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

Kakumura, Keigo, Watanabe, Soichi, Bell, Justin D., Donald, John A., Toop, Tes, Kaneko, Toyoji and Hyodo, Susumu 2009, Multiple urea transporter proteins in the kidney of holocephalan elephant fish (Callorhinchus milii), Comparative biochemistry and physiology. B, Biochemistry & molecular biology, vol. 154, no. 2, pp. 239-247, doi: 10.1016/j.cbpb.2009.06.009.

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Title Multiple urea transporter proteins in the kidney of holocephalan elephant fish (Callorhinchus milii)
Formatted title Multiple urea transporter proteins in the kidney of holocephalan elephant fish (Callorhinchus milii)
Author(s) Kakumura, Keigo
Watanabe, Soichi
Bell, Justin D.
Donald, John A.ORCID iD for Donald, John A.
Toop, Tes
Kaneko, Toyoji
Hyodo, Susumu
Journal name Comparative biochemistry and physiology. B, Biochemistry & molecular biology
Volume number 154
Issue number 2
Start page 239
End page 247
Total pages 9
Publisher Elsevier Inc.
Place of publication Amsterdam, The Netherlands
Publication date 2009-10
ISSN 1096-4959
Keyword(s) urea transporter
cartilaginous fish
elephant fish
xenopus oocytes expression
molecular evolution
splicing variant
Summary 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 NH2-terminal intracellular domain was distinct between the variants. Differences in potential phosphorylation sites were found in the variant-specific NH2-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.
Language eng
DOI 10.1016/j.cbpb.2009.06.009
Field of Research 110106 Medical Biochemistry: Proteins and Peptides (incl Medical Proteomics)
060601 Animal Physiology - Biophysics
HERDC Research category C1 Refereed article in a scholarly journal
Copyright notice ©2009, Elsevier Inc.
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Document type: Journal Article
Collection: School of Life and Environmental Sciences
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