title: Effects of conformational peptide probe DP4 on bidirectional signaling between DHPR and RyR1 calcium channels in voltage-clamped skeletal muscle fibers.
abstract: In skeletal muscle, excitation-contraction coupling involves the activation of dihydropyridine receptors (DHPR) and type-1 ryanodine receptors (RyR1) to produce depolarization-dependent sarcoplasmic reticulum Ca²⁺ release via orthograde signaling. Another form of DHPR-RyR1 communication is retrograde signaling, in which RyRs modulate the gating of DHPR. DP4 (domain peptide 4), is a peptide corresponding to residues Leu²⁴⁴²-Pro²⁴⁷⁷ of the central domain of the RyR1 that produces RyR1 channel destabilization. Here we explore the effects of DP4 on orthograde excitation-contraction coupling and retrograde RyR1-DHPR signaling in isolated murine muscle fibers. Intracellular dialysis of DP4 increased the peak amplitude of Ca²⁺ release during step depolarizations by 64% without affecting its voltage-dependence or kinetics, and also caused a similar increase in Ca²⁺ release during an action potential waveform. DP4 did not modify either the amplitude or the voltage-dependence of the intramembrane charge movement. However, DP4 augmented DHPR Ca²⁺ current density without affecting its voltage-dependence. Our results demonstrate that the conformational changes induced by DP4 regulate both orthograde E-C coupling and retrograde RyR1-DHPR signaling.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Rotimi O
authors.initials: RO
authors.lastname: Olojo
authors.forename: Erick O
authors.initials: EO
authors.lastname: Hernández-Ochoa
authors.forename: Noriaki
authors.initials: N
authors.lastname: Ikemoto
authors.forename: Martin F
authors.initials: MF
authors.lastname: Schneider
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000814:Aniline Compounds / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism; D003956:Dialysis; D005453:Fluorescence; D066298:In Vitro Techniques; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000378:metabolism*; D017711:Nonlinear Dynamics; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology*; D011487:Protein Conformation; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D014966:Xanthenes / Q000378:metabolism
chemical_list: D000814:Aniline Compounds; D020746:Calcium Channels, L-Type; C409648:Fluo 4; D010455:Peptides; D019837:Ryanodine Receptor Calcium Release Channel; D014966:Xanthenes; D002118:Calcium