MIM regulates Shh target gene expression in tumors

描述（由申请人提供）：该项目的长期目标是了解不受调节的上皮细胞增殖和侵袭如何导致癌变。Sonic hedgehog （Shh）信号控制着许多器官祖细胞的增殖和迁移，不受控制的Shh靶基因诱导可促进25%的人类癌症的生长和侵袭，包括肺癌、乳腺癌、前列腺癌、胰腺癌以及成神经管细胞瘤和基底细胞癌。虽然Gli家族转录因子介导Shh的转录作用，但在正常和致癌环境下控制Gli转录输出和Shh依赖的迁移和侵袭的机制仍然知之甚少。包括融合抑制因子（Sufu）和Smoothened在内的Shh信号成分已被证明集中在初级纤毛上，这是一种基于微管的动态信号细胞器。初级纤毛存在于大多数哺乳动物细胞中，Shh信号成分集中在纤毛上，以调节Gli3的裂解和Gli1/2的激活。纤毛的缺失导致Shh信号缺陷和各种发育缺陷和疾病，从某些类型的视网膜变性和脱发到多囊肾/肝脏疾病和Bardet-Biedl综合征。我们已经确定了一个新的Shh通路成员，转移缺失（MIM），这是一种调节膜动力学的bar结构域蛋白，其水平在各种上皮癌中发生改变，并与乳腺癌的预后呈负相关。到目前为止，我们已经确定，在许多细胞类型中，Shh靶基因的诱导需要MIM，并且MIM与肿瘤抑制因子Sufu （Shh信号的主要负调节因子）和Gli癌基因合作，以总结Shh介导的上皮细胞增殖和侵袭。此外，MIM是初级纤毛形成所必需的。我们的工作假设是，MIM通过促进原发性纤毛形成和拮抗Sufu来调节肿瘤中Shh靶基因的表达。本研究旨在结合生物化学、细胞生物学和遗传技术：1)确定MIM在纤毛发生过程中调节膜动力学的机制；2)确定初级纤毛中MIM依赖性的Sonic hedgehog信号通路增强的机制。资助这项研究将使我们能够深入了解Shh介导的肿瘤生长和侵袭以及Shh信号在纤毛相关疾病中的作用。

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand how unregulated epithelial proliferation and invasion leads to carcinogenesis. Sonic hedgehog (Shh) signaling controls the proliferation and migration of progenitor cells of many organs, and uncontrolled Shh target gene induction promotes growth and invasion of 25% of human cancers including lung, breast, prostate, pancreatic, as well as medulloblastoma and basal cell carcinoma. While the Gli family of transcription factors mediates the transcriptional effects of Shh, the mechanism for controlling Gli transcriptional output and Shh-dependent migration and invasion during normal and oncogenic contexts remain poorly understood. Shh signaling components including Suppressor of fused (Sufu) and Smoothened have been shown to concentrate at the primary cilia, a dynamic microtubule-based signaling organelle. Primary cilia are found on most mammalian cells and Shh signaling components concentrate at the cilia in order to regulate Gli3 cleavage and Gli1/2 activation. Loss of cilia leads to defects in Shh signaling and a variety of developmental defects and disorders that range from certain types of retinal degeneration and hair loss to polycystic kidney/liver disease and Bardet-Biedl syndrome. We have identified a novel Shh pathway member, Missing in Metastasis (MIM), a BAR-domain protein that regulates membrane dynamics and whose levels are altered in a variety of epithelial cancers and negatively correlates with outcome in breast cancer. So far, we have established that MIM is required for Shh target gene induction in many cell types and cooperates with the tumor suppressor Sufu, a major negative regulator of Shh signaling, and the Gli oncogene to recapitulate Shh-mediated epithelial proliferation and invasion. In addition, MIM is required for primary cilia formation. Our working hypothesis is that MIM functions to regulate Shh target gene expression in tumors by promoting primary cilia formation and antagonizing Sufu. This proposal seeks to utilize a combination of biochemical, cell biological, and genetic techniques to: 1) Determine the mechanism by which MIM regulates membrane dynamics during ciliogenesis and 2) Determine the mechanism of MIM-dependent potentiation of Sonic hedgehog signaling at the primary cilium. Funding this fellowship will allow us to gain insight into Shh-mediated tumor growth and invasion and Shh signaling in cilia-related disorders.