Decreased K13 Abundance Reduces Hemoglobin Catabolism and Proteotoxic Stress, Underpinning Artemisinin Resistance

Summary: Increased tolerance of Plasmodium falciparum to front-line artemisinin antimalarials (ARTs) is associated with mutations in Kelch13 (K13), although the precise role of K13 remains unclear. Here, we show that K13 mutations result in decreased expression of this protein, while mislocalization of K13 mimics resistance-conferring mutations, pinpointing partial loss of function of K13 as the relevant molecular event. K13-GFP is associated with ∼170 nm diameter doughnut-shaped structures at the parasite periphery, consistent with the location and dimensions of cytostomes. Moreover, the hemoglobin-peptide profile of ring-stage parasites is reduced when K13 is mislocalized. We developed a pulse-SILAC approach to quantify protein turnover and observe less disruption to protein turnover following ART exposure when K13 is mislocalized. Our findings suggest that K13 regulates digestive vacuole biogenesis and the uptake/degradation of hemoglobin and that ART resistance is mediated by a decrease in heme-dependent drug activation, less proteotoxicity, and increased survival of parasite ring stages. : Artemisinin resistance in P. falciparum is associated with Kelch13 (K13) mutations. Yang et al. report that K13 is located in cytostome-like structures, consistent with a role in hemoglobin uptake. K13 is less abundant in mutants, and hemoglobin catabolism is impaired. The resultant decrease in artemisinin activation likely underpins artemisinin resistance. Keywords: malaria, artemisinin, antimalarial, kelch13, proteomics, SILAC, protein turnover, cytostome