Key result
Mutation of 6 of 16 N-glycosylation sites on the CaVα2δ1 subunit decreased protein stability and prevented the CaVα2δ1-mediated increase in peak current density of the CaV1.2 channel.
N-glycosylation of the CaVα2δ1 subunit at specific Asn residues is essential for the stability and functional surface expression of cardiac L-type Ca2+ channels.
May inform mechanistic studies of L-type remodeling; leaves open any role for CaVα2δ1 glycosylation in arrhythmia therapy.
Alteration in the L-type current density is one aspect of the electrical remodeling observed in patients suffering from cardiac arrhythmias. Changes in channel function could result from variations in the protein biogenesis, stability, post-translational modification, and/or trafficking in any of the regulatory subunits forming cardiac L-type Ca(2+) channel complexes. CaVα2δ1 is potentially the most heavily N-glycosylated subunit in the cardiac L-type CaV1.2 channel complex. Here, we show that enzymatic removal of N-glycans produced a 50-kDa shift in the mobility of cardiac and recombinant CaVα2δ1 proteins. This change was also observed upon simultaneous mutation of the 16 Asn sites. Nonetheless, the mutation of only 6/16 sites was sufficient to significantly 1) reduce the steady-state cell surface fluorescence of CaVα2δ1 as characterized by two-color flow cytometry assays and confocal imaging; 2) decrease protein stability estimated from cycloheximide chase assays; and 3) prevent the CaVα2δ1-mediated increase in the peak current density and voltage-dependent gating of CaV1.2. Reversing the N348Q and N812Q mutations in the non-operational sextuplet Asn mutant protein partially restored CaVα2δ1 function. Single mutation N663Q and double mutations N348Q/N468Q, N348Q/N812Q, and N468Q/N812Q decreased protein stability/synthesis and nearly abolished steady-state cell surface density of CaVα2δ1 as well as the CaVα2δ1-induced up-regulation of L-type currents. These results demonstrate that Asn-663 and to a lesser extent Asn-348, Asn-468, and Asn-812 contribute to protein stability/synthesis of CaVα2δ1, and furthermore that N-glycosylation of CaVα2δ1 is essential to produce functional L-type Ca(2+) channels.
No takes yet. Share an insight, caveat, or question.
Tétreault et al. (2016) studied cardiac arrhythmias. Mutation of N-glycosylation sites on CaVα2δ1 vs. Wild-type CaVα2δ1 was evaluated on Protein stability, cell surface density, and L-type Ca(2+) channel function. Mutation of 6 of 16 N-glycosylation sites on the CaVα2δ1 subunit decreased protein stability and prevented the CaVα2δ1-mediated increase in peak current density of the CaV1.2 channel.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: