Department of Anatomy, School of Medicine, University of Occupational and Environmental Health, 1-1, Iseigaoka, Yahatanishi, Kitakyushu 807-8555, Japan.
J Cell Biochem. 2010 May;110(1):104-11. doi: 10.1002/jcb.22513.
Intestinal epithelial cells (IECs) are exposed to external environment, microbial and viral products, and serve as essential barriers to antigens. Recent studies have shown that IECs express Toll-like receptors (TLRs) and respond to microbial components. The antimicrobial and antiviral barriers consist of many molecules including TLRs. To investigate the further component of this barrier in intestine, we examined the expression of double-stranded RNA-dependent protein kinase (PKR). PKR is a player in the cellular antiviral response and phosphorylates alpha-subunit of the eukaryotic translation initiation factor 2 (eIF-2alpha) to block protein synthesis and induces apoptosis. In this study, we showed that the expression of PKR was restricted to the cytoplasm of absorptive epithelial cells in the intestine of adult rat. We also demonstrated that PKR was expressed in the cultured rat intestinal epithelial cells (IEC-6). The level of PKR protein expression and the activity of alkaline phosphatase (ALP) increased in the cultured IEC-6 cells in a time-dependent manner. Inhibition of PKR by the 2-aminopurine treatment decreased ALP activity in the IEC-6 cells. Treatment of IEC-6 cells with synthetic double-stranded RNA (dsRNA) induced cell death in a dose-dependent manner. The addition of hydrocortisone also provoked suppression of PKR expression and ALP activity. This modulation might be mediated by signal transducers and activators of transcription-1 (STAT-1) protein. We concluded that PKR is expressed in IECs as potent barriers to antigens and is a possible modulator of the differentiation of rat IECs.
肠上皮细胞（IECs）暴露于外环境、微生物和病毒产物中，是抗原的重要屏障。最近的研究表明，IECs 表达 Toll 样受体（TLRs）并对微生物成分作出反应。抗菌和抗病毒屏障由包括 TLRs 在内的许多分子组成。为了研究肠道中这一屏障的进一步组成部分，我们研究了双链 RNA 依赖性蛋白激酶（PKR）的表达。PKR 是细胞抗病毒反应的参与者，可磷酸化真核翻译起始因子 2（eIF-2alpha）的α亚基，从而阻断蛋白质合成并诱导细胞凋亡。在这项研究中，我们表明 PKR 的表达仅限于成年大鼠肠道吸收上皮细胞的细胞质中。我们还证明 PKR 在培养的大鼠肠上皮细胞（IEC-6）中表达。PKR 蛋白表达水平和碱性磷酸酶（ALP）的活性在培养的 IEC-6 细胞中呈时间依赖性增加。用 2-氨基嘌呤处理抑制 PKR 会降低 IEC-6 细胞中的 ALP 活性。用合成双链 RNA（dsRNA）处理 IEC-6 细胞会导致细胞死亡呈剂量依赖性。氢化可的松的添加也会引起 PKR 表达和 ALP 活性的抑制。这种调节可能是由信号转导和转录激活因子-1（STAT-1）蛋白介导的。我们得出结论，PKR 在 IECs 中表达，作为抗原的有效屏障，并且可能是大鼠 IECs 分化的调节剂。
