Miller P, DiOrio C, Moyer M, Schnur R C, Bruskin A, Cullen W, Moyer J D
Department of Neurosciences and Cancer, Central Research Division, Pfizer, Inc., Groton, Connecticut 06340.
Cancer Res. 1994 May 15;54(10):2724-30.
Herbimycin A, a benzoquinoid ansamycin, is widely used as an inhibitor of tyrosine kinases. We have examined the effects of herbimycin A and several analogues on p185, the tyrosine kinase encoded by the erbB2 gene in human breast cancer cells. Exposure to 0.35 microM herbimycin A reduced tyrosine phosphorylation of p185 in SKBr3 cells by 80% after 2 h, and the p185 protein level was reduced by 90% after 6 h. The reduction of p185 resulted primarily from increased degradation of p185; cellular protein synthesis was reduced only 16% in SKBr3 cells treated with herbimycin A, RNA synthesis was inhibited only 10%, and erbB2 mRNA levels were unchanged. Examination of the major cellular glycoproteins indicated that most glycoproteins were unaffected under conditions that substantially depleted p185. Studies with cell lines transfected with erbB2 containing defined deletions indicated that susceptibility to the depletion of p185 by herbimycin and its analogues required the domain encoded by amino acids 751-971. The benzoquinoid ansamycins therefore initiate a process of specific degradation of tyrosine kinases by a mechanism that remains unknown.
赫比霉素A是一种苯醌型安莎霉素，被广泛用作酪氨酸激酶抑制剂。我们研究了赫比霉素A及其几种类似物对人乳腺癌细胞中erbB2基因编码的酪氨酸激酶p185的影响。在SKBr3细胞中，暴露于0.35微摩尔的赫比霉素A 2小时后，p185的酪氨酸磷酸化降低了80%，6小时后p185蛋白水平降低了90%。p185的减少主要是由于p185降解增加所致；用赫比霉素A处理的SKBr3细胞中细胞蛋白质合成仅减少16%，RNA合成仅受抑制10%，且erbB2 mRNA水平未改变。对主要细胞糖蛋白的检测表明，在p185大量减少的条件下，大多数糖蛋白未受影响。对转染了含特定缺失erbB2的细胞系的研究表明，赫比霉素及其类似物导致p185减少的敏感性需要由氨基酸751 - 971编码的结构域。因此，苯醌型安莎霉素通过一种尚不清楚的机制启动了酪氨酸激酶的特异性降解过程。
