| Description |
Essential amino acids (EAA) are a potent stimulator of mammalian target of rapamycin complex 1 (mTORC1) signaling and muscle protein synthesis. However, the molecular regulators upstream of mTORC1 signaling that are stimulated by EAA are not well described in human skeletal muscle. Leucyl tRNA synthetase (LRS) and RagB have recently been shown to be important in mTORC1 activation, but their role in human skeletal muscle following EAA ingestion is unknown. The purpose of this study was to determine changes in protein expression and the association of the LRS- and RagB RagBmTORC1 complexes following acute EAA ingestion in healthy human skeletal muscle. Muscle biopsies (vastus lateralis) were obtained from 13 young adults (7M, 6F, 22.9 ± 0.9y, 21.7 ± 0.9 BMI) in the fasted state (basal) and 1 and 3 h after EAA (13g; 2.4g Leu) ingestion. Co-immunoprecipitation and western blotting were used to determine LRSand RagB-mTORC1 protein complexes and LRS and RagB protein expression, respectively. We report that EAA ingestion did not alter LRS- or RagB-mTORC1 association or LRS protein expression (P > 0.05) contrary to the robust increase in mTOR phosphorylation (P < 0.05). However, we found that EAA increased RagB protein abundance following EAA ingestion (P < 0.05). We conclude that LRS- and RagBmTORC1 complexes are not altered 1 and 3 h following EAA ingestion in healthy young adult skeletal muscle. However, the transient increase in RagB protein expression afterEAA ingestion may be an important mechanism to promote protein anabolism. |
