Rapamycin induces dephosphorylation/inactivation of the 70 kDa S6 kinase, defining an early readout of TOR signalling.
| Evidence tier | D Mechanistic / in vitro / review |
| Study type | 5 - Mechanistic / In Vitro |
| Model system | Mammalian cells; in vitro |
| Journal | Science |
| Year | 1992 |
| Peer reviewed | Yes |
| Source | DOI 10.1126/science.1380182 · PMID 1380182 |
The immunosuppressant rapamycin inhibited proliferation of the H4IIEC hepatoma cell line. Rapamycin, but not its structural analog FK506, also inhibited the basal and insulin-stimulated activity of the p70 ribosomal protein S6 kinase. By contrast, insulin stimulation of the p85 Rsk S6 kinase and mitogen-activated protein (MAP) kinase activity were unaffected by drug. Rapamycin treatment of COS cells transfected with recombinant p70 S6 kinase completely inhibited the appearance of the hyperphosphorylated form of p70 S6 kinase concomitant with the inhibition of enzyme activity toward 40S subunits. Thus, rapamycin inhibits a signal transduction element that is necessary for the activation of p70 S6 kinase and mitogenesis but unnecessary for activation of p85 Rsk S6 kinase or MAP kinase.
| Intervention | Rapamycin (vs FK506) |
| Target | p70 S6 kinase |
| Model | Mammalian cells; in vitro |
| Effect | Rapamycin (not FK506) inhibits basal and insulin-stimulated p70 S6 kinase activity |