REGULATION OF TRANSFORMING GROWTH FACTORS

转化生长因子（TGF α和TGF β）可以协同诱导 正常哺乳动物细胞的可逆表型转化， 文化 经处理的细胞显示出戏剧性的形态变化， 转化细胞特有的生长特性。 其中一 TGF α是一种有效的促分裂原，结合EGF受体， 诱导EGF样受体相关酪氨酸磷酸化 方式 TGF α的分泌首先在细胞生长时观察到。 但越来越多的证据表明， TGF α也由肿瘤细胞表达。 此外，TGF-α已被 作为骨再吸收的诱导剂， 伴随某些恶性肿瘤的高钙血症。 这些发现表明 TGF α可能在肿瘤生物学中起重要作用。 最近 TGF α的分析也表明，在正常成人中， 组织和高水平的发育胚胎。 我们的目标是确定假定的跨膜前体的作用 并确定前体的加工是否代表 在生长因子的分泌的调节步骤。 另外我们 想要确定TGF α在正常生长中的功能， 发展，并最终了解TGF α的意义 在肿瘤生物学方面的表达。 因此，我们将：（1）执行 额外的cDNA克隆以建立前体的序列;（2） 开发适当的抗体，以确定亚细胞位置的 （3）试图确定是否蛋白水解释放的前体， 生长因子发生在膜的细胞外侧;（4）利用 我们的TGF α表达载体和体外诱变来表征 蛋白水解加工和确定蛋白酶识别位点;（5）使用 TGF α表达载体，以检查TGF α表达的影响 （6）进一步分析TGF α的表达 通过原位杂交分析在发育中的胚胎中;（7）检查 TGF α在正常分裂细胞中的表达;和（8）开始研究， 以调节区域为重点表征TGF α基因。

Transforming growth factors (TGFAlpha and TGFBeta) can cooperatively induce a reversible phenotypic transformation of normal mammalian cells in culture. Treated cells display dramatic morphological changes and acquire growth properties characteristic of transformed cells. One of these factors, TGFAlpha, is a potent mitogen and binds the EGF receptor and induces receptor-associated tyrosine phosphorylation in an EGF-like manner. Secretion of TGFAlpha was first observed when cells were transformed with retroviruses, but accumulating evidence suggests that TGFAlpha is also expressed by tumor cells. In addition, TGFAlpha has been implicated as an inducer of the bone resportion and concomitant hypercalcemia that accompanies some malignancies. These findings suggest that TGFAlpha may play a significant role in tumor biology. Recent analyses of TGFAlpha is also expressed at low levels in normal adult tissues and at high levels in developing embryos. Our goals are to determine the role of the putative transmembrane precursor and to establish whether processing of the precursor represents a regulatory step in the secretion of the growth factor. In addition, we would like to determine the function of TGFAlpha in normal growth and development and, ultimately to understand the significance of TGFAlpha expression in terms of tumor biology. Accordingly, we will: (1) perform additional cDNA cloning to establish the sequence of the precursor; (2) develop appropriate antibodies to determine the subcellular location of the precursor; (3) attempt to determine whether proteolytic release of the growth factor occurs on the extracellular side of the membrane; (4) utilize our TGFAlpha expression vectors and in vitro mutagenesis to characterize proteolytic processing and define protease recognition sites; (5) use TGFAlpha expression vectors to examine the effects of TGFAlpha expression in normal cells and animals; (6) further analyze the expression of TGFAlpha in developing embryos by in situ hybridization analysis; (7) examine TGFAlpha expression in normal dividing cells; and (8) begin studies to characterize the TGFAlpha gene with an emphasis on regulatory regions.