The β1a Subunit of the Skeletal DHPR Binds to Skeletal RyR1 and Activates the Channel via Its 35-Residue C-Terminal Tail

• Published in: Biophysical journal Vol. 100; no. 4; pp. 922 - 930
• Main Authors: Rebbeck, Robyn T., Karunasekara, Yamuna, Gallant, Esther M., Board, Philip G., Beard, Nicole A., Casarotto, Marco G., Dulhunty, Angela F.
• Format: Journal Article
• Language: English
• Published: The Biophysical Society 16-02-2011
• Subjects: Channels and Transporters
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1016/j.bpj.2011.01.022

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
μ
M 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.