Integrin-collagen signaling and control of fibroblast proliferation

描述（由申请人提供）：特发性肺纤维化（IPF）是一种进行性、致死性纤维化肺部疾病，目前尚无有效治疗方法。前哨形态病变为成纤维细胞病灶，由富含I型胶原的肌成纤维细胞组成。鉴于肌成纤维细胞是增生并在肺泡壁沉积胶原蛋白的细胞，初步证据支持肌成纤维细胞在IPF无情进展中的关键作用。尽管研究强烈支持IPF成纤维细胞表现出独特的病理表型的观点，但关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，知识上仍然存在很大差距。本研究的目的是表征IPF成纤维细胞病理性质的分子过程。开创性的研究表明，聚合的I型胶原作为成纤维细胞增殖的负调节因子。与此一致，我们发现正常肺成纤维细胞增殖被聚合胶原抑制。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，在与I型胶原结扎的反应中，1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是一种基线活性高的磷酸酶。它通过抑制整合素-磷酸肌醇3-激酶(PI3K)/Akt信号通路负性调节增殖而发挥肿瘤抑制作用。当正常肺成纤维细胞在聚合胶原上培养时，我们发现PTEN活性仍然很高。相比之下，当IPF成纤维细胞在聚合胶原上培养时，PTEN活性低得不适当，使PI3K/Akt信号通路不受约束，从而消除了调节增殖的主要生理负反馈信号之一。这使得IPF成纤维细胞能够规避聚合胶原的负面调节作用。我们假设：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活性不受限制，并成为IPF成纤维细胞在聚合胶原上的病理性增殖的基础。为了验证我们的假设，我们将：目标1。确定PI3K/Akt/S6K1-PTEN信号轴在IPF成纤维细胞逃避聚合型胶原的负增殖作用中的作用。目标2。确定PTEN和PI3K/Akt信号通路在对照和IPF肺成纤维细胞中通过¿1整合素I型胶原相互作用调控的分子基础。目标3。体内方法验证IPF纤维化过程中1整合素PI3K/Akt/S6K1-PTEN信号轴异常功能的体外研究。公共卫生相关性：特发性肺纤维化（IPF）是一种慢性、致死性间质性肺疾病。前哨形态病变为成纤维细胞病灶，由包埋在富含I型胶原的基质中的成纤维细胞组成。开创性的研究表明，聚合的I型胶原作为成纤维细胞增殖的负调节因子。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表明，异常增殖信号通过整合素传递，涉及下游磷酸肌醇3-激酶/Akt - PTEN轴。本资助申请的目的是表征整合素-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。我们的目标是揭示在正常情况下导致IPF持续纤维化和适当组织愈合的肌成纤维细胞机制的组成部分。确定控制IPF成纤维细胞病理行为的关键调控节点可能为限制IPF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.