title: Triadin (Trisk 95) overexpression blocks excitation-contraction coupling in rat skeletal myotubes.
abstract: To identify the function of triadin in skeletal muscle, adenovirus-mediated overexpression of Trisk 95 or Trisk 51, the two major skeletal muscle isoforms, was induced in rat skeletal muscle primary cultures, and the physiological behavior of the modified cells was analyzed. Overexpression did not modify the expression level of their protein partners ryanodine receptor, dihydropyridine receptor, and the other triadin. Caffeine-induced calcium release was also unaffected by triadin overexpression. Nevertheless, in the absence of extracellular calcium, depolarization-induced calcium release was almost abolished in Trisk 95 overexpressing myotubes (T95 myotubes), and not modified in Trisk 51 overexpressing myotubes (T51 myotubes). This was not because of a modification of dihydropyridine receptors, as depolarization in presence of external calcium still induced a calcium release, and the activation curve of dihydropyridine receptor was unchanged, in both T95 and T51 myotubes. The calcium release complex was also maintained in T95 myotubes as Trisk 95, ryanodine receptor, dihydropyridine receptor, and Trisk 51 were still co-localized. The effect of Trisk 95 overexpression on depolarization-induced calcium release was reversed by a simultaneous infection with an antisense Trisk 95 adenovirus, indicating the specificity of this effect. Thus, the level of Trisk 95 and not Trisk 51 is important on regulating the calcium release complex, and an excess of this protein can lead to an inhibition of the physiological function of the complex.
authors.affiliation: INSERM U607, Laboratoire Canaux Calciques, Fonctions et Pathologies, CEA Grenoble, DRDC, 17 rue des Martyrs, F38054 Grenoble, France.
authors.forename: Sophia Smida
authors.initials: SS
authors.lastname: Rezgui
authors.forename: Stéphane
authors.initials: S
authors.lastname: Vassilopoulos
authors.forename: Julie
authors.initials: J
authors.lastname: Brocard
authors.forename: Jean Claude
authors.initials: JC
authors.lastname: Platel
authors.forename: Alexandre
authors.initials: A
authors.lastname: Bouron
authors.forename: Christophe
authors.initials: C
authors.lastname: Arnoult
authors.forename: Sarah
authors.initials: S
authors.lastname: Oddoux
authors.forename: Luis
authors.initials: L
authors.lastname: Garcia
authors.forename: Michel
authors.initials: M
authors.lastname: De Waard
authors.forename: Isabelle
authors.initials: I
authors.lastname: Marty
mesh_terms: D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling; D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology*; D002478:Cells, Cultured; D004594:Electrophysiology; D015870:Gene Expression; D047908:Intracellular Signaling Peptides and Proteins; D008564:Membrane Potentials; D046912:Multiprotein Complexes; D009119:Muscle Contraction / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D009124:Muscle Proteins / Q000235:genetics* / Q000502:physiology*; D051381:Rats; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D014162:Transfection
chemical_list: D020746:Calcium Channels, L-Type; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; C498271:Trdn protein, rat