Evolutionary conservation of the lipopolysaccharide binding site of β2-glycoprotein I

2011 ◽  
Vol 106 (12) ◽  
pp. 1069-1075 ◽  
Author(s):  
Çetin Ağar ◽  
Philip de Groot ◽  
J. Arnoud Marquart ◽  
Joost Meijers
Keyword(s):  
Binding Site ◽  
Antiphospholipid Antibody ◽  
Amino Acid Homology ◽  
Anionic Phospholipids ◽  
Glycoprotein I ◽  
Binding Epitope ◽  
Factor Expression ◽  
Major Antigen ◽  
Domain V ◽  
Lps Binding

Summaryβ2-Glycoprotein I (β2GPI) is a highly abundant plasma protein and the major antigen for autoantibodies in the antiphospholipid syndrome. Recently, we have described a novel function of β2GPI as scavenger of lipopolysaccharide (LPS). With this in mind we investigated the conservation of β2GPI in vertebrates and set out to identify the binding site of LPS within β2GPI. The genome sequences of 42 species were surveyed. Surface plasmon resonance (SPR) was performed with peptides to characterise the binding site of β2GPI for LPS. β2GPI could be identified in most tested vertebrates with a high overall amino acid homology of 80% or more in mammals. SPR revealed that a synthesised peptide (LAFWKTDA) from domain V of β2GPI was able to compete for binding of β2GPI to LPS. The AFWKTDA sequence was completely conserved in all mammals. The peptide containing the LPS binding site attenuated the inhibition by β2GPI in a cellular model of LPS-induced tissue factor expression. Other important sites, such as the binding site for anionic phospholipids and the antiphospholipid antibody binding epitope, were also preserved. β2GPI is highly conserved across the animal kingdom, which suggests that the function of β2GPI may be more important than anticipated.

scholarly journals The Binding Site in β2-Glycoprotein I for ApoER2′ on Platelets Is Located in Domain V

2005 ◽  
Vol 280 (44) ◽  
pp. 36729-36736 ◽  
Author(s):  
Menno van Lummel ◽  
Maarten T. T. Pennings ◽  
Ronald H. W. M. Derksen ◽  
Rolf T. Urbanus ◽  
Bianca C. H. Lutters ◽  
...  
Keyword(s):  
Binding Site ◽  
Glycoprotein I ◽  
Domain V

Identification of the Phospholipid-binding Site of Human β2-Glycoprotein I Domain V by Heteronuclear Magnetic Resonance

2000 ◽  
Vol 304 (5) ◽  
pp. 927-939 ◽  
Author(s):  
Masaru Hoshino ◽  
Yoshihisa Hagihara ◽  
Ichiro Nishii ◽  
Toshio Yamazaki ◽  
Hisao Kato ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Binding Site ◽  
Phospholipid Binding ◽  
Glycoprotein I ◽  
Domain V

116. TROPHOBLAST ANTIPHOSPHOLIPID ANTIBODY INTERNALISATION BY A β2 GLYCOPROTEIN I-ANIONIC PHOSPHOLIPID-MEGALIN COMPLEX

2010 ◽  
Vol 22 (9) ◽  
pp. 34
Author(s):  
C. A. Viall ◽  
L. W. Chamley ◽  
Q. Chen
Keyword(s):  
Antiphospholipid Antibodies ◽  
Recurrent Miscarriage ◽  
First Trimester ◽  
Antiphospholipid Antibody ◽  
Anionic Phospholipid ◽  
Anionic Phospholipids ◽  
Glycoprotein I ◽  
Increased Risk ◽  
Dependent Mechanism ◽  
Risk Of Preeclampsia

Women with antiphospholipid antibodies (aPL) are at an increased risk of preeclampsia, recurrent miscarriage, stillbirth and intrauterine growth restriction. Antiphospholipid antibodies may predispose to these pathologies by damaging the placenta, although exactly how is not understood. Recently, a novel pathogenic mechanism was suggested by work which showed that aPL are specifically internalised by placental trophoblasts where they caused aberrant trophoblast death. Internalisation may occur via an endocytic receptor called megalin in a process that seems to involve at least one of the two components of the antigen for aPL, the anionic phospholipid-binding protein β2 glycoprotein I (β2GPI). However, whether internalisation is also dependent upon anionic phospholipids is unknown. Identifying the receptor pathway responsible for aPL internalisation may provide insight into the pathogenesis of aPL in the placenta. To investigate the process of aPL internalisation, first trimester placental explants were cultured with fluorescently-labeled monoclonal aPL, or a control antibody and/or β2GPI or acetylated β2GPI, which can not bind anionic phospholipids. The explants were then sectioned and the localisation of the aPL, β2GPI, or acetylated β2GPI was determined by confocal microscopy. The localisation of megalin expression in placental explants was determined by immunohistochemistry. Megalin was expressed throughout the syncytiotrophoblast but more strongly in some regions. After an overnight incubation, both aPL and β2GPI, but not control antibodies were co-localised in the cytoplasm of the syncytiotrophoblast. Acetylated β2GPI was not internalised and partially blocked aPL uptake. These results suggest that aPL are internalised into the synctiotrophoblast by a receptor-dependent mechanism involving β2GPI, anionic phospholipids and megalin. This work forms the first step to understanding how aPL are internalised by trophoblasts. Further investigation of this mechanism and the subsequent intracellular effects of aPL may lead to a new therapeutic strategy for aPL-positive pregnant women by preventing the pathogenic effect of aPL on the placenta.

A Novel Dimeric Inhibitor That Targets Dimeric ß2GPI In ß2GPI/Anti-ß2GPI Antibody Complexes.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1142-1142
Author(s):  
Natalia Beglova ◽  
Alexey Kolyada ◽  
Chang-Jin Lee ◽  
Alfredo De Biasio
Keyword(s):  
Human Serum ◽  
Antiphospholipid Syndrome ◽  
Conflicts Of Interest ◽  
Half Maximum ◽  
Anionic Phospholipids ◽  
Starting Point ◽  
Maximum Inhibition ◽  
Major Antigen ◽  
Dimeric Form ◽  
Domain V

Abstract Abstract 1142 ß2GPI is a major antigen for autoantibodies associated with antiphospholipid syndrome, an autoimmune disease characterized by thrombosis and recurrent pregnancy loss. Only the dimeric form of ß2GPI generated by anti-ß2GPI antibodies is pathologically important, in contrast to monomeric ß2GPI which is abundant in plasma. Several cell-surface molecules including anionic phospholipids and ApoER2, a member of the lipoprotein receptor family, are implicated in the pathology of antiphospholipid syndrome. We created a dimeric inhibitor, A1-A1, to selectively target ß2GPI in ß2GPI/antibody complexes. This inhibitor consists of two ligand-binding A1 modules from ApoER2 connected by a flexible linker. A1-A1 disrupts the binding of ß2GPI/antibody complexes with anionic phospholipids and lipoprotein receptors. We compared the potency of A1-A1 to monomeric A1 for inhibition of the binding of ß2GPI/antibody complexes to anionic phospholipids. We tested the inhibition of ß2GPI present in human serum, ß2GPI purified from human plasma and domain V of ß2GPI. We demonstrated that when ß2GPI/antibody complexes are formed, A1-A1 is more effective than A1 in inhibition of the ß2GPI binding to cardiolipin, regardless of the source of ß2GPI. Half maximum inhibition of ß2GPI in human serum in the presence of anti-ß2GPI antibodies was achieved at 9 μM of A1-A1 and 218 μM of A1. Similarly, ß2GPI purified from plasma was inhibited to 50% by 26 μM of A1-A1 and 191 μM of A1. Also, A1-A1 strongly inhibited the binding of dimerized domain V of ß2GPI to cardiolipin compared to monomeric A1. Concentration of A1-A1 and A1 at half maximum inhibition of the binding of ß2GPI domain V to cardiolipin in the presence of dimerization antibodies was 29 μM and 204 μM, respectively. In the absence of anti-ß2GPI antibodies, A1-A1 and A1 were equally inefficient in the inhibition of the binding of monomeric ß2GPI to cardiolipin. The concentration of inhibitor at half-maximum inhibition of the binding of ß2GPI in human serum to cardiolipin was 189 μM for A1-A1 and 176 μM for A1. A novel inhibitor A1-A1 may be a starting point in the development of an effective therapeutic for antiphospholipid syndrome. Disclosures: No relevant conflicts of interest to declare.

The Interaction of β2 Glycoprotein-I and Heparin and Its Effect on β2 Glycoprotein-I Antiphospholipid Antibody Cofactor Function in Plasma

1994 ◽  
Vol 72 (04) ◽  
pp. 578-581 ◽  
Author(s):  
T McNally ◽  
S E Cotterell ◽  
I J Mackie ◽  
D A Isenberg ◽  
S J Machin
Keyword(s):  
Solid Phase ◽  
Pharmaceutical Preparations ◽  
Enzyme Linked Immunosorbent Assay ◽  
Antiphospholipid Antibody ◽  
Biological Functions ◽  
Dermatan Sulphate ◽  
Glycoprotein I ◽  
Crossed Immunoelectrophoresis ◽  
Calcium Heparin ◽  
Cofactor Activity

Summaryβ2 glycoprotein-I (β2GPI), a cofactor for antiphospholipid antibody (aPA) binding, binds to many anionic macromolecules including heparin. The nature of this interaction with heparin is not well understood and its effect on the purported biological functions of β2GPI is unknown.We have examined the interactions of dermatan sulphate (DS) and different pharmaceutical preparations of heparin with β2GPI by crossed immunoelectrophoresis (CIE) and investigated the effect of these agents on plasma levels of p2GPI antigen (β2GPI: Ag) by a standardised enzyme linked immunosorbent assay (ELISA). P2GPI aPA cofactor activity (β2GPI:Cof) was also measured using a modified solid phase an-ti-phosphatidylserine (aPS) ELISA. CIE results confirmed a heparin-β2GPI interaction with unfractionated (UF) heparin. β2GPI:Ag levels were unaffected by any of the preparations investigated. There were no significant differences in β2GPI:Cof activities of the samples containing LMW heparins or DS but levels of β2GPI:Cof were increased in samples containing UF sodium and calcium heparin preparations (0.5 IU/ml Monoparin, p <0.05, and 10 IU/ml Liquemin and Calcipa-rine, p <0.05).

Anticardiolipin and Anti-Beta2 Glycoprotein I Antibodies in Infants Born to Mothers with Antiphospholipid Antibody-Positive Autoimmune Disease: A Follow-Up Study

2006 ◽  
Vol 23 (4) ◽  
pp. 247-252 ◽  
Author(s):  
Mario Motta ◽  
Gaetano Chirico ◽  
Chiara Rebaioli ◽  
David Faden ◽  
Andrea Lojacono ◽  
...  
Keyword(s):  
Autoimmune Disease ◽  
Antiphospholipid Antibody ◽  
Follow Up Study ◽  
Glycoprotein I

Antiphospholipid Antibody Profile Stability Over Time: Prospective Results from APS ACTION Clinical Database and Repository

2020 ◽  
pp. jrheum.200513
Author(s):  
Elena Gkrouzman ◽  
Ecem Sevim ◽  
Jackie Finik ◽  
Danieli Andrade ◽  
Vittorio Pengo ◽  
...  
Keyword(s):  
Multivariable Analysis ◽  
Primary Objective ◽  
Antiphospholipid Antibody ◽  
Long Term Outcomes ◽  
Glycoprotein I ◽  
Baseline Characteristics ◽  
Stored Blood ◽  
Over Time

Objective APS ACTION Registry studies long-term outcomes in persistently antiphospholipid antibody (aPL)-positive patients. Our primary objective was to determine whether clinically meaningful aPL profiles at baseline remain stable over time. Our secondary objectives were to determine a) whether baseline characteristics differ between patients with stable and unstable aPL profiles, and b) predictors of unstable aPL profiles over time. Methods Clinically meaningful aPL profile was defined as positive lupus anticoagulant (LA) test and/or anticardiolipin (aCL)/anti-β2 glycoprotein-I (aβ2GPI) IgG/M ≥40 U. Stable aPL profile was defined as a clinically meaningful aPL profile in at least two-thirds of follow-up measurements. Generalized linear mixed models with logit link were used for primary objective analysis. Results Of 472 patients with clinically meaningful aPL profile at baseline (median follow up: 5.1 years), 366/472 (78%) patients had stable aPL profiles over time, 54 (11%) unstable; and 52 (11%) inconclusive. Time did not significantly affect odds of maintaining a clinically meaningful aPL profile at follow-up in univariate (p=0.906) and multivariable analysis (p=0.790). Baseline triple aPL positivity decreased (Odds Ratio [OR] 0.25, 95% Confidence Interval [CI] 0.10-0.64, p=0.004) and isolated LA test positivity increased (OR 3.3, 95% CI 1.53-7.13, p=0.002) the odds of an unstable aPL profile over time. Conclusion Approximately 80% of our international cohort patients with clinically meaningful aPL profile at baseline maintain such at a median follow-up of five years; triple aPL-positivity increase the odds of a stable aPL profile. These results will guide future validation studies of stored blood samples through APS ACTION Core Laboratories.

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