KERATOCYTE COLLAGENASE INDUCED VIA FIBRONECTIN RECEPTOR

正常的眼睛功能取决于角膜的透明度，反过来， 取决于正常角膜基质的维持。 该基质 通常静止角膜细胞可被刺激合成并 分泌中性蛋白酶和细胞外基质。 基质伤口 愈合和重塑，降解现有的细胞外基质， 新细胞外基质的合成必须在空间上受到控制， 暂时的 过量的胶原酶分泌导致角膜溃疡或 融化细胞因子和细胞骨架干扰物，如细胞松弛素B和 佛波醇诱导胶原酶。 胶原酶活性受到调节 转录和细胞外抑制剂（TIMP）或激活剂。 我们目前的初步数据表明，角膜细胞胶原酶是通过诱导的， 纤连蛋白信号转导途径 我们假设角膜细胞 纤连蛋白受体（整合素）将完整的纤连蛋白与 纤连蛋白片段：纤连蛋白片段中的一个或多个识别序列。 纤连蛋白片段作为降解产物被检测到，激活 通过纤连蛋白受体的角膜细胞胶原酶途径。 我们的具体目标是： 1.更精确地定义细胞外基质信号， 胶原酶诱导 是否存在纤连蛋白或其他 调节金属蛋白酶的细胞外基质成分 分泌物？ 2.鉴定角膜基质细胞的整合素，并确定 它们的相对数量受纤连蛋白的内吞作用或 诱导胶原酶的刺激物。 3.通过形态学、动力学和定量分析确定， 前胶原酶诱导与 肌动蛋白细胞骨架的变化。 4.确定通过纤连蛋白受体的差异调节， 新的细胞外基质合成和蛋白酶合成/活性。 具体而言，胶原酶、胶原、纤连蛋白和TIMP是否诱导 促进新的合成或降解的模式？这是不是 在一个单独的细胞中展示？ 这些研究将有助于理解角膜伤口愈合，其中 角膜细胞降解并重新合成细胞外基质。 了解胶原酶调节机制将有助于预防 由于胶原酶分泌不受抑制而造成的损害，如圆锥角膜。 我们 长期目标是确定在细胞，亚细胞和 细胞外基质和个体在分子水平上 正常和病理状态下角膜细胞在时间和空间上相互作用 例如伤口愈合或圆锥角膜。

Normal eye function depends on corneal transparency which, in turn, depends on maintenance of a normal corneal stroma. The stromal keratocyte, normally quiescent, can be stimulated to synthesize and secrete neutral proteinases and extracellular matrix. In stromal wound healing and remodeling, degradation of existing extracellular matrix and synthesis of new extracellular matrix must be controlled spatially and temporally. Excess collagenase secretion causes corneal ulceration or melting. Cytokines and cytoskeletal disruptors like cytochalasin B and phorbol induce collagenase. Collagenase activity is regulated transcriptionally and by extracellular inhibitors (TIMP) or activators. We present preliminary data that keratocyte collagenase is induced via a fibronectin signal transduction pathway. We hypothesize that keratocyte fibronectin receptors (integrins) distinguish intact fibronectin from fibronectin fragments: one or more recognition sequences in the fibronectin fragment, sensed as degradation products, activate the keratocyte collagenase pathway via fibronectin receptors. Our specific aims are to: 1. Define more precisely the extracellular matrix signals for collagenase induction. Are there domain(s) of fibronectin or other extracellular matrix components which regulate metalloproteinase secretion? 2. Identify the integrins of corneal keratocytes and determine whether their relative number is regulated by endocytosis of fibronectin or by stimuli which induce collagenase. 3. Determine morphologically, and by kinetic and quantitative assays, whether a strict correlation exists between procollagenase induction and changes in the actin cytoskeleton. 4. Determine differential regulation through the fibronectin receptor of new extracellular matrix synthesis and proteinase synthesis/activity. Specifically, are collagenase, collagen, fibronectin, and TIMP induced in patterns which promote new synthesis or degradation? Can this be demonstrated in an individual cell? These studies will aid understanding of corneal wound healing, in which keratocytes degrade and re-synthesize extracellular matrix. Understanding mechanisms of collagenase regulation will help prevent damage from uninhibited collagenase secretion, as in keratoconus. Our long term goal is to determine at the cellular, subcellular and molecular level how the extracellular matrix and the individual keratocyte interact temporally and spatially in normal and pathological situations such as wound healing or keratoconus.