Differential expression of individual UT-A urea transporter isoforms in rat kidney

• Published in: Journal of the American Society of Nephrology 2000-11, Vol.11 (11), p.1980-1986
• Main Authors: BAGNASCO, Serena M, TAO PENG, NAKAYAMA, Yushi, SANDS, Jeff M
• Format: Article
• Language: English
• Subjects: 3' Untranslated Regions - genetics; Animals; Base Sequence - genetics; Biological and medical sciences; Body Water - metabolism; Carrier Proteins - genetics; Carrier Proteins - metabolism; Fundamental and applied biological sciences. Psychology; Kidney - metabolism; Male; Membrane Glycoproteins - genetics; Membrane Glycoproteins - metabolism; Membrane Transport Proteins; Molecular Sequence Data; Protein Isoforms - genetics; Protein Isoforms - metabolism; Rats; Rats, Sprague-Dawley; Urea Transporters; Vertebrates: urinary system
• ISSN: 1046-6673; 1533-3450
• DOI: 10.1681/ASN.V11111980

The rat renal urea transporter UT-A includes four mRNA isoforms: UT-A1, UT-A2, UT-A3, and UT-A4. This study detected by rapid amplification of cDNA ends (RACE), primer extension, and ribonuclease protection assay (RPA) a single transcription start site for UT-A1, UT-A3, and UT-A4, distinct from the one for UT-A2 and identified by 3'-RACE new transcripts of UT-A1, UT-A2, and UT-A3, characterized by alternative 3' untranslated sequences (UTR). Expression of an alternative 3'UTR resulted in UT-A1 and UT-A2 transcripts that are approximately 400 bp shorter than the original cDNA. These mRNA isoforms (UT-A1b and UT-A2b) were present in low abundance in the inner medulla. Expression of an alternative 3'UTR for UT-A3 resulted in a 3.5 kb transcript (UT-A3b), which is 1.5 kb longer than the original UT-A3 cDNA. UT-A3b mRNA was easily detected by Northern hybridization in the inner medulla. This study examined whether different states of hydration induce homogeneous changes in mRNA expression of individual UT-A isoforms in the kidney. Analysis of UT-A1, UT-A1b, UT-A2, UT-A2b, UT-A3, and UT-A3b mRNA expression in rat kidney revealed that water deprivation markedly increases the relative abundance of UT-A2, UT-A2b, UT-A3, and UT-A3b mRNA in renal inner medulla, whereas UT-A1 and UT-A1b remain almost unchanged. The conclusion is that differential expression of individual UT-A mRNA isoforms occurs in the kidney and probably involves multiple regulatory mechanisms.