Referenced in: none

Automatically associated channels: Cav1.2

Title: C-terminal fragments of the alpha 1C (CaV1.2) subunit associate with and regulate L-type calcium channels containing C-terminal-truncated alpha 1C subunits.

Authors: T Gao, A E Cuadra, H Ma, M Bünemann, B L Gerhardstein, T Cheng, R T Eick, M M Hosey

Journal, date & volume: J. Biol. Chem., 2001 Jun 15 , 276, 21089-97

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/11274161

Abstract
L-type Ca(2+) channels in native tissues have been found to contain a pore-forming alpha(1) subunit that is often truncated at the C terminus. However, the C terminus contains many important domains that regulate channel function. To test the hypothesis that C-terminal fragments may associate with and regulate C-terminal-truncated alpha(1C) (Ca(V)1.2) subunits, we performed electrophysiological and biochemical experiments. In tsA201 cells expressing either wild type or C-terminal-truncated alpha(1C) subunits in combination with a beta(2a) subunit, truncation of the alpha(1C) subunit by as little as 147 amino acids led to a 10-15-fold increase in currents compared with those obtained from control, full-length alpha(1C) subunits. Dialysis of cells expressing the truncated alpha(1C) subunits with C-terminal fragments applied through the patch pipette reconstituted the inhibition of the channels seen with full-length alpha(1C) subunits. In addition, C-terminal deletion mutants containing a tethered C terminus also exhibited the C-terminal-induced inhibition. Immunoprecipitation assays demonstrated the association of the C-terminal fragments with truncated alpha(1C) subunits. In addition, glutathione S-transferase pull-down assays demonstrated that the C-terminal inhibitory fragment could associate with at least two domains within the C terminus. The results support the hypothesis the C- terminal fragments of the alpha(1C) subunit can associate with C-terminal-truncated alpha(1C) subunits and inhibit the currents through L-type Ca(2+) channels.