Signaling mechanisms Controlling Planar Cell Polarity

描述(由申请人提供)：平面细胞极性(PCP)信号使上皮片中的细胞沿与其顶端-基底轴垂直的轴极化。我们对PCP信号的大部分机械理解都来自于对果蝇的研究。然而，脊椎动物中一系列重要的医学发育缺陷和生理过程都在它的控制之下。脊椎动物的PCP似乎保存了PCP信号的大部分或全部控制，包括神经管闭合缺陷、多囊肾、圆锥干心脏缺陷、耳聋和内翻。PCP使皮肤和毛发极化，并在伤口愈合和恶性细胞侵袭和转移过程中进行定向迁移，这一机制在果蝇中已被发现，这激发了人们对PCP在果蝇中的研究兴趣。对果蝇的研究揭示了一个控制五氯苯酚的模块化系统。由Fat(Ft)、Dachsous(DS)和Fj(Fj)组成的‘全局’模块将相反的Fj和DS的组织水平表达梯度转化为细胞间Ft-DS异二聚体的亚细胞不对称性，因此可以将PCP与组织轴对齐。“核心”模块放大了分子的不对称性，将近端(梵高和皮刺)和远端(Frizzleed，Disheveled[Dsh])蛋白质定位到细胞的两边，并协调相邻细胞之间的极性。对由此产生的分子不对称的形态反应是组织特有的。我们已经确定了一种串联这些模块的机制，并在这样做的过程中，揭示了一种有趣的细胞生物学机制。全局组分Ft和DS通过新颖的连接超微结构，组织和拴住作为Dsh定向运输底物的极化顶端微管(MT)阵列，从而向核心模块引入定向偏置。Dsh的定向运输破坏了对称性，使核心蛋白质极化发生偏向。一个悖论是观察到全局梯度方向和核心模块极化方向之间的关系在组织之间不是保守的。我们发现，核心PCP成分PK的棘突(PK)或棘腿(SPLe)亚型的优势通过决定梯度依赖的MTS的方向，从而控制MT依赖的Dsh运输的方向，从而控制这些组织中的梯度解释。这些结果提出了一些有趣的问题，我们在这项提案中解决了这些问题。全球组件如何组织心尖MTS？我们假设Ft和DS招募捕获和组织MTS的蛋白质。我们将研究PK-SPLe是如何控制依赖于Ft-DS的MT取向的。我们的数据表明，Ft-DS机制部分冗余地发挥作用，第二个信号起源于机翼边缘。初步数据表明，WNT4也通过组织极化的MT作为另一种信号。这另一个信号是如何工作的？一旦MT被建立，我们希望了解Dsh囊泡的产生是否与这些结构直接相关，并研究内化和 分子马达的控制。最后，我们将研究E3泛素连接酶Cul1，我们已经确定它是PK功能的调节因子。

DESCRIPTION (provided by applicant): Planar Cell Polarity (PCP) signaling polarizes cells in epithelial sheets along an axis orthogonal to their apical- basal axis. Most of our mechanistic understanding of PCP signaling derives from work in Drosophila. However, a range of medically important developmental defects and physiological processes in vertebrates are under its control. PCP in vertebrates appears to conserve much or all of control of PCP signaling, including neural tube closure defects, polycystic kidneys, conotruncal heart defects, deafness and situs inversus. PCP polarizes skin and hair, and underlies directed migration during wound healing and invasion and metastasis of malignant cells the mechanism uncovered in flies, motivating considerable interest in studying PCP both in Drosophila. Studies in Drosophila reveal a modular system controlling PCP. A 'global' module comprising Fat(Ft), Dachsous(Ds) and Four-jointed(Fj) converts opposing tissue-level expression gradients of Fj and Ds into subcellular asymmetry of intercellular Ft-Ds heterodimers, and could therefore align PCP with the tissue axes. A 'core' module amplifies molecular asymmetry, localizing proximal (Van Gogh and Prickle) and distal (Frizzled, Dishevelled[Dsh]) proteins to opposite sides of the cell and coordinating polarity between neighboring cells. Morphological responses to the resulting molecular asymmetry are tissue specific. We have identified a mechanism linking these modules in series, and in so doing, revealed a fascinating cell biological mechanism. The global components Ft and Ds, via novel junctional ultrastructures, organize and tether arrays of polarized apical microtubules (MTs) that serve as substrates for directional trafficking of Dsh, thereby introducing a directional bias to the core module. Directional trafficking of Dsh breaks symmetry to bias core protein polarization. A paradox was the observation that the relationship between the direction of the global gradients and the direction of core module polarization is not conserved between tissues. We found that the predominance of the Prickle(Pk) or Spiny-legs(Sple) isoform of the core PCP component Pk controls gradient interpretation in these tissues by determining the direction of gradient dependent MTs, and thus the direction of MT dependent Dsh trafficking. These results raise a number of fascinating questions that we address in this proposal. How do the global components organize apical MTs? We hypothesize that Ft and Ds recruit proteins that capture and organize MTs. We will investigate how Pk-Sple controls Ft-Ds dependent MT orientation. Our data indicate that the Ft- Ds mechanism functions partially redundantly with a second signal originating at the wing margin. Preliminary data indicate that Wnt4 serves as this other signal, also by organizing polarized MTs. How does this other signal function? Once MTs are established, we wish to understand whether Dsh vesicle production is directly linked to these structures, and to study the signals for internalization and the control of molecular motors. Finally, we will study the E3 Ubiquitin ligase Cul1, which we have identified as a regulator of Pk function.