Distribution and Targeting Mechanisms of Voltage Activated Ca2+ Channels

摘要: Voltage dependent Ca^* channels control critical parameters of cell function. Their involvement in excitation contraction (EC)-coupling muscle, their role secretion pancreas, the acrosome reaction sperm and function fast slow signal transduction brain predicts a variety different channel complexes with defined biophysical properties. Since all these actions occur within specialized subcellular structures like triad muscle cells or presynaptic terminal neurons, have to be targeted specific site action. Thus mechanisms exist for subunit assembly transport complex. The human genome more than 20 subunits, which may assemble large combinations. Functional Ca * consists three four subunits designated tti, p, a2-8 y. tti is pore forming consisting domains, are connected via intracellular protein peptide bridges. ancillary a2-6 y interact intracellular, extracellular transmembrane regions OLi modulate Three families can distinguished according sequence homology ai electrophysiological pharmacological differences. These L-type chan­ nels, P/Q/N/R-type T-type channels. Further characterization predicted types obtained from projects will likely extend each subgroup define new types. We first describe distribution periphety then discuss what we know about destiny Ca^^ subunit. Distribution Channel Types Specified by Pore Forming Subunit appear already most primitive animals single ciliate Paramecium where they trigger regenerative action potential necessaty environment sensing. ^'^ In mammals expressed almost evety throughout tissues organs such as brain, pancreas testis. L-Type Channels CapI.I Ca^lA encoded Cayl.l, Cavl.2, Cavl.3 Cavl.4 OL\ subunits. were identified diameter fibers crab leg.^ Due its high concentration T-tubular system skeletal it was complex purified. This CayLl OL\, pia, CLx-^i yi subunit.^ CavLl ttisubunit contains DHP binding together other