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

The role of calcium, calcium-activated K+ channels, and tyrosine/kinase in psoralen-evoked responses in human melanoma cells

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Author(s):
M.C. Isoldi ; E.A. Pereira ; M.A. Visconti ; A.M.L. Castrucci
Total Authors: 4
Document type: Journal article
Source: Brazilian Journal of Medical and Biological Research; v. 37, n. 4, p. 559-568, Abr. 2004.
Abstract

8-Methoxy psoralen (8-MOP) exerts a short-term (24 h) mitogenic action, and a long-term (48-72 h) anti-proliferative and melanogenic action on two human melanoma cell lines, SK-Mel 28 and C32TG. An increase of intracellular calcium concentration was observed by spectrofluorometry immediately after the addition of 0.1 mM 8-MOP to both cell lines, previously incubated with calcium probe fluo-3 AM (5 µM). The intracellular Ca2+ chelator BAPTA/AM (1 µM) blocked both early (mitogenic) and late (anti-proliferative and melanogenic) 8-MOP effects on both cell lines, thus revealing the importance of the calcium signal in both short- and long-term 8-MOP-evoked responses. Long-term biological assays with 5 and 10 mM tetraethylammonium chloride (TEA, an inhibitor of Ca2+-dependent K+ channels) did not affect the responses to psoralen; however, in 24-h assays 10 mM TEA blocked the proliferative peak, indicating a modulation of Ca2+-dependent K+ channels by 8-MOP. No alteration of cAMP basal levels or forskolin-stimulated cAMP levels was promoted by 8-MOP in SK-Mel 28 cells, as determined by radioimmunoassay. However, in C32TG cells forskolin-stimulated cAMP levels were further increased in the presence of 8-MOP. In addition, assays with 1 µM protein kinase C and calcium/calmodulin-dependent kinase inhibitors, Ro 31-8220 and KN-93, respectively, excluded the participation of these kinases in the responses evoked by 8-MOP. Western blot with antibodies anti-phosphotyrosine indicated a 92% increase of the phosphorylated state of a 43-kDa band, suggesting that the phosphorylation of this protein is a component of the cascade that leads to the increase of tyrosinase activity. (AU)

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