Cloning and functional expression of novel N-type Ca2+ channel variants

Abstract

Voltage-dependent Ca2+ channels are structurally and functionally diverse. As Ca2+ currents recorded from embryonic chick dorsal root ganglion (DRG) neurons differ significantly from their mammalian counterparts, information on the primary sequence of the chick channels will help define the structural underpinnings of Ca2+ channel function. Here, we report the cloning and functional expression of full-length Ca2+ channel α(1B) subunit cDNAs derived from chick DRGs. Two variable regions (A and B) have been identified in the cytoplasmic linker between repeats I and II; a third (C) in the carboxyl terminus extends the open reading frame by 525 nucleotides. The A and C inserts are absent, and the B insert is present in all other class B clones reported to date. The unique shorter channels appear to predominate in DRG neurons. Results represent a requisite first step in defining the structural elements that underlie variations in function and modulation of Ca2+ channels.