Abstract
Voltage-gated Ca$^2+$ channels mediate Ca$^2+$ entry into
cells in response to membrane depolarization. Electrophysiological
studies reveal different Ca$^2+$ currents designated L-, N-,
P-, Q-, R-, and T-type. The high-voltage-activated Ca$^2+$ channels
that have been characterized biochemically are complexes of a pore-forming
alpha1 subunit of approximately 190-250 kDa; a transmembrane, disulfide-linked
complex of alpha2 and delta subunits; an intracellular beta subunit;
and in some cases a transmembrane gamma subunit. Ten alpha1 subunits,
four alpha2delta complexes, four beta subunits, and two gamma subunits
are known. The Cav1 family of alpha1 subunits conduct L-type Ca$^2+$
currents, which initiate muscle contraction, endocrine secretion,
and gene transcription, and are regulated primarily by second messenger-activated
protein phosphorylation pathways. The Cav2 family of alpha1 subunits
conduct N-type, P/Q-type, and R-type Ca$^2+$ currents, which
initiate rapid synaptic transmission and are regulated primarily
by direct interaction with G proteins and SNARE proteins and secondarily
by protein phosphorylation. The Cav3 family of alpha1 subunits conduct
T-type Ca$^2+$ currents, which are activated and inactivated
more rapidly and at more negative membrane potentials than other
Ca$^2+$ current types. The distinct structures and patterns of
regulation of these three families of Ca$^2+$ channels provide
a flexible array of Ca$^2+$ entry pathways in response to changes
in membrane potential and a range of possibilities for regulation
of Ca$^2+$ entry by second messenger pathways and interacting
proteins.
Description
The whole bibliography file I use.
Links and resources
Tags