Epithelial niche regulation of intestinal stem cell division in Drosophila

 描述（由申请人提供）：本提案旨在破译新发现的Misshapen-Warts-Yorkie通路在上皮生态位中调节果蝇肠干细胞（ISC）分裂的机制。组织干细胞以及癌症干细胞可以根据环境转变为更高的增殖状态，但其机制在很大程度上尚不清楚。尽管近年来哺乳动物ISC生物学已经取得了巨大的进展，但哺乳动物胃肠道的复杂性给理解ISC分裂的生态位调控带来了很大的障碍。果蝇中肠具有相对简单的细胞组织，并且中肠ISCs是在正常和致病条件下补充该组织中不同细胞类型的唯一有丝分裂细胞。我们已经发现了Ste 20激酶Misshapen在分化称为肠母细胞的前体细胞以影响ISC分裂中发挥作用的新作用。Misshapen与Warts相互作用以负调节转录辅激活因子Yorkie，其促进JAK-STAT途径配体Upd 3的产生以增加ISC增殖。我们还发现哺乳动物同源物MAP 4 K4与LATS相互作用以抑制雅普。因此，果蝇Misshapen-Warts-Yorkie和哺乳动物MAP 4K 4-LATS-YAP代表了一种新的、保守的调节组织稳态的机制。该提案的具体目标是：1.确定畸形疣信号复合物的性质。我们将测试Misshapen是否直接磷酸化疣作为底物，以及Misshapen-Warts复合物是否由其他信号成分组成。2.确定上游激酶Tao 1是否通过苏氨酸194残基的磷酸化激活Misshapen。我们的初步结果表明，畸形的T194是磷酸化的，实验旨在证明T194磷酸化的Tao 1，或其他激酶，是必不可少的肠道内稳态。3.研究调节肠母细胞Misshapen活性的生理过程。我们将检验这样一个假设，即成肠细胞和邻近细胞之间的物理相互作用会影响Misshapen的活性，而Misshapen的活性反过来又会调节适量Upd 3的产生，以实现最佳的肠道组织维持。这些目标的成功实现将揭示上皮小生境调节ISC分裂的一些机制，并为人类GI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.