Evidence for MAP kinase activation during mitotic division.
MAP kinases have been implicated in the control of a broad spectrum of cellular events in many types of cells. In somatic cells, MAP kinase activation seems to be triggered after exit from a quiescent state (in G0 or G2) only and then inactivated by entry into a proliferative state. In oocytes of various species, a one-time activation of MAP kinase that is apparently not repeated during the succeeding mitotic cycles occurs after meiotic activation. However, several reports suggest that a myelin basic protein (MBP) kinase activity, unrelated to that of maturation promoting factor, can sometimes be detected during mitotic divisions in various types of cells and oocytes. We have reinvestigated this problem in order to determine the origin and the role of MBP kinase that is stimulated at time of mitosis in the fertilized eggs of the sea urchin Paracentrotus lividus. We used anti-ERK1 antibodies or substrates specific for different MAP kinases, and performed in-gel phosphorylation experiments. Our results suggest that an ERK1-like protein was responsible for part of the MBP kinase activity that is stimulated during the first mitotic divisions. Furthermore, we observed that wortmannin, an inhibitor of PI 3-kinase that arrests the fertilized sea urchin eggs at the prometaphase stage, inhibited the inactivation of MAP kinase normally observed when the eggs divide, suggesting a role for PI 3-kinase in the deactivation process of MAP kinase. We also discuss how the activities of MPF and MAP kinase may be interconnected to regulate the first mitotic divisions of the early sea urchin embryo.
Chiri
S
S
Groupe de Recherche Sur l'Interaction Gamétique (GRIG), CJF 9504 INSERM, Faculté de Médecine, Avenue de Valombrose, Cedex 02 France.
De Nadai
C
C
Ciapa
B
B
D051698:Activating Transcription Factor 2; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism* / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3; D016350:Leucine Zippers; D016200:Maturation-Promoting Factor / Q000502:physiology; D008540:Meiosis / Q000187:drug effects; D008938:Mitosis / Q000502:physiology*; D004676:Myelin Basic Protein / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012617:Sea Urchins; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015053:Zygote / Q000166:cytology / Q000187:drug effects / Q000201:enzymology
D051698:Activating Transcription Factor 2; D017362:Cyclic AMP Response Element-Binding Protein; D004676:Myelin Basic Protein; D016755:Proto-Oncogene Proteins c-jun; D016271:Proto-Oncogene Proteins c-myc; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D005982:Glutathione Transferase; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D016200:Maturation-Promoting Factor; D038362:Glycogen Synthase Kinase 3