Ca2+-dependent actin filament-severing protein that has a regulatory function in exocytosis by affecting the organization of the microfilament network underneath the plasma membrane.Severing activity is inhibited by phosphatidylinositol 4,5-bis-phosphate.In vitro, also has barbed end capping and nucleating activities in the presence of Ca2+. Required for megakaryocyte differentiation, maturation, polyploidization and apoptosis with the release of platelet-like particles.