Androgen receptor stimulates bone sialoprotein (BSP) gene transcription via cAMP response element and activator protein 1/glucocorticoid response elements.
Bone sialoprotein (BSP) is an early marker of osteoblast differentiation. Androgens are steroid hormones that are essential for skeletal development. The androgen receptor (AR) is a transcription factor and a member of the steroid receptor superfamily that plays an important role in male sexual differentiation and prostate cell proliferation. To determine the molecular mechanism involved in the stimulation of bone formation, we have analyzed the effects of androgens and AR effects on BSP gene transcription. AR protein levels were increased after AR overexpression in ROS17/2.8 cells. BSP mRNA levels were increased by AR overexpression. However, the endogenous and overexpressed BSP mRNA levels were not changed by DHT (10(-8) M, 24 h). Whereas luciferase (LUC) activities in all constructs, including a short construct (nts -116 to +60), were increased by AR overexpression, the basal and LUC activities enhanced by AR overexpression were not induced by DHT (10(-8)M, 24 h). The effect of AR overexpression was abrogated by 2 bp mutations in either the cAMP response element (CRE) or activator protein 1 (AP1)/glucocorticoid response element (GRE). Gel shift analyses showed that AR overexpression increased binding to the CRE and AP1/GRE elements. Notably, the CRE-protein complexes were supershifted by phospho-CREB antibody, and CREB, c-Fos, c-Jun, and AR antibodies disrupted the complexes formation. The AP1/GRE-protein complexes were supershifted by c-Fos antibody and c-Jun, and AR antibodies disrupted the complexes formation. These studies demonstrate that AR stimulates BSP gene transcription by targeting the CRE and AP1/GRE elements in the promoter of the rat BSP gene.
Takai
Hideki
H
Department of Periodontology, Nihon University School of Dentistry at Matsudo, Chiba 271-8587, Japan.
Nakayama
Youhei
Y
Kim
Dong-Soon
DS
Arai
Masato
M
Araki
Shouta
S
Mezawa
Masaru
M
Nakajima
Yu
Y
Kato
Naoko
N
Masunaga
Hiroshi
H
Ogata
Yorimasa
Y
D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D005938:Glucocorticoids / Q000502:physiology; D058574:Integrin-Binding Sialoprotein; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011944:Receptors, Androgen / Q000378:metabolism*; D020218:Response Elements; D012795:Sialoglycoproteins / Q000096:biosynthesis / Q000235:genetics*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D015533:Transcriptional Activation
D005938:Glucocorticoids; C546873:Ibsp protein, rat; D058574:Integrin-Binding Sialoprotein; D009687:Nuclear Proteins; D012333:RNA, Messenger; D011944:Receptors, Androgen; D012795:Sialoglycoproteins; D018808:Transcription Factor AP-1; D000242:Cyclic AMP; D000469:Alkaline Phosphatase