Responsiveness of serine racemase promoter to Aβ. The human serine racemase upstream regulatory region was cloned into a firefly luciferase reporter construct. HAPI microglial cells were cotransfected with this construct and a vector encoding Renilla luciferase under control of a constitutive promoter. After transfection, the cells were treated in serum-free medium with 0.3% DMSO ("Control"), 15 μM Aβ1–42 or 100 ng/mL LPS. Luciferase activity was measured after 24 h and is represented as firefly luciferase signal, relative to Renilla luciferase signal in the same well (mean of quadruplicates ± SEM; * p < 0.02; ** p < 0.001). Results are representative of three separate experiments.