IGF1 induces up-regulation of steroidogenic and apoptotic regulatory genes via activation of phosphatidylinositol-dependent kinase/AKT in bovine granulosa cells

Mani, Arul M.; Fenwick, Mark A.; Cheng, Zhangrui; Sharma, Mohan; Singh, Dheer; Wathes, D C

doi:10.1530/rep-09-0050

Cited by 141 publications

(83 citation statements)

References 68 publications

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“…Mechanism of PKA-enhanced IRS1 Y*MXM Phosphorylation by the IGF-1R-The well recognized synergy between FSH and IGF-1 at the level of gene expression (23,(31)(32)(33)(34)(35)(36)(37)(38) spearheaded our identification of the site of intersection between these two signaling pathways and, consequently, the mechanism by which FSH via PKA activates PI3K/AKT. Our results place IRS1 Y*MXM phosphorylation as a pivotal step in the activation of PI3K/AKT in GCs in response to FSH.…”

Section: Discussionmentioning

confidence: 99%

“…Exogenous IGF-1 alone (in the absence of FSH) also activates PI3K/AKT in GCs (3) but does not promote gene expression (23,32,33). However, numerous studies have reported that exogenous IGF-1 potentiates gene expression responses to FSH (23,(31)(32)(33)(34)(35)(36)(37)(38). IGF-1 does not alter the affinity of FSH for its receptor (37), suggesting an intracellular intersection of the two hormonal pathways downstream of the FSH receptor.…”

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confidence: 99%

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Insulin Receptor Substrate 1, the Hub Linking Follicle-stimulating Hormone to Phosphatidylinositol 3-Kinase Activation

Law

Hunzicker-Dunn

2016

Journal of Biological Chemistry

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The ubiquitous phosphatidylinositol 3-kinase (PI3K) signaling pathway regulates many cellular functions. However, the mechanism by which G protein-coupled receptors (GPCRs) signal to activate PI3K is poorly understood. We have used ovarian granulosa cells as a model to investigate this pathway, based on evidence that the GPCR agonist follicle-stimulating hormone (FSH) promotes the protein kinase A (PKA)-dependent phosphorylation of insulin receptor substrate 1 (IRS1) on tyrosine residues that activate PI3K. We report that in the absence of FSH, granulosa cells secrete a subthreshold concentration of insulin-like growth factor-1 (IGF-1) that primes the IGF-1 receptor (IGF-1R) but fails to promote tyrosine phosphorylation of IRS1. FSH via PKA acts to sensitize IRS1 to the tyrosine kinase activity of the IGF-1R by activating protein phosphatase 1 (PP1) to promote dephosphorylation of inhibitory Ser/Thr residues on IRS1, including Ser 789 . Knockdown of PP1␤ blocks the ability of FSH to activate PI3K in the presence of endogenous IGF-1. Activation of PI3K thus requires both PKA-mediated relief of IRS1 inhibition and IGF-1R-dependent tyrosine phosphorylation of IRS1. Treatment with FSH and increasing concentrations of exogenous IGF-1 triggers synergistic IRS1 tyrosine phosphorylation at PI3K-activating residues that persists downstream through protein kinase B (AKT) and FOXO1 (forkhead box protein O1) to drive synergistic expression of genes that underlies follicle maturation. Based on the ability of GPCR agonists to synergize with IGFs to enhance gene expression in other cell types, PP1 activation to relieve IRS1 inhibition may be a more general mechanism by which GPCRs act with the IGF-1R to activate PI3K/AKT.The phosphatidylinositol-3 kinase (PI3K) signaling pathway regulates transcription, translation, proliferation, and apoptosis (1, 2). Whereas PI3K is classically activated by receptor tyrosine kinases, such as the insulin-like growth factor-1 receptor (IGF-1R), 2 PI3K is also activated in many cells by G-proteincoupled receptors (GPCRs). However, the mechanisms by which GPCRs signal to activate PI3K are much less understood compared with classical activation by receptor tyrosine kinases (1). We have used rat ovarian granulosa cells (GCs) as a model to elucidate the mechanism by which the GPCR agonist folliclestimulating hormone (FSH) activates PI3K, based on prior evidence that FSH activates PI3K in a protein kinase A (PKA)-dependent manner (3). FSH is an obligatory regulator of ovarian follicle maturation. During the menstrual cycle, preantral follicles that encompass developing oocytes mature to a preovulatory stage in response to elevated levels of FSH (4). Administration of exogenous FSH also restores follicle development in anovulatory women (5). Finally, mice harboring null alleles for either the FSH receptor or FSH␤ lack preovulatory follicles and are infertile (6, 7). Traditionally, FSH has thus been considered both necessary and sufficient to promote follicle maturation.FSH acts exclusively on GCs wit...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Insulin Receptor Substrate 1, the Hub Linking Follicle-stimulating Hormone to Phosphatidylinositol 3-Kinase Activation

Law

Hunzicker-Dunn

2016

Journal of Biological Chemistry

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“…Therefore, to verify the involvement of the PI3K in the regulation of ovine primordial follicle activation in vitro, we tested the hypothesis that pharmacological inhibition of the PI3K pathway with LY294002 would inhibit the initiation of follicle growth. LY294002 has been used at different concentrations (from 1 μM to 50 μM) and incubation periods (from 20 min to 14 days) to inhibit the PI3K pathway in different ovarian cells (Reddy et al, 2009;Mani et al, 2010;Adhikari et al, 2013;Zhang et al, 2014;Fujihara et al, 2014;Lan et al, 2017). In this study, although the concentration of the inhibitor (50 µM LY294002) is higher than most of the other studies (Keating et al, 2009;Sobinoff et al, 2012;Zhang et al, 2014;Zhao et al, 2017), our findings support the idea that this concentration was not toxic because it did not reduce the percentage of normal follicles compared to the treatment without the inhibitor.…”

Section: Discussionmentioning

confidence: 99%

Blocking the PI3K pathway or the presence of high concentrations of EGF inhibits the spontaneous activation of ovine primordial follicles in vitro

Santos¹,

Santos²,

Menezes³

et al. 2017

Anim Reprod

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The aims of this study were to verify the effects of Epidermal Growth Factor (EGF) on the morphology, primordial follicle activation, growth and proliferation of granulosa cells of ovine follicles cultured in situ, as well as the effect of a PI3K inhibitor on the follicular activation. Ten ovine ovaries were divided into fragments, being one fixed for histological analysis (fresh control). The remaining fragments were cultured for 7 days in control medium (α-MEM + ) alone or supplemented with EGF (1, 10, 50, 100 or 200 ng/mL). Follicles were classified as normal or atretic, as primordial or growing, and the oocyte and follicle diameters were measured. PCNA immunohistochemistry was performed in the fresh control and in treatment that showed the best results for follicular activation. Pharmacologic inhibition of PI3K activity was performed through pretreatment in media added with 50 µM LY294002 for 1 h. The percentage of normal follicles decreased (P < 0.05) after 7 days of culture in all treatments compared to the fresh control. A significant reduction in the percentage of primordial follicles and an increase (P < 0.05) in the growing ones were observed in all treatments compared to fresh control. Furthermore, both the control medium and 1 ng/mL EGF promoted an increase (P < 0.05) in follicular activation compared to other EGF treatments. The PCNA-positive cells in the EGF treatment were higher (P < 0.05) than in fresh control and α-MEM + . Pretreatment of ovarian tissue with PI3K inhibitor significantly inhibited (P < 0.05) α-MEM + -stimulated primordial follicle activation, but had no effect on EGF-stimulated activation (P > 0.05). In conclusion, PI3K pathway mediates the in vitro spontaneous activation of sheep primordial follicles. Moreover, EGF may act indirectly on follicular activation by promoting granulosa cell proliferation at 1 ng/mL, and EGF inhibited follicle activation in concentrations similar or higher than 10 ng/mL.

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“…51 embryo development and is affected by the pubertal status of the female (Pawlak et al, 2015) and FSH levels, which maintain the expression of BAX and BCL2 genes in the granulosa cells (Mani et al, 2010).…”

Section: Effects Of Pi3k and Fsh On Steroidogenesis Viability And Emmentioning

confidence: 99%

Effects of PI3K and FSH on steroidogenesis, viability and embryo development of the cumulus–oocyte complex after in vitro culture

Souza

Salles

Camargo

et al. 2017

Zygote

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SummaryThe purpose of this study was to evaluate the effects of FSH and PI3K on the nuclear maturation, viability, steroidogenesis and embryo development of bovine cumulus-oocyte complexes (COCs). Oocyte maturation was achieved with MIV B, MIV B+100 µM LY294002, MIV B+10 ng/mL follicle stimulating hormone (FSH), or MIV B+10 ng/mL FSH+100 µM LY294002 treatments for 22-24 h. After the cultured COCs were denuded, oocytes were separated into those that extruded polar bodies (mature) and those that did not, and real-time polymerase chain reaction (PCR) for BAX, BCL2, LHR, FSHR, CYP11A1, CYP19A1 and HSD17B1 genes was performed. The culture medium was collected to determine the levels of 17β-estradiol (E2) and progesterone (P4). The trypan blue test was used to study COC viability, and embryo development was evaluated. FSH increased nuclear maturation and PI3K blocked the maturation but did not influence oocyte viability. BAX and BCL2 expression levels in the cumulus cells were only affected by FSH, and the BAX levels decreased after treatment with LY294002. FSH increased the levels of E2 and P4, however inhibition of PI3K decreased E2 levels. MIV B enhanced levels of LHR, FSHR, CYP11A1, CYP19A1 and HSD17B1, whereas LY294002 inhibited the expression levels of all genes. MIV B+FSH decreased the expression levels of all genes except CYP11A1. LY294002 did not demonstrate any effects in the presence of FSH. Embryo development was significantly decreased when the MIV B+FSH medium was used. In conclusion, FSH controls the steroidogenesis, viability and gene expression in COCs. PI3K plays essential roles in nuclear maturation, steroidogenesis and embryo development.

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IGF1 induces up-regulation of steroidogenic and apoptotic regulatory genes via activation of phosphatidylinositol-dependent kinase/AKT in bovine granulosa cells

Cited by 141 publications

References 68 publications

Insulin Receptor Substrate 1, the Hub Linking Follicle-stimulating Hormone to Phosphatidylinositol 3-Kinase Activation

Insulin Receptor Substrate 1, the Hub Linking Follicle-stimulating Hormone to Phosphatidylinositol 3-Kinase Activation

Blocking the PI3K pathway or the presence of high concentrations of EGF inhibits the spontaneous activation of ovine primordial follicles in vitro

Effects of PI3K and FSH on steroidogenesis, viability and embryo development of the cumulus–oocyte complex after in vitro culture

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