Dissecting the Signaling Mechanisms of Smoothened

描述（申请人提供）：Hedgehog （Hh）信号转导通路在细胞发育过程中的模式场中起重要作用，并且在癌症中经常被激活。不适当的Hh信号是基底细胞癌（人类最常见的癌症）、髓母细胞瘤（儿童最常见的恶性脑肿瘤）和横纹肌肉瘤的病因，其中通路激活与预后不良相关。Hh也与肺、乳腺和前列腺的散发性肿瘤有关。因此，Hh通路已成为一个有吸引力的治疗靶点；对Hh信号的特异性抑制可能对这些癌症有效，而不会引发与传统化疗相关的不良副作用。为了设计和应用Hh特异性治疗方法，明确Hh信号转导的调控机制和信号成分至关重要。因此，本提案的目标是剖析控制Hh通路诱导的机制事件，并确定促进下游信号传导的新型效应物。我们将以果蝇黑腹果蝇为模型系统，通过Hh信号转导的分子和功能分析来实现这些目标。我们的研究主要集中在阐明Hh通路的关键信号换能器Smoothened的信号机制和下游效应。Smoothened是g蛋白偶联受体（GPCR）超家族的成员。因此，本研究包括三个特定目的，旨在更好地表征Smoothened GPCR信号传导活性：1)表征细胞外GPCR结构特征，促进Hh调控Smoothened信号传导；2)鉴定Smoothened中控制信号传导的GPCR功能域；3)绘制Smoothened下游功能的g蛋白效应网络。拟议的研究将增强我们对Hh信号如何启动和转导的理解，并可能通过识别Smoothened和Hh级联中的“压力点”揭示新的治疗靶点。

DESCRIPTION (provided by applicant): The Hedgehog (Hh) signal transduction pathway plays an essential role in patterning fields of cells during development, and is frequently activated in cancer. Inappropriate Hh signaling is causative in basal cell carcinoma, the most common cancer in humans, medulloblastoma, the most common malignant brain tumor in children, and rhabdomyosarcoma, where pathway activation correlates with poor prognosis. Hh has also been implicated in sporadic tumors of the lung, breast and prostate. Consequently, the Hh pathway has emerged as an attractive therapeutic target; specific inhibition of Hh signaling will likely have efficacy against these cancers without triggering the undesirable side effects associated with conventional chemotherapy. To design and employ Hh-specific therapies, a clear understanding of the regulatory mechanisms and signaling components controlling physiological Hh signal transduction is of paramount importance. Accordingly, the goals of this proposal are to dissect mechanistic events governing Hh pathway induction and to identify novel effectors facilitating downstream signaling. We will achieve these goals through molecular and functional analysis of Hh signal transduction using the fruit fly Drosophila melanogaster as our model system. Our studies primarily focus on elucidating the signaling mechanisms and downstream effectors of Smoothened, the critical signal transducer of the Hh pathway. Smoothened is a member of the G-protein coupled receptor (GPCR) superfamily. As such, this study includes three Specific Aims designed to better characterize Smoothened GPCR signaling activity: 1) To characterize the extracellular GPCR structural features that facilitate Hh- regulated Smoothened signaling, 2) To identify GPCR functional domains in Smoothened that govern signaling and 3) To map the G-protein effector network functioning downstream of Smoothened. The proposed studies will enhance our understanding of how the Hh signal is initiated and transduced, and may reveal novel therapeutic targets through identifying "pressure points" on Smoothened and within the Hh cascade.