DISTRIBUTION AND FUNCTIONAL ASPECTS OF TGF-BETA-3

一种新型的转化生长因子-β-家族生长抑制因子已被克隆并 从人胎盘cdna中测序；新形式被命名为 转化生长因子-β-3。转化生长因子-β以非活性前体的形式分泌 分子，这些分子随后被蛋白水解性切割以产生 生物活性成熟的二聚体，大小为25 KDa。前兆区域 转化生长因子-β-1和转化生长因子-β-3的序列含有RGD序列。转化生长因子-β 影响细胞的增殖和分化过程， 并特别显示出强烈的生长抑制活性 多种细胞类型，尤其是癌。初步实验 显示转化生长因子-β-3的生长速度至少高出10倍 对包括人肺癌在内的细胞具有抑制活性。 最近，不同的功能，部分地通过特定的 已经证实了转化生长因子-β1和转化生长因子-β2的受体。 由于转化生长因子-β-3是一种新发现的蛋白质及其分布， 其功能和受体结合特性尚不清楚。反- 血清将被提升为前体和合成多肽 成熟形式的转化生长因子-β-3。无交叉反应抗肽免疫球蛋白 将用于分析性地筛选正常和肿瘤细胞以及 免疫荧光法检测组织中转化生长因子-β3的表达。免疫沉淀 免疫亲和层析技术将用于 成熟型转化生长因子-β3及其前体形式的定量和纯化 细胞和组织中的转化生长因子-β1和转化生长因子-β3。纯化的转化生长因子-2 β-3将被用来量化其在各种不同环境中的比活性 转化生长因子-β的特异性功能及其鉴定和表征 细胞表面的受体结合实体。通过刺激 产生细胞外基质(ECM)的某些成分 如纤维连接蛋白(FN)和胶原，并通过防止ECM 通过合成抗催化蛋白进行分解，如 纤溶酶原激活物抑制物(PAI)，转化生长因子-β似乎具有 对维护ECM的完整性具有重要作用。这个 转化生长因子-β3对纤维连接蛋白、胶原和纤溶酶原激活物生成的影响 被评估。失活的转化生长因子-β-3 前体分子通过其RGD与Fn受体结合 序列，创建一个负反馈机制，将被研究。 阻断纤维连接蛋白与其受体的结合将导致 细胞与细胞外基质的粘附力降低。FN受体是 转化细胞中酪氨酸的磷酸化，但不是正常细胞。 转化生长因子-β-3改善转化相关的能力 阻止FN酪氨酸磷酸化的特性 将对受体进行评估。这些研究在中国的意义 了解肿瘤细胞增殖的调控机制 转移可能在两个方面阐明未来治疗的概念 癌症研究的重要领域。

A novel growth inhibitor of the TGF-beta-family has been cloned and sequenced from human placental cDNA; the new form is designated TGF-beta-3. TGF-betas are secreted as inactive precursor molecules, that are subsequently proteolytically cleaved to yield biologically active mature dimers of 25 KDa. The precursor regions of TGF-beta-1 and TGF-beta-3 contain an RGD sequence. TGF-betas influence the proliferation and differentiation processes of cells, and specifically demonstrate potent growth inhibitory activity on many cell types, especially carcinomas. Preliminary experiments showed that TGF-beta-3 exhibited at least 10 fold greater growth inhibitory activity on cells, including a human lung carcinoma. Recently, different functions, partially mediated through specific receptors have been demonstrated for TGF-beta-1 and TGF-beta-2. Since TGF-beta-3 is a newly discovered protein its distribution, functions, and receptor binding characteristics are unknown. Anti- sera will be raised to synthetic peptides of both the precursor and mature forms of TGF-beta-3. Non-cross-reacting anti-peptide IgG will be used analytically to screen normal and neoplastic cells and tissues for TGF-beta-3 by immunofluorescence. Immunoprecipitation and immunoaffinity chromatographic techniques will be employed to quantitate and purify mature TGF-beta-3 and the precursor form of TGF-beta-1 and TGF-beta-3 from cells and tissues. Purified TGF- beta-3 will be used to quantitate its specific activity in various TGF-beta specific functions and to identify and characterize its receptor binding entities on the cell surface. By stimulating the production of certain components of the extracellular matrix (ECM) such as fibronectin (Fn) and collagen, and by preventing ECM breakdown through the synthesis of anticatalytic proteins such as plasminogen activator inhibitor (PAI), TGF-beta appears to have an important effect on maintaining the integrity of the ECM. The influence of TGF-beta-3 on Fn, collagen, and PAI production will be assessed. The possibility that the inactive TGF-beta-3 precursor molecule binds to the Fn receptor through its RGD sequence, creating a negative feedback mechanism, will be examined. Blocking the binding of fibronectin to its receptor would cause decreased adherence of cells to the ECM. The Fn receptor is phosphorylated on tyrosines in transformed but not normal cells. The ability of TGF-beta-3 to ameliorate transformation related properties by preventing tyrosine phosphorylation of the Fn receptor will be evaluated. The significance of these studies in understanding control mechanisms of tumor cell proliferation and metastasis may elucidate concepts for future therapeutics in two important areas of cancer research.