Cellular regulation of myosin-I

描述(由申请人提供)：本提案中的努力集中于确定脊椎动物肌球蛋白-I的调节机制。肌球蛋白-I亚型是肌球蛋白超家族中的单头、膜相关成员，存在于大多数真核细胞中。肌球蛋白-是在人类中发现的最大的非传统肌球蛋白家族(八个基因)。脊椎动物肌球蛋白-I家族的大小和表达谱使其成为最多样化的类别之一。肌球蛋白-IS在膜动力学、细胞骨架结构、机械信号转导、内小体加工以及可能的核转录中发挥着重要作用。我们现在才开始了解这类重要马达的分子作用和调控模式。因此，我们在这项建议中的努力集中在了解脊椎动物肌球蛋白-I亚型的物理性质以及这些性质的调节。我们将使用细胞生物学、生物物理和生化技术的组合来研究以下具体目标： 1.肌球蛋白-I与脂膜的生化和细胞相互作用。我们将研究肌球蛋白-I亚型信号转导脂质的特异性，我们将确定肌球蛋白-I亚型与膜的运动相互作用，以及肌球蛋白-I亚型与膜结合和释放的动力学。 2.基于微丝的肌球蛋白-I的调节。非肌原肌球蛋白在肌球蛋白I的定位和活性调节中起着重要作用，但对这一基本调节方式知之甚少。我们将研究原肌球蛋白和肌球蛋白-I相互作用的生化细节，目的是了解微丝对肌球蛋白-I的细胞调控。 3.肌球蛋白-I作为张力传感器的特性。肌球蛋白-I是一种低占空比的马达。然而，我们的新研究表明，在小负载下，肌动蛋白附着的寿命显著增加，从而成为一种高占空比的电机。我们将研究力和运动密度在调节前进运动中的作用，我们将研究肌球蛋白-I家族中的机械多样性。

DESCRIPTION (provided by applicant): Efforts in this proposal focus on determining the mechanisms of regulation of vertebrate myosin-I. Myosin-I isoforms are the single-headed, membrane-associated members of the myosin superfamily that are found in most eukaryotic cells. Myosin-Is comprise the largest unconventional myosin family found in humans (eight genes). The large size and expression profile of the vertebrate myosin-I family distinguishes it as one of the most diverse classes. Myosin-Is play essential roles in membrane dynamics, cytoskeletal structure, mechanical signal-transduction, endosome processing, and possibly nuclear transcription. We are only now learning the molecular roles and modes of regulation of this important class of motors. Therefore, our efforts in this proposal focus on understanding the physical properties of vertebrate myosin-I isoforms and the regulation of these properties. We will use a combination of cell biological, biophysical, and biochemical techniques to investigate the following specific aims: 1. Biochemical and cellular interactions of myosin-I with lipid membranes. We will investigate the specificity of myosin-I isoforms for signaling lipids, we will determine the kinetics of phosphoinositide binding and release, and we will determine the motile interactions of myosin-I isoforms with membranes. 2. Microfilament-based regulation of myosin-I. Non-muscle tropomyosin plays an important role in regulating myosin-I localization and activity, but very little is known about this fundamental mode of regulation. We will investigate the biochemical details of the tropomyosin and myosin-I interaction with the goal of understanding the cellular regulation of myosin-I by microfilaments. 3. Characterization of myosin-I as a tension-sensor. Myosin-I is a low-duty ratio motor in the absence of load. However, our new investigations show that under small loads, the lifetime of actin attachment is increased dramatically, such that it becomes a high duty ratio motor. We will investigate the role of force and motor density in regulating processive motility, and we will investigate the mechanical diversity within the myosin-I family.