Proteolytic processing of the C terminus of the alpha(1C) subunit
of L-type calcium channels and the role of a proline-rich domain
in membrane tethering of proteolytic fragments
J Biol Chem, 275 (12):
8556-63 (March 2000)Gerhardstein, B L Gao, T Bunemann, M Puri, T S Adair, A Ma, H Hosey,
M M R01 HL23306/HL/NHLBI NIH HHS/United States T32-DK07169/DK/NIDDK
NIH HHS/United States Research Support, U.S. Gov't, P.H.S. United
states The Journal of biological chemistry J Biol Chem. 2000 Mar
24;275(12):8556-63..Abstract
Although most L-type calcium channel alpha(1C) subunits isolated from
heart or brain are approximately 190-kDa proteins that lack approximately
50 kDa of the C terminus, the C-terminal domain is present in intact
cells. To test the hypothesis that the C terminus is processed but
remains functionally associated with the channels, expressed, full-length
alpha(1C) subunits were cleaved in vitro by chymotrypsin to generate
a 190-kDa C-terminal truncated protein and C-terminal fragments of
30-56 kDa. These hydrophilic C-terminal fragments remained membrane-associated.
A C-terminal proline-rich domain (PRD) was identified as the mediator
of membrane association. The alpha(1C) PRD bound to SH3 domains in
Src, Lyn, Hck, and the channel beta(2) subunit. Mutant alpha(1C)
subunits lacking either approximately 50 kDa of the C terminus or
the PRD produced increased barium currents through the channels,
demonstrating that these domains participate in the previously described
(Wei, X., Neely, a., Lacerda, A. E. Olcese, r., Stefani, E., Perez-Reyes,
E., and Birnbaumer, L. (1994) J. Biol. Chem. 269, 1635-1640) inhibition
of channel function by the C terminus.