Harada Naoki, Katsuki Takahiro, Takahashi Yuji, Masuda Tatsuya, Yoshinaga Mariko, Adachi Tetsuya, Izawa Takeshi, Kuwamura Mitsuru, Nakano Yoshihisa, Yamaji Ryoichi, Inui Hiroshi
Division of Applied Life Sciences, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, 5998531, Japan.
J Cell Biochem. 2015 Jun;116(6):998-1006. doi: 10.1002/jcb.25054.
Androgen receptor (AR) is known to bind to the same cis-element that glucocorticoid receptor (GR) binds to. However, the effects of androgen signaling on glucocorticoid signaling have not yet been elucidated. Here, we investigated the effects of testosterone on dexamethasone (DEX, a synthetic glucocorticoid)-induced apoptosis of pancreatic β-cells, which might be involved in the pathogenesis of type 2 diabetes mellitus in males. We used INS-1 #6 cells, which were isolated from the INS-1 pancreatic β-cell line and which express high levels of AR. Testosterone and dihydrotestosterone inhibited apoptosis induced by DEX in INS-1 #6 cells. AR knockdown and the AR antagonist hydroxyflutamide each diminished the anti-apoptotic effects of testosterone. AR was localized in the nucleus of both INS-1 #6 cells and pancreatic β-cells of male rats. Induction of thioredoxin-interacting protein (TXNIP) is known to cause pro-apoptotic effects in β-cells. Testosterone suppressed the DEX-induced increase of TXNIP at the transcriptional level. A Chromatin immunoprecipitation assays showed that both AR and GR competitively bound to the TXNIP promoter in ligand-dependent manners. Recombinant DNA-binding domain of AR bound to the same cis-element of the TXNIP promoter that GR binds to. Our results show that AR and GR competitively bind to the same cis-element of TXNIP promoter as a silencer and enhancer, respectively. These results indicate that androgen signaling functionally competes with glucocorticoid signaling in pancreatic β-cell apoptosis.
已知雄激素受体（AR）与糖皮质激素受体（GR）结合的是相同的顺式元件。然而，雄激素信号传导对糖皮质激素信号传导的影响尚未阐明。在此，我们研究了睾酮对地塞米松（DEX，一种合成糖皮质激素）诱导的胰腺β细胞凋亡的影响，这可能与男性2型糖尿病的发病机制有关。我们使用了INS-1 #6细胞，该细胞从INS-1胰腺β细胞系中分离出来，并且表达高水平的AR。睾酮和双氢睾酮抑制了DEX在INS-1 #6细胞中诱导的凋亡。AR敲低和AR拮抗剂羟基氟他胺均减弱了睾酮的抗凋亡作用。AR定位于INS-1 #6细胞和雄性大鼠胰腺β细胞的细胞核中。已知硫氧还蛋白相互作用蛋白（TXNIP）的诱导会在β细胞中引起促凋亡作用。睾酮在转录水平上抑制了DEX诱导的TXNIP增加。染色质免疫沉淀分析表明，AR和GR均以配体依赖性方式竞争性结合TXNIP启动子。AR的重组DNA结合结构域与GR结合的TXNIP启动子的相同顺式元件结合。我们的结果表明，AR和GR分别作为沉默子和增强子竞争性结合TXNIP启动子的相同顺式元件。这些结果表明，雄激素信号传导在胰腺β细胞凋亡中与糖皮质激素信号传导在功能上相互竞争。
