肿瘤细胞因癌基因突变、缺氧及营养受限而高度依赖未折叠蛋白反应(unfolded protein response,UPR).细胞通过内质网(endoplasmic reticulum,ER)膜上3个跨膜蛋白感知未折叠蛋白信号,引起未折叠蛋白反应,动态调控内质网折叠能力,一方面通过暂时减缓翻译和加快蛋白质流出减少ER蛋白质折叠负担,另一方面通过转录因子提高伴侣分子合成,增加ER折叠能力.未折叠的蛋白质长时间积聚在ER会对细胞产生毒性,引起不能缓解的ER应激状态,启动细胞凋亡程序.热休克蛋白90 (heat shock protein 90,Hsp90)是一种进化保守的伴侣分子,参与了300多种新生蛋白质的折叠与成熟,其中包括UPR重要信号IRE1α (inositol-requiring en-zyme 1α).Hsp90抑制剂导致细胞产生大量未折叠蛋白质,同时直接诱导IRE1α的降解,从而破坏UPR恢复蛋白质平衡的能力,诱导UPR相关凋亡.目前,Hsp90抑制剂可有效诱导分泌型肿瘤细胞如骨髓瘤以及RAS突变肿瘤UPR途径的凋亡.%Due to oncogene mutation and stressful environments including hypoxia,nutritional stress and pH stress,tumor cells are often subjected to endoplasmic reticulum (ER) protein folding stress.Cellular adaptation to ER stress is achieved by the activation of unfolded protein response (UPR).There are three key transmembrane proteins on the ER membrane to sense and process unfolded protein signals.The outcome of UPR activation involves transient attenuation of protein synthesis,increased capacity for protein trafficking through the ER,protein folding and transport,and increased protein degradation through ER-associated degradation (ERAD).However,above a certain threshold,chronic UPR results in apoptosis.Heat shock protein 90 (Hsp90) is an evolutionarily conserved molecular chaperone,involving in stabilization and activation of over 300 client proteins.Hsp90 inhibitors disrupt folding and maturation of the client proteins,and cause degradation of inositol-requiring enzyme 1α (IRE1α),the essential UPR signal.So far,the inhibitors could effectively elicit UPR-mediated apoptosis of secretory tumors like multiple myeloma and RA S-driven tumors.
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