Fig. 10. Proposed scheme of interactions between the FAK/ERK and TGF/Smad pathways in mesangial cell collagen expression. The pathway described in the present study is shown in the box. The exact mechanism(s) by which phosphorylation of the Smad3 linker region and ERK activity affect type I collagen gene transcription are uncertain; therefore, the connections are indicated by broken lines. MEK, a constitutively active form of which we used to directly activate ERK in the absence of phospho-Y397 FAK in Figs 5 and 7, is directly upstream of ERK.