Au4 cluster inhibits human thioredoxin reductase activity via specifically binding of Au to Cys189

Studies have shown that Au triggers tumor cell apoptosis by directly inhibiting human thioredoxin re-ductase (hTrxR), thus making Au potential drugs for cancer treatment. However, the exact molecular me-chanism of Au inhibiting hTrxR has never been demonstrated via experimental and theoretical studies. Here, we synthesized an Au4 cluster coated by an artificial RGD peptide. This gold cluster can bind with hTrxR (KD: & SIM;1.74 mu M) in vitro, and significantly inhibit hTrxR activity in tumor cells. To analyze the un-derlying mechanism, we established hTrxR-overexpressing tumor cells and fished Au-hTrxR adducts from tumor cells previously treated by Au clusters. Using single-particle cryo-electron microscopy (Cryo-EM) and mass spectra (MS), we found unexpectedly that, Au (I) ion, metabolism of Au cluster, specifically binds to the Cys189 of hTrxR. Molecular dynamic simulation revealed such specific Au-Cys189 binding effectively broke the electron transfer from Sec498 of hTrxR to Cys32 of thioredoxin. This inhibition of hTrxR activity by Au4 cluster induced ROS-regulated tumor cell apoptosis and significantly suppressed tumor growth in an A549 lung cancer xenograft model. In summary, this study revealed the structural mechanism of Au in-hibiting hTrxR activity and shed light to the design and application of novel hTrxR-inhibitory anti-tumor nanodrugs.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Studies have shown that gold clusters inhibit human thioredoxin reductase, leading to tumor cell apoptosis, and may serve as potential drugs for cancer treatment. This study reveals the structural mechanism of gold inhibiting enzyme activity and provides insights for the design of novel anti-tumor nanodrugs.