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 (PIP2) (By similarity). 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. Plays a role in osteoclastogenesis (OCG) and actin cytoskeletal organization in osteoclasts. Regulates chondrocyte proliferation and differentiation. Inhibits cell proliferation and tumorigenesis. Signaling is mediated by MAPK, p38 and JNK pathways.