title: Oxidation of the skeletal muscle Ca2+ release channel alters calmodulin binding.
abstract: This study presents evidence for a close relationship between the oxidation state of the skeletal muscle Ca2+ release channel (RyR1) and its ability to bind calmodulin (CaM). CaM enhances the activity of RyR1 in low Ca2+ and inhibits its activity in high Ca2+. Oxidation, which activates the channel, blocks the binding of 125I-labeled CaM at both micromolar and nanomolar Ca2+ concentrations. Conversely, bound CaM slows oxidation-induced cross-linking between subunits of the RyR1 tetramer. Alkylation of hyperreactive sulfhydryls (<3% of the total sulfhydryls) on RyR1 with N-ethylmaleimide completely blocks oxidant-induced intersubunit cross-linking and inhibits Ca2+-free 125I-CaM but not Ca2+/125I-CaM binding. These studies suggest that 1) the sites on RyR1 for binding apocalmodulin have features distinct from those of the Ca2+/CaM site, 2) oxidation may alter the activity of RyR1 in part by altering its interaction with CaM, and 3) CaM may protect RyR1 from oxidative modifications during periods of oxidative stress.
authors.affiliation: Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: J Z
authors.initials: JZ
authors.lastname: Zhang
authors.forename: Y
authors.initials: Y
authors.lastname: Wu
authors.forename: B Y
authors.initials: BY
authors.lastname: Williams
authors.forename: G
authors.initials: G
authors.lastname: Rodney
authors.forename: F
authors.initials: F
authors.lastname: Mandel
authors.forename: G M
authors.initials: GM
authors.lastname: Strasburg
authors.forename: S L
authors.initials: SL
authors.lastname: Hamilton
mesh_terms: D000478:Alkylation; D000818:Animals; D002147:Calmodulin / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003958:Diamide / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D011817:Rabbits; D012433:Ryanodine / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D013439:Sulfhydryl Reagents / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D003432:Cross-Linking Reagents; D019837:Ryanodine Receptor Calcium Release Channel; D013439:Sulfhydryl Reagents; D003958:Diamide; D012433:Ryanodine; D005033:Ethylmaleimide