Mechanism of Hedgehog Signal transduction across the plasma membrane

描述（由申请人提供）：分泌信号蛋白的Hedgehog（Hh）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生长和模式化。Hh信号传导活性的失调已经涉及许多人类疾病，包括癌症。我实验室的长期目标是了解Hh如何控制细胞生长和模式，以及分级Hh信号如何转导以引起不同的发育结果。Hh信号接收系统由两个跨膜蛋白组成：作为Hh受体的十二跨膜蛋白Patched（Ptc）和作为强制性信号转导子的七跨膜蛋白Smoothened（Smo）。我们已经发现蛋白激酶A（PKA）和酪蛋白激酶1（CK1）通过磷酸化Smo来正调控Hh通路，导致Smo在细胞表面积聚并构象改变为活性状态。此外，我们发现，Hh诱导的磷酸化促进Smo与细胞内信号复合物的相互作用。我们还发现，哺乳动物的Smo经历了构象变化，响应Shh，这是由一组不同的激酶调节。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，并提供了新的工具和假设来剖析这两个系统中的Hh信号机制。在这个计划中，我们将研究Hh信号中多个Smo磷酸化事件的功能和调节（Aim 1），确定磷酸化如何调节Smo细胞表面表达（Aim 2），确定Smo如何激活胞内信号复合体（Aim 3），并研究Smo磷酸化在Shh通路激活中的功能和机制（Aim 4）。拟议的研究应该提供更深入的理解Hh信号转导机制，并揭示了如何分级Hh信号转化为不同的发育结果在果蝇和脊椎动物系统。由于Smo活性和Hh信号传导的异常升高有助于许多人类癌症，并且Smo是药物开发的主要治疗靶点，我们的研究可能为改善Hh通路相关癌症的诊断和治疗提供新的途径。 公共卫生相关性：Hh通路活性的失调与包括癌症在内的许多人类疾病有关。因此，了解Hh信号传导机制，如本项目所提出的，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.