PI3-kinase and mitogen-activated protein kinase in cumulus cells mediate EGF-induced meiotic resumption of porcine oocyte.
Previous studies have shown that epidermal growth factor (EGF) has the ability to promote in vitro cultured porcine oocyte maturation. However, little is known about the detailed downstream events in EGF-induced meiotic resumption. We designed this study to determine the relationship of EGF, EGFR, phosphatidylinositol 3-kinase (PI3-kinase), MAPK, and germinal vesicle breakdown (GVBD) during oocyte maturation. Our results showed that GVBD in cumulus-enclosed oocytes (CEOs) but not in denuded oocytes (DOs) was induced by EGF in a dose-dependent manner, which indicated that cumulus cells but not oocyte itself were the main target for EGF-induced meiotic resumption. Furthermore, we found that MAPK in cumulus cells rather than in oocyte was activated immediately after EGF administration. To explore whether EGF exerts its functions through MAPK pathway, the activities of EGF receptor (EGFR) and MAPK were inhibited by employing AG1478 and U0126, respectively. Inhibition of MAPK blocked EGF-induced GVBD, whereas inhibition of EGFR prevented MAPK activation. Both AG1478 and U0126 could lead to the failure of EGF-induced GVBD singly. Notably, we found that LY294002, a specific inhibitor of PI3-kinase, effectively inhibited EGF-induced MAPK activation as well as subsequent oocyte meiotic resumption and this inhibition could not be reversed by adding additional EGF. Thus, PI3-kinase-induced MAPK activation in cumulus cells mediated EGF-induced meiotic resumption in porcine CEOs. Together, this study provides evidences demonstrating a linear relationship of EGF/EGFR, PI3-kinase, MAPK and GVBD and presents a relatively definitive mechanism of EGF-induced meiotic resumption of porcine oocyte.
Li
Mo
M
State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Da Tun Road, Chaoyang, Beijing 100101, PR China.
Liang
Cheng-Guang
CG
Xiong
Bo
B
Xu
Bao-Zeng
BZ
Lin
Sheng-Li
SL
Hou
Yi
Y
Chen
Da-Yuan
DY
Schatten
Heide
H
Sun
Qing-Yuan
QY
D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D054885:Cumulus Cells / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors; D005260:Female; D008540:Meiosis / Q000187:drug effects*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology*; D009025:Morpholines / Q000494:pharmacology; D009570:Nitriles / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D011799:Quinazolines; D013552:Swine / Q000378:metabolism / Q000502:physiology; D020032:Tyrphostins / Q000494:pharmacology
D002070:Butadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D009570:Nitriles; D011799:Quinazolines; D020032:Tyrphostins; C113580:U 0126; C101044:RTKI cpd; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D004815:Epidermal Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases