Delayed death in the malaria parasite Plasmodium falciparum is caused by disruption of prenylation-dependent intracellular trafficking

PLoS Biol. 2019 Jul 18;17(7):e3000376. doi: 10.1371/journal.pbio.3000376. eCollection 2019 Jul.

Abstract

Apicomplexan parasites possess a plastid organelle called the apicoplast. Inhibitors that selectively target apicoplast housekeeping functions, including DNA replication and protein translation, are lethal for the parasite, and several (doxycycline, clindamycin, and azithromycin) are in clinical use as antimalarials. A major limitation of such drugs is that treated parasites only arrest one intraerythrocytic development cycle (approximately 48 hours) after treatment commences, a phenotype known as the 'delayed death' effect. The molecular basis of delayed death is a long-standing mystery in parasitology, and establishing the mechanism would aid rational clinical implementation of apicoplast-targeted drugs. Parasites undergoing delayed death transmit defective apicoplasts to their daughter cells and cannot produce the sole, blood-stage essential metabolic product of the apicoplast: the isoprenoid precursor isopentenyl-pyrophosphate. How the isoprenoid precursor depletion kills the parasite remains unknown. We investigated the requirements for the range of isoprenoids in the human malaria parasite Plasmodium falciparum and characterised the molecular and morphological phenotype of parasites experiencing delayed death. Metabolomic profiling reveals disruption of digestive vacuole function in the absence of apicoplast derived isoprenoids. Three-dimensional electron microscopy reveals digestive vacuole fragmentation and the accumulation of cytostomal invaginations, characteristics common in digestive vacuole disruption. We show that digestive vacuole disruption results from a defect in the trafficking of vesicles to the digestive vacuole. The loss of prenylation of vesicular trafficking proteins abrogates their membrane attachment and function and prevents the parasite from feeding. Our data show that the proximate cause of delayed death is an interruption of protein prenylation and consequent cellular trafficking defects.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antimalarials / pharmacology
  • Apicoplasts / metabolism*
  • Cell Death / drug effects
  • Hemiterpenes / metabolism
  • Hemiterpenes / pharmacology
  • Humans
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism*
  • Intracellular Space / parasitology
  • Malaria, Falciparum / parasitology
  • Metabolomics / methods
  • Organophosphorus Compounds / metabolism
  • Organophosphorus Compounds / pharmacology
  • Plasmodium falciparum / drug effects
  • Plasmodium falciparum / metabolism*
  • Plasmodium falciparum / physiology
  • Protein Prenylation / drug effects
  • Protein Transport / drug effects
  • Protozoan Proteins / metabolism*
  • Vacuoles / drug effects
  • Vacuoles / metabolism
  • Vacuoles / parasitology

Substances

  • Antimalarials
  • Hemiterpenes
  • Organophosphorus Compounds
  • Protozoan Proteins
  • isopentenyl pyrophosphate

Grant support

This work was funded through grants from the Australian National Health and Medical Research Council (grants 1062504, 628704) https://www.nhmrc.gov.au/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.