Checking your SOCCs and feet: the molecular mechanisms of Ca2+ entry in skeletal muscle.
It has long been known that skeletal muscle contraction persists in the absence of extracellular Ca(2+). Nevertheless, recent evidence indicates that multiple distinct Ca(2+) entry pathways exist in skeletal muscle: one active at negative potentials that requires store depletion (store-operated calcium entry or SOCE) and a second that is independent of store depletion and is activated by depolarization (excitation-coupled calcium entry or ECCE). This review highlights recent findings regarding the molecular identity, subcellular localization, and inter-relationship between SOCE and ECCE in skeletal muscle. The respective roles of ryanodine receptors (RyRs), dihydropyridine receptors (DHPRs), inositol-1,4,5-trisphosphate receptors (IP(3)Rs), canonical transient receptor potential channels (TRPCs), STIM1 Ca(2+) sensor proteins, and Orai1 Ca(2+) permeable channels in mediating SOCE and ECCE in skeletal muscle are discussed. Differences between SOCE and ECCE in skeletal muscle with Ca(2+) entry mechanisms in non-excitable cells are also reviewed. Finally, potential physiological roles for SOCE and ECCE in skeletal muscle development and function, as well as other currently unanswered questions and controversies in the field are also considered.
Dirksen
Robert T
RT
Department of Pharmacology and Physiology, University of Rochester, NY 14642, USA. robert_dirksen@urmc.rochester.edu
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000737:chemistry / Q000378:metabolism; D000071740:ORAI1 Protein; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D000071737:Stromal Interaction Molecule 1; D013601:T-Lymphocytes / Q000378:metabolism
D015220:Calcium Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D019837:Ryanodine Receptor Calcium Release Channel; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D002118:Calcium