Regulation of protein breakdown by epidermal growth factor in A431 cells.
Regulation of protein breakdown by epidermal growth factor in A431 cells.
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DOI：
10.1016/0014-4827(85)90160-0
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发表时间：
1985-03
影响因子：
3.7
通讯作者：
F. Ballard
中科院分区：
文献类型：
--
作者：
F. Ballard
添加表皮生长因子（EGF）的A431人表皮样癌细胞的培养物中产生的细胞内蛋白质分解的速度增加，不能占EGF处理的细胞裂解物中的蛋白水解增加。为了支持这一观察结果，放线菌酮抑制蛋白质合成不会降低细胞单层中的EGF反应。另一方面，溶酶体蛋白水解功能的抑制剂如亮抑酶肽、长春碱，尤其是弱碱氨，能够阻断EGF增加蛋白质分解的能力。另外的结果表明，EGF的作用是通过刺激自噬介导的。首先，自噬抑制剂3-甲基腺嘌呤降低了EGF的反应，其次，胰岛素通过防止自噬空泡的形成来抑制蛋白质分解的能力被EGF克服。此外，抑制剂和竞争激素的作用与胰高血糖素的作用相似，胰高血糖素是一种已知会增加自噬的激素。EGF对蛋白质分解的反应在彻底洗涤A431单层后持续至少6小时。这一结果与EGF在其他细胞系中的快速逆转作用形成对比。对洗涤并在37 °C下孵育2小时的细胞中结合的EGF的命运的检查显示，与AG 2804转化的成纤维细胞相比，A431细胞表面上保留的每mg蛋白质的EGF多约500倍，这一差异可能解释了EGF对蛋白质分解的作用的不寻常的持久性。
Addition of epidermal growth factor (EGF) to cultures of A431 human epidermoid carcinoma cells produces an increase in the rate of intracellular protein breakdown that cannot be accounted for by increased proteolysis in lysates from EGF-treated cells. In support of this observation, inhibition of protein synthesis with cycloheximide does not reduce the EGF response in cell monolayers. On the other hand, inhibitors of lysosomal proteolytic function such as leupeptin, vinblastine and especially the weak base, ammonia, are able to block the ability of EGF to increase protein breakdown. Additional results suggest that the EGF effect is mediated via a stimulation of autophagy. First, the autophagocytosis inhibitor, 3-methyladenine, reduces the EGF response, and second, the ability of insulin to inhibit protein breakdown by preventing the formation of autophagic vacuoles is overcome by EGF. Moreover, the actions of inhibitors and competing hormones are similar to those reported for glucagon, a hormone known to increase autophagy. The EGF response on protein breakdown persists for at least 6 h after thorough washing of the A431 monolayers. This result contrasts with the rapid reversal of EGF effects in other cell lines. Examination of the fate of bound EGF in cells washed and incubated for 2 h at 37 °C shows that some 500-fold more EGF per mg protein is retained on the surface of A431 cells compared to AG2804-transformed fibroblasts, a difference which probably explains the unusual persistence of the EGF effect on protein breakdown.