Inhibition of Plasmepsin V activity demonstrates its essential role in protein export, PfEMP1 display, and survival of malaria parasites

PLoS Biol. 2014 Jul 1;12(7):e1001897. doi: 10.1371/journal.pbio.1001897. eCollection 2014 Jul.

Abstract

The malaria parasite Plasmodium falciparum exports several hundred proteins into the infected erythrocyte that are involved in cellular remodeling and severe virulence. The export mechanism involves the Plasmodium export element (PEXEL), which is a cleavage site for the parasite protease, Plasmepsin V (PMV). The PMV gene is refractory to deletion, suggesting it is essential, but definitive proof is lacking. Here, we generated a PEXEL-mimetic inhibitor that potently blocks the activity of PMV isolated from P. falciparum and Plasmodium vivax. Assessment of PMV activity in P. falciparum revealed PEXEL cleavage occurs cotranslationaly, similar to signal peptidase. Treatment of P. falciparum-infected erythrocytes with the inhibitor caused dose-dependent inhibition of PEXEL processing as well as protein export, including impaired display of the major virulence adhesin, PfEMP1, on the erythrocyte surface, and cytoadherence. The inhibitor killed parasites at the trophozoite stage and knockdown of PMV enhanced sensitivity to the inhibitor, while overexpression of PMV increased resistance. This provides the first direct evidence that PMV activity is essential for protein export in Plasmodium spp. and for parasite survival in human erythrocytes and validates PMV as an antimalarial drug target.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aspartic Acid Endopeptidases / antagonists & inhibitors*
  • Aspartic Acid Proteases / antagonists & inhibitors*
  • Endoplasmic Reticulum / metabolism
  • Erythrocytes / parasitology
  • Humans
  • Oligopeptides / pharmacology*
  • Protein Transport / drug effects
  • Protozoan Proteins / antagonists & inhibitors*
  • Protozoan Proteins / metabolism
  • Sulfonamides / pharmacology*

Substances

  • Oligopeptides
  • Protozoan Proteins
  • Sulfonamides
  • WEHI-916
  • erythrocyte membrane protein 1, Plasmodium falciparum
  • Aspartic Acid Proteases
  • Aspartic Acid Endopeptidases
  • plasmepsin

Grant support

This work was supported by an NHMRC Project Grant (1010326 to JAB), the Human Frontiers Science Program (RGY0073/2012 to JAB), a Ramaciotti Foundation Establishment Grant (3197/2010 to JAB), a CASS Foundation Science and Medicine grant (SM.12.4348 to JAB), the Australian Cancer Research Foundation, and a Victorian State Government Operational Infrastructure Support and Australian Government NHMRC IRIISS. PJS acknowledges CPM/NSTDA grant P-11-00673. AFC is a Howard Hughes International Scholar and JAB is a QEII Fellow of the Australian Research Council. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.