MAP kinase cascade, but not ERKs, activated during early cleavage of mouse embryos.
Mitosis in early embryos is independent of exogenous mitogens, although mitogen stimulations and subsequent activation of a mitogen-activated protein (MAP) kinase cascade are essential for the proliferation of somatic cells. The activation state of the MAP kinase cascade during early cleavage has never been reported. In the present study, factors involved in the MAP kinase cascade--Ras, Raf-1, 14-3-3, MEK, and ERKs--and their activation states were detected by immunoblotting during early cleavage of mouse embryos. We found the constant presence of these molecules in mouse early embryos and the activation of Raf-1 exclusively at the M-phase. An immunoprecipitation study revealed that active Raf-1 in the M-phase was dissociated from 14-3-3, as in somatic cells, whereas inactive Raf-1 was associated with 14-3-3. Surprisingly, the ERKs (MAP kinases) were not activated throughout early cleavage, although M-phase-specific activation of the MAP kinase kinase, MEK was observed. Myelin basic protein kinase activity was, however, significantly higher in the M-phase than in the interphase. These results indicate that the MAP kinase cascade is activated at the M-phase and that some MAP kinases other than ERKs are activated during early cleavage of mouse embryos.
Haraguchi
S
S
Department of Reproductive and Developmental Biology, Institute of Medical Science, University of Tokyo, Japan.
Naito
K
K
Sato
E
E
D048948:14-3-3 Proteins; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000166:cytology / Q000201:enzymology*; D005314:Embryonic and Fetal Development; D004789:Enzyme Activation; D005260:Female; D038362:Glycogen Synthase Kinase 3; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D008297:Male; D051379:Mice; D008806:Mice, Inbred AKR; D008813:Mice, Inbred ICR; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D008938:Mitosis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase; D018631:ras Proteins / Q000378:metabolism
D048948:14-3-3 Proteins; D011506:Proteins; D014446:Tyrosine 3-Monooxygenase; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D038362:Glycogen Synthase Kinase 3; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; D018631:ras Proteins