Valosin-Containing Protein is a Novel Autoantigen in Patients with Glaucoma

Abstract

The purpose of this study was to identify novel autoantigens that react with specific serum autoantibodies in patients with glaucoma. Sera from patients with glaucoma (n = 80) and healthy subjects without a known pathology (n = 20) were investigated by immunoblot performed with bovine optic nerve lysates and resolved by one- and two-dimensional electrophoresis. Proteins in the immunoreactive spots were selected and identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) data analysis. All the sera from subjects were assayed using enzyme-linked immunosorbent assay to identify autoantibodies. We selected two prominent bands with molecular weights of 100 and 220 kDa by 8% sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, and these two bands were only found in the glaucoma patients. Using one-dimensional electrophoresis and LC-MS/MS analyses, we identified these proteins to be valosin-containing protein (VCP) and fodrin, respectively, and using two-dimensional electrophoresis and LC-MS/MS analyses, VCP was identified to be a common target antigen. In patients with primary open angle glaucoma and normal tension glaucoma, the frequency of autoantibodies to recombinant human VCP was 42.0 and 23.3%, respectively (p < 0.002). In the enzyme-linked immunosorbent assay tests, autoantibody titers to recombinant human VCP were significantly higher than that in healthy controls (p < 0.025). VCP represents a potential candidate target for autoantibodies on the optic nerve in patients with glaucoma.