ECM and Cell Cycle Control in Aortic Smooth Muscle Cells

在动脉粥样硬化形成过程中，血管平滑肌细胞被认为经历了从收缩表型到合成表型的转变，获得了增殖的能力。我们在过去几年的研究表明，细胞外基质和整合素在激活细胞周期蛋白依赖性蛋白依赖性蛋白激酶(CDKs)的G1期中起着至关重要的作用。新的数据显示，CD44是一种与透明质酸(HA)结合的黏附受体，调节主动脉平滑肌细胞和成纤维细胞中整合素依赖的信号事件，控制肌动蛋白细胞骨架和G1期细胞周期进程。这些结果验证了长期以来关于整合素和CD44之间潜在相互作用的假设。对CD44缺失小鼠的遗传分析表明，CD44与整合素的相互作用可能至少部分解释了CD44促进动脉粥样硬化的作用。现在提出了三个目标来研究整合素和CD44在肌动蛋白组织、G1期细胞周期进展和主动脉平滑肌细胞增殖中的相互作用。目的1将扩展初步结果，表明CD44抑制整合素依赖的细胞扩散和肌动蛋白应激纤维的形成。我们将描述CD44和整合素之间潜在的物理相互作用，并研究CD44影响整合素功能的机制。目的2扩展初步数据显示，HA和CD44调节G1期细胞周期进程。我们将绘制这种调节的分子基础图，并确定HA-CD44如何影响调节G1期进展的信号通路。目的3通过CD44缺失和CD44/ApoE双缺失小鼠与Cyclin A启动子-EGFP转基因小鼠交配，研究CD44对体内细胞增殖的影响。分析子代分离的主动脉中的EGFP荧光将使我们能够确定CD44对正常血管细胞增殖的影响，以及在动脉粥样硬化和导管诱导的损伤过程中被认为对刺激的平滑肌细胞增殖的影响。

During atherogenesis, vascular smooth muscle cells are thought to undergo conversion from a contractile to a "synthetic" phenotype, acquiring the ability to proliferate. Our studies over the past several years have shown that the ECM and integrins have essential roles in activating the G1 phase cyclin-dependent kinases (cdks), the critical regulators of cell proliferation. New data described here shows that CD44, an adhesion receptor that binds to hyaluronic acid (HA), regulates integrin-dependent signaling events in aortic smooth muscle cells and fibroblasts, controlling both the actin cytoskeleton and G1 phase cell cycle progression. These results validate a long-standing assumption about the potential interaction between integrins and CD44. Genetic analysis in CD44-null mice suggest that the CD44-integrin interaction may explain, at least in part, the pro-atherosclerotic effect of CD44. Three aims are now proposed to study the interactions between integrins and CD44 on actin organization, G1 phase cell cycle progression, and aortic smooth muscle cell proliferation. Aim 1 will extend preliminary results showing that CD44 inhibits integrin-dependent cell spreading and formation of actin stress fibres. We will characterize potential physical interactions between CD44 and integrins and study the mechanism by which CD44 affects integrin function. Aim 2 extends preliminary data showing that HA and CD44 regulate G1 phase cell cycle progression. We will map the molecular basis of the regulation and determine how HA-CD44 affects the signaling pathways regulating G1 phase progression. Aim 3 examines the effect of CD44 on cell proliferation in vivo by mating CD44-null and CD44/ApoE-double null mice to a cyclin A promoter-eGFP transgenic mouse. Analysis of eGFP fluorescence in isolated aortae from the progeny will allow us to determine the effect of CD44 on normal smooth muscle cell proliferation, as well as on the stimulated smooth muscle cell proliferation thought to occur during atherosclerosis and catheter-induced injury.