COMPARISON OF EXOCYTOTIC MECHANISMS BETWEEN ACETYLCHOLINE-CONTAINING AND CATECHOLAMINE-CONTAINING VESICLES IN RAT PHEOCHROMOCYTOMA CELLS

The molecular mechanisms of exocytosis from two types of secretory org anelles, synaptic-like microvesicles and secretory vesicles, were comp ared by measuring acetylcholine (ACh) and catecholamine (CA) release f rom a newly isolated PC12 subclone, PC12-C3 which contains a high leve l of Ach. Digitonin-permeabilized PC12-C3 cells released both transmit ters with similar Ca2+-dependency, Ca2+-evoked ACh and CA release from permeabilized cells were increased in the presence of MgATP, suggesti ng the existence of a MgATP-dependent priming step prior to the Ca2+-t riggered fusion step in both ACh release and CA release. The non-hydro lyzable analogue of GTP, guanosine 5'-(gamma-thio)triphosphate (GTP ga mma S), produced both ACh and CA release from permeabilized cells in t he absence of Ca2+. Pretreatment with a phorbol ester which activates protein kinase C, potentiated depolarization-induced ACh and CA releas e from unpermeabilized cells. These results indicate that exocytosis f rom two distinct vesicle populations are mediated by the same basic mo lecular mechanisms. (C) 1997 Academic Press.