Journal
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Volume 316, Issue 4, Pages 1178-1185Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.bbrc.2004.03.003
Keywords
AQP9; aquaglyceroporin; arsenic trioxide; trisenox; acute promyelocytic leukemia
Categories
Funding
- NEI NIH HHS [EY11239] Funding Source: Medline
- NHLBI NIH HHS [HL48268, HL33991] Funding Source: Medline
- NIEHS NIH HHS [ES10344] Funding Source: Medline
- NIGMS NIH HHS [GM55425] Funding Source: Medline
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Aquaglyceroporins are channels that allow downhill movement of uncharged solutes such as glycerol and urea. Arsenic trioxide has recently been shown to be translocated by mouse mAQP7 and rat rAQP9. In this study we examined the ability of the four known human members of the aquaglyceroporin family, hAQP3, hAQP7, hAQP9, and hAQP10, to facilitate As(OH)(3) movement in Xenopus oocytes. The order of effectiveness as an As(III) transporter was found to be hAQP9 > hAQP7, with little or no transport by hAQP3 or hAQP10. From comparison with the crystal structure of the bacterial homologue GlpF and the bovine erythrocyte water channel bAQP1, AQP9 residues Phe-64 and Arg-219 are predicted to serve as part of the selectivity filter. The requirement for Phe-64 and Arg-219 in arsenic trioxide translocation was examined by site-directed mutagenesis of rAQP9, taking advantage of the fact that rat AQP9 catalyzes (73)AS(OH)(3) uptake in Saccharomyces cerevisiae and in oocytes. R219A, R219K, F64A, F64T, and F64W were expressed in both yeast and oocytes, and permeability of arsenic trioxide and glycerol was measured. A lysine but not an alanine residue could substitute for the highly conserved Arg-219, indicating that a positive charge is required at the entry to the channel. In contrast, the phenylalanine residue, which is believed to position substrates near the conserved arginine, was not required for either arsenic trioxide or glycerol uptake. The results support the hypothesis that arsenic trioxide and glycerol use the same translocation pathway in AQP9. (C) 2004 Elsevier Inc. All rights reserved.
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