The Pathogenic Role of Posttranslational Modification of Plasma N-Linked Glycoprotein to Rheumatoid Arthritis Combined Sjogren$S Syndrome Was Investigated

Primary Sjogren's syndrome (pSS) and Rheumatoid arthritis (RA) both are an autoimunne disease. Primary Sjogren's syndrome occurs by itself, and secondary Sjogren's syndrome (sSS) occurs with RA (RA-sSS). One of the pathogenic roles in both RA and pSS is citrullination of autoantigens. Other posttranslational modification of autoantigens in RA included oxidative, isomerization and glycosylation. The aim of this study was to investigate the pathogenic role of posttranslational modification of plasma N-linked glycoprotein to sSS in RA. We studied a group of 20 female patients with RA, 20 with pSS and 20 with RA-sSS, and 20 healthy volunteers. One-dimensional electrophoresis, nano-liquid chromatography tandem mass spectrometry (Nano-LC-MS/MS), bioinformatic system (PTM-Miner, PTM-Q, Ingenuity pathways analysis and SRM) and Western blot method were used. The change of amount in novel plasma biomarkers (quantity) and quality (posttranslational modification, PTM) was studied in diagnosis of RA, pSS and RA-sSS. In the aspect to discover probable novel RA, pSS and RA-sSS biomarkers, this study includes three parts: 1) to build up a data bank for plasma protein expression and the posttranslational modification profile. 2) Differential analysis between native protein expression and the posttranslationally modified proteins. 3) To confirm and characterize any single target protein in the differential profile analyzed above. We used Western blotting and SRM to validate the differentially expressed proteins and PTM peptide. It is noted that protein posttranslational modification is significant in eukaryotic physiology; therefore, in order to determine all variety of modifications of plasma proteins, the samples will be analyzed by the MS data in conjunction with bioinformatic software. All 300 types of modifications and a complete set plasma proteins expression will be performed and identified entirely in our assay. Specific protein with different levels of modification are then determined, and confirmed on samples from other patients. On single target proteins, the degree of modification of specific peptides may play a role on the incidence of the disease. Human plasma protein can be analyzed quantitatively (levels of expression) and qualitatively (posttranslational modification) by using proteomic analysis. Our proteomic strategies and Ingenuity Pathway Analysis are valid to identify novel biomarkers for clinical RA, pSS and RA-sSS diagnosis and investigate the pathogenic role of novel PTM of plasma N-linked glycoprotein to RA-sSS.