GPI regulates cell cycle progression of FLS. A, Flow cytometry of the cell cycle of RA-FLS after GPI overexpression and knockdown for 48 hours (left) and the percentages of the indicated cell subsets (right). B, Western blot analysis of the levels of GP78 in RA-FLS after GPI knockdown for 48 hours. C, Western blot analysis of the levels of GP78 in RA-FLS after GPI overexpression for 48 hours (left). The interaction between GPI and GP78 was determined by Co-IP analysis (right). D, Western blot analysis of the levels of P-ERK, ERK and Cyclin D1 in lysates of RA-FLS after GPI overexpression. β-actin was used as a loading control. P values were determined by Wilcoxon signed-rank test (GPI, glucose 6-phosphate isomerase; gp78, glycoprotein 78;RA, rheumatoid arthritis; OA, osteoarthritis; FLS, fibroblast-like synoviocytes; NC, negative control; ERK, extracellular regulated protein kinases).