Journal
MOLECULAR AND CELLULAR ENDOCRINOLOGY
Volume 374, Issue 1-2, Pages 46-55Publisher
ELSEVIER IRELAND LTD
DOI: 10.1016/j.mce.2013.04.007
Keywords
Insulin signalling; PI3K; Akt; Phosphodiesterase; Oocyte maturation; Zebrafish
Categories
Funding
- Department of Biotechnology [BT/29/NE/TBP/2010]
- University Grants Commission [39-681/2010 (SR)]
- INSPIRE Program, Department of Science and Technology, Govt. of India
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Exposure of fully grown oocytes to growth factors (insulin/IGFs) initiates various signalling cascades that culminate to final stages of oocyte maturation. Regulation of signalling pathways during growth factor-induced meiosis resumption in fish is not well characterized. Here we studied the participation of PI3K/Akt signalling pathway during recombinant human insulin (rh-insulin)-induced meiotic maturation in zebrafish (Danio rerio) oocytes. Priming of defolliculated oocytes in vitro with rh-insulin promotes germinal vesicle breakdown (GVBD) in a dose- and time-dependent manner, an effect sensitive to translation but not transcription inhibition. More than 80% of the oocytes underwent GVBD due to 0.8 IU/ml rh-insulin within 10 h of incubation and the kinetics of p34cdc2 kinase activation corresponded well with GVBD data. PI3K inhibitors, wortmannin and LY294002 blocked insulin, but not 17 alpha, 20 beta-DHP-induced GVBD. Immunoblot analyses of oocyte extract revealed that phospho-PI3K (p85 alpha) was up regulated within 30-60 min of insulin stimulation followed by phospho-Akt (Ser473) at 60-120 min. Though PI3K/Akt phosphorylation was largely unaffected, pre-incubation with phosphodiesterase (PDE) inhibitors, IBMX and cilostamide, but not rolipram completely blocked rh-insulin-induced p34cdc2 activation and GVBD. These results suggest that PDE3 may be one potential downstream target to PI3K/Akt signalling necessary for rh-insulin-induced GVBD in zebrafish. (c) 2013 Elsevier Ireland Ltd. All rights reserved.
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