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  • 1
    In: European Journal of Immunology, Wiley, Vol. 44, No. 11 ( 2014-11), p. 3403-3412
    Abstract: Post‐translational modifications of proteins significantly affect their structure and function. The carbamylation of positively charged lysine residues to form neutral homoitrulline occurs primarily under inflammatory conditions through myeloperoxidase‐dependent cyanate (CNO − ) formation. We analyzed the pattern of human IgG 1 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 IgG 1 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 IgG 1 followed by subsequent complement activation. This severely hindered complement‐dependent cytotoxicity of therapeutic IgG 1 . 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 IgG 1 and reveals a pivotal role for previously uncharacterized lysine residues in this process.
    Type of Medium: Online Resource
    ISSN: 0014-2980 , 1521-4141
    URL: Issue
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    Language: English
    Publisher: Wiley
    Publication Date: 2014
    detail.hit.zdb_id: 1491907-2
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  • 2
    In: Innate Immunity, SAGE Publications, Vol. 22, No. 3 ( 2016-04), p. 218-229
    Abstract: Carbamylation of lysine residues and protein N-termini is an ubiquitous, non-enzymatic post-translational modification. Carbamylation at sites of inflammation is due to cyanate formation during the neutrophil oxidative burst and may target lysine residues within the antimicrobial peptide LL-37. The bactericidal and immunomodulatory properties of LL-37 depend on its secondary structure and cationic nature, which are conferred by arginine and lysine residues. Therefore, carbamylation may affect the biological functions of LL-37. The present study examined the kinetics and pattern of LL-37 carbamylation to investigate how this modification affects the bactericidal, cytotoxic and immunomodulatory function of the peptide. The results indicated that LL-37 undergoes rapid modification in the presence of physiological concentrations of cyanate, yielding a spectrum of diverse carbamylated peptides. Mass spectrometry analyses revealed that the N-terminal amino group of Leu-1 was highly reactive and was modified almost instantly by cyanate to generate the predominant form of the modified peptide, named LL-37 C1 . This was followed by the sequential carbamylation of Lys-8, Lys-12, and Lys-15 to yield LL-37 C8 , and Lys-15 to yield LL-37 C12,15 . Carbamylation had profound and diverse effects on the structure and biological properties of LL-37. In some cases, anti-inflammatory LL-37 was rapidly converted to pro-inflammatory LL-37.
    Type of Medium: Online Resource
    ISSN: 1753-4259 , 1753-4267
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2016
    detail.hit.zdb_id: 2381250-3
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  • 3
    In: Nephrology Dialysis Transplantation, Oxford University Press (OUP), Vol. 34, No. Supplement_1 ( 2019-06-01)
    Type of Medium: Online Resource
    ISSN: 0931-0509 , 1460-2385
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2019
    detail.hit.zdb_id: 1465709-0
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  • 4
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 8, No. 1 ( 2018-09-20)
    Abstract: Peptidylarginine deiminase (PPAD) is a virulence factor unique to pathogenic Porphyromonas species, especially P. gingivalis . Mechanistically, PPAD activity, in conjunction with Arg-specific gingipains, generates protein fragments with citrullinated C-termini. Such polypeptides are potential de novo epitopes that are key drivers of rheumatoid arthritis. This process could underlie the observed clinical association between rheumatoid arthritis and periodontitis. However, the role of PPAD in host colonization by P. gingivalis and, subsequently, in triggering periodontitis is not known. Therefore, the aim of the current study was to delineate the role of PPAD in bacterial biofilm formation, and to define whether adherence to, invasion of, and host responses to bacteria of gingival keratinocytes depend on PPAD activity. We studied these aspects using PPAD-competent and PPAD-incompetent strains of P. gingivalis , and demonstrated that neither biofilm formation nor its composition was affected by PPAD activity. Similarly, flow cytometry revealed that PPAD did not impact the ability of P. gingivalis to adhere to and, subsequently, invade keratinocytes. Network analyses of gene expression patterns, however, revealed a group of host genes that were sensitive to PPAD activity ( CXCL8 , IL36G , CCL20 , and IL1B ). These genes can be categorized as potent immune modulators belonging to the interleukin 1 system, or chemoattractants of lymphocytes and neutrophils. Thus, we conclude that PPAD, although it is a potent modulator of the immune response, does not affect bacterial biofilm formation or the ability of P. gingivalis to adhere to and invade gingival epithelial cells.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2018
    detail.hit.zdb_id: 2615211-3
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  • 5
    In: Journal of the American Society of Nephrology, Ovid Technologies (Wolters Kluwer Health), Vol. 33, No. 10 ( 2022-10), p. 1841-1856
    Abstract: Dialysis is lifesaving for patients with ESKD, but replaces only 10% of normal kidney function, leaving these patients with a chronic urea overload. One unavoidable consequence of excess urea is carbamylation, a post-translational modification that interferes with biologic functions of proteins. In this study, the authors found that platelets from patients with ESKD exhibit carbamylation-triggered structural alterations in integrin α IIb β 3 , associated with a fibrinogen-binding defect and impaired platelet aggregation. Given that lysine 185 in the β 3 subunit seems to play a pivotal role in receptor activation, carbamylation of this residue may represent a mechanistic link between uremia and dysfunctional primary hemostasis in patients. Supplementation of free amino acids prevented loss of α IIb β 3 function, suggesting amino acid administration may have a beneficial effect on uremic platelet dysfunction. Background Bleeding diatheses, common among patients with ESKD, can lead to serious complications, particularly during invasive procedures. Chronic urea overload significantly increases cyanate concentrations in patients with ESKD, leading to carbamylation, an irreversible modification of proteins and peptides. Methods To investigate carbamylation as a potential mechanistic link between uremia and platelet dysfunction in ESKD, we used liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to quantify total homocitrulline, and biotin-conjugated phenylglyoxal labeling and Western blot to detect carbamylated integrin α IIb β 3 (a receptor required for platelet aggregation). Flow cytometry was used to study activation of isolated platelets and platelet-rich plasma. In a transient transfection system, we tested activity and fibrinogen binding of different mutated forms of the receptor. We assessed platelet adhesion and aggregation in microplate assays. Results Carbamylation inhibited platelet activation, adhesion, and aggregation. Patients on hemodialysis exhibited significantly reduced activation of α IIb β 3 compared with healthy controls. We found significant carbamylation of both subunits of α IIb β 3 on platelets from patients receiving hemodialysis versus only minor modification in controls. In the transient transfection system, modification of lysine 185 in the β 3 subunit was associated with loss of receptor activity and fibrinogen binding. Supplementation of free amino acids, which was shown to protect plasma proteins from carbamylation-induced damage in patients on hemodialysis, prevented loss of α IIb β 3 activity in vitro . Conclusions Carbamylation of α IIb β 3 —specifically modification of the K185 residue—might represent a mechanistic link between uremia and dysfunctional primary hemostasis in patients on hemodialysis. The observation that free amino acids prevented the carbamylation-induced loss of α IIb β 3 activity suggests amino acid administration during dialysis may help to normalize platelet function.
    Type of Medium: Online Resource
    ISSN: 1046-6673 , 1533-3450
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2022
    detail.hit.zdb_id: 2029124-3
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