title: RyR1 deficiency in congenital myopathies disrupts excitation-contraction coupling.
abstract: In skeletal muscle, excitation-contraction (EC) coupling is the process whereby the voltage-gated dihydropyridine receptor (DHPR) located on the transverse tubules activates calcium release from the sarcoplasmic reticulum by activating ryanodine receptor (RyR1) Ca(2+) channels located on the terminal cisternae. This subcellular membrane specialization is necessary for proper intracellular signaling and any alterations in its architecture may lead to neuromuscular disorders. In this study, we present evidence that patients with recessive RYR1-related congenital myopathies due to primary RyR1 deficiency also exhibit downregulation of the alfa 1 subunit of the DHPR and show disruption of the spatial organization of the EC coupling machinery. We created a cellular RyR1 knockdown model using immortalized human myoblasts transfected with RyR1 siRNA and confirm that knocking down RyR1 concomitantly downregulates not only the DHPR but also the expression of other proteins involved in EC coupling. Unexpectedly, this was paralleled by the upregulation of inositol-1,4,5-triphosphate receptors; functionally however, upregulation of the latter Ca(2+) channels did not compensate for the lack of RyR1-mediated Ca(2+) release. These results indicate that in some patients, RyR1 deficiency concomitantly alters the expression pattern of several proteins involved in calcium homeostasis and that this may influence the manifestation of these diseases.
authors.affiliation: Dubowitz Neuromuscular Centre, Institute of Child Health, University College London, London, UK.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Zhou
authors.forename: Ori
authors.initials: O
authors.lastname: Rokach
authors.forename: Lucy
authors.initials: L
authors.lastname: Feng
authors.forename: Iulia
authors.initials: I
authors.lastname: Munteanu
authors.forename: Kamel
authors.initials: K
authors.lastname: Mamchaoui
authors.forename: Jo M
authors.initials: JM
authors.lastname: Wilmshurst
authors.forename: Caroline
authors.initials: C
authors.lastname: Sewry
authors.forename: Adnan Y
authors.initials: AY
authors.lastname: Manzur
authors.forename: Komala
authors.initials: K
authors.lastname: Pillay
authors.forename: Vincent
authors.initials: V
authors.lastname: Mouly
authors.forename: Michael
authors.initials: M
authors.lastname: Duchen
authors.forename: Heinz
authors.initials: H
authors.lastname: Jungbluth
authors.forename: Susan
authors.initials: S
authors.lastname: Treves
authors.forename: Francesco
authors.initials: F
authors.lastname: Muntoni
mesh_terms: D001706:Biopsy; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D056966:Excitation Contraction Coupling / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D009135:Muscular Diseases / Q000151:congenital / Q000503:physiopathology*; D009154:Mutation; D032446:Myoblasts / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D020746:Calcium Channels, L-Type; D053496:Inositol 1,4,5-Trisphosphate Receptors; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium