title: Conformation-dependent stability of junctophilin 1 (JP1) and ryanodine receptor type 1 (RyR1) channel complex is mediated by their hyper-reactive thiols.
abstract: Junctophilin 1 (JP1), a 72-kDa protein localized at the skeletal muscle triad, is essential for stabilizing the close apposition of T-tubule and sarcoplasmic reticulum membranes to form junctions. In this study we report that rapid and selective labeling of hyper-reactive thiols found in both JP1 and ryanodine receptor type 1 (RyR1) with 7-diethylamino-3-(4'-maleimidylphenyl)-4-methylcoumarin, a fluorescent thiol-reactive probe, proceeded 12-fold faster under conditions that minimize RyR1 gating (e.g. 10 mM Mg2+) compared with conditions that promote high channel activity (e.g. 100 microM Ca2+, 10 mM caffeine, 5 mM ATP). The reactivity of these thiol groups was very sensitive to oxidation by naphthoquinone, H2O2, NO, or O2, all known modulators of the RyR1 channel complex. Using preparative SDS-PAGE, in-gel tryptic digestion, high pressure liquid chromatography, and mass spectrometry-based peptide sequencing, we identified 7-diethylamino-3-(4'-maleimidylphenyl)-4-methylcoumarin-thioether adducts on three cysteine residues of JP1 (101, 402, and 627); the remaining five cysteines of JP1 were unlabeled. Co-immunoprecipitation experiments demonstrated a physical interaction between JP1 and RyR1 that, like thiol reactivity, was sensitive to RyR1 conformation and chemical status of the hyper-reactive cysteines of JP1 and RyR1. These findings support a model in which JP1 interacts with the RyR1 channel complex in a conformationally sensitive manner and may contribute integral redox-sensing properties through reactive sulfhydryl chemistry.
authors.affiliation: Department of Veterinary Molecular Biosciences and Center for Children's Environmental Health and Disease Prevention, University of California, Davis, California 95616, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Phimister
authors.forename: Jozsef
authors.initials: J
authors.lastname: Lango
authors.forename: Eun Hui
authors.initials: EH
authors.lastname: Lee
authors.forename: Michael A
authors.initials: MA
authors.lastname: Ernst-Russell
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takeshima
authors.forename: Jianjie
authors.initials: J
authors.lastname: Ma
authors.forename: Paul D
authors.initials: PD
authors.lastname: Allen
authors.forename: Isaac N
authors.initials: IN
authors.lastname: Pessah
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry; D008274:Magnesium / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D008956:Models, Chemical; D010084:Oxidation-Reduction; D011485:Protein Binding; D011487:Protein Conformation; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry* / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D014357:Trypsin / Q000737:chemistry
chemical_list: D008565:Membrane Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D013438:Sulfhydryl Compounds; C412507:junctophilin; D002110:Caffeine; D014357:Trypsin; D008274:Magnesium; D003545:Cysteine; D002118:Calcium