The focus of the project is to study tyrosine kinases, their mechanism of action, substrates that may correlate with transformation, and pharmacological agents which may potentially alter their activity. (1) We identified highly transforming mutants of the c-fgr proto-oncogene. Surprisingly, the normal c-fgr proto-oncogene was also found to be transforming, and this protein was subsequently observed to be growth-inhibitory in mouse fibroblasts. These findings emphasize that cell growth rate and transformation are distinct phenotypic properties. (2) Utilizing mutants of fgr, fyn, and src, we have identified a common 130 kd tyrosine phosphorylated protein (p130) that associates with activated src-family kinases and a 70 kd tyrosine phosphorylated protein that preferentially associates with activated versions of the fyn proto-oncogene. (3) Efforts to identify the associated p130 have lead to identification of a monoclonal antibody (obtained from Dr. T. Parsons) that reacts with this protein. Furthermore, we have found that p130 is markedly induced after transfection with activated src-family kinases. (4) Utilizing Dr. Parsons' anti-p85 monoclonal antibody, we identified another protein that associates with the fyn kinase. This tyrosine- phosphorylated protein contains an SH3 domain and appears to localize to regions of membrane adhesion. The p85 molecule is not associated with fgr or src, and current efforts are directed toward mapping the regions of fyn responsible for this association. (5) Studies in collaboration with K. Robbins and M. Cardinali reveal that suramin can markedly modulate tyrosine phosphorylation and growth in epithelial cancer cell lines. Preliminary observations suggest potentially interesting mechanisms may underlie these alterations.
