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

Abstract

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.

Evidence for Regulation of Hemoglobin Metabolism and Intracellular Ionic Flux by the Plasmodium falciparum Chloroquine Resistance Transporter

“…Hb is present at low millimolar concentrations in the RBC cytoplasm and is imported into the DV via cytostomes or endocytic vesicles 42 , 43 . In the DV, Hb catabolism employs aspartic and cysteine proteases that generate oligopeptides 44 as well as free Fe 2+ -heme (which is biomineralized into chemically inert hemozoin 8 , 45 – 47 ). Oligopeptides are degraded by the Cl − dependent exopeptidase dipeptidyl aminopeptidase 1 (PfDPAP1) and the Zn 2+ and/or Mn 2+ -dependent peptidases falcilysin, aminopeptidase P (PfAPP), and aminopeptidase N (PfA-M1).…”

Complete Molecular and Immunoprotective Characterization of Babesia microti Enolase

“…Surface expressed enolase has been identified as a plasminogen receptor, which can be subsequently converted into active plasmin, a strong serine protease facilitating the host invasion process ( Pancholi, 2001 ; Ghosh and Jacobs-Lorena, 2011 ; Diaz-Ramos et al, 2012 ). In recent years, a variety of pathogenic parasites have also been found to express enolase on their surface, and it is thus thought to aid with host invasion ( Figueiredo et al, 2015 ; Alves et al, 2016 ; Mahana et al, 2016 ). Remarkably, enolase has also been identified on the surface of vector-borne pathogens (e.g., Plasmodium falciparum and Borrelia burgdorferi ), and plays an important role during pathogen invasion of vector gut by binding mammalian plasminogen ( Ghosh et al, 2011 ; Toledo et al, 2012 ).…”

Porphyrin Derivative Nanoformulations for Therapy and Antiparasitic Agents

“…The host catalytically degrades hemin into biliverdin (BV) [197]. Nanomolar concentration of BV can delay the intraerythrocytic development of P. falciparum by targeting parasite enolase [198]. Moreover, the malaria digestive vacuole (DV), where hemoglobin degradation and hemozoin formation takes place, is also an important compartment for calcium homeostasis [199].…”