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.21089-21097
• Main Authors: Gao, Tianyan, Cuadra, Adolfo E., Ma, Hong, Bünemann, Moritz, Gerhardstein, Brian L., Cheng, Tong, Eick, Robert Ten, Hosey, M.Marlene
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M008000200

L-type Ca2+ channels in native tissues have been found to contain a pore-forming α1 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 α1C(CaV1.2) subunits, we performed electrophysiological and biochemical experiments. In tsA201 cells expressing either wild type or C-terminal-truncated α1C subunits in combination with a β2a subunit, truncation of the α1C 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 α1C subunits. Dialysis of cells expressing the truncated α1C subunits with C-terminal fragments applied through the patch pipette reconstituted the inhibition of the channels seen with full-length α1C 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 α1C subunits. In addition, glutathioneS-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 α1C subunit can associate with C-terminal-truncated α1C subunits and inhibit the currents through L-type Ca2+ channels.