Fig. 3.

Rapamycin inhibits the mTOR pathway in the cichlid fish Astatotilapia burtoni. (A) Simplified diagram of the action of the mTOR inhibitor rapamycin (RAP) on the rapamycin-sensitive mTORC1 pathway. mTORC1 is composed of several proteins associated with mTOR: Rheb (Ras-homolog enriched in brain), Raptor (regulatory-associated protein of mTOR), Deptor (DEP-domain-containing mTOR-interacting protein), PRAS40 (proline-rich Akt 40 kDa substrate), and ml_ST8 (mammalian lethal with Sec13 protein 8; also known as GβL). The activated mTORC1 complex phosphorylates p70S6 kinase (asterisk), which phosphorylates the S6 ribosome to mediate functions such as protein synthesis and cell growth. RAP associated with FKBP12 (12 kDa FK506-binding protein) inhibits the mTORC1 complex. Quantification of phospho-p70S6 kinase is used as an indicator of downstream mTOR pathway activity. (B) Representative western blot of p-p70S6 kinase from whole brains of males given intraperitoneal injections of vehicle control or rapamycin (Rap) and collected at 24 and 48 hrs post treatment. Rap-injected animals show reduced expression of p-p70S6 kinase. Bands for the p-p70S6 and p-p85S6 isoforms detected by the antibody are shown.