Cytoskeleton - Membrane Interactions

描述（由申请人提供）：肌动蛋白细胞骨架和富含胆固醇的液体有序膜结构域，也称为“脂筏”，都参与细胞粘附、运动、存活和膜运输过程中的信号转导。然而，潜在的分子机制尚不清楚。这项申请提出了一种新型膜骨架的持续研究，在当前的资助期内首次描述和表征，这可能代表了理解肌动蛋白和肌球蛋白参与脂质筏信号传导的“缺失环节”。由于脂质筏组织蛋白（flotillins, stomatin）和信号蛋白（Src家族激酶、异三聚体Gi蛋白、基质金属蛋白酶）与丝状肌动蛋白、肌球蛋白I和肌球蛋白II以及其他膜骨架蛋白（α -肌动蛋白、fodrin、超级绒毛蛋白）紧密结合，含有这种膜骨架（DRM-H）的耐洗涤膜表现出比其他富含胆固醇的膜组分更高的浮力密度。drm - h相关的膜骨架存在于许多运动细胞中，并明显调节细胞粘附、收缩和细胞外调节激酶（ERK1/2）的信号传导。

DESCRIPTION (provided by applicant): Both the actin cytoskeleton and cholesterol-rich liquid-ordered membrane domains, also called 'lipid rafts', are involved in signal transduction during cell adhesion, motility, survival, and membrane trafficking. However, the underlying molecular mechanisms are unclear. This application proposes the continued study of a new type of membrane skeleton, first described and characterized in the current funding period, that may represent a 'missing link' in understanding actin and myosin involvement in lipid raft signaling. Detergent-resistant membranes containing this membrane skeleton (DRM-H) exhibit a higher buoyant density than do other cholesterol-rich membrane fractions due to the tight association of lipid raft organizing proteins (flotillins, stomatin) and signaling proteins (Src family kinases, heterotrimeric Gi proteins, matrix metalloproteinase) with filamentous actin, myosins I and II, and other membrane skeleton proteins (alpha-actinin, fodrin, supervillin). DRM-H-related membrane skeletons are present in many motile cells and apparently regulate cell adhesion, contractility, and signaling to extracellularly regulated kinases (ERK1/2). We propose that the DRM-H membrane skeleton is involved in Src and/or ERK signaling by promoting local rearrangements of lipid raft-associated proteins. Supervillin, a membrane-proximal protein that also binds directly to actin and myosin II, appears to be a key control point for this regulation. To test these hypotheses, we propose to: (1) elucidate the roles of actin, myosin, supervillin, and other DRM-H proteins in the formation and reorganization of signaling scaffolds; (2) explore the mechanisms by which DRM-H proteins modulate focal adhesion function and cellular contractility; and (3) determine the role of the DRM-H membrane skeleton during membrane trafficking. These studies describe a novel mechanism for the attachment of actin and myosin II to cholesterol-rich membrane domains and will provide insight into cytoskeletal regulatory mechanisms in these domains. The long-range goal of this project is to understand how actin-based membrane skeletons function during cell motility, adhesion, and signaling. This information will increase our understanding of both normal cellular behaviors and pathological conditions associated with immune dysfunction, cancer cell invasion, muscular dystrophy, diabetes, and developmental abnormalities.