Activation of latent TGF-beta by integrins

整合素激活潜在的 TGF-β

• 批准号: 7116401
• 负责人: John S Munger
• 金额: $ 41.26万
• 依托单位: NEW YORK UNIVERSITY SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-02-07 至 2008-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7116401
• 关键词: angiogenesis; animal infant mortality; antibody formation; autoantibody; gene deletion mutation; gene expression; genetically modified animals; immunocytochemistry; in situ hybridization; integrins; laboratory mouse; phenotype; protein binding; protein protein interaction; protein sequence; transforming growth factors

DESCRIPTION (provided by applicant): TGFbeta, which exists in 3 isoforms, is a pleiotropic cytokine involved in a variety of lung processes and diseases, e.g., development, pulmonary fibrosis, tuberculosis, asthmatic airway remodeling and cancer. TGFbeta bioavailability is tightly regulated in the extracellular space: TGFbeta is secreted in a latent form, which is sequestered in matrix binding sites by the action of an adapter protein (LTBP), and must be activated before it can signal via TGFbeta receptors. TGFbeta latency occurs as a result of binding to the TGFbeta propeptide Latency-Associated Peptide (LAP), and activation involves releasing TGFbeta from LAP. Because all TGFbeta signaling occurs subsequent to TGFbeta activation, the activation mechanisms are critical control points. Mechanisms of TGFbeta activation have been proposed (e.g., thrombospondin-1, proteases and oxidants), but their roles in vivo are unclear. We showed that an epithelium-specific integrin, alphaVbeta6, binds latent TGFbeta1 at an RGD sequence within LAP. Cells expressing alphaVbeta6 activate TGFbeta1, and mice lacking alphaVbeta6 do not develop bleomycin-induced pulmonary fibrosis. We have also shown that alphaVbeta6 can activate TGFbeta3, and that another integrin expressed in lung epithelium (alphaVbeta8) can activate TGFbeta1/3. The goal of this work is to define the role of integrin-mediated TGFbeta1 activation in vivo. To that end, we have generated knockin mice with a mutation in the TGFbeta1 gene that encodes a nonfunctional integrin-binding site in the LAP propeptide. The phenotype of these mice (designated TGFbeta1-RGE) reproduces the most prominent aspect of the TGFbeta1-/- phenotype: severe, multiorgan inflammation that causes death at 3-4 weeks of age. This important finding suggests the possibility that integrin-mediated TGFbeta1 activation occurs upstream of most TGFbeta1 effects. The specific aims of this work are to (1) characterize the TGFbeta1-RGE mice in comparison to TGFbeta1-/- mice, (2) test the hypothesis that the only TGFbeta1-activating integrins in vivo are alphaVbeta6 and alphaVbeta8, and (3) test the hypothesis that the phenotype of certain integrin KO mice (alphaV-/- and (beta8-/-) is due to combined lack of TGFbeta1 and TGFbeta3 activation. These studies will further delineate the role of RGD-binding integrins in TGFbeta biology and provide a basis for important studies of their role in lung pathology.

描述（由申请人提供）：TGFbeta存在3种亚型，是一种多效性细胞因子，参与多种肺部过程和疾病，例如发育、肺纤维化、结核病、哮喘气道重塑和癌症。 TGFbeta 的生物利用度在细胞外空间受到严格调节：TGFbeta 以潜在形式分泌，通过衔接蛋白 (LTBP) 的作用被隔离在基质结合位点，并且必须先被激活，然后才能通过 TGFbeta 受体发出信号。 TGFbeta 潜伏期是由于与 TGFbeta 前肽潜伏相关肽 (LAP) 结合而发生，激活涉及从 LAP 释放 TGFbeta。 由于所有 TGFbeta 信号传导均在 TGFbeta 激活后发生，因此激活机制是关键的控制点。 TGFbeta 激活机制已被提出（例如血小板反应蛋白-1、蛋白酶和氧化剂），但它们在体内的作用尚不清楚。我们发现上皮特异性整合素 alphaVbeta6 在 LAP 内的 RGD 序列处结合潜在的 TGFbeta1。表达 alphaVbeta6 的细胞会激活 TGFbeta1，而缺乏 alphaVbeta6 的小鼠不会发生博来霉素诱导的肺纤维化。我们还表明，αVbeta6 可以激活 TGFbeta3，而肺上皮中表达的另一种整合素 (αVbeta8) 可以激活 TGFbeta1/3。 这项工作的目标是确定体内整合素介导的 TGFbeta1 激活的作用。为此，我们培育了具有 TGFbeta1 基因突变的敲入小鼠，该基因编码 LAP 前肽中的非功能性整合素结合位点。这些小鼠的表型（命名为 TGFbeta1-RGE）再现了 TGFbeta1-/- 表型最突出的方面：严重的多器官炎症，导致 3-4 周龄时死亡。这一重要发现表明整合素介导的 TGFbeta1 激活可能发生在大多数 TGFbeta1 效应的上游。这项工作的具体目的是（1）与 TGFbeta1-/- 小鼠相比，表征 TGFbeta1-RGE 小鼠，（2）测试体内唯一激活 TGFbeta1 的整合素是 alphaVbeta6 和 alphaVbeta8 的假设，以及（3）测试某些整合素 KO 小鼠（alphaV-/- 和 (beta8-/-) 是由于 TGFbeta1 和 TGFbeta3 激活联合缺乏所致。这些研究将进一步阐明RGD结合整合素在TGFbeta生物学中的作用，并为其在肺病理学中的作用的重要研究提供基础。