UCSF

A search for effective treatment of African sleeping sickness, a fatal disease caused by the parasite Trypanosoma brucei, necessitates identification and validation of new therapeutic targets. T. brucei, like all eukaryotes, relies on protein kinases to regulate cellular processes; however, little is known about individual kinases to guide drug development. The fungal polyketide hypothemycin covalently inhibits kinases that contain a poorly conserved cysteine preceding the DXG motif (CDXG) in the active site. We found its potent trypanocidal activity both in culture and in mouse model of infection. We developed an unbiased and quantitative chemical proteomics tool, propargyl-hypothemycin, which identified four kinase targets in T. brucei: TbMAPK2, TbGSK3short, and TbCLK1/2. RNA interference (RNAi) knockdown of all twenty-one CDXG kinases showed TbGSK3short and TbCLK1 are essential. Studies in vitro and in intact cells showed hypothemycin covalently inhibits both kinases at physiologically relevant concentrations. Thus we were able to capitalize on the unique mechanism of hypothemycin to identify two potential therapeutic targets for African sleeping sickness.