Signal transduction mechanisms for the regulation of EGF receptor gene expression.

1.小细胞肺癌(SCLC)细胞系中EGFR基因表达的调控从小细胞肺癌细胞系Lul34中分离到一株形态发生改变的突变体AD320，该突变体以锚定依赖的方式生长。在该变异体中可检测到EGFR mRNA和EGF结合活性。基因表达发生明显变化，包括肌酸脱氢酶B基因表达下降，c-mye基因表达增加。突变体中的EGFR似乎是跨膜信号机制的活跃部分，因为在ISGF和肿瘤促进剂TPA处理后，c-fos和c-jun mRNA积累，随后是EGFR和c-myc mRNA积累。因此，尽管EGFR基因是结构性表达的，但对EGFR基因的诱导调控机制在该变异体中被激活。表皮生长因子…的独特诱导更多的受体磷酸化和早期反应基因的表达由蛋白激酶C抑制剂CalpBostin-c来实现。已知Calphostin-c在体外以一种光依赖的方式结合蛋白激酶C的调节域和T6抑制激酶的活性。我们发现，当EGF受体高表达的鳞癌细胞株NA和肺腺癌细胞株A549被TILS化合物处理时，Calphostin-c以光依赖的方式诱导独特的细胞反应。照射后30min观察到EGF受体的磷酸化。磷酸氨基酸分析表明丝氨酸和苏氨酸残基上存在受体磷酸化。在光处理下，EGF结合活性显著降低，这表明磷酸化的细胞表面受体明显内化。此外，Cal-c还显著增强了e-fos和c-jun基因的表达。这些结果表明，Calphostin-c诱导EGF受体独特的磷酸化并激活信号转导途径，这似乎不同于EGF和TPA激活的途径。较少

1. Regulation of EGF receptor (EGFR) gene expression in a variant isolated from an EGFR-deficient small cell lung carcinoma (SCLC) cell line.Most cell lines derived from SCLC grow in an anchorage-independent manner ; they neither possess EGF binding activity nor express EGFR mRNA. A variant AD320, which grew In an anchorage-dependent manner with altered morphology, was isolated from SCLC cell line Lul34. EGFR mRNA and EGF binding activity could be detected In the varlant. Drastle change In gene expression Including a decrease of creatlne klnase B mRNA and an increase of c-mye mRNA were observed. The EGFR In the variant appeared to be an active part of the transmembrane signaling machinery since c-fos and c-jun mRNA accumulated after ISGF and a tumor promoter TPA treatment, followed by EGFR mRNA and c-myc mRNA accumulation. Thus, the Inducible regulatory mechanism for EGFR gene was activated in the variant even though the EGFR gene was constitutively expressed.2. Unique induction of EGF … More receptor phosphorylation and early-response gene expression by protein kinase C inhibitor Calpbostin-c.Calphostin-c is known to bind the regulatory domain of protein kinase C and t6 inhibit kinase activity in vitro in a light dependent fashion. We have found that calphostin-c induces unique cellular responses in a light dependent fashion when the EGF receptor hyperproducing squamous carcinoma cell line NA and the lung adenocareinoma cell line A549 were treated with tills compound. Phosphorylation of EGF receptor was observed 30 min after calphostln-c/llght treatment. Phosphoamino acid analysis revealed the receptor phosphorylation on serine and threonine residues. EGF binding activity was markedly reduced when treated under light, suggesting apparent internalization of the phosphorylated cell surface receptor. Furthermore, cal-c markedly enhoned e-fos and c-jun gene expression. These results suggest that calphostin-c induces a unique phosphorylation of EGF receptor and activate signal transduction pathway, which appears to be different from EGF- and TPA-activated pathways. Less