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) Ca2+ 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 Ca2+ channels did not compensate for the lack of RyR1-mediated Ca2+ 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. We provide evidence in this study that RyR1 deficiency caused by mutations in RYR1 gene is responsible for the collapse of excitation-contraction coupling by disrupting the physi-ological colocalization of the dihydropyridine receptor and ryanodine receptor in skeletal muscle. The upregulation of an alternative calcium regulating system via IP3R is identifi-ed in the condition of RyR1 deficiency and in-dicates the possible existence of a complex interplay on RyR1 and IP3R signalling cascade in the pathophysiology of RYR1-related conge-nital myopathies. © 2013 WILEY PERIODICALS, INC.
RyR1 Deficiency in Congenital Myopathies Disrupts Excitation-Contraction Coupling
TREVES, Susan Nella;
2013
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) Ca2+ 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 Ca2+ channels did not compensate for the lack of RyR1-mediated Ca2+ 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. We provide evidence in this study that RyR1 deficiency caused by mutations in RYR1 gene is responsible for the collapse of excitation-contraction coupling by disrupting the physi-ological colocalization of the dihydropyridine receptor and ryanodine receptor in skeletal muscle. The upregulation of an alternative calcium regulating system via IP3R is identifi-ed in the condition of RyR1 deficiency and in-dicates the possible existence of a complex interplay on RyR1 and IP3R signalling cascade in the pathophysiology of RYR1-related conge-nital myopathies. © 2013 WILEY PERIODICALS, INC.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
