Carbamylation of immunoglobulin abrogates activation of the classical complement pathway

TY - JOUR

T1 - Carbamylation of immunoglobulin abrogates activation of the classical complement pathway

AU - Koro, Catalin

AU - Bielecka, Ewa

AU - Dahl-Knudsen, Anders

AU - Enghild, Jan Johannes

AU - Scavenius, Carsten

AU - Brun, Johan G

AU - Binder, Veronika

AU - Hellvard, Annelie

AU - Bergum, Brith

AU - Jonsson, Roland

AU - Potempa, Jan

AU - Blom, Anna M

AU - Mydel, Piotr

N1 - This article is protected by copyright. All rights reserved.

PY - 2014/11

Y1 - 2014/11

N2 - Post-translational modifications of proteins significantly affect their structure and function. The carbamylation of positively charged lysine residues to form neutral homocitrulline occurs primarily under inflammatory conditions through myeloperoxidase-dependent cyanate (CNO(-) ) formation. We analysed the pattern of human IgG1 carbamylation under inflammatory conditions and the effects that this modification has on the ability of antibodies to trigger complement activation via the classical pathway. We found that the lysine residues of IgG1 are rapidly modified after brief exposure to CNO(-) . Interestingly, modifications were not random, but instead limited to only few lysines within the hinge area and the N-terminal fragment of the CH2 domain. A complement activation assay combined with mass spectrometry analysis revealed a highly significant inverse correlation between carbamylation of several key lysine residues within the hinge region and N-terminus of the CH2 domain and the proper binding of C1q to human IgG1 followed by subsequent complement activation. This severely hindered complement-dependent cytotoxicity of therapeutic IgG1 . The reaction can apparently occur in vivo, as we found carbamylated antibodies in synovial fluid from rheumatoid arthritis patients. Taken together, our data suggest that carbamylation has a profound impact on the complement-activating ability of IgG1 and reveals a pivotal role for previously uncharacterised lysine residues in that process. This article is protected by copyright. All rights reserved.

AB - Post-translational modifications of proteins significantly affect their structure and function. The carbamylation of positively charged lysine residues to form neutral homocitrulline occurs primarily under inflammatory conditions through myeloperoxidase-dependent cyanate (CNO(-) ) formation. We analysed the pattern of human IgG1 carbamylation under inflammatory conditions and the effects that this modification has on the ability of antibodies to trigger complement activation via the classical pathway. We found that the lysine residues of IgG1 are rapidly modified after brief exposure to CNO(-) . Interestingly, modifications were not random, but instead limited to only few lysines within the hinge area and the N-terminal fragment of the CH2 domain. A complement activation assay combined with mass spectrometry analysis revealed a highly significant inverse correlation between carbamylation of several key lysine residues within the hinge region and N-terminus of the CH2 domain and the proper binding of C1q to human IgG1 followed by subsequent complement activation. This severely hindered complement-dependent cytotoxicity of therapeutic IgG1 . The reaction can apparently occur in vivo, as we found carbamylated antibodies in synovial fluid from rheumatoid arthritis patients. Taken together, our data suggest that carbamylation has a profound impact on the complement-activating ability of IgG1 and reveals a pivotal role for previously uncharacterised lysine residues in that process. This article is protected by copyright. All rights reserved.

U2 - 10.1002/eji.201444869

DO - 10.1002/eji.201444869

M3 - Journal article

C2 - 25130613

SN - 0014-2980

VL - 44

SP - 3403

EP - 3412

JO - European Journal of Immunology

JF - European Journal of Immunology

IS - 11

ER -