Skeletal muscle IP3R1 receptors amplify physiological and pathological synaptic calcium signals.
Ca(2+) release from internal stores is critical for mediating both normal and pathological intracellular Ca(2+) signaling. Recent studies suggest that the inositol 1,4,5-triphosphate (IP(3)) receptor mediates Ca(2+) release from internal stores upon cholinergic activation of the neuromuscular junction (NMJ) in both physiological and pathological conditions. Here, we report that the type I IP(3) receptor (IP(3)R(1))-mediated Ca(2+) release plays a crucial role in synaptic gene expression, development, and neuromuscular transmission, as well as mediating degeneration during excessive cholinergic activation. We found that IP(3)R(1)-mediated Ca(2+) release plays a key role in early development of the NMJ, homeostatic regulation of neuromuscular transmission, and synaptic gene expression. Reducing IP(3)R(1)-mediated Ca(2+) release via siRNA knockdown or IP(3)R blockers in C2C12 cells decreased calpain activity and prevented agonist-induced acetylcholine receptor (AChR) cluster dispersal. In fully developed NMJ in adult muscle, IP(3)R(1) knockdown or blockade effectively increased synaptic strength at presynaptic and postsynaptic sites by increasing both quantal release and expression of AChR subunits and other NMJ-specific genes in a pattern resembling muscle denervation. Moreover, in two mouse models of cholinergic overactivity and NMJ Ca(2+) overload, anti-cholinesterase toxicity and the slow-channel myasthenic syndrome (SCS), IP(3)R(1) knockdown eliminated NMJ Ca(2+) overload, pathological activation of calpain and caspase proteases, and markers of DNA damage at subsynaptic nuclei, and improved both neuromuscular transmission and clinical measures of motor function. Thus, blockade or genetic silencing of muscle IP(3)R(1) may be an effective and well tolerated therapeutic strategy in SCS and other conditions of excitotoxicity or Ca(2+) overload.
Department of Neurology, University of Chicago Medical Center, Chicago, Illinois 60637, USA.
Haipeng
H
Zhu
Bula J
BJ
Bhattacharyya
Hong
H
Lin
Christopher M
CM
Gomez
D000200:Action Potentials / Q000187:drug effects / Q000235:genetics; D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000235:genetics / Q000502:physiology*; D002154:Calpain / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002461:Cell Line, Transformed; D018679:Cholinergic Agonists / Q000494:pharmacology; D002800:Cholinesterase Inhibitors / Q000633:toxicity; D004195:Disease Models, Animal; D004576:Electromyography; D018274:Electroporation / Q000379:methods; D005080:Exercise Test; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics; D006655:Histone Deacetylases / Q000378:metabolism; D006657:Histones / Q000235:genetics / Q000378:metabolism; D066298:In Vitro Techniques; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000172:deficiency / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D018482:Muscle, Skeletal / Q000378:metabolism*; D020294:Myasthenic Syndromes, Congenital / Q000235:genetics / Q000473:pathology* / Q000628:therapy; D009388:Neostigmine / Q000633:toxicity; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009469:Neuromuscular Junction / Q000378:metabolism / Q000502:physiology*; D020258:Neurotoxicity Syndromes / Q000209:etiology / Q000473:pathology* / Q000628:therapy; D018408:Patch-Clamp Techniques; D034741:RNA, Small Interfering / Q000494:pharmacology; D011950:Receptors, Cholinergic / Q000145:classification / Q000235:genetics / Q000378:metabolism; D012584:Sciatic Nerve / Q000503:physiopathology; D013997:Time Factors
D001896:Boron Compounds; D002118:Calcium; D002154:Calpain; D002217:Carbachol; D053148:Caspase 3; D053453:Caspase 9; D018679:Cholinergic Agonists; D002800:Cholinesterase Inhibitors; D049452:Green Fluorescent Proteins; D006655:Histone Deacetylases; D006657:Histones; D053496:Inositol 1,4,5-Trisphosphate Receptors; D009388:Neostigmine; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; D011950:Receptors, Cholinergic; C109986:2-aminoethoxydiphenyl borate; C498618:Hdac5 protein, mouse; C475961:gamma-H2AX protein, mouse