Noncanonical binding of calmodulin to aquaporin-0: implications for channel regulation.
Aquaporins (AQPs) are a family of ubiquitous membrane channels that conduct water across cell membranes. AQPs form homotetramers containing four functional and independent water pores. Aquaporin-0 (AQP0) is expressed in the eye lens, where its water permeability is regulated by calmodulin (CaM). Here we use a combination of biochemical methods and NMR spectroscopy to probe the interaction between AQP0 and CaM. We show that CaM binds the AQP0 C-terminal domain in a calcium-dependent manner. We demonstrate that only two CaM molecules bind a single AQP0 tetramer in a noncanonical fashion, suggesting a form of cooperativity between AQP0 monomers. Based on these results, we derive a structural model of the AQP0/CaM complex, which suggests CaM may be inhibitory to channel permeability by capping the vestibules of two monomers within the AQP0 tetramer. Finally, phosphorylation within AQP0's CaM binding domain inhibits the AQP0/CaM interaction, suggesting a temporal regulatory mechanism for complex formation.
Reichow
Steve L
SL
Department of Biochemistry, University of Washington, Box 357350, Seattle, WA 98195-7350, USA.
Gonen
Tamir
T
D000595:Amino Acid Sequence; D000818:Animals; D020346:Aquaporins / Q000737:chemistry / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000737:chemistry / Q000378:metabolism*; D003459:Crystallins / Q000378:metabolism; D005136:Eye Proteins / Q000737:chemistry / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism* / Q000502:physiology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D012756:Sheep
D020346:Aquaporins; D002147:Calmodulin; D003459:Crystallins; D005136:Eye Proteins; D007473:Ion Channels; C030328:aquaporin 0; D017346:Protein Serine-Threonine Kinases; D002118:Calcium
J Biol Chem. 2004 Apr 23;279(17):17027-37
14752100
PLoS Biol. 2003 Dec;1(3):E72
14691544
J Biol Chem. 2007 Nov 30;282(48):35005-17
17901047
J Mol Biol. 1988 Nov 5;204(1):191-204
3145979
Science. 2002 Apr 19;296(5567):525-30
11964478
Invest Ophthalmol Vis Sci. 1989 May;30(5):975-89
2722452
Proc Natl Acad Sci U S A. 2004 Sep 28;101(39):14045-50
15377788
FASEB J. 1997 Apr;11(5):331-40
9141499
J Mol Biol. 2003 Apr 18;328(1):193-204
12684008
Science. 2000 Oct 20;290(5491):481-6
11039922
Nature. 2004 May 13;429(6988):193-7
15141214
Biochim Biophys Acta. 2001 Apr 30;1536(1):64-72
11335105
Nature. 1999 May 13;399(6732):159-62
10335846
J Gen Physiol. 2004 May;123(5):573-80
15078916
Cardiovasc Res. 2007 Mar 1;73(4):641-7
17137569
J Mol Biol. 2004 Sep 24;342(4):1337-45
15351655
J Comput Chem. 2004 Oct;25(13):1605-12
15264254
Q Rev Biophys. 2006 Nov;39(4):361-96
17156589
FEBS Lett. 2003 Nov 27;555(1):72-8
14630322
J Biol Chem. 1994 Apr 8;269(14):10417-22
7511600
J Biol Chem. 1997 Oct 31;272(44):27525-8
9346883
Nature. 2001 Dec 20-27;414(6866):872-8
11780053
Invest Ophthalmol Vis Sci. 2003 Nov;44(11):4820-8
14578404
Proc Natl Acad Sci U S A. 2005 Dec 27;102(52):18932-7
16361443
Mol Biotechnol. 2004 May;27(1):33-57
15122046
Nature. 2000 Oct 5;407(6804):599-605
11034202
Biochemistry. 1985 Dec 31;24(27):8152-7
3841496
Am J Physiol. 1993 Sep;265(3 Pt 2):F461
7692747
Exp Eye Res. 2004 Dec;79(6):761-8
15642313
Biochemistry. 1990 May 15;29(19):4659-67
2372549
Mol Vis. 2007 Sep 11;13:1651-6
17893667
Exp Eye Res. 1975 Dec;21(6):581-95
1204686
J Biol Chem. 1997 Jun 27;272(26):16140-6
9195910
J Biomol NMR. 1995 Nov;6(3):277-93
8520220
Biochem J. 1983 May 1;211(2):473-9
6870843
J Cell Biol. 1982 Jan;92(1):213-20
7035467
Invest Ophthalmol Vis Sci. 2005 Apr;46(4):1393-402
15790907
Curr Opin Struct Biol. 2006 Aug;16(4):447-56
16837191
Invest Ophthalmol Vis Sci. 2000 Jan;41(1):199-203
10634621
J Mol Biol. 2006 Jan 27;355(4):628-39
16325200
Biochemistry. 2004 Aug 3;43(30):9856-65
15274640
Cell Differ. 1972 Jun;1(2):91-106
4275925
Br J Ophthalmol. 2000 Dec;84(12):1376-9
11090476
Proc Natl Acad Sci U S A. 2001 Feb 13;98(4):1398-403
11171962
J Biol Chem. 2000 Mar 10;275(10):6777-82
10702234
Biochem Cell Biol. 1994 Sep-Oct;72(9-10):357-76
7605608
Nature. 2005 Dec 1;438(7068):633-8
16319884
J Intern Med. 2007 Jan;261(1):53-64
17222168
Biochemistry. 2008 Jan 8;47(1):339-47
18081321
Eur J Biochem. 1995 Dec 1;234(2):670-9
8536718
Nature. 2006 Feb 9;439(7077):688-94
16340961
Curr Eye Res. 1985 Apr;4(4):431-9
2410193
Shi Yan Sheng Wu Xue Bao. 2001 Jun;34(2):131-5
12549106
Curr Eye Res. 1991 Sep;10(9):839-49
1790714
Chem Biol. 2005 Sep;12(9):961-71
16183020