The formation of skeletal muscle myotubes requires functional membrane receptors activated by extracellular ATP.
Skeletal muscle differentiation follows an organized sequence of events including commitment, cell cycle withdrawal, and cell fusion to form multinucleated myotubes. The role of adenosine 5'-triphosphate (ATP)-mediated signaling in differentiation of skeletal muscle myoblasts was evaluated in C(2)C(12) cells, a myoblast cell line. Cell differentiation was inhibited by P2X receptor blockers or by degradation of endogenous ATP with apyrase. However, pertussis toxin, known to block only a group of P2Y receptors, did not alter the differentiation process. Cells were heterogeneous in their expression of functional P2X receptors, evaluated by the uptake of fluorescent permeability tracers (Lucifer yellow and ethidium bromide), and by immunofluorescence of P2X(7) receptors. Moreover, xestospongin C, a selective and membrane-permeable inhibitor of IP(3) receptors, inhibited both myotube formation and myogenin expression. Based on these results, we suggest that the known increase in intracellular Ca(2+) concentration required for differentiation is due at least in part to Ca(2+) influx through P2X receptors and Ca(2+) release from intracellular stores. The possible involvement of P2X receptors and other pathways that might set the intracellular Ca(2+) at the level required for myoblast differentiation as well as the possible involvement of gap junction channels in the intercellular transfer of second messengers involved in coordinating myogenesis is proposed.
Araya
Roberto
R
Departamento de Ciencias Fisiológicas, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Alameda 340, Region Metropolitana, Santiago 114D, Chile. raraya@genes.bio.puc.cl
Riquelme
Manuel A
MA
Brandan
Enrique
E
Sáez
Juan C
JC
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D045604:Extracellular Fluid / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D018008:Myogenin / Q000096:biosynthesis / Q000187:drug effects; D058919:Purinergic P2 Receptor Antagonists; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058469:Receptors, Purinergic P2X; D058486:Receptors, Purinergic P2X7; D012508:Sarcolemma / Q000378:metabolism*
D015220:Calcium Channels; D005456:Fluorescent Dyes; D053496:Inositol 1,4,5-Trisphosphate Receptors; C503801:Myog protein, mouse; D018008:Myogenin; C546469:P2rx7 protein, mouse; D058919:Purinergic P2 Receptor Antagonists; D018160:Receptors, Cytoplasmic and Nuclear; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058486:Receptors, Purinergic P2X7; D000255:Adenosine Triphosphate; D002118:Calcium