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Regulation of melanosome movement by MAP kinase
Linköping University, Department of Medicine and Care, Pharmacology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medicine and Care, Pharmacology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medicine and Care, Pharmacology. Linköping University, Faculty of Health Sciences.
2003 (English)In: Pigment Cell Research, ISSN 1755-1471, E-ISSN 1755-148X, 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.

Place, publisher, year, edition, pages
2003. Vol. 16, no 3, 215-221 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-26778DOI: 10.1034/j.1600-0749.2003.00048.xLocal ID: 11383OAI: oai:DiVA.org:liu-26778DiVA: diva2:247328
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Melanophore signaling: regulation and application
Open this publication in new window or tab >>Melanophore signaling: regulation and application
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:nbn:se:liu:diva-27457 (URN)12110 (Local ID)91-7373-485-3 (ISBN)12110 (Archive number)12110 (OAI)
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

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Andersson, TonySvensson, Samuel

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