Immunological and Structural Characterization of Titin Main Immunogenic Region; I110 Domain Is the Target of Titin Antibodies in Myasthenia Gravis
Myasthenia gravis (MG) is an autoimmune disease caused by antibodies targeting the neuromuscular junction (NJ) of skeletal muscles. The major MG autoantigen is nicotinic acetylcholine receptor. Other autoantigens at the NJ include MuSK, LRP4 and agrin. Autoantibodies to the intra-sarcomeric striated...
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MDPI AG
2023-02-01
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| Series: | Biomedicines |
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| Online Access: | https://www.mdpi.com/2227-9059/11/2/449 |
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| author | Christos Stergiou Rhys Williams Jennifer R. Fleming Vasiliki Zouvelou Elpinickie Ninou Francesca Andreetta Elena Rinaldi Ornella Simoncini Renato Mantegazza Julius Bogomolovas John Tzartos Siegfried Labeit Olga Mayans Socrates Tzartos |
| author_facet | Christos Stergiou Rhys Williams Jennifer R. Fleming Vasiliki Zouvelou Elpinickie Ninou Francesca Andreetta Elena Rinaldi Ornella Simoncini Renato Mantegazza Julius Bogomolovas John Tzartos Siegfried Labeit Olga Mayans Socrates Tzartos |
| author_sort | Christos Stergiou |
| collection | DOAJ |
| description | Myasthenia gravis (MG) is an autoimmune disease caused by antibodies targeting the neuromuscular junction (NJ) of skeletal muscles. The major MG autoantigen is nicotinic acetylcholine receptor. Other autoantigens at the NJ include MuSK, LRP4 and agrin. Autoantibodies to the intra-sarcomeric striated muscle-specific gigantic protein titin, although not directed to the NJ, are invaluable biomarkers for thymoma and MG disease severity. Thymus and thymoma are critical in MG mechanisms and management. Titin autoantibodies bind to a 30 KDa titin segment, the main immunogenic region (MIR), consisting of an Ig-FnIII-FnIII 3-domain tandem, termed I109–I111. In this work, we further resolved the localization of titin epitope(s) to facilitate the development of more specific anti-titin diagnostics. For this, we expressed protein samples corresponding to 8 MIR and non-MIR titin fragments and tested 77 anti-titin sera for antibody binding using ELISA, competition experiments and Western blots. All anti-MIR antibodies were bound exclusively to the central MIR domain, I110, and to its containing titin segments. Most antibodies were bound also to SDS-denatured I110 on Western blots, suggesting that their epitope(s) are non-conformational. No significant difference was observed between thymoma and non-thymoma patients or between early- and late-onset MG. In addition, atomic 3D-structures of the MIR and its subcomponents were elucidated using X-ray crystallography. These immunological and structural data will allow further studies into the atomic determinants underlying titin-based autoimmunity, improved diagnostics and how to eventually treat titin autoimmunity associated co-morbidities. |
| first_indexed | 2024-03-11T09:06:39Z |
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| issn | 2227-9059 |
| language | English |
| last_indexed | 2024-03-11T09:06:39Z |
| publishDate | 2023-02-01 |
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| spelling | doaj.art-186ab3b480f74a108ef07beaa5b2468e2023-11-16T19:18:23ZengMDPI AGBiomedicines2227-90592023-02-0111244910.3390/biomedicines11020449Immunological and Structural Characterization of Titin Main Immunogenic Region; I110 Domain Is the Target of Titin Antibodies in Myasthenia GravisChristos Stergiou0Rhys Williams1Jennifer R. Fleming2Vasiliki Zouvelou3Elpinickie Ninou4Francesca Andreetta5Elena Rinaldi6Ornella Simoncini7Renato Mantegazza8Julius Bogomolovas9John Tzartos10Siegfried Labeit11Olga Mayans12Socrates Tzartos13Tzartos NeuroDiagnostics, 115 23 Athens, GreeceDepartment of Biology, University of Konstanz, 78457 Konstanz, GermanyDepartment of Biology, University of Konstanz, 78457 Konstanz, Germany1st Neurology Department, Eginition Hospital, National and Kapodistrian University of Athens, 157 72 Athens, GreeceTzartos NeuroDiagnostics, 115 23 Athens, GreeceFondazione I.R.C.C.S., Istituto Neurologico Carlo Besta, 20133 Milano, ItalyFondazione I.R.C.C.S., Istituto Neurologico Carlo Besta, 20133 Milano, ItalyFondazione I.R.C.C.S., Istituto Neurologico Carlo Besta, 20133 Milano, ItalyFondazione I.R.C.C.S., Istituto Neurologico Carlo Besta, 20133 Milano, ItalySchool of Medicine, University of California, La Jolla, San Diego, CA 92093, USASchool of Medicine, Attikon University Hospital, National and Kapodistrian University of Athens, 124 62 Athens, GreeceDZHK Partner Site Mannheim-Heidelberg, Medical Faculty Mannheim, University of Heidelberg, 68167 Mannheim, GermanyDepartment of Biology, University of Konstanz, 78457 Konstanz, GermanyTzartos NeuroDiagnostics, 115 23 Athens, GreeceMyasthenia gravis (MG) is an autoimmune disease caused by antibodies targeting the neuromuscular junction (NJ) of skeletal muscles. The major MG autoantigen is nicotinic acetylcholine receptor. Other autoantigens at the NJ include MuSK, LRP4 and agrin. Autoantibodies to the intra-sarcomeric striated muscle-specific gigantic protein titin, although not directed to the NJ, are invaluable biomarkers for thymoma and MG disease severity. Thymus and thymoma are critical in MG mechanisms and management. Titin autoantibodies bind to a 30 KDa titin segment, the main immunogenic region (MIR), consisting of an Ig-FnIII-FnIII 3-domain tandem, termed I109–I111. In this work, we further resolved the localization of titin epitope(s) to facilitate the development of more specific anti-titin diagnostics. For this, we expressed protein samples corresponding to 8 MIR and non-MIR titin fragments and tested 77 anti-titin sera for antibody binding using ELISA, competition experiments and Western blots. All anti-MIR antibodies were bound exclusively to the central MIR domain, I110, and to its containing titin segments. Most antibodies were bound also to SDS-denatured I110 on Western blots, suggesting that their epitope(s) are non-conformational. No significant difference was observed between thymoma and non-thymoma patients or between early- and late-onset MG. In addition, atomic 3D-structures of the MIR and its subcomponents were elucidated using X-ray crystallography. These immunological and structural data will allow further studies into the atomic determinants underlying titin-based autoimmunity, improved diagnostics and how to eventually treat titin autoimmunity associated co-morbidities.https://www.mdpi.com/2227-9059/11/2/449titinmyasthenia gravisthymomamain immunogenic regionepitope mappingtitin atomic structure |
| spellingShingle | Christos Stergiou Rhys Williams Jennifer R. Fleming Vasiliki Zouvelou Elpinickie Ninou Francesca Andreetta Elena Rinaldi Ornella Simoncini Renato Mantegazza Julius Bogomolovas John Tzartos Siegfried Labeit Olga Mayans Socrates Tzartos Immunological and Structural Characterization of Titin Main Immunogenic Region; I110 Domain Is the Target of Titin Antibodies in Myasthenia Gravis Biomedicines titin myasthenia gravis thymoma main immunogenic region epitope mapping titin atomic structure |
| title | Immunological and Structural Characterization of Titin Main Immunogenic Region; I110 Domain Is the Target of Titin Antibodies in Myasthenia Gravis |
| title_full | Immunological and Structural Characterization of Titin Main Immunogenic Region; I110 Domain Is the Target of Titin Antibodies in Myasthenia Gravis |
| title_fullStr | Immunological and Structural Characterization of Titin Main Immunogenic Region; I110 Domain Is the Target of Titin Antibodies in Myasthenia Gravis |
| title_full_unstemmed | Immunological and Structural Characterization of Titin Main Immunogenic Region; I110 Domain Is the Target of Titin Antibodies in Myasthenia Gravis |
| title_short | Immunological and Structural Characterization of Titin Main Immunogenic Region; I110 Domain Is the Target of Titin Antibodies in Myasthenia Gravis |
| title_sort | immunological and structural characterization of titin main immunogenic region i110 domain is the target of titin antibodies in myasthenia gravis |
| topic | titin myasthenia gravis thymoma main immunogenic region epitope mapping titin atomic structure |
| url | https://www.mdpi.com/2227-9059/11/2/449 |
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