PHOSPHATIDYLINOSITOL 3-KINASE BINDS TO PROFILIN THROUGH THE P85-ALPHASUBUNIT AND REGULATES CYTOSKELETAL ASSEMBLY

Phosphatidylinositol 3-kinase (PI3-K), endowed with catalytic (110kDa) and regulatory (85kDa) subunits co-precipitates with anti-tyrosine an tibodies in mitogen-activated cells. Association of PI3-K with cytoske leton activates its catalytic activity through undeciphered mechanisms . Recently Singh et al., (Biochemistry, 35, 16544-16549, 1996) have sh own that profilin activates PI3-K activity in a concentration-dependen t manner. Consequently, we investigated the interaction between the PI 3-K and profilin employing the GSTp85 alpha fusion protein and the res ults indicate a specific interaction between pofilin and p85 alpha. Th e effect of p85 alpha/profilin complex on polymerization of actin mono mers was monitored fluorimetrically employing pyrene-labelled actin mo nomers. It was noted that p85 alpha/profilin complex on polymerization of actin monomers was monitored simultaneously bind to actin as well as to p85 alpha. The affinity of p85 alpha/profilin complex to actin i ncreases in the presence of p85 alpha subunit of PI3-K as compared to profilin itself.