Lofts F J, Hurst H C, Sternberg M J, Gullick W J
Molecular Oncology Laboratory, Hammersmith Hospital, London, UK.
Oncogene. 1993 Oct;8(10):2813-20.
The neu oncogene is activated by a point mutation within its transmembrane domain that results in the substitution of glutamic acid for valine at position 664, and is associated with constitutive activation of the tyrosine kinase. It has been proposed that the mutation allows for stabilization of homodimers of the receptor that are necessary for transduction of the mitogenic signal. To investigate the role of the alpha-helical transmembrane sequence in the function of neu, we constructed an expression vector to produce a variety of short transmembrane neu proteins, lacking ligand binding or intracellular kinase domains. Such sequences should interact with full-length receptors and prevent receptor dimerization and thus act as specific inhibitors of function. These small proteins all included a pentapeptide from position 661-665, which has been proposed to be necessary for packing. We show that the short transmembrane molecules are expressed at the cell surface and can retard the growth of neu-transformed cells in monolayers, as colonies in soft agar and as tumours in animals. As predicted by molecular modelling, the magnitude of inhibition depended on the nature of the packing surface, suggesting that the neu transmembrane domain is directly involved in neu protein dimerization.
neu癌基因通过其跨膜结构域内的一个点突变而被激活，该突变导致第664位的缬氨酸被谷氨酸取代，并与酪氨酸激酶的组成型激活相关。有人提出，该突变能够使受体同源二聚体稳定，而这对于有丝分裂信号的转导是必需的。为了研究α-螺旋跨膜序列在neu功能中的作用，我们构建了一个表达载体，以产生多种缺少配体结合或细胞内激酶结构域的短跨膜neu蛋白。这些序列应与全长受体相互作用并阻止受体二聚化，从而作为功能的特异性抑制剂。这些小蛋白均包含来自第661 - 665位的一个五肽，有人提出该五肽对于组装是必需的。我们表明，短跨膜分子在细胞表面表达，并且能够抑制单层培养中neu转化细胞的生长、软琼脂中集落的形成以及动物体内肿瘤的生长。正如分子建模所预测的那样，抑制程度取决于组装表面的性质，这表明neu跨膜结构域直接参与neu蛋白的二聚化。
