Calcium channels in chromaffin cells: focus on L and T types.
Voltage-gated Ca2+ channels (Cav) are highly expressed in the adrenal chromaffin cells of mammalian species. Besides shaping action potential waveforms, they are directly involved in the excitation-secretion coupling underlying catecholamine release and, possibly, control other Ca2+-dependent events that originate near the membrane. These functions are shared by a number of Cav channel types (L, N, P/Q, R and T) which have different structure-function characteristics and whose degree of expression changes remarkably among mammalian species. Understanding precisely the functioning of each voltage-gated Ca2+ channels is a crucial task that helps clarifying the Ca2+-dependent mechanisms controlling exocytosis during physiological and pathological conditions. In this paper, we focus on classical and new roles that L- and T-type channels play in the control of chromaffin cell excitability and neurotransmitter release. Interestingly, L-type channels are shown to be implicated in the spontaneous autorhythmicity of chromaffin cells, while T-type channels, which are absent in adult chromaffin cells, are coupled with secretion and can be recruited following long-term beta-adrenergic stimulation or chronic hypoxia. This suggests that like other cells, adrenal chromaffin cells undergo effective remodelling of membrane ion channels and cell functioning during prolonged stress conditions.
Marcantoni
A
A
Department of Neuroscience, NIS Centre of Excellence, CNISM Research Unit, Torino, Italy.
Carabelli
V
V
Comunanza
V
V
Hoddah
H
H
Carbone
E
E
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000502:physiology*; D020747:Calcium Channels, T-Type / Q000502:physiology*; D020013:Calcium Signaling; D002395:Catecholamines / Q000378:metabolism; D019439:Chromaffin Cells / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating; D018408:Patch-Clamp Techniques
D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D002395:Catecholamines; D002118:Calcium