Role of protein kinase C in chick embryo skeletal myoblast fusion.
The involvement of Ca2+ and PGE1 in myoblast fusion has been well documented. Extracellular Ca2+ is essential for myoblast adhesion, alignment, and fusion. There is an obligatory increase in Ca2+ influx immediately preceding fusion and the Ca2+ ionophore A23187 promotes precocious fusion. PGE1 receptors appear just prior to fusion, and an antagonist of PGE1 binding to cell surface receptors blocks fusion when added prior to Ca2+ influx. Finally, exogenous PGE1 induces precocious fusion. The present study was an initial test of the hypothesis that membrane protein phosphorylation by protein kinase C (PKC) links PGE1 receptor occupancy and the increase in Ca2+ influx. Our conclusion that PKC is an essential component in the regulation of myoblast fusion is based in part on the following evidence: (1) an activator of PKC, the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), at low concentration and for a brief exposure period, induces precocious fusion and stimulates Ca2+ influx; (2) 4 alpha-phorbol-12,13-didecanoate, an inactive analog of TPA, has no discernible effect on fusion or Ca2+ influx; (3) 1-oleoyl-2-acetyl glycerol, an analog of endogenous diacylglycerol (DAG) which activates PKC, promotes precocious fusion, as does the DAG kinase inhibitor R59022 (6-[2-[4-[(4-fluorophenyl)phenylmethylene]-1-piperidinyl]ethyl]-7- methyl-5H-thiazole-[3,2 alpha]-pyrimidin-5-one) which raises the level of endogenous DAG by inhibiting its catabolism; (4) 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), a highly potent PKC inhibitor, reversibly blocks myogenesis at a point between alignment and fusion; and (5) H-7 also blocks the normal increase in Ca2+ influx preceding fusion.
David
J D
JD
Division of Biological Sciences, University of Missouri, Columbia 65211.
Faser
C R
CR
Perrot
G P
GP
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000527:Alprostadil / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002459:Cell Fusion / Q000187:drug effects; D002642:Chick Embryo; D004075:Diglycerides / Q000494:pharmacology; D004789:Enzyme Activation; D007546:Isoquinolines / Q000494:pharmacology; D009132:Muscles / Q000196:embryology*; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology*; D011494:Protein Kinases / Q000502:physiology; D011744:Pyrimidinones / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology
D004075:Diglycerides; D007546:Isoquinolines; D010879:Piperazines; D011744:Pyrimidinones; D013844:Thiazoles; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; C038237:1-oleoyl-2-acetylglycerol; C047505:R 59022; D011494:Protein Kinases; D011493:Protein Kinase C; D000527:Alprostadil; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium