细胞周期中纤毛动态变化调控机制及其功能的研究

The primary cilium is an antenna-like organelle that projects from the apical surface of most vertebrate cells. It consists of a basal body，a axoneme, and is sheathed by a signaling receptor-rich ciliary membrane. The primary cilium is structurally dynamic during the cell cycle. It is assembled immediately after mitosis and maintained in resting (G0 phase) cells; once the resting cell is committed to recycle, the primary cilium starts to disassemble until it disappears before entry into mitosis. However, how these processes are coordinated with the cell cycle remain largely unknown. Since many kinds of receptors are localized at the cilium membrane, the primary cilium plays pivotal roles in mediating signal transduction for the cell, and regulating the balance between proliferation and differentiation. Although deregulation of the primary cilium-mediated signaling pathways is often correlated to human diseases, it is not clear whether these pathways are also regulated by the cell cycle and are involved in the regulation of the cell cycle. Here, by means of molecular biology, cell biology, biochemistry, we tend to illuminate the mechanism(s) governing the cilium dynamics in the cell cycle and the relationship between the primary cilium-mediated signaling pathways and the cell cycle progression. These studies will deepen our understandings about the regulation of the cell cycle, proliferation and differentiation of the cell, and the activity of the primary cilium-mediated signaling pathways.

初级纤毛是一种直立组装于大多数脊椎动物细胞上表面的“天线”样细胞器，其主要由基体、轴丝及富含信号通路受体的纤毛膜构成。初级纤毛的结构在细胞周期中是动态变化的：其在有丝分裂期（M）退出时立即组装并在静止期（G0）得以维持；在由G0重回细胞周期时开始去组装直至M开始之前完全去组装。然而该动态变化的调控机制目前并不清楚。纤毛膜富集多种信号通路的受体，因而在细胞的信号转导、增殖与分化的平衡调控中具有重要作用。现有研究显示纤毛介导的信号通路的异常活化与人类疾病的发生高度相关。而这些信号通路是否同样受到细胞周期的调控、其与细胞周期运转是否存在相互关联，目前也不清楚。本立项拟采用分子生物学、细胞生物学、生物化学等实验手段，阐明细胞周期中纤毛动态变化及其功能的调控机制。这些研究将为加深我们对细胞周期调控、细胞增殖与分化及信号通路活性调控机制的认识提供重要的理论基础。

初级纤毛是一种存在于大多数脊椎动物细胞上表面的“天线”样细胞器，其主要由基体、轴丝及纤毛膜构成。初级纤毛的结构与细胞周期运行密切相关，即主要存在于间期而在分裂期被去组装。人们已知纤毛结构的异常会加速或阻碍细胞周期运行，但其与细胞周期间相互调控的机制有待阐明。纤毛膜上富集了多种信号通路的受体蛋白，因此纤毛介导了包括Hedgehog、Wnt、TGFβ、PDGFR、GPCR、RPTK以及钙离子通路在内的多种信号转导，具有重要的生理学功能。尽管人们已经发现了大量与纤毛病发生相关的基因突变，这些认识还大多停留在现象描述的层面。因此，阐明这些突变基因及其蛋白产物引发纤毛病的分子机制，已成为本领域研究的重点和难点。..本项目以分子生物学、生物化学、细胞生物学、高级显微镜学等为研究手段，主要回答了细胞G2期纤毛去组装调控机制、G2期Hedgehog通路对细胞周期负反馈调控机制、以及G0期纤毛介导的Hedgehog通路活化机制的三个科学问题。结果证明：在G2期，细胞周期激酶Plk1通过磷酸化Dzip1蛋白减弱后者的中心体卫星定位，进而中止BBSome蛋白复合体的中心体卫星和纤毛定位，从而在G2期抑制纤毛组装并关闭依赖于BBSome的有关信号转导。Plk1还通过磷酸化Hedgehog通路下游蛋白Gli1使后者的细胞核转运受到抑制，从而在G2期关闭Hedgehog通路。在G0期，PKA激酶通过磷酸化Inversin蛋白促进Smo蛋白在Hedgehog通路活化时向纤毛定位，进而激活下游信号通路。Smo基因致癌突变的蛋白产物通过增强与Inversin的相互作用获得纤毛定位并引起Hedgehog通路的异常活化，成为基底细胞癌发生的分子机制之一。..细胞周期调控和细胞信号转导都是细胞生物学的主要研究内容，也是生命科学领域的重要研究对象。本项目的研究成果揭示了一种新的细胞周期调控纤毛去组装的分子机制，证明了细胞周期对Hedgehog通路存在抑制性调控作用，还阐明了Hedgehog信号转导起始过程中相关蛋白纤毛定位的重要分子机制。这些成果不仅在知识层面加深了人们对纤毛功能和细胞周期调控的认识，还在应用层面为人们寻找Hedgehog通路相关癌症的治疗靶点提供了新的思路。