title: Raptor ablation in skeletal muscle decreases Cav1.1 expression and affects the function of the excitation-contraction coupling supramolecular complex.
abstract: The protein mammalian target of rapamycin (mTOR) is a serine/threonine kinase regulating a number of biochemical pathways controlling cell growth. mTOR exists in two complexes termed mTORC1 and mTORC2. Regulatory associated protein of mTOR (raptor) is associated with mTORC1 and is essential for its function. Ablation of raptor in skeletal muscle results in several phenotypic changes including decreased life expectancy, increased glycogen deposits and alterations of the twitch kinetics of slow fibres. In the present paper, we show that in muscle-specific raptor knockout (RamKO), the bulk of glycogen phosphorylase (GP) is mainly associated in its cAMP-non-stimulated form with sarcoplasmic reticulum (SR) membranes. In addition, 3[H]-ryanodine and 3[H]-PN200-110 equilibrium binding show a ryanodine to dihydropyridine receptors (DHPRs) ratio of 0.79 and 1.35 for wild-type (WT) and raptor KO skeletal muscle membranes respectively. Peak amplitude and time to peak of the global calcium transients evoked by supramaximal field stimulation were not different between WT and raptor KO. However, the increase in the voltage sensor-uncoupled RyRs leads to an increase of both frequency and mass of elementary calcium release events (ECRE) induced by hyper-osmotic shock in flexor digitorum brevis (FDB) fibres from raptor KO. The present study shows that the protein composition and function of the molecular machinery involved in skeletal muscle excitation-contraction (E-C) coupling is affected by mTORC1 signalling.
authors.affiliation: *Departments of Anesthesia and of Biomedicine, Basel University Hospital, Hebelstrasse 20, 4031 Basel, Switzerland.
authors.forename: Rubén J
authors.initials: RJ
authors.lastname: Lopez
authors.affiliation: *Departments of Anesthesia and of Biomedicine, Basel University Hospital, Hebelstrasse 20, 4031 Basel, Switzerland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Mosca
authors.affiliation: *Departments of Anesthesia and of Biomedicine, Basel University Hospital, Hebelstrasse 20, 4031 Basel, Switzerland.
authors.forename: Susan
authors.initials: S
authors.lastname: Treves
authors.affiliation: *Departments of Anesthesia and of Biomedicine, Basel University Hospital, Hebelstrasse 20, 4031 Basel, Switzerland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Maj
authors.affiliation: †Department of Life Sciences, General Pathology section, University of Ferrara, Via Borsari 46, 44100 Ferrara, Italy.
authors.forename: Leda
authors.initials: L
authors.lastname: Bergamelli
authors.affiliation: ‡Laboratorio de Fisiología Celular, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas (IVIC), Apartado 20632, 1020A Caracas, Venezuela.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Calderon
authors.affiliation: §Biozentrum, University of Basel, CH-4056 Basel, Switzerland.
authors.forename: C Florian
authors.initials: CF
authors.lastname: Bentzinger
authors.affiliation: §Biozentrum, University of Basel, CH-4056 Basel, Switzerland.
authors.forename: Klaas
authors.initials: K
authors.lastname: Romanino
authors.affiliation: §Biozentrum, University of Basel, CH-4056 Basel, Switzerland.
authors.forename: Michael N
authors.initials: MN
authors.lastname: Hall
authors.affiliation: §Biozentrum, University of Basel, CH-4056 Basel, Switzerland.
authors.forename: Markus A
authors.initials: MA
authors.lastname: Rüegg
authors.affiliation: ║Department of Internal Medicine, Section on Gerontology and Geriatric Medicine, Wake Forest University School of Medicine, Winston-Salem, NC 27157, U.S.A.
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Delbono
authors.affiliation: ‡Laboratorio de Fisiología Celular, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas (IVIC), Apartado 20632, 1020A Caracas, Venezuela.
authors.forename: Carlo
authors.initials: C
authors.lastname: Caputo
authors.affiliation: *Departments of Anesthesia and of Biomedicine, Basel University Hospital, Hebelstrasse 20, 4031 Basel, Switzerland.
authors.forename: Francesco
authors.initials: F
authors.lastname: Zorzato
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000172:deficiency / Q000235:genetics*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000235:genetics* / Q000378:metabolism; D005071:Evoked Potentials / Q000502:physiology; D056966:Excitation Contraction Coupling / Q000502:physiology; D005786:Gene Expression Regulation; D024981:Glycogen Phosphorylase / Q000235:genetics / Q000378:metabolism; D007537:Isometric Contraction; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D018345:Mice, Knockout; D046912:Multiprotein Complexes / Q000235:genetics* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D000076223:Regulatory-Associated Protein of mTOR; D012433:Ryanodine / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C529218:CACNA1S protein, mouse; D020746:Calcium Channels, L-Type; D046912:Multiprotein Complexes; D000076223:Regulatory-Associated Protein of mTOR; C540162:Rptor protein, mouse; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D024981:Glycogen Phosphorylase; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D002118:Calcium