MAPK3 and rheumatoid arthritis: Incubation of HFLS-RA cells at 1-h and 4-h were optimal for phosphorylation of signaling molecules, whereas with 15-min and 30-min incubation only p-Erk1/2 was detected, and the band intensities for p-Erk1/2 were lower than 1-h and 4-h incubation (data not shown).