Characterization of the major brain form of the ryanodine receptor/Ca2+ release channel

At least three distinct ryanodine receptor genes appear to be expressed in mammalian brain. We have used biochemical and immunological methods to characterize the major form of ryanodine binding protein purified from brain. [3H]Ryanodine binding to the purified brain receptor is stimulated by Ca2+, ATP, KCl, and phosphorylation and is inhibited by calmodulin, Mg2+, and ruthenium red. Immunoblot and immunoprecipitation analysis using a panel of monoclonal and polyclonal antibodies against skeletal and cardiac muscle ryanodine receptors, and two novel polyclonal antibodies against the brain ryanodine receptor, reveals that the major form of ryanodine receptor expressed in brain is immunologically similar to the cardiac ryanodine receptor, but is distinct from the skeletal muscle receptor. Digestion of cardiac and brain ryanodine receptors with trypsin or alpha-chymotrypsin generates similar proteolytic patterns as detected by immunoblot analysis or by autoradiography after labeling with a hydrophobic probe, suggesting that the two proteins are similar in both their large cytoplasmic and hydrophobic transmembrane domains. Taken together, these data indicate that the cardiac ryanodine receptor/Ca2+ release channel is the major form of ryanodine receptor expressed in brain, and that it likely functions in releasing Ca2+ from caffeine-sensitive intracellular Ca2+ stores in neurons by a mechanism of regulated Ca(2+)-induced Ca2+ release.