Calcium channel types contributing to chromaffin cell excitability, exocytosis and endocytosis

Voltage gated Ca2+ channels are effective voltage sensors of plasma membrane which convert cell depolarizations into Ca2+ signaling. The chromaffin cells of the adrenal medulla utilize a large number of Ca2+ channel types to drive the Ca2+-dependent release of catecholamines into blood circulation, during normal or stress-induced conditions. Some of the Ca2+ channels expressed in chromaffin cells (L, N, P/Q, R and T), however, do not control only vesicle fusion and catecholamine release. They also subserve a variety of key activities which are vital for the physiological and pathological functioning of the cell, like: (i) shaping the action potentials of electrical oscillations driven either spontaneously or by ACh stimulation, (ii) controlling the action potential frequency of tonic or bursts firing, (iii) regulating the compensatory and excess endocytosis following robust exocytosis and (iv) driving the remodeling of Ca2+ signaling which occurs during stressors stimulation. Here, we will briefly review the well-established properties of voltage-gated Ca2+ channels accumulated over the past three decades focusing on the most recent discoveries on the role that L- (Cav1.2, Cav1.3) and T-type (Cav3.2) channels play in the control of excitability, exocytosis and endocytosis of chromaffin cells in normal and stress-mimicking conditions