title: Giardia cyst wall protein 1 is a lectin that binds to curled fibrils of the GalNAc homopolymer.
abstract: The infectious and diagnostic stage of Giardia lamblia (also known as G. intestinalis or G. duodenalis) is the cyst. The Giardia cyst wall contains fibrils of a unique beta-1,3-linked N-acetylgalactosamine (GalNAc) homopolymer and at least three cyst wall proteins (CWPs) composed of Leu-rich repeats (CWP(LRR)) and a C-terminal conserved Cys-rich region (CWP(CRR)). Our goals were to dissect the structure of the cyst wall and determine how it is disrupted during excystation. The intact Giardia cyst wall is thin (approximately 400 nm), easily fractured by sonication, and impermeable to small molecules. Curled fibrils of the GalNAc homopolymer are restricted to a narrow plane and are coated with linear arrays of oval-shaped protein complex. In contrast, cyst walls of Giardia treated with hot alkali to deproteinate fibrils of the GalNAc homopolymer are thick (approximately 1.2 microm), resistant to sonication, and permeable. The deproteinated GalNAc homopolymer, which forms a loose lattice of curled fibrils, is bound by native CWP1 and CWP2, as well as by maltose-binding protein (MBP)-fusions containing the full-length CWP1 or CWP1(LRR). In contrast, neither MBP alone nor MBP fused to CWP1(CRR) bind to the GalNAc homopolymer. Recombinant CWP1 binds to the GalNAc homopolymer within secretory vesicles of Giardia encysting in vitro. Fibrils of the GalNAc homopolymer are exposed during excystation or by treatment of heat-killed cysts with chymotrypsin, while deproteinated fibrils of the GalNAc homopolymer are degraded by extracts of Giardia cysts but not trophozoites. These results show the Leu-rich repeat domain of CWP1 is a lectin that binds to curled fibrils of the GalNAc homopolymer. During excystation, host and Giardia proteases appear to degrade bound CWPs, exposing fibrils of the GalNAc homopolymer that are digested by a stage-specific glycohydrolase.
authors.affiliation: Department of Molecular and Cell Biology, Boston University Goldman School of Dental Medicine, Boston, Massachusetts, USA.
authors.forename: Aparajita
authors.initials: A
authors.lastname: Chatterjee
authors.forename: Andrea
authors.initials: A
authors.lastname: Carpentieri
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Ratner
authors.forename: Esther
authors.initials: E
authors.lastname: Bullitt
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Costello
authors.forename: Phillips W
authors.initials: PW
authors.lastname: Robbins
authors.forename: John
authors.initials: J
authors.lastname: Samuelson
mesh_terms: D000116:Acetylgalactosamine / Q000378:metabolism*; D002469:Cell Separation; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism*; D005434:Flow Cytometry; D016829:Giardia lamblia / Q000737:chemistry* / Q000378:metabolism*; D037102:Lectins / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D015800:Protozoan Proteins / Q000378:metabolism*
chemical_list: C094333:CWP1 protein, Giardia lamblia; D037102:Lectins; D015800:Protozoan Proteins; D000116:Acetylgalactosamine
references.citation: Eukaryot Cell. 2010 Jan;9(1):84-96
references.pmid: 19949049
references.citation: J Clin Microbiol. 1999 Mar;37(3):611-4
references.pmid: 9986821
references.citation: Infect Immun. 2000 Jul;68(7):4217-24
references.pmid: 10858239
references.citation: Curr Opin Microbiol. 2007 Dec;10(6):554-9
references.pmid: 17981075
references.citation: Mol Biochem Parasitol. 2004 Aug;136(2):173-80
references.pmid: 15478797
references.citation: J Biol Chem. 2003 Jun 13;278(24):21701-8
references.pmid: 12686559
references.citation: Mol Microbiol. 2007 Dec;66(5):1164-73
references.pmid: 17971081
references.citation: PLoS Pathog. 2010 Apr 08;6(4):e1000835
references.pmid: 20386711
references.citation: Mol Biochem Parasitol. 1997 Apr;85(2):139-47
references.pmid: 9106188
references.citation: Eukaryot Cell. 2008 Nov;7(11):1930-40
references.pmid: 18820077
references.citation: J Biol Chem. 1995 Dec 8;270(49):29307-13
references.pmid: 7493963
references.citation: Nat Protoc. 2007;2(2):383-91
references.pmid: 17406599
references.citation: J Eukaryot Microbiol. 1996 Sep-Oct;43(5):416-29
references.pmid: 8822813
references.citation: Eukaryot Cell. 2006 May;5(5):836-48
references.pmid: 16682461
references.citation: Infect Immun. 1996 Jun;64(6):2151-7
references.pmid: 8675320
references.citation: Int Rev Cytol. 2003;222:237-93
references.pmid: 12503851
references.citation: Clin Microbiol Rev. 2001 Jul;14(3):447-75
references.pmid: 11432808
references.citation: Science. 1995 Jun 9;268(5216):1483-7
references.pmid: 7770772
references.citation: Science. 2007 Sep 28;317(5846):1921-6
references.pmid: 17901334
references.citation: PLoS Negl Trop Dis. 2010 May 11;4(5):e677
references.pmid: 20485485
references.citation: Microbiology (Reading). 2004 May;150(Pt 5):1237-1243
references.pmid: 15133086
references.citation: Infect Immun. 1999 Apr;67(4):2022-4
references.pmid: 10085053
references.citation: J Mol Evol. 1991 Sep;33(3):283-94
references.pmid: 1757999
references.citation: Microbiol Mol Biol Rev. 2006 Jun;70(2):317-43
references.pmid: 16760306
references.citation: Cell. 1997 May 2;89(3):437-44
references.pmid: 9150143
references.citation: Microbes Infect. 2009 Jan;11(1):20-8
references.pmid: 18992359
references.citation: J Biol Chem. 2001 Jun 8;276(23):19679-82
references.pmid: 11309404
references.citation: J Agric Food Chem. 2006 Feb 8;54(3):597-606
references.pmid: 16448156
references.citation: J Cell Sci. 2009 Aug 15;122(Pt 16):2846-56
references.pmid: 19622633
references.citation: J Biol Chem. 2002 Mar 8;277(10):8474-81
references.pmid: 11773053
references.citation: Mol Microbiol. 1995 Mar;15(5):955-63
references.pmid: 7596296
references.citation: PLoS Pathog. 2009 Jul;5(7):e1000498
references.pmid: 19578434
references.citation: Annu Rev Med. 1997;48:329-40
references.pmid: 9046966
references.citation: Mol Biochem Parasitol. 2007 Mar;152(1):80-9
references.pmid: 17204341
references.citation: Proteomics. 2008 Feb;8(4):893-908
references.pmid: 18210371
references.citation: PLoS One. 2006 Dec 20;1:e44
references.pmid: 17183673
references.citation: PLoS Pathog. 2009 Aug;5(8):e1000560
references.pmid: 19696920
references.citation: Mol Biol Cell. 2000 May;11(5):1789-800
references.pmid: 10793152
references.citation: Methods Enzymol. 1973;27:616-72
references.pmid: 4129766
references.citation: Cell Microbiol. 2001 Jul;3(7):459-72
references.pmid: 11437832
references.citation: Infect Immun. 1990 Nov;58(11):3516-22
references.pmid: 2228222
references.citation: Curr Opin Immunol. 2008 Aug;20(4):377-82
references.pmid: 18585455
references.citation: Proc Natl Acad Sci U S A. 2005 Feb 1;102(5):1548-53
references.pmid: 15665075
references.citation: J Biol Chem. 2006 Jun 30;281(26):18156-66
references.pmid: 16611634
references.citation: Infect Immun. 2002 Jun;70(6):3259-63
references.pmid: 12011021
references.citation: Infect Immun. 2001 Dec;69(12):7866-72
references.pmid: 11705969
references.citation: Mol Biochem Parasitol. 2002 Jun;122(1):95-8
references.pmid: 12076774
references.citation: Glycobiology. 2002 Aug;12(8):499-505
references.pmid: 12145190
references.citation: Mol Biochem Parasitol. 1990 Dec;43(2):151-65
references.pmid: 2128647
references.citation: J Eukaryot Microbiol. 2004 Mar-Apr;51(2):220-6
references.pmid: 15134259
references.citation: Immunity. 2008 Aug 15;29(2):182-91
references.pmid: 18701082