Abstract
Here we report c-Abl kinase inhibition mediated by a phosphotyrosine located in trans in the c-Abl substrate, Abi1. The mechanism, which is pertinent to the nonmyristoylated c-Abl kinase, involves high affinity concurrent binding of the phosphotyrosine pY213 to the Abl SH2 domain and binding of a proximal PXXP motif to the Abl SH3 domain. Abi1 regulation of c-Abl in vivo appears to play a critical role, as demonstrated by inhibition of pY412 phosphorylation of the nonmyristoylated Abl by coexpression of Abi1. Pervanadate-induced c-Abl kinase activity was also reduced upon expression of the wild type Abi1 but not by expression of the Y213 to F213 mutant Abi1 in LNCaP cells, which are naturally deficient in the regulatory pY213. Our findings suggest a novel mechanism by which Abl kinase is regulated in cells.