Effect of Rab11a in the regulated exocytosis of mouse chromaffin cells

GALLO, LUCIANA I; GALLO, LUCIANA I; MARENGO, FERNANDO D; MARENGO, FERNANDO D; ALFONSO BUENO, SAMUEL; ALFONSO BUENO, SAMUEL

Córdoba

Congreso; XXXIII Reunión anual de la Sociedad Argentina de Investigación en Neurociencias (SAN-2018); 2018

Sociedad Argentina de Investigación en Neurociencias

Chromaffin cell exocytosis is coupled to voltage dependent Ca2+ channels (VDCCs) activation. These cells present various pools of vesicles with different maturation level. The Immediately releasable pool (IRP) is composed of ready releasable vesicles very close to VDCCs and is released by short depolarizations. More prolonged stimulation is able to release the totality of the ready releasable pool and if stimulation is maintained exocytosis depends on the transport of vesicles from reserve pools. Some RabGTPases are involved in the secretion pathway but Rab11a has not yet been studied in chromaffin cells. We evaluated the effect of Rab11a on chromaffin cell exocytosis by expressing GFP-Rab11aQ70L, a constitutively active form, and mCherry-Rab11aS25N, a dominant negative form. We used patch-clamp/whole-cell to measure membrane capacitance. We observed a strong decline in the release of the IRP when either Rab11a mutants were expressed. In addition, both mutants showed a significant reduction in the total change of the membrane capacitance in response to ten 50 ms depolarizations (2 Hz), evidencing a decrease in the whole number of ready releasable vesicles. Images taken by confocal microscopy showed that mCherry-Rab11aS25N affected the distribution of GFP-Neuropeptide Y (NPY)-labeled secretory vesicles: NPY was concentrated in one big spot. These results suggest that Rab11a modulates the generation of secretory vesicles needed for the regulated exocytosis in chromaffin cells.