Figure 6.

NE cleaves SIRT1 at multiple sites. BEAS-2B cells were transiently transfected with control or SIRT1 siRNA. Forty-eight hours after transfection, the cells were treated with NE (1 or 3 units/ml) for 4 h. Total RNA was isolated and quantitative real-time PCR for SIRT1 and GAPDH was performed (A). Data represent the mean ± S.D. of triplicates. **, p < 0.05. B and C, total cellular extracts were subjected to Western blot analysis for SIRT1 using two different SIRT1 antibodies that recognize the carboxyl-terminal region or the amino-terminal region of SIRT1, respectively. The results are representative of three independent experiments. n.s., nonspecific; S.E., short exposure; L.E., long exposure.