Selected cytotoxic gold compounds cause significant inhibition of 20S proteasome catalytic activities

Six structurally diverse cytotoxic gold compounds are reported to cause profound and differential inhibition of the three main catalytic activities of purified 20S proteasome whilst auranofin, an established gold(I) drug in clinical use, is nearly ineffective. In particular, the gold(I) complex [(pbiH)Au(PPh3)]PF6, turns out to be the most potent inhibitor of all three enzyme activities with sub-micromolar IC50 values. The present results further support the view that proteasome inhibition may play a major – yet not exclusive – role in the cytotoxic actions of gold based anticancer agents.

Graphical abstractThe 20S core of proteasome is constituted of two outer rings, composed of seven different α-subunits which serve as an anchor for the 19S regulators and two inner rings, consisting of seven different β-subunits, which contain the three different catalytic sites (caspase-like, trypsin-like, and chymotrypsin-like sites).Figure optionsDownload full-size imageDownload as PowerPoint slide