Title: The novel product of a five-exon stargazin-related gene abolishes Ca(V)2.2 calcium channel expression.

Authors: Fraser J Moss, Patricia Viard, Anthony Davies, Federica Bertaso, Karen M Page, Alex Graham, Carles Cantí, Mary Plumpton, Christopher Plumpton, Jeffrey J Clare, Annette C Dolphin

Journal, date & volume: EMBO J., 2002 Apr 2 , 21, 1514-23

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/11927536

Abstract
We have cloned and characterized a new member of the voltage-dependent Ca(2+) channel gamma subunit family, with a novel gene structure and striking properties. Unlike the genes of other potential gamma subunits identified by their homology to the stargazin gene, CACNG7 is a five-, and not four-exon gene whose mRNA encodes a protein we have designated gamma(7). Expression of human gamma(7) has been localized specifically to brain. N-type current through Ca(V)2.2 channels was almost abolished when co-expressed transiently with gamma(7) in either Xenopus oocytes or COS-7 cells. Furthermore, immunocytochemistry and western blots show that gamma(7) has this effect by causing a large reduction in expression of Ca(V)2.2 rather than by interfering with trafficking or biophysical properties of the channel. No effect of transiently expressed gamma(7) was observed on pre-existing endogenous N-type calcium channels in sympathetic neurones. Low homology to the stargazin-like gamma subunits, different gene structure and the unique functional properties of gamma(7) imply that it represents a distinct subdivision of the family of proteins identified by their structural and sequence homology to stargazin.