Aquaglyceroporin-null trypanosomes display glycerol transport defects and respiratory-inhibitor sensitivity

PLoS Pathog. 2017 Mar 30;13(3):e1006307. doi: 10.1371/journal.ppat.1006307. eCollection 2017 Mar.

Abstract

Aquaglyceroporins (AQPs) transport water and glycerol and play important roles in drug-uptake in pathogenic trypanosomatids. For example, AQP2 in the human-infectious African trypanosome, Trypanosoma brucei gambiense, is responsible for melarsoprol and pentamidine-uptake, and melarsoprol treatment-failure has been found to be due to AQP2-defects in these parasites. To further probe the roles of these transporters, we assembled a T. b. brucei strain lacking all three AQP-genes. Triple-null aqp1-2-3 T. b. brucei displayed only a very moderate growth defect in vitro, established infections in mice and recovered effectively from hypotonic-shock. The aqp1-2-3 trypanosomes did, however, display glycerol uptake and efflux defects. They failed to accumulate glycerol or to utilise glycerol as a carbon-source and displayed increased sensitivity to salicylhydroxamic acid (SHAM), octyl gallate or propyl gallate; these inhibitors of trypanosome alternative oxidase (TAO) can increase intracellular glycerol to toxic levels. Notably, disruption of AQP2 alone generated cells with glycerol transport defects. Consistent with these findings, AQP2-defective, melarsoprol-resistant clinical isolates were sensitive to the TAO inhibitors, SHAM, propyl gallate and ascofuranone, relative to melarsoprol-sensitive reference strains. We conclude that African trypanosome AQPs are dispensable for viability and osmoregulation but they make important contributions to drug-uptake, glycerol-transport and respiratory-inhibitor sensitivity. We also discuss how the AQP-dependent inverse sensitivity to melarsoprol and respiratory inhibitors described here might be exploited.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aquaglyceroporins / metabolism*
  • Biological Transport / drug effects
  • Disease Models, Animal
  • Drug Resistance / drug effects
  • Drug Resistance / physiology*
  • Gene Knockout Techniques
  • Glycerol / metabolism
  • Melarsoprol / pharmacology
  • Mice
  • Mice, Inbred BALB C
  • Trypanocidal Agents / pharmacology
  • Trypanosoma brucei gambiense / metabolism
  • Trypanosomiasis, African / metabolism*

Substances

  • Aquaglyceroporins
  • Trypanocidal Agents
  • Glycerol
  • Melarsoprol