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.
Department of Pathology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Hideki
H
Inoue
Shelley D
SD
Jackson
Tatyana
T
Vikulina
Janet D
JD
Klein
Kimio
K
Tomita
Serena M
SM
Bagnasco
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