Cloning of a new aquaporin (AQP10) abundantly expressed in duodenum and jejunum

A new aquaporin (AQP10) was identified in human small intestine. This gene encoded a 264-amino-acid protein with high sequence identity with AQP3 (53% ), 9 (52%), and 7 (43%). These AQPs constitute one subfamily of AQP family that is differentiated from the other subfamily of AQP (AQP0, 1, 2, 4, 5, 6 , and 8) by sequence homology. Ribonuclease protection assay and Northern b lotting demonstrated almost exclusive expression of AQP10 mRNA in the duode num and jejunum. In situ hybridization localized it in absorptive jejunal e pithelial cells. Xenopus oocytes expressing AQP10 exhibited an increased os motic water permeability in a mercury-sensitive manner. Although AQP10 belo ngs to the AQP subfamily, which has been characterized by permeability to w ater and neutral solutes such as urea and glycerol, it was not permeable to urea nor glycerol. The specific expression of AQP10 suggests its contribut ion to the water transport in the upper portion of small intestine. (C) 200 1 Academic Press.