title: AMP-activated protein kinase is required for exercise-induced peroxisome proliferator-activated receptor co-activator 1 translocation to subsarcolemmal mitochondria in skeletal muscle.
abstract: In skeletal muscle, mitochondria exist as two subcellular populations known as subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria. SS mitochondria preferentially respond to exercise training, suggesting divergent transcriptional control of the mitochondrial genomes. The transcriptional co-activator peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α) and mitochondrial transcription factor A (Tfam) have been implicated in the direct regulation of the mitochondrial genome in mice, although SS and IMF differences may exist, and the potential signalling events regulating the mitochondrial content of these proteins have not been elucidated. Therefore, we examined the potential for PGC-1α and Tfam to translocate to SS and IMF mitochondria in human subjects, and performed experiments in rodents to identify signalling mechanisms regulating these translocation events. Acute exercise in humans and rats increased PGC-1α content in SS but not IMF mitochondria. Acute exposure to 5-aminoimidazole-4-carboxamide-1-β-ribofuranoside in rats recapitulated the exercise effect of increased PGC-1α protein within SS mitochondria only, suggesting that AMP-activated protein kinase (AMPK) signalling is involved. In addition, rendering AMPK inactive (AMPK kinase dead mice) prevented exercise-induced PGC-1α translocation to SS mitochondria, further suggesting that AMPK plays an integral role in these translocation events. In contrast to the conserved PGC-1α translocation to SS mitochondria across species (humans, rats and mice), acute exercise only increased mitochondrial Tfam in rats. Nevertheless, in rat resting muscle PGC-1α and Tfam co-immunoprecipate with α-tubulin, suggesting a common cytosolic localization. These data suggest that exercise causes translocation of PGC-1α preferentially to SS mitochondria in an AMPK-dependent manner.
authors.affiliation: Human Health and Nutritional Sciences, University of Guelph, 491 Gordon St., Guelph, ON, N1G 2W1, Canada. smithb@uoguelph.ca
authors.forename: Brennan K
authors.initials: BK
authors.lastname: Smith
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Mukai
authors.forename: James S
authors.initials: JS
authors.lastname: Lally
authors.forename: Amy C
authors.initials: AC
authors.lastname: Maher
authors.forename: Brendon J
authors.initials: BJ
authors.lastname: Gurd
authors.forename: George J F
authors.initials: GJ
authors.lastname: Heigenhauser
authors.forename: Lawrence L
authors.initials: LL
authors.lastname: Spriet
authors.forename: Graham P
authors.initials: GP
authors.lastname: Holloway
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D003600:Cytosol / Q000378:metabolism; D015444:Exercise; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008931:Mitochondria, Muscle / Q000145:classification / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D005082:Physical Exertion; D021381:Protein Transport; D016601:RNA-Binding Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012508:Sarcolemma / Q000378:metabolism; D015398:Signal Transduction; D013045:Species Specificity; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D055815:Young Adult
chemical_list: D006360:Heat-Shock Proteins; C486497:PPARGC1A protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C485290:Ppargc1a protein, mouse; C501429:Ppargc1a protein, rat; D016601:RNA-Binding Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D055372:AMP-Activated Protein Kinases