Chiba Yoshihiko, Goto Kumiko, Momata Makiko, Kobayashi Taiki, Misawa Miwa
Department of Pharmacology, School of Pharmacy, Hoshi University, Shinagawa-ku, Tokyo, Japan.
J Smooth Muscle Res. 2010;46(4):217-24. doi: 10.1540/jsmr.46.217.
RhoA, a small GTPase, is one of the key proteins of smooth muscle contraction. In allergic asthma, an upregulation of RhoA in bronchial smooth muscle has been suggested. However, the mechanism of its upregulation has not yet been clarified. In the present study, the effects of interleukin-4 (IL-4), one of the T-helper 2 cytokines, on RhoA mRNA expression and promoter activity of RhoA gene were examined in cultured human bronchial smooth muscle cells (hBSMCs). The quantitative real-time RT-PCR analyses revealed that incubation of hBSMCs with IL-4 (10, 30 and 100 ng/mL, for 24 hr) caused an increase in RhoA mRNA in a concentration-dependent manner. In luciferase reporter gene assay using hBSMCs that were transfected with luciferase constructs and were then stimulated with IL-4 (100 ng/mL), an importance of the most proximal STAT6 binding region (78-70 bp upstream of the transcription initiation site) was suggested. It is thus possible that IL-4 is capable of upregulating RhoA by promoting its transcription in hBSMCs. The proximal STAT6 binding region is required for the IL-4-induced increase in promoter activity of the human RhoA gene.
小GTP酶RhoA是平滑肌收缩的关键蛋白之一。在过敏性哮喘中，支气管平滑肌中RhoA的表达上调。然而，其上调机制尚未阐明。在本研究中，我们检测了辅助性T细胞2细胞因子之一白细胞介素-4（IL-4）对培养的人支气管平滑肌细胞（hBSMCs）中RhoA mRNA表达及RhoA基因启动子活性的影响。定量实时RT-PCR分析显示，用IL-4（10、30和100 ng/mL，作用24小时）孵育hBSMCs会导致RhoA mRNA呈浓度依赖性增加。在用荧光素酶构建体转染并随后用IL-4（100 ng/mL）刺激的hBSMCs进行的荧光素酶报告基因检测中，提示了最靠近转录起始位点上游78 - 70 bp处的STAT6结合区域的重要性。因此，IL-4可能通过促进hBSMCs中RhoA的转录来上调其表达。近端STAT6结合区域是IL-4诱导人RhoA基因启动子活性增加所必需的。
