Molecular Mechanisms of Mammalian Hedgehog Signal Transduction

描述(申请人提供)：本研究的长期目标是了解哺乳动物Hedgehog(HH)信号转导的分子机制。HH信号异常与多种人类癌症和出生缺陷有关。最近的证据表明，HH信号的某些方面在无脊椎动物和脊椎动物之间并不保守。不仅脊椎动物中的一些主要参与者的角色发生了变化，而且它们的遗传相互作用和信号转导模式也发生了改变。此外，初级纤毛似乎在哺乳动物而不是果蝇的HH信号中起主要作用。这些发现突显了直接阐明哺乳动物HH途径组分的功能对于进一步了解脊椎动物HH信号转导的重要性。这项建议集中在哺乳动物HH信号转导中的一个关键角色-融合抑制因子(Sufu)，并将定义Sufu在调节Gli转录因子功能方面的机制，Gli转录因子是哺乳动物发育过程中HH信号的唯一中介。我们提出了以下具体目标：1)明确Sufu在控制Gli2纤毛定位中的作用。2)阐明Sufu介导的Gli3蛋白稳定的分子机制。3)描述了初级纤毛在Sufu或SPOP介导的Gli蛋白功能中的需求。4)验证Sufu与Kinesin家族成员Kif7在调节哺乳动物HH信号中相互作用的假说。将采用基于细胞的分析、使用基因敲除小鼠的遗传学研究和蛋白质生物化学相结合的方法来解决这些中心问题。这些研究将为哺乳动物HH信号如何在反应细胞中传递提供新的机械性见解7.公共卫生相关性：Hedgehog(HH)信号异常与癌症和出生缺陷有关。阐明HH信号是如何传导的，对于理解HH相关疾病的潜在机制以及确定诊断和合理治疗的潜在靶点至关重要。

DESCRIPTION (provided by applicant): The long-term goal of this study is to understand the molecular mechanism of mammalian Hedgehog (Hh) signal transduction. Aberrant Hh signaling has been associated with various human cancers and birth defects. Recent evidence indicates that several aspects of Hh signaling are not conserved between invertebrates and vertebrates. Not only have the roles of some of the main players changed in vertebrates, but also their genetic interactions and the mode of signal transduction have been modified. Further, primary cilia appear to play a major role in mammalian and not Drosophila Hh signaling. These findings highlight the importance of elucidating the functions of mammalian Hh pathway components directly in order to further understand vertebrate Hh signal transduction. This proposal focuses on one critical player in mammalian Hh signal transduction, Suppressor of Fused (Sufu), and will define the mechanism of Sufu in regulating the functions of Gli transcription factors, the sole mediators of Hh signaling during mammalian development. We propose the following specific aims: 1) Define the role of Sufu in controlling ciliary localization of Gli2. 2) Elucidate the molecular mechanism of Sufu-mediated Gli3 protein stabilization. 3) Delineate the requirement of primary cilia in Sufu- or SPOP-mediated Gli protein function. 4) Test the hypothesis that Sufu interacts with Kif7, a kinesin family member, in modulating mammalian Hh signaling. A combination of cell-based assays, genetic studies using knockout mice and protein biochemistry will be employed to address these central issues. These studies will provide new mechanistic insights into how the mammalian Hh signal is transduced in responsive cells 7. PUBLIC HEALTH RELEVANCE: Aberrant Hedgehog (Hh) signaling is associated with cancers and birth defects. Elucidating how the Hh signal is transduced is critical to understanding the underlying mechanisms of Hh-related diseases as well as identifying potential targets for diagnosis and rational therapies.