The Hippo pathway controls polar cell fate through Notch signaling during Drosophila oogenesis

During Drosophila oogenesis, the somatic follicle cells form an epithelial layer surrounding the germline cells to form egg chambers. In this process, follicle cell precursors are specified into polar cells, stalk cells, and main-body follicle cells. Proper specification of these three cell types ensures correct egg chamber formation and polarization of the anterior–posterior axis of the germline cells. Multiple signaling cascades coordinate to control the follicle cell fate determination, including Notch, JAK/STAT, and Hedgehog signaling pathways. Here, we show that the Hippo pathway also participates in polar cell specification. Over-activation of yorkie (yki) leads to egg chamber fusion, possibly through attenuation of polar cell specification. Loss-of-function experiments using RNAi knockdown or generation of mutant clones by mitotic recombination demonstrates that reduction of yki expression promotes polar cell formation in a cell-autonomous manner. Consistently, polar cells mutant for hippo (hpo) or warts (wts) are not properly specified, leading to egg chamber fusion. Furthermore, Notch activity is increased in yki mutant cells and reduction of Notch activity suppresses polar cell formation in yki mutant clones. These results demonstrate that yki represses polar cell fate through Notch signaling. Collectively, our data reveal that the Hippo pathway controls polar cell specification. Through repressing Notch activity, Yki serves as a key repressor in specifying polar cells during Drosophila oogenesis.     

Hippo信号通路在果蝇遗传学研究中的发现与扩展

Hippo信号通路的发现是利用果蝇遗传学研究重大生物学问题的又一里程碑式的贡献。大量研究表明,Hippo信号通路像早期发现的其他信号通路一样,也在众多的生理与病理过程中扮演着关键角色,如控制器官尺寸和癌症发生。迄今为止,Hippo信号通路的研究过程主要经历了3个阶段：第一,Hippo信号通路的遗传学发现及其核心因子的筛选与鉴定;第二,Hippo信号通路的调控机制研究;第三,Hippo信号通路的多样性生理学功能。现阶段正是研究Hippo信号通路的上游调控和各种功能的阶段,如细胞骨架、机械张力、营养的调控,功能涉及细胞增殖调控、干细胞生物学和免疫等方面。本文按时间顺序综述了在果蝇遗传学研究中Hippo信号通路的发现与扩展过程,并对未来的研究方向进行了展望。     

Hippo信号通路在肠道稳态、再生及癌变过程中的作用及机制

肠道是人体最重要的消化器官之一,急慢性肠炎、肠道肿瘤等肠道疾病严重威胁着人类的健康,因此对肠道生理及病理机制的研究具有重要的科学意义及临床价值。Hippo信号通路在细胞增殖与分化、组织损伤再生、肿瘤发生和发展过程中起重要作用,参与肠道中众多生理及病理进程的调控。本文结合近年来肠道相关Hippo信号通路的研究进展,对该领域的前沿信息进行概括总结,重点阐述了Hippo信号在肠稳态、再生与癌变过程中的作用,并在此基础上展望了肠道中Hippo信号通路研究的前景及潜在的临床价值。     

Hippo pathway in intestinal homeostasis and tumorigenesis

The Hippo pathway plays a crucial role in controlling organ size by inhibiting cell proliferation and promoting cell death. Recent findings implicate that this pathway is involved in the process of intestinal regeneration and tumorigenesis. Here we summarize current studies for the function of the Hippo signaling pathway in intestinal homeostasis, regeneration and tumorigenesis, and the crosstalk between the Hippo signaling pathway and other major signaling pathways, i.e. Wnt, Notch and Jak/Stat signaling pathways in intestinal compartment.     

Hippo信号通路调控免疫细胞的功能

Hippo信号通路最初是在果蝇(Drosophila)中被发现的,是在进化上高度保守并能调控器官大小的信号转导通路。在哺乳动物多种组织器官中,Hippo信号通路的关键激酶MST1和MST2(果蝇Hippo激酶的同源分子)通过抑制下游的转录共激活分子YAP(果蝇中为Yorki)的活性来实现对细胞增殖和凋亡的调控。在这些组织器官中条件性敲除Mst1和Mst2或过表达Yap大都会造成细胞过度增殖或肿瘤的发生。近年来,随着研究的不断深入,Hippo信号通路不依赖于YAP的非经典功能也逐渐被发现。其中,Hippo信号通路多个成员在免疫系统中的调控功能逐渐成为该领域的研究热点,特别是在免疫细胞发育分化、机体自身免疫性疾病及应对病毒和细菌入侵等过程中所发挥的调控作用。本文重点阐述了Hippo信号通路在T淋巴细胞中发育、分化、活化和迁移等方面及在部分天然免疫细胞抗感染过程中的功能和调控。     

哺乳动物Hippo信号通路:肿瘤治疗的新标靶

Hippo信号通路是首次在果蝇中发现具有调节细胞增殖与凋亡作用的信号通路。最近发现果蝇Hippo信号通路的组成、分子作用机制和生物学功能在进化过程中高度保守。Hippo信号通路在胚胎发育中对细胞的生长分化、组织器官形成以及成体干细胞的维持和自稳态的保持等方面具有重要作用。同时,Hippo信号通路与Wnt信号通路、Notch信号通路等相互作用、密切联系,在肿瘤的发生、发展过程中也起到关键作用。文章综述了哺乳动物Hippo信号通路的作用机理、与其他信号通路和蛋白质因子的相互联系及与肿瘤的关系,对于肿瘤的诊断、预防和治疗具有一定的参考价值。     

Discovery of N-aryl sulphonamide-quinazoline derivatives as anti-gastric cancer agents in vitro and in vivo via activating the Hippo signalling pathway

Hippo signalling pathway plays a crucial role in tumorigenesis and cancer progression. In this work, we identified an N-aryl sulphonamide-quinazoline derivative, compound 9i as an anti-gastric cancer agent, which exhibited potent antiproliferative ability with IC₅₀ values of 0.36 μM (MGC-803 cells), 0.70 μM (HCT-116 cells), 1.04 μM (PC-3 cells), and 0.81 μM (MCF-7 cells), respectively and inhibited YAP activity by the activation of p-LATS. Compound 9i was effective in suppressing MGC-803 xenograft tumour growth in nude mice without obvious toxicity and significantly down-regulated the expression of YAP in vivo. Compound 9i arrested cells in the G2/M phase, induced intrinsic apoptosis, and inhibited cell colony formation in MGC-803 and SGC-7901 cells. Therefore, compound 9i is to be reported as an anti-gastric cancer agent via activating the Hippo signalling pathway and might help foster a new strategy for the cancer treatment by activating the Hippo signalling pathway regulatory function to inhibit the activity of YAP.     

Linc-RoR promotes proliferation,migration, and invasion via the Hippo/YAP pathway in pancreatic cancer cells

Large intergenic noncoding RNA regulator of reprogramming (Linc-RoR) was first identified as a regulator to increase the emergence of induced pluripotent stem cells through reprogramming differentiated cells and is abnormal expression in a variety of malignant tumors. However, the function of Linc-RoR in pancreatic cancer progression needs further clarification. The data from this study demonstrated that Linc-RoR knockdown suppressed cell proliferative capacity and colony formation, while Linc-RoR overexpression promoted these behaviors. In particular, Linc-RoR overexpression promoted the level of mesenchymal markers, inhibited the expression of epithelial markers, as well as enhanced pancreatic cancer cells migration and invasion, whereas Linc-RoR knockdown inhibited the expression of mesenchymal markers, promoted the expression of epithelial markers, as well as weakened pancreatic cancer cells migration and invasion. Further study revealed that Linc-RoR knockdown brought about a significant fall in YAP phosphorylation and a rise in total YAP, while Linc-RoR overexpression produced the opposite results. Specifically, Linc-RoR promoted YAP in the cytoplasm into the nucleus. Taken together, we conjectured that Linc-RoR promoted proliferation, migration, and invasion of pancreatic cancer cells by activating the Hippo/YAP pathway. YAP might be an underlying target of Linc-RoR and mediate epithelial-mesenchymal transition (EMT) in pancreatic cancer (PC); thus, Linc-RoR might be a very meaningful biomarker for PC.     

WW domain interactions regulate the Hippo tumor suppressor pathway

The Hippo kinase pathway is emerging as a conserved signaling pathway that is essential for organ growth and tumorigenesis in Drosophila and mammalians. Although the signaling of the core kinases is relatively well understood, less is known about the upstream inputs, downstream outputs and regulation of the whole cascade. Enrichment of the Hippo pathway components with WW domains and their cognate proline-rich interacting motifs provides a versatile platform for further understanding the mechanisms that regulate organ growth and tumorigenesis. Here, we review recently discovered mechanisms of WW domain-mediated interactions that contribute to the regulation of the Hippo signaling pathway in tumorigenesis. We further discuss new insights and future directions on the emerging role of such regulation.