title: Aquaglyceroporin-null trypanosomes display glycerol transport defects and respiratory-inhibitor sensitivity.
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.
authors.affiliation: The Wellcome Trust Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dow Street, Dundee, United Kingdom.
authors.forename: Laura
authors.initials: L
authors.lastname: Jeacock
authors.affiliation: The Wellcome Trust Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dow Street, Dundee, United Kingdom.
authors.forename: Nicola
authors.initials: N
authors.lastname: Baker
authors.affiliation: Parasite Chemotherapy Unit, Swiss Tropical and Public Health Institute, Basel, Switzerland.|University of Basel, Basel, Switzerland.
authors.forename: Natalie
authors.initials: N
authors.lastname: Wiedemar
authors.affiliation: Parasite Chemotherapy Unit, Swiss Tropical and Public Health Institute, Basel, Switzerland.|University of Basel, Basel, Switzerland.
authors.forename: Pascal
authors.identifier: 0000-0003-3122-1941
authors.initials: P
authors.lastname: Mäser
authors.affiliation: The Wellcome Trust Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dow Street, Dundee, United Kingdom.
authors.forename: David
authors.identifier: 0000-0001-5173-9284
authors.initials: D
authors.lastname: Horn
mesh_terms: D000818:Animals; D051397:Aquaglyceroporins / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D004195:Disease Models, Animal; D004351:Drug Resistance / Q000187:drug effects / Q000502:physiology*; D055786:Gene Knockout Techniques; D005990:Glycerol / Q000378:metabolism; D008549:Melarsoprol / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D014344:Trypanocidal Agents / Q000494:pharmacology; D014347:Trypanosoma brucei gambiense / Q000378:metabolism; D014353:Trypanosomiasis, African / Q000378:metabolism*
chemical_list: D051397:Aquaglyceroporins; D014344:Trypanocidal Agents; D005990:Glycerol; D008549:Melarsoprol