Department of Pathophysiology, The Second Military Medical University, Shanghai, China.
J Cell Mol Med. 2013 Jul;17(7):863-72. doi: 10.1111/jcmm.12069. Epub 2013 May 15.
Stomatin is an important lipid raft-associated protein which interacts with membrane proteins and plays a role in the membrane organization. However, it is unknown whether it is involved in the response to hypoxia and glucocorticoid (GC) in alveolar epithelial cells (AEC). In this study we found that hypoxia and dexamethasone (dex), a synthetic GC not only up-regulated the expression of stomatin alone, but also imposed additive effect on the expression of stomatin in A549 cells, primary AEC and lung of rats. Then we investigated whether hypoxia and dex transcriptionally up-regulated the expression of stomatin by reporter gene assay, and found that dex, but not hypoxia could increase the activity of a stomatin promoter-driven reporter gene. Further deletion and mutational studies demonstrated that a GC response element (GRE) within the promoter region mainly contributed to the induction of stomatin by dex. Moreover, we found that hypoxia exposure did not affect membrane-associated actin, but decreased actin in cytoplasm in A549 cells. Inhibiting stomatin expression by stomatin siRNA significantly decreased dense of peripheral actin ring in hypoxia or dex treated A549 cells. Taken all together, these data indicated that dex and/or hypoxia significantly up-regulated the expression of stomatin in vivo and in vitro, which could stabilize membrane-associated actin in AEC. We suppose that the up-regulation of stomatin by hypoxia and dex may enhance the barrier function of alveolar epithelia and mediate the adaptive role of GC to hypoxia.
板层素是一种重要的脂筏相关蛋白，它与膜蛋白相互作用，在膜组织中发挥作用。然而，目前尚不清楚它是否参与肺泡上皮细胞（AEC）对缺氧和糖皮质激素（GC）的反应。在这项研究中，我们发现缺氧和地塞米松（dex），一种合成的 GC，不仅单独上调了板层素的表达，而且对 A549 细胞、原代 AEC 和大鼠肺中的板层素表达有相加作用。然后，我们通过报告基因检测研究了缺氧和地塞米松是否转录地上调板层素的表达，发现地塞米松而不是缺氧可以增加板层素启动子驱动的报告基因的活性。进一步的缺失和突变研究表明，启动子区域内的一个 GC 反应元件（GRE）主要有助于地塞米松诱导板层素的表达。此外，我们发现缺氧暴露不会影响膜相关肌动蛋白，但会减少 A549 细胞细胞质中的肌动蛋白。用板层素 siRNA 抑制板层素的表达，可显著减少缺氧或地塞米松处理的 A549 细胞外周肌动蛋白环的密度。综上所述，这些数据表明，地塞米松和/或缺氧可显著上调体内和体外 AEC 中板层素的表达，从而稳定 AEC 中膜相关肌动蛋白。我们假设缺氧和地塞米松对板层素的上调可能增强肺泡上皮的屏障功能，并介导 GC 对缺氧的适应性作用。
