Alpha-Taxilin: A Potential Diagnosis and Therapeutics Target in Rheumatoid Arthritis Which Interacts with Key Glycolytic Enzymes Associated with Metabolic Shifts in Fibroblast-Like Synoviocytes.

Background: Rheumatoid Arthritis (RA) is a chronic multifactorial inflammatory autoimmune disease of the synovial joint with unknown etiology. In our previous study, we identified Alpha-Taxilin (α-Taxilin) as one of the upregulated proteins in RA and validated it in different biological samples such as tissue, synovial fluid, and blood cells. Here we further investigated its mechanistic role in RA pathophysiology. Methods: The α-Taxilin was validated in a larger cohort (n = 106) of RA plasma by Enzyme-linked Immunosorbent Assay (ELISA). Interacting proteins were identified by co-immunoprecipitation followed by mass spectrometry, and in silico analyses were done to identify protein-protein interactions and involved pathways. The in vitro knockdown studies were performed on SW982 cells and Rheumatoid Arthritis Fibroblast-like Synoviocyte (RAFLS) to investigate the molecular mechanism of α-Taxilin involved in RA via Western Blot, quantitative real-time polymerase chain reaction (qRT-PCR), and confocal microscopy, which was further validated by in vivo studies via collagen-induced arthritis (CIA) rat model. Results: The plasma level of α-Taxilin was found to be significantly increased in plasma samples from patients with RA compared to osteoarthritis (OA), systemic lupus erythematosus (SLE), and healthy controls (HC). The α-Taxilin was found to be positively correlated with anti-citrullinated peptide antibody (ACPA) levels and DAS score in patients with RA. Seventeen interacting proteins were identified with α-Taxilin, and in silico study suggested that glycolysis and gluconeogenesis pathways are the most affected pathways regulated by α-Taxilin. The in vitro knockdown studies of α-Taxilin resulted in decreased levels of pro-inflammatory cytokines, p65, reactive oxygen species (ROS), and toll-like receptors (TLRs). It also improved macroscopic arthritic score, paw edema, and inflammation in CIA rats. Conclusion: α-Taxilin has been found to be associated with glycolysis and gluconeogenesis. This may lead to a metabolic shift in synovial cells, ROS generation, and TLR activation. Therefore, α-Taxilin can be targeted for its diagnostic and therapeutic potential in RA along with other parameters.