Proceedings of The Physiological Society
University College London (2011) Proc Physiol Soc 24, PC21
Investigation of UT-B urea transporter isoforms in the human gastrointestinal tract
C. Walpole1, O. O'Coigligh1, C. M. Nolan1, G. Stewart1
1. Biology & Environmental Science, University College Dublin, Dublin, Ireland.
The symbiotic relationship that exists between humans and their intestinal bacteria is crucial in maintaining our gastrointestinal health. UT-B urea transporters facilitate the entry of urea into the lumen of the gastrointestinal tract and hence play a significant role in the urea nitrogen salvaging mechanism believed to support bacterial growth. Previously, using an antibody raised against bovine UT-B1, we detected UT-B proteins in human colonic mucosa in the form of 30kDa unglycosylated and 35kDa glycosylated signals. In contrast, a study by Inoue et al. utilising a different antibody detected a glycosylated 50kDa UT-B protein (2), suggesting there may be more than one isoform present in the human colon. To determine whether different UT-B isoforms are present in the human gastrointestinal tract, we produced and characterised a new UT-B antibody that was raised against the C-terminal of human UT-B1. Using western blotting techniques, we detected multiple protein signals of different sizes - namely 34, 38, 43 and 55kDa. These proteins were present in stomach, small intestine and colonic tissue (obtained from surgical resection procedures, with consent), as well as the Caco-2 intestinal cell line. Although pre-incubation with immunizing peptide completely prevented these signals, surprisingly none of them represented glycosylated proteins. Preliminary RT-PCR investigation of human colonic cDNA confirmed the presence of more than one human UT-B transcript (e.g. both UT-B1 and UT-B2 detected). Together, these data suggest the existence of multiple UT-B isoforms throughout the human gastrointestinal tract. Further studies are now required to determine the precise nature, cellular localization and function of these different gastrointestinal human UT-B urea transporters.
Where applicable, experiments conform with Society ethical requirements