FIG. 1.

Activation of PDK4 gene expression by physiological stimuli and by overexpression of PGC-1α. (A) Northern blot studies performed with 15 μg of total RNA isolated from the gastrocnemii of animals following two bouts of exercise as described in Materials and Methods (Ex) or from sedentary controls (C) (n = 4). Blots were sequentially hybridized with probes specific for the genes encoding PGC-1α and PDK4. Representative autoradiographs are shown at the top. Phosphorimage-based quantification of Northern blot signal intensities is shown in the graph. Data represent mean arbitrary units (±SE) normalized to sedentary control values (taken as 1.0). (B) Results of Northern blot analysis performed as described above on gastrocnemius samples immediately following 6 h of cold exposure (Cold) and from room temperature controls (C) (n = 6). Graph represents mean arbitrary units (±SE) as determined by real-time PCR quantification corrected to the 36B4 transcript and normalized to the values for control littermates (taken as 1.0). (C) RNA analysis of PGC-1α and PDK4 gastrocnemius gene expression 1 h and 3 h after a single bout of exercise (n = 4). The graph represents mean arbitrary units (±SE) as determined by RT-PCR corrected to the 36B4 transcript and normalized to the value for sedentary controls (taken as 1.0). (D) RNA analyses and Western blot analysis were performed with samples isolated from Ad-GFP- or Ad-PGC-1α-infected C₂C₁₂ myotubes. (Top) Results of Northern blotting performed as described above. Data represent mean arbitrary units (±SE) as determined by RT-PCR corrected to the 36B4 transcript and normalized to value for control Ad-GFP-infected samples (taken as 1.0). (Bottom) Western blot analysis of whole-cell extracts (25 μg) prepared from C₂C₁₂ myotubes infected with adenovirus vectors expressing GFP or PGC-1α. Asterisks indicate significant differences (P < 0.05) from controls.