Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California 95616.
Division of Endocrinology and Metabolism, University of California San Diego, La Jolla, California 92093.
J Biol Chem. 2011 Sep 2;286(35):30561-30570. doi: 10.1074/jbc.M111.261685. Epub 2011 Jul 11.
The protein deacetylase, sirtuin 1 (SIRT1), is a proposed master regulator of exercise-induced mitochondrial biogenesis in skeletal muscle, primarily via its ability to deacetylate and activate peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). To investigate regulation of mitochondrial biogenesis by SIRT1 in vivo, we generated mice lacking SIRT1 deacetylase activity in skeletal muscle (mKO). We hypothesized that deacetylation of PGC-1α and mitochondrial biogenesis in sedentary mice and after endurance exercise would be impaired in mKO mice. Skeletal muscle contractile characteristics were determined in extensor digitorum longus muscle ex vivo. Mitochondrial biogenesis was assessed after 20 days of voluntary wheel running by measuring electron transport chain protein content, enzyme activity, and mitochondrial DNA expression. PGC-1α expression, nuclear localization, acetylation, and interacting protein association were determined following an acute bout of treadmill exercise (AEX) using co-immunoprecipitation and immunoblotting. Contrary to our hypothesis, skeletal muscle endurance, electron transport chain activity, and voluntary wheel running-induced mitochondrial biogenesis were not impaired in mKO versus wild-type (WT) mice. Moreover, PGC-1α expression, nuclear translocation, activity, and deacetylation after AEX were similar in mKO versus WT mice. Alternatively, we made the novel observation that deacetylation of PGC-1α after AEX occurs in parallel with reduced nuclear abundance of the acetyltransferase, general control of amino-acid synthesis 5 (GCN5), as well as reduced association between GCN5 and nuclear PGC-1α. These findings demonstrate that SIRT1 deacetylase activity is not required for exercise-induced deacetylation of PGC-1α or mitochondrial biogenesis in skeletal muscle and suggest that changes in GCN5 acetyltransferase activity may be an important regulator of PGC-1α activity after exercise.
蛋白去乙酰化酶 Sirtuin 1（SIRT1）被认为是调节骨骼肌中运动诱导的线粒体生物发生的主要调控因子，主要通过其去乙酰化和激活过氧化物酶体增殖物激活受体-γ共激活因子-1α（PGC-1α）的能力。为了研究 SIRT1 在体内对线粒体生物发生的调节作用，我们生成了骨骼肌中缺乏 SIRT1 去乙酰化酶活性的小鼠（mKO）。我们假设，在安静状态下和运动后，mKO 小鼠的 PGC-1α 去乙酰化和线粒体生物发生会受到损害。我们在离体的伸趾长肌中测定了骨骼肌的收缩特性。通过测量电子传递链蛋白含量、酶活性和线粒体 DNA 表达，在 20 天自愿轮跑后评估了线粒体生物发生。在急性跑步机运动（AEX）后，通过免疫共沉淀和免疫印迹测定了 PGC-1α 的表达、核定位、乙酰化和相互作用蛋白的关联。与我们的假设相反，与野生型（WT）小鼠相比，mKO 小鼠的骨骼肌耐力、电子传递链活性和自愿轮跑诱导的线粒体生物发生并没有受损。此外，AEX 后 PGC-1α 的表达、核转位、活性和去乙酰化在 mKO 与 WT 小鼠之间相似。相反，我们有了一个新的发现，即 AEX 后 PGC-1α 的去乙酰化与乙酰转移酶一般氨基酸合成 5（GCN5）的核含量减少以及 GCN5 与核 PGC-1α 的关联减少同时发生。这些发现表明，SIRT1 去乙酰化酶活性不是运动诱导的 PGC-1α 去乙酰化或骨骼肌线粒体生物发生所必需的，并且提示 GCN5 乙酰转移酶活性的变化可能是运动后 PGC-1α 活性的重要调节因子。
