FoxO1 is a negative regulator of FSHβ gene expression in basal and GnRH-stimulated conditions in female.
The importance of forkhead box class O (FoxO) proteins in reproductive endocrinology has been confirmed by age-dependent infertility in females in a FoxO3a-knockout mouse model. In this study, FoxO1 was detected in gonadotropes in the anterior pituitary. Overexpression of FoxO1 in primary pituitary cells decreased FSHβ gene expression in both basal and GnRH-stimulated conditions, and this result was replicated by the human FSHβ promoter activity. Although direct binding of FoxO1 to FoxO-binding element (FBE) (at -124 to -119 bp of the human FSHβ promoter) was not detected in an electrophoretic mobility shift assay, a DNA pull-down assay and transfection study using the mutant FBE reporter vector revealed that FBE is necessary in FSHβ suppression by FoxO1, suggestive of other cofactor requirements. GnRH stimulated the phosphoinositide 3-kinase pathway, which induced posttranslational modification of FoxO1 and retained it in the cytoplasm. We also confirmed this result in primary cell cultures; most of the FoxO1 was detected in the cytoplasm when treated with GnRH but in the nucleus when the phosphoinositide 3-kinase pathway was inhibited. These findings suggest that FoxO1 is regulated by the GnRH signaling pathway and functions as a negative regulator of FSHβ gene expression.
Endocrinology, Institute of Endocrine Research (Y.-S.C., H.J.L., C.R.K., Y.H.C., M.R.S., E.J.L.), Brain Korea 21 Project for Medical Science (Y.-S.C., H.J.L., E.J.L.), and Department of Biochemistry and Molecular Biology (Y.J.L.), Yonsei University College of Medicine, 120-752, Seoul, Korea.
Young-Suk
YS
Choi
Hyeon Jeong
HJ
Lee
Cheol Ryong
CR
Ku
Yoon Hee
YH
Cho
Mi Ran
MR
Seo
Yoo Jeoung
YJ
Lee
Eun Jig
EJ
Lee
D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics / Q000378:metabolism*; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071161:Forkhead Box Protein O1
D037201:Follicle Stimulating Hormone, beta Subunit; D051858:Forkhead Transcription Factors; D007987:Gonadotropin-Releasing Hormone; D009419:Nerve Tissue Proteins; C074639:Foxo1 protein, rat; D000071161:Forkhead Box Protein O1