Role of the Phosphatidylinositol-3-Kinase and Extracellular Regulated Kinase Pathways in the Induction of Hypoxia-Inducible Factor (HIF)-1 Activity and the HIF-1 Target Vascular Endothelial Growth Factor in Ovarian Granulosa Cells in Response to Follicle-Stimulating Hormone

Abstract

FSH stimulation of granulosa cells (GCs) results in increased hypoxia-inducible factor (HIF)-1alpha protein levels and HIF-1 activity that is necessary for up-regulation of certain FSH target genes including vascular endothelial growth factor. We report that the role of the phosphatidylinositol (PI)-3-kinase/AKT pathway in increasing HIF-1alpha protein in FSH-stimulated GCs extends beyond an increase in mammalian target of rapamycin-stimulated translation. FSH increases phosphorylation of the AKT target mouse double-minute 2 (MDM2); a phosphomimetic mutation of MDM2 is sufficient to induce HIF-1 activity. The PI3-kinase/AKT target forkhead box-containing protein O subfamily 1 (FOXO1) also effects the accumulation of HIF-1alpha as evidenced by the ability of a constitutively active FOXO1 mutant to inhibit the induction by FSH of HIF-1alpha protein and HIF-1 activity. Activation of the PI3-kinase/AKT pathway in GCs by IGF-I is sufficient to induce HIF-1alpha protein but surprisingly not HIF-1 activity. HIF-1 activity also appears to require a PD98059-sensitive protein (kinase) activity stimulated by FSH that is both distinct from mitogen-activated ERK kinase1/2 or 5 and independent of the PI3-kinase/AKT pathway. These results indicate that FSH-stimulated HIF-1 activation leading to up-regulation of targets such as vascular endothelial growth factor requires not only PI3-kinase/AKT-mediated activation of mammalian target of rapamycin as well as phosphorylation of FOXO1 and possibly MDM2 but also a protein (kinase) activity that is inhibited by the classic ERK kinase inhibitor PD98059 but not ERK1/2 or 5. Thus, regulation of HIF-1 activity in GCs by FSH under normoxic conditions is complex and requires input from multiple signaling pathways.

Extracellular Signal-regulated Kinase (ERK)-dependent Phosphorylation of Y-Box-binding Protein 1 (YB-1) Enhances Gene Expression in Granulosa Cells in Response to Follicle-stimulating Hormone (FSH)

“…4C). Unlike many other cell models, IGF 1 does not activate the ERK pathway in GCs (55). Additionally, GCs treated with the RSK-2 inhibitor BI-D1870 (56) exhibited a marked inhibition (89.4% Ϯ 5.3%) of YB-1(Ser 102 ) phosphorylation in the presence of FSH (Fig.…”

Hormone signaling pathways as treatment targets in renal cell cancer (Review)

“…FSHR may also contribute to the development of metastases due to its position on the luminal surface of the endothelium. Moreover, FSHR may play a role in tumor intravasation, allowing RCC cells to penetrate through the endothelium and into circulation (57). In addition, FSHR expression at the periphery of tumors (55), where the tumor interacts with the stroma, may suggest its role in metastases.…”

“…In fact, it has been observed that the binding of FSH to FSH receptors in ovarian granulosa cells induces an increase in hypoxia-inducible factor 1α protein levels, which consequently leads to upregulation of VEGF production ( Fig. 2) (57). It was later suggested that FSHR expression in the blood vessels of ccRCC primary tumors can be used to predict if patients will respond to sunitinib treatment (56).…”

HIF1A-dependent increase in endothelin 2 levels in granulosa cells: role of hypoxia, LH/cAMP, and reactive oxygen species

“…Insulin-like growth factor 1, for instance, augmented the accumulation of HIF1A in normoxia in several cell types (Alam et al 2009, Sartori-Cintra et al 2012, Yu et al 2012. Reactive oxygen species (ROS) is another factor implicated in HIF1A accumulation.…”