Epithelial niche regulation of intestinal stem cell division in Drosophila

 描述(申请人提供)：这项建议旨在破译新发现的畸形-疣-约克通路在果蝇上皮龛中作用于肠道干细胞(ISC)分裂的调节机制。组织干细胞和癌症干细胞可以根据环境转换到更高的增殖状态，但其机制在很大程度上尚不清楚。尽管哺乳动物ISC生物学近年来取得了巨大的进展，但哺乳动物胃肠道的复杂性为理解ISC分裂的生态位调控设置了强大的障碍。果蝇中肠具有相对简单的细胞结构，在正常和致病条件下，中肠ISCs是唯一能补充该组织中不同细胞类型的有丝分裂细胞。我们已经发现了Ste20激酶畸形在分化被称为肠母细胞的前体细胞以影响ISC分裂方面的一个新的作用。畸形与疣相互作用，负调控转录共激活因子York kie，促进JAK-STAT途径配体Upd3的产生，促进ISC增殖。我们还发现，哺乳动物同系物MAP4K4与LATS相互作用，抑制YAP。因此，果蝇畸形-疣-约克和哺乳动物MAP4K4-LATS-YAP代表了一种新的、保守的调节组织动态平衡的机制。这项建议的具体目的是：1.确定畸形-疣信号复合体的性质。我们将测试畸形是否直接将疣作为底物磷酸化，以及畸形-疣复合体是否由其他信号成分组成。2.确定上游的蛋白酪氨酸酶1是否通过苏氨酸194残基的磷酸化而激活畸形。我们的初步结果表明，畸形蛋白的T194是磷酸化的，实验旨在证明T194被陶氏蛋白1或其他激酶磷酸化，对肠道内环境稳定是必不可少的。3.研究调节肠成纤维细胞畸形活动的生理学过程。我们将检验这一假设，即肠成纤维细胞和邻近细胞之间的物理相互作用会影响畸形活动，进而调节适量Upd3的产生，以优化肠道组织的维护。这些目标的成功实现将揭示上皮细胞生态位调节ISC分裂的一些机制，并将为人类胃肠道炎症性疾病和癌症的治疗策略提供见解。

 DESCRIPTION (provided by applicant): This proposal aims at deciphering the mechanism by which the newly discovered Misshapen-Warts-Yorkie pathway acts in the epithelial niche to regulate intestinal stem cell (ISC) division in Drosophila. Tissue stem cells, as well as cancer stem cells, can transition into higher proliferative states depending on the environment but the mechanism is largely unknown. Although mammalian ISC biology has gained tremendous progress in recently years, the complexity of the mammalian gastrointestinal tract posts strong barriers to understand niche regulation of ISC division. The Drosophila midgut has a relatively simple cellular organization, and midgut ISCs are the only mitotic cells that replenish the different cell types in this tissue under normal and pathogenic conditions. We have uncovered a novel role of the Ste20 kinase Misshapen functioning in differentiating precursor cells called enteroblasts to influence ISC division. Misshapen interacts with Warts to negatively regulate the transcriptional coactivator Yorkie, which promotes the production of the JAK-STAT pathway ligand Upd3 to increase ISC proliferation. We have also found that the mammalian homologue MAP4K4 interacts with LATS to inhibit YAP. Therefore, the Drosophila Misshapen-Warts-Yorkie and mammalian MAP4K4- LATS-YAP represent a new, conserved mechanism to regulate tissue homeostasis. The specific aims of this proposal are: 1. Determine the nature of the Misshapen-Warts signaling complex. We will test whether Misshapen directly phosphorylates Warts as a substrate and whether the Misshapen-Warts complex consists of other signaling components. 2. Determine whether the upstream kinase Tao1 activates Misshapen via phosphorylation at the threonine 194 residue. Our preliminary results show that T194 of Misshapen is phosphorylated and experiments are designed to prove that T194 phosphorylation by Tao1, or other kinases, is essential for intestinal homeostasis. 3. Investigate the physiologica processes that regulate Misshapen activity in enteroblasts. We will test the hypothesis that the physical interaction between enteroblasts and neighboring cells affects Misshapen activity, which in turn regulates the production of the appropriate amount of Upd3 for optimal intestinal tissue maintenance. The successful accomplishment of these aims will unveil some of the mechanisms by which the epithelial niche regulates ISC division and should provide insights into therapeutic strategies for human GI inflammatory diseases and cancer.