Cardiac-specific phosphorylation site for multifunctional Ca2+/calmodulin-dependent protein kinase is conserved in the brain ryanodine receptor.

An antiserum raised against the region of the cardiac ryanodine receptor (residues 2805-2819) containing the phosphorylation site for multifunctional Ca2+/calmodulin-dependent protein kinase (CaM kinase) was used to identify the brain ryanodine receptor. This antiserum, which is cardiac isoform-specific, immunoprecipitated greater than 90% of the [3H]ryanodine receptor binding sites solubilized from guinea pig brain membranes. The immunoprecipitated brain receptor exhibited the characteristic cardiac-type mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The brain ryanodine receptor, like the cardiac ryanodine receptor, was a substrate for CaM kinase. Affinity-purified, site-specific antibodies completely blocked phosphorylation of both brain and cardiac receptors by CaM kinase, and two-dimensional peptide mapping identified the same major 32P-labeled peptide in receptors from both tissues. 125I-Labeled receptors also gave the same peptide maps. These results confirm that mammalian brain expresses the cardiac isoform of the ryanodine receptor. Furthermore, the unique CaM kinase phosphorylation site, which has been shown to regulate Ca2+ channel activity, is conserved.