liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Melanophore signaling: regulation and application
Linköping University, Department of Medicine and Care, Pharmacology. Linköping University, Faculty of Health Sciences.
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Melanophores are pigment-containing cells responsible for quick physiological color changes in lower vertebrates due to redistribution of melanosomes, pigment granules. We have studied melanophores from African clawed frog, Xenopus laevis. Classically, melanosomes can be stimulated to aggregate in the cell center by the hormone melatonin via a process involving activation of the inhibitory Gi/o protein and inhibition of adenylate cyclase/cAMP/protein kinase A pathway. In addition, tyrosine phosphorylations have been shown to be crucial for aggregation. In this thesis, we demonstrate that mitogen-activated protein kinase (MAPK) are activated and phosphoinositol 3-kinase (PI3-K) are involved in melatonininduced aggregation. Inhibition of MAPK kinase or PI3-K inhibits MAPK activation, tyrosine phosphorylation of a 280-kDa protein and aggregation. Further, PI3-K inhibition is less dramatic in fish Labrus melanophores. Together with findings that phosphodiesterase (PDE) 4 and/or PDE2 are involved in keeping the aggregated state in Xenopus, we suggest that active PI3-K via MAPK stimulates PDE, thus lowering cAMP. We also use latrunculin A to induce aggregation via disruption of actin filaments. Kinetic studies indicate that melatonin and latrunculin share final downstream target, possibly inactivate myosin-V leading to melanosome aggregation. As biosensor application, a new computer screen assisted technique suitable for bioassays is demonstrated using melanophores to monitor kinetic responses of melanosome movement and blood plasma sample detection of the asthma drug and ß2 adrenergic agonist formoterol. We also used melanophores to examine the efficacy of enantiomers of formoterol. We confirm that (R;R)-formoterol is more potent than (S;S)-formoterol, in guinea pig tracheal ring preparations, cultured melanophores, and radioligand binding on COS-7 cells, but demonstrate and calculate that (S;S)-formoterol has more efficacy than previously described. Characterization of melanophores are important for biosensor applications, i e to understand mechanisms of drugs, and will probably also increase the knowledge of cell signaling in other cell systems.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2003. , 64 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 799
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-27457Local ID: 12110ISBN: 91-7373-485-3 (print)OAI: oai:DiVA.org:liu-27457DiVA: diva2:248009
Public defence
2003-09-05, Aulan, Administrationshuset, Hälsouniversitet, Linköping, 13:00 (Swedish)
Opponent
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-10-12Bibliographically approved
List of papers
1. Regulation of melanosome movement by MAP kinase
Open this publication in new window or tab >>Regulation of melanosome movement by MAP kinase
2003 (English)In: Pigment Cell Research, ISSN 0893-5785, E-ISSN 1600-0749, Vol. 16, no 3, 215-221 p.Article in journal (Refereed) Published
Abstract [en]

Our objectives were to further characterize the signaling pathways in melatonin-induced aggregation in Xenopus melanophores, specifically to investigate a possible role of mitogen-activated protein kinase (MAPK). By Western blotting we found that melatonin activates MAPK, which precedes melanosome aggregation measured in a microplate reader. Activation of MAPK, tyrosine phosphorylation of a previously described 280-kDa protein, and melanosome aggregation are sensitive to PD98059, a selective inhibitor of MAPK kinase. The MAPK activation is also decreased by the adenylate cyclase stimulant forskolin. In summary, we found that MAPK is activated during melatonin-induced melanosome aggregation. Activation was decreased by an inhibitor of MAPK kinase, and by forskolin. In addition to inhibition of cyclic adenosine 3′,5′-monophosphate (cAMP), reduction in protein kinase A activity (PKA), and activation of protein phosphatase 2A, we suggest that melatonin receptors activate the MAPK cascade and tyrosine phosphorylation of the 280-kDa protein. Although the cAMP/PKA signaling pathway is the most prominent, our data suggest that simultaneous activation of the MAPK cascade is of importance to obtain a completely aggregated state. This new regulatory mechanism of organelle transport by the MAPK cascade might be important in other eukaryotic cells.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26778 (URN)10.1034/j.1600-0749.2003.00048.x (DOI)11383 (Local ID)11383 (Archive number)11383 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-10-12Bibliographically approved
2. Phosphoinositide 3-kinase is involved in Xenopus and Labrus melanophore aggregation
Open this publication in new window or tab >>Phosphoinositide 3-kinase is involved in Xenopus and Labrus melanophore aggregation
2003 (English)In: Cellular Signalling, ISSN 0898-6568, E-ISSN 1873-3913, Vol. 15, no 12, 1119-1127 p.Article in journal (Refereed) Published
Abstract [en]

Melanophores are pigmented cells capable of quick colour changes through coordinated transport of their intracellular pigment granules. We demonstrate the involvement of phosphoinositide 3-kinase (PI3-K) in Xenopus and Labrus aggregation by the use of the PI3-K inhibitor, LY-294002. In Xenopus, wortmannin-insensitive PI3-K was found to be essential for the aggregation, mitogen-activated protein kinase (MAPK) activation and tyrosine phosphorylation of a 280-kDa protein, and for the maintenance of low cyclic adenosine 3′:5′-monophosphate (cAMP) during the aggregated state. Pre-aggregated cells disperse completely to LY-294002 at 50–100 μM, involving a transient elevation in cAMP due to adenylate cyclase (AC) stimulation or to inhibition of cyclic nucleotide phosphodiesterase (PDE). The inactive analogue LY-303511 did not induce dispersion at the same concentrations. PDE4 and/or PDE2 was found to be involved in melanosome aggregation. The similar kinetics of LY-294002 and various PDE inhibitors indicates that the elevation of cAMP might be due to inhibition of PDE. In Labrus melanophores, LY-294002 had a less dramatic effect, probably due to less dependence on PDE in regulation of cAMP levels. In Xenopus aggregation, we suggest that melatonin stimulation of the Mel1c receptor via Gβγ activates PI3-K that, directly or indirectly via MAPK, activates PDE.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26779 (URN)10.1016/S0898-6568(03)00111-6 (DOI)11384 (Local ID)11384 (Archive number)11384 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-10-12Bibliographically approved
3. Myosin V is the rate-determinative step in Xenopus melanophore aggregation
Open this publication in new window or tab >>Myosin V is the rate-determinative step in Xenopus melanophore aggregation
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In Xenopus melanophores, melatonin induce melanosome aggregation via activation of its receptor Mel1c, coupled to inhibitory G proteins, adenylate cyclase deactivation, cyclic adenosine 3':5'-monophosphate (cAMP) decrease, protein kinase A inhibition, protein phophatase 2A activation, and serine/threonine dephosphorylations. Myosin V is the motor protein responsible for transporting melanosomes along actin filaments. Myosin V has been demonstrated to be necessary for melanosome dispersion and to keep the dispersed state. We have previously shown that melatonin induce activation of phosphoinositide-3 kinase, mitogen-activated protein kinase and tyrosine phosphorylation of a 280-kDa protein. Here we characterize the kinetics of latrunculin A-induced aggregation, and show that latrunculin A aggregate melanophores with the same kinetics as melatonin. This indicates that the downstream mechanisms might be similar although their primary targets in the cells are totally different. We suggest that both drugs act by inhibiting myosin V, the rate-determinative step for melanosome aggregation. Our data suggest that dynein is not up regulated during aggregation, as previously suggested by others,

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-84527 (URN)
Available from: 2012-10-11 Created: 2012-10-11 Last updated: 2012-10-12Bibliographically approved
4. Microplate based biosensing with a computer screen aided technique
Open this publication in new window or tab >>Microplate based biosensing with a computer screen aided technique
2003 (English)In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 19, no 1, 35-41 p.Article in journal (Refereed) Published
Abstract [en]

Melanophores, dark pigment cells from the frog Xenopus laevis, have the ability to change light absorbance upon stimulation by different biological agents. Hormone exposure (e.g. melatonin or α-melanocyte stimulating hormone) has been used here as a reversible stimulus to test a new compact microplate reading platform. As an application, the detection of the asthma drug formoterol in blood plasma samples is demonstrated. The present system utilizes a computer screen as a (programmable) large area light source, and a standard web camera as recording media enabling even kinetic microplate reading with a versatile and broadly available platform, which suffices to evaluate numerous bioassays. Especially in the context of point of care testing or self testing applications these possibilities become advantageous compared with highly dedicated comparatively expensive commercial systems.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26777 (URN)10.1016/S0956-5663(03)00132-5 (DOI)11382 (Local ID)11382 (Archive number)11382 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-10-12Bibliographically approved
5. Is effect of (S;S)-formoterol due to contamination of (R;R)-formoterol?
Open this publication in new window or tab >>Is effect of (S;S)-formoterol due to contamination of (R;R)-formoterol?
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Formoterol is a long acting selective ß2-adrenoceptor (ß2-AR) agonist of the so-called third generation of ß-adrenoceptor agonists. lt also has an onset action comparable to most short acting ß2-AR agonists. Formoterol has two chiral centres making four enantiomers possible. In this study we have examined (R;R)- and (S;S)-formoterol relaxing effect on guinea pig tracheal ring preparations, affinity to human ß2-AR in transfected COS-7 cells and the ability to influence pigment movement in frog melanophores with stable expression of human ß2AR. We also compared single concentration curves versus cumulative concentration curves on guinea pig tracheal preparations. In all three systems the (R;R)-formoterol is the most potent ß2AR agonist compered to (S;S)-formoterol with eudismic ratios ranging from 11 to 75. We also measure and theoretically calculated the effect of (S;S)-formoterol. VVhen the contamination of (R;R)-formoterol was subtracted the (S;S)-formoterol had effect, although approximately 72 times less then (R;R)-formoterol. We conclude that (R;R)-formoterol is the most potent ß2-AR agonist in three different systems and that (S;S)-formoterol posses an ß2-AR effect. We also show that cumulative concentration curves have higher EC50 values compered to single concentration curves and that this might be a consequence of recaptor desensitisation.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-84528 (URN)
Available from: 2012-10-12 Created: 2012-10-11 Last updated: 2012-10-12Bibliographically approved

Open Access in DiVA

No full text

Authority records BETA

Andersson, Tony P. M.

Search in DiVA

By author/editor
Andersson, Tony P. M.
By organisation
PharmacologyFaculty of Health Sciences
Medical and Health Sciences

Search outside of DiVA

GoogleGoogle Scholar

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 248 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf