c-ABL tyrosine kinase activity is regulated by association with a novel SH3-domain-binding protein.
The c-ABL tyrosine kinase is activated following either the loss or mutation of its Src homology domain 3 (SH3), resulting in both increased autophosphorylation and phosphorylation of cellular substrates and cellular transformation. This suggests that the SH3 domain negatively regulates c-ABL kinase activity. For several reasons this regulation is thought to involve a cellular protein that binds to the SH3 domain. Hyperexpression of c-ABL results in an activation of its kinase, the kinase activity of purified c-ABL protein in the absence of cellular proteins is independent of either the presence or absence of a SH3 domain, and point mutations and deletions within the SH3 domain are sufficient to activate c-ABL transforming ability. To identify proteins that interact with the c-ABL SH3 domain, we screened a cDNA library by the yeast two-hybrid system, using the c-ABL SH3SH2 domains as bait. We identified a novel protein, AAP1 (ABL-associated protein 1), that associates with these c-ABL domains and fails to bind to the SH3 domain in the activated oncoprotein BCRABL. Kinase experiments demonstrated that in the presence of AAP1, the ability of c-ABL to phosphorylate either glutathione S-transferase-CRK or enolase was inhibited. In contrast, AAP1 had little effect on the phosphorylation of glutathione S-transferase-CRK by the activated ABL oncoproteins v-ABL and BCRABL. We conclude that AAP1 inhibits c-ABL tyrosine kinase activity but has little effect on the tyrosine kinase activities of oncogenic BCRABL or v-ABL protein and propose that AAP1 functions as a trans regulator of c-ABL kinase. Our data also indicate that loss of susceptibility to AAP1 regulation correlates with oncogenicity of the activated forms of c-ABL.
Zhu
J
J
Department of Biochemistry, School of Medicine, Temple University, Philadelphia, Pennsylvania 19140, USA.
Shore
S K
SK
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D004791:Enzyme Inhibitors / Q000302:isolation & purification*; D016313:Genes, abl; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016315:Proto-Oncogene Proteins c-abl / Q000235:genetics*; D018909:src Homology Domains / Q000235:genetics*
D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D016315:Proto-Oncogene Proteins c-abl