title: Participation of PI3-kinase/Akt signalling in insulin stimulation of p34cdc2 activation in zebrafish oocyte: phosphodiesterase 3 as a potential downstream target.
abstract: 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 0.8IU/ml rh-insulin within 10h of incubation and the kinetics of p34cdc2 kinase activation corresponded well with GVBD data. PI3K inhibitors, wortmannin and LY294002 blocked insulin, but not 17α, 20β-DHP-induced GVBD. Immunoblot analyses of oocyte extract revealed that phospho-PI3K (p85α) 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.
authors.affiliation: Department of Zoology, Visva-Bharati, Santiniketan 731 235, India.
authors.forename: Debabrata
authors.initials: D
authors.lastname: Das
authors.forename: Pragya Paramita
authors.initials: PP
authors.lastname: Khan
authors.forename: Sudipta
authors.initials: S
authors.lastname: Maitra
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002867:Chromones / Q000494:pharmacology; D018844:Cyclin-Dependent Kinases / Q000235:genetics* / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D006908:Hydroxyprogesterones / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008540:Meiosis / Q000187:drug effects / Q000235:genetics; D009025:Morpholines / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D058539:Phosphatidylinositol 3-Kinase / Q000235:genetics* / Q000378:metabolism; D058987:Phosphodiesterase 3 Inhibitors / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics* / Q000378:metabolism; D015363:Quinolones / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D000077191:Wortmannin; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism*; D000095043:Cyclin-Dependent Kinase-Activating Kinase
chemical_list: D000730:Androstadienes; D002867:Chromones; D006908:Hydroxyprogesterones; D007328:Insulin; D007527:Isoenzymes; D009025:Morpholines; D058987:Phosphodiesterase 3 Inhibitors; D015363:Quinolones; D011994:Recombinant Proteins; C007433:17,20-dihydroxy-4-pregnen-3-one; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C021294:cilostamide; D058539:Phosphatidylinositol 3-Kinase; D051057:Proto-Oncogene Proteins c-akt; D018844:Cyclin-Dependent Kinases; D010727:Phosphoric Diester Hydrolases; D015056:1-Methyl-3-isobutylxanthine; D000077191:Wortmannin; D000095043:Cyclin-Dependent Kinase-Activating Kinase