title: Anti-ribosomal-phosphoprotein autoantibodies penetrate to neuronal cells via neuronal growth associated protein, affecting neuronal cells in vitro.
abstract: OBJECTIVE
  Anti-ribosomal-phosphoprotein antibodies (anti-Ribos.P Abs) are detected in 10-45% of NPSLE patients. Intracerebroventricular administration of anti-ribosomal-P Abs induces depression-like behaviour in mice. We aimed to discern the mechanism by which anti-Ribos.P Abs induce behavioural changes in mice.
  
  
  METHODS
  Anti-Ribos.P Abs were exposed to human and rat neuronal cell cultures, as well as to human umbilical vein endothelial cell cultures for a control. The cellular localization of anti-Ribo.P Abs was found by an immunofluorescent technique using a confocal microscope. Identification of the target molecules was undertaken using a cDNA library. Immunohistochemistry and an inhibition assay were carried out to confirm the identity of the target molecules. Neuronal cell proliferation was measured by bromodeoxyuridine, and Akt and Erk expression by immunoblot.
  
  
  RESULTS
  Human anti-Ribos.P Abs penetrated into human neuronal cells and rat hippocampal cell cultures in vitro, but not to endothelial cells as examined. Screening a high-content human cDNA-library with anti-Ribos.P Abs identified neuronal growth-associated protein (GAP43) as a target for anti-Ribos.P Abs. Ex vivo anti-Ribos.P Abs bind to mouse brain sections of hippocampus, dentate and amygdala. Anti-Ribos.P Abs brain-binding was prevented by GAP43 protein. Interestingly, GAP43 inhibited in a dose-dependent manner the anti-Ribos.P Abs binding to recombinant-ribosomal-P0, indicating mimicry between the ribosomal-P0 protein and GAP43. Furthermore, anti-Ribos.P Abs reduced neuronal cell proliferation activity in vitro (P < 0.001), whereas GAP43 decreased this inhibitory activity by a factor of 7.6. The last was related to Akt and Erk dephosphorylation.
  
  
  CONCLUSIONS
  Anti-Ribos.P Abs penetrate neuronal cells in vitro by targeting GAP43. Anti -Ribos.P Abs inhibit neuronal-cell proliferation via inhibition of Akt and Erk. Our data contribute to deciphering the mechanism for anti-Ribos.P Abs' pathogenic activity in NPSLE.
authors.affiliation: The Zabludowicz Center for Autoimmune Diseases, affiliated to Sackler Faculty of Medicine, Tel-Aviv University, Israel.
authors.forename: Shaye
authors.initials: S
authors.lastname: Kivity
authors.affiliation: The Zabludowicz Center for Autoimmune Diseases, affiliated to Sackler Faculty of Medicine, Tel-Aviv University, Israel shoenfel@post.tau.ac.il.
authors.forename: Yehuda
authors.initials: Y
authors.lastname: Shoenfeld
authors.affiliation: The Zabludowicz Center for Autoimmune Diseases, affiliated to Sackler Faculty of Medicine, Tel-Aviv University, Israel Doctoral Program in Biomedical Sciences, Universidad del Rosario, Bogota, Colombia.
authors.forename: Maria-Teresa
authors.initials: MT
authors.lastname: Arango
authors.affiliation: School of Medicine and Medical Sciences, Conway Institute of Biomedical and Biomolecular Research, University College Dublin, Belfield, Ireland.
authors.forename: Dolores J
authors.initials: DJ
authors.lastname: Cahill
authors.affiliation: School of Medicine and Medical Sciences, Conway Institute of Biomedical and Biomolecular Research, University College Dublin, Belfield, Ireland.
authors.forename: Sara Louise
authors.initials: SL
authors.lastname: O'Kane
authors.affiliation: The Zabludowicz Center for Autoimmune Diseases, affiliated to Sackler Faculty of Medicine, Tel-Aviv University, Israel.
authors.forename: Margalit
authors.initials: M
authors.lastname: Zusev
authors.affiliation: Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv.
authors.forename: Inna
authors.initials: I
authors.lastname: Slutsky
authors.affiliation: The Zabludowicz Center for Autoimmune Diseases, affiliated to Sackler Faculty of Medicine, Tel-Aviv University, Israel.
authors.forename: Michal
authors.initials: M
authors.lastname: Harel-Meir
authors.affiliation: Department of Neurology, Sagol Neuroscience Center, Sheba Medical Center, Tel-Hashomer, Israel.
authors.forename: Joab
authors.initials: J
authors.lastname: Chapman
authors.affiliation: AESKU.KIPP Institute, Mikroforum Ring, Wendelsheim, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Matthias
authors.affiliation: The Zabludowicz Center for Autoimmune Diseases, affiliated to Sackler Faculty of Medicine, Tel-Aviv University, Israel.
authors.forename: Miri
authors.initials: M
authors.lastname: Blank
keywords: anti-ribosomal antibodies; autoantibodies; brain cDNA library; neuropsychiatric-systemic lupus erythemathosus; penetration