title: Myoplasmic resting Ca2+ regulation by ryanodine receptors is under the control of a novel Ca2+-binding region of the receptor.
abstract: Passive SR (sarcoplasmic reticulum) Ca2+ leak through the RyR (ryanodine receptor) plays a critical role in the mechanisms that regulate [Ca2+]rest (intracellular resting myoplasmic free Ca2+ concentration) in muscle. This process appears to be isoform-specific as expression of either RyR1 or RyR3 confers on myotubes different [Ca2+]rest. Using chimaeric RyR3-RyR1 receptors expressed in dyspedic myotubes, we show that isoform-dependent regulation of [Ca2+]rest is primarily defined by a small region of the receptor encompassing amino acids 3770-4007 of RyR1 (amino acids 3620-3859 of RyR3) named as the CLR (Ca2+ leak regulatory) region. [Ca2+]rest regulation by the CLR region was associated with alteration of RyRs' Ca2+-activation profile and changes in SR Ca2+-leak rates. Biochemical analysis using Tb3+-binding assays and intrinsic tryptophan fluorescence spectroscopy of purified CLR domains revealed that this determinant of RyRs holds a novel Ca2+-binding domain with conformational properties that are distinctive to each isoform. Our data suggest that the CLR region provides channels with unique functional properties that modulate the rate of passive SR Ca2+ leak and confer on RyR1 and RyR3 distinctive [Ca2+]rest regulatory properties. The identification of a new Ca2+-binding domain of RyRs with a key modulatory role in [Ca2+]rest regulation provides new insights into Ca2+-mediated regulation of RyRs.
authors.affiliation: *Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, NSC 552, Atlanta, GA 30303, U.S.A.
authors.forename: Yanyi
authors.initials: Y
authors.lastname: Chen
authors.affiliation: *Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, NSC 552, Atlanta, GA 30303, U.S.A.
authors.forename: Shenghui
authors.initials: S
authors.lastname: Xue
authors.affiliation: *Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, NSC 552, Atlanta, GA 30303, U.S.A.
authors.forename: Juan
authors.initials: J
authors.lastname: Zou
authors.affiliation: †Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, 1089 Veterinary Medicine Drive, Davis, CA 95616, U.S.A.
authors.forename: Jose R
authors.initials: JR
authors.lastname: Lopez
authors.affiliation: *Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, 50 Decatur Street, NSC 552, Atlanta, GA 30303, U.S.A.
authors.forename: Jenny J
authors.initials: JJ
authors.lastname: Yang
authors.affiliation: ‡Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, 20 Shattuck Street, Boston, MA 02115, U.S.A.
authors.forename: Claudio F
authors.initials: CF
authors.lastname: Perez
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018485:Muscle Fibers, Skeletal; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium