TY - JOUR
T1 - C1q binding to surface-bound IgG is stabilized by C1r2s2 proteases
AU - Zwarthoff, Seline A.
AU - Widmer, Kevin
AU - Kuipers, Annemarie
AU - Strasser, Jürgen
AU - Ruyken, Maartje
AU - Aerts, Piet C.
AU - Haas, Carla J.C. de
AU - Ugurlar, Deniz
AU - Vidarsson, Gestur
AU - Strijp, Jos A. G. Van
AU - Gros, Piet
AU - Parren, Paul W.H.I.
AU - Kessel, Kok P.M. van
AU - Preiner, Johannes
AU - Beurskens, Frank J.
AU - Schuurman, Janine
AU - Ricklin, Daniel
AU - Rooijakkers, Suzan H.M.
N1 - Funding Information:
ACKNOWLEDGMENTS. We kindly thank Dr. Rob de Jong, Prof. Albert Heck, Dr. Annette Stemerding, Dr. Lubka Roemenia, and Dr. Leendert Trouw for scientific advice. We thank Dr. Brandon Garcia for providing BBK32. This work was supported by an European Research Council (ERC) Starting Grant (Grant No. 639209-ComBact to S.H.M.R.) and ERC Advanced Grant (Grant No. 233229-Coco to P.G.), the Utrecht University Molecular Immunology Hub, and the Swiss NSF (Grant No. 31003A_176104 to D.R.). J.P. acknowledges support by the European Fund for Regional Development (Regio 13), the Federal State of Upper Austria, and the Austrian Science Fund (FWF, Grant No. P33958 and P34164).
Publisher Copyright:
© 2021 National Academy of Sciences. All rights reserved.
PY - 2021/6/29
Y1 - 2021/6/29
N2 - Complement is an important effector mechanism for antibodymediated 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.
AB - Complement is an important effector mechanism for antibodymediated 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.
KW - C1
KW - Complement
KW - IgG hexamerization
KW - IgG subclasses
KW - Staphylococcus aureus
KW - Immunoglobulin G/metabolism
KW - Complement C1s/metabolism
KW - Complement Activation
KW - Mutation/genetics
KW - Complement C1q/metabolism
KW - Humans
KW - Protein Multimerization
KW - Staphylococcus aureus/immunology
KW - Complement C1r/metabolism
KW - Cell Membrane/metabolism
KW - Microscopy, Atomic Force
KW - Protein Binding
KW - Protein Stability
KW - Phagocytosis
UR - http://www.scopus.com/inward/record.url?scp=85108321140&partnerID=8YFLogxK
U2 - 10.1073/pnas.2102787118
DO - 10.1073/pnas.2102787118
M3 - Article
C2 - 34155115
SN - 0027-8424
VL - 118
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 26
M1 - e2102787118
ER -