Mos activates MAP kinase in mouse oocytes through two opposite pathways.
Activation of mitogen-activated protein kinase (MAPK) in maturing mouse oocytes occurs after synthesis of Mos, a MAPKKK. To investigate whether Mos acts only through MEK1, we microinjected constitutively active forms of MEK1 (MEK1S218D/S222D referred herein as MEK*) and Raf (DeltaRaf) into mouse oocytes. In mos(-/-) oocytes, which do not activate MAPK during meiosis and do not arrest in metaphase II, MEK* and DeltaRaf did not rescue MAPK activation and metaphase II arrest, whereas Mos induced a complete rescue. MEK* and DeltaRaf induced cleavage arrest of two-cell blastomeres. They induced MAPK activation when protein phosphatases were inhibited by okadaic acid, suggesting that Mos may inhibit protein phosphatases. Finally, in mos(-/-) oocytes, MEK* induced the phosphorylation of Xp42(mapk)D324N, a mutant less sensitive to dephosphorylation, showing that a MAPK phosphatase activity is present in mouse oocytes. We demonstrate that active MAPKK or MAPKKK cannot substitute for Mos to activate MAPK in mouse oocytes. We also show that a phosphatase activity inactivates MAPK, and that Mos can overcome this inhibitory activity. Thus Mos activates MAPK through two opposite pathways: activation of MEK1 and inhibition of a phosphatase.
Verlhac
M H
MH
Biologie Cellulaire et Moléculaire du Développement, UMR 7622, CNRS/Université Pierre et Marie Curie, 9 quai Saint Bernard-Bat. C-5, 75252 Paris, cedex 05, France.
Lefebvre
C
C
Kubiak
J Z
JZ
Umbhauer
M
M
Rassinier
P
P
Colledge
W
W
Maro
B
B
D000818:Animals; D004789:Enzyme Activation; D005260:Female; D015870:Gene Expression; D066298:In Vitro Techniques; D048369:MAP Kinase Kinase 1; D008540:Meiosis; D008677:Metaphase; D051379:Mice; D018345:Mice, Knockout; D008845:Microinjections; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009154:Mutation; D019319:Okadaic Acid / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D017231:Proto-Oncogene Proteins c-mos / Q000235:genetics* / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism; D011691:Puromycin / Q000494:pharmacology; D012333:RNA, Messenger / Q000008:administration & dosage / Q000235:genetics
D012333:RNA, Messenger; D019319:Okadaic Acid; D011691:Puromycin; D017346:Protein Serine-Threonine Kinases; D017231:Proto-Oncogene Proteins c-mos; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases