title: Interaction between the dihydropyridine receptor Ca2+ channel beta-subunit and ryanodine receptor type 1 strengthens excitation-contraction coupling.
abstract: Previous studies have shown that the skeletal dihydropyridine receptor (DHPR) pore subunit Ca(V)1.1 (alpha1S) physically interacts with ryanodine receptor type 1 (RyR1), and a molecular signal is transmitted from alpha1S to RyR1 to trigger excitation-contraction (EC) coupling. We show that the beta-subunit of the skeletal DHPR also binds RyR1 and participates in this signaling process. A novel binding site for the DHPR beta1a-subunit was mapped to the M(3201) to W(3661) region of RyR1. In vitro binding experiments showed that the strength of the interaction is controlled by K(3495)KKRR_ _R(3502), a cluster of positively charged residues. Phenotypic expression of skeletal-type EC coupling by RyR1 with mutations in the K(3495)KKRR_ _R(3502) cluster was evaluated in dyspedic myotubes. The results indicated that charge neutralization or deletion severely depressed the magnitude of RyR1-mediated Ca(2+) transients coupled to voltage-dependent activation of the DHPR. Meantime the Ca(2+) content of the sarcoplasmic reticulum was not affected, and the amplitude and activation kinetics of the DHPR Ca(2+) currents were slightly affected. The data show that the DHPR beta-subunit, like alpha1S, interacts directly with RyR1 and is critical for the generation of high-speed Ca(2+) signals coupled to membrane depolarization. These findings indicate that EC coupling in skeletal muscle involves the interplay of at least two subunits of the DHPR, namely alpha1S and beta1a, interacting with possibly different domains of RyR1.
authors.affiliation: Department of Physiology, University of Wisconsin School of Medicine, Madison, WI 53706, USA.
authors.forename: Weijun
authors.initials: W
authors.lastname: Cheng
authors.forename: Xavier
authors.initials: X
authors.lastname: Altafaj
authors.forename: Michel
authors.initials: M
authors.lastname: Ronjat
authors.forename: Roberto
authors.initials: R
authors.lastname: Coronado
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001842:Bone and Bones / Q000378:metabolism; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000737:chemistry*; D051242:Caveolin 1 / Q000737:chemistry; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D018613:Microscopy, Confocal; D008957:Models, Genetic; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000166:cytology; D009132:Muscles / Q000166:cytology / Q000473:pathology; D009154:Mutation; D018408:Patch-Clamp Techniques; D010641:Phenotype; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014162:Transfection
chemical_list: D015220:Calcium Channels; D020746:Calcium Channels, L-Type; C495541:Cav1 protein, mouse; D051242:Caveolin 1; D018076:DNA, Complementary; D011994:Recombinant Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D005982:Glutathione Transferase; D002118:Calcium