Myosin-X and the molecular basis of filopodia function

描述（由申请人提供）：丝状伪足是细长的细胞延伸，似乎起细胞传感器的作用，允许细胞在诸如神经生长、血管形成和癌细胞转移的过程中与其周围环境相互作用。尽管丝状伪足和相关结构如微绒毛和静纤毛的重要性，但调节这些结构的形成和功能的分子机制仍不清楚。越来越多的证据表明，MyTH 4-FERM肌球蛋白，一个新认识的非常规肌球蛋白家族，作为在丝状伪足和相关结构中起作用的马达蛋白具有关键作用。人类表达四种MyTH 4-FERM肌球蛋白，其中两种突变导致遗传性耳聋。我们已经发现，肌球蛋白-X，脊椎动物特异性成员的MyTH 4-FERM肌球蛋白，定位于丝状伪足的尖端，是一个非常有效的诱导丝状伪足，并经历了一种新的形式的运动内丝状伪足。这使我们假设肌球蛋白X的功能作为一个电机的一个以前未知的系统内的丝状伪足和相关结构的细胞内运输。因此，我们建议：1）确定肌球蛋白X诱导丝状伪足的分子机制。2)研究我们发现的新的丝状伪足内运动系统的基本特性。3)分离全长肌球蛋白-X并确定其基本生化特性4）使用小鼠敲除来确定肌球蛋白-X的细胞和生物功能。通过研究myosin-X，在大多数脊椎动物细胞和组织中表达的MyTH 4-FERM肌球蛋白，这项研究将提供一个模型来研究MyTH 4-FERM肌球蛋白的基本细胞生物学及其在丝状伪足样结构中的作用。这项研究与耳聋特别相关，因为听力依赖于静纤毛，一种含有肌动蛋白丝核心的丝状伪足样机械传感器。此外，已知至少有五种其他非常规肌球蛋白的突变会导致人类耳聋，包括遗传性耳聋的主要原因Usher综合征1b。还有越来越多的证据表明，丝状伪足可以作为细胞的高速公路，运输材料，如关键信号分子和病毒，因此丝状伪足中肌球蛋白X功能的研究将有助于我们理解神经再生，血管生成和癌细胞扩散的基础细胞生物学。

DESCRIPTION (provided by applicant): Filopodia are slender cellular extensions that appear to function as cellular sensors that allow cells to interact with their surroundings in processes such as nerve growth, blood vessel formation, and the metastasis of cancer cells. Despite the central importance of filopodia and related structures such as microvilli and stereocilia, the molecular mechanisms that regulate the formation and function of these structures remain unclear. Growing evidence indicates that the MyTH4-FERM myosins, a newly recognized family of unconventional myosins, have critical roles as motor proteins that function in filopodia and related structures. Humans express four MyTH4-FERM myosins and mutations in two of these lead to hereditary deafness. We have discovered that myosin-X, a vertebrate-specific member of the MyTH4-FERM myosins that localizes to the tips of filopodia, is a remarkably potent inducer of filopodia, and undergoes a novel form of motility within filopodia. This has led us to hypothesize that myosin-X functions as a motor for a previously unsuspected system of intracellular transport within filopodia and related structures. We thus propose to: 1) Determine the molecular mechanisms by which myosin-X induces filopodia. 2) Investigate the basic properties of the novel system of intrafilopodial motility we have discovered. 3) Isolate full-length myosin-X and determine its fundamental biochemical properties 4) Determine the cellular and organismal functions of myosin-X using a mouse knock-out. By investigating myosin-X, the MyTH4-FERM myosin that is expressed in most vertebrate cells and tissues, this research will provide a model to investigate the fundamental cell biology of the MyTH4-FERM myosins and their roles in filopodia-like structures. This research is particularly relevant to deafness, since hearing depends on stereocilia, filopodia-like mechanosensors that contain a core of actin filaments. In addition, mutations in at least five other unconventional myosins are already known to cause human deafness, including Usher syndrome 1b, the leading cause of hereditary deaf-blindness. There is also growing evidence that filopodia can act as cellular highways that transport materials such as key signaling molecules and viruses, so studies of myosin-X function in filopodia will contribute to our understanding of the fundamental cell biology underlying nerve regeneration, angiogenesis, and the spread of cancer cells.