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Background: Artemisinin monotherapy of Plasmodium falciparum infection is frequently ineffective due to recrudescence. Artemisinin-induced dormancy, shown in vitro and in animal models, provides a plausible explanation. To date, direct evidence of artemisinin-induced dormancy in humans is lacking. Methods: Blood samples were collected from Plasmodium falciparum 3D7- or K13-infected participants before and 48–72 hours after single-dose artesunate (AS) treatment. Parasite morphology, molecular signature of dormancy, capability and dynamics of seeding in vitro cultures, and genetic mutations in the K13 gene were investigated. Results: Dormant parasites were observed in post-AS blood samples of 3D7- and K13-infected participants. The molecular signature of dormancy, an up-regulation of acetyl CoA carboxylase, was detected in 3D7 and K13 samples post-AS, but not in pre-AS samples. Posttreatment samples successfully seeded in vitro cultures, with a significant delay in time to reach 2% parasitemia compared to pretreatment samples. Conclusions: This study provides strong evidence for the presence of artemisinin-induced dormant parasites in P. falciparum infections. These parasites are a likely reservoir for recrudescent infection following artemisinin monotherapy and artemisinin combination therapy (ACT). Combination regimens that target dormant parasites or remain at therapeutic levels for a sufficient time to kill recovering parasites will likely improve efficacy of ACTs.

Upregulation of fatty acid synthase (FASN) is a common event in cancer, although its mechanistic and potential therapeutic roles are not completely understood. In this study, we establish a key role of FASN during transformation. FASN is required for eliciting the anaplerotic shift of the Krebs cycle observed in cancer cells. However, its main role is to consume acetyl-CoA, which unlocks isocitrate dehydrogenase (IDH)-dependent reductive carboxylation, producing the reductive power necessary to quench reactive oxygen species (ROS) originated during the switch from two-dimensional (2D) to three-dimensional (3D) growth (a necessary hallmark of cancer). Upregulation of FASN elicits the 2D-to-3D switch; however, FASN's synthetic product palmitate is dispensable for this process since cells satisfy their fatty acid requirements from the media. In vivo, genetic deletion or pharmacologic inhibition of FASN before oncogenic activation prevents tumor development and invasive growth. These results render FASN as a potential target for cancer prevention studies.

The increasing atmospheric carbon dioxide (CO2) level is calling for more efficient CO2 fixation systems to re-balance the carbon cycle. At the same time, atmospheric CO2 can in principle be a cheap and abundant carbon source for synthesizing various organic compounds. Converting CO2 into useful chemicals can be an ideal solution for a sustainable future. However, due to its high thermodynamic stability and kinetic inertness, the chemical transformation of CO2 into organic compounds usually requires quite harsh conditions. In contrast, nature has evolved several CO2 fixation pathways for synthesizing longer carbon chain compounds from CO2 under ambient conditions. To date, six CO2 fixation pathways have been reported. However, they all contain key carboxylases with intrinsic properties such as structural complexity and oxygen sensitivity that hinder their further engineering and applications. To circumvent these problems, we designed a synthetic CO2 fixation cycle composed of all efficient, simple and oxygen tolerant enzymes and demonstrated its function in vitro.In this work, we utilized the two most active and oxygen-insensitive carboxylases, crotonyl-CoA carboxylase/reductase (Ccr) and phosphoenolpyruvate carboxylase (Ppc) to fix CO2 and bicarbonate, respectively. Our designed cycle is composed of the reductive glyoxylate synthesis (rGS) pathway and the reductive pyruvate synthesis (rPS) pathway. The rGS pathway converts one pyruvate to one glyoxylate and one acetyl-CoA fixing one bicarbonate, while the rPS pathway converts one acetyl-CoA to pyruvate with one CO2 fixed. Together, we obtained a CO2 fixation cycle termed the reductive glyoxylate/pyruvate synthesis (rGPS) cycle.We first validated the feasibility of rGPS with its stepwise reconstitution in vitro. Using a two-pot immobilized enzyme system, we were able to run the rGPS cycle semi-continuously. To further improve its efficiency, we developed electrochemical and enzymatic FAD regeneration systems to run

The increasing atmospheric carbon dioxide (CO2) level is calling for more efficient CO2 fixation systems to re-balance the carbon cycle. At the same time, atmospheric CO2 can in principle be a cheap and abundant carbon source for synthesizing various organic compounds. Converting CO2 into useful chemicals can be an ideal solution for a sustainable future. However, due to its high thermodynamic stability and kinetic inertness, the chemical transformation of CO2 into organic compounds usually requires quite harsh conditions. In contrast, nature has evolved several CO2 fixation pathways for synthesizing longer carbon chain compounds from CO2 under ambient conditions. To date, six CO2 fixation pathways have been reported. However, they all contain key carboxylases with intrinsic properties such as structural complexity and oxygen sensitivity that hinder their further engineering and applications. To circumvent these problems, we designed a synthetic CO2 fixation cycle composed of all efficient, simple and oxygen tolerant enzymes and demonstrated its function in vitro.In this work, we utilized the two most active and oxygen-insensitive carboxylases, crotonyl-CoA carboxylase/reductase (Ccr) and phosphoenolpyruvate carboxylase (Ppc) to fix CO2 and bicarbonate, respectively. Our designed cycle is composed of the reductive glyoxylate synthesis (rGS) pathway and the reductive pyruvate synthesis (rPS) pathway. The rGS pathway converts one pyruvate to one glyoxylate and one acetyl-CoA fixing one bicarbonate, while the rPS pathway converts one acetyl-CoA to pyruvate with one CO2 fixed. Together, we obtained a CO2 fixation cycle termed the reductive glyoxylate/pyruvate synthesis (rGPS) cycle.We first validated the feasibility of rGPS with its stepwise reconstitution in vitro. Using a two-pot immobilized enzyme system, we were able to run the rGPS cycle semi-continuously. To further improve its efficiency, we developed electrochemical and enzymatic FAD regeneration systems to run

We quantified the ozone impact on levels of Zea mays L. cv. Chambord mRNAs encoding C4-phosphoenolpyruvate carboxylase (C4-PEPc), ribulose-l,5-bisphosphate carboxylase/oxygenase small and large subunits (Rubisco-SSU and Rubisco-LSU, respectively) and Rubisco activase (RCA) using real-time RT-PCR. Foliar pigment content, PEPc and Rubisco protein amounts were simultaneously determined. Two experiments were performed to study the ozone response of the 5th and the 10th leaf. For each experiment, three ozone concentrations were tested in open-top chambers: non-filtered air (NF, control) and non-filtered air containing 40 (+40) and 80 nL L-1 (+80) ozone. Regarding the 5th leaf, +40 atmosphere induced a loss in pigmentation, PEPc and Rubisco activase mRNAs. However, it was unable to notably depress carboxylase protein amounts and mRNAs encoding Rubisco. Except for Rubisco mRNAs, all other measured parameters from 5th leaf were depressed by +80 atmosphere. Regarding the 10th leaf, +40 atmosphere increased photosynthetic pigments and transcripts encoding Rubisco and Rubisco activase. Rubisco and PEPc protein amounts were not drastically changed, even if they tended to be increased. Level of C4-PEPc mRNA remained almost stable. In response to +80 atmosphere, pigments and transcripts encoding PEPc were notably decreased. Rubisco and PEPc protein amounts also declined to a lesser extent. Conversely, the level of transcripts encoding both Rubisco subunits and Rubisco activase that were not consistently disturbed tended to be slightly augmented. So, the present study suggests that maize leaves can respond differentially to a similar ozone stress