Characterization of mouse urea transporters UT-A1 and UT-A2.
Specialized transporter proteins that are the products of two closely related genes, UT-A (Slc14a2) and UT-B (Slc14a1), modulate the movement of urea across cell membranes. The purpose of this study was to characterize the mouse variants of two major products of the UT-A gene, UT-A1 and UT-A2. Screening a mouse kidney inner medulla cDNA library yielded 4,047- and 2,876-bp cDNAs, the mouse homologues of UT-A1 and UT-A2. Northern blot analysis showed high levels of UT-A mRNAs in kidney medulla. UT-A transcripts were also present in testes, heart, brain, and liver. Immunoblots with an antiserum raised to the 19 COOH-terminal amino acids of rat UT-A1 (L194) identified immunoreactive proteins in kidney, testes, heart, brain, and liver and showed a complex pattern of differential expression. Relative to other tissues, kidney and brain had the highest levels of UT-A protein expression. In kidney sections, immunostaining with L194 revealed immunoreactive proteins in type 1 (short) and type 3 (long) thin descending limbs of the loop of Henle and in the middle and terminal inner medullary collecting ducts. Expression in Xenopus laevis oocytes showed that, characteristic of UT-A family members, the cDNAs encoded phloretin-inhibitable urea transporters. Acute application of PKA agonists (cAMP/forskolin/IBMX) caused a significant increase in UT-A1- and UT-A3-, but not UT-A2-mediated, urea transport.
Fenton
R A
RA
School of Biological Sciences, University of Manchester, United Kingdom.
Stewart
G S
GS
Carpenter
B
B
Howorth
A
A
Potter
E A
EA
Cooper
G J
GJ
Smith
C P
CP
D000595:Amino Acid Sequence; D000818:Animals; D001693:Biological Transport, Active; D015152:Blotting, Northern; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D003001:Cloning, Molecular; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D007150:Immunohistochemistry; D007679:Kidney Medulla / Q000737:chemistry*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D026901:Membrane Transport Proteins; D051379:Mice; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014018:Tissue Distribution; D014508:Urea / Q000378:metabolism*; D014981:Xenopus; D000096982:Urea Transporters
D002352:Carrier Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D017931:DNA Primers; D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D014508:Urea; D000096982:Urea Transporters