title: Subsarcolemmal and intermyofibrillar mitochondria proteome differences disclose functional specializations in skeletal muscle.
abstract: Skeletal muscle is a highly specialized tissue that contains two distinct mitochondria subpopulations, the subsarcolemmal (SS) and the intermyofibrillar (IMF) mitochondria. Although it is established that these mitochondrial subpopulations differ functionally in several ways, limited information exists about the proteomic differences underlying these functional differences. Therefore, the objective of this study was to biochemically characterize the SS and IMF mitochondria isolated from rat red gastrocnemius skeletal muscle. We separated the two mitochondrial subpopulations from skeletal muscle using a refined method that provides an excellent division of these unique mitochondrial subpopulations. Using proteomics of mitochondria and its subfractions (intermembrane space, matrix and inner membrane), a total of 325 distinct proteins were identified, most of which belong to the functional clusters of oxidative phosphorylation, metabolism and signal transduction. Although more gel spots were observed in SS mitochondria, 38 of the identified proteins were differentially expressed between the SS and IMF subpopulations. Compared to the SS mitochondrial, IMF mitochondria expressed a higher level of proteins associated with oxidative phosphorylation. This observation, coupled with the finding of a higher respiratory chain complex activity in IMF mitochondria, suggests a specialization of IMF mitochondria toward energy production for contractile activity.
authors.affiliation: QOPNA, Chemistry Department, University of Aveiro, Aveiro, Portugal.
authors.forename: Rita
authors.initials: R
authors.lastname: Ferreira
authors.forename: Rui
authors.initials: R
authors.lastname: Vitorino
authors.forename: Renato M P
authors.initials: RM
authors.lastname: Alves
authors.forename: Hans Joachim
authors.initials: HJ
authors.lastname: Appell
authors.forename: Scott K
authors.initials: SK
authors.lastname: Powers
authors.forename: José Alberto
authors.initials: JA
authors.lastname: Duarte
authors.forename: Francisco
authors.initials: F
authors.lastname: Amado
mesh_terms: D000818:Animals; D015153:Blotting, Western; D042967:Electron Transport Complex I; D042963:Electron Transport Complex II; D015180:Electrophoresis, Gel, Two-Dimensional; D008297:Male; D008928:Mitochondria / Q000737:chemistry; D024101:Mitochondrial Proteins / Q000032:analysis* / Q000737:chemistry; D009124:Muscle Proteins / Q000032:analysis* / Q000737:chemistry; D018482:Muscle, Skeletal / Q000737:chemistry; D009210:Myofibrils / Q000737:chemistry* / Q000378:metabolism; D020543:Proteome / Q000032:analysis; D040901:Proteomics / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012508:Sarcolemma / Q000737:chemistry* / Q000378:metabolism; D018709:Statistics, Nonparametric; D053719:Tandem Mass Spectrometry
chemical_list: D024101:Mitochondrial Proteins; D009124:Muscle Proteins; D020543:Proteome; C478189:respiratory complex II; D042963:Electron Transport Complex II; D042967:Electron Transport Complex I