The CaV? Subunit Protects the I-II Loop of the Voltage-gated Calcium Channel CaV2.2 from Proteasomal Degradation but Not Oligoubiquitination.

ABSTRACT: CaV? subunits interact with the voltage-gated calcium channel CaV2.2 on a site in the intracellular loop between domains I and II (the I-II loop). This interaction influences the biophysical properties of the channel and leads to an increase in its trafficking to the plasma membrane. We have shown previously that a mutant CaV2.2 channel that is unable to bind CaV? subunits (CaV2.2 W391A) was rapidly degraded (Waithe, D., Ferron, L., Page, K. M., Chaggar, K., and Dolphin, A. C. (2011) J. Biol. Chem. 286, 9598-9611). Here we show that, in the absence of CaV? subunits, a construct consisting of the I-II loop of CaV2.2 was directly ubiquitinated and degraded by the proteasome system. Ubiquitination could be prevented by mutation of all 12 lysine residues in the I-II loop to arginines. Including a palmitoylation motif at the N terminus of CaV2.2 I-II loop was insufficient to target it to the plasma membrane in the absence of CaV? subunits even when proteasomal degradation was inhibited with MG132 or ubiquitination was prevented by the lysine-to-arginine mutations. In the presence of CaV? subunit, the palmitoylated CaV2.2 I-II loop was protected from degradation, although oligoubiquitination could still occur, and was efficiently trafficked to the plasma membrane. We propose that targeting to the plasma membrane requires a conformational change in the I-II loop that is induced by binding of the CaV? subunit.

SUBMITTER: Page KM 

PROVIDER: S-EPMC5034038 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature