Molecular transitions regulating ryanodine receptor channel gating : potential target for therapeutic intervention in heart failure and arrhythmia

摘要

Previous work, on RyR1/2 modulation, assessing phosphorylation in relation to FKBP12/12.6 stabilisation of channel activity, indicates convergent regulation involving control of domain interaction sites by phosphorylation, FKBP12/12.6 and other modulators. This study used a central domain peptide (DP4WT) and its mutant form (DP4M) to investigate the relationship between FKBP12, phosphorylation, and other modulators to identify this region of convergent regulation. Native RyR1 channels, stripped or endogenous FKBP12 and phosphorylated or dephosphorylated, were shown, by [H]ryanodine binding, to be fully functional and to be activated by calcium and ATP. FKBP12 and magnesium were each shown to inhibit channel activity, and phosphorylation reversed magnesium inhibition. DP4WT peptide, synthesised from two sources, activated RyR1 2-fold in the presence of µM calcium, less than activity observed with ATP. Magnesium and FKBP12 inhibited RyR1 activation by DP4WT. In contrast to previous studies, DP4M was not an inactive control peptide. To investigate this discrepancy, recombinant GST-tagged (R-)DP4M and (R-)DP4WT were generated and neither showed an activatory effect. However, once cleaved of GST, the R-DP4WT was as potent as synthetic DP4WT at 10 µM. Experiments with RyR2 demonstrated similar results for calcium and ATP activation with inhibition by FKBP12.6. The RyR2 central domain peptide (DPc10) has been cloned and the protein produced.