title: Expression and functional characterization of four aquaporin water channels from the European eel (Anguilla anguilla).
abstract: The European eel is a euryhaline teleost which has been shown to differentially up- and downregulate aquaporin (AQP) water channels in response to changes in environmental salinity. We have characterized the transport properties of four aquaporins localized to osmoregulatory organs - gill, esophagus, intestine and kidney. By sequence comparison these four AQP orthologs resemble human AQP1 (eel AQP1), AQP3 (eel AQP3) and AQP10 (AQPe). The fourth member is a duplicate form of AQP1 (AQP1dup) thought to arise from a duplication of the teleost genome. Using heterologous expression in Xenopus oocytes we demonstrate that all four eel orthologs transport water and are mercury inhibitable. Eel AQP3 and AQPe also transport urea and glycerol, making them aquaglyceroporins. Eel AQP3 is dramatically inhibited by extracellular acidity (91% and 69% inhibition of water and glycerol transport respectively at pH 6.5) consistent with channel gating by protons. Maximal water flux of eel AQP3 occurred around pH 8.2 - close to the physiological pH of plasma in the eel. Exposure of AQP-expressing oocytes to heavy metals revealed that eel AQP3 is highly sensitive to extracellular nickel and zinc (88.3% and 86.3% inhibition, respectively) but less sensitive to copper (56.4% inhibition). Surprisingly, copper had a stimulatory effect on eel AQP1 (153.7% activity of control). Copper, nickel and zinc did not affect AQP1dup or AQPe. We establish that all four eel AQP orthologs have similar transport profiles to their human counterparts, with eel AQP3 exhibiting some differences in its sensitivity to metals. This is the first investigation of the transport properties and inhibitor sensitivity of salinity-regulated aquaporins from a euryhaline species. Our results indicate a need to further investigate the deleterious effects of metal pollutants on AQP-containing epithelial cells of the gill and gastrointestinal tract at environmentally appropriate concentrations.
authors.affiliation: Nephrology Division, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Bryce
authors.initials: B
authors.lastname: MacIver
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Cutler
authors.forename: Jia
authors.initials: J
authors.lastname: Yin
authors.forename: Myles G
authors.initials: MG
authors.lastname: Hill
authors.forename: Mark L
authors.initials: ML
authors.lastname: Zeidel
authors.forename: Warren G
authors.initials: WG
authors.lastname: Hill
mesh_terms: D000811:Anguilla / Q000378:metabolism*; D000818:Animals; D020346:Aquaporins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D001692:Biological Transport / Q000187:drug effects; D003300:Copper / Q000494:pharmacology; D029941:Fish Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D009532:Nickel / Q000494:pharmacology; D014867:Water / Q000378:metabolism; D014981:Xenopus; D015032:Zinc / Q000494:pharmacology
chemical_list: D020346:Aquaporins; D029941:Fish Proteins; D014867:Water; D003300:Copper; D009532:Nickel; D015032:Zinc
references.citation: J Mol Evol. 2001 May;52(5):391-404
references.pmid: 11443343
references.citation: Annu Rev Plant Biol. 2008;59:595-624
references.pmid: 18444909
references.citation: Proc Natl Acad Sci U S A. 2005 Dec 27;102(52):18932-7
references.pmid: 16361443
references.citation: J Biol Chem. 2003 Mar 21;278(12):10649-56
references.pmid: 12519768
references.citation: Environ Health Perspect. 1987 Apr;71:47-58
references.pmid: 3297663
references.citation: Comp Biochem Physiol A Comp Physiol. 1974 Apr 1;47(4):1241-4
references.pmid: 4156279
references.citation: J Biol Chem. 1999 Jul 30;274(31):21631-6
references.pmid: 10419471
references.citation: Gen Comp Endocrinol. 2003 Jun 1;132(1):112-8
references.pmid: 12765650
references.citation: J Exp Biol. 2002 Sep;205(Pt 17):2643-51
references.pmid: 12151370
references.citation: J Biol Chem. 2003 Aug 8;278(32):30037-43
references.pmid: 12773542
references.citation: Microbiology (Reading). 2001 May;147(Pt 5):1129-1135
references.pmid: 11320116
references.citation: J Exp Biol. 1994 Sep;194(1):299-317
references.pmid: 9317846
references.citation: Gen Comp Endocrinol. 2007 Jun-Jul;152(2-3):310-3
references.pmid: 17353012
references.citation: Mol Microbiol. 2000 Jul;37(2):254-62
references.pmid: 10931322
references.citation: Comp Biochem Physiol A Mol Integr Physiol. 2007 Sep;148(1):82-91
references.pmid: 17126580
references.citation: J Exp Biol. 2008 Aug;211(Pt 15):2542-50
references.pmid: 18626090
references.citation: J Comp Physiol B. 2003 Aug;173(6):463-74
references.pmid: 12851779
references.citation: Am J Physiol Regul Integr Comp Physiol. 2005 Jun;288(6):R1733-43
references.pmid: 15650119
references.citation: Aquat Toxicol. 2005 Mar 25;72(1-2):119-33
references.pmid: 15748751
references.citation: Chem Biol Interact. 2008 Aug 11;174(3):183-92
references.pmid: 18586230
references.citation: Nat Rev Mol Cell Biol. 2004 Sep;5(9):687-98
references.pmid: 15340377
references.citation: Aquat Toxicol. 2007 Nov 30;85(2):143-53
references.pmid: 17904660
references.citation: J Exp Biol. 2002 Sep;205(Pt 17):2653-63
references.pmid: 12151371
references.citation: J Mol Biol. 2007 May 4;368(3):607-17
references.pmid: 17376483
references.citation: J Exp Biol. 1998 Jun;201(Pt 11):1809-15
references.pmid: 9576891
references.citation: Aquat Toxicol. 2004 Jun 24;68(3):263-75
references.pmid: 15159052
references.citation: Comp Biochem Physiol B Biochem Mol Biol. 2003 Dec;136(4):621-33
references.pmid: 14662289
references.citation: Biochemistry. 1997 Nov 18;36(46):13973-8
references.pmid: 9369468
references.citation: J Biol Chem. 1997 Jun 27;272(26):16140-6
references.pmid: 9195910
references.citation: J Exp Biol. 2008 Aug;211(Pt 15):2533-41
references.pmid: 18626089
references.citation: Ann Clin Lab Sci. 1988 Nov-Dec;18(6):444-50
references.pmid: 2467601
references.citation: Biol Cell. 2005 Aug;97(8):615-27
references.pmid: 15850452
references.citation: Comp Biochem Physiol C Toxicol Pharmacol. 2002 Sep;133(1-2):287-303
references.pmid: 12356534
references.citation: J Cell Sci. 2005 Aug 1;118(Pt 15):3225-32
references.pmid: 16079275
references.citation: Aquat Toxicol. 2006 Nov 16;80(2):131-9
references.pmid: 16996624
references.citation: Aquat Toxicol. 2007 Aug 30;84(2):162-72
references.pmid: 17643507
references.citation: Comp Biochem Physiol A Mol Integr Physiol. 2007 Nov;148(3):479-97
references.pmid: 17689996
references.citation: Comp Biochem Physiol C Toxicol Pharmacol. 2006 May;143(1):94-102
references.pmid: 16458611
references.citation: Am J Physiol Renal Physiol. 2004 May;286(5):F811-27
references.pmid: 15075177
references.citation: J Cell Physiol. 1995 Sep;164(3):613-9
references.pmid: 7544358
references.citation: J Biol Chem. 2004 Dec 10;279(50):51939-43
references.pmid: 15456785
references.citation: Physiol Rev. 2005 Jan;85(1):97-177
references.pmid: 15618479
references.citation: Aquat Toxicol. 2006 Oct 25;80(1):70-81
references.pmid: 16968655
references.citation: Am J Physiol. 1997 Sep;273(3 Pt 2):F451-6
references.pmid: 9321919