scholarly journals Wortmannin Inhibits Mitogen-activated Protein Kinase Activation by Platelet-activating Factor through a Mechanism Independent of p85/p110-type Phosphatidylinositol 3-Kinase

1996 ◽  
Vol 271 (20) ◽  
pp. 11684-11688 ◽  
Author(s):  
Ingvar M. Ferby ◽  
Iwao Waga ◽  
Mitsunobu Hoshino ◽  
Kazuhiko Kume ◽  
Takao Shimizu
Keyword(s):  
Protein Kinase ◽  
Platelet Activating Factor ◽  
Mitogen Activated Protein Kinase ◽  
Phosphatidylinositol 3 Kinase ◽  
Kinase Activation ◽  
Protein Kinase Activation ◽  
Mitogen Activated Protein ◽  
Phosphatidylinositol 3

scholarly journals 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

Zygote ◽  
2017 ◽  
Vol 26 (1) ◽  
pp. 62-75 ◽  
Author(s):  
Debabrata Das ◽  
Poulomi Nath ◽  
Soumojit Pal ◽  
Sudip Hajra ◽  
Pritha Ghosh ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Relative Importance ◽  
Phosphatidylinositol 3 Kinase ◽  
Kinase Activation ◽  
Erk Activation ◽  
Mapk Signalling ◽  
Mitogen Activated Protein ◽  
Phosphatidylinositol 3

SummaryParticipation 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.

Phosphatidylinositol 3-kinase activation is required for insulin stimulation of pp70 S6 kinase, DNA synthesis, and glucose transporter translocation

1994 ◽  
Vol 14 (7) ◽  
pp. 4902-4911
Author(s):  
B Cheatham ◽  
C J Vlahos ◽  
L Cheatham ◽  
L Wang ◽  
J Blenis ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Dna Synthesis ◽  
Mitogen Activated Protein Kinase ◽  
Phosphatidylinositol 3 Kinase ◽  
Insulin Stimulation ◽  
S6 Kinase ◽  
Kinase Activation ◽  
Mitogen Activated Protein ◽  
Stimulation Of ◽  
Phosphatidylinositol 3

Phosphatidylinositol 3-kinase (PI 3-kinase) is stimulated by insulin and a variety of growth factors, but its exact role in signal transduction remains unclear. We have used a novel, highly specific inhibitor of PT 3-kinase to dissect the role of this enzyme in insulin action. Treatment of intact 3T3-L1 adipocytes with LY294002 produced a dose-dependent inhibition of insulin-stimulated PI 3-kinase (50% inhibitory concentration, 6 microM) with > 95% reduction in the levels of phosphatidylinositol-3,4,5-trisphosphate without changes in the levels of phosphatidylinositol-4-monophosphate or its derivatives. In parallel, there was a complete inhibition of insulin-stimulated phosphorylation and activation of pp70 S6 kinase. Inhibition of PI 3-kinase also effectively blocked insulin- and serum-stimulated DNA synthesis and insulin-stimulated glucose uptake by inhibiting translocation of GLUT 4 glucose transporters to the plasma membrane. By contrast, LY294002 had no effect on insulin stimulation of mitogen-activated protein kinase or pp90 S6 kinase. Thus, activation of PI 3-kinase plays a critical role in mammalian cells and is required for activation of pp70 S6 kinase and DNA synthesis and certain forms of intracellular vesicular trafficking but not mitogen-activated protein kinase or pp90 S6 kinase activation. These data suggest that PI 3-kinase is not only an important component but also a point of divergence in the insulin signaling network.

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