Novel bUT-B2 urea transporter isoform is constitutively activated.
Our previous studies have detailed a novel facilitative UT-B urea transporter isoform, bUT-B2. Despite the existence of mouse and human orthologs, the functional characteristics of UT-B2 remain undefined. In this report, we produced a stable MDCK cell line that expressed bUT-B2 protein and investigated the transepithelial urea flux across cultured cell monolayers. We observed a large basal urea flux that was significantly reduced by known inhibitors of facilitative urea transporters; 1,3 dimethylurea (P < 0.001, n = 17), thionicotinamide (P < 0.05, n = 11), and phloretin (P < 0.05, n = 9). Pre-exposure for 1 h to the antidiuretic hormone vasopressin had no effect on bUT-B2-mediated urea transport (NS, n = 3). Acute vasopressin exposure for up to 30 min also failed to elicit any transient response (NS, n = 9). Further investigation confirmed that bUT-B2 function was not affected by alteration of intracellular cAMP (NS, n = 4), intracellular calcium (NS, n = 3), or protein kinase activity (NS, n = 4). Finally, immunoblot data suggested a possible role for glycosylation in regulating bUT-B2 function. In conclusion, this study showed that bUT-B2-mediated transepithelial urea transport was constitutively activated and unaffected by known regulators of renal UT-A urea transporters.
Tickle
P
P
Faculty of Life Sciences, The University of Manchester, Manchester, UK.
Thistlethwaite
A
A
Smith
C P
CP
Stewart
G S
GS
D000818:Animals; D000906:Antibodies / Q000276:immunology; D000918:Antibody Specificity / Q000276:immunology; D001127:Arginine Vasopressin / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002417:Cattle; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004285:Dogs; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008782:Methylurea Compounds / Q000494:pharmacology; D009536:Niacinamide / Q000031:analogs & derivatives / Q000494:pharmacology; D010693:Phloretin / Q000494:pharmacology; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014508:Urea / Q000031:analogs & derivatives / Q000378:metabolism; D000096982:Urea Transporters
D000906:Antibodies; D001127:Arginine Vasopressin; D026901:Membrane Transport Proteins; D008782:Methylurea Compounds; D009536:Niacinamide; D010693:Phloretin; D020033:Protein Isoforms; D013755:Tetradecanoylphorbol Acetate; D014508:Urea; D000096982:Urea Transporters; C070820:thionicotinamide; C018276:1,3-dimethylurea