Regulation of FSH receptor promoter activation in the osteoclast Samir Zaidi, Ling-Ling Zhu, Rajesh Mali, Jameel Iqbal, Guozhe Yang, Mone Zaidi * , Li Sun Mount Sinai Bone Program, Mount Sinai School of Medicine, One Gustave L. Levy Place, NY 10029, USA Received 16 July 2007 Available online 24 July 2007 Abstract We have shown recently that FSH stimulates osteoclast formation and function by a direct action on a G i -coupled FSH receptor (FSHR). Here, we report properties of the mouse FSH receptor promoter in the context of its activation in RAW-C3 osteoclast precursor macrophages. Basal promoter activity was low, but was significantly stimulated by receptor activator for NF-jB-ligand (RANK-L), a critical osteoclastogenic and pro-resorptive cytokine. In contrast, FSH dampened FSHR promoter activation, while estrogen had no effect. We surmise that the FSHR expression is regulated distinctly in the osteoclast, and differently from other cells, such as the ovarian follicular and Leydig cells. Ó 2007 Elsevier Inc. All rights reserved. Keywords: Follicle stimulating hormone receptor promoter; Osteoclast; Estrogen Hitherto, follicle stimulating hormone (FSH) was rec- ognized solely as a hormone regulating ovarian follicular cell development and function [1]. We recently demon- strated that FSH acts on the osteoclast, the cell that resorbs bone, to stimulate its genesis and function [2]. We further identified FSH receptors (FSHRs) both on human and mouse osteoclasts and their precursors [2]. These receptors specifically mediate the pro-osteoclasto- genic actions of FSH, which have been recently verified by others [3]. We reported that the osteoclastic receptor was non-tra- ditional in that it coupled with G i2a so that its stimulation by FSH resulted in a concentration-dependent reduction in cAMP levels [2]. That the FSHR/G i2a interaction was nec- essary for downstream signaling through Erk and NF-jB to stimulate osteoclastogenesis was verified by a loss of these functions in G i2a null cells. In contrast to osteoclasts, ovarian follicular FSHRs have been found consistently to interact with a G sa . FSHRs belong to an evolutionarily remote family of G protein coupled membrane receptors that have seven trans- membrane spanning domains and are encoded by a single copy gene [4]. The gene contains 10 exons and 9 introns, and is highly conserved amongst species. Exons 1 through 9 encode the large, ligand-binding extracellular domain, while exon 10 encodes the transmembrane regions [5]. Alternative splicing of the single gene results in up to four distinct transcripts [6]. There is very little information on how the expression of FSHRs is regulated, even in the context of ovarian follicular cells or testicular Sertoli cells. The 5 0 flanking region in the rat and humans displays 2 and 5 transcrip- tional start sites, respectively [7,8]. No TATA boxes, CCAAT elements or GC box motifs have been identified in any species [7,9,10]. The 5 0 flanking region also lacks consensus sequences for cAMP binding, AP-2 binding or methylation sites. However, the rat, but not the human gene promoter does have an AP-1 binding site, whereas the human gene selectively displays a half con- sensus estrogen response element (ERE) [11]. There is also a set of initiator elements (Inrs) that likely function in positioning RNA polymerase II in the absence of the TATA box [8]. Moreover, an E-box sequence has been identified in the rat, human, sheep and mouse promoters that binds upstream regulatory factors 1 and 2 (USF-1 and USF-2) [12]; the latter are known members of the helix-loop-helix family of transcription factors. Finally, 0006-291X/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2007.07.081 * Corresponding author. Fax: +1 212 426 8312. E-mail address: mone.zaidi@mssm.edu (M. Zaidi). www.elsevier.com/locate/ybbrc Biochemical and Biophysical Research Communications 361 (2007) 910–915