Function of a Novel Tyrosine Kinase in the Intestine

描述(申请人摘要)：管理人员快速流动的机制 和多种上皮细胞类型的持续分化 对胃肠道的认识还不够深入。努力找出那些 调节肠道上皮细胞分化导致分离出一种 来自小鼠小肠的新的上皮特异性酪氨酸激酶 这位研究人员名叫SIK，意为Src相关肠激酶。SIK表达式 是发育调节的，并仅限于分化上皮细胞 内层，它在肠道中表达水平最高。这个 研究人员鉴定了SIK的人类同源物，并确定它是 从转移性乳腺中分离出的乳腺肿瘤激酶BRK 肿瘤。BRK在人类胃肠道分化细胞中表达 肠道及其在结肠肿瘤中的表达增加。在结肠癌细胞中 LINES，BRK存在于称为Sam68/SLM核的新型核结构中 与RNA结合蛋白Sam68结合的小体(SNB)。 SIK/BRK对Sam68的磷酸化抑制Sam68与RNA的结合 在核RNA输出中作为HIV1 Rev细胞同源物。Sam68 已经被证明在促进有丝分裂方面发挥了积极的作用，它是 一种名为STAR(Signal Transducers And Signal Transducers)的RNA结合蛋白家族 核糖核酸激活剂)。STAR蛋白已被证明可以调节基因表达 在转录和转录后水平上。调查员 已经确定SIK/BRK还可以磷酸化更多的 STAR家族，类Sam68的哺乳动物蛋白SLM1和SLM2。调查员 SIK/BRK调控肠道相关基因表达的假说 上皮细胞的分化和/或转化通过改变其活性 星状蛋白。在提议的工作中，调查员将重点放在获得 更好地理解RNA结合蛋白的磷酸化作用 在正常和转化的肠道细胞中通过SIK/BRK表达STAR家族。这个 研究人员将继续探索sik在转基因中的生物学作用 表达显性负性或肉豆蔻酰化SIK蛋白的小鼠 肠道，以及sik基因中断的小鼠。尽管锡克人 基因敲除的小鼠是存活的，没有明显的肠道表型， 调查员将向他们提出质疑，以确定他们是否改变了 对引起伤害或肿瘤的药物的敏感性。这些实验将 加深对BRK/SIK信号转导及STAR蛋白在 在正常肠道和结肠肿瘤中。

DESCRIPTION (Applicant's Abstract): Mechanisms regulating the rapid turnover and continuous differentiation of the multiple epithelial cell types in the gastrointestinal tract are not well understood. Efforts to identify genes that regulate intestinal epithelial cell differentiation led to the isolation of a novel epithelial-specific tyrosine kinase from the mouse small intestine that the investigator named Sik, for Src-related intestinal kinase. Sik expression is developmentally regulated and restricted to differentiating epithelial linings, and it is expressed at highest levels in the intestinal tract. The investigator identified the human homologue of Sik and determined that it is the breast tumor kinase BRK, which had been isolated from a metastatic breast tumor. BRK is expressed in differentiating cells of the human gastrointestinal tract and its expression is increased in colon tumors. In colon cancer cell lines, BRK is present in novel nuclear structures called Sam68/SLM nuclear bodies (SNBs) where it associates with the RNA-binding protein Sam68. Phosphorylation of Sam68 by Sik/BRK inhibits Sam68 RNA-binding and the ability of Sam68 to act as an HIV1 Rev cellular homologue in nuclear RNA export. Sam68 has been shown to play a positive role in promoting mitosis, and it is a member of a growing family of RNA-binding proteins called STAR (Signal Transducers and Activators of RNA). STAR proteins have been shown to regulate gene expression at both the transcriptional and posttranscriptional levels. The investigator has determined that Sik/BRK can also phosphorylate additional members of the STAR family, the Sam68-like mammalian proteins SLM1 and SLM2. The investigator hypothesizes that Sik/BRK regulates gene expression associated with intestinal epithelial differentiation and/or transformation by modifying the activities of the STAR proteins. In the work proposed, the investigator will focus on gaining a better understanding of the role of phosphorylation of RNA-binding proteins of the STAR family by Sik/BRK in normal and transformed intestinal cells. The investigator will continue to explore the biological role of Sik in transgenic mice expressing a dominant negative or myristoylated Sik protein in the intestine, and mice with a disruption of the Sik gene. Although the Sik knockout mice are viable and have no apparent intestinal phenotype, the investigator will challenge them to determine if they have altered susceptibility to agents that induce injury or tumors. These experiments will enhance our understanding of BRK/Sik signaling and the role of STAR proteins in the normal intestinal tract and in colon tumors.