Lehtola L, Sistonen L, Koskinen P, Lehväslaiho H, Di Renzo M F, Comoglio P M, Alitalo K
Laboratory of Cancer Biology, Department of Pathology, Helsinki, Finland.
J Cell Biochem. 1991 Jan;45(1):69-81. doi: 10.1002/jcb.240450114.
The neu receptor oncoprotein tyrosine kinase, capable of transforming cultured fibroblasts and causing mammary carcinomas in transgenic mice, carries a point mutation in its transmembrane domain and shows a constitutive tyrosine kinase activity. We analyzed the neu tyrosine kinase and its substrates in transfected NIH 3T3 fibroblasts by phosphotyrosine immunoblotting. Tyrosine phosphorylated proteins were similar but not identical in epidermal growth factor (EGF)-stimulated cells expressing the human EGF receptor (EGFR) or a chimeric EGFR/neu receptor but differed from phosphotyrosyl proteins constitutively expressed in neu oncogene-transformed cells. The neu oncoprotein in the latter cells was phosphorylated in tyrosine in a ligand-independent manner and had a shortened half-life in comparison with the normal neu protein. Tumor promoter pretreatment inhibited ligand-induced receptor tyrosine phosphorylation and decreased tyrosine phosphorylated neu oncoprotein. Prolonged pretreatment with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) also prevented the induction of immediate early growth factor-regulated genes in response to neu activation. Expression of the neu oncogene but not the protooncogene in NIH 3T3 cells was associated with enhanced levels of the jun and fos oncoproteins and loss of serum growth factor induction of immediate early mRNA responses. The constitutively activated neu oncoprotein tyrosine kinase thus deregulates cellular genomic responses to growth factors.
神经受体癌蛋白酪氨酸激酶能够使培养的成纤维细胞发生转化，并在转基因小鼠中引发乳腺癌，其跨膜结构域存在一个点突变，且具有组成型酪氨酸激酶活性。我们通过磷酸酪氨酸免疫印迹法分析了转染的NIH 3T3成纤维细胞中的神经酪氨酸激酶及其底物。在表达人表皮生长因子受体（EGFR）或嵌合型EGFR/神经受体的表皮生长因子（EGF）刺激细胞中，酪氨酸磷酸化蛋白相似但不完全相同，这与在神经癌基因转化细胞中组成型表达的磷酸酪氨酸蛋白不同。后一种细胞中的神经癌蛋白以不依赖配体的方式在酪氨酸位点磷酸化，与正常神经蛋白相比半衰期缩短。肿瘤启动子预处理可抑制配体诱导的受体酪氨酸磷酸化，并降低酪氨酸磷酸化的神经癌蛋白水平。用12 - O - 十四酰佛波醇 - 13 - 乙酸酯（TPA）进行长时间预处理也可防止在神经激活后诱导立即早期生长因子调节基因。在NIH 3T3细胞中，神经癌基因而非原癌基因的表达与jun和fos癌蛋白水平升高以及血清生长因子诱导立即早期mRNA反应的丧失有关。因此，组成型激活的神经癌蛋白酪氨酸激酶会使细胞基因组对生长因子的反应失调。
