title: Structures of human CCL18, CCL3, and CCL4 reveal molecular determinants for quaternary structures and sensitivity to insulin-degrading enzyme.
abstract: CC chemokine ligands (CCLs) are 8- to 14-kDa signaling proteins involved in diverse immune functions. While CCLs share similar tertiary structures, oligomerization produces highly diverse quaternary structures that protect chemokines from proteolytic degradation and modulate their functions. CCL18 is closely related to CCL3 and CCL4 with respect to both protein sequence and genomic location, yet CCL18 has distinct biochemical and biophysical properties. Here, we report a crystal structure of human CCL18 and its oligomerization states in solution based on crystallographic and small-angle X-ray scattering analyses. Our data show that CCL18 adopts an α-helical conformation at its N-terminus that weakens its dimerization, explaining CCL18's preference for the monomeric state. Multiple contacts between monomers allow CCL18 to reversibly form a unique open-ended oligomer different from those of CCL3, CCL4, and CCL5. Furthermore, these differences hinge on proline 8, which is conserved in CCL3 and CCL4 but is replaced by lysine in human CCL18. Our structural analyses suggest that a mutation of proline 8 to alanine stabilizes a type 1 β-turn at the N-terminus of CCL4 to prevent dimerization but prevents dimers from making key contacts with each other in CCL3. Thus, the P8A mutation induces depolymerization of CCL3 and CCL4 by distinct mechanisms. Finally, we used structural, biochemical, and functional analyses to unravel why insulin-degrading enzyme degrades CCL3 and CCL4 but not CCL18. Our results elucidate the molecular basis for the oligomerization of three closely related CC chemokines and suggest how oligomerization shapes CCL chemokine function.
authors: Ben May Department for Cancer Research, The University of Chicago, IL 60637, USA.
authors: Wenguang G
authors: WG
authors: Liang
authors: Ben May Department for Cancer Research, The University of Chicago, IL 60637, USA.
authors: Min
authors: M
authors: Ren
authors: Ben May Department for Cancer Research, The University of Chicago, IL 60637, USA.
authors: Fan
authors: F
authors: Zhao
authors: Ben May Department for Cancer Research, The University of Chicago, IL 60637, USA. Electronic address: wtang@uchicago.edu.
authors: Wei-Jen
authors: WJ
authors: Tang
mesh_terms: D000595:Amino Acid Sequence; D054405:Chemokine CCL3 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D054407:Chemokine CCL4 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019742:Chemokines, CC / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002633:Chemotaxis; D018360:Crystallography, X-Ray; D006801:Humans; D007339:Insulysin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D020836:Protein Structure, Quaternary; D053838:Scattering, Small Angle; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: C111792:CCL18 protein, human; C515429:CCL3 protein, human; C066507:CCL4 protein, human; D054405:Chemokine CCL3; D054407:Chemokine CCL4; D019742:Chemokines, CC; D007339:Insulysin
keywords: M16 metalloprotease; SAXS; chemokine; crystallography
references: Proteomics. 2009 Mar;9(6):1548-55
references: 19235167
references: J Biol Chem. 2013 Apr 5;288(14):10024-34
references: 23408426
references: J Immunol. 1997 Aug 1;159(3):1140-9
references: 9233607
references: Pharmacol Rev. 2014;66(1):1-79
references: 24218476
references: Science. 2009 Aug 21;325(5943):960-3
references: 19696342
references: J Exp Med. 2013 Sep 23;210(10):1889-98
references: 23999500
references: Nature. 1998 Feb 26;391(6670):908-11
references: 9495345
references: Annu Rev Immunol. 2007;25:787-820
references: 17291188
references: J Appl Crystallogr. 2007 Aug 1;40(Pt 4):658-674
references: 19461840
references: Acta Crystallogr D Biol Crystallogr. 2010 Jan;66(Pt 1):12-21
references: 20057044
references: J Leukoc Biol. 2008 Oct;84(4):1101-8
references: 18662971
references: Anal Biochem. 2006 Oct 15;357(2):289-98
references: 16962548
references: Eur J Med Chem. 2014 May 22;79:184-93
references: 24735644
references: Cell. 2002 Nov 1;111(3):343-56
references: 12419245
references: Acta Crystallogr D Biol Crystallogr. 2012 Jun;68(Pt 6):620-6
references: 22683784
references: Blood. 2003 Sep 15;102(6):1985-8
references: 12763925
references: Acta Crystallogr D Biol Crystallogr. 2002 Nov;58(Pt 11):1955-7
references: 12393928
references: Mol Immunol. 2012 Jun;51(2):227-33
references: 22487721
references: J Biol Chem. 1998 Dec 11;273(50):33157-65
references: 9837883
references: J Leukoc Biol. 2005 Jul;78(1):14-26
references: 15784687
references: Proc Natl Acad Sci U S A. 2013 Aug 20;110(34):13827-32
references: 23922390
references: PLoS One. 2010;5(5):e10504
references: 20498699
references: Proc Natl Acad Sci U S A. 2003 Feb 18;100(4):1885-90
references: 12571364
references: J Leukoc Biol. 2001 Oct;70(4):610-6
references: 11590198
references: EMBO J. 2010 Dec 1;29(23):3952-66
references: 20959807
references: Cytokine Growth Factor Rev. 2002 Dec;13(6):455-81
references: 12401480
references: Exp Cell Res. 2011 Mar 10;317(5):590-601
references: 21223963
references: J Mol Biol. 2010 Jan 15;395(2):430-43
references: 19896952
references: J Biol Chem. 2003 Feb 14;278(7):5179-87
references: 12466283
references: Exp Cell Res. 2011 Mar 10;317(5):642-54
references: 21146523
references: Nature. 1997 Jun 12;387(6634):713-7
references: 9192897
references: Science. 1994 Mar 25;263(5154):1762-7
references: 8134838
references: Eur J Med Chem. 2015 Jan 27;90:547-67
references: 25489670
references: Am J Respir Crit Care Med. 2006 Apr 1;173(7):781-92
references: 16415274
references: Methods. 2011 Sep;55(1):94-106
references: 21821126
references: Annu Rev Biochem. 2006;75:333-66
references: 16756495
references: J Immunol. 1998 Feb 1;160(3):1411-8
references: 9570561
references: Nature. 2006 Oct 19;443(7113):870-4
references: 17051221
references: Biochemistry. 2008 Dec 2;47(48):12822-34
references: 18986166
references: Blood. 2004 Jan 1;103(1):33-9
references: 12969956
references: Structure. 2011 Aug 10;19(8):1138-48
references: 21827949
references: Nature. 2014 Jul 3;511(7507):94-8
references: 24847884
references: J Mol Biol. 2007 Sep 21;372(3):774-97
references: 17681537
references: Trends Immunol. 2004 Dec;25(12):677-86
references: 15530839
references: Chem Biol. 2005 Mar;12(3):267-77
references: 15797210
references: Biochemistry. 2001 Sep 11;40(36):10782-91
references: 11535053
references: Acta Crystallogr D Biol Crystallogr. 2004 Dec;60(Pt 12 Pt 1):2126-32
references: 15572765
references: Cancer Cell. 2011 Apr 12;19(4):541-55
references: 21481794
references: J Biol Chem. 1994 Feb 18;269(7):4974-8
references: 8106472
references: J Appl Crystallogr. 2012 Mar 15;45(Pt 2):342-350
references: 25484842
references: Cell Mol Life Sci. 2008 Aug;65(16):2574-85
references: 18470479