Journal
CELLULAR PHYSIOLOGY AND BIOCHEMISTRY
Volume 27, Issue 6, Pages 749-756Publisher
KARGER
DOI: 10.1159/000330083
Keywords
Aquaporin 10; Glycerol; Urea; Channel; Carrier; Transporter
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Funding
- Japan Society for the Promotion of Science, Japan [20590151]
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Background/Aims: Although aquaglyceroporins have been generally believed to operate in a channel mode, which is of nonsaturable nature, for glycerol as well as for water, we recently found that human aquaporin 9 (hAQP9) operates in a carrier-mediated mode, which is of saturable nature, for glycerol. Based on the finding, we assumed that such a characteristic might be shared by the other aquaglyceroporins and examined the functional characteristics of hAQP10, which is an intestine-specific aquaglyceroporin. Methods: Transport assays were conducted using Xenopus laevis oocytes expressing hAQP10 derived from the microinjected cRNA. Results: The transport of glycerol by hAQP10 was found to be highly saturable with a Michaelis constant of 10.4 mu M and specifically inhibited by several glycerol analogs such as monoacetin. Furthermore, when glycerol was preloaded in hAQP10-expressing oocytes, its efflux was trans-stimulated by extracellular glycerol. These results indicate the involvement of a carrier-mediated mechanism in glycerol transport by hAQP10. Interestingly, a channel mechanism was also found to be involved in part in hAQP10-mediated glycerol transport. Conclusion: The present study unveiled the uniquely dual functional characteristic of hAQP10 as a carrier/channel for solute transport, providing a novel insight into its operation mechanism, which would help further elucidate its physiological role. Copyright (C) 2011 S. Karger AG, Basel
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