Fig. 6.

CGS inhibition of cAMP stimulation of CT/CGRP promoter activity. Luciferase reporter genes containing 1250, 920, or 280 bp of the 5′-flanking sequence of the CT/CGRP gene or the non-cAMP-responsive 105 bp TK promoter were transfected into CA77 cells. The cAMP-responsive region is indicated by a dotted box, whereas the striped and solid boxes identify the noncell-specific and cell-specific enhancer, respectively. Cells were cotreated with 10 μm forskolin in the presence (+) or absence (−) of 10 μm CGS for 4 hr and assayed for luciferase activity. The activities of the forskolin-treated cells with or without CGS were normalized to vehicle (control) cells. The average activity for the TK control cells was ∼1700 light units per 20 μg of protein. The fold stimulations in response to forskolin and SEM from at least four independent experiments, each in duplicate, are shown.