PDF(Pubmed)
Abstract：
Succinate dehydrogenase (SDH) is a key mitochondrial enzyme involved in the tricarboxylic acid cycle, where it facilitates the oxidation of succinate to fumarate, and is coupled to the reduction of ubiquinone in the electron transport chain as Complex II. Previously, we developed a confocal-based quantitative histochemical technique to determine the maximum velocity of the SDH reaction (SDHmax) in single cells and observed that SDHmax corresponds with mitochondrial volume density. In addition, mitochondrial volume and motility varied within different compartments of human airway smooth muscle (hASM) cells. Therefore, we hypothesize that the SDH activity varies relative to the intracellular mitochondrial volume within hASM cells. Using 3D confocal imaging of labeled mitochondria and a concentric shell method for analysis, we quantified mitochondrial volume density, mitochondrial complexity index, and SDHmax relative to the distance from the nuclear membrane. The mitochondria within individual hASM cells were more filamentous in the immediate perinuclear region and were more fragmented in the distal parts of the cell. Within each shell, SDHmax also corresponded to mitochondrial volume density, where both peaked in the perinuclear region and decreased in more distal parts of the cell. Additionally, when normalized to mitochondrial volume, SDHmax was lower in the perinuclear region when compared to the distal parts of the cell. In summary, our results demonstrate that SDHmax measures differences in SDH activity within different cellular compartments. Importantly, our data indicate that mitochondria within individual cells are morphologically heterogeneous, and their distribution varies substantially within different cellular compartments, with distinct functional properties.
摘要：
琥珀酸脱氢酶（SDH）是参与三羧酸循环的关键线粒体酶，它促进琥珀酸盐氧化为富马酸盐，并与电子传输链中泛醌的还原偶联为络合物II。以前,我们开发了一种基于共聚焦的定量组织化学技术来确定单个细胞中SDH反应的最大速度（SDHmax），并观察到SDHmax与线粒体体积密度相对应。此外,线粒体体积和运动在人气道平滑肌（hASM）细胞的不同区室中有所不同。因此,我们假设SDH活性相对于hASM细胞内的细胞内线粒体体积而变化。使用标记线粒体的3D共聚焦成像和同心壳方法进行分析，我们量化了线粒体体积密度，线粒体复杂性指数,和SDHmax相对于与核膜的距离。单个hASM细胞内的线粒体在核周围区域中更丝状，在细胞的远端部分中更破碎。在每个shell中，SDHmax也对应于线粒体体积密度，两者都在核周区域达到峰值，在细胞的更远部分降低。此外,当归一化到线粒体体积时，与细胞的远端部分相比，核周区域的SDHmax较低。总之,我们的结果表明,SDHmax测量了不同细胞区室中SDH活性的差异.重要的是,我们的数据表明单个细胞内的线粒体在形态上是异质的，它们的分布在不同的细胞区室中变化很大，具有不同的功能属性。
