Molecular characterization of a novel UT-A urea transporter isoform (UT-A5) in testis.
Urea movement across plasma membranes is modulated by specialized transporter proteins that are products of two genes, termed UT-A and UT-B. These proteins play key roles in the urinary concentrating mechanism and fluid homeostasis. We have isolated and characterized a 1.4-kb cDNA from testes encoding a new isoform (UT-A5) belonging to the UT-A transporter family. For comparison, we also isolated a 2. 0-kb cDNA from mouse kidney inner medulla encoding the mouse UT-A3 homologue. The UT-A5 cDNA has a putative open reading frame encoding a 323-amino acid protein, making UT-A5 the smallest UT-A family member in terms of molecular size. Its putative topology is of particular interest, because it calls into question earlier models of UT-A transporter structure. Expression of UT-A5 cRNA in Xenopus oocytes mediates phloretin-inhibitable urea uptake and does not translocate water. The distribution of UT-A5 mRNA is restricted to the peritubular myoid cells forming the outermost layer of the seminiferous tubules within the testes and is not detected in kidney. UT-A5 mRNA levels are coordinated with the stage of testes development and increase 15 days postpartum, commensurate with the start of seminiferous tubule fluid movement.
Fenton
R A
RA
School of Biological Science, University of Manchester, Manchester M13 9PT, United Kingdom.
Howorth
A
A
Cooper
G J
GJ
Meccariello
R
R
Morris
I D
ID
Smith
C P
CP
D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence / Q000235:genetics; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000378:metabolism / Q000494:pharmacology; D018076:DNA, Complementary / Q000235:genetics; D005784:Gene Amplification; D007679:Kidney Medulla / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000494:pharmacology; D026901:Membrane Transport Proteins; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D010539:Permeability; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid; D013737:Testis / Q000378:metabolism*; D014018:Tissue Distribution; D014867:Water / Q000378:metabolism; D000096982:Urea Transporters
D002352:Carrier Proteins; D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D014867:Water; D000096982:Urea Transporters