Pknox1/Prep1 Regulates Mitochondrial Oxidative Phosphorylation Components in Skeletal Muscle

Abstract

eThe homeodomain transcription factor Prep1 was previously shown to regulate insulin sensitivity. Our aim was to study the specific role of Prep1 for the regulation of energy metabolism in skeletal muscle. Muscle-specific ablation of Prep1 resulted in increased expression of respiratory chain subunits. This finding was consistent with an increase in mitochondrial enzyme activity without affecting mitochondrial volume fraction as assessed by electron microscopy. Metabolic phenotyping revealed no differences in daily energy expenditure or body composition. However, during treadmill exercise challenge, Prep1 ablation resulted in a higher maximal oxidative capacity and better endurance. Elevated PGC-1␣ expression was identified as a cause for increased mitochondrial capacity in Prep1 ablated mice. Prep1 stabilizes p160 Mybbp1a, a known inhibitor of PGC-1␣ activity. Thereby, p160 protein levels were significantly lower in the muscle of Prep1 ablated mice. By a chromatin immunoprecipitation-sequencing (ChIP-seq) approach, PREP1 binding sites in genes encoding mitochondrial components (e.g., Ndufs2) were identified that might be responsible for elevated proteins involved in oxidative phosphorylation (OXPHOS) in the muscle of Prep1 null mutants. These results suggest that Prep1 exhibits additional direct effects on regulation of mitochondrial proteins. We therefore conclude that Prep1 is a regulator of oxidative phosphorylation components via direct and indirect mechanisms.

Sarcolipin Is a Key Determinant of the Basal Metabolic Rate, and Its Overexpression Enhances Energy Expenditure and Resistance against Diet-induced Obesity

“…Western Blotting-Expression levels of mitochondrial and other signaling proteins were determined by Western blot as described earlier (20). Skeletal muscle tissues were homogenized in ice-cold homogenization buffer (NaCl, 137 mM; KCl, 2.7 mM; MgCl 2 , 1 mM; Na 4 O 7 P 2 , 5 mM; NaF, 10 mM; Nonidet P-40, 100 1%; glycerol, 10%; Tris (pH 7.8), 20 mM; EDTA, 1 mM; PMSF, 0.2 mM; Na 3 VO 4 , 0.5 mM; and protease inhibitor mixture, 1ϫ (Calbiochem, Merck Millipore, Billerica, MA)).…”

Exercise training alters DNA methylation patterns in genes related to muscle growth and differentiation in mice

“…Citrate synthase activity was measured in the muscle of the mice as a surrogate measurement for changes in oxidative capacity in response to exercise training. Assays were performed as described previously (21). Briefly, frozen quadriceps muscle samples were homogenized in 19 volumes of Tris-EDTA buffer (pH 7.4), and cleared supernatant after centrifugation was used for a spectrophotometric assay.…”

Mitochondrial Abnormalities in Down Syndrome: Pathogenesis, Effects and Therapeutic Approaches

“…Most important, Prep1 ablation significantly increased the abundance of Opa1 and Mfn2, two genes inducing mitochondrial fusion [56]. These results suggest that PREP1 negatively regulates OXPHOS and mitochondrial network.…”

“…PREP1 demonstrated to regulate mitochondrial oxidative phosphorylation components. It directly binds to the promoter region of genes encoding mitochondrial components [56] and indirectly controls the stability of p160 Myb-binding protein, a powerful negative regulator of PGC-1α activity [57].…”