Maekawa Satoshi, Takada Shingo, Furihata Takaaki, Fukushima Arata, Yokota Takashi, Kinugawa Shintaro
Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
Faculty of Lifelong Sport, Department of Sports Education, Hokusho University, Ebetsu, Japan.
Biochem Biophys Rep. 2019 Dec 18;21:100717. doi: 10.1016/j.bbrep.2019.100717. eCollection 2020 Mar.
Skeletal muscle (SKM) requires a large amount of energy, which is produced mainly by mitochondria, for their daily functioning. Of the several mitochondrial complexes, it has been reported that the dysfunction of complex II is associated with several diseases, including myopathy. However, the degree to which complex II contributes to ATP production by mitochondria remains unknown. As complex II is not included in supercomplexes, which are formed to produce ATP efficiently, we hypothesized that complex II-linked respiration was lower than that of complex I. In addition, differences in the characteristics of complex I and II activity suggest that different factors might regulate their function. The isolated mitochondria from gastrocnemius muscle was used for mitochondrial respiration measurement and immunoblotting in male C57BL/6J mice. Student paired t-tests were performed to compare means between two groups. A univariate linear regression model was used to determine the correlation between mitochondrial respiration and proteins. Contrary to our hypothesis, complex II-linked respiration was not significantly less than complex I-linked respiration in SKM mitochondria (complex I vs complex II, 3402 vs 2840 pmol/[s × mg]). Complex I-linked respiration correlated with the amount of complex I incorporated in supercomplexes ( = 0.727, < 0.05), but not with the total amount of complex I subunits. In contrast, complex II-linked respiration correlated with the total amount of complex II ( = 0.883, < 0.05), but not with the amount of each complex II subunit. We conclude that both complex I and II play important roles in mitochondrial respiration and that the assembly of both supercomplexes and complex II is essential for the normal functioning of complex I and II in mouse SKM mitochondria.
骨骼肌（SKM）的日常功能需要大量能量，这些能量主要由线粒体产生。在几种线粒体复合物中，据报道复合物II功能障碍与包括肌病在内的多种疾病相关。然而，复合物II对线粒体ATP产生的贡献程度尚不清楚。由于复合物II不包含在为高效产生ATP而形成的超复合物中，我们推测复合物II相关的呼吸作用低于复合物I。此外，复合物I和II活性特征的差异表明可能有不同因素调节它们的功能。在雄性C57BL/6J小鼠中，使用从腓肠肌分离的线粒体进行线粒体呼吸测量和免疫印迹。采用学生配对t检验比较两组之间的均值。使用单变量线性回归模型确定线粒体呼吸与蛋白质之间的相关性。与我们的假设相反，在SKM线粒体中，复合物II相关的呼吸作用并不显著低于复合物I相关的呼吸作用（复合物I与复合物II，3402对2840 pmol/[s×mg]）。复合物I相关的呼吸作用与超复合物中结合的复合物I的量相关（r = 0.727，P < 0.05），但与复合物I亚基的总量无关。相比之下，复合物II相关的呼吸作用与复合物II的总量相关（r = 0.883，P < 0.05），但与每个复合物II亚基的量无关。我们得出结论，复合物I和II在小鼠SKM线粒体的呼吸作用中均起重要作用，并且超复合物和复合物II的组装对于复合物I和II在小鼠SKM线粒体中的正常功能至关重要。
