Document Type
Article
Department or Administrative Unit
Nutrition Exercise and Health Sciences
Publication Date
6-12-2021
Abstract
Background
Previous work in HEK-293 cells demonstrated the importance of amino acid-induced mTORC1 translocation to the lysosomal surface for stimulating mTORC1 kinase activity and protein synthesis. This study tested the conservation of this amino acid sensing mechanism in human skeletal muscle by treating subjects with chloroquine—a lysosomotropic agent that induces in vitro and in vivo lysosome dysfunction.
Methods
mTORC1 signaling and muscle protein synthesis (MPS) were determined in vivo in a randomized controlled trial of 14 subjects (10 M, 4 F; 26 ± 4 year) that ingested 10 g of essential amino acids (EAA) after receiving 750 mg of chloroquine (CHQ, n = 7) or serving as controls (CON, n = 7; no chloroquine). Additionally, differentiated C2C12 cells were used to assess mTORC1 signaling and myotube protein synthesis (MyPS) in the presence and absence of leucine and the lysosomotropic agent chloroquine.
Results
mTORC1, S6K1, 4E-BP1 and rpS6 phosphorylation increased in both CON and CHQ 1 h post EAA ingestion (P < 0.05). MPS increased similarly in both groups (CON, P = 0.06; CHQ, P < 0.05). In contrast, in C2C12 cells, 1 mM leucine increased mTORC1 and S6K1 phosphorylation (P < 0.05), which was inhibited by 2 mg/ml chloroquine. Chloroquine (2 mg/ml) was sufficient to disrupt mTORC1 signaling, and MyPS.
Conclusions
Chloroquine did not inhibit amino acid-induced activation of mTORC1 signaling and skeletal MPS in humans as it does in C2C12 muscle cells. Therefore, different in vivo experimental approaches are required for confirming the precise role of the lysosome and amino acid sensing in human skeletal muscle.
Recommended Citation
Borack, M. S., Dickinson, J. M., Fry, C. S., Reidy, P. T., Markofski, M. M., Deer, R. R., Jennings, K., Volpi, E., & Rasmussen, B. B. (2021). Effect of the lysosomotropic agent chloroquine on mTORC1 activation and protein synthesis in human skeletal muscle. Nutrition & Metabolism, 18(1). https://doi.org/10.1186/s12986-021-00585-w
Journal
Nutrition & Metabolism
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Rights
© The Author(s) 2021
Included in
Human and Clinical Nutrition Commons, Molecular, Genetic, and Biochemical Nutrition Commons
Comments
This article was originally published Open Access in Nutrition & Metabolism. The full-text article from the publisher can be found here.