Signaling mechanisms Controlling Planar Cell Polarity

描述（由申请人提供）：平面细胞极性（PCP）信号使上皮片上的细胞沿与其顶基轴正交的轴极化。我们对PCP信号传导的大部分机制理解来自果蝇的研究。然而，一系列医学上重要的发育缺陷和脊椎动物的生理过程都在它的控制之下。脊椎动物的PCP似乎保留了对PCP信号的大部分或全部控制，包括神经管闭合缺陷、多囊肾、圆锥状心脏缺陷、耳聋和逆位。PCP使皮肤和毛发发生极化，是伤口愈合和恶性细胞侵袭转移过程中定向迁移的基础（在果蝇中发现的机制），这激发了人们对果蝇中PCP研究的极大兴趣。对果蝇的研究揭示了控制PCP的模块化系统。由Fat(Ft), Dachsous（Ds）和Four-jointed（Fj）组成的“全局”模块将Fj和Ds的相反组织水平表达梯度转化为细胞间Ft-Ds异源二聚体的亚细胞不对称，因此可以将PCP与组织轴对齐。一个“核心”模块放大了分子的不对称性，将近端（梵高和普ickle）和远端（卷曲的，凌乱的[Dsh]）蛋白质定位到细胞的相对两侧，并协调相邻细胞之间的极性。对分子不对称的形态学反应是组织特异性的。我们已经确定了将这些模块串联起来的机制，并由此揭示了一个迷人的细胞生物学机制。全局组分Ft和Ds通过新颖的结态超微结构，组织和连接极化的顶端微管（mt）阵列，作为Dsh定向运输的底物，从而向核心模块引入定向偏置。Dsh的定向运输打破了对称，使核心蛋白极化偏倚。一个悖论是观察到的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并不守恒。我们发现PCP核心成分Pk的Prickle（Pk）或Spiny-legs（single）异构体的优势控制了这些组织中的梯度解释，通过决定梯度依赖MT的方向，从而决定MT依赖的Dsh运输的方向。这些结果提出了一些有趣的问题，我们将在本建议中加以解决。全局组件如何组织顶级mt ？我们假设Ft和Ds招募捕获和组织MT的蛋白质。我们将研究pk - simple如何控制Ft-Ds依赖的MT定向。我们的数据表明，Ft- Ds机制的功能部分冗余与第二个信号起源于翼缘。初步数据表明，Wnt4也是通过组织极化的MTs来充当另一个信号。这个信号是如何起作用的？一旦MTs被确定，我们希望了解Dsh囊泡的产生是否与这些结构直接相关，并研究内化和诱导的信号

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.