Tamás Huszár a , István Mucsi a,d , Balázs Antus a , Tamás Terebessy a , Csaba Jeney b , András Masszi a , László Hunyady c , Balázs Mihalik c , Howard J. Goldberg e , Thomas J. Thekkumkara f , László Rosivall a
11 January 2001
To study the role of extracellular-signal-regulated kinase (ERK) cascade and the small GTP-ase proteins in the activation of the c-fos promoter by angiotensin II (AII), transient transfection experiments were performed in CHO cells stably expressing the rat AT<sub>1A</sub> receptor. In this system AII activated ERK in 1 min and also increased the transcriptional activity of the c-fos promoter-luciferase reporter gene construct. The activation of the promoter proved to be dependent on the Ras-Raf-ERK cascade as cotransfection of expression vectors known to specifically inhibit this cascade blocked the effect of AII. Dominant-negative p21Rac1 mutant partially blocked the activation of the c-fos promoter by AII. However, activation of the c-fos promoter was independent of protein kinase C (PKC) as bisindolylmaleimide I, a specific PKC inhibitor did not block the effect of AII. These results suggest that AII activates the transcription of the c-fos through the Ras-Raf-ERK cascade. Furthermore, p21Rac1 is involved in the modulation of the c-fos promoter by AII.