Nucleoskeleton-Cytoskeleton Connections and Cell Polarity in Aging

项目摘要 细胞骨架及其与细胞核的连接在建立细胞形态中起着重要作用， 极性、迁移和粘附。由于它们在这些细胞功能中的重要作用， 重要的是要了解发生在细胞骨架系统及其核连接的变化 在正常的细胞衰老过程中。尽管如此重要，但人们对它的作用知之甚少。 生理老化中的细胞骨架。我们的初步研究发现了 细胞极性缺陷，发生在成纤维细胞从儿童加速老化障碍哈钦森- 吉尔福德早老综合征以及来自生理年龄个体的成纤维细胞。这一缺陷是由 内核膜内侧核板层之间的不平衡连接， 两种主要的细胞骨架蛋白系统：肌动蛋白微丝和微管。这些连接是 核骨架与细胞骨架连接体（LINC）复合物介导的 膜SUN和外核膜KASH/nesprin蛋白。在老龄化方面， 与肌动蛋白微丝相比，nesprin-2G与微管（由SUN 1支持）的相互作用增加 （支持SUN 2）这导致了我们的总体假设，即改变了核细胞骨架连接 由LINC复合物介导的细胞内信号传导导致生理老化中的固有细胞极性缺陷以及 加速老化症我们进一步假设这种缺陷至少部分是由一种蛋白质介导的 由老年人的细胞分泌的因子。我们建议在三个具体目标中测试这些假设。在 目的1、阐明生理性衰老过程中细胞极性缺陷的机制。我们将 确定在衰老过程中如何在核膜中建立增加的SUN 1水平，探索如何 SUN 1与nesprin-2G的相互作用使其相互作用偏向微管，并检查细胞质如何 微管受到它们与核膜过度相互作用的影响。在目标2中，我们将研究 年龄依赖性细胞极性缺陷在体内伤口愈合中的作用。我们会检查皮肤伤口 从年轻和年老的小鼠，以确定是否相同的机制，产生极性缺陷，在组织培养 在转基因小鼠中检查伤口愈合和成纤维细胞极性 成纤维细胞中SUN 1的过表达。在目标3中，我们将纯化和表征从大肠杆菌分泌的可溶性因子。 老化的电池，导致有缺陷的电池极性。我们将使用质谱分析的补充方法， 蛋白纯化以鉴定我们称之为FRAC的因子，即从老化细胞释放的因子。完成 这些目标将使我们对LINC复合体中的核细胞连接的改变有新的认识 导致老化中基本细胞极性缺陷。

Project Summary The cytoskeleton and its connections to the nucleus play fundamental roles in establishing cellular morphology, polarity, migration and adhesion. Because of their essential roles in these cellular functions, it is critically important to understand the changes that take place in cytoskeletal systems and their nuclear connections during the normal process of cellular aging. Despite this importance, remarkably little is known about the role of the cytoskeleton in physiologically aging. Our preliminary studies have led to the discovery of a fundamental cell polarity defect that occurs in fibroblasts from children with the accelerated aging disorder Hutchinson- Gilford progeria syndrome and also in fibroblasts from physiologically-aged individuals. This defect results from unbalanced connections between the nuclear lamina on the inner aspect of the inner nuclear membrane and two major cytoskeletal protein systems: actin microfilaments and microtubules. These connections are mediated by the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex composed of inner nuclear membrane SUN and outer nuclear membrane KASH/nesprin proteins. In aging, there is a preferential increased interaction of nesprin-2G with microtubules (supported by SUN1) versus actin microfilaments (supported by SUN2). This has led to our overall hypothesis that altered nucleocytoskeletal connections mediated by the LINC complex causes an intrinsic cell polarity defect in physiological aging as well as an accelerated aging disorder. We further hypothesize that this defect is at least in part mediated by a protein factor secreted by cells from aged individuals. We propose to test these hypotheses in three specific aims. In Aim 1, we will decipher the mechanism underlying the cell polarity defect in physiological aging. We will determine how increased SUN1 levels are established in the nuclear envelope during aging, explore how SUN1 interaction with nesprin-2G biases its interaction toward microtubules and examine how cytoplasmic microtubules are impacted by their excessive interaction with the nuclear envelope. In Aim 2, we will examine the role of the age-dependent cell polarity defect in would healing in vivo. We will examine cutaneous wounds from young and old mice to determine if the same mechanisms that generate polarity defects in tissue culture are operative in vivo as well as examine wound healing and fibroblast polarity in transgenic mice overexpressing SUN1 in fibroblasts. In Aim 3, we will purify and characterize a soluble factor secreted from aged cells that leads to defective cell polarity. We will use complementary methods of mass spectrometry and protein purification to identify this factor we call FRAC, for Factor Released from Aged Cells. Completion of these aims will lead to novel insights into how alterations in nucleocytoskeltal connections at the LINC complex lead to a fundamental cell polarity defect in aging.