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Updated: May 30, 2026

Isolation of Primary Mouse Hepatocytes for Nascent Protein Synthesis Analysis by Non-radioactive L-azidohomoalanine Labeling Method
Published on: October 23, 2018
The non-proteinogenic amino acids L-methionine sulfoximine and DL-phosphinothricin activate mTOR
Saverio Tardito1, Martina Chiu, Renata Franchi-Gazzola
1Unit of General and Clinical Pathology, Department of Experimental Medicine, University of Parma, Via Volturno 39, 43125, Parma, Italy.
Abstract:
L-Methionine sulfoximine (MSO) and DL-Phosphinothricin (PPT), two non-proteinogenic amino acids known as inhibitors of Glutamine Synthetase, cause a dose-dependent increase in the phosphorylation of the mTOR substrate S6 kinase 1. The effect is particularly evident in glutamine-depleted cells, where mTOR activity is very low, but is detectable for PPT also in the presence of glutamine. The stimulation of mTOR activity by either MSO or PPT is strongly synergized by essential amino acids. Thus, the non-proteinogenic amino acids MSO and PPT are mTOR activators.
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