent amyloid probe 2,5-bis(4'-hydroxy-3'-carboxy-styryl)benzene (X-34) were synthesized based on the trans-stilbene pyrene scaffold (Py1SA and Py2SA). The compounds show strikingly different emission spectra when bound to preformed Aβ1-42 fibrils. This remarkable emission difference is retained when bound to amyloid fibrils of four distinct proteins, suggesting a common binding configuration for each molecule. Density functional theory calculations show that Py1SA is twisted, while Py2SA is more planar. Still, an analysis of the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) of the two compounds indicates that the degree of electronic coupling between the pyrene and salicylic acid (SA) moieties is larger in Py1SA than in Py2SA. Excited state intramolecular proton transfer (ESIPT) coupled-charge transfer (ICT) was observed for the anionic form in polar solvents. We conclude that ICT properties of trans-stilbene derivatives can be utilized for amyloid probe design with large changes in emission spectra and decay times from analogous chemical structures depending on the detailed physical nature of the binding site.less thanbr /greater than (© 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim.)

Luminescent-conjugated oligo- and polythiophenes (LCOs and LCPs) are valuable tools for optical imaging of a plethora of protein aggregates associated with amyloidoses. Here, we outline updated protocols for the application of the anionic pentameric LCO, p-FTAA, for staining and hyperspectral imaging of protein aggregates in a variety of settings such as in vitro formed amyloid fibrils, ex vivo tissue sections, and whole brain Drosophila.

Amyloid plaque formation constitutes one of the main pathological hallmarks of Alzheimers disease (AD) and is suggested to be a critical factor driving disease pathogenesis. Interestingly, in patients that display amyloid pathology but remain cognitively normal, A beta deposits are predominantly of diffuse morphology suggesting that cored plaque formation is primarily associated with cognitive deterioration and AD pathogenesis. Little is known about the molecular mechanism responsible for conversion of monomeric A beta into neurotoxic aggregates and the predominantly cored deposits observed in AD. The structural diversity among A beta plaques, including cored/compact- and diffuse, may be linked to their distinct A beta profile and other chemical species including neuronal lipids. We developed a novel, chemical imaging paradigm combining matrix assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) and fluorescent amyloid staining. This multimodal imaging approach was used to probe the lipid chemistry associated with structural plaque heterogeneity in transgenic AD mice (tgAPP(Swe)) and was correlated to A beta profiles determined by subsequent laser microdissection and immunoprecipitation-mass spectrometry. Multivariate image analysis revealed an inverse localization of ceramides and their matching metabolites to diffuse and cored structures within single plaques, respectively. Moreover, phosphatidylinositols implicated in AD pathogenesis, were found to localize to the diffuse A beta structures and correlate with A beta 1-42. Further, lysophospholipids implicated in neuroinflammation were increased in all A beta deposits. The results support previous clinical findings on the importance of lipid disturbances in AD pathophysiology and associated sphingolipid processing. These data highlight the potential of multimodal imaging as a powerful technology to probe neuropathological mechanisms.

The molecular architecture of amyloids formed in vivo can be interrogated using luminescent conjugated oligothiophenes (LCOs), a unique class of amyloid dyes. When bound to amyloid, LCOs yield fluorescence emission spectra that reflect the 3D structure of the protein aggregates. Given that synthetic amyloid-beta peptide (A beta) has been shown to adopt distinct structural conformations with different biological activities, we asked whether A beta can assume structurally and functionally distinct conformations within the brain. To this end, we analyzed the LCO-stained cores of beta-amyloid plaques in postmortem tissue sections from frontal, temporal, and occipital neocortices in 40 cases of familial Alzheimers disease (AD) or sporadic (idiopathic) AD (sAD). The spectral attributes of LCO-bound plaques varied markedly in the brain, but the mean spectral properties of the amyloid cores were generally similar in all three cortical regions of individual patients. Remarkably, the LCO amyloid spectra differed significantly among some of the familial and sAD subtypes, and between typical patients with sAD and those with posterior cortical atrophy AD. Neither the amount of A beta nor its protease resistance correlated with LCO spectral properties. LCO spectral amyloid phenotypes could be partially conveyed to A beta plaques induced by experimental transmission in a mouse model. These findings indicate that polymorphic A beta-amyloid deposits within the brain cluster as clouds of conformational variants in different AD cases. Heterogeneity in the molecular architecture of pathogenic A beta among individuals and in etiologically distinct subtypes of AD justifies further studies to assess putative links between A beta conformation and clinical phenotype.

Transthyretin-derived (ATTR) amyloidosis is a frequent finding in carpal tunnel syndrome. We tested the following hypotheses: the novel fluorescent amyloid ligand heptameric formic thiophene acetic acid (h-FTAA) has a superior sensitivity for the detection of amyloid compared with Congo red-staining; Amyloid load correlates with patient gender and/or patient age. We retrieved 208 resection specimens obtained from 184 patients with ATTR amyloid in the carpal tunnel. Serial sections were stained with Congo red, h-FTAA and an antibody directed against transthyretin (TTR). Stained sections were digitalized and forwarded to computational analyses. The amount of amyloid was correlated with patient demographics. Amyloid stained intensely with h-FTAA and an anti-TTR-antibody. Congo red-staining combined with fluorescence microscopy was significantly less sensitive than h-FTAA-fluorescence and TTR-immunostaining: the highest percentage area was found in TTR-immunostained sections, followed by h-FTAA and Congo red. The Pearson correlation coefficient was .8 (Congo red vs. h-FTAA) and .9 (TTR vs. h-FTAA). Amyloid load correlated with patient gender, anatomical site and patient age. h-FTAA is a highly sensitive method to detect even small amounts of ATTR amyloid in the carpal tunnel. The staining protocol is easy and h-FTAA may be a much more sensitive procedure to detect amyloid at an earlier stage.

Proteins that deposit as amyloid in tissues throughout the body can be the cause or consequence of a large number of diseases. Among these we find neurodegenerative diseases such as Alzheimers and Parkinsons disease afflicting primarily the central nervous system, and systemic amyloidosis where serum amyloid A, transthyretin and IgG light chains deposit as amyloid in liver, carpal tunnel, spleen, kidney, heart, and other peripheral tissues. Amyloid has been known and studied for more than a century, often using amyloid specific dyes such as Congo red and Thioflavin T (ThT) or Thioflavin (ThS). In this paper, we present heptamer-formyl thiophene acetic acid (hFTAA) as an example of recently developed complements to these dyes called luminescent conjugated oligothiophenes (LCOs). hFTAA is easy to use and is compatible with co-staining in immunofluorescence or with other cellular markers. Extensive research has proven that hFTAA detects a wider range of disease associated protein aggregates than conventional amyloid dyes. In addition, hFTAA can also be applied for optical assignment of distinct aggregated morphotypes to allow studies of amyloid fibril polymorphism. While the imaging methodology applied is optional, we here demonstrate hyperspectral imaging (HIS), laser scanning confocal microscopy and fluorescence lifetime imaging (FLIM). These examples show some of the imaging techniques where LCOs can be used as tools to gain more detailed knowledge of the formation and structural properties of amyloids. An important limitation to the technique is, as for all conventional optical microscopy techniques, the requirement for microscopic size of aggregates to allow detection. Furthermore, the aggregate should comprise a repetitive beta-sheet structure to allow for hFTAA binding. Excessive fixation and/or epitope exposure that modify the aggregate structure or conformation can render poor hFTAA binding and hence pose limitations to accurate imaging.

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It was previously reported that two naphthyl-based trans-stilbene probes, (E)-4-(2-(naphthalen-1-yl)vinyl)benzene-1,2-diol (1) and (E)-4-(2-(naphthalen-2-yl)vinyl)benzene-1,2-diol (3), can bind to both native transthyretin (TTR) and misfolded protofibrillar TTR at physiological concentrations, displaying distinct emission maxima bound to the different conformational states (>100 nm difference). To further explore this amyloid probe scaffold to obtain extended fluorescence lifetimes, two new analogues with expanded aromatic ring systems (anthracene and pyrene), (E)-4-(2-(anthracen-2-yl)vinyl)benzene-1,2-diol (4) and (E)-4-(2-(pyren-2-yl)vinyl)benzene-1,2-diol (5), were synthesized employing the palladium-catalyzed Mizoroki–Heck reaction. (E)-4-Styrylbenzene-1,2-diol (2), 3, 4, and 5 were investigated with respect to their photophysical properties in methanol and when bound to insulin, lysozyme, and Aβ1-42 fibrils, including time-resolved fluorescence measurements. In conclusion, 4 and 5 can bind to both native and fibrillar TTR, becoming highly fluorescent. Compounds 2–5 bind specifically to insulin, lysozyme, and Aβ1-42 fibrils with an apparent fluorescence intensity increase and moderate binding affinities. The average fluorescence lifetimes of the probes bound to Aβ1-42 fibrils are 1.3 ns (2), 1.5 ns (3), 5.7 ns (4), and 29.8 ns (5). In summary, the variable aromatic moieties of the para-positioned trans-stilbenoid vinyl-benzene-1,2-diol with benzene, naphthalene, anthracene, and pyrene showed that the extended conjugated systems retained the amyloid targeting properties of the probes. Furthermore, both the anthracene and pyrene moieties extensively enhanced the fluorescence intensity and prolonged lifetimes. These attractive probe properties should improve amyloid detection and characterization by fluorescence-based techniques.

Three oligothiophenes were evaluated as PET tracers for the study of local and systemic amyloidosis ex vivo using tissue from patients with amyloid deposits and in vivo using healthy animals and PET-CT. The ex vivo binding studies revealed that all three labeled compounds bound specifically to human amyloid deposits. Specific binding was found in the heart, kidney, liver and spleen. To verify the specificity of the oligothiophenes towards amyloid deposits, tissue sections with amyloid pathology were stained using the fluorescence exhibited by the compounds and evaluated with multiphoton microscopy. Furthermore, in vivo rat and monkey PET-CT studies showed very low uptake in the brain, pancreas and heart of the healthy animals indicating low non-specific binding to healthy tissue. The biological evaluations indicated that this is a promising group of compounds for the visualization of systemic and localized amyloidosis.

Most human proteins possess amyloidogenic segments, but only about 30 are associated with amyloid-associated pathologies, and it remains unclear what determines amyloid toxicity. We designed vascin, a synthetic amyloid peptide, based on an amyloidogenic fragment of vascular endothelial growth factor receptor 2 (VEGFR2), a protein that is not associated to amyloidosis. Vascin recapitulates key biophysical and biochemical characteristics of natural amyloids, penetrates cells, and seeds the aggregation of VEGFR2 through direct interaction. We found that amyloid toxicity is observed only in cells that both express VEGFR2 and are dependent on VEGFR2 activity for survival. Thus, amyloid toxicity here appears to be both protein-specific and conditional-determined by VEGFR2 loss of function in a biological context in which target protein function is essential.

Here, we study and compare the mechanisms of action of the GroEL/GroES and the TRiC chaperonin systems on MreB client protein variants extracted from E. coli. MreB is a homologue to actin in prokaryotes. Single-molecule fluorescence correlation spectroscopy (FCS) and time-resolved fluorescence polarization anisotropy report the binding interaction of folding MreB with GroEL, GroES and TRiC. Fluorescence resonance energy transfer (FRET) measurements on MreB variants quantified molecular distance changes occurring during conformational rearrangements within folding MreB bound to chaperonins. We observed that the MreB structure is rearranged by a binding-induced expansion mechanism in TRiC, GroEL and GroES. These results are quantitatively comparable to the structural rearrangements found during the interaction of beta-actin with GroEL and TRiC, indicating that the mechanism of chaperonins is conserved during evolution. The chaperonin-bound MreB is also significantly compacted after addition of AMP-PNP for both the GroEL/ES and TRiC systems. Most importantly, our results showed that GroES may act as an unfoldase by inducing a dramatic initial expansion of MreB (even more than for GroEL) implicating a role for MreB folding, allowing us to suggest a delivery mechanism for GroES to GroEL in prokaryotes.

Rapid and accurate detection of amyloid deposits in routine surgical pathology settings are of great importance. The use of fluorescence microscopy in combination with appropriate amyloid specific dyes is very promising in this regard. Here we report that a luminescent conjugated oligothiophene, h-FTAA, rapidly and with high sensitivity and selectivity detects amyloid deposits in verified clinical samples from systemic amyloidosis patients with AA, AL and ATTR types; as well as in tissues laden with localized amyloidosis of AANF, AIAPP and ASem1 type. The probe h-FTAA emitted yellow red fluorescence on binding to amyloid deposits, whereas no apparent staining was observed in surrounding tissue. The only functional structure stained with h-FTAA showing the amyloidotypic fluorescence spectrum was Paneth cell granules in intestine. Screening of 114 amyloid containing tissues derived from 107 verified (Congo red birefringence and/or immunohistochemistry) amyloidosis patients revealed complete correlation between h-FTAA and Congo red fluorescence (107/107, 100% sensitivity). The majority of Congo red negative control cases (27 of 32, 85% specificity) were negative with h-FTAA. Small Congo red negative aggregates in kidney, liver, pancreas and duodenum were found by h-FTAA fluorescence in five control patients aged 72-83 years suffering from diverse diseases. The clinical significance of these false-positive lesions is currently not known. Because h-FTAA fluorescence is one magnitude brighter than Congo red and as the staining is performed four magnitudes lower than the concentration of dye, we believe that these inclusions are beyond detection by Congo red. We conclude that h-FTAA is a fluorescent hypersensitive, rapid and powerful tool for identifying amyloid deposits in tissue sections. Use of h-FTAA can be exploited as a rapid complementary technique for accurate detection of amyloid in routine surgical pathology settings. Our results also implicate the potential of the technique for detection of prodromal amyloidosis as well as for discovery of new amyloid-like protein aggregates in humans.

Amyloid plaques composed of fibrillar Amyloid-beta (A beta) are hallmarks of Alzheimers disease. However, A beta fibrils are morphologically heterogeneous. Conformation sensitive luminescent conjugated oligothiophenes (LCOs) are versatile tools for monitoring such fibril polymorphism in vivo and in vitro. Biophysical methods applied on in vitro generated A beta fibrils, stained with LCOs with different binding and fluorescence properties, can be used to characterize the A beta fibrillation in depth, far beyond that possible for in vivo generated amyloid plaques. In this study, in vitro fibrillation of the A beta 1-40 peptide was monitored by time-lapse transmission electron microscopy, LCO fluorescence, and atomic force microscopy. Differences in the LCO binding in combination with nanoscale imaging revealed that spectral variation correlated with fibrils transforming from solitary filaments (empty set similar to 2.5 nm) into higher order bundled structures (empty set similar to 5 nm). These detailed in vitro experiments can be used to derive data that reflects the heterogeneity of in vivo generated A beta plaques observed by LCO fluorescence. Our work provides new structural basis for targeted drug design and molecular probe development for amyloid imaging.

Accumulation of misfolded transthyretin (TTR) as amyloid fibrils causes various human disorders. Native transthyretin is a neurotrophic protein and is a putative extracellular molecular chaperone. Several fluorophores have been shown in vitro to bind selectively to native TTR. Other compounds, such as thioflavin T, bind TTR amyloid fibrils. The probe 1-anilinonaphthalene-8-sulfonate (ANS) binds to both native and fibrillar TTR, becoming highly fluorescent, but with indistinguishable emission spectra for native and fibrillar TTR. Herein we report our efforts to develop a fluorescent small molecule capable of binding both native and misfolded protofibrillar TTR, providing distinguishable emission spectra. We used microwave synthesis for efficient production of a small library of trans-stilbenes and fluorescence spectral screening of their binding properties. We synthesized and tested 22 trans-stilbenes displaying a variety of functional groups. We successfully developed two naphthyl-based trans-stilbenes probes that detect both TTR states at physiological concentrations. The compounds bound with nanomolar to micromolar affinities and displayed distinct emission maxima upon binding native or misfolded protofibrillar TTR (>100 nm difference). The probes were mainly responsive to environment polarity providing evidence for the divergent hydrophobic structure of the binding sites of these protein conformational states. Furthermore, we were able to successfully use one of these probes to quantify the relative amounts of native and protofibrillar TTR in a dynamic equilibrium. In conclusion, we identified two trans-stilbene-based fluorescent probes, (E)-4-(2-(naphthalen-1-yl)vinyl)benzene-1,2-diol (11) and (E)-4-(2-(naphthalen-2-yl)vinyl)benzene-1,2-diol (14), that bind native and protofibrillar TTR, providing a wide difference in emission maxima allowing conformational discrimination by fluorescence spectroscopy. We expect these novel molecules to serve as important chemical biology research tools in studies of TTR folding and misfolding.

Taking advantage of the xenobiotic nature of bacterial infections, we tested whether the cytotoxicity of protein aggregation can be targeted to bacterial pathogens without affecting their mammalian hosts. In particular, we examined if peptides encoding aggregation-prone sequence segments of bacterial proteins can display antimicrobial activity by initiating toxic protein aggregation in bacteria, but not in mammalian cells. Unbiased in vitro screening of aggregating peptide sequences from bacterial genomes lead to the identification of several peptides that are strongly bactericidal against methicillin-resistant Staphylococcus aureus. Upon parenteral administration in vivo, the peptides cured mice from bacterial sepsis without apparent toxic side effects as judged from histological and hematological evaluation. We found that the peptides enter and accumulate in the bacterial cytosol where they cause aggregation of bacterial polypeptides. Although the precise chain of events that leads to cell death remains to be elucidated, the ability to tap into aggregation-prone sequences of bacterial proteomes to elicit antimicrobial activity represents a rich and unexplored chemical space to be mined in search of novel therapeutic strategies to fight infectious diseases.

We herein report on an iontronic device to drive and control A1-40 and A1-42 fibril formation. This system allows kinetic control of A aggregation by regulation of H+ flows. The formed aggregates show both nanometer-sized fibril structure and microscopic growth, thus mimicking senile plaques, at the H+-outlet. Mechanistically we observed initial accumulation of A1-40 likely driven by electrophoretic migration which preceded nucleation of amyloid structures in the accumulated peptide cluster.

Despite numerous studies, a detailed description of the transthyretin (TTR) self-assembly mechanism and fibril structure in TTR amyloidoses remains unresolved. Here, using a combination of primarily small -angle X-ray scattering (SAXS) and hydrogen exchange mass spectrometry (HXMS) analysis, we describe an unexpectedly dynamic TTR protofibril structure which exchanges protomers with highly unfolded monomers in solution. The protofibrils only grow to an approximate final size of 2,900 kDa and a length of 70 nm and a comparative HXMS analysis of native and aggregated samples revealed a much higher average solvent exposure of TTR upon fibrillation. With SAXS, we reveal the continuous presence of a considerably unfolded TTR monomer throughout the fibrillation process, and show that a considerable fraction of the fibrillating protein remains in solution even at a late maturation state. Together, these data reveal that the fibrillar state interchanges with the solution state. Accordingly, we suggest that TTR fibrillation proceeds via addition of considerably unfolded monomers, and the continuous presence of amyloidogenic structures near the protofibril surface offers a plausible explanation for secondary nucleation. We argue that the presence of such dynamic structural equilibria must impact future therapeutic development strategies.

Prion diseases are lethal, infectious diseases associated with prion protein (PrP) misfolding. A large number of mammals are susceptible to both sporadic and acquired prion diseases. Although PrP is highly conserved and ubiquitously expressed in all mammals, not all species exhibit prion disease. By employing full length recombinant PrP from five known prion susceptible species (human, cattle, cat, mouse and hamster) and two species considered to be prion resistant (pig and dog) the amyloidogenicity of these PrPs has been delineated. All the mammalian PrPs, even from resistant species, were swiftly converted from the native state to amyloid-like structure when subjected to a native condition conversion assay. The PrPs displayed amyloidotypic tinctorial and ultrastructural hallmarks. Self-seeded conversion of the PrPs displayed significantly decreased lag phases demonstrating that nucleation dependent polymerization is a dominating mechanism in the fibrillation process. Fibrils from A beta 1-40, A beta 1-42, Lysozyme, Insulin and Transthyretin did not accelerate conversion of HuPrP whereas fibrils from HuPrP90-231 and HuPrP121-231 as well as full length PrPs of all PrPs efficiently seeded conversion showing specificity of the assay requiring the C-terminal PrP sequence. Our findings have implications for PrP misfolding and could have ramifications in the context of prion resistant species and silent carriers.

Transthyretin (TTR) is a homotetrameric protein that must misfold in order to form amyloid fibrils. Misfolding includes rate limiting tetramer dissociation, followed by fast tertiary structural changes of the monomer that enable aggregation. Hereditary ATTR amyloidosis is an autosomal dominant genetic disorder with systemic deposition of amyloid fibrils induced by TTR gene mutation. We identified a rare Y114H (p.Y134H) TTR variant in a Japanese patient presenting with late-onset, very mild clinical course. The patient had an extremely low serum variant TTR concentration (18% of total TTR), whereas the composition of variant TTR was 55% in amyloid fibrils in tenosynovial tissues obtained at carpal tunnel release surgery. The amyloid fibril deposits in the ATTR Y114H patient had an altered structure compared with that in wild-type ATTR patients, as determined by luminescent conjugated poly/oligo-thiophene fluorescence spectroscopy. Biophysical studies using recombinant protein showed that Y114H TTR was markedly destabilized both thermodynamically and kinetically and was highly amyloidogenic in vitro. These data suggest that extremely low serum variant Y114H TTR concentration, probably due to endoplasmic reticulum-associated degradation of unstable variant TTR protein, protected this patient from severe amyloidosis, as self-assembly of the amyloidogenic intermediate is a concentration-dependent process.

Mammalian prions are composed of misfolded aggregated prion protein (PrP) with amyloid-like features. Prions are zoonotic disease agents that infect a wide variety of mammalian species including humans. Mammals and by-products thereof which are frequently encountered in daily life are most important for human health. It is established that bovine prions (BSE) can infect humans while there is no such evidence for any other prion susceptible species in the human food chain (sheep, goat, elk, deer) and largely prion resistant species (pig) or susceptible and resistant pets (cat and dogs, respectively). PrPs from these species have been characterized using biochemistry, biophysics and neurobiology. Recently we studied PrPs from several mammals in vitro and found evidence for generic amyloidogenicity as well as cross-seeding fibril formation activity of all PrPs on the human PrP sequence regardless if the original species was resistant or susceptible to prion disease. Porcine PrP amyloidogenicity was among the studied. Experimentally inoculated pigs as well as transgenic mouse lines overexpressing porcine PrP have, in the past, been used to investigate the possibility of prion transmission in pigs. The pig is a species with extraordinarily wide use within human daily life with over a billion pigs harvested for human consumption each year. Here we discuss the possibility that the largely prion disease resistant pig can be a clinically silent carrier of replicating prions.

Systemic amyloidosis (SA) is often diagnosed late. Combining clinical and biochemical biomarkers is necessary for raising suspicion of disease. Fine needle aspiration (FNA) of subcutaneous fat enables SA detection by Congo red staining. The luminescent conjugated probe heptameric formic thiophene acetic acid (h-FTAA) is a sensitive alternative to Congo red-staining of tissue samples. Our objective was to compare h-FTAA fluorescence with the Congo red stain for amyloid detection in FNA-obtained fat tissue. Herein, we studied samples from 57 patients with established SA (19 with AA, 20 with AL, and 18 with ATTR) and 17 age-matched controls (34–75 years). Positivity for h-FTAA was graded according to a Congo red-based grading scale ranging from 0 to 4+. Amyloid grading by both methods correlated strongly (r = 0.87). Here h-FTAA was positive in 53 of 54 Congo red-positive cases (sensitivity 98%) and h-FTAA was negative in 7 of 17 Congo red-negative controls (specificity 41%), but was also positive for 3 Congo red-negative SA cases. We conclude that h-FTAA fluorescence is more sensitive than Congo red staining in this small exploratory study of fat tissue samples, implicating potential sensitivity for prodromal amyloidosis, but is less specific for clinical amyloidosis defined by Congo red positivity. Given its simplicity h-FTAA staining may therefore be the most appropriate method for rapid screening of fat tissue samples but should presently treat grade 1+ as only suggestive, whereas 2+ or higher as positive for amyloidosis. Parallel assessment of h-FTAA and Congo red staining appears highly promising for clinical applications.

Prions cause transmissible spongiform encephalopathies for which no treatment exists. Prions consist of PrPSc, a misfolded and aggregated form of the cellular prion protein (PrPC). We explore the antiprion properties of luminescent conjugated polythiophenes (LCPs) that bind and stabilize ordered protein aggregates. By administering a library of structurally diverse LCPs to the brains of prion-infected mice via osmotic minipumps, we found that antiprion activity required a minimum of five thiophene rings bearing regularly spaced carboxyl side groups. Solid-state nuclear magnetic resonance analyses and molecular dynamics simulations revealed that anionic side chains interacted with complementary, regularly spaced cationic amyloid residues of model prions. These findings allowed us to extract structural rules governing the interaction between LCPs and protein aggregates, which we then used to design a new set of LCPs with optimized binding. The new set of LCPs showed robust prophylactic and therapeutic potency in prion-infected mice, with the lead compound extending survival by greater than80% and showing activity against both mouse and hamster prions as well as efficacy upon intraperitoneal administration into mice. These results demonstrate the feasibility of targeted chemical design of compounds that may be useful for treating diseases of aberrant protein aggregation such as prion disease.