Myosin-X and the molecular basis of filopodia function

描述(申请人提供)：丝状伪足是一种细长的细胞延伸，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。尽管丝状伪足及其相关结构如微绒毛和立体纤毛非常重要，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，MyTH4-ferm肌球蛋白是一个新发现的非传统肌球蛋白家族，作为运动蛋白在丝状伪足和相关结构中发挥重要作用。人类表达四个MyTH4-FERM肌球蛋白，其中两个的突变会导致遗传性耳聋。我们已经发现，MyTH4-ferm肌球蛋白中的一种脊椎动物特有的成员MyTH4-ferm肌球蛋白-X是丝状伪足顶端的一种非常有效的诱导剂，并且在丝状伪足中经历了一种新的运动形式。这导致我们假设，肌球蛋白-X在丝状伪足和相关结构中作为一种以前未被怀疑的细胞内运输系统的马达发挥作用。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管腔内运动系统的基本性质。3)分离全长肌球蛋白-X并测定其基本生化性质4)利用小鼠基因敲除技术确定肌球蛋白-X的细胞和组织功能。通过研究大多数脊椎动物细胞和组织中表达的MyTH4-ferm肌球蛋白-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，因为听力依赖于含有肌动蛋白细丝核心的丝状机械传感器--立体纤毛。此外，已知至少其他五种非传统肌球蛋白的突变会导致人类耳聋，包括亚瑟综合征1b，这是遗传性耳聋的主要原因。越来越多的证据表明，丝状伪足可以作为细胞高速公路，运输关键信号分子和病毒等物质，因此对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.