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Cooperative Role of Caveolin‐1 and Cbp in Csk‐Mediated Inactivation of Src
Author(s) -
Place Aaron T,
Liu Guoquan,
Shinin Vasily,
Chen Zhenlong,
Minshall Richard D
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.772.2
Subject(s) - proto oncogene tyrosine protein kinase src , phosphorylation , signal transducing adaptor protein , microbiology and biotechnology , chemistry , downregulation and upregulation , immunoprecipitation , biology , biochemistry , gene
c‐Src is inactivated by C‐terminal Src Kinase (Csk). A membrane adaptor such as Csk Binding Protein (Cbp) is required to recruit and upregulate Csk activity at the plasma membrane. To determine whether Cav‐1 and Cbp cooperatively regulate Csk activity, we investigated c‐Src activity regulation in the presence and absence of each adaptor. In Cav‐1−/− cells, we observed greater expression of Cbp than in WT cells, but equivalent c‐Src activity and expression suggesting that Cbp compensated for the lack of Cav‐1. Fractionation studies of WT and Cav‐1−/− cells revealed that Csk is present at the membrane under basal conditions in equivalent amounts. Depletion of Cbp by siRNA increased Cav‐1 Y14 phosphorylation without an increase in basal c‐Src activity. This suggests that Cav‐1, like Cbp, also compensates for the lack of Cbp and coordinates Csk in a phospho‐dependant manner to keep c‐Src inactive. Furthermore, Cbp, Csk, and Cav‐1 co‐immunoprecipitated, and treatment of Cav‐1−/− cells with Cbp siRNA increased basal c‐Src activity. Thus, Cav‐1 and Cbp cooperate to negatively regulate Src activity by recruiting Csk to the membrane where it phosphorylates Src Y529. In the absence of Cav‐1 or Cbp, there is a compensatory increase in phosphorylation or expression of the other to maintain Src in an inhibited state. When both adapters are absent, basal Src activity is increased. Sponsored by AHA Predoctoral Fellowship #0910026G.