New parasite treatment with old alcohol drug targeting COP9 signalosome

The Ubiquitin‐Proteasomal System (UPS) is essential for cell survival because it is responsible for the large majority of protein degradation within the cell. Thus, targeting the UPS has emerged as an attractive approach for combating protozoan parasites. Yet, the regulation of UPS‐mediated protein degradation remains poorly understood in clinically important protozoans. We identified COP9 signalosome to be conserved in multiple pathogenic parasites including Leishmania , Trypanosoma, Toxoplasma and Entamoeba . Here, we show that COP9 signalosome is an essential and druggable parasite target that regulates protein degradation. Using Entamoeba histolytica as a model parasite, we found that genetic disruption of COP9 subunit 5 (CSN5) by two independent but complementary approaches, inhibited parasite cell proliferation and viability. Both CSN5 knockdown and dominant negative mutation trapped cullin1 in a neddylated state disrupting UPS activity and protein degradation. Using virtual screening by molecular docking, we identified zinc dithiocarbamate (ZnDTC), a metabolite of the FDA approved alcohol drug disulfiram, as a potential COP9 inhibitor. We found that ZnDTC acts in a COP9‐dependent manner, phenocopy CSN5 gene disruption, and is active against E. histolytica parasites at nanomolar concentrations. In addition, in‐vivo studies revealed that ZnDTC had oral efficacy in clearing E. histolytica parasites in a mouse model that mirrors human amebic colitis. Parasite clearance was assessed by live bioluminescent imaging, amebic culture and immunohistochemistry. Also, ZnDTC treatment promoted resolution of inflammation and tissue damage. Our findings provide insights into how COP9 signalosome regulates parasite protein degradation, and supports COP9 inhibition as a potential anti‐parasite therapy.