SAT0040 PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR-GAMMA COACTIVATOR-1β FACILITATES PSEUDOPODIA FORMATION OF FIBROBLAST-LIKE SYNOVIOCYTES IN RHEUMATOID ARTHRITIS VIA ACTIVATING RHO GTPASES

Background Fibroblast-like synoviocytes (FLS) play critical roles on joint inflammation and destruction of cartilage and bone in rheumatoid arthritis (RA) due to their aggressive behavior including increased migration. The Rho family of small GTPases are the master regulators of actin cytoskeleton remodeling which leads to pseudopodia formation and migration. Peroxisome proliferator-activated receptor-gamma coactivator-1 (PGC-1) β is a transcriptional regulator which plays important roles on regulating multiple signaling pathways. Our previous study revealed that elevated PGC-1β in RA-FLS promoted their migration and invasion. However, the underlying mechanism remains elusive. Objectives To investigate the role of PGC-1β on regulating pseudopodia formation of RA-FLS and its underlying mechanism. Methods Synovial tissues were obtained from six patients with active RA and FLS were isolated and cultured in vitro. RA-FLS were transfected with a lentivirus vector for PGC-1β knockdown or over-expression, and transfected with same lentivirus vectors marked Lv-sh-GFP or Lv-GFP as negative controls. The change of cytoskeleton was stained with fluorescent phalloidin to visualize polymerized actin in lentivirus transfected RA-FLS. The mRNA expression of RhoA, Rac1, and Cdc42 was measured by qPCR. Their activity was measured using a Rac1, RhoA or Cdc42 Pulldown & G-Lisa Activation Assay Kit. Results 1) PGC-1β knockdown inhibited lamellipodia and filopodia formations of RA-FLS compared with Lv-sh-GFP transfection group (cells with lamellipodia: 24% ± 7% vs. 40% ± 5%, P=0.035; cells with filopodia: 34% ± 9% vs. 49% ± 4%, P=0.041), while PGC-1β over-expression promoted lamellipodia and filopodia formations of RA-FLS compared with Lv-GFP transfection group (cells with lamellipodia: 50% ± 4% vs. 34% ± 6%, P=0.040; cells with filopodia: 67% ± 7% vs. 52% ± 6%, P=0.045, Figure 1A). 2) PGC-1β knockdown or over-expression did not affect the mRNA expression of Rac1, RhoA or Cdc42 (all P>0.05, Figure 1B). However, PGC-1β knockdown suppressed the activity of Rac1, RhoA and Cdc42 (Pulldown assays: 65%∼78% reduction; G-LISA assays: 28%∼53% reduction, all P Conclusion Our findings revealed that elevated PGC-1β in RA-FLS promoted pseudopodia formation by activating Rho family proteins which imply a novel target on regulating RA-FLS migration. Acknowledgement This work was supported by National Natural Science Foundation of China (81671612 and 81801606), Guangdong Natural Science Foundation (2017A030313576, 2017A030310236 and 2018A030313541) and Guangdong Medical Scientific Research Foundation (A2017109). Disclosure of Interests None declared