REGULATING GLI FUNCTION IN HAIR FOLLICLE PROGENITORS

描述（由申请人提供）：尽管其结构多样性，但上皮器官如脊椎动物毛发在器官自我更新期间使用Sonic hedgehog（Shh）信号系统来扩增多能祖细胞。通过Gli家族转录因子介导的Shh信号传导在人类发育中起着至关重要的作用，其不适当的通路活性与各种人类出生缺陷和高达25%的人类癌症相关。祖细胞如何接收精确的Shh信号强度，而不被转化，仍然知之甚少。我们实验室的工作支持这样的假设，即毛囊祖细胞中的细胞内在Shh靶基因诱导是由周围基质细胞的特异性信号调节的。我们的研究结果指出，两个细胞内在的机制，调节Gli活性和Shh靶基因诱导上皮细胞：Gli蛋白破坏的调节，并通过辅助转录因子的存在下，Gli活性的调节转移（MIM）。我们已经证明，祖细胞增殖依赖于上皮Gli蛋白的积累。Gli通过两种不同的保守破坏信号（降解决定子）以蛋白酶体依赖性方式被破坏;去除这些降解决定子可稳定GN 1并迅速加速小鼠中的祖细胞增殖和BCC。我们还表明MIM是Shh信号传导所需的，并通过与Gli和肿瘤抑制因子融合抑制因子形成复合物来介导Shh依赖性生长和侵袭。该提案的目标是更深入地了解控制Gli蛋白稳定性和活性的上皮信号输入。我们将：1）通过定义每个降解决定子对体内Gli稳定性和活性的贡献并鉴定调节Gli蛋白稳定性的信号传导途径的分子组分来阐明卵泡祖细胞中Gli破坏的机制; 2）通过检查Shh途径不同状态下的MIM活性，确定MIM拮抗哪种Sufu活性，并表征MIM与之相互作用的腐乳蛋白表面; 3）通过确定Gli 3是否是体内主要的MIM调节剂，确定祖细胞中对MIM的需求，确定MIM水平如何影响Sufu依赖性毛发祖细胞增殖，并确定MIM和腐乳如何影响稳定的Gli 1活性。这项工作的前提是，了解Gli功能的调节将导致对hedgehog信号传导的新见解，目标是皮肤再生和上皮肿瘤的新疗法。

DESCRIPTION (provided by applicant): Despite their architectural diversity, epithelial organs such as the vertebrate hair use the Sonic hedgehog (Shh) signaling system to expand multipotent progenitor cells during organ self-renewal. Shh signaling, mediated through the Gli family of transcription factors, plays a crucial role in human development with inappropriate pathway activity associated with a variety of human birth defects and up to 25% of human cancers. How progenitor cells receive precise Shh signal strength, without becoming transformed, remains poorly understood. Work from our lab support the hypothesis that cell-intrinsic Shh target gene induction in hair follicle progenitors is regulated by specific signals from the surrounding stromal cells. Our results point to two cell-intrinsic mechanisms that regulate Gli activity and Shh target gene induction in the epithelium: regulation of Gli protein destruction, and regulation of Gli activity through the presence of the accessory transcription factor Missing in Metastasis (MIM). We have demonstrated that progenitor proliferation depends on epithelial Gli protein accumulation. Gli is destroyed in a proteasome-dependent manner through two distinct, conserved destruction signals (degrons); removal of these degrons stabilizes GN1 and rapidly accelerates progenitor proliferation and BCCs in mice. We have also shown that MIM is required for Shh signaling and mediates Shh- dependent growth and invasion by forming complexes with Gli and the tumor-suppressor, Suppressor of Fused. The goal of this proposal is to gain a deeper understanding of the epithelial signaling inputs that control Gli protein stability and activity. We will: 1) Elucidate the mechanisms of Gli destruction in follicle progenitors by defining the contribution of each degron to Gli stability and activity in vivo and identifying the molecular components of signaling pathways that regulate Gli protein stability; 2) Determine how MIM antagonizes Suppressor of Fused by examining MIM activity in different states of the Shh pathway, determining which Sufu activity MIM antagonizes, and characterizing the Sufu protein surface with which MIM interacts; 3) Determine the impact of Gli regulators on murine hair follicle progenitors by ascertaining whether Gli3 is the major MIM regulator in vivo, determining the requirements for MIM in progenitor cells, determining how MIM levels impact Sufu-dependent hair progenitor proliferation, and determine how MIM and Sufu affect stabilized Gli1 activity. This effort is based on the premise that understanding the regulation of Gli function will lead to new insights into hedgehog signaling, with a goal toward new therapeutics for skin regeneration and epithelial tumors.