Interaction between the Dihydropyridine Receptor Ca2+Channel$\beta-Subunit$and Ryanodine Receptor Type 1 Strengthens Excitation-Contraction Coupling

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 102; no. 52; pp. 19225 - 19230
• Main Authors: Weijun Cheng, Altafaj, Xavier, Ronjat, Michel, Coronado, Roberto
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 27.12.2005; National Acad Sciences
• Subjects: Amino Acid Sequence; Animals; Binding Sites; Biological Sciences; Bone and Bones; Bone and Bones - metabolism; Calcium; Calcium - chemistry; Calcium - metabolism; Calcium Channels; Calcium Channels - metabolism; Calcium Channels, L-Type; Calcium Channels, L-Type - chemistry; Caveolin 1; Caveolin 1 - chemistry; Cell membranes; Cells, Cultured; Cellular Biology; Complementary DNA; Depolarization; DNA, Complementary; DNA, Complementary - metabolism; Electric potential; Fluorescence; Gene expression; Glutathione Transferase; Glutathione Transferase - metabolism; Kinetics; Life Sciences; Mice; Microscopy, Confocal; Models, Genetic; Molecular Sequence Data; Muscle fibers; Muscle, Skeletal; Muscle, Skeletal - cytology; Muscles; Muscles - cytology; Muscles - pathology; Muscular system; Mutation; Patch-Clamp Techniques; Phenotype; Protein Binding; Protein Structure, Secondary; Protein Structure, Tertiary; Proteins; Receptors; Recombinant Proteins; Recombinant Proteins - chemistry; Ryanodine Receptor Calcium Release Channel; Ryanodine Receptor Calcium Release Channel - chemistry; Sarcoplasmic Reticulum; Sarcoplasmic Reticulum - metabolism; Sequence Homology, Amino Acid; Skeletal muscle; Structure-Activity Relationship; Thermodynamics; Transfection
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0504334102

Previous studies have shown that the skeletal dihydropyridine receptor (DHPR) pore subunit$Ca_v1.1 (\alpha1S)$physically interacts with ryanodine receptor type 1 (RyR1), and a molecular signal is transmitted from$\alpha 1S$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$\beta 1a-subunit$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 Ca2+transients coupled to voltage-dependent activation of the DHPR. Meantime the Ca2+content of the sarcoplasmic reticulum was not affected, and the amplitude and activation kinetics of the DHPR Ca2+currents were slightly affected. The data show that the DHPR$\beta-subunit$,$like \alpha 1S$, interacts directly with RyR1 and is critical for the generation of high-speed Ca2+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$alpha 1S$and$\beta 1a$, interacting with possibly different domains of RyR1.