Epitope specificity of anti-synapsin autoantibodies: Differential targeting of synapsin I domains

• Published in: PloS one Vol. 13; no. 12; p. e0208636
• Main Authors: Mertens, Robert, Melchert, Sarah, Gitler, Daniel, Schou, Morten Brix, Saether, Sverre Georg, Vaaler, Arne, Piepgras, Johannes, Kochova, Elena, Benfenati, Fabio, Ahnert-Hilger, Gudrun, Ruprecht, Klemens, Höltje, Markus
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 13.12.2018; Public Library of Science (PLoS)
• Subjects: Adult; Aged; Analysis; Antibodies; Antigenic determinants; Autoantibodies; Autoantibodies - blood; Autoimmunity; Biology and Life Sciences; Case-Control Studies; Cerebrospinal fluid; Disease; Domains; Encephalitis; Epitopes; Epitopes - immunology; Female; HEK293 Cells; Hospitals; Humans; Immunoglobulin A; Immunoglobulin A - blood; Immunoglobulin G; Immunoglobulin G - blood; Immunoglobulin G - classification; Immunoglobulins; Male; Medicine and Health Sciences; Mental Disorders - cerebrospinal fluid; Mental Disorders - pathology; Mental health; Middle Aged; Multiple sclerosis; Nerve tissue proteins; Nervous system diseases; Neurodegenerative Diseases - cerebrospinal fluid; Neurodegenerative Diseases - pathology; Neurological diseases; Neurology; Neurosciences; Patients; Protein Domains - immunology; Proteins; Psychiatry; Research and Analysis Methods; Synapsin I; Synapsins - chemistry; Synapsins - immunology; Synapsins - metabolism; Young Adult; Norway; Germany
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0208636

To identify the specific domains of the presynaptic protein synapsin targeted by recently described autoantibodies to synapsin. Sera of 20 and CSF of two patients with different psychiatric and neurological disorders previously tested positive for immunoglobulin (Ig)G antibodies to full-length synapsin were screened for IgG against synapsin I domains using HEK293 cells transfected with constructs encoding different domains of rat synapsin Ia. Additionally, IgG subclasses were determined using full-length synapsin Ia. Serum and CSF from one patient were also screened for IgA autoantibodies to synapsin I domains. Sera from nine and CSF from two healthy subjects were analyzed as controls. IgG in serum from 12 of 20 IgG synapsin full-length positive patients, but from none of the healthy controls, bound to synapsin domains. Of these 12 sera, six bound to the A domain, five to the D domain, and one to the B- (and possibly A-), D-, and E-domains of synapsin I. IgG antibodies to the D-domain were also detected in one of the CSF samples. Determination of IgG subclasses detected IgG1 in two sera and one CSF, IgG2 in none of the samples, IgG3 in two sera, and IgG4 in eight sera. One patient known to be positive for IgA antibodies to full-length synapsin had IgA antibodies to the D-domain in serum and CSF. Anti-synapsin autoantibodies preferentially bind to either the A- or the D-domain of synapsin I.