The apicoplast link to fever-survival and artemisinin-resistance in the malaria parasite.

The emergence and spread of Plasmodium falciparum parasites resistant to front-line antimalarial artemisinin-combination therapies (ACT) threatens to erase the considerable gains against the disease of the last decade. Here, we develop a large-scale phenotypic screening pipeline and use it to carry out a large-scale forward-genetic phenotype screen in P. falciparum to identify genes allowing parasites to survive febrile temperatures. Screening identifies more than 200 P. falciparum mutants with differential responses to increased temperature. These mutants are more likely to be sensitive to artemisinin derivatives as well as to heightened oxidative stress. Major processes critical for P. falciparum tolerance to febrile temperatures and artemisinin include highly essential, conserved pathways associated with protein-folding, heat shock and proteasome-mediated degradation, and unexpectedly, isoprenoid biosynthesis, which originated from the ancestral genome of the parasite's algal endosymbiont-derived plastid, the apicoplast. Apicoplast-targeted genes in general are upregulated in response to heat shock, as are other Plasmodium genes with orthologs in plant and algal genomes. Plasmodium falciparum parasites appear to exploit their innate febrile-response mechanisms to mediate resistance to artemisinin. Both responses depend on endosymbiont-derived genes in the parasite's genome, suggesting a link to the evolutionary origins of Plasmodium parasites in free-living ancestors

A novel Modulator of Ring Stage Translation (MRST) gene alters artemisinin sensitivity in Plasmodium falciparum

The implementation of artemisinin (ART) combination therapies (ACTs) has greatly decreased deaths caused by Plasmodium falciparum malaria, but increasing ACT resistance in Southeast Asia and Africa could reverse this progress. Parasite population genetic studies have identified numerous genes, single-nucleotide polymorphisms (SNPs), and transcriptional signatures associated with altered artemisinin activity with SNPs in the Kelch13 (K13) gene being the most well-characterized artemisinin resistance marker. However, there is an increasing evidence that resistance to artemisinin in P. falciparum is not related only to K13 SNPs, prompting the need to characterize other novel genes that can alter ART responses in P. falciparum. In our previous analyses of P. falciparum piggyBac mutants, several genes of unknown function exhibited increased sensitivity to artemisinin that was similar to a mutant of K13. Further analysis of these genes and their gene co-expression networks indicated that the ART sensitivity cluster was functionally linked to DNA replication and repair, stress responses, and maintenance of homeostatic nuclear activity. In this study, we have characterized PF3D7_1136600, another member of the ART sensitivity cluster. Previously annotated as a conserved Plasmodium gene of unknown function, we now provide putative annotation of this gene as a Modulator of Ring Stage Translation (MRST). Our findings reveal that the mutagenesis of MRST affects gene expression of multiple translation-associated pathways during the early ring stage of asexual development via putative ribosome assembly and maturation activity, suggesting an essential role of MRST in protein biosynthesis and another novel mechanism of altering the parasite’s ART drug response

Inconsistencies in sulphur dioxide emissions from the Canadian oil sands and potential implications

atellite-derived and reported sulphur dioxide (SO2) emissions from the Canadian oil sands are shown to have been consistent up to 2013. Post-2013, these sources of emissions data diverged, with reported emissions dropping by a factor of two, while satellite-derived emissions for the region remained relatively constant, with the discrepancy (satellite-derived emissions minus reported emissions) peaking at 50 kT(SO2) yr-1 around 2016. The 2013-2014 period corresponds to when new flue-gas desulphurization units came on-line. Previous work has established a high level of consistency between at-stack SO2 emissions observations and satellite estimates, and surface monitoring network SO2 concentrations over the same multi-year period show similar trends as the satellite data, with a slight increase in concentrations post-2013. No clear explanation for this discrepancy currently exists. The implications of the discrepancy towards estimated total sulphur deposition to downwind ecosystems were estimated relative to 2013 emissions levels, with the satellite-derived values leaving the area of regional critical load exceedances of aquatic ecosystems largely unchanged from 2013 values, 335,000 km2, and reported values potentially decreasing this area to 185,000 km2

Chemogenomic profiling of a Plasmodium falciparum transposon mutant library reveals shared effects of dihydroartemisinin and bortezomib on lipid metabolism and exported proteins

The antimalarial activity of the frontline drug artemisinin involves generation of reactive oxygen species (ROS) leading to oxidative damage of parasite proteins. To achieve homeostasis and maintain protein quality control in the overwhelmed parasite, the ubiquitin-proteasome system kicks in. Even though molecular markers for artemisinin resistance like pfkelch13 have been identified, the intricate network of mechanisms driving resistance remains to be elucidated. Here, we report a forward genetic screening strategy that enables a broader identification of genetic factors responsible for altering sensitivity to dihydroartemisinin (DHA) and a proteasome inhibitor, bortezomib (BTZ). Using a library of isogenic piggyBac mutants in P. falciparum, we defined phenotype-genotype associations influencing drug responses and highlighted shared mechanisms between the two processes, which mainly included proteasome-mediated degradation and the lipid metabolism genes. Additional transcriptomic analysis of a DHA/BTZ-sensitive piggyBac mutant showed it is possible to find differences between the two response mechanisms on the specific components for regulation of the exportome. Our results provide further insight into the molecular mechanisms of antimalarial drug resistance

Highly <i>N</i>‑Methylated Peptides from the Antarctic Sponge <i>Inflatella coelosphaeroides</i> Are Active against <i>Plasmodium falciparum</i>

Malaria, caused by the parasite Plasmodium falciparum, continues to threaten much of the world’s population, and there is a pressing need for expanding treatment options. Natural products have been a vital source of such drugs, and here we report seven new highly N-methylated linear peptides, friomaramide B (2) and shagamides A–F (3–8) from the marine sponge Inflatella coelosphaeroides, collected in Antarctic waters, which demonstrate activity against three strains of blood-stage P. falciparum. The planar structures of these metabolites were solved by interpreting NMR data, as well as HRESIMS/MS fragmentation patterns, while Marfey’s analysis was used to establish the configurations of the amino acids. Reisolation of the previously reported compound friomaramide A (1) allowed us to revise its structure. The panel of isolated compounds allowed establishing structure/activity relationships and provided information for future structure optimization for this class of P. falciparum inhibitory metabolites

Design and Synthesis of Orally Bioavailable Piperazine Substituted 4(1H)-Quinolones with Potent Antimalarial Activity: Structure–Activity and Structure–Property Relationship Studies

Malaria deaths have been decreasing over the last 10–15 years, with global mortality rates having fallen by 47% since 2000. While the World Health Organization (WHO) recommends the use of artemisinin-based combination therapies (ACTs) to combat malaria, the emergence of artemisinin resistant strains underscores the need to develop new antimalarial drugs. Recent in vivo efficacy improvements of the historical antimalarial ICI 56,780 have been reported, however, with the poor solubility and rapid development of resistance, this compound requires further optimization. A series of piperazine-containing 4(1H)-quinolones with greatly enhanced solubility were developed utilizing structure–activity relationship (SAR) and structure–property relationship (SPR) studies. Furthermore, promising compounds were chosen for an in vivo scouting assay to narrow selection for testing in an in vivo Thompson test. Finally, two piperazine-containing 4(1H)-quinolones were curative in the conventional Thompson test and also displayed in vivo activity against the liver stages of the parasite

Protein KIC5 is a novel regulator of artemisinin stress response in the malaria parasite Plasmodium falciparum.

Artemisinin combination therapies (ACTs) have led to a significant decrease in Plasmodium falciparum malaria mortality. This progress is now threatened by emerging artemisinin resistance (ART-R) linked originally in SE Asia to polymorphisms in the Kelch propeller protein (K13) and more recently to several other seemingly unrelated genetic mutations. To better understand the parasite response to ART, we are characterizing a P. falciparum mutant with altered sensitivity to ART that was created via piggyBac transposon mutagenesis. The transposon inserted near the putative transcription start site of a gene defined as a "Plasmodium-conserved gene of unknown function," now functionally linked to K13 as the Kelch13 Interacting Candidate 5 protein (KIC5). Phenotype analysis of the KIC5 mutant during intraerythrocytic asexual development identified transcriptional changes associated with DNA stress response and altered mitochondrial metabolism, linking dysregulation of the KIC5 gene to the parasite's ability to respond to ART exposure. Through characterization of the KIC5 transcriptome, we hypothesize that this gene may be essential under ART exposure to manage gene expression of the wild-type stress response at early ring stage, thereby providing a better understanding of the parasite's processes that can alter ART sensitivity