RASGRF1 and rheumatoid arthritis: Consistent with the notion that RasGRF1 is involved in the regulation of MMPs, we find that RasGRF1 expression colocalizes to synovial cells producing MMP-1 and MMP-3 in situ, and that modulation of RasGRF1 in RA FLS in vitro regulates spontaneous MMP-3 production by these cells.