Ceramide metabolism and the regulation of TGF-beta receptor signaling to control metastasis

总结 转化生长因子β受体I/II型（T β RI/II）信号在质膜上被激活 (PM)通过配体结合，诱导Smad 3/4依赖性（典型）或独立的细胞迁移，侵袭 和/或转移。当Smad 3/4激活时，Smad 7结合并抑制T β RI/II信号传导。初级纤毛 PM突起，介导细胞间通讯和迁移/侵袭，而不影响细胞运动性 通过激活各种信号通路，如音速刺猬（Shh）。神经酰胺是一种具有生物活性的鞘脂 具有肿瘤抑制信号传导功能，神经酰胺合酶4（CerS 4）产生长链C18/20- 神经酰胺然而，神经酰胺代谢、Smad 7募集和T β RI/II之间的任何机制联系， 在初级纤毛膜上用于调节肿瘤转移的信号传导仍然未知。基于 我们的新的和未发表的初步数据，我们设计了这个应用程序来测试一个新的假设， CerS 4/神经酰胺通过Smad 7选择性抑制初级纤毛膜上的T β RI/II运输和信号传导 以调节细胞迁移、侵袭和/或转移。提出了以下具体目标： 定义神经酰胺通过Smad 7调节T β RI/II信号传导的机制;目的2）确定 神经酰胺/Smad 7抑制复合物调节T β RI/II向初级纤毛运输的机制;和 目的3）探讨初级纤毛T β RI/II信号转导诱导肿瘤的下游机制 CerS 4/神经酰胺/Smad 7轴的改变可导致肿瘤转移。总的来说，根据我们在以下方面的专业知识， 癌症信号传导和脂质代谢，我们处于独特的地位，开发新的机制为基础的 在初级纤毛中选择性靶向/抑制T β RI/II信号传导的策略， 肿瘤转移而不影响TGF-β信号传导的典型功能（降低一般毒性），使用 创新的分子/药理学工具、遗传模型和临床标本。

SUMMARY Transforming growth factor beta receptor type I/II (TßRI/II) signaling is activated on the plasma membrane (PM) by ligand binding, inducing Smad3/4-dependent (canonical) or independent cell migration, invasion and/or metastasis. While Smad3/4 activates, Smad7 binds and inhibits TßRI/II signaling. Primary cilia are protrusions of PM that mediate cell-to-cell communication and migration/invasion without affecting cell motility by activating various signaling pathways such as sonic hedgehog (Shh). Ceramide is a bioactive sphingolipid with tumor suppressive signaling functions, and ceramide synthase 4 (CerS4) generates long chain C18/20- ceramide. However, any mechanistic link between ceramide metabolism, Smad7 recruitment and TßRI/II signaling at the primary cilium membrane for the regulation of tumor metastasis remains unknown. Based on our novel and unpublished preliminary data, we designed this application to test a novel hypothesis that CerS4/ceramide inhibits TßRI/II trafficking and signaling selectively at the primary cilia membrane via Smad7 to modulate cell migration, invasion and/or metastasis. The following Specific Aims are proposed: Aim 1) Define the mechanisms by which ceramide regulates TßRI/II signaling by Smad7; Aim 2) Determine the mechanisms by which ceramide/Smad7 inhibitory complex regulates TßRI/II trafficking to the primary cilia; and Aim 3) Dissect the downstream mechanism by which TßRI/II signaling at primary cilia induces tumor metastasis in response to alterations of the CerS4/ceramide/Smad7 axis. Overall, based on our expertise in cancer signaling and lipid metabolism, we are uniquely positioned to develop novel mechanism-based strategies for targeting/inhibiting TßRI/II signaling selectively in primary cilium, which then will help attenuate tumor metastasis without affecting canonical functions of TGF-ß signaling (reducing general toxicity), using innovative molecular/pharmacologic tools, genetic models, and clinical specimens.