Ribosomal protein S6 kinase beta-1

Ribosomal protein S6 kinase beta-1 (RPS6KB1) is a serine/threonine-protein kinase that acts downstream of mTOR signaling to promote cell proliferation, growth, and cycle progression (UniProt: P23443). It regulates protein synthesis by phosphorylating translation factors including EIF4B, RPS6, and EEF2K, and contributes to cell survival through phosphorylation of the pro-apoptotic protein BAD. The kinase also participates in feedback regulation of both mTORC1 and mTORC2 complexes and modulates insulin signaling through IRS1 phosphorylation.

RPS6KB1 is widely expressed and its functions span multiple metabolic pathways coordinating nutrient sensing with translational control and cell survival. In the context of mTOR pathway regulation, the protein plays a central role integrating growth factor and nutrient signals (UniProt: P23443).

In Alzheimer's disease, RPS6KB1 is significantly downregulated in post-mortem AD brain tissue compared to age-matched controls (Chaparral AD proteomics), with a mean log2 fold-change of −0.48 across subcellular fractions in TMT-labeled DDA proteomics. This downregulation may reflect impaired mTOR-mediated translational control and altered cell survival signaling in the AD brain.