Premium
A critical GxxxA motif in the γ 6 calcium channel subunit mediates its inhibitory effect on Cav3.1 calcium current
Author(s) -
Lin Zuojun,
Witschas Katja,
Garcia Thomas,
Chen RenShiang,
Hansen Jared P.,
Sellers Zachary M.,
Kuzmenkina Elza,
Herzig Stefan,
Best Philip M.
Publication year - 2008
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2008.159111
Subject(s) - n type calcium channel , protein subunit , r type calcium channel , calcium channel , voltage dependent calcium channel , chemistry , hek 293 cells , microbiology and biotechnology , cav1.2 , ion channel , biophysics , inhibitory postsynaptic potential , calcium , t type calcium channel , biology , biochemistry , neuroscience , receptor , gene , organic chemistry
The eight members of the calcium channel γ subunit family are integral membrane proteins that regulate the expression and behaviour of voltage and ligand gated ion channels. While a subgroup consisting of γ 2 , γ 3 , γ 4 and γ 8 (the TARPs) modulate AMPA receptor localization and function, the γ 1 and γ 6 subunits conform to the original description of these proteins as regulators of voltage gated calcium channels. We have previously shown that the γ 6 subunit is highly expressed in atrial myocytes and that it is capable of acting as a negative modulator of low voltage activated calcium current. In this study we extend our understanding of γ 6 subunit modulation of low voltage activated calcium current. Using engineered chimeric constructs, we demonstrate that the first transmembrane domain (TM1) of γ 6 is necessary for its inhibitory effect on Cav3.1 current. Mutational analysis is then used to identify a unique GxxxA motif within TM1 that is required for the function of the subunit strongly suggesting the involvement of helix–helix interactions in its effects. Results from co‐immunoprecipitation experiments confirm a physical association of γ 6 with the Cav3.1 channel in both HEK cells and atrial myocytes. Single channel analysis reveals that binding of γ 6 reduces channel availability for activation. Taken together, the results of this study provide both a molecular and a mechanistic framework for understanding the unique ability of the γ 6 calcium channel subunit to modulate low voltage activated (Cav3.1) calcium current density.