Follicle-stimulating hormone amplifies insulin-like growth factor I-mediated activation of AKT/protein kinase B signaling in immature rat Sertoli cells

Shafiq A. Khan, Lilianne Ndjountche, Lauren Pratchard, L. J. Spicer, John S. Davis

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Abstract

FSH and IGF-I are both important determinants of testicular development and Sertoli cell function. The present studies were performed to determine the actions of FSH and IGF-I on PI3K/AKT protein kinase signaling in immature rat Sertoli cells. Primary cultures of rat Sertoli cells were prepared from 10-d-old rats. After 7 d in culture, Sertoli cells were treated with IGF-I, FSH, or IGF-I plus FSH. In some experiments cultures were treated with 8-bromo-cAMP (40 μM), (Bu)2cAMP (40 μM), or forskolin (10 μM). After treatments, cell lysates were prepared, and the activation state of AKT and cAMP response element-binding protein (CREB) was determined by Western blot analysis using phosphorylation site-specific antibodies. IGF-I had little effect on CREB phosphorylation, but rapidly increased the phosphorylation of AKT in a concentration-dependent manner. Maximal stimulatory effects of IGF-I were observed at 10-20 ng/ml. Treatment with FSH (0.9 IU/ml) or forskolin for 20 min increased CREB phosphorylation, but had little effect on AKT phosphorylation. However, FSH caused a concentration-dependent increase in IGF-I-induced AKT phosphorylation. Longer incubations (1-4 h) with FSH alone resulted in the elevation of AKT phosphorylation concomitant with an increased secretion of IGF-I and decreased production of IGF-binding protein-3, implicating endogenous IGF-I in the action of FSH on AKT phosphorylation. IGF-I- and FSH-dependent AKT phosphorylation was inhibited by LY29400 (10 μM), a PI3K inhibitor, and by IGF-binding protein 3, but not by a PKA inhibitor (H89). The present study demonstrates that immature rat Sertoli cells possess multiple protein kinase signaling cascades that are regulated by FSH. Furthermore, FSH amplifies IGF-I-mediated PI3K/AKT signaling in Sertoli cells. The results provide evidence for intracellular signaling mechanisms that may be required for the proliferation and differentiation of Sertoli cells.

Original languageEnglish (US)
Pages (from-to)2259-2267
Number of pages9
JournalEndocrinology
Volume143
Issue number6
DOIs
StatePublished - Jan 1 2002

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Proto-Oncogene Proteins c-akt
Sertoli Cells
Follicle Stimulating Hormone
Insulin-Like Growth Factor I
Phosphorylation
Cyclic AMP Response Element-Binding Protein
Phosphatidylinositol 3-Kinases
Insulin-Like Growth Factor Binding Protein 3
Colforsin
Protein Kinases
8-Bromo Cyclic Adenosine Monophosphate
2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
Western Blotting

ASJC Scopus subject areas

  • Endocrinology

Cite this

Follicle-stimulating hormone amplifies insulin-like growth factor I-mediated activation of AKT/protein kinase B signaling in immature rat Sertoli cells. / Khan, Shafiq A.; Ndjountche, Lilianne; Pratchard, Lauren; Spicer, L. J.; Davis, John S.

In: Endocrinology, Vol. 143, No. 6, 01.01.2002, p. 2259-2267.

Research output: Contribution to journalArticle

Khan, Shafiq A. ; Ndjountche, Lilianne ; Pratchard, Lauren ; Spicer, L. J. ; Davis, John S. / Follicle-stimulating hormone amplifies insulin-like growth factor I-mediated activation of AKT/protein kinase B signaling in immature rat Sertoli cells. In: Endocrinology. 2002 ; Vol. 143, No. 6. pp. 2259-2267.
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