Identification and characterization of a Kidd antigen/UT-B urea transporter expressed in human colon.
We have identified a urea transporter from the mucosa of the human colon that has characteristics consistent with a Kidd antigen/UT-B urea transporter. This intestinal urea transporter encodes a 389-amino acid peptide with a sequence identical to that previously reported for the UT-B urea transporter in erythrocytes. Expression of a UT-B 2-kb mRNA transcript and of approximately 50- and approximately 98-kDa UT-B proteins is detected in human colonic mucosa by Northern and Western blot analysis. The UT-B protein is localized in the cell membrane and cytoplasm of the superficial intestinal epithelium and in the epithelial cells in the crypts. A 2-kb UT-B mRNA transcript and the UT-B protein were also identified in the intestinal cell line Caco-2. The transepithelial flux of (14)C urea was examined in Caco-2 cells growing on porous membrane support and was significantly inhibited by phloretin, 1,3-dimethylurea, and thiourea, suggesting that the transfer of urea across the Caco-2 monolayer could be mediated, at least in part, by the UT-B urea transporter. We conclude that the Kidd antigen/UT-B urea transporter is physiologically expressed in the human colon epithelium, where it could participate in the transport of urea across the colon mucosa.
Inoue
Hideki
H
Department of Pathology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Jackson
Shelley D
SD
Vikulina
Tatyana
T
Klein
Janet D
JD
Tomita
Kimio
K
Bagnasco
Serena M
SM
D000595:Amino Acid Sequence; D001789:Blood Group Antigens / Q000235:genetics / Q000378:metabolism*; D015152:Blotting, Northern; D015153:Blotting, Western; D018938:Caco-2 Cells; D003106:Colon / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000378:metabolism; D007667:Kidd Blood-Group System / Q000276:immunology*; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D000096982:Urea Transporters
D001789:Blood Group Antigens; D018076:DNA, Complementary; D007667:Kidd Blood-Group System; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D000096982:Urea Transporters