Artemisinin resistance in rodent malaria - mutation in the AP2 adaptor μ-chain suggests involvement of endocytosis and membrane protein trafficking

Abstract

BackgroundThe control of malaria, caused by Plasmodium falciparum, is hampered by the relentless evolution of drug resistance. Because artemisinin derivatives are now used in the most effective anti-malarial therapy, resistance to artemisinin would be catastrophic. Indeed, studies suggest that artemisinin resistance has already appeared in natural infections. Understanding the mechanisms of resistance would help to prolong the effective lifetime of these drugs. Genetic markers of resistance are therefore required urgently. Previously, a mutation in a de-ubiquitinating enzyme was shown to confer artemisinin resistance in the rodent malaria parasite Plasmodium chabaudi.MethodsHere, for a mutant P. chabaudi malaria parasite and its immediate progenitor, the in vivo artemisinin resistance phenotypes and the mutations arising using Illumina whole-genome re-sequencing were compared.ResultsAn increased artemisinin resistance phenotype is accompanied by one non-synonymous substitution. The mutated gene encodes the μ-chain of the AP2 adaptor complex, a component of the endocytic machinery. Homology models indicate that the mutated residue interacts with a cargo recognition sequence. In natural infections of the human malaria parasite P. falciparum, 12 polymorphisms (nine SNPs and three indels) were identified in the orthologous gene.ConclusionAn increased artemisinin-resistant phenotype occurs along with a mutation in a functional element of the AP2 adaptor protein complex. This suggests that endocytosis and trafficking of membrane proteins may be involved, generating new insights into possible mechanisms of resistance. The genotypes of this adaptor protein can be evaluated for its role in artemisinin responses in human infections of P. falciparum.

Artemisinin Action and Resistance in Plasmodium falciparum

“…A recent review provides a more detailed discussion of possible roles for PI3P/PI3K in ART resistance [60]. Interestingly, a recent study with ART-pressured, resistant rodent parasites also implicates an important role for altered hemoglobin endocytosis in ART resistance [61]. …”

Protein Degradation Systems as Antimalarial Therapeutic Targets

“…Whole-genome sequencing of ART-pressured P. chaubaudi parasites referred to above [74] identified a single mutation: I568T in the mu chain of the AP2 adaptor complex (PCHAS_143590) [79]. In humans the AP2 complex is involved in clathrin-mediated endocytosis [80].…”

“…In humans the AP2 complex is involved in clathrin-mediated endocytosis [80]. Homology modeling studies predict that the I568T mutation alters binding affinity of the PcAP2 μchain to cargo protein undergoing endocytosis [79]. Analysis of parasite isolates from ACT-treated Kenyan children suggested an increased prevalence of S160N/T mutations in PfAP2-μ (PF3D7_1218300) or a E1528D mutation in PfUBP1 in parasites surviving ACT treatment [81].…”

Culture-adapted Plasmodium falciparum isolates from UK travellers: in vitro drug sensitivity, clonality and drug resistance markers

“…Recent published data from studies of artemisinin resistance in the rodent parasite Plasmodium chabaudi has identified a new candidate locus , pcap2mu , encoding the clathrin-associated μ adaptor protein 2 [36]. These authors described potentially important sequence diversity in the P. falciparum homologue, pfap2mu (PF3D7_1218300), between codons 146 and 437, in a series of clinical isolates.…”