Dynactin/microtubule interactions in dynein motility

描述（由申请人提供）： 细胞质动力蛋白和动力肌动蛋白运动复合体产生力，为大量细胞功能提供运动。长距离运动在神经元的轴突过程中特别重要，其中动力蛋白和动力蛋白在微米到米的距离范围内逆行运输货物。动力蛋白和动力肌动蛋白运动机制的组成部分的遗传病变改变轴突运输，并可导致严重的神经元疾病。动力蛋白采取多个步骤而不与微管分离的能力，称为持续合成能力，被动力蛋白增强。为了增强这种持续合成能力，动力蛋白必须能够结合微管。该建议的目的是阐明动力蛋白/微管相互作用增加细胞质动力蛋白合成能力的机制。我们的假设是，持续合成能力增强的发生，因为动力蛋白，货物，和微管细胞骨架之间的分子系绳dynactin的行为。作为一种分子系链，动力蛋白阻止马达/货物复合物从微管上完全解离，并使动力蛋白与微管的重新结合偏向。 该提案的第一个具体目标是表征动力蛋白和微管之间发生的相互作用，目的是测试动力蛋白拴系模型的有效性，并区分可能的作用机制。这将通过A）确定动力蛋白的哪些部分在微管结合中起作用并表征相互作用的表观结合强度，B）分析动力蛋白/微管相互作用的单分子行为，和C）表征动力蛋白/微管相互作用在进行性运动中的作用来完成。第二个具体目标是阐明dynactin/微管相互作用的调节机制。这将通过A）检查dynactin分子异质性和B）检查lis 1功能来完成。 细胞质动力蛋白和动力肌动蛋白运动复合体的异常功能可能引起或加剧的广泛的人类健康问题提出了动力蛋白和动力肌动蛋白组分可能是治疗干预的有用靶点的可能性。然而，我们需要更好地了解如何动力蛋白为基础的运动发生的作用，动力蛋白和动力蛋白可能发挥这些疾病之前，可以尝试干预。

DESCRIPTION (provided by applicant): The cytoplasmic dynein and dynactin motor complex generates force to provide movement for a vast array of cellular functions. Long-range movements are especially important in the axonal processes of neurons where dynein and dynactin move retrograde cargo over distances ranging from microns to meters. Genetic lesions in components of the dynein and dynactin motor machinery alter axonal transport and can result in severe neuronal disorders. The ability of dynein to take multiple steps without dissociating from the microtubule, called processivity, is enhanced by dynactin. For this processivity enhancement to take place, dynactin must be able to bind microtubules. The goal of this proposal is to elucidate the mechanism by which the dynactin/microtubule interaction increases cytoplasmic dynein processivity. Our hypothesis is that processivity enhancement occurs because dynactin acts as a molecular tether between dynein, cargo, and the microtubule cytoskeleton. As a molecular tether, dynactin prevents the complete dissociation of the motor/cargo complex from the microtubule and biases the rebinding of dynein to the microtubule. The first specific aim of this proposal is to characterize the interactions that occur between dynactin and microtubules with the goal of testing the validity of the dynactin tethering model and discriminating between possible mechanisms of action. This will be done by A) determining what portions of dynactin play a role in microtubule binding and characterizing the apparent binding strengths of the interactions, B) analyzing the single-molecule behavior of the dynactin/microtubule interaction, and C) characterizing the role of the dynactin/microtubule interaction in processive motility. The second specific aim is to elucidate regulatory mechanisms of the dynactin/microtubule interaction. This will be done by A) examining dynactin molecular heterogeneity and B) examining lis1 function. The wide range of human health problems that may be caused or compounded through the aberrant function of the cytoplasmic dynein and dynactin motor complex raises the possibility that dynein and dynactin components may be useful targets for therapeutic intervention. However, we require a better understanding of how dynein-based motility occurs and the role that dynein and dynactin may play in these disorders before intervention can be attempted.