Phospholipase C{eta}2 Activation Re-directs Vesicle Trafficking By Regulating F-actin [Lipids]

October 2nd, 2015 by Yamaga, M., Kielar-Grevstad, D. M., Martin, T. F. J.

PI(4,5)P2 localizes to sites of dense-core vesicle exocytosis in neuroendocrine cells and is required for Ca2+-triggered vesicle exocytosis, but the impact of local PI(4,5)P2 hydrolysis on exocytosis is poorly understood. Previously we reported that Ca2+-dependent activation of phospholipase Cη2 (PLCη2) catalyzes PI(4,5)P2 hydrolysis, which affected vesicle exocytosis by regulating the activities of the lipid-dependent priming factors CAPS (aka CADPS) and ubiquitous Munc13-2 in PC12 cells. Here we describe an additional role for PLCη2 in vesicle exocytosis as a Ca2+-dependent regulator of the actin cytoskeleton. Depolarization of neuroendocrine PC12 cells with 56 mM or 95 mM KCl buffers increased peak Ca2+ levels to ~400 nM or ~800 nM, respectively, but elicited similar numbers of vesicle exocytic events. However, 56 mM K+ preferentially elicited the exocytosis of plasma membrane-resident vesicles whereas 95 mM K+ preferentially elicited the exocytosis of cytoplasmic vesicles arriving during stimulation. Depolarization with 95 mM K+ but not with 56 mM K+ activated PLCη2 to catalyze PI(4,5)P2 hydrolysis. The decrease in PI(4,5)P2 promoted F-actin disassembly, which increased exocytosis of newly-arriving vesicles. Consistent with its role as a Ca2+-dependent regulator of the cortical actin cytoskeleton, PLCη2 localized with F-actin filaments. The results highlight the importance of PI(4,5)P2 for coordinating cytoskeletal dynamics with vesicle exocytosis, and reveal a new role for PLCη2 as a Ca2+-dependent regulator of F-actin dynamics and vesicle trafficking.