我们前期研究表明肠干细胞凋亡是放射性肠损伤的重要原因 (Liu ZH, Am J Physiol)，但放射线对肠干细胞增殖的影响仍知之甚少。既往研究表明内质网应激（ERS）的激活能促进肠干细胞增殖；衔接蛋白βarrestin1(βarr1)是参与ERS的重要蛋白。我们进一步发现放射线能提高小肠隐窝βarr1、p-PERK和p-eIF2α表达；抑制ERS可降低肠隐窝增殖能力，但βarr1与ERS互调控作用在放射性肠损伤肠干细胞增殖中仍不明确，本课题拟研究1)下调βarr1或抑制ERS对小鼠肠隐窝增殖的影响；2)用Lgr5敲入小鼠体外分离培养Lgr5+肠干细胞，通过高表达βarr1研究βarr1对PERK调控作用，同时低表达βarr1或抑制ERS来探讨βarr1通过PERK/eIF2α来调控ERS介导的肠干细胞增殖的机制；3)在放射性肠炎临床标本中验证此调控。本项目有望为今后临床治疗提供参考。

Our previous study reveals that Intestinal stem cell apoptosis is the critical factor of radiation (IR)-induced intestinal damage (Liu ZH, et al. Am J Physiol- Gastrointest Liver Physiol 2014:G1033-43), but the effect of IR on intestinal stem cell proliferation remains to be elusive. Past studies have demonstrated that endoplasmic reticulum stress (ERS) can potentiate intestinal stem cell proliferation and also found that βarrestin1 (βarr1), a G protein receptor-associated adaptor protein, is importantly involved in ER process. We further found that IR promoted the expressions of βarr1, p-PERK and p-eIF2α in intestinal crypts of mice and inhibition of ERS decreased the proliferation index of intestinal crypts. However, the significance of mutual regulation between βarr1 and ERS on intestinal stem cell proliferation in IR-induced intestinal damage is still unknown. First, our future work is to explore the impact of down-regulation of βarr1 or inhibition of ERS on proliferation index of intestinal crypt in mice. Second, we will isolate and culture Lgr5 positive cells from Lgr5 konck-in mice and then, study the regulation of βarr1 on PERK when βarr1 is over-expressed in Lgr5 positive cells. Moreover, we will analyze the regulation of βarr1 on ERS-mediated intestinal stem cell proliferation though PERK/eIF2α pathway by down-regulating βarr1 expression or suppressing ERS. Finally, we will verify the above mechanism in clinical samples. The project is expected to provide the meaningful significance for clinical treatment in the future.