title: IP3 receptors and associated Ca2+ signals localize to satellite cells and to components of the neuromuscular junction in skeletal muscle.
abstract: Recently, we described an inositol 1,4,5-trisphosphate (IP3) signaling system in cultured rodent skeletal muscle, triggered by high K+ and affecting gene transcription (Powell et al., 2001). Now, in a study of adult rodent skeletal muscle, using immunocytology and confocal microscopy, we have found a high level of IP3 receptor (IP3R) staining in satellite cells, which have been shown recently to contribute to nuclei in adult fibers after muscle exercise. These IP3R staining cells are positively identified as satellite cells by their position, morphology and staining with satellite-cell-specific antibodies such as desmin and neural cell adhesion molecule. IP3Rs are also localized to postsynaptic components of the neuromuscular junction (NMJ), in areas surrounding the nuclei of the motor end plate, and in perisynaptic Schwann cells, and localized close to nicotinic acetylcholine receptors of the endplate gutters. Ca2+ imaging experiments show calcium release at the motor endplate upon K+ depolarization precisely in these IP3R-rich regions. We suggest that electrical activity stimulates IP3-associated Ca2+ signals that may be involved in gene regulation in satellite cells and in elements of the NMJ, contributing both to muscle fiber growth and stabilization of the NMJ.
authors.affiliation: Department of Biological Sciences, Smith College, Northampton, Massachusetts 01063, USA.
authors.forename: Jeanne A
authors.initials: JA
authors.lastname: Powell
authors.forename: Jordi
authors.initials: J
authors.lastname: Molgó
authors.forename: Dany S
authors.initials: DS
authors.lastname: Adams
authors.forename: Cesare
authors.initials: C
authors.lastname: Colasante
authors.forename: Aislinn
authors.initials: A
authors.lastname: Williams
authors.forename: MacKenzie
authors.initials: M
authors.lastname: Bohlen
authors.forename: Enrique
authors.initials: E
authors.lastname: Jaimovich
mesh_terms: D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D003964:Diaphragm / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005456:Fluorescent Dyes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D051379:Mice; D008815:Mice, Inbred Strains; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000648:ultrastructure; D019006:Neural Cell Adhesion Molecules / Q000096:biosynthesis; D009469:Neuromuscular Junction / Q000378:metabolism* / Q000648:ultrastructure; D011188:Potassium / Q000494:pharmacology; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000378:metabolism; D032496:Satellite Cells, Skeletal Muscle / Q000166:cytology / Q000378:metabolism*; D012583:Schwann Cells / Q000166:cytology / Q000378:metabolism; D014966:Xanthenes
chemical_list: D000814:Aniline Compounds; D015220:Calcium Channels; C073804:FM1 43; D005456:Fluorescent Dyes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D019006:Neural Cell Adhesion Molecules; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D018160:Receptors, Cytoplasmic and Nuclear; D011978:Receptors, Nicotinic; D014966:Xanthenes; C059715:Fluo-3; D011188:Potassium; D002118:Calcium