Infectious and Inflammatory Disease Center, Sanford-Burnham Medical Research Institute, La Jolla, California, USA.
FASEB J. 2011 Aug;25(8):2700-10. doi: 10.1096/fj.10-167676. Epub 2011 May 4.
Autophagy is one of the downstream effector mechanisms for elimination of intracellular microbes following activation of the Toll-like receptors (TLRs). Although the detailed molecular mechanism for this cellular process is still unclear, Beclin 1, a key molecule for autophagy, has been suggested to play a role. Heat shock protein 90 (Hsp90) is a molecular chaperone that regulates the stability of signaling proteins. Herein, we show that Hsp90 forms a complex with Beclin 1 through an evolutionarily conserved domain to maintain the stability of Beclin 1. In monocytic cells, geldanamycin (GA), an Hsp90 inhibitor, effectively promoted proteasomal degradation of Beclin 1 in a concentration-dependent (EC(50) 100 nM) and time-dependent (t(50) 2 h) manner. In contrast, KNK437/Hsp inhibitor I had no effect. Hsp90 specifically interacted with Beclin 1 but not with other adapter proteins in the TLR signalsome. Treatment of cells with GA inhibited TLR3- and TLR4-mediated autophagy. In addition, S. typhimurium infection-induced autophagy was blocked by GA treatment. This further suggested a role of the Hsp90/Beclin 1 in controlling autophagy in response to microbial infections. Taken together, our data revealed that by maintaining the homeostasis of Beclin 1, Hsp90 plays a novel role in TLR-mediated autophagy.
自噬是 Toll 样受体 (TLRs) 激活后消除细胞内微生物的下游效应机制之一。尽管该细胞过程的详细分子机制尚不清楚，但自噬的关键分子 Beclin 1 被认为起作用。热休克蛋白 90 (Hsp90) 是一种调节信号蛋白稳定性的分子伴侣。在此，我们表明 Hsp90 通过进化保守结构域与 Beclin 1 形成复合物，以维持 Beclin 1 的稳定性。在单核细胞中，Hsp90 抑制剂格尔德霉素 (GA) 以浓度依赖性（EC50100 nM）和时间依赖性（t502 h）的方式有效促进 Beclin 1 的蛋白酶体降解。相比之下，KNK437/Hsp 抑制剂 I 没有作用。Hsp90 特异性地与 Beclin 1 而不是 TLR 信号转导体中的其他衔接蛋白相互作用。用 GA 处理细胞可抑制 TLR3 和 TLR4 介导的自噬。此外，GA 处理可阻断 S. typhimurium 感染诱导的自噬。这进一步表明 Hsp90/Beclin 1 在控制微生物感染引起的自噬中的作用。总之，我们的数据揭示了 Hsp90 通过维持 Beclin 1 的内稳态，在 TLR 介导的自噬中发挥新的作用。
