The immediately releasable pool of mouse chromaffin cell vesicles is coupled to P/Q calcium channels by the synaptic protein interaction site

YANINA ÁLVAREZ; ANDRÉS E. PEREZ BAY; ANA VERÓNICA BELINGHERI; SCOTT E. JAVIS; H. WILLIAM TEDFORD; GERALD ZAMPONI; FERNANDO D. MARENGO

Huerta Grande (Cordoba)

Congreso; Reunion Anual de la Sociedad Argentina de Investigacion en Neurociencia; 2011

Sociedad Argentina de Investigacion en Neurociencia

The immediately releasable pool (IRP) is a group of ready releasable vesicles closely associated with voltage dependent Ca2+ channels. We have previously shown that exocytosis of this pool is specifically coupled to P/Q Ca2+ current. Accordingly, in the present work we found that the Ca2+ current flowing through P/Q-type Ca2+ channels is 8 times more effective to induce exocytosis in response to short stimuli that the current flowing through L-type channels. To investigate the mechanism that may generate the coupling between IRP and P/Q-type channels we transiently expressed in chromaffin cells peptides corresponding to the synaptic protein interaction site (synprint) of Cav2.2, an amino acidic sequence of the Ca2+ channel that serves to maintain a close physical coupling with vesicles in synaptic terminals. This treatment reduced the efficiency of Ca2+ current to induce exocytosis to similar values as ù-agatoxin-IVA. In addition, the same treatment markedly reduced IRP exocytosis, but did not affect the exocytosis provoked by sustained electric or high K+ stimulation. In conclusion, our results indicate that synprint is a crucial factor for the establishment of the functional coupling between IRP vesicles and P/Q-type Ca2+ channels.