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.

Protein composition and function of red and white skeletal muscle mitochondria

“…IMF mitochondria are reported to comprise a greater proportion of the total mitochondrial population in white versus red skeletal muscle (19). The lack of difference in protein composition between red and white mitochondria may indicate that either a similar proportion of IMF and SS mitochondria were isolated from both red and white mitochondria or that IMF and SS mitochondria are not largely different themselves, though the latter would contradict a number of previous reports (1,12,15,50). In addition, while disruption of the mitochondrial reticulum during the isolation process may remove any potential effect fission and fusion events have on mitochondrial composition and/or function, the lack of difference in fission/ fusion proteins OPA1, FIS1, PARL, and MTP18 (Supplemental Materials) suggests these processes may also be similar between red and white skeletal muscle mitochondria.…”

Running‐wheel activity delays mitochondrial respiratory flux decline in aging mouse muscle via a post‐transcriptional mechanism

“…This conversion should be independent of the purity of the mitochondrial preparation, as the enrichment factor for CS is the same as for other proteins in the mitochondrial preparation. This approach does not, however, take into account any mitochondrial inhomogeneity, for example due to preferential isolation of subsarcolemmal over intermyofibrillar mitochondria (Ferreira et al., 2010). …”

A Combined Laser Microdissection and Mass Spectrometry Approach Reveals New Disease Relevant Proteins Accumulating in Aggregates of Filaminopathy Patients

“…Several studies including gel-based and mass spectrometric approaches have been performed that mainly aimed at the global cataloguing and biochemical characterization of the whole rodent muscle proteome or of cellular substructures under physiological and aging conditions (10,11, and for review see (12)). In aged muscles, for example, abundance changes have been detected for proteins involved in metabolism, contractile activity, myofibrillar remodeling, and stress response (12).…”