Caveolin-1 is phosphorylated on Tyr14 in response to both oxidative and hyperosmotic stress. In the present paper, we show that this phosphorylation requires activation of the Src family kinase Fyn. Stress-induced caveolin phosphorylation was abolished by three Src kinase inhibitors, SU6656, PP2 and PD180970, and was not observed in fibroblasts derived from a Src, Yes and Fyn triple-knockout mouse (SYF−/−). Using cell lines derived from single-kinase-knockout mice (Src−/−, Yes−/− and Fyn−/−), we show that expression of Fyn, but not Src or Yes, is required for stress-induced caveolin phosphorylation. Heterologous expression of Fyn in the SYF−/− and Fyn−/− cells was sufficient to reconstitute stress-induced caveolin phosphorylation, and overexpression of Fyn in wild-type cells induced hyperphosphorylation of caveolin. Fyn was autophosphorylated following oxidative stress, verifying activation of this kinase. Interestingly, there was a concomitant increase in the phosphorylation of Fyn on its Csk (C-terminal Src kinase) site, indicating feedback inhibition. Csk binds to phosphocaveolin [Cao, Courchesne and Mastick (2002) J. Biol. Chem. 277, 8771–8774] and should phosphorylate any co-localized Src-family kinases. Oxidative-stress-induced phosphorylation of caveolin-1 also requires expression of Abl [Sanguinetti and Mastick (2003) Cell Signal. 15, 289–298]. Using inhibitors and cells derived from knockout mice, we verified a requirement for both Abl and Fyn in stress-induced caveolin phosphorylation in a single cell type. Our data suggest a novel mechanism for attenuation of Src-kinase activity by Abl: stable tyrosine phosphorylation of a scaffolding protein, caveolin, and recruitment of Csk. Paxillin, a substrate of both Abl and Src, organizes a similar regulatory complex.
Fyn is required for oxidative- and hyperosmotic-stress-induced tyrosine phosphorylation of caveolin-1
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Amy R. SANGUINETTI, Haiming CAO, Cynthia CORLEY MASTICK; Fyn is required for oxidative- and hyperosmotic-stress-induced tyrosine phosphorylation of caveolin-1. Biochem J 15 November 2003; 376 (1): 159–168. doi: https://doi.org/10.1042/bj20030336
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