BIOLOGY AND MOLECULAR BIOLOGY OF TRANSFORMING GROWTH FACTOR-BETA

在哺乳动物中表达三种不同的转化生长因子-β亚型。虽然 这些亚型中的每一种都显示出65%-85%的同源性，即氨基酸 任何特定异构体的酸序列保守性都大于98% 在哺乳动物、鸟类和两栖动物之间。这强烈地表明 成熟的多肽将具有某些独特的生物活性。 只有转化生长因子-β1和2是从天然来源中提纯的。所以 我们也许能够比较这三种异构体的活性，我们 建立了重组转化生长因子-β3的表达系统。 开始探索分子的哪些区域负责 对于特定于异构体的结合和活性，我们使用了相同的 表达特异性嵌合转化生长因子-β的表达系统 转化生长因子-β1、2和3的氨基酸序列的哪些区域是 在成熟肽中相互替代。这其中的每一个 重组转化生长因子-β已通过一种序列纯化为均一 高压液相色谱步骤。是否可以使用 转化生长因子-β3使我们能够提高这种多肽的抗体。 现在可以用来检测它在各种实验中的存在 系统。此外，转化生长因子-β3的选择性作用已被证实。 在抑制造血细胞的生长，在胎儿的迁移中 并抑制某些神经细胞的存活。 使用嵌合的转化生长因子-β结构，我们已经能够推断 转化生长因子-β分子的中间三分之一足以赋予 具有异构体特异性的生物活性。在与此相关的一个方面 项目，我们正在探索不同的转化生长因子-β亚型的影响。 论动作对心肌细胞损伤的保护作用 白介素I等生长因子与肿瘤坏死 因子-阿尔法。

Three distinct isoforms of TGF-beta are expressed in mammals. Although each of these isoforms shows 65-85% homology to each other, the amino acid sequence of any particular isoform is conserved greater than 98% between mammalian, avian, and amphibian species. This strongly suggests that the mature peptides will have certain unique biological activities. Only TGF-beta's 1, and 2 have been purified from natural sources. So that we might be able to compare the activities of all three isoforms, we developed a system for expression of recombinant TGF-beta 3. Moreover, to begin to explore exactly which regions of the molecule are responsible for isoform-specific binding and activity, we have used this same expression system to express specific recombinant chimeric TGF-beta's in which regions of the amino acid sequence of TGF-beta's 1, 2, and 3 are substituted for each other in the mature peptide. Each of these recombinant TGF-beta's has been purified to homogeneity using a sequence of high pressure liquid chromatography steps. The availability of TGF-beta 3 has permitted us to raise antibodies against this peptide which can now be used to detect its presence in a variety of experimental systems. Moreover, selective effects of TGF-beta 3 have been identified in inhibition of the growth of hematopoietic cells, in migration of fetal fibroblasts, and in inhibiting the survival of certain neuronal cells. Using the chimeric TGF-beta constructs, we have been able to deduce that the middle third of the TGF-beta molecule is sufficient to confer isoform-specific biological activity. In a related aspect of this project, we are exploring the effects of the different TGF-beta isoforms on protection of cardiac myocytes from damage resulting from the action of growth factors such as interleukin-I and tumor necrosis factor-alpha.