Role of Intestinal Cell Kinase in the Intestinal Epithelium

描述（由申请人提供）：肠上皮内细胞更新、分化和细胞死亡的微妙平衡对于维持胃肠道组织结构和功能至关重要，胃肠道组织结构和功能形成肠道正常生理学的基础。肠上皮在整个成年期经历程序性自我更新，并且由于多能上皮干细胞和祖细胞的存在，肠上皮在损伤后快速再生。各种信号传导途径已被认为在胃肠上皮的正常发育和稳态期间在控制干细胞活性、增殖、谱系定型、终末分化和细胞存活中发挥作用。这些信号通路的失调可导致肠肿瘤。在这个建议中，我们专注于阐明一种新的蛋白激酶信号通路，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 mRNA特异性定位于干细胞所在的下隐窝隔室中的未分化肠上皮，表明ICK可能在隐窝上皮的上皮复制、谱系特化和细胞命运决定中发挥作用。我们的初步数据显示[原文如此]，当干/祖细胞活跃复制时，在隐窝上皮再生期间，隐窝上皮中的ICK表达被显著诱导。我们在肠上皮细胞系中的体外敲除研究表明，ICK促进肠上皮细胞增殖和G1细胞周期进展，可能通过选择性调节关键细胞周期调节因子的蛋白质翻译通过哺乳动物雷帕霉素靶（mTOR）途径。总之，这些数据支持我们目前的工作假设，ICK介导的信号调节上皮干细胞和它们的祖细胞在肠上皮细胞的增殖和分化，在正常的肠个体发育和/或在隐窝上皮细胞再生，以响应粘膜损伤。 为了验证这一假设，我们提出了三个具体目标。目标1：确定ICK介导的信号传导是否在肠上皮的正常发育和稳态维持期间体内调节上皮增殖和分化;目的2：确定ICK介导的信号传导是否对响应于粘膜损伤的肠上皮修复和再生重要;目的3：确定ICK介导的信号传导是否通过调节蛋白质翻译来调节肠上皮细胞增殖和分化，通过mTOR信号通路调节细胞周期。 公共卫生相关性：对ICK信号通路的研究将为更好地理解肠上皮发育和再生过程中干细胞命运和功能调控的分子基础提供帮助。因此，这项研究的结果将有助于建立一个阶段，检查ICK作为一个潜在的治疗目标，诊断，预防和治疗胃肠道疾病和癌症的作用。

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.