TORC1 signaling inhibition by rapamycin and caffeine affect lifespan, global gene expression, and cell proliferation of fission yeast

Abstract

Target of rapamycin complex 1 (TORC1) is implicated in growth control and aging from yeast to humans. Fission yeast is emerging as a popular model organism to study TOR signaling, although rapamycin has been thought to not affect cell growth in this organism. Here, we analyzed the effects of rapamycin and caffeine, singly and combined, on multiple cellular processes in fission yeast. The two drugs led to diverse and specific phenotypes that depended on TORC1 inhibition, including prolonged chronological lifespan, inhibition of global translation, inhibition of cell growth and division, and reprograming of global gene expression mimicking nitrogen starvation. Rapamycin and caffeine differentially affected these various TORC1-dependent processes. Combined drug treatment augmented most phenotypes and effectively blocked cell growth. Rapamycin showed a much more subtle effect on global translation than did caffeine, while both drugs were effective in prolonging chronological lifespan. Rapamycin and caffeine did not affect the lifespan via the pH of the growth media. Rapamycin prolonged the lifespan of nongrowing cells only when applied during the growth phase but not when applied after cells had stopped proliferation. The doses of rapamycin and caffeine strongly correlated with growth inhibition and with lifespan extension. This comprehensive analysis will inform future studies into TORC1 function and cellular aging in fission yeast and beyond.

Artemisinin mimics calorie restriction to extend yeast lifespan via a dual-phase mode: a conclusion drawn from global transcriptome profiling

“…Therefore, it seems that MAPK may not be activated due to ROS deprival although the correlation of ROS levels with MAPK activity and MAPK gene expression is yet to be identified in yeast. On the other hand, it is accepted that protein kinases are implicated in yeast longevity [19,29,39,40], we actually observed the significant upregulation of Tor1 in PME yeast cells, which is as same as the case described in fission yeast [41]. It is unclear, however, whether the upregulation of Tor1 is due to the inhibition of Tor1p per se upon exposure of yeast cells to CR, ART, or H 2 O 2 .…”

Glucose Activates TORC2-Gad8 Protein via Positive Regulation of the cAMP/cAMP-dependent Protein Kinase A (PKA) Pathway and Negative Regulation of the Pmk1 Protein-Mitogen-activated Protein Kinase Pathway

“…Gad8 kinase activity or TORC2-dependent phosphorylation of Gad8 at Ser-546 was unchanged upon shift to media containing a poor nitrogen source (EMM-proline) or no nitrogen source (EMM-N). Rapamycin also had no effect on Gad8 activity or phosphorylation, consistent with the current notion that rapamycin specifically targets the TORC1 complex (34,36,37). In a remarkable contrast, a shift to a medium lacking glucose (EMM-G) abolished Gad8 activity or Gad8 Ser-546 phosphorylation (Fig.…”

Isp7 Is a Novel Regulator of Amino Acid Uptake in the TOR Signaling Pathway

“…Interestingly, TORC1 and TORC2 in S. pombe oppositely regulate starvation responses, including sexual development and transcription of nitrogen starvation-induced genes (25). Moreover, TORC1 and TORC2 play antagonistic roles with respect to mitosis (15) and longevity (32).…”

“…A triple deletion mutant of these kinases is viable (33), indicating that additional TORC1 downstream effectors are yet to be discovered. More recently, it was shown that rapamycin can inhibit TORC1 in the presence of caffeine, which potentially lowers the kinase activity of TORC1 and induces a nitrogen starvation-like response (32,34). Rapamycin inhibits sexual development and amino acid uptake (20,24,35) and following long exposure reduces the expression of nitrogen starvation-induced amino acid permeases (20).…”