Ca 2+ ATPase Phospholamban, Sarcolipin Brody Disease Cardiomyopathy Ca2+ Release Channel Publications MH/CCD Ca2+ Binding Proteins OMIM RYR1						Calcium Release Channels (Ryanodine Receptors) The Ca2+ release channel is a homotetrameric complex constructed from a 565,000 Da subunit. Transmembrane sequences, located in the COOH-terminal fifth of each subunit, combine to form the transmembrane portion of the Ca2+ release channel and the remainder of the subunit is cytoplasmic, bridging the gap between the sarcoplasmic reticulum and the transverse tubule. Single channel measurements in planar bilayers have shown that Ca2+ release is mediated by a ligand-gated channel with a conductance greater than 100 pS in 50 mM Ca2+. Although it is likely that physical interactions with the dihydropyridine receptor open the channel in the muscle cell, Ca2+ and ATP act synergistically to open the channel in isolated vesicles and Mg2+ and calmodulin inhibit channel opening. Our initial approach to the understanding of structure-function relationships in the Ca2+ release channel involved cloning of cDNAs encoding skeletal (RYR1) and cardiac (RYR2) isoforms and making predictions about structure-function relationships from the primary sequence of these 565,000 Da proteins. These predictions are now being tested in a number of ways: we expressed RYR1 cDNA encoding the rabbit skeletal muscle ryanodine receptor and characterized its function by single channel recordings in planar lipid bilayers; we identified seven proteolytic cleavage sites in the molecule that may delineate functional domains; we expressed fragments of the ryanodine receptor sequence as fusion proteins and carried out direct measurement of Ca2+ and calmodulin binding to them, leading to the assignment of several sites in the molecule where Ca2+ or calmodulin may bind and to evidence for colocalization of some Ca2+ and calmodulin binding sites within the same domain. Our most recent approach is to express the full length cDNA encoding the protein in HEK-293 cells and assay wild type and mutated function by the photometric measurement of Ca2+ release in whole cells.
Ca 2+ ATPase Phospholamban, Sarcolipin Brody Disease Cardiomyopathy Ca2+ Release Channel Top of Page MH/CCD Ca2+ Binding Proteins OMIM RYR1						Ryanodine Receptor Publications Leong, P. and MacLennan, D.H. (1998) A 37 amino acid sequence in the skeletal muscle ryanodine receptor interacts with the cytoplasmic loop between domains II and III in the skeletal muscle dihydropyridine receptor. Journal of Biological Chemistry (in press) Tong, J., Oyamada, H., Demaurex, N., Grinstein, S., McCarthy, T.V. and MacLennan, D.H. (1997) Caffeine and halothane sensitivity of intracellular Ca2+ release is altered by 15 calcium release channel (ryanodine receptor) mutations associated with malignant hyperthermia and/or central core disease. J Biol Chem 272(42):26332-9 Chen, S.R., Leong, P., Imredy, J.P., Bartlett, C., Zhang, L. and MacLennan, D.H. (1997) Single-channel properties of the recombinant skeletal muscle Ca2+ release channel (ryanodine receptor). Biophys J 73(4):1904-12 Chen, S.R., Zhang, L. and MacLennan, D.H. (1994) Asymmetrical blockade of the Ca2+ release channel (ryanodine receptor) by 12-kDa FK506 binding protein. Proceedings of the National Academy of Sciences of the United States of America 91(25):11953-7 Chen, S.R. and MacLennan, D.H. (1994) Identification of calmodulin-, Ca(2+)-, and ruthenium red-binding domains in the Ca2+ release channel (ryanodine receptor) of rabbit skeletal muscle sarcoplasmic reticulum. Journal of Biological Chemistry 269(36):22698-704 MacLennan, D.H. and Chen, S.R.W. (1993) The role of the calcium release channel of skeletal muscle sarcoplasmic reticulum in malignant hyperthermia. Ann N.Y. Acad Sci 707294-304 Chen, S.R., Airey, J.A. and MacLennan, D.H. (1993) Positioning of major tryptic fragments in the Ca2+ release channel (ryanodine receptor) resulting from partial digestion of rabbit skeletal muscle sarcoplasmic reticulum. Journal of Biological Chemistry 268(30):22642-9 Chen, S.R., Zhang, L. and MacLennan, D.H. (1993) Antibodies as probes for Ca2+ activation sites in the Ca2+ release channel (ryanodine receptor) of rabbit skeletal muscle sarcoplasmic reticulum. Journal of Biological Chemistry 268(18):13414-21 Chen, S.R., Vaughan, D.M., Airey, J.A., Coronado, R. and MacLennan, D.H. (1993) Functional expression of cDNA encoding the Ca2+ release channel (ryanodine receptor) of rabbit skeletal muscle sarcoplasmic reticulum in COS-1 cells. Biochemistry 32(14):3743-53 Chen, S.R., Zhang, L. and MacLennan, D.H. (1992) Characterization of a Ca2+ binding and regulatory site in the Ca2+ release channel (ryanodine receptor) of rabbit skeletal muscle sarcoplasmic reticulum. Journal of Biological Chemistry 267(32):23318-26 Otsu, K., Willard, H.F., Khanna, V.K., Zorzato, F., Green, N.M. and MacLennan, D.H. (1990) Molecular cloning of cDNA encoding the Ca2+ release channel (ryanodine receptor) of rabbit cardiac muscle sarcoplasmic reticulum. Journal of Biological Chemistry 265(23):13472-83 Zorzato, F., Fujii, J., Otsu, K., Phillips, M., Green, N.M., Lai, F.A., Meissner, G. and MacLennan, D.H. (1990) Molecular cloning of cDNA encoding human and rabbit forms of the Ca2+ release channel (ryanodine receptor) of skeletal muscle sarcoplasmic reticulum. Journal of Biological Chemistry 265(4):2244-56 Shoshan, V., MacLennan, D.H. and Wood, D.S. (1983) Tetraphenylboron causes Ca2+ release in isolated sarcoplasmic reticulum and in skinned muscle fibers. Journal of Biological Chemistry 258(5):2837-42 Shoshan, V., MacLennan, D.H. and Wood, D.S. (1981) A proton gradient controls a calcium-release channel in sarcoplasmic reticulum. Proceedings of the National Academy of Sciences of the United States of America 78(8):4828-32 Shoshan, V., Campbell, K.P., MacLennan, D.H., Frodis, W. and Britt, B.A. (1980) Quercetin inhibits Ca2+ uptake but not Ca2+ release by sarcoplasmic reticulum in skinned muscle fibers. Proceedings of the National Academy of Sciences of the United States of America 77(8):4435-8
Ca2+ Release Channel Top of Page Publications Revised 1998Apr09