title: The β(1a) subunit of the skeletal DHPR binds to skeletal RyR1 and activates the channel via its 35-residue C-terminal tail.
abstract: Although it has been suggested that the C-terminal tail of the β(1a) subunit of the skeletal dihyropyridine receptor (DHPR) may contribute to voltage-activated Ca(2+) release in skeletal muscle by interacting with the skeletal ryanodine receptor (RyR1), a direct functional interaction between the two proteins has not been demonstrated previously. Such an interaction is reported here. A peptide with the sequence of the C-terminal 35 residues of β(1a) bound to RyR1 in affinity chromatography. The full-length β(1a) subunit and the C-terminal peptide increased [(3)H]ryanodine binding and RyR1 channel activity with an AC(50) of 450-600 pM under optimal conditions. The effect of the peptide was dependent on cytoplasmic Ca(2+), ATP, and Mg(2+) concentrations. There was no effect of the peptide when channel activity was very low as a result of Mg(2+) inhibition or addition of 100 nM Ca(2+) (without ATP). Maximum increases were seen with 1-10 μM Ca(2+), in the absence of Mg(2+) inhibition. A control peptide with the C-terminal 35 residues in a scrambled sequence did not bind to RyR1 or alter [(3)H]ryanodine binding or channel activity. This high-affinity in vitro functional interaction between the C-terminal 35 residues of the DHPR β(1a) subunit and RyR1 may support an in vivo function of β(1a) during voltage-activated Ca(2+) release.
authors.affiliation: John Curtin School of Medical Research, Australian National University, Canberra, Australia.
authors.forename: Robyn T
authors.initials: RT
authors.lastname: Rebbeck
authors.forename: Yamuna
authors.initials: Y
authors.lastname: Karunasekara
authors.forename: Esther M
authors.initials: EM
authors.lastname: Gallant
authors.forename: Philip G
authors.initials: PG
authors.lastname: Board
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Beard
authors.forename: Marco G
authors.initials: MG
authors.lastname: Casarotto
authors.forename: Angela F
authors.initials: AF
authors.lastname: Dulhunty
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000737:chemistry* / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D021122:Protein Subunits / Q000378:metabolism*; D011817:Rabbits; D012433:Ryanodine / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D020746:Calcium Channels, L-Type; D021122:Protein Subunits; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002118:Calcium