Franzini-Armstrong Clara, Boncompagni Simona
Department of Cell and Developmental Biology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
J Biomed Biotechnol. 2011;2011:830573. doi: 10.1155/2011/830573. Epub 2011 Oct 13.
The spatial relationship between mitochondria and the membrane systems, more specifically the calcium release units (CRUs) of skeletal muscle, is of profound functional significance. CRUs are the sites at which Ca(2+) is released from the sarcoplasmic reticulum during muscle activation. Close mitochondrion-CRU proximity allows the organelles to take up Ca(2+) and thus stimulate aerobic metabolism. Skeletal muscles of most mammals display an extensive, developmentally regulated, close mitochondrion-CRU association, fostered by tethering links between the organelles. A comparative look at the vertebrate subphylum however shows that this specific association is only present in the higher vertebrates (mammals). Muscles in all other vertebrates, even if capable of fast activity, rely on a less precise and more limited mitochondrion-CRU proximity, despite some tethering connections. This is most evident in fish muscles. Clustering of free subsarcolemmal mitochondria in proximity of capillaries is also more frequently achieved in mammalian than in other vertebrates.
线粒体与膜系统之间的空间关系，更具体地说是与骨骼肌钙释放单元（CRUs）之间的空间关系，具有深远的功能意义。CRUs是肌肉激活过程中钙离子从肌浆网释放的部位。线粒体与CRUs紧密相邻，使得这些细胞器能够摄取钙离子，从而刺激有氧代谢。大多数哺乳动物的骨骼肌表现出广泛的、受发育调控的线粒体与CRUs紧密关联，这种关联由细胞器之间的连接链所促进。然而，对脊椎动物亚门的比较研究表明，这种特定的关联仅存在于高等脊椎动物（哺乳动物）中。所有其他脊椎动物的肌肉，即使能够进行快速活动，尽管存在一些连接，但线粒体与CRUs的相邻关系较不精确且更为有限。这在鱼类肌肉中最为明显。与其他脊椎动物相比，哺乳动物的游离肌膜下线粒体在毛细血管附近聚集的情况也更为常见。
