title: Aquaporin 9 is the major pathway for glycerol uptake by mouse erythrocytes, with implications for malarial virulence.
abstract: Human and rodent erythrocytes are known to be highly permeable to glycerol. Aquaglyceroporin aquaporin (AQP)3 is the major glycerol channel in human and rat erythrocytes. However, AQP3 expression has not been observed in mouse erythrocytes. Here we report the presence of an aquaglyceroporin, AQP9, in mouse erythrocytes. AQP9 levels rise as reticulocytes mature into erythrocytes and as neonatal pups develop into adult mice. Mice bearing targeted disruption of both alleles encoding AQP9 have erythrocytes that appear morphologically normal. Compared with WT cells, erythrocytes from AQP9-null mice are defective in rapid glycerol transport across the cell membrane when measured by osmotic lysis, [(14)C]glycerol uptake, or stopped-flow light scattering. In contrast, the water and urea permeabilities are intact. Although the physiological role of glycerol in the normal function of erythrocytes is not clear, plasma glycerol is an important substrate for lipid biosynthesis of intraerythrocytic malarial parasites. AQP9-null mice at the age of 4 months infected with Plasmodium berghei survive longer during the initial phase of infection compared with WT mice. We conclude that AQP9 is the major glycerol channel in mouse erythrocytes and suggest that this transport pathway may contribute to the virulence of intraerythrocytic stages of malarial infection.
authors.affiliation: Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Yangjian
authors.initials: Y
authors.lastname: Liu
authors.forename: Dominique
authors.initials: D
authors.lastname: Promeneur
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Rojek
authors.forename: Nirbhay
authors.initials: N
authors.lastname: Kumar
authors.forename: Jørgen
authors.initials: J
authors.lastname: Frøkiaer
authors.forename: Søren
authors.initials: S
authors.lastname: Nielsen
authors.forename: Landon S
authors.initials: LS
authors.lastname: King
authors.forename: Peter
authors.initials: P
authors.lastname: Agre
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Carbrey
mesh_terms: D000818:Animals; D051398:Aquaporin 1 / Q000378:metabolism; D020346:Aquaporins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D002463:Cell Membrane Permeability; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism*; D008288:Malaria / Q000235:genetics / Q000378:metabolism* / Q000469:parasitology* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D010962:Plasmodium berghei / Q000472:pathogenicity*; D015996:Survival Rate; D014774:Virulence
chemical_list: C496021:Aqp1 protein, mouse; C491638:Aqp9 protein, mouse; D020346:Aquaporins; D051398:Aquaporin 1; D005990:Glycerol