Myosin-X and the molecular basis of filopodia function

描述（由申请人提供）：丝状足是细长的细胞延伸，其功能似乎是细胞传感器，允许细胞在神经生长、血管形成和癌细胞转移等过程中与周围环境相互作用。尽管丝状足和相关结构如微绒毛和立体纤毛具有重要意义，但调控这些结构形成和功能的分子机制尚不清楚。越来越多的证据表明，MyTH4-FERM肌球蛋白是一个新发现的非常规肌球蛋白家族，在丝状足和相关结构中起着至关重要的运动蛋白作用。人类表达四种MyTH4-FERM肌球蛋白，其中两种的突变导致遗传性耳聋。我们发现myosin-X是脊椎动物特有的myosin- 4- ferm肌球蛋白的成员，它位于丝状足的尖端，是一种非常有效的丝状足诱导剂，并在丝状足内经历一种新的运动形式。这使我们假设肌球蛋白- x在丝状足和相关结构内的细胞内运输系统中起着马达的作用。因此，我们建议：1)确定肌球蛋白- x诱导丝状足的分子机制。2)研究我们发现的新的肌束内运动系统的基本特性。3)分离全长myosin-X并测定其基本生化特性4)用小鼠敲除法测定myosin-X的细胞和机体功能。通过研究在大多数脊椎动物细胞和组织中表达的MyTH4-FERM肌球蛋白myosin- x，本研究将为研究MyTH4-FERM肌球蛋白的基本细胞生物学及其在丝状足样结构中的作用提供一个模型。这项研究与耳聋特别相关，因为听力依赖于立体纤毛，一种含有肌动蛋白丝核心的丝状足状机械传感器。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，包括亚瑟综合征1b，这是遗传性耳盲的主要原因。也有越来越多的证据表明，丝状足可以作为细胞高速公路运输物质，如关键信号分子和病毒，因此研究肌球蛋白- x在丝状足中的功能将有助于我们理解神经再生、血管生成和癌细胞扩散的基本细胞生物学。

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.