Mechanism of Hedgehog Signal transduction across the plasma membrane

描述(由申请人提供)：Hedgehog(HH)分泌信号蛋白家族在脊椎动物和无脊椎动物的许多发育过程中控制细胞的生长和模式。HH信号活性的错误调节与包括癌症在内的许多人类疾病有关。我的实验室的长期目标是了解HH是如何控制细胞生长和构图的，以及HH信号是如何被转导以产生不同的发育结果的。HH信号接收系统由两个跨膜蛋白组成：一个是作为HH受体的十二跨膜蛋白补丁(PTC)，另一个是作为必需的信号转导的七跨膜蛋白平滑(Smo)。我们发现蛋白激酶A(PKA)和酪蛋白激酶1(CK1)通过磷酸化Smo正向调节HH途径，导致Smo在细胞表面聚集和构象变化到活跃状态。此外，我们还发现HH诱导的磷酸化促进了Smo与细胞内信号复合体的相互作用。我们还发现哺乳动物Smo在Shh的反应下经历了构象变化，Shh受一组不同的激酶调控。这些和其他发现揭示了果蝇和脊椎动物HH信号机制之间有趣的相似之处，并为剖析这两个系统中的HH信号机制提供了新的工具和假设。在这项研究中，我们将研究多个Smo磷酸化事件在HH信号转导中的作用和调节(Aim1)，确定磷酸化如何调节Smo细胞表面的表达(Aim 2)，确定Smo如何激活细胞内信号复合体(Aim 3)，并探讨Smo磷酸化在Shh途径激活中的功能和机制(Aim 4)。这项拟议的研究将提供对HH信号转导机制的更深层次的理解，并为HH信号如何在果蝇和脊椎动物系统中转化为不同的发育结果提供新的线索。由于Smo活性和HH信号的异常升高与许多人类癌症有关，而Smo是药物开发的主要治疗靶点，我们的研究可能为改善HH途径相关癌症的诊断和治疗提供新的途径。 公共卫生相关性：HH途径活性调节不当与包括癌症在内的许多人类疾病有关。因此，了解本项目提出的HH信号机制，可能为改善癌症的诊断和治疗提供新的途径。

DESCRIPTION (provided by applicant): The Hedgehog (Hh) family of secreted signaling proteins governs cell growth and patterning in numerous developmental processes in both vertebrates and invertebrates. Misregulation of Hh signaling activity has been implicated in many human disorders including cancer. The long-term goal of my laboratory is to understand how Hh controls cell growth and patterning, and how the graded Hh signals are transduced to elicit different developmental outcomes. The Hh signal reception system consists of two transmembrane proteins: a twelve-transmembrane protein Patched (Ptc) as the Hh receptor and a seven-transmembrane protein Smoothened (Smo) as the obligatory signal transducer. We have discovered that protein kinase A (PKA) and casein kinase 1 (CK1) positively regulate the Hh pathway by phosphorylating Smo, leading to its cell surface accumulation and conformational change to an active state. In addition, we found that Hh-induced phosphorylation promotes Smo interaction with the intracellular signaling complexes. We have also found that mammalian Smo undergoes a conformational change in response to Shh, which is regulated by a distinct set of kinases. These and other findings unveil interesting parallels between Drosophila and vertebrate Hh signaling mechanisms and provide new tools and hypotheses to dissect the Hh signaling mechanism in both systems. In this proposal, we will investigate the function and regulation of multiple Smo phosphorylation events in Hh signaling (Aim1), determine how phosphorylation regulates Smo cell surface expression (Aim 2), determine how Smo activates the intracellular signaling complex (Aim 3), and investigate the function and mechanism of Smo phosphorylation in Shh pathway activation (Aim 4). The proposed study should provide deeper understanding of the Hh signal transduction mechanism and shed new light into how graded Hh signals are translated into different developmental outcomes in both Drosophila and vertebrate systems. As abnormal elevation of Smo activity and Hh signaling contributes to many human cancers and Smo is a primary therapeutic target for drug development, our study may provide new avenues for improving diagnosis and therapeutics of Hh pathway related cancers. PUBLIC HEALTH RELEVANCE: Misregulation of Hh pathway activity has been implicated in many human disorders including cancer. Hence, understanding the Hh signaling mechanisms, as proposed by this project, may provide new avenues for improving diagnosis and therapeutics of cancer.