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Negative regulation of Rap1 activation by the Cbl E3 ubiquitin ligase
Author(s) -
Shao Yuan,
Elly Chris,
Liu YunCai
Publication year - 2003
Publication title -
embo reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.584
H-Index - 184
eISSN - 1469-3178
pISSN - 1469-221X
DOI - 10.1038/sj.embor.embor813
Subject(s) - rap1 , ubiquitin ligase , guanine nucleotide exchange factor , ubiquitin , signal transducing adaptor protein , microbiology and biotechnology , chemistry , signal transduction , biology , biochemistry , gene
Cbl functions as an adaptor protein by interacting with other signalling molecules to form multimolecular complexes. Previous studies have proposed that Cbl is also a positive regulator of CrkL–C3G signalling, which leads to Rap1 activation. However, there is a lack of genetic evidence for a physiological function of Cbl in regulating this pathway. Here, we show that Cbl deficiency results in enhanced activation of Rap1. Cbl was shown to promote the ubiquitylation of CrkL without any apparent effect on its stability. Remarkably, the membrane translocation of C3G, its association with CrkL, and the guanine‐nucleotide exchange activity of C3G were all increased in Cbl −/− thymocytes. Consistent with a function of Rap1 in integrin activation, enhanced integrin‐mediated cell adhesion was also seen in Cbl −/− thymocytes. Thus, Cbl negatively regulates Rap1 activation, probably through a proteolysis‐independent E3‐ubiquitin‐ligase activity of Cbl that modulates protein–protein interactions.