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Sensitivity to Lysosome-Dependent Cell Death is Directly Regulated by Lysosomal Cholesterol Content
Linköping University, Department of Clinical and Experimental Medicine, Experimental Pathology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medical and Health Sciences, Anesthesiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Intensive Care.
Biochemical Institute, Christian-Albrechts-University Kiel, Kiel, Germany.
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2012 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 11Article in journal (Refereed) Published
Abstract [en]

Alterations in lipid homeostasis are implicated in several neurodegenerative diseases, although the mechanisms responsible are poorly understood. We evaluated the impact of cholesterol accumulation, induced by U18666A, quinacrine or mutations in the cholesterol transporting Niemann-Pick disease type C1 (NPC1) protein, on lysosomal stability and sensitivity to lysosome-mediated cell death. We found that neurons with lysosomal cholesterol accumulation were protected from oxidative stress-induced apoptosis. In addition, human fibroblasts with cholesterol-loaded lysosomes showed higher lysosomal membrane stability than controls. Previous studies have shown that cholesterol accumulation is accompanied by the storage of lipids such as sphingomyelin, glycosphingolipids and sphingosine and an up regulation of lysosomal associated membrane protein-2 (LAMP-2), which may also influence lysosomal stability. However, in this study the use of myriocin and LAMP deficient fibroblasts excluded these factors as responsible for the rescuing effect and instead suggested that primarily lysosomal cholesterol content determined the cellular sensitivity to toxic insults. Further strengthening this concept, depletion of cholesterol using methyl-β-cyclodextrin or 25-hydroxycholesterol decreased the stability of lysosomes and cells became more prone to undergo apoptosis. In conclusion, cholesterol content regulated lysosomal membrane permeabilization and thereby influenced cell death sensitivity. Our data suggests that lysosomal cholesterol modulation might be used as a therapeutic strategy for conditions associated with accelerated or repressed apoptosis.

Place, publisher, year, edition, pages
Public Library of Science , 2012. Vol. 7, no 11
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-85004DOI: 10.1371/journal.pone.0050262ISI: 000311885300096PubMedID: 23166840OAI: oai:DiVA.org:liu-85004DiVA: diva2:563512
Note

Funding Agencies|Swedish Research Council|2010-3463|Deutsche Forschungsgemeinschaft||foundation of Olle Engqvist||foundation of Ake Wiberg||

Available from: 2012-10-30 Created: 2012-10-30 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Lysosomal Membrande Stability and Cathepsins in Cell Death
Open this publication in new window or tab >>Lysosomal Membrande Stability and Cathepsins in Cell Death
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lysosomes are acidic organelles that are critically involved in a number of physiological processes, including macromolecule degradation, endocytosis, autophagy, exocytosis and cholesterol homeostasis. Several pathological conditions, such as cancer, neurodegenerative disorders and lysosomal storage diseases, involve lysosomal disturbances, indicating the importance of the organelle for correct cellular function. The aim of this thesis was to investigate the role of lysosomes in cell death signaling.

Previous studies have shown that permeabilization of the lysosomal membrane and release of hydrolytic enzymes such as cathepsin D to the cytosol occurs during apoptosis. We identified Bid and 14-3-3 proteins as cytosolic targets of cathepsin D in human fibroblasts. Truncated Bid, generated by cathepsin D proteolytic cleavage, stimulates Bax-mediated release of pro-apoptotic factors from the mitochondria, thereby engaging the intrinsic pathway to apoptosis.

Since the presence of cathepsins in the cytosol is sufficient to induce apoptosis, the permeability of the lysosomal membrane influences the fate of the cell. In this thesis, we demonstrated that the stability of the lysosomal membrane can be manipulated by altering the lysosomal cholesterol content. Cells with high lysosomal cholesterol content were less prone to undergo apoptosis when challenged with stimuli known to induce lysosome-mediated cell death. In addition, cholesterol accumulation was associated with increased expression of lysosome-associated membrane proteins and storage of other lipids; however, these factors did not contribute to lysosomal stabilization.

Lysosomal membrane permeabilization and cathepsins contribute to ultraviolet (UV) irradiation-induced apoptosis. We demonstrate plasma membrane damage induced by UVA irradiation to be rapidly repaired by lysosomal exocytosis in human keratinocytes. Despite efficient plasma membrane resealing, the cells underwent apoptosis, which was dependent on early activation of caspase-8. The activation of caspase-8 was lysosome-dependent and occurred in vesicles positive for lysosomal markers.

This thesis demonstrates the importance of lysosomal stability for apoptosis regulation and that this stability can be influenced by drug intervention. Modulation of the lysosomal membrane permeability may have potential for use as a therapeutic strategy in conditions associated with accelerated or repressed apoptosis.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 160 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1325
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-85008 (URN)978-91-7519-803-3 (ISBN)
Public defence
2012-11-28, Eken, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 09:00 (Swedish)
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Available from: 2012-10-30 Created: 2012-10-30 Last updated: 2017-08-30Bibliographically approved

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Appelqvist, HannaSandin, LinneaBjörnström, KarinÖllinger, KarinKågedal, Katarina

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Experimental PathologyFaculty of Health SciencesCell BiologyAnesthesiologyDepartment of Intensive CareDepartment of Clinical Pathology and Clinical GeneticsPathology
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