Abstract

Objective Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and bone destruction. Abnormal TNF/TNFR signaling leads to various dysregulations in Fibroblast-like synoviocytes (FLSs), including proliferation, migration, and cytokine production. CKLF like MARVEL transmembrane domain containing 6 (CMTM6) plays a crucial role in tumor progression and immune escape. This study aimed to research the function of CMTM6 in fibroblast-like synoviocytes (FLSs) of rheumatoid arthritis (RA). Materials and methods The level of CMTM6 in serum and synovial fluid was detected by enzyme-linked immunosorbent assays (ELISA). CMTM6 was silenced by transfecting FLSs with small interfering RNAs (siRNAs). Proliferation, migration, and apoptosis were assessed using a Cell counting kit-8 (CCK-8), Matrigel invasion assays and flow cytometry respectively. The levels of interleukin-1β (IL-1β) and interleukin-6 (IL-6) of cell culture supernatant were detectd with ELISA. The protein expression level of TNF/TNFR pathway and its downstream NF-κB/MAPK signaling were detected through RNA-sequencing and determined by western blotting (WB). Co-Immunoprecipitation, immunofluorescence and pymol analysis were used to confirm the interaction between CMTM6 and TGF-β-activated kinase 1 (TAK1). We used ubiquitination assay and Cycloheximide (CHX) assay to detect degradation of TAK1. The collagen II-induced arthritis (CIA) mouse model were established in DBA/1 mice and treated with Cmtm6 shRNA (AAV-sh Cmtm6 ) or rAAV vector (AAV-Ctrl). Micro-CT and histological analyses evaluated the severity of arthritis. Results Increased levels of CMTM6 in the serum, synovial fluid and synovial tissues were observed in RA patients. Silencing CMTM6 suppressed proliferation, migration and inflammatory cytokines secretion and promote the apoptosis of FLSs. Mechanistically, CMTM6 maintains the stability of TAK1 by inhibiting its ubiquitin-proteasome degradation, leading to th