G PROTEIN MEDIATED CONTROL OF THE NEURONAL CYTOSKELETON

描述：(申请人摘要)神经元作为一个细胞没有竞争对手 专门从事膜结合细胞器(MBO)运输的类型 沿微管(MT)。神经元的这一独特特征是 由其独特的形态和功能特性决定的。在.期间 神经发生，例如，树突和轴突的形成需要 新生质膜蛋白和脂质在体内的持续输送 生长中的轴突。这些膜前体是囊泡中的包裹。 其表面相关的马达分子将囊泡沿MTS移动到 神经突起的远端顶端，在那里小泡与 质膜促进轴突伸长。在分化的神经元中， 轴突的维持同样依赖于MTS。因为轴突 缺乏蛋白质合成机制，但可以超过1万倍 与其发出的核周细胞的直径一样长，轴突 必须不断地提供新的驻留蛋白质来取代那些 到了那个年龄就会退化。新的轴突蛋白在细胞内合成 周核，以及许多像那些注定要合并到 轴膜被包裹在囊泡中，利用马达蛋白进行巨大的运动 沿MTS到轴突终末的距离。同样，前兆 突触小泡(SVS)的终极专门产品 神经元是从细胞体中传递出来的，在那里它们被制造出来， 通过基于MT的运输到达轴突的远端。最后，内吞体 和溶酶体前囊泡携带降解的轴突成分和 内源性神经营养因子在轴突MTS逆行中的作用 方向，朝向核周。 根据所取得的进展，本次续签申请包括3个具体目标 在本供资期间。1)重组动力系统 将被起诉以确定和描述MBO的监管因素 脑和肾上腺嗜铬细胞的转运，重点是 SVS和嗜铬颗粒的转运。关于管理层收购的假设 沿MTs的运输是以细胞器特有的方式进行调节的 接受测试。2)新发现的MTS和MTS络合物的结构 将测定蛋白磷酸酶2A(PP2A)。一种假设是 测试表明，MT结合的PP2A通过以下方式调节MBO沿MTS的运输 控制转运成分的磷酸化状态 机械或通过调节MT稳定性。3)MTS在以下方面的作用 维持小窝的结构将接受测试。新数据表明 这种小窝蛋白是小窝的一种驻留蛋白质，它以结构性循环。 在质膜和高尔基体之间通过一种需要 MTS用于运输到高尔基山脉，但不能远离高尔基山脉。一项测试将是 基于这样的假设：其他驻留的凹陷蛋白也 通常情况下，质膜和高尔基体之间通过MT- 从属循环。动力蛋白是运输马达的假说 也将测试洞穴对高尔基体的影响，以及 洞穴蛋白从高尔基体运回质膜将被 下定决心。

DESCRIPTION: (Applicant's Abstract) The neuron has no rival as a cell type that specializes in transport of membrane-bounded organelles (MBOs) along microtubles (MTs). This distinctive trait of the neuron is dictated by its unique morphological and functional properties. During neurogenesis, for example, the formation of dendrites and axons requires sustained delivery of nascent plasma membrane proteins and lipids into growing neurites. These membrane precursors are packages in vesicle whose surface-associated motor molecules move the vesicle along MTs to the distal tips of neurites, where fusion of the vesicles with the plasma membrane promotes neurite elongation. In differentiated neurons, the maintenance of axons is equally reliant upon MTs. Because the axon lacks protein synthesis machinery, but can be more than 10,000 times as long as the diameter of the perikaryon from which it emanates, the axon must constantly be supplied with new resident proteins to replace those that age and degrade. New axonal proteins are synthesized in the perikaryon, and many, like those destined for incorporation into the axolemma, are packaged in vesicles that use motor proteins to move great distances along MTs toward the axon terminal. Likewise, the precursors of synaptic vesicles (SVs), the ultimate specialized products of neurons, are delivered from the cell body, where they are manufactured, to the distal end of the axon by MT- based transport. Finally, endosomal and pre-lysosomal vesicles carry degraded axonal components and edocytosed neurotrophic factors along axonal MTs in the retrograde direction, toward the perikaryon. This renewal application comprises 3 Specific Aims based on progress made during the present funding period. 1) Reconstituted motility systems will be sued to identify and characterize regulatory factors for MBO transport in brian and adrenal chromaffin cells, with emphasis on transport of SVs and chromaffin granules. The hypothesis that MBO transport along MTs is regulated in an organelle-specific manner will be tested. 2) The structure of a newly discovered complex of MTs and protein phosphatase 2A (PP2A) will be determined. A hypothesis to be tested is that MT-bound PP2A regulates MBO transport along MTs by controlling the phosphorylation state of components of the transport machinery or by regulating MT stability. 3) The role of MTs in maintaining the structure of caveolae will be tested. New data indicate that caveolin, a resident protein of caveolae, cycles constitutively between the plasma membrane and the Golgi by a mechanism that requires MTs for transport toward, but not away from the Golgi. A test will be made of the hypothesis that other resident caveolar proteins also normally more between the plasma membrane and the golgi by a MT- dependent cycle. The hypothesis that dynein is the motor for transport of caveolin to the golgi will be also tested, and the mechanism for caveolin transport from the Golgi back to the plasma membrane will be determined.