Fig. 4. Effect of the overexpression of ALK5, ALK1 and Smad isoforms on ALK5- and ALK1-specific reporters and on human ET-1 promoter. The effect of the overexpression of constitutively active (ca) forms of ALK5 and ALK1 on (A) ALK5- and (B) ALK1-specific luciferase reporters was analyzed by cotransfection experiments in BAEC. Overexpression plasmids were cotransfected together with a -650/+172-bp fragment of the human ET-1 promoter linked to a luciferase gene. (C) Effect of ALK5 and ALK1 ca in the absence of TGF- (open bars), and of ALK5 and ALK1 wild type (wt) and kinase-deficient (kd) forms in the presence of 5 ng/ml TGF- (filled bars). (D) Effect of Smad3, Smad1 and Smad5 overexpression in the presence of TGF-. Luciferase activity was measured by luminometry and expressed as fold induction with respect to control pCMV5 empty vector (mean ± s.d., n=4, ^*P<0.05 versus control).