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Multiple urea transporter proteins in the kidney of holocephalan elephant fish (Callorhinchus milii)


Kakumura, K and Watanabe, S and Bell, JD and Donald, JA and Toop, T and Kaneko, T and Hyodo, S, Multiple urea transporter proteins in the kidney of holocephalan elephant fish (Callorhinchus milii), Comparative Biochemistry and Physiology - B Biochemistry and Molecular Biology, 154, (2) pp. 239-247. ISSN 1096-4959 (2009) [Refereed Article]

DOI: doi:10.1016/j.cbpb.2009.06.009


Reabsorption of filtered urea by the kidney is essential for retaining high levels of urea in marine cartilaginous fish. Our previous studies on the shark facilitative urea transporter (UT) suggest that additional UT(s) comprising the urea reabsorption system could exist in the cartilaginous fish kidney. Here, we isolated three cDNAs encoding UTs from the kidney of elephant fish, Callorhinchus milii, and termed them efUT-1, efUT-2 and efUT-3. efUT-1 is orthologous to known elasmobranch UTs, while efUT-2 and efUT-3 are novel UTs in cartilaginous fish. Two variants were found for efUT-1 and efUT-2, in which the NH 2-terminal intracellular domain was distinct between the variants. Differences in potential phosphorylation sites were found in the variant-specific NH 2-terminal domains. When expressed in Xenopus oocytes, all five UT transcripts including the efUT-1 and efUT-2 variants induced more than a 10-fold increase in [ 14C] urea uptake. Phloretin inhibited dose-dependently the increase of urea uptake, suggesting that the identified UTs are facilitative UTs. Molecular phylogenetic analysis revealed that efUT-1 and efUT-2 had diverged in the cartilaginous fish lineage, while efUT-3 is distinct from efUT-1 and efUT-2. The present finding of multiple UTs in elephant fish provides a key to understanding the molecular mechanisms of urea reabsorption system in the cartilaginous fish kidney. © 2009 Elsevier Inc. All rights reserved.

Item Details

Item Type:Refereed Article
Keywords:Cartilaginous fish; Elephant fish; Kidney; Molecular evolution; Reabsorption; Splicing variant; Urea transporter; Xenopus oocytes expression; carrier proteins and binding proteins; phloretin; unclassified drug; urea transporter 1; urea transporter 2
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Fisheries sciences
Research Field:Fish physiology and genetics
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the biological sciences
UTAS Author:Bell, JD (Dr Justin Bell)
ID Code:82509
Year Published:2009
Web of Science® Times Cited:14
Deposited By:Sustainable Marine Research Collaboration
Deposited On:2013-02-06
Last Modified:2013-06-06

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