Yonsei Med J.  2015 Nov;56(6):1590-1596. 10.3349/ymj.2015.56.6.1590.

The Role of Foxo3 in Leydig Cells

• Choi YS
• Song JE
• Kong BS
• Hong JW
• Novelli S
• Lee EJ

• KMID: 2345887
• DOI: http://doi.org/10.3349/ymj.2015.56.6.1590

Abstract

PURPOSE
Foxo3 in female reproduction has been reported to regulate proliferation of granulose cells that form follicles. There are no reports so far that discuss on the role of Foxo3 in males. This study was designed to outline the role of Foxo3 in the testes.
MATERIALS AND METHODS
Testes from mice at birth to postpartum week (PPW) 5 were isolated and examined for the expression of Foxo3 using immunostaining. To elucidate role of Foxo3 in Leydig cells, R2C cells were treated with luteinizing hormone (LH) and the phosphorylation of Foxo3. Testosterone and steroidogenic acute regulatory (StAR) protein levels were measured after constitutive active [triple mutant (TM)] human FOXO3 adenovirus was transduced and StAR promoter assay was performed.
RESULTS
Foxo3 expression in the testicles started from birth and lasted until PPW 3. After PPW 3, most Foxo3 expression occurred in the nuclei of Leydig cells; however, at PPW 5, Foxo3 was expressed in both the nucleus and cytoplasm. When R2C cells were treated with luteinizing hormone, Foxo3 phosphorylation levels by AKT increased. After blocking the PI3K pathway, LH-induced phosphorylated Foxo3 levels decreased, indicating that LH signaling regulates Foxo3 localization. When active FOXO3-TM adenovirus was introduced into a Leydig tumor cell line, the concentrations of testosterone and StAR protein decreased. When FOXO3 and a StAR promoter vector were co-transfected into HEK293 cells for a reporter assay, FOXO3 inhibited the StAR promoter.
CONCLUSION
FOXO3 affects testosterone synthesis by inhibiting the formation of StAR protein. LH hormone, meanwhile, influences Foxo3 localization, mediating its function.

Keyword

Foxo3; Leydig cell; testosterone; StAR

MeSH Terms

Animals
Cell Aging/*physiology
Cell Nucleus/metabolism
Cytoplasm/metabolism
Forkhead Transcription Factors/*metabolism
HEK293 Cells
Humans
Leydig Cells/*drug effects/*enzymology/metabolism
Luteinizing Hormone/blood
Male
Mice
Phosphatidylinositol 3-Kinases
Phosphoproteins/metabolism
Phosphorylation
Signal Transduction/drug effects
Testosterone/blood/*metabolism
Forkhead Transcription Factors
Luteinizing Hormone
Phosphatidylinositol 3-Kinases
Phosphoproteins
Testosterone