title: Isoproterenol Promotes Rapid Ryanodine Receptor Movement to Bridging Integrator 1 (BIN1)-Organized Dyads.
abstract: BACKGROUND
  The key pathophysiology of human acquired heart failure is impaired calcium transient, which is initiated at dyads consisting of ryanodine receptors (RyRs) at sarcoplasmic reticulum apposing CaV1.2 channels at t-tubules. Sympathetic tone regulates myocardial calcium transients through β-adrenergic receptor (β-AR)-mediated phosphorylation of dyadic proteins. Phosphorylated RyRs (P-RyR) have increased calcium sensitivity and open probability, amplifying calcium transient at a cost of receptor instability. Given that bridging integrator 1 (BIN1) organizes t-tubule microfolds and facilitates CaV1.2 delivery, we explored whether β-AR-regulated RyRs are also affected by BIN1.
  
  
  RESULTS
  Isolated adult mouse hearts or cardiomyocytes were perfused for 5 minutes with the β-AR agonist isoproterenol (1 µmol/L) or the blockers CGP+ICI (baseline). Using biochemistry and superresolution fluorescent imaging, we identified that BIN1 clusters P-RyR and CaV1.2. Acute β-AR activation increases coimmunoprecipitation between P-RyR and cardiac spliced BIN1+13+17 (with exons 13 and 17). Isoproterenol redistributes BIN1 to t-tubules, recruiting P-RyRs and improving the calcium transient. In cardiac-specific Bin1 heterozygote mice, isoproterenol fails to concentrate BIN1 to t-tubules, impairing P-RyR recruitment. The resultant accumulation of uncoupled P-RyRs increases the incidence of spontaneous calcium release. In human hearts with end-stage ischemic cardiomyopathy, we find that BIN1 is also 50% reduced, with diminished P-RyR association with BIN1.
  
  
  CONCLUSIONS
  On β-AR activation, reorganization of BIN1-induced microdomains recruits P-RyR into dyads, increasing the calcium transient while preserving electric stability. When BIN1 is reduced as in human acquired heart failure, acute stress impairs microdomain formation, limiting contractility and promoting arrhythmias.
authors.affiliation: From Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (Y.F., S.A.S., R.N., C.L.V., W.A.B., T.H.); Institute for Translational Genomics and Population Sciences, Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA (X.G.); and Departments of Medicine, Cedars-Sinai Medical Center and UCLA, Los Angeles, CA (T.H.).
authors.forename: Ying
authors.initials: Y
authors.lastname: Fu
authors.affiliation: From Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (Y.F., S.A.S., R.N., C.L.V., W.A.B., T.H.); Institute for Translational Genomics and Population Sciences, Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA (X.G.); and Departments of Medicine, Cedars-Sinai Medical Center and UCLA, Los Angeles, CA (T.H.).
authors.forename: Seiji A
authors.initials: SA
authors.lastname: Shaw
authors.affiliation: From Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (Y.F., S.A.S., R.N., C.L.V., W.A.B., T.H.); Institute for Translational Genomics and Population Sciences, Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA (X.G.); and Departments of Medicine, Cedars-Sinai Medical Center and UCLA, Los Angeles, CA (T.H.).
authors.forename: Robert
authors.initials: R
authors.lastname: Naami
authors.affiliation: From Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (Y.F., S.A.S., R.N., C.L.V., W.A.B., T.H.); Institute for Translational Genomics and Population Sciences, Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA (X.G.); and Departments of Medicine, Cedars-Sinai Medical Center and UCLA, Los Angeles, CA (T.H.).
authors.forename: Caresse L
authors.initials: CL
authors.lastname: Vuong
authors.affiliation: From Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (Y.F., S.A.S., R.N., C.L.V., W.A.B., T.H.); Institute for Translational Genomics and Population Sciences, Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA (X.G.); and Departments of Medicine, Cedars-Sinai Medical Center and UCLA, Los Angeles, CA (T.H.).
authors.forename: Wassim A
authors.initials: WA
authors.lastname: Basheer
authors.affiliation: From Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (Y.F., S.A.S., R.N., C.L.V., W.A.B., T.H.); Institute for Translational Genomics and Population Sciences, Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA (X.G.); and Departments of Medicine, Cedars-Sinai Medical Center and UCLA, Los Angeles, CA (T.H.).
authors.forename: Xiuqing
authors.initials: X
authors.lastname: Guo
authors.affiliation: From Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (Y.F., S.A.S., R.N., C.L.V., W.A.B., T.H.); Institute for Translational Genomics and Population Sciences, Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA (X.G.); and Departments of Medicine, Cedars-Sinai Medical Center and UCLA, Los Angeles, CA (T.H.). tingting.hong@cshs.org.
authors.forename: TingTing
authors.initials: T
authors.lastname: Hong
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000172:deficiency / Q000378:metabolism*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000172:deficiency / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000318:Adrenergic beta-Agonists; C109221:Bin1 protein, mouse; D009419:Nerve Tissue Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D025521:Tumor Suppressor Proteins; D007545:Isoproterenol
keywords: BIN1 protein; heart failure; membrane microdomain; myocytes cardiac; receptors, adrenergic, beta; ryanodine receptor 2, mouse