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

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 Xe...

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Bibliographic Details
Published in:Molecular biology of the cell 2015-03, Vol.26 (6), p.1106-1118
Main Authors: Vilas, Gonzalo, Krishnan, Devishree, Loganathan, Sampath Kumar, Malhotra, Darpan, Liu, Lei, Beggs, Megan Rachele, Gena, Patrizia, Calamita, Giuseppe, Jung, Martin, Zimmermann, Richard, Tamma, Grazia, Casey, Joseph Roman, Alexander, Robert Todd
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Aquaporin 1 - metabolism
Carbonic Anhydrase II - metabolism
Cell Membrane Permeability
Cells, Cultured
Erythrocytes - metabolism
HEK293 Cells
Humans
Molecular Sequence Data
Protein Binding
Protein Interaction Mapping
Water - metabolism
Xenopus laevis
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Summary: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.
ISSN:1059-1524
1939-4586
DOI:10.1091/mbc.E14-03-0812