ASSOCIATION OF P62, A MULTIFUNCTIONAL SH2-DOMAIN AND SH3-DOMAIN BINDING-PROTEIN, WITH SRC FAMILY TYROSINE KINASES, GRB2, AND PHOSPHOLIPASE-C-GAMMA-1

src family tyrosine kinases contain two noncatalytic domains termed sr c homology 3 (SH3) and SH2 domains. Although several other signal tran sduction molecules also contain tandemly occurring SH3 and SH2 domains , the function of these closely spaced domains is not well understood. To identify the role of the SH3 domains of src family tyrosine kinase s, we sought to identify proteins that interacted with this domain. By using the yeast two-hybrid system, we identified p62, a tyrosine-phos phorylated protein that associates with p21(ras) GTPase-activating pro tein, as a src family kinase SH3-domain-binding protein. Reconstitutio n of complexes containing p62 and the src family kinase p59(fyn) in He La cells demonstrated that complex formation resulted in tyrosine phos phorylation of p62 and was mediated by both the SH3 and SH2 domains of p59(fyn). The phosphorylation of p62 by p59(fyn) required an intact S H3 domain, demonstrating that one function of the src family kinase SH 3 domains is to bind and present certain substrates to the kinase. As p62 contains at least five SH3 domain-binding motifs and multiple tyro sine phosphorylation sites, p62 may interact with other signalling mol ecules via SH3 and SH2 domain interactions. Here we show that the SH3 and/or SH2 domains of the signalling proteins Grb2 and phospholipase C gamma-1 can interact with p62 both in vitro and in vivo. Thus, we pro pose that one function of the tandemly occurring SH3 and SH2 domains o f src family kinases is to bind p62, a multifunctional SH3 and SH2 dom ain adapter protein, linking src family kinases to downstream effector and regulatory molecules.