Protein Methylation Activates Reconstituted Ryanodine Receptor-Ca²⁺ Release Channels from Coronary Artery Myocytes

Ryanodine receptors (RyR) play an important role in the regulation of intracellular Ca²⁺ concentration and in the control of vascular tone. However, the mechanism regulating the activity of RyR is poorly understood. The present study determined whether protein methylation participates in the control of RyR activity. Using a planar lipid bilayer clamping system, S-adenosyl-<i>L</i>-methionine (SAM), a methyl donor, significantly increased the activity of a 245-pS reconstituted Ca²⁺ release channel from coronary arterial smooth muscle (CASM) in a concentration-dependent manner. Addition of the protein methylation blockers, 3-deazaadenosine, S-adenosylhomocysteine or sinefungin into the <i>cis</i> solution markedly attenuated SAM-induced activation of RyR/Ca²⁺ release channels. By Western blot analysis, arginine N-methyltransferase (PRMT1) and FK506 binding protein (FKBP) were detected in the SR used for reconstitution of RyR. In the presence of anti-PRMT1 antibody (1:100), SAM-induced activation of RyR/Ca²⁺ channel was completely abolished. In addition, this SAM-induced increase in RyR/Ca²⁺ channel activity was blocked by 30 µ<i>M</i> ryanodine and by FK506 (100 µ<i>M</i>), a ligand for the RyR accessory protein. These results suggest that protein methylation activates RyR/Ca²⁺ release channels and may participate in the control of intracellular Ca²⁺ mobilization in CASM cells by transferring a methyl group to the arginine moiety of the RyR accessory protein, FKBP 12.