Relative importance of phosphatidylinositol-3 kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK3/1) signaling during maturational steroid-induced meiotic G2–M1 transition in zebrafish oocytes. Issue 1 (12th December 2017)

• Record Type: Journal Article
• Authors: Das, Debabrata; Nath, Poulomi; Pal, Soumojit; Hajra, Sudip; Ghosh, Pritha; Maitra, Sudipta
• Is Part Of: Zygote. Volume 26:Issue 1(2018)
• Page Start: 62
• Page End: 75
• Publication Date: 2017-12-12
• Subjects: GVBD, -- Oocyte, -- Meiosis, -- PKA, -- Zebrafish; Developmental biology -- Periodicals; Embryology -- Periodicals; Zygotes -- Periodicals; Gametes -- Periodicals; 571.864
• DOI: 10.1017/S0967199417000545
• Languages: English
• ISSNs: 0967-1994

Abstract

Summary: Participation and relative importance of phosphatidylinositol-3 kinase (PI3K) and mitogen-activated protein kinase (MAPK) signalling, either alone or in combination, have been investigated during 17α, 20β-dihydroxy-4-pregnen-3-one (DHP)-induced meiotic G2−M1 transition in denuded zebrafish oocyte. Results demonstrate that concomitant with rapid phosphorylation (activation) of Akt (Ser473) and MAPK (ERK1/2) at as early as 15 min of incubation, DHP stimulation promotes enhanced an GVBD response and histone H1 kinase activation between 1 and 5 h in full-grown oocytes in vitro . While p-Akt reaches its peak at 60 to 90 min and undergoes downregulation to the basal level by 240 min, ERK1/2 phosphorylation (activation) increases gradually until 120 min and remains high thereafter. Although, priming with MEK1/2 inhibitor U0126 is without effect, PI3K inhibitors, wortmannin or LY294002, delay the GVBD response significantly ( P < 0.001) until 3 h but not at 5 h of incubation. Interestingly, blocking PI3K and MEK function together could abrogate steroid-induced oocyte maturation at all time points tested. While DHP stimulation promotes phospho-PKA catalytic (p-PKAc) dephosphorylation (inactivation) between 30–120 min of incubation, simultaneous inhibition of PI3K and MEK1/2 kinases abrogates DHP action. Conversely, elevated intra-oocyte cAMP, through priming with either adenylyl cyclase (AC) activator forskolin (FK) or dibutyryl cAMP (db-cAMP), abrogates steroid-induced Akt and ERK1/2 phosphorylation. Taken together, these results suggest that DHP-induced Akt and ERK activation precedes the onset of meiosis (GVBD response) in a cAMP-sensitive manner and PI3K/Akt and MEK/MAPK pathways together have a pivotal influence in the downregulation of PKA and resumption of meiotic maturation in zebrafish oocytes in vitro .