Phosphatidylinositol 4,5‐bisphosphate specifically stimulates PP60c‐src catalyzed phosphorylation of gelsolin and related actin‐binding proteins

Abstract
Gelsolin is a widely distributed Ca2+‐dependent regulator of the cortical actin network. We demonstrate that gelsolin is phosphorylated by pp60c‐src and that this phosphorylation is dramatically enhanced by phosphatidylinositol 4,5‐bisphosphate (PIP2), known to specifically interact with gelsolin. Other phospholipids display only a marginal effect. pp56lck, a tyrosine kinase of the same family, does not phosphorylate gelsolin. Other mammalian actin‐binding proteins such as profilin and CapG but also fragmin from Physarum polycephalum are similar targets for PIP2‐stimulated pp60c‐src phosphorylation.