A mutant human IgG molecule with only one C1q binding site can activate complement and induce lysis of target cells

Michaelsen, Terje E.; Thommesen, John Einar; Ihle, Øistein; Gregers, Tone F.; Sandin, Randi; Brekke, Ole Henrik; Sandlie, Inger

doi:10.1002/eji.200535178

Cited by 11 publications

(11 citation statements)

References 49 publications

(61 reference statements)

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“…The residues K322, P329 and P331 are crucial for complement activation for both IgG1 [5,7,21,23] and verified for K322 of IgG3 [8,23] and for P329 and P331 of IgG3 in this report. Interestingly, when mutation at position 329 was mutated from proline to alanine was performed on the basis of IgG3h1 (IgG3 with a hinge of IgG1), the resulting IgG3h1P329A molecule was devoid of ADCML activity even at high target antigen concentration [33]. Apparently residue proline 329 is even more crucial for ADCML activity, at least for IgG3, than residue lysine 322.…”

Section: Residues Lys322 Pro329 and Pro331mentioning

confidence: 99%

Structural Difference in the Complement Activation Site of Human IgG1 and IgG3

et al. 2009

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The C1q binding epicentre on IgG molecules involves residues Asp270, Lys322, Pro329 and Pro331 in the CH2 domain. IgG1 and IgG3 are usually the most efficient of the four human IgG subclasses in activating complement and they both share all these residues. To reveal possible differences in the structural requirement for complement activation, we created a number of NIP (5‐iodo‐4‐hydroxy‐3‐nitro‐phenacetyl) specific IgG1 and IgG3 antibodies with parallel mutations in or near the putative C1q binding site. The mutants were tested simultaneously for antibody induced, antibody‐dependent complement‐mediated lysis (ADCML) at high and low antigen concentration on the target cells using sera of human, rabbit and guinea pig as complement source. In addition, we tested the antibodies against target cells decorated with the NP hapten, which has 10‐fold lower affinity for the antibodies compared to the NIP hapten. We also used ELISA methods to measure complement activation. We observed a clear difference between IgG1 and IgG3 localized to residues Asp270, Leu334, Leu335. For all these residues, and especially for Asp270, IgG1 was heavily reduced in complement activation, while IgG3 was only moderated reduced, by alanine substitution. This difference was independent of the long hinge region of IgG3, demonstrated by hinge region truncation of this isotype such that it resembles that of IgG1. This report indicates the presence of structural differences between human IgG1 and IgG3 in the C1q binding site, and points to a specialization of the two isotypes with respect to complement activation.

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Section: Residues Lys322 Pro329 and Pro331mentioning

confidence: 99%

Structural Difference in the Complement Activation Site of Human IgG1 and IgG3

et al. 2009

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“…Lys B136 was selected as a residue from the apo plane, which is located near the bottom side of ghB and far away from any proposed binding site. (31)(32)(33)(34)(35). Chemical modification, mutational analysis, and molecular modeling approaches have been used to dissect the complementary IgG binding sites on the gC1q domain (7,10,11,19).…”

Section: Certain Key Residues Belonging To the Apo And Holo Planes Ofmentioning

confidence: 99%

Interaction of C1q with IgG1, C-reactive Protein and Pentraxin 3: Mutational Studies Using Recombinant Globular Head Modules of Human C1q A, B, and C Chains

et al. 2006

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C1q is the first subcomponent of the classical complement pathway that can interact with a range of biochemically and structurally diverse self and nonself ligands. The globular domain of C1q (gC1q), which is the ligand-recognition domain, is a heterotrimeric structure composed of the Cterminal regions of A (ghA), B (ghB), and C (ghC) chains. The expression and functional characterization of ghA, ghB, and ghC modules have revealed that each chain has specific and differential binding properties toward C1q ligands. It is largely considered that C1q-ligand interactions are ionic in nature; however, the complementary ligand-binding sites on C1q and the mechanisms of interactions are still unclear. To identify the residues on the gC1q domain that are likely to be involved in ligand recognition, we have generated a number of substitution mutants of ghA, ghB, and ghC modules and examined their interactions with three selected ligands: IgG1, Creactive protein (CRP), and pentraxin 3 (PTX3). Our results suggest that charged residues belonging to the apex of the gC1q heterotrimer (with participation of all three chains) as well as the side of the ghB are crucial for C1q binding to these ligands, and their contribution to each interaction is different. It is likely that a set of charged residues from the gC1q surface participate † This study was supported by the National Science Foundation of Bulgaria, Grant MY-K-1303 to L.T.R. and L-1000 to M.S.K. R.G.is sponsored by the Deutsche Forschungsgemeinschaft through the Graduiertenkolleg GK370. U.K. is funded by the European Commission, University of Oxford, and the Alexander von Humboldt Foundation. A.M. and B.B. are funded by TELETHON, MIUR (FIRB Fund), the European Commission, and AIRC.© 2006 American Chemical Society * Corresponding author. Phone: +44-1865+44- -222325. Fax: +44-1865 +49-641-9941259. ukishore@hotmail.comu.kishore@rediffmail.com. NIH Public Access Author ManuscriptBiochemistry. Author manuscript; available in PMC 2013 December 29. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript via different ionic and hydrogen bonds with corresponding residues from the ligand, instead of forming separate binding sites. Thus, a recently proposed model suggesting the rotation of the gC1q domain upon ligand recognition may be extended to C1q interaction with CRP and PTX3 in addition to IgG1.C1q is the first subcomponent of the classical complement pathway and its binding to IgGor IgM-containing immune complexes leads to the autoactivation of C1r, which in turn, activates C1s. C1r and C1s, the two serine protease proenzymes, together with C1q constitute C1, the first component of the classical pathway. The activation of the C1 complex (C1q + C1r2 + C1s2) subsequently leads to the activation of the C2−C9 components of the classical pathway and the formation of the terminal-membrane-attack complex (MAC) (1, 2). C1q is a versatile innate immune molecule that can bind a diverse range of self and nonself ligands, ranging from proteins to lipids ...

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“…By immuno-histochemical methods and radioimmunoassay, we and others have previously shown that IgG2b binding to AChR at the neuro-muscular junction (NMJ), triggers complement activation that leads to formation of the membrane attack complex (MAC), which depletes functional muscle AChRs at the NMJ (Nakano and Engel, 1993; Kusner and Kaminski, 2012; Tüzün and Christadoss, 2013). Complement activation by anti-AChR antibody is required for AChR depletion and EAMG development (Michaelsen et al, 2006). However, while mouse IgG2b (as well as mouse IgG2a and IgG3 and human IgG1 and IgG3) effectively activates the classical complement cascade, mouse IgG1 and human IgG2 and IgG4 have little or no ability to do this (Redpath et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

IgG1 deficiency exacerbates experimental autoimmune myasthenia gravis in BALB/c mice

Huda

Strait

Tüzün

et al. 2015

Journal of Neuroimmunology

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Myasthenia gravis is an autoimmune disease characterized by muscle weakness due to neuromuscular junction (NMJ) damage by anti-acetylcholine receptor (AChR) auto-antibodies and complement. In experimental autoimmune myasthenia gravis (EAMG), which is induced by immunization with Torpedo AChR in CFA, anti-AChR IgG2b and IgG1 are the predominant isotypes in the circulation. Complement activation by isotypes such as IgG2b plays a crucial role in EAMG pathogenesis; this suggested the possibility that IgG1, which does not activate complement through the classical pathway, may suppress EAMG. In this study, we show that AChR-immunized BALB/c mice genetically deficient for IgG1 produce higher levels of complement-activating isotypes of anti-AChR, especially IgG3 and IgG2a, and develop increased IgG3/IgG2a deposits at the NMJ, as compared to wild type (WT) BALB/c mice. Consistent with this, AChR-immunized IgG1−/− BALB/c mice lose muscle strength and muscle AChR to a greater extent than AChR-immunized WT mice. These observations demonstrate that IgG1 deficiency leads to increased severity of EAMG associated with an increase in complement activating IgG isotypes. Further studies are needed to dissect the specific role or mechanism of IgG1 in limiting EAMG and that of EAMG exacerbating role of complement activating IgG3 and IgG2a in IgG1 deficiency.

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A mutant human IgG molecule with only one C1q binding site can activate complement and induce lysis of target cells

Cited by 11 publications

References 49 publications

Structural Difference in the Complement Activation Site of Human IgG1 and IgG3

Structural Difference in the Complement Activation Site of Human IgG1 and IgG3

Interaction of C1q with IgG1, C-reactive Protein and Pentraxin 3: Mutational Studies Using Recombinant Globular Head Modules of Human C1q A, B, and C Chains

IgG1 deficiency exacerbates experimental autoimmune myasthenia gravis in BALB/c mice

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