We identified proteins significant for rheumatoid arthritis (RA) in peripheral blood mononuclear cells (PBMCs), and to clarify mechanisms mediated by underlying proteins that may involve in the pathogenesis of RA.
Proteome-wide protein expressions were profiled by employing label-free quantitative proteomics methodology (Easy-nLC1000 and Q-exactive). The t-test was applied to identify differentially expressed proteins (DEP, p ≤ 0.05) between RA case and control samples. Gene Ontology enrichment analyses and Protein-Protein Interaction analyses were performed to annotate functions of DEPs. The selected DEP was validated in independent samples using Simple Western assay. Plasma protein level of α2 component of integrin (ITGA2) was measured by using ELISA. The DEP, ITGA2, was assessed for its effects on T cell proliferation, cell cycle, apoptosis, and inflammatory cytokine expression.
Sixty-four DEPs (p < 0.05) were identified in PBMCs. The selected ITGA2 (Fold Change, FC = 2.20, p = 1.49E-02) was validated to be up-regulated (FC = 12.33, p = 4.90E-2) with RA, and plasma ITGA2 protein level significantly elevated in RA patients vs. controls. Over-expression of ITGA2 could promote proliferation and inhibit apoptosis of Jurkat T cell, and induce IL-8, IFN-γ and TNF-α expression in Jurkat T cells.
ITGA2 protein was significantly over-expressed in PBMCs in RA patients, and affects T cell growth and pro-inflammatory cytokine expression in T cells.