Inositol hexakisphosphate pr mediated endocytosis

Membrane homeostasis is maintained by exocytosis and endocyM; tosis. The molecular mechanisms regulating the interplay between Pri these two processes are not clear. Inositol hexakisphosphate is (InsP6) is under metabolic control and serves as a signal in the se pancreatic f3 cell stimulus-secretion coupling by increasing Ca2+bli channel activity and insulin exocytosis. We now show that InsP6 pa also promotes dynamin I-mediated endocytosis in the pancreatic 13 la cell. This effect of InsP6 depends on calcineurin-induced dephosir phorylation and is accounted for by both activation of protein ce kinase C and inhibition of the phosphoinositide phosphatase i; synaptojanin and thereby formation of phosphatidylinositol 4,5m bisphosphate. In regulating both exocytosis and endocytosis, InsP6 m] thus may have an essential integral role in membrane trafficking. s