Staphylococcal protein A inhibits complement activation by interfering with IgG hexamer formation

Cruz, Ana Rita; Boer, Maurits A. den; Strasser, Jürgen; Zwarthoff, Seline A.; Beurskens, Frank J.; Haas, Carla J. C. de; Aerts, Piet C.; Wang, Guanbo; Jong, Rob N. de; Bagnoli, Fábio; Strijp, Jos A. G. van; Kessel, Kok P. M. van; Schuurman, Janine; Preiner, Johannes; Heck, Albert J. R.; Rooijakkers, Suzan H.M.

doi:10.1073/pnas.2016772118

Cited by 67 publications

(59 citation statements)

References 59 publications

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“…In line with recent results, IgG1 and IgG3 antibodies against WTA elicit effective C3b deposition on S. aureus (Fig. 1A) (34). Furthermore, IgG4 did not activate complement on S. aureus (Fig.…”

Section: Igg-mediated Complement Activation Does Not Always Correlatesupporting

confidence: 92%

C1q binding to surface-bound IgG is stabilized by C1r₂s₂proteases

Zwarthoff

Widmer

Kuipers

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Complement is an important effector mechanism for antibody-mediated clearance of infections and tumor cells. Upon binding to target cells, the antibody’s constant (Fc) domain recruits complement component C1 to initiate a proteolytic cascade that generates lytic pores and stimulates phagocytosis. The C1 complex (C1qr2s2) consists of the large recognition protein C1q and a heterotetramer of proteases C1r and C1s (C1r2s2). While interactions between C1 and IgG-Fc are believed to be mediated by the globular heads of C1q, we here find that C1r2s2 proteases affect the capacity of C1q to form an avid complex with surface-bound IgG molecules (on various 2,4-dinitrophenol [DNP]-coated surfaces and pathogenic Staphylococcus aureus). The extent to which C1r2s2 contributes to C1q–IgG stability strongly differs between human IgG subclasses. Using antibody engineering of monoclonal IgG, we reveal that hexamer-enhancing mutations improve C1q–IgG stability, both in the absence and presence of C1r2s2. In addition, hexamer-enhanced IgGs targeting S. aureus mediate improved complement-dependent phagocytosis by human neutrophils. Altogether, these molecular insights into complement binding to surface-bound IgGs could be important for optimal design of antibody therapies.

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Section: Igg-mediated Complement Activation Does Not Always Correlatesupporting

confidence: 92%

C1q binding to surface-bound IgG is stabilized by C1r₂s₂proteases

Zwarthoff

Widmer

Kuipers

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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“…The recombinant production of the hexamerizing IgG1-RGY is reasonably straightforward and similar to the production of normal IgG1 antibodies, whereby the inclusion of the RGY mutations promotes extensive hexamerization in solution, as previously described. 14 , 20 , 57 The production of recombinant IgM, especially in its (IgM) 5 J “pentamer” format, is less straightforward as it requires the appropriate coexpression of the joining J chain and IgM subunits and the correct formation of all inter- and intrachain disulfide bridges ( Figure 1 A,B). Here, a pure aWTA (IgM) 5 J pentamer (with J-chain) was recombinantly expressed and purified by SEC.…”

Section: Resultsmentioning

confidence: 99%

“… 14 The therapeutic potential of these induced IgG hexamers is currently being investigated, especially for their role in complement activation. 17 − 20 …”

Section: Introductionmentioning

confidence: 99%

Extending Native Top-Down Electron Capture Dissociation to MDa Immunoglobulin Complexes Provides Useful Sequence Tags Covering Their Critical Variable Complementarity-Determining Regions

et al. 2021

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Native top-down mass spectrometry (MS) is gaining traction for the analysis and sequencing of intact proteins and protein assemblies, giving access to their mass and composition, as well as sequence information useful for identification. Herein, we extend and apply native top-down MS, using electron capture dissociation, to two submillion Da IgM- and IgG-based oligomeric immunoglobulins. Despite structural similarities, these two systems are quite different. The ∼895 kDa noncovalent IgG hexamer consists of six IgG subunits hexamerizing in solution due to three specifically engineered mutations in the Fc region, whereas the ∼935 kDa IgM oligomer results from the covalent assembly of one joining (J) chain and 5 IgM subunits into an asymmetric “pentamer” stabilized by interchain disulfide bridges. Notwithstanding their size, structural differences, and complexity, we observe that their top-down electron capture dissociation spectra are quite similar and straightforward to interpret, specifically providing informative sequence tags covering the highly variable CDR3s and FR4s of the Ig subunits they contain. Moreover, we show that the electron capture dissociation fragmentation spectra of immunoglobulin oligomers are essentially identical to those obtained for their respective monomers. Demonstrated for recombinantly produced systems, the approach described here opens up new prospects for the characterization and identification of IgMs circulating in plasma, which is important since IgMs play a critical role in the early immune response to pathogens such as viruses and bacteria.

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“…Although they do not impact the interaction with the antigen ( Fig. 2A ), they often prevent the recognition of the antibodies by other proteins and thus can block the antibody-mediated effector functions ( 67 , 68 ). First evidence for the presence of IBPs in mycoplasmas came in 1991, when Lauerman et al showed that two proteins in M. synoviae (∼80 and ∼90 kDa) are able to bind to the Fc part of chicken IgG ( 69 ).…”

Section: Mycoplasmas Directly Target the Host Antibodiesmentioning

confidence: 99%