Role of Intestinal Cell Kinase in the Intestinal Epithelium

描述(申请人提供)：肠上皮内细胞更新、分化和细胞死亡的微妙平衡对维持胃肠道组织结构和功能至关重要，而胃肠道组织结构和功能是肠道正常生理的基础。由于存在多能上皮干细胞和祖细胞，肠上皮在成年后经历程序性自我更新，并在损伤后快速再生。在胃肠道上皮细胞的正常发育和动态平衡过程中，多种信号通路在干细胞活性、增殖、谱系定位、终末分化和细胞存活等方面发挥着重要的调控作用。这些信号通路的失控会导致肠道肿瘤。在这项建议中，我们重点阐述了一种新的蛋白激酶信号通路，该信号通路可能在调节肠上皮的发育和再生中发挥重要作用。 肠细胞激酶(ICK)是一种高度保守的丝氨酸/苏氨酸蛋白激酶。在小肠中，ICK基因特异性地定位于干细胞所在的隐窝下部未分化的肠上皮细胞，提示ICK可能在隐窝上皮细胞的复制、谱系确定和细胞命运的决定中发挥作用。我们的初步数据显示，当干细胞/祖细胞活跃复制时，在隐窝上皮再生过程中，[SIC]在隐窝上皮细胞中显著诱导ICK表达。我们在肠上皮细胞系中的体外基因敲除研究表明，ICK促进肠上皮细胞增殖和G1细胞周期进展，可能是通过选择性地通过哺乳动物雷帕霉素靶点(MTOR)途径调节关键细胞周期调节因子的蛋白质翻译。综上所述，这些数据支持我们目前的工作假说，即在正常的肠道个体发育和/或粘膜损伤后的隐窝上皮再生过程中，ICK介导的信号调节肠上皮中上皮干细胞及其前体细胞的增殖和分化。 为了检验这一假设，我们提出了三个具体目标。目的1：确定在肠上皮正常发育和动态平衡维持过程中，ICK介导的信号通路是否在体内调节肠上皮细胞的增殖和分化；目的2：确定ICK介导的信号通路是否在黏膜损伤时对肠上皮细胞的修复和再生起重要作用；目的3：确定ICK介导的信号通路是否通过mTOR信号通路调节细胞周期调节因子的蛋白翻译来调节肠上皮细胞的增殖和分化。 公共卫生相关性：对ICK信号通路的研究将为干细胞在肠上皮发育和再生过程中的命运和功能调控提供更好的分子基础。因此，这项研究的结果将有助于为研究ICK作为诊断、预防和治疗胃肠道疾病和癌症的潜在治疗靶点的作用奠定基础。

DESCRIPTION (provided by applicant): A delicate balance of cell renewal, differentiation and cell death within the intestinal epithelium is crucial to maintain the gastrointestinal tissue structure and function which form the basis for normal physiology of the gut. Intestinal epithelium undergoes a programmed self-renewal throughout adult life and a rapid regeneration after injury due to the presence of multipotent epithelial stem and progenitor cells. Various signaling pathways have been implicated to play a role in the control of stem cell activity, proliferation, lineage commitment, terminal differentiation and cell survival during normal development and homeostasis of the gastrointestinal epithelium. Deregulation of these signaling pathways can lead to intestinal neoplasia. In this proposal, we focus on the elucidation of a novel protein kinase signaling pathway that may play an important role in regulating the development and regeneration of the intestinal epithelium. Intestinal cell kinase (ICK) is a highly conserved serine/threonine protein kinase. In the small intestine, the ICK mRNA localizes specifically to the undifferentiated intestinal epithelium in the lower crypt compartment where stem cells reside suggesting that ICK may play a role in epithelial replication, lineage specification and cell fate determination in crypt epithelium. Our preliminary data shows [sic] that ICK expression in crypt epithelium is significantly induced during crypt epithelium regeneration when stem/progenitor cells actively replicate. Our in vitro knockdown studies in intestinal epithelial cell lines suggest that ICK promotes intestinal epithelial proliferation and G1 cell cycle progression, possibly by selectively regulating protein translation of key cell cycle regulators through the mammalian target of rapamycin (mTOR) pathway. Taken together these data support our current working hypothesis that ICK mediated signaling regulates proliferation and differentiation of epithelial stem cells and their progenitors in the intestinal epithelium during normal intestinal ontogeny and/or during the crypt epithelium regeneration in response to mucosal injury. To test this hypothesis, we propose three specific aims. Aim 1: Determine whether ICK mediated signaling regulates epithelial proliferation and differentiation in vivo during normal development and homeostatic maintenance of the intestinal epithelium; Aim 2: Determine whether ICK mediated signaling is important for intestinal epithelial repair and regeneration in response to mucosal injury; Aim 3: Determine whether ICK mediated signaling regulates intestinal epithelial cell proliferation and differentiation by modulating protein translation of cell cycle regulators through the mTOR signaling pathway. PUBLIC HEALTH RELEVANCE: The study of the ICK signaling pathway will provide a better understanding of the molecular basis for the regulation of stem cell fate and function during intestinal epithelium development and regeneration. Thus, the outcomes from this study will help to set up the stage for examining the role of ICK as a potential therapeutic target for diagnosis, prevention and treatment of gastrointestinal diseases and cancer.