MAP2K1 and rheumatoid arthritis: As protein kinases play important roles in the pathogenesis of RA, and small-molecule kinase inhibitors have substantially improved clinical outcomes [35], we used the 17 components of PEL to dock with the 8 protein kinases targets including Src, JAK2, MEK1, ERK2, JNK1, p38 MAPK, EGFR and KDR.