Mechanistic target of rapamycin-Ribosomal protein S6 signaling axis (mTOR-S6 axis)

The mTOR-S6 signaling axis is a central regulatory pathway downstream of the mechanistic target of rapamycin complex 1 (mTORC1) that coordinates protein synthesis, cell growth, and metabolic homeostasis in response to environmental cues [1.3.1, 1.3.4]. Within this axis, mTORC1 phosphorylates and activates ribosomal protein S6 kinase 1 (S6K1), which subsequently phosphorylates the 40S ribosomal protein S6, a key component of the translation machinery [1.1.1, 1.3.3]. This cascade is essential for the translation of mRNAs containing 5' terminal oligopyrimidine (TOP) motifs, which primarily encode ribosomal proteins and elongation factors [1.1.1, 1.3.4]. Dysregulation of the mTOR-S6 axis is frequently observed in various cancers, where it promotes aberrant cell proliferation, survival, and angiogenesis [1.2.2, 1.4.1]. Additionally, the axis is implicated in metabolic diseases such as type 2 diabetes and obesity, often through a negative feedback loop where S6K1 phosphorylates insulin receptor substrate 1 (IRS-1) to attenuate insulin signaling [1.1.4, 1.4.3]. Therapeutic strategies targeting this axis include allosteric mTOR inhibitors like rapamycin (sirolimus) and its analogs, as well as second-generation ATP-competitive mTOR kinase inhibitors and selective S6K1 inhibitors [1.1.3, 1.4.4]. The phosphorylation status of ribosomal protein S6 (p-S6) is widely utilized as a pharmacodynamic biomarker to monitor the efficacy of these treatments in clinical and preclinical settings [1.1.1, 1.2.2].

Other names

mTOR-S6K1-S6 pathwaymTORC1-S6K1-S6 axismTOR-S6 signaling pathwaymTOR-S6K axisAKT-mTOR-S6 signaling axis

Inhibition of the mTOR kinase complex or its downstream effector S6K1 to prevent the phosphorylation of ribosomal protein S6, thereby suppressing the translation of specific mRNAs required for cell growth and proliferation.