Park S H, Gammon S R, Knippers J D, Paulsen S R, Rubink D S, Winder W W
Department of Zoology, Brigham Young University, Provo, Utah 84602, USA.
J Appl Physiol (1985). 2002 Jun;92(6):2475-82. doi: 10.1152/japplphysiol.00071.2002.
AMP-activated protein kinase (AMPK) is activated during muscle contraction in response to the increase in AMP and decrease in phosphocreatine (PCr). Once activated, AMPK has been proposed to phosphorylate a number of targets, resulting in increases in glucose transport, fatty acid oxidation, and gene transcription. Although it has been possible to directly observe phosphorylation of one of these targets, acetyl-CoA carboxylase (ACC) in vitro, it has been more difficult to obtain direct evidence of ACC phosphorylation in contracting skeletal muscle. In these experiments using a phosphoserine antibody to ACC and a phosphothreonine antibody to AMPK, evidence was obtained for phosphorylation and activation of ACC in vitro, in gastrocnemius muscle electrically stimulated at different frequencies, and in muscle from rats running on the treadmill. Significant negative linear correlations between phospho-ACC and ACC activity were observed in all models (P < 0.01). The decline in ACC activity was related to the decrease in PCr and the rise in AMP. A relationship between phospho-AMPK (threonine 172) and activity of AMPK immunoprecipitated with anti-alpha(2) subunit antibody preparation was also observed. These data provide the first evidence of a direct link between extent of phosphorylation of these proteins at sites recognized by the antibodies and activity of the enzymes in electrically stimulated muscle and in muscle of rats running on the treadmill.
AMP 激活的蛋白激酶（AMPK）在肌肉收缩过程中，因 AMP 增加和磷酸肌酸（PCr）减少而被激活。一旦被激活，AMPK 被认为会磷酸化多个靶点，从而导致葡萄糖转运、脂肪酸氧化和基因转录增加。尽管在体外能够直接观察到这些靶点之一——乙酰辅酶 A 羧化酶（ACC）的磷酸化，但在收缩的骨骼肌中获得 ACC 磷酸化的直接证据则更为困难。在这些实验中，使用针对 ACC 的磷酸丝氨酸抗体和针对 AMPK 的磷酸苏氨酸抗体，在体外、不同频率电刺激的腓肠肌以及跑步机上跑步的大鼠肌肉中，均获得了 ACC 磷酸化和激活的证据。在所有模型中均观察到磷酸化 ACC 与 ACC 活性之间存在显著的负线性相关性（P < 0.01）。ACC 活性的下降与 PCr 的减少和 AMP 的增加有关。还观察到磷酸化 AMPK（苏氨酸 172）与用抗α(2)亚基抗体制备免疫沉淀的 AMPK 活性之间的关系。这些数据首次证明了在电刺激的肌肉和跑步机上跑步的大鼠肌肉中，这些蛋白质在抗体识别位点的磷酸化程度与酶活性之间存在直接联系。
