Human Follicle-Stimulating Hormone (FSH) Receptor Interacts with the Adaptor Protein APPL1 in HEK 293 Cells: Potential Involvement of the PI3K Pathway in FSH Signaling1

• Published in: Biology of reproduction 2004-08, Vol.71 (2), p.629-636
• Main Authors: Nechamen, Cheryl A, Thomas, Richard M, Cohen, Brian D, Acevedo, Giselles, Poulikakos, Poulikos I, Testa, Joseph R, Dias, James A
• Format: Article
• Language: English
• Subjects: apoptosis; Contents; follicle-stimulating hormone; follicle-stimulating hormone receptor; mechanisms of hormone action; signal transduction
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod.103.025833

Selection of a dominant follicle that will ovulate likely occurs by activation of cell survival pathways and suppression of death-promoting pathways in a mechanism involving FSH and its cognate receptor (FSHR). A yeast two-hybrid screen of an ovarian cDNA library was employed to identify potential interacting partners with human FSHR intracellular loops 1 and 2. Among eight cDNA clones identified in the screen, APPL1 (adaptor protein containing PH domain, PTB domain, and leucine zipper motif; also known as APPL or DIP13α) was chosen for further analysis. APPL1 appears to coimmunoprecipitate with FSHR in HEK 293 cells stably expressing FSHR (293/FSHR cells), confirming APPL1 as a potential FSHR-interacting partner. The phosphorylation status of members of the phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway was also examined because of the proposed role of APPL1 in the antiapoptotic PI3K/Akt pathway. FOXO1a, also referred to as forkhead homologue in rhabdomyosarcoma, is a downstream effector in the pathway and tightly linked to expression of proapoptotic genes. FOXO1a, but not the upstream kinase Akt, is rapidly phosphorylated, and FOXO1a is thereby inactivated when 293/FSHR cells are treated with FSH. In addition, FSHR coimmunoprecipitates with Akt. The identification of APPL1 as a potential interactor with FSHR and the finding that FOXO1a is phosphorylated in response to FSH provide a possible link between FSH and PI3K/Akt signaling, which may help to delineate a survival mechanism whereby FSH selects the dominant follicle to survive.