T-type channels become highly permeable to sodium ions using an alternative extracellular turret region (S5-P) outside the selectivity filter.

ABSTRACT: T-type (Cav3) channels are categorized as calcium channels, but invertebrate ones can be highly sodium-selective channels. We illustrate that the snail LCav3 T-type channel becomes highly sodium-permeable through exon splicing of an extracellular turret and descending helix in domain II of the four-domain Cav3 channel. Highly sodium-permeable T-type channels are generated without altering the invariant ring of charged residues in the selectivity filter that governs calcium selectivity in calcium channels. The highly sodium-permeant T-type channel expresses in the brain and is the only splice isoform expressed in the snail heart. This unique splicing of turret residues offers T-type channels a capacity to serve as a pacemaking sodium current in the primitive heart and brain in lieu of Nav1-

SUBMITTER: Senatore A 

PROVIDER: S-EPMC4002102 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature