C-terminal Fragments of the α1C(CaV1.2) Subunit Associate with and Regulate L-type Calcium Channels Containing C-terminal-truncated α1CSubunits

• Published in: The Journal of biological chemistry 2001-06, Vol.276 (24), p.21089
• Main Authors: Tianyan Gao, Adolfo E. Cuadra, Hong Ma, Moritz Bünemann, Brian L. Gerhardstein, Tong Cheng, Robert Ten Eick, M. Marlene Hosey
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M008000200

L-type Ca 2+ channels in native tissues have been found to contain a pore-forming α 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 α 1C (Ca V 1.2) subunits, we performed electrophysiological and biochemical experiments. In tsA201 cells expressing either wild type or C-terminal-truncated α 1C subunits in combination with a β 2a subunit, truncation of the α 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 α 1C subunits. Dialysis of cells expressing the truncated α 1C subunits with C-terminal fragments applied through the patch pipette reconstituted the inhibition of the channels seen with full-length α 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 α 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 α 1C subunit can associate with C-terminal-truncated α 1C subunits and inhibit the currents through L-type Ca 2+ channels.