Modification of Cardiac Ryanodine Receptor Gating by a Peptide from the Central Domain of the RyR2

Abstract

The effect of a domain peptide DPCPVTc from the central region of the RYR2 on ryanodine receptors isolated from rat heart was examined in planar lipid bilayers. At a zero holding potential and at 100 nM cytosolic and 8 mM luminal Ca2+ concentration, DPCPVTc induced concentration-dependent activation of the ryanodine receptor that led up to 20-fold increase of open probability at saturating DPCPVTc concentrations. The effect of the peptide appeared within 30 s after addition to the experimental chamber. At all DPCPVTc concentrations RyR2 channels displayed large variability in open probability, open time and opening frequency. DPCPVTc prolonged RyR2 openings up to 8× and increased RyR2 opening frequency by up to 100%. With increasing DPCPVTc concentration, the fraction of high open probability records increased up to 5×, and their open time increased up to 4×. The closed times did not depend on DPCPVTc concentration either in low- or high-open probability records. The DPCPVTc concentration dependence of all gating parameters had EC50 of 20 µM and a Hill slope of 2. Comparison of the effects of DPCPVTc with those of ATP [1] and cytosolic Ca2+ [2] suggests that activation does not involve luminal feed-through and is not caused by modulation of the cytosolic activation A-site. The data suggest that although “domain unzipping” by DPCPVTc occurs in both modes of RyR activity, it affects RyR gating only when the channel resides in the H-mode of activity.Supported in part by the European Union Contract No. LSHM-CT-2005-018802/CONTICA and by grants APVV-LPP-0441-09, APVV-0628-10 and VEGA 2/0197/11.[1] Tencerova B, Zahradnikova A, Gaburjakova J, Gaburjakova M. J Gen Physiol 140: 93, 2012.[2] Gaburjakova J, Gaburjakova M. J Membr Biol 212: 17, 2006.