The evolution of the mitochondria-to-calcium release units relationship in vertebrate skeletal muscles.
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.
Department of Cell and Developmental Biology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. armstroc@mail.med.upenn.edu
Clara
C
Franzini-Armstrong
Simona
S
Boncompagni
D000663:Amphibians; D000818:Animals; D005075:Biological Evolution; D001717:Birds; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism / Q000648:ultrastructure*; D002462:Cell Membrane / Q000648:ultrastructure*; D005399:Fishes; D006801:Humans; D008322:Mammals; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure*; D018482:Muscle, Skeletal / Q000648:ultrastructure*; D012104:Reptiles; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism / Q000648:ultrastructure*; D012519:Sarcoplasmic Reticulum / Q000648:ultrastructure
D015220:Calcium Channels; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium