MAPK8 and rheumatoid arthritis: In rheumatoid arthritis, RASGRF1 promotes the production of matrix metalloproteinases by regulating inflammatory processes.35 RASGRF1 can also activate the Rho family GTPase Rac1,36 and Rac1 may play a role in regulating the proliferation and invasiveness of RA-FLS by activating JNK.37 However, the regulatory role of RASGRF1 in RA is still unclear.