Defining Effects of Myosin VII Structure and Kinetics on Hereditary Deafness

描述(申请人提供)：肌球蛋白VII属于肌球蛋白家族的肌球蛋白激活的ATPase马达蛋白，负责在真核生物的肌动蛋白细胞骨架上产生力量。在哺乳动物中，肌球蛋白VII通常在极化的细胞结构中表达，这些细胞结构形成富含肌动蛋白的突起的有序阵列。根据突变生物的表型和生化研究表明，肌球蛋白VII处于与肌动蛋白强烈结合的状态，这种肌球蛋白被认为主要是通过维持这些结构中细胞骨架和膜组件之间的张力来发挥锚的作用。肌球蛋白Vila的突变导致人类最常见的遗传性耳聋之一，但疾病表现的分子基础目前尚不清楚。尽管它在生物医学上很重要，但目前还缺乏决定这种马达如何执行其细胞功能的结构和动力学细节。这项建议的长期目标是了解肌球蛋白VII中的酶和结构适应，以及这些变化如何有助于精确的生物学功能。具体地说，这项提议的第一个目标是确定在人类中产生耳聋表型的突变如何破坏肌球蛋白Vila的酶和运动特性。第二个目的是确定天然肌球蛋白VII的寡聚体状态，这是建立一个完整的肌球蛋白VII功能和细胞运动模型所必需的。作为一个整体，本提案中描述的工作旨在实现肌球蛋白VII功能的更完整的模型，并将为肌球蛋白VII功能障碍导致耳聋的分子基础提供洞察。与公共卫生相关：肌球蛋白V1a的突变与Ib型亚瑟综合征(和各种其他形式的遗传性耳聋)的发展直接相关，这是人类遗传性耳聋的最大原因之一--失明综合征。目前这些疾病患者缺乏治疗选择的一个根本原因是对肌球蛋白VII在耳朵和眼睛中功能的分子基础了解有限。这项拟议的研究侧重于了解肌球蛋白VII作为分子马达的功能，以更好地了解肌球蛋白VII马达活性丧失是如何导致耳聋的。

DESCRIPTION (provided by applicant): Myosin VII belongs to the myosin family of actin-activated ATPase motor proteins responsible for generating force on the actin cytoskeleton in eukaryotes. In mammals, myosin VII is generally expressed in polarized cellular structures that form ordered arrays of actin-rich protrusions. Based on phenotypes of mutant organisms and biochemical studies demonstrating that myosin VII dwells in a state strongly-bound to actin, this myosin is thought to act primarily as an anchor by maintenance of tension between the cytoskeleton and membrane components in these structures. Mutations in myosin Vila results in one of the most common forms of inherited deafness in humans, but the molecular basis of disease presentation is currently unknown. Despite its biomedical importance, the structural and kinetic details that dictate how this motor performs its cellular functions are currently lacking. The long term goal of this proposal is to gain an understanding of the enzymatic and structural adaptations in myosin VII and how these contribute to precise biological function. Specifically, the first aim of this proposal is to identify how mutations that generate deafness phenotypes in humans disrupt the enzymatic and motor properties of myosin Vila. The second aim is to determine the oligomeric state of native myosin VII, which is necessary to develop a complete model of myosin VII function and motility in cells. As a whole, the work described in this proposal is directed towards the attainment of a more complete model for myosin VII function and will provide insight to the molecular basis of deafness that results from myosin VII dysfunction. Relevance to public health: Mutations in myosin Vila are directly associated with the development of Usher syndrome type Ib (and various other forms of inherited deafness), comprising one of the largest causes of inherited deafness-blindness syndromes in humans. A fundamental reason for the current lack of treatment options for patients with these diseases is a limited understanding of the molecular basis for myosin VII function in the ear and eye. The proposed research focuses on understanding how myosin VII functions as a molecular motor to better understand how loss of myosin VII motor activity leads to deafness.