Glycosylation and the Complement System

Ritchie, Gayle E.; Moffatt, Beryl E.; Sim, Robert B.; Morgan, B. Paul; Dwek, Raymond A.; Rudd, Pauline M.

doi:10.1021/cr990294a

Cited by 157 publications

(126 citation statements)

References 53 publications

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“…There has been a recent interest in studying glycosylation of complement components, and in some instances glycosylation is important for the function of these proteins (11,19,44,46,56). Most complement components are synthesized predominantly in the liver and contain complex biantennary glycans, as displayed in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Both the classical and alternative pathways of complement activation converge at the formation of the C3 convertase and deposition of C3 onto the bacterial surface. As C3 is shared by both complement pathways, it would seem to be a likely target for these exoglycosidases; however, this complement component does not have complex-type N-linked glycans (44). Therefore, the pneumococcal exoglycosidases could act upstream on a regulatory component of complement that affects C3 deposition.…”

Section: Discussionmentioning

confidence: 99%

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Three Surface Exoglycosidases fromStreptococcus pneumoniae, NanA, BgaA, and StrH, Promote Resistance to Opsonophagocytic Killing by Human Neutrophils

Dalia¹,

Standish²,

2010

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Streptococcus pneumoniae (the pneumococcus) is a major human pathogen and a leading cause of inflammatory infections such as pneumonia and otitis media. An important mechanism for host defense against S. pneumoniae is opsonophagocytic killing by neutrophils. To persist in the human host, the pneumococcus has developed strategies to evade opsonization and subsequent neutrophil-mediated killing. Utilizing a genomic approach, we identified NanA, the major pneumococcal neuraminidase, as a factor important for resistance to opsonophagocytic killing in ex vivo killing assays using human neutrophils. The effect of NanA was shown using both type 4 (TIGR4) and type 6A clinical isolates. NanA promotes this resistance by acting in conjunction with two other surface-associated exoglycosidases, BgaA, a ␤-galactosidase, and StrH, an N-acetylglucosaminidase. Experiments using human serum showed that these exoglycosidases reduced deposition of complement component C3 on the pneumococcal surface, providing a mechanism for this resistance. Additionally, we have shown that antibodies in human serum do not contribute to this phenotype. These results demonstrate that deglycosylation of a human serum glycoconjugate(s) by the combined effects of NanA, BgaA, and StrH, is important for resistance to complement deposition and subsequent phagocytic killing of S. pneumoniae.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Three Surface Exoglycosidases fromStreptococcus pneumoniae, NanA, BgaA, and StrH, Promote Resistance to Opsonophagocytic Killing by Human Neutrophils

Dalia¹,

Standish²,

2010

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“…The mature protein consists of a N-terminal H chain with 317 aa residues and a C-terminal L chain with 244 residues (6,7) that are covalently linked via a disulfide bond between residues Cys 309 and Cys 435 (S. A. Tsiftsoglou and A. C. Willis, unpublished data). Each chain contains three occupied Nlinked glycosylation sites contributing 20 -25% (w/w) of the apparent protein molecular mass (8,9). Analysis of the primary structure of fI reveals a unique linear arrangement of domains; a N-terminal fI membrane attack complex domain, an scavenger receptor cysteine-rich domain, and two class A low density lipoprotein receptor domains in the noncatalytic H chain (6,7,10).…”

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confidence: 99%

Human Complement Factor I Does Not Require Cofactors for Cleavage of Synthetic Substrates

Tsiftsoglou

Sim

2004

The Journal of Immunology

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Complement factor I (fI) plays a major role in the regulation of the complement system. It circulates in an active form and has very restricted specificity, cleaving only C3b or C4b in the presence of a cofactor such as factor H (fH), complement receptor type 1, membrane cofactor protein, or C4-binding protein. Using peptide-7-amino-4-methylcoumarin derivatives, we investigated the substrate specificity of fI. There is no previous report of synthetic substrate cleavage by fI, but five substrates were found in this study. A survey of 15 substrates and a range of inhibitors showed that fI has specificity similar to that of thrombin, but with much lower catalytic activity than that of thrombin. fI amidolytic activity has a pH optimum of 8.25, typical of serine proteases and is insensitive to ionic strength. This is in contrast to its proteolytic activity within the fI-C3b-fH reaction, in which the pH optimum for C3b cleavage is <5.5 and the reaction rate is highly dependent on ionic strength. The rate of cleavage of tripeptide 7-amino-4-methylcoumarins by fI is unaffected by the presence of fH or C3(NH3). The amidolytic activity is inhibited by the synthetic thrombin inhibitor Z-d-Phe-Pro-methoxypropylboroglycinepinanediol ester, consistent with previous reports, and by benzenesulfonyl fluorides such as Pefabloc SC. Suramin inhibits fI directly at concentration of 1 mM. Within a range of metal ions tested, only Cr2+ and Fe3+ were found to inhibit both the proteolytic and amidolytic activity of fI.

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“…The f/f o value used was held at 1.45 to follow that used in the C3b study [10] and this is insensitive to the shape and mass changes being observed. The C4b concentrations were determined using an absorption coefficient of 9.5 (1% concentration, wavelength 280 nm and 1 cm path length) calculated from its composition (UNIPROT code P0C0L4 for the C4A allotype), assuming the presence of four oligomannose and complex-type oligosaccharides at Asn207 (β-chain) and at Asn843, Asn1309 and Asn1372 (α-chain) [22,23]. The sequence-predicted molecular masses of C4 and C4b (including four N-glycan chains) were 200.5 and 188.0 kDa, respectively.…”

Section: Auc Measurements Of C4bmentioning

confidence: 99%

“…The C4b models had been created without the addition of biantennary complex-type N-glycan chains. These glycans were added to Asn207, Asn843, Asn1309 and Asn1372 in the best-fit C4b models in extended conformations [22,23]. The effect on the R-factors was minimal and did not affect the conclusions of this study.…”

Section: Atomistic Scattering Modelling Of C4b In Solutionmentioning

confidence: 99%

Domain structure of human complement C4b extends with increasing NaCl concentration: implications for its regulatory mechanism

Fung

Wright

Gor

et al. 2016

Biochemical Journal

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During the activation of complement C4 to C4b, the exposure of its thioester domain (TED) is crucial for the attachment of C4b to activator surfaces. In the C4b crystal structure, TED forms an Arg 104 -Glu 1032 salt bridge to tether its neighbouring macroglobulin (MG1) domain. Here, we examined the C4b domain structure to test whether this salt bridge affects its conformation. Dual polarisation interferometry of C4b immobilised at a sensor surface showed that the maximum thickness of C4b increased by 0.46 nm with an increase in NaCl concentration from 50 to 175 mM NaCl. Analytical ultracentrifugation showed that the sedimentation coefficient s 20,w of monomeric C4b of 8.41 S in 50 mM NaCl buffer decreased to 7.98 S in 137 mM NaCl buffer, indicating that C4b became more extended. Small angle X-ray scattering reported similar R G values of 4.89-4.90 nm for C4b in 137-250 mM NaCl. Atomistic scattering modelling of the C4b conformation showed that TED and the MG1 domain were separated by 4.7 nm in 137-250 mM NaCl and this is greater than that of 4.0 nm in the C4b crystal structure. Our data reveal that in low NaCl concentrations, both at surfaces and in solution, C4b forms compact TED-MG1 structures. In solution, physiologically relevant NaCl concentrations lead to the separation of the TED and MG1 domain, making C4b less capable of binding to its complement regulators. These conformational changes are similar to those seen previously for complement C3b, confirming the importance of this salt bridge for regulating both C4b and C3b.

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Glycosylation and the Complement System

Cited by 157 publications

References 53 publications

Three Surface Exoglycosidases fromStreptococcus pneumoniae, NanA, BgaA, and StrH, Promote Resistance to Opsonophagocytic Killing by Human Neutrophils

Three Surface Exoglycosidases fromStreptococcus pneumoniae, NanA, BgaA, and StrH, Promote Resistance to Opsonophagocytic Killing by Human Neutrophils

Human Complement Factor I Does Not Require Cofactors for Cleavage of Synthetic Substrates

Domain structure of human complement C4b extends with increasing NaCl concentration: implications for its regulatory mechanism

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