Gain of function mutant of complement factor B K323E mimics pathogenic C3NeF autoantibodies in convertase assays
Complement convertases are enzymatic complexes, which play a critical role in propagation and amplification of the complement cascade. Under physiological conditions, convertases decay shortly after being formed in either spontaneous or inhibitor-driven process. Prolongation of their half-life by C3...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Taylor & Francis Group
2018-01-01
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| Series: | Autoimmunity |
| Subjects: | |
| Online Access: | http://dx.doi.org/10.1080/08916934.2017.1423286 |
| _version_ | 1797684753438081024 |
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| author | Aleksandra Urban Anna Borowska Anna Felberg Lambertus van den Heuvel Grzegorz Stasiłojć Elena Volokhina Marcin Okrój |
| author_facet | Aleksandra Urban Anna Borowska Anna Felberg Lambertus van den Heuvel Grzegorz Stasiłojć Elena Volokhina Marcin Okrój |
| author_sort | Aleksandra Urban |
| collection | DOAJ |
| description | Complement convertases are enzymatic complexes, which play a critical role in propagation and amplification of the complement cascade. Under physiological conditions, convertases decay shortly after being formed in either spontaneous or inhibitor-driven process. Prolongation of their half-life by C3NeF autoantibodies that prevent convertase dissociation results in pathogenic condition often manifested by renal diseases. However, the diagnosis of convertase abnormalities is difficult due to the labile nature of these enzymes and low credibility of existing methods. Only recently, two-step functional assays employing C5-depleted serum or C5 inhibitors were introduced. Their advantage is convertase formation in the physiological milieu of whole serum and the drawback is inter-assay variability due to variations in rabbit erythrocytes used for the haemolysis-based readout. Abovementioned problems demand the application of the internal standard in each experiment. Obtaining a defined preparation of autoantibodies is complicated due to ethical and practical considerations. We found that recombinant, his-tagged factor B (fB) variant K323E retains full hemolytic activity and possess the ability to form convertases with prolonged half-life either in fB-depleted serum or when mixed with normal human serum. Such dominant character of K323E mutation allows using recombinant protein as a reference in functional convertase assays, not limited to these using rabbit erythrocytes. Additionally, our results demonstrate that gain of function mutations in complement components mimic the phenotype of C3NeF. Hence, patients with such “genetic C3NeF” would not benefit from B-cell depletion (e.g. by rituximab) and therefore should be properly diagnosed in order to choose suitable therapeutic intervention. |
| first_indexed | 2024-03-12T00:35:21Z |
| format | Article |
| id | doaj.art-a26babf28a654b5799f92ffe0a4147f7 |
| institution | Directory Open Access Journal |
| issn | 0891-6934 1607-842X |
| language | English |
| last_indexed | 2024-03-12T00:35:21Z |
| publishDate | 2018-01-01 |
| publisher | Taylor & Francis Group |
| record_format | Article |
| series | Autoimmunity |
| spelling | doaj.art-a26babf28a654b5799f92ffe0a4147f72023-09-15T10:01:07ZengTaylor & Francis GroupAutoimmunity0891-69341607-842X2018-01-01511182410.1080/08916934.2017.14232861423286Gain of function mutant of complement factor B K323E mimics pathogenic C3NeF autoantibodies in convertase assaysAleksandra Urban0Anna Borowska1Anna Felberg2Lambertus van den Heuvel3Grzegorz Stasiłojć4Elena Volokhina5Marcin Okrój6Intercollegiate Faculty of Biotechnology UG-GUMEDIntercollegiate Faculty of Biotechnology UG-GUMEDIntercollegiate Faculty of Biotechnology UG-GUMEDRadboud University Medical CenterIntercollegiate Faculty of Biotechnology UG-GUMEDRadboud University Medical CenterIntercollegiate Faculty of Biotechnology UG-GUMEDComplement convertases are enzymatic complexes, which play a critical role in propagation and amplification of the complement cascade. Under physiological conditions, convertases decay shortly after being formed in either spontaneous or inhibitor-driven process. Prolongation of their half-life by C3NeF autoantibodies that prevent convertase dissociation results in pathogenic condition often manifested by renal diseases. However, the diagnosis of convertase abnormalities is difficult due to the labile nature of these enzymes and low credibility of existing methods. Only recently, two-step functional assays employing C5-depleted serum or C5 inhibitors were introduced. Their advantage is convertase formation in the physiological milieu of whole serum and the drawback is inter-assay variability due to variations in rabbit erythrocytes used for the haemolysis-based readout. Abovementioned problems demand the application of the internal standard in each experiment. Obtaining a defined preparation of autoantibodies is complicated due to ethical and practical considerations. We found that recombinant, his-tagged factor B (fB) variant K323E retains full hemolytic activity and possess the ability to form convertases with prolonged half-life either in fB-depleted serum or when mixed with normal human serum. Such dominant character of K323E mutation allows using recombinant protein as a reference in functional convertase assays, not limited to these using rabbit erythrocytes. Additionally, our results demonstrate that gain of function mutations in complement components mimic the phenotype of C3NeF. Hence, patients with such “genetic C3NeF” would not benefit from B-cell depletion (e.g. by rituximab) and therefore should be properly diagnosed in order to choose suitable therapeutic intervention.http://dx.doi.org/10.1080/08916934.2017.1423286complement systemc3nefc3 glomerulopathy dense deposit diseaseahus |
| spellingShingle | Aleksandra Urban Anna Borowska Anna Felberg Lambertus van den Heuvel Grzegorz Stasiłojć Elena Volokhina Marcin Okrój Gain of function mutant of complement factor B K323E mimics pathogenic C3NeF autoantibodies in convertase assays Autoimmunity complement system c3nef c3 glomerulopathy dense deposit disease ahus |
| title | Gain of function mutant of complement factor B K323E mimics pathogenic C3NeF autoantibodies in convertase assays |
| title_full | Gain of function mutant of complement factor B K323E mimics pathogenic C3NeF autoantibodies in convertase assays |
| title_fullStr | Gain of function mutant of complement factor B K323E mimics pathogenic C3NeF autoantibodies in convertase assays |
| title_full_unstemmed | Gain of function mutant of complement factor B K323E mimics pathogenic C3NeF autoantibodies in convertase assays |
| title_short | Gain of function mutant of complement factor B K323E mimics pathogenic C3NeF autoantibodies in convertase assays |
| title_sort | gain of function mutant of complement factor b k323e mimics pathogenic c3nef autoantibodies in convertase assays |
| topic | complement system c3nef c3 glomerulopathy dense deposit disease ahus |
| url | http://dx.doi.org/10.1080/08916934.2017.1423286 |
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