eLife assessment
In this study, Sparta et al., generated and employed a battery of fluorescent reporters that allowed them to perform time-resolved monitoring of mechanistic target of rapamycin complex 1 (mTORC1) responses to stimuli including glucose, amino acids, and insulin at the single cell resolution. The results of this elegant approach support a model of graded mTORC1 activation in response to the aforementioned stimuli when applied individually or in combination. This model is consistent with continuous adjustment of mTORC1 signaling to changes in cellular environment and opposed to the "on/off" model of mTORC1 function. Considering the pivotal role of mTORC1 in integrating signals such as nutrients, hormones, growth factors, oxygen, and energy status with a plethora of outputs that affect cell fate and organismal physiology, it was thought that this study will be of interests across a variety of biomedical disciplines. Overall, the elegance and robustness of the approach was highly appreciated, though the paper would be strengthened by addressing some technical issues and concerns regarding the positioning of the proposed model of mTORC1 regulation in the field.