Defining the metabolic network of the malaria parasite reveals an essential lipid regulator

Cobbold SA1, Dumont L1, Marapana D2, Triglia T2, Ralph SA1, Cowman AF2, Tilley L1 and McConville MJ1

  1. Bio21 Institute, University of Melbourne, Melbourne, VIC, Australia.
  2. Walter and Eliza Hall Institute, Melbourne, VIC, Australia.

Asexual development of the malaria parasite is associated with major restructuring of both parasite and host erythrocyte metabolism. Most current antimalarials target metabolic processes - so in the search for novel antimalarials - it is crucial to understand the parasite’s total metabolic capacity and identify which metabolic enzymes are essential. To comprehensively define the metabolic changes that occur in human erythrocytes following malaria infection we utilized an approach that approximates a global stable-isotope labelling strategy. Using untargeted LC-MS we traced the fate of all major carbon sources using 13C-labelled substrates. Differential analyses of all mass/charge features between infected and uninfected cells has led to a draft metabolome of the malaria parasite. The draft metabolome constitutes 43% of the expected metabolome of the parasite (via genomic reconstructions), however 112 observed metabolites did not match to the expected metabolome. To further explore this ’dark’ metabolome and validate the accuracy of the draft metabolome we targeted potential enzymes with no defined function which could potentially participate in the dark metabolome. CRISPR/Cas9 was used to generate a dual inducible knock-down system for 17 genes encoding uncharacterized metabolic enzymes, including a member of the Haloacid Dehalogense family (HAD5). We demonstrate that HAD5 is essential to normal parasite development and mediates lipid metabolism via dephosphorylating phosphatidate into diacylglycerol species. This lipid regulator was previously unrecognised in the malaria parasite and demonstrates how exploration of the dark metabolome of the parasite could lead to novel antimalarial targets.