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IGF-I Signaling Is Essential for FSH Stimulation of AKT and Steroidogenic Genes in Granulosa Cells

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journal contribution
posted on 15.04.2014, 00:00 by Ping Zhou, Sarah C. Baumgarten, Yanguang Wu, Jill Bennett, Nicola Winston, Jennifer Hirshfeld-Cytron, Carlos Stocco
FSH and IGF-I synergistically stimulate gonadal steroid production; conversely, silencing the FSH or the IGF-I genes leads to infertility and hypogonadism. To determine the molecular link between these hormones, we examined the signaling cross talk downstream of their receptors. In human and rodent granulosa cells (GCs), IGF-I potentiated the stimulatory effects of FSH and cAMP on the expression of steroidogenic genes. In contrast, inhibition of IGF-I receptor (IGF-IR) activity or expression using pharmacological, genetic, or biochemical approaches prevented the FSH- and cAMP-induced expression of steroidogenic genes and estradiol production. In vivo experiments demonstrated that IGF-IR inactivation reduces the stimulation of steroidogenic genes and follicle growth by gonadotropins. FSH or IGF-I alone stimulated protein kinase B (PKB), which is also known as AKT and in combination synergistically increased AKT phosphorylation. Remarkably, blocking IGF-IR expression or activity decreased AKT basal activity and abolished AKT activation by FSH. In GCs lacking IGF-IR activity, FSH stimulation of Cyp19 expression was rescued by overexpression of constitutively active AKT. Our findings demonstrate, for the first time, that in human, mouse, and rat GCs, the well-known stimulatory effect of FSH on Cyp19 and AKT depends on IGF-I and on the expression and activation of the IGF-IR.

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Funding

This work was supported by National Institutes of Health Grants R01HD057110 and R21HD066233.

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Publisher Statement

This is a copy of an article published in the Molecular Endocrinology © 2013 Endocrine Society. The publication is available at http://mend.endojournals.org/

Publisher

Endocrine Society

Language

en_US

issn

1944-9917

Issue date

01/03/2013

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