Integrin-collagen signaling and control of fibroblast proliferation

描述(申请人提供)：特发性肺纤维化(IPF)是一种进行性的、致命的纤维性肺部疾病，目前还没有有效的治疗方法。前哨形态病变为成纤维细胞灶，由富含I型胶原基质的肌成纤维细胞组成。初步证据支持肌成纤维细胞在IPF的持续发展中的关键作用，因为这是一种在肺泡壁中增殖和沉积胶原的细胞。尽管研究强烈支持IPF成纤维细胞表现出独特的病理表型，但对于导致进行性纤维化的IPF成纤维细胞的病理性质与正常肺修复所必需的肌成纤维细胞的生理功能之间的差异，仍存在很大的认识空白。这项建议的目的是描述IPF成纤维细胞病理本质的分子过程。开创性研究表明，聚合的I型胶原对成纤维细胞的增殖起负调控作用。与此一致，我们发现聚合的胶原抑制了正常肺成纤维细胞的增殖。相反，我们发现IPF成纤维细胞逃脱了这种限制。我们对这一现象的机制研究指出，与I型胶原结扎时，整合素信号异常。我们发现整合素-ECM相互作用调节PTEN的表达和活性。PTEN是一种基础活性较高的磷酸酶。它通过抑制整合素-磷脂酰肌醇3-激酶(PI3K)/Akt信号通路，负向调节细胞增殖，发挥肿瘤抑制作用。当将正常肺成纤维细胞培养在聚合的胶原上时，我们发现PTEN活性仍然很高。相反，当IPF成纤维细胞被培养在聚合的胶原上时，PTEN的活性不适当地低，使得PI3K/Akt信号通路不受抑制，并消除了调节增殖的主要生理负反馈信号之一。这使得IPF成纤维细胞能够避开聚合胶原蛋白的负面调节作用。我们假设：1整合素-I型胶原相互作用导致PTEN的异常调节。这导致PI3K/Akt/S6K1活性不受抑制，是IPF成纤维细胞在聚合胶原上病理性增殖的基础。为了验证我们的假设，我们将：目的1.确定PI3K/Akt/S6K1-PTEN信号轴在使IPF成纤维细胞逃避聚合的I型胶原的负面增殖效应中的作用。目的2.明确1整合素-I型胶原相互作用对对照和特发性肺纤维化肺成纤维细胞PTEN和PI3K/Akt信号通路调控的分子基础。目的3.用体内方法学验证1整合素PI3K/Akt/S6K1-PTEN信号轴在特发性肺纤维化中功能异常的体外研究。公共卫生相关性：特发性肺纤维化(IPF)是一种慢性、致命性间质性肺部疾病。前哨形态病变为成纤维细胞灶，由嵌于I型胶原基质中的成纤维细胞组成。开创性研究表明，聚合的I型胶原对成纤维细胞的增殖起负调控作用。我们发现，IPF成纤维细胞已经逃脱了这种限制。我们对这一现象的机制研究指出，异常的增殖信号通过整合素1，涉及下游的磷酸肌醇3-激酶/Akt-PTEN轴。这项资助申请的目的是描述整合素胶原相互作用导致IPF成纤维细胞异常增殖信号的分子机制。我们的目标是发现肌成纤维细胞细胞结构中那些导致IPF持续纤维化的成分，并在正常情况下实现适当的组织愈合。识别控制IPF成纤维细胞病理行为的关键调控节点可能为限制以IPF为特征的进行性纤维化提供分子治疗靶点。

DESCRIPTION (provided by applicant): Idiopathic Pulmonary Fibrosis (IPF) is a progressive, fatal fibrotic lung disease for which there is no effective therapy. The sentinel morphological lesion is the fibroblastic focus, which is composed of myofibroblasts in a type I collagen rich matrix. Prima facie evidence supports the critical role for myofibroblasts in the relentless progression of IPF given that this is the cell that proliferates and deposits collagen in the alveolar wall. Although studies strongly support the notion that IPF fibroblasts display a distinct pathological phenotype, large gaps in knowledge remain regarding differences between the pathological nature of IPF fibroblasts responsible for progressive fibrosis and the physiologic function of myofibroblasts essential for normal lung repair. The objective of this proposal is to characterize the molecular processes underlying the pathological nature of IPF fibroblasts. Seminal studies have demonstrated that polymerized type I collagen acts as a negative regulator of fibroblast proliferation. Consistent with this, we have found that normal lung fibroblast proliferation is inhibited by polymerized collagen. In contrast, we have found that IPF fibroblasts have escaped this restraint. Our mechanistic studies of this phenomenon point to abnormalities in ¿1 integrin signaling in response to ligation with type I collagen. We have discovered that integrin-ECM interaction regulates PTEN expression and activity. PTEN is a phosphatase whose baseline activity is constitutively high. It functions as a tumor suppressor by negatively regulating proliferation by repressing the integrin-phosphoinositol 3-kinase (PI3K)/Akt signaling pathway. When normal lung fibroblasts are cultured on polymerized collagen, we have found that PTEN activity remains high. In contrast, when IPF fibroblasts are cultured on polymerized collagen PTEN activity is inappropriately low leaving the PI3K/Akt signaling pathway unrestrained and removing one of the major physiological negative feedback signals regulating proliferation. This enables IPF fibroblasts to circumvent the negative regulatory effects of polymerized collagen. We hypothesize that: ¿1 integrin-type I collagen interaction results in aberrant regulation of PTEN. This leads to unrestrained PI3K/Akt/S6K1 activity and underlies the pathologic proliferation of IPF fibroblasts on polymerized collagen. To test our hypothesis we will: Aim 1. Determine the role of the PI3K/Akt/S6K1-PTEN signaling axis in enabling IPF fibroblasts to elude the negative proliferative effects of polymerized type I collagen. Aim 2. Define the molecular basis for regulation of PTEN and the PI3K/Akt signal pathway in control and IPF lung fibroblasts by ¿1 integrin-type I collagen interaction. Aim 3. Validation of in vitro studies implicating abnormal function of the ¿1 integrin PI3K/Akt/S6K1-PTEN signaling axis in IPF fibrogenesis by in vivo methodology. PUBLIC HEALTH RELEVANCE: Idiopathic pulmonary fibrosis (IPF) is a chronic, lethal interstitial lung disease. The sentinel morphological lesion is the fibroblastic focus, which is composed of fibroblasts embedded in a type I collagen rich matrix. Seminal studies have demonstrated that polymerized type I collagen acts as a negative regulator of fibroblast proliferation. We have discovered that IPF fibroblasts have escaped this restraint. Our mechanistic studies of this phenomenon point to aberrant proliferation signaling through the ¿1 integrin, involving the downstream phosphoinositol 3-kinase/Akt - PTEN axis. The objective of this grant application is to characterize the molecular mechanism by which ¿1 integrin-collagen interaction results in abnormal proliferative signaling in IPF fibroblasts. It is our goal to uncover those components of the myofibroblast cellular machinery that result in unrelenting fibrosis in IPF, and in proper tissue healing under normal circumstances. Identifying key regulatory nodes controlling the pathologic behavior of IPF fibroblasts may provide molecular therapeutic targets to limit the progressive fibrosis that characterizes IPF.