The alpha1S N-terminus is not essential for bi-directional coupling with RyR1.
The dihydropyridine receptor (DHPR) alpha(1S) II-III loop has been shown to be critical for excitation-contraction (EC) coupling in skeletal muscle, but the importance of other cytoplasmic regions, especially the N-terminus (residues 1-51), remains unclear. In this study, we found that deletion of alpha(1S) residues 2-37 (weakly conserved with N-termini of other L-type Ca(2+) channels) had little effect on the ability of alpha(1S) to serve as a Ca(2+) channel or voltage sensor for EC coupling. Strikingly, deletion of 10 additional residues, which are conserved in L-type channels, resulted in ablation of DHPR function. Specifically, confocal microscopy and measurement of charge movement showed that removal of residues 2-47 resulted in a failure of sarcolemmal insertion. Our results indicate that the weakly conserved, distal alpha(1S) N-terminus is not critical for EC coupling or function as a Ca(2+) channel. However, integrity of the proximal alpha(1S) N-terminus is necessary for sarcolemmal expression of the DHPR.
Bannister
R A
RA
Department of Biomedical Sciences, Neurosciences Division, Colorado State University, Fort Collins, CO 80523, USA.
Beam
K G
KG
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002478:Cells, Cultured; D051379:Mice; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D020746:Calcium Channels, L-Type; D019837:Ryanodine Receptor Calcium Release Channel