BIOLOGY AND MOLECULAR BIOLOGY OF TRANSFORMING GROWTH FACTOR-BETA

TGF-β的三种不同亚型在哺乳动物中表达。 虽然 这些同种型中的每一种彼此显示出65-85%的同源性， 任何特定同种型的酸序列保守性大于98%， 哺乳动物鸟类和两栖动物之间的联系 这有力地表明 成熟肽将具有某些独特的生物活性。 只有TGF-β 1和2已从天然来源纯化。 所以 我们也许可以比较所有三种异构体的活性， 开发了一种用于表达重组TGF-β 3的系统。 此外，委员会认为， 来开始探索到底是分子的哪个区域 对于同种型特异性结合和活性，我们使用了相同的 表达系统，以表达特定的重组嵌合TGF-β， TGF-β 1、2和3的氨基酸序列的哪些区域是 在成熟肽中相互取代。 这一切成功都 重组TGF-β已经使用序列 高压液相色谱步骤。 的可用性 TGF-β 3使我们能够产生针对这种肽的抗体 现在可以用来检测它在各种实验中的存在， 系统. 此外，TGF-β 3的选择性作用已被确定， 抑制造血细胞的生长， 成纤维细胞，以及抑制某些神经元细胞的存活。 使用嵌合TGF-β构建体，我们已经能够推断， TGF-β分子的中间三分之一足以赋予 同种型特异性生物活性。在与此相关的方面， 在这个项目中，我们正在探索不同的TGF-β亚型的作用， 对保护心肌细胞免受 生长因子如白细胞介素-I和肿瘤坏死 α因子

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.