The proteasome is an essential mediator of the activation of pre-MPF during starfish oocyte maturation.
Starfish oocyte maturation was blocked by the addition of 100 microM MG115, a potent proteasome inhibitor, whereas no inhibition was observed by membrane permeable cysteine protease inhibitor, E-64-d. The inhibition by MG115 was diminished by adding at a time corresponding to the half time required for germinal vesicle breakdown. Potent inhibition of germinal vesicle breakdown was also observed by microinjection of anti-proteasome-a-subunit antibodies. The antibody-injected oocytes failed to activate pre-maturation promoting factor (pre-MPF), since the dephosphorylation of phospho-Tyr15 in cdc2 kinase was not observed even in the presence of 1-methyadenine, a maturation-inducing hormone. These results indicate that the proteasome triggers the activation of pre-MPF via the dephosphorylation of cdc2 kinase in the signal transduction pathway in response to the hormonal stimulus during starfish oocyte maturation.
Takagi Sawada
M
M
Bioscience and Chemistry Division, Hokkaido National Industrial Research Institute, MITI, Toyohira-ku, Sapporo, Japan.
Kyozuka
K
K
Morinaga
C
C
Izumi
K
K
Sawada
H
H
D000818:Animals; D002454:Cell Differentiation; D003546:Cysteine Endopeptidases / Q000502:physiology*; D005260:Female; D016200:Maturation-Promoting Factor / Q000502:physiology*; D009097:Multienzyme Complexes / Q000502:physiology*; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D046988:Proteasome Endopeptidase Complex; D011498:Protein Precursors / Q000502:physiology*; D015398:Signal Transduction; D013215:Starfish
D009097:Multienzyme Complexes; D011498:Protein Precursors; C067034:maturation-promoting factor precursor; D016200:Maturation-Promoting Factor; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex