Systematic Identification of Splice Variants in Human P/Q-Type Channel α₁2.1 Subunits: Implications for Current Density and Ca²⁺-Dependent Inactivation

Abstract

P/Q-type (Ca v 2.1) calcium channels support a host of Ca 2ϩ -driven neuronal functions in the mammalian brain. Alternative splicing of the main ␣ 1A (␣ 1 2.1) subunit of these channels may thereby represent a rich strategy for tuning the functional profile of diverse neurobiological processes. Here, we applied a recently developed "transcript-scanning" method for systematic determination of splice variant transcripts of the human ␣ 1 2.1 gene. This screen identified seven loci of variation, which together have never been fully defined in humans. Genomic sequence analysis clarified the splicing mechanisms underlying the observed variation. Electrophysiological characterization and a novel analytical paradigm, termed strength-current analysis, revealed that one focus of variation, involving combinatorial inclusion and exclusion of exons 43 and 44, exerted a primary effect on current amplitude and a corollary effect on Ca 2ϩ -dependent channel inactivation. These findings significantly expand the anticipated scope of functional diversity produced by splice variation of P/Q-type channels.

Similar Intracellular Ca2+Requirements for Inactivation and Facilitation of Voltage-Gated Ca2+Channels in a Glutamatergic Mammalian Nerve Terminal

“…We therefore asked whether a reduction in the number of functional channels would reduce the rate of I Ca(V) inactivation (Soong et al, 2002;Kreiner et al, 2010). Figure 3A shows that this is indeed the case.…”

CaV2.1 voltage activated calcium channels and synaptic transmission in familial hemiplegic migraine pathogenesis

“…Cav2.1 channels are located throughout the mammalian brain and spinal cord (Westenbroek et al 1995) at presynaptic terminals (Catterall 1998, Wu et al 1999, Mintz et al 1995 and at somatodendritic membranes. The CACNA1A gene encoding Cav2.1 channels undergoes alternative splicing at multiple loci in an age-, gender-, and species-dependent manner (Bourinet et al 1999, Chang et al 2007, Chaudhuri et al 2005, Kanumilli et al 2006, Soong et al 2002. This mechanism resultes in multiple Cav2.1 splice variants with different outcomes in neuronal distribution and subcellular localization, biophysical properties, and sensitivity to ω-AgaIVA.…”

Contribution of calcium-dependent facilitation to synaptic plasticity revealed by migraine mutations in the P/Q-type calcium channel

“…1F, Right). Importantly, because of its reliance on global Ca 2+ levels (unlike that for CDF), CDI depends on Ca v 2.1 current density (22). Whereas the R192Q mutation has little effect on current density, the S218L mutation causes a large reduction in current density (23) (Fig.…”