title: Differential protein abundance and function of UT-B urea transporters in human colon.
abstract: Facilitative UT-B urea transporters enable the passage of urea across cell membranes. Gastrointestinal urea transporters are thought to play a significant role in the urea nitrogen salvaging process that occurs between mammalian hosts and their gut bacteria. This study investigated the expression of UT-B urea transporters in different segments of human colon. Immunoblot analysis showed that human colon expressed a 35-kDa glycosylated UT-B protein in the colonic mucosa. The 35-kDa UT-B transporter was predominantly located in plasma membrane-enriched samples (P < 0.001; n = 6), and its expression was greater in the ascending colon compared with the descending colon (P < 0.01; n = 3). At the cellular level, UT-B transporters were located throughout colonocytes situated in the upper portion of the colonic crypts. Bidirectional trans-epithelial urea transport was significantly greater in the ascending colon than the descending colon (P < 0.05; n = 6). In addition, the facilitative urea transporter inhibitor 1,3,dimethylurea significantly reduced urea transport in the ascending colon (P < 0.05; n = 6) but had no effect in the descending colon (NS; n = 6). These results illustrate differential protein abundance of functional UT-B protein in different sections of the human colon, strongly correlating to regions that contain the largest populations of intestinal bacteria. This study suggests an important role for UT-B urea transporters in maintaining the symbiotic relationship between humans and their gut bacteria.
authors.affiliation: Center for Pain Research, Department of Anesthesiology, University of Pittsburgh, Pennsylvania, USA. daniellecol@gmail.com
authors.forename: D
authors.initials: D
authors.lastname: Collins
authors.forename: D C
authors.initials: DC
authors.lastname: Winter
authors.forename: A M
authors.initials: AM
authors.lastname: Hogan
authors.forename: L
authors.initials: L
authors.lastname: Schirmer
authors.forename: A W
authors.initials: AW
authors.lastname: Baird
authors.forename: G S
authors.initials: GS
authors.lastname: Stewart
mesh_terms: D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D003106:Colon / Q000187:drug effects / Q000502:physiology*; D044682:Colon, Ascending / Q000187:drug effects / Q000502:physiology; D044683:Colon, Descending / Q000187:drug effects / Q000502:physiology; D003593:Cytoplasm / Q000378:metabolism; D017097:Electric Impedance; D055724:Electrophysiological Phenomena / Q000502:physiology; D004847:Epithelial Cells / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000187:drug effects / Q000502:physiology*; D008782:Methylurea Compounds / Q000494:pharmacology; D009130:Muscle, Smooth / Q000378:metabolism; D014508:Urea / Q000031:analogs & derivatives / Q000378:metabolism; D000096982:Urea Transporters
chemical_list: D002217:Carbachol; D026901:Membrane Transport Proteins; D008782:Methylurea Compounds; D014508:Urea; D000096982:Urea Transporters; C018276:1,3-dimethylurea