Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10934353 | Developmental Biology | 2005 | 12 Pages |
Abstract
Expression of constitutively active Src protein tyrosine kinase in Xenopus oocytes has been shown to accelerate oocyte maturation suggesting that Src may be involved in meiotic progression. However, meiotic regulation of endogenous Src kinase in oocytes has not been investigated in detail. To address this problem, we measured the activity, expression level, and phosphorylation state of the endogenous Xenopus Src (xSrc) and overexpressed xSrc mutants in the process of progesterone-induced oocyte maturation. We found that the enzyme is first transiently activated in the plasma membrane-containing fraction of oocytes within 3 min of progesterone administration. This event represents one of the earliest responses of oocytes to the hormone and should be related to triggering some early signaling pathways of maturation. Thereafter, xSrc activity increases again at the time of germinal vesicle breakdown (GVBD) and remains elevated till the completion of maturation. This elevation of xSrc activity is associated with a 2-fold increase of xSrc protein content in the absence of change in its specific activity and xSrc mRNA content. No significant changes in the phosphorylation state of C-terminal regulatory phosphotyrosine can be registered either in endogenous xSrc or in overexpressed kinase-negative and wild-type xSrc proteins during maturation. Altogether, these results indicate that upregulation of xSrc in the meiotic metaphase occurs at the translation level. We also demonstrate here that the expression of constitutively active xSrc in Xenopus oocytes is accompanied by the activation of mitogen-activated protein kinase (MAPK). Our data suggest that the Src kinase acts through the MAPK pathway to accelerate oocyte maturation.
Keywords
PI3KSrc kinaseSFKRT-PCRPLCMPFpKaGVBDIP3inositol 1,4,5-trisphosphateSrc family kinaseMAPKMaturationmaturation-promoting factorgerminal vesicle breakdownoocytecytostatic factorPhosphatidylinositol 3-kinasephospholipase CXenopusCSFMeiosisreal-time polymerase chain reactionmitogen-activated protein kinasecAMP-dependent protein kinaseProgesterone receptor
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Authors
Alexander Tokmakov, Tetsushi Iwasaki, Shuji Itakura, Ken-Ichi Sato, Mikako Shirouzu, Yasuo Fukami, Shigeyuki Yokoyama,