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Mol Biol Cell. 2015 Mar 15;26(6):1106-18. doi: 10.1091/mbc.E14-03-0812. Epub 2015 Jan 21.

Increased water flux induced by an aquaporin-1/carbonic anhydrase II interaction.

Author information

1
Department of Biochemistry, University of Alberta, Edmonton, AB T6G 1C9, Canada.
2
Department of Physiology, University of Alberta, Edmonton, AB T6G 1C9, Canada Membrane Protein Disease Research Group, University of Alberta, Edmonton, AB T6G 1C9, Canada.
3
Department of Biochemistry, University of Alberta, Edmonton, AB T6G 1C9, Canada Membrane Protein Disease Research Group, University of Alberta, Edmonton, AB T6G 1C9, Canada.
4
Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, 70121 Bari, Italy.
5
Department of Medical Biochemistry and Molecular Biology, Saarland University, D-66424 Homburg, Germany.
6
Department of Biochemistry, University of Alberta, Edmonton, AB T6G 1C9, Canada Department of Physiology, University of Alberta, Edmonton, AB T6G 1C9, Canada Membrane Protein Disease Research Group, University of Alberta, Edmonton, AB T6G 1C9, Canada.
7
Department of Physiology, University of Alberta, Edmonton, AB T6G 1C9, Canada Membrane Protein Disease Research Group, University of Alberta, Edmonton, AB T6G 1C9, Canada Department of Pediatrics, University of Alberta, Edmonton, AB T6G 1C9, Canada todd2@ualberta.ca.

Abstract

Aquaporin-1 (AQP1) enables greatly enhanced water flux across plasma membranes. The cytosolic carboxy terminus of AQP1 has two acidic motifs homologous to known carbonic anhydrase II (CAII) binding sequences. CAII colocalizes with AQP1 in the renal proximal tubule. Expression of AQP1 with CAII in Xenopus oocytes or mammalian cells increased water flux relative to AQP1 expression alone. This required the amino-terminal sequence of CAII, a region that binds other transport proteins. Expression of catalytically inactive CAII failed to increase water flux through AQP1. Proximity ligation assays revealed close association of CAII and AQP1, an effect requiring the second acidic cluster of AQP1. This motif was also necessary for CAII to increase AQP1-mediated water flux. Red blood cell ghosts resealed with CAII demonstrated increased osmotic water permeability compared with ghosts resealed with albumin. Water flux across renal cortical membrane vesicles, measured by stopped-flow light scattering, was reduced in CAII-deficient mice compared with wild-type mice. These data are consistent with CAII increasing water conductance through AQP1 by a physical interaction between the two proteins.

PMID:
25609088
PMCID:
PMC4357510
DOI:
10.1091/mbc.E14-03-0812
[Indexed for MEDLINE]
Free PMC Article

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