title: Phospholipase Cη2 Activation Redirects Vesicle Trafficking by Regulating F-actin.
abstract: PI(4,5)P2 localizes to sites of dense core vesicle exocytosis in neuroendocrine cells and is required for Ca(2+)-triggered vesicle exocytosis, but the impact of local PI(4,5)P2 hydrolysis on exocytosis is poorly understood. Previously, we reported that Ca(2+)-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 (also known as CADPS) and ubiquitous Munc13-2 in PC12 cells. Here we describe an additional role for PLCη2 in vesicle exocytosis as a Ca(2+)-dependent regulator of the actin cytoskeleton. Depolarization of neuroendocrine PC12 cells with 56 or 95 mm KCl buffers increased peak Ca(2+) levels to ~400 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 Ca(2+)-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 Ca(2+)-dependent regulator of F-actin dynamics and vesicle trafficking.
authors.affiliation: From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706.
authors.forename: Masaki
authors.initials: M
authors.lastname: Yamaga
authors.affiliation: From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706.
authors.forename: D Michelle
authors.initials: DM
authors.lastname: Kielar-Grevstad
authors.affiliation: From the Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706 tfmartin@wisc.edu.
authors.forename: Thomas F J
authors.initials: TF
authors.lastname: Martin
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D016716:PC12 Cells; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000235:genetics / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D051381:Rats; D022142:Secretory Vesicles / Q000201:enzymology* / Q000235:genetics; D010738:Type C Phospholipases / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; C485549:Unc13b protein, mouse; C117991:Unc13b protein, rat; D011189:Potassium Chloride; D010738:Type C Phospholipases; D002118:Calcium
keywords: actin; exocytosis; membrane trafficking; phosphoinositide; phospholipase C; vesicles