Two domains in dihydropyridine receptor activate the skeletal muscle Ca(2+) release channel.
The II-III cytoplasmic loop of the skeletal muscle dihydropyridine receptor (DHPR) alpha(1)-subunit is essential for skeletal-type excitation-contraction coupling. Single channel and [(3)H]ryanodine binding studies with a full-length recombinant peptide (p(666-791)) confirmed that this region specifically activates skeletal muscle Ca2+ release channels (CRCs). However, attempts to identify shorter domains of the II-III loop specific for skeletal CRC activation have yielded contradictory results. We assessed the specificity of the interaction of five truncated II-III loop peptides by comparing their effects on skeletal and cardiac CRCs in lipid bilayer experiments; p(671-680) and p(720-765) specifically activated the submaximally Ca2+-activated skeletal CRC in experiments using both mono and divalent ions as current carriers. A third peptide, p(671-690), showed a bimodal activation/inactivation behavior indicating a high-affinity activating and low-affinity inactivating binding site. Two other peptides (p(681-690) and p(681-685)) that contained an RKRRK-motif and have previously been suggested in in vitro studies to be important for skeletal-type E-C coupling, failed to specifically stimulate skeletal CRCs. Noteworthy, p(671-690), p(681-690), and p(681-685) induced similar subconductances and long-lasting channel closings in skeletal and cardiac CRCs, indicating that these peptides interact in an isoform-independent manner with the CRCs.
Stange
M
M
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260, USA.
Tripathy
A
A
Meissner
G
G
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D020033:Protein Isoforms / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011817:Rabbits; D012433:Ryanodine / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D013379:Substrate Specificity
D020746:Calcium Channels, L-Type; D008051:Lipid Bilayers; D010446:Peptide Fragments; D020033:Protein Isoforms; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002118:Calcium