This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kayampilly, P. P. Articles by Menon, K. M. J. Search for Related Content PubMed PubMed Citation Articles by Kayampilly, P. P. Articles by Menon, K. M. J. Pubmed/NCBI databases Gene GEO Profiles HomoloGene UniGene Compound via MeSH Substance via MeSH Hazardous Substances DB MENOTROPINS

Follicle-Stimulating Hormone Increases Tuberin Phosphorylation and Mammalian Target of Rapamycin Signaling through an Extracellular Signal-Regulated Kinase-Dependent Pathway in Rat Granulosa Cells

Departments of Obstetrics and Gynecology and Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109

Address all correspondence and requests for reprints to: Dr. K. M. J. Menon, 6428 Medical Science I, 1150 West Medical Center Drive, University of Michigan Medical School, Ann Arbor, Michigan 48109. E-mail: kmjmenon{at}umich.edu.

FSH-mediated regulation of mammalian target of rapamycin (mTOR) signaling in proliferating granulosa cells and the effect of dihydrotestosterone (DHT) on this pathway were examined. Inhibiting mTOR activation using rapamycin significantly reduced the FSH-mediated increase in cyclin D2 mRNA expression, suggesting that mTOR plays a role in the FSH-mediated increase in granulosa cell proliferation. FSH treatment of granulosa cells showed a 2-fold increase in phosphorylation of p70S6 kinase (p70S6K), the downstream target of mTOR. The increase in p70S6K phosphorylation by FSH treatment was abolished by prior exposure to DHT, suggesting that DHT inhibits FSH-mediated activation of mTOR signaling in cultured granulosa cells. The effect of FSH and DHT treatment on tuberin (TSC2), the upstream regulator of mTOR, was then examined. FSH treatment increased TSC2 phosphorylation, and pretreatment with DHT for 24 h reduced this stimulation. These results indicate that reduced p70S6K phosphorylation observed in DHT-treated cells might be the result of reduced TSC2 phosphorylation. Because Akt is the upstream activator of TSC2 phosphorylation, the effect of Akt inhibition was examined to test whether FSH-mediated TSC2 phosphorylation proceeds through an Akt-dependent pathway. Our results show that inhibiting Akt phosphorylation did not block FSH-stimulated TSC2 phosphorylation, whereas ERK inhibition reduced FSH-mediated stimulation. These results demonstrate the involvement of ERK rather than Akt in FSH-mediated TSC2 phosphorylation in granulosa cells. Based on these observations, we conclude that in granulosa cells, FSH uses a protein kinase A-/ERK-dependent pathway to stimulate TSC2 phosphorylation and mTOR signaling, and DHT treatment significantly reduces this response.

This article has been cited by other articles:

				T. R. Korfhagen, T. D. Le Cras, C. R. Davidson, S. M. Schmidt, M. Ikegami, J. A. Whitsett, and W. D. Hardie Rapamycin Prevents Transforming Growth Factor-{alpha}-Induced Pulmonary Fibrosis Am. J. Respir. Cell Mol. Biol., November 1, 2009; 41(5): 562 - 572. [Abstract] [Full Text] [PDF]

				P. P. Kayampilly and K. M. J. Menon Follicle-Stimulating Hormone Inhibits Adenosine 5'-Monophosphate-Activated Protein Kinase Activation and Promotes Cell Proliferation of Primary Granulosa Cells in Culture through an Akt-Dependent Pathway Endocrinology, February 1, 2009; 150(2): 929 - 935. [Abstract] [Full Text] [PDF]