Amino acid residues 489-503 of dihydropyridine receptor (DHPR) β1a subunit are critical for structural communication between the skeletal muscle DHPR complex and type 1 ryanodine receptor.
The β1a subunit is a cytoplasmic component of the dihydropyridine receptor (DHPR) complex that plays an essential role in skeletal muscle excitation-contraction (EC) coupling. Here we investigate the role of the C-terminal end of this auxiliary subunit in the functional and structural communication between the DHPR and the Ca(2+) release channel (RyR1). Progressive truncation of the β1a C terminus showed that deletion of amino acid residues Gln(489) to Trp(503) resulted in a loss of depolarization-induced Ca(2+) release, a severe reduction of L-type Ca(2+) currents, and a lack of tetrad formation as evaluated by freeze-fracture analysis. However, deletion of this domain did not affect expression/targeting or density (Qmax) of the DHPR-α1S subunit to the plasma membrane. Within this motif, triple alanine substitution of residues Leu(496), Leu(500), and Trp(503), which are thought to mediate direct β1a-RyR1 interactions, weakened EC coupling but did not replicate the truncated phenotype. Therefore, these data demonstrate that an amino acid segment encompassing sequence (489)QVQVLTSLRRNLSFW(503) of β1a contains critical determinant(s) for the physical link of DHPR and RyR1, further confirming a direct correspondence between DHPR positioning and DHPR/RyR functional interactions. In addition, our data strongly suggest that the motif Leu(496)-Leu(500)-Trp(503) within the β1a C-terminal tail plays a nonessential role in the bidirectional DHPR/RyR1 signaling that supports skeletal-type EC coupling.
the Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virgina 23298, and.
Jose M
JM
Eltit
the Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
Clara
C
Franzini-Armstrong
From the Department of Anesthesiology Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, cperez@zeus.bwh.harvard.edu.
Claudio F
CF
Perez
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002478:Cells, Cultured; D056966:Excitation Contraction Coupling; D057927:Hydrophobic and Hydrophilic Interactions; D008564:Membrane Potentials; D051379:Mice; D008969:Molecular Sequence Data; D021122:Protein Subunits; D021381:Protein Transport; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*
C492923:Cacnb1 protein, mouse; D020746:Calcium Channels, L-Type; D021122:Protein Subunits; D019837:Ryanodine Receptor Calcium Release Channel
Ca2+ Current; Ca2+ Release; Calcium Intracellular Release; Charge Movement; Patch Clamp; Retrograde Signaling; Ryanodine Receptor; Signal Transduction; Skeletal Muscle; Tetrad Array