A cell surface phosphoprotein of 48 kDa specific for myoblast fusion

• Published in: Cell differentiation Vol. 22; no. 3; pp. 245 - 258
• Main Authors: Lognonne, J.L., Wahrmann, J.P.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.1988; North-Holland
• Subjects: Animals; Biological and medical sciences; Calcium - pharmacology; Cell Cycle - drug effects; Cell differentiation, maturation, development, hematopoiesis; Cell Fusion; Cell Line; Cell Membrane - drug effects; Cell Membrane - physiology; Cell Membrane - ultrastructure; Cell physiology; Cell surface; Creatine Kinase - metabolism; Ectoprotein-kinase; Fundamental and applied biological sciences. Psychology; membrane proteins; Membrane Proteins - biosynthesis; Membrane Proteins - physiology; Molecular and cellular biology; Molecular Weight; Muscles - cytology; Muscles - embryology; Muscles - physiology; Myoblast fusion; myoblasts; Phosphoprotein; Phosphoproteins - biosynthesis; Phosphoproteins - physiology; Phosphorylation; Protein Kinases - metabolism; Rats; Myoblast fusion; Phosphoprotein; Ectoprotein-kinase; Cell surface; Cell culture; Phosphorylation; Membrane protein; Calcium; Rat; Rodentia; Cell fusion; Vertebrata; Regulation(control); Mammalia; Phosphoproteins; Myoblast
• ISSN: 0045-6039
• DOI: 10.1016/0045-6039(88)90016-4

The data we present here permit us to affirm that a 48 kDa phosphoprotein is the target of extracellular Ca 2+ during fusion. It is detected only in fusion-competent L 6 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 Ca 2+ 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 Ca 2+-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.