hamilton-differntiallocalization-2017.pdf (3.91 MB)
Differential localization and anabolic responsiveness of mTOR complexes in human skeletal muscle in response to feeding and exercise
journal contribution
posted on 2017-12-01, 00:00 authored by Nathan Hodson, Chris McGlory, Sara Y Oikawa, Stewart Jeromson, Zhe Song, Markus A Rüegg, Lee HamiltonLee Hamilton, Stuart M Phillips, Andrew PhilpMechanistic target of rapamycin (mTOR) resides as two complexes within skeletal muscle. mTOR complex 1 [mTORC1-regulatory associated protein of mTOR (Raptor) positive] regulates skeletal muscle growth, whereas mTORC2 [rapamycin-insensitive companion of mTOR (Rictor) positive] regulates insulin sensitivity. To examine the regulation of these complexes in human skeletal muscle, we utilized immunohistochemical analysis to study the localization of mTOR complexes before and following protein-carbohydrate feeding (FED) and resistance exercise plus protein-carbohydrate feeding (EXFED) in a unilateral exercise model. In basal samples, mTOR and the lysosomal marker lysosomal associated membrane protein 2 (LAMP2) were highly colocalized and remained so throughout. In the FED and EXFED states, mTOR/LAMP2 complexes were redistributed to the cell periphery [wheat germ agglutinin (WGA)-positive staining] (time effect; P = 0.025), with 39% (FED) and 26% (EXFED) increases in mTOR/WGA association observed 1 h post-feeding/exercise. mTOR/WGA colocalization continued to increase in EXFED at 3 h (48% above baseline) whereas colocalization decreased in FED (21% above baseline). A significant effect of condition (P = 0.05) was noted suggesting mTOR/WGA colocalization was greater during EXFED. This pattern was replicated in Raptor/WGA association, where a significant difference between EXFED and FED was noted at 3 h post-exercise/feeding (P = 0.014). Rictor/WGA colocalization remained unaltered throughout the trial. Alterations in mTORC1 cellular location coincided with elevated S6K1 kinase activity, which rose to a greater extent in EXFED compared with FED at 1 h post-exercise/feeding (P < 0.001), and only remained elevated in EXFED at the 3 h time point (P = 0.037). Collectively these data suggest that mTORC1 redistribution within the cell is a fundamental response to resistance exercise and feeding, whereas mTORC2 is predominantly situated at the sarcolemma and does not alter localization.
History
Journal
American journal of physiology. Cell physiologyVolume
313Issue
6Pagination
C604 - C611Publisher
American Physiological SocietyLocation
Bethesda, Md.Publisher DOI
ISSN
0363-6143eISSN
1522-1563Language
engPublication classification
C1 Refereed article in a scholarly journalCopyright notice
2017, American Physiological SocietyUsage metrics
Keywords
RaptorRictorlysosomemTORC1mTORC2AdultDietary CarbohydratesDietary ProteinsEatingEnergy MetabolismExerciseHumansLysosomal-Associated Membrane Protein 2LysosomesMaleMechanistic Target of Rapamycin Complex 1Mechanistic Target of Rapamycin Complex 2Muscle ContractionProtein TransportProto-Oncogene Proteins c-aktQuadriceps MuscleRapamycin-Insensitive Companion of mTOR ProteinRegulatory-Associated Protein of mTORResistance TrainingRibosomal Protein S6 Kinases, 70-kDaSarcolemmaTime FactorsYoung AdultScience & TechnologyLife Sciences & BiomedicineCell BiologyPhysiologyPROTEIN-SYNTHESISAMINO-ACIDSRESISTANCE EXERCISERAPAMYCINPHOSPHORYLATIONACTIVATIONINCREASETARGETPhysiology
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