A cell surface phosphoprotein of 48 kDa specific for myoblast fusion.
The data we present here permit us to affirm that a 48 kDa phosphoprotein is the target of extracellular Ca2+ during fusion. It is detected only in fusion-competent L6 myoblasts and not in the fusion-defective spontaneous stable variants we isolated. The phosphorylation of this protein species can be totally inhibited by culturing myoblasts in a medium containing low Ca2+ concentrations (0.250 mM). However, under such conditions myoblasts do not fuse, but withdraw from the cell cycle and accumulate the muscle isoform of creatine kinase (M-CK). The results we have obtained support the following conclusions: (1) in fusion-competent cells, overall Ca2+-dependent phosphorylation of cell surface proteins appears to be necessary, but is not sufficient by itself for myoblast fusion; (2) the phosphorylation of a 48 kDa protein species is required for cell fusion; and (3) the phosphorylation of this 48 kDa protein is independent of other main events of cellular differentiation.
Lognonne
J L
JL
INSERM U 15, Institut de Pathologie Moléculaire, Paris, France.
Wahrmann
J P
JP
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D002459:Cell Fusion; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D003402:Creatine Kinase / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis / Q000502:physiology*; D008970:Molecular Weight; D009132:Muscles / Q000166:cytology* / Q000196:embryology / Q000502:physiology; D010750:Phosphoproteins / Q000096:biosynthesis / Q000502:physiology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats
D008565:Membrane Proteins; D010750:Phosphoproteins; D011494:Protein Kinases; C034454:ectoprotein kinase; D003402:Creatine Kinase; D002118:Calcium