Scheme of the involvement of C/EBPβ-LAP and -LIP for cartilage and bone destruction in rheumatoid arthritis (RA). Pro-inflammatory cytokines stimulate expression of C/EBPβ-LAP and -LIP in RA synovium. Synovium over-expressing C/EBPβ, particularly LAP, caused cartilage degeneration through MMPs and ADAMTSs. C/EBPβ-LIP promoted osteoclast formation through stimulation of RANKL and repression of OPG leading to bone destruction. ATF4 cooperates with C/EBPβ-LIP to stimulate RANKL expression.