Aquaporin-11: A channel protein lacking apparent transport function expressed in brain
Daniel A Gorelick1 ,4, Jeppe Praetorius2, Takashi Tsunenari3, Søren Nielsen2 and Peter Agre1
1Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, USA
2The Water and Salt Research Center, Institute of Anatomy, University of Aarhus, Aarhus, Denmark
3Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, USA
4Department of Embryology, Carnegie Institution of Washington, 3520 San Martin Drive, Baltimore, MD 21218, USA
The aquaporins are a family of integral membrane proteins composed of two subfamilies: the orthodox aquaporins, which transport only water, and the aquaglyceroporins, which transport glycerol, urea, or other small solutes. Two recently described aquaporins, numbers 11 and 12, appear to be more distantly related to the other mammalian aquaporins and aquaglyceroporins.
We report on the characterization of Aquaporin-11 (AQP11). AQP11 RNA and protein is found in multiple rat tissues, including kidney, liver, testes and brain. AQP11 has a unique distribution in brain, appearing in Purkinje cell dendrites, hippocampal neurons of CA1 and CA2, and cerebral cortical neurons. Immunofluorescent staining of Purkinje cells indicates that AQP11 is intracellular. Unlike other aquaporins, Xenopus oocytes expressing AQP11 in the plasma membrane failed to transport water, glycerol, urea, or ions.
AQP11 is functionally distinct from other proteins of the aquaporin superfamily and could represent a new aquaporin subfamily. Further studies are necessary to elucidate the role of AQP11 in the brain.
Source: BMC Biochemistry 2006, 7:14.
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