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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Light modulates the melanophore response to alpha-MSH in Xenopus laevis: An analysis of the signal transduction crosstalk mechanisms involved

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Isoldi, Mauro Cesar [1, 2] ; Provencio, Ignacio [1] ; de Lauro Castrucci, Ana Maria [3]
Total Authors: 3
[1] Univ Virginia, Dept Biol, Charlottesville, VA 22904 - USA
[2] Univ Fed Ouro Preto, Dept Ciencias Biol, DECBI NUPEB, BR-35400000 Ouro Preto, MG - Brazil
[3] Univ Sao Paulo, Dept Fisiol, Inst Biociencias, BR-05508900 Sao Paulo - Brazil
Total Affiliations: 3
Document type: Journal article
Source: General and Comparative Endocrinology; v. 165, n. 1, p. 104-110, JAN 1 2010.
Web of Science Citations: 8

Melanin granule (melanosome) dispersion within Xenopus laevis melanophores is evoked either by light or alpha-MSH. We have previously demonstrated that the initial biochemical steps of light and alpha-MSH signaling are distinct, since the increase in cAMP observed in response to alpha-MSH was not seen after light exposure. cAMP concentrations in response to alpha-MSH were significantly lower in cells pre-exposed to light as compared to the levels in dark-adapted melanophores. Here we demonstrate the presence of an adenylyl cyclase (AC) in the Xenopus melanophore, similar to the mammalian type IX which is inhibited by Ca(2+)-calmodulin-activated phosphatase. This finding supports the hypothesis that the cyclase could be negatively modulated by a light-promoted Ca(2+) increase. In fact, the activity of calcineurin PP2B phosphatase was increased by light, which could result in AC IX inhibition, thus decreasing the response to alpha-MSH. St-Ht31, a disrupting agent of protein kinase A (PKA)-anchoring kinase A protein (AKAP) complex totally blocked the melanosome dispersing response to alpha-MSH, but did not impair the photo-response in Xenopus melanophores. Sequence comparison of a melanophore AKAP partial clone with GenBank sequences showed that the anchoring protein was a gravin-like adaptor previously sequenced from Xenopus non-pigmentary tissues. Co-immunoprecipitation of Xenopus AKAP and the catalytic subunit of PKA demonstrated that PKA is associated with AKAP and it is released in the presence of alpha-MSH. We conclude that in X laevis melanophores, AKAP12 (gravin-like) contains a site for binding the inactive PKA thus compartmentalizing PKA signaling and also possesses binding sites for PKC. Light diminishes alpha-MSH-induced increase of cAMP by increasing calcineurin (PP2B) activity, which in turn inhibits adenylyl cyclase type IX, and/or by activating PKC, which phosphorylates the gravin-like molecule, thus destabilizing its binding to the cell membrane. (C) 2009 Elsevier Inc. All rights reserved. (AU)

FAPESP's process: 06/03381-1 - Comparative physiology of peripheral clocks: clock genes (CLOCK, PER1, PER2, CRY1 and BMAL 1) and their modulation by light and hormones in fish, amphibians and mammals
Grantee:Ana Maria de Lauro Castrucci
Support type: Research Projects - Thematic Grants
FAPESP's process: 01/02460-1 - Melanopsin: comparative physiology of the gene and of the transduction of the luminous signal in pigmentary cells of fish, amphibians and mammals
Grantee:Ana Maria de Lauro Castrucci
Support type: Research Projects - Thematic Grants