[Beta]1a490-508, a 19-Residue Peptide from C-Terminal Tail of Cav1.1 [Beta]1a Subunit, Potentiates Voltage-Dependent Calcium Release in Adult Skeletal Muscle Fibers

• Published in: Biophysical journal 2014-02, Vol.106 (3), p.535
• Main Authors: Hernández-Ochoa, Erick O, Olojo, Rotimi O, Rebbeck, Robyn T, Dulhunty, Angela F, Schneider, Martin F
• Format: Article
• Language: English
• Subjects: Biophysics; Calcium; Fibers; Musculoskeletal system; Peptides
• ISSN: 0006-3495; 1542-0086

The α1 and β1a subunits of the skeletal muscle calcium channel, Cav1.1, as well as the Ca^sup 2+^ release channel, ryanodine receptor (RyR1), are essential for excitation-contraction coupling. RyR1 channel activity is modulated by the β1a subunit and this effect can be mimicked by a peptide (β1a490-524) corresponding to the 35-residue C-terminal tail of the β1a subunit. Protein-protein interaction assays confirmed a high-affinity interaction between the C-terminal tail of the β1a and RyR1. Based on previous results using overlapping peptides tested on isolated RyR1, we hypothesized that a 19-amino-acid residue peptide (β1a490-508) is sufficient to reproduce activating effects of β1a490-524. Here we examined the effects of β1a490-508 on Ca^sup 2+^ release and Ca^sup 2+^ currents in adult skeletal muscle fibers subjected to voltage-clamp and on RyR1 channel activity after incorporating sarcoplasmic reticulum vesicles into lipid bilayers. β1a490-508 (25 nM) increased the peak Ca^sup 2+^ release flux by 49% in muscle fibers. Considerably fewer activating effects were observed using 6.25, 100, and 400 nM of β1a490-508 in fibers. β1a490-508 also increased RyR1 channel activity in bilayers and Cav1.1 currents in fibers. A scrambled form of β1a490-508 peptide was used as negative control and produced negligible effects on Ca^sup 2+^ release flux and RyR1 activity. Our results show that the β1a490-508 peptide contains molecular components sufficient to modulate excitation-contraction coupling in adult muscle fibers. [PUBLICATION ABSTRACT]