Biliverdin targets enolase and eukaryotic initiation factor 2 (eIF2α) to reduce the growth of intraerythrocytic development of the malaria parasite Plasmodium falciparum

• Published in: Scientific reports 2016-02, Vol.6 (1), p.22093-22093, Article 22093
• Main Authors: Alves, Eduardo, Maluf, Fernando V., Bueno, Vânia B., Guido, Rafael V. C., Oliva, Glaucius, Singh, Maneesh, Scarpelli, Pedro, Costa, Fahyme, Sartorello, Robson, Catalani, Luiz H., Brady, Declan, Tewari, Rita, Garcia, Celia R. S.
• Format: Article
• Language: English
• Subjects: 38; 38/77; 631/45; 631/92/607; 82/16; 82/29; 82/58; 82/80; 82/83; 96; 96/31; Amino Acid Sequence; Biliverdin; Biliverdine - metabolism; Biliverdine - pharmacology; Calorimetry; Erythrocytes; Erythrocytes - metabolism; Erythrocytes - parasitology; Eukaryotic Initiation Factor-2 - antagonists & inhibitors; Eukaryotic Initiation Factor-2 - chemistry; Eukaryotic Initiation Factor-2 - metabolism; Glycolysis; Heme oxygenase (decyclizing); Heme Oxygenase (Decyclizing) - metabolism; Humanities and Social Sciences; Humans; Initiation factor eIF-2α; Malaria; Malaria, Falciparum - metabolism; Models, Molecular; Molecular modelling; multidisciplinary; Oxygenase; Parasites; Phosphopyruvate hydratase; Phosphopyruvate Hydratase - antagonists & inhibitors; Phosphorylation; Plasmodium falciparum; Plasmodium falciparum - metabolism; Protozoan Proteins - antagonists & inhibitors; Science; Science (multidisciplinary); Sequence Alignment; Titration; Toxicity; Vector-borne diseases
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep22093

In mammals, haem degradation to biliverdin (BV) through the action of haem oxygenase (HO) is a critical step in haem metabolism. The malaria parasite converts haem into the chemically inert haemozoin to avoid toxicity. We discovered that the knock-out of HO in P. berghei is lethal; therefore, we investigated the function of biliverdin (BV) and haem in the parasite. Addition of external BV and haem to P. falciparum -infected red blood cell (RBC) cultures delays the progression of parasite development. The search for a BV molecular target within the parasites identified P. falciparum enolase (Pf enolase) as the strongest candidate. Isothermal titration calorimetry using recombinant full-length Plasmodium enolase suggested one binding site for BV. Kinetic assays revealed that BV is a non-competitive inhibitor. We employed molecular modelling studies to predict the new binding site as well as the binding mode of BV to P. falciparum enolase. Furthermore, addition of BV and haem targets the phosphorylation of Plasmodium falciparum eIF2α factor, an eukaryotic initiation factor phosphorylated by eIF2α kinases under stress conditions. We propose that BV targets enolase to reduce parasite glycolysis rates and changes the eIF2α phosphorylation pattern as a molecular mechanism for its action.