Differential expression of individual UT-A urea transporter isoforms in rat kidney.
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.
Bagnasco
Serena M
SM
Department of Pathology, Emory University School of Medicine, Atlanta, Georgia.
Peng
Tao
T
Department of Pathology, Emory University School of Medicine, Atlanta, Georgia.
Nakayama
Yushi
Y
Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.
Sands
Jeff M
JM
Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.
D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D001483:Base Sequence / Q000235:genetics; D001834:Body Water / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000096982:Urea Transporters
D020413:3' Untranslated Regions; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D020033:Protein Isoforms; D000096982:Urea Transporters