Anti-RPS6 (phospho S235 + S236) Antibody

Phosphorylation of ribosomal protein S6 at serine residues 235 and 236 is uniquely positioned at the intersection of two major kinase cascades. While S6K1 and S6K2 downstream of mTORC1 target all five C-terminal phospho-sites of RPS6, the p90 RSK family, activated through the MAPK/ERK pathway, phosphorylates only Ser235 and Ser236, a distinction confirmed in S6K1/S6K2 double-knockout MEFs where Ser240/244 phosphorylation is lost but Ser235/236 persists. This rabbit polyclonal IgG reagent, raised against a doubly phosphorylated RPS6 peptide, recognizes the dual-phosphorylated epitope and is supplied by Antibodies.com as a 50 µl unconjugated aliquot for Western blot detection of endogenous human RPS6 at the predicted 29 kDa band. Because S235/S236 can be driven independently by either mTOR/S6K or ERK/RSK inputs, the reagent is widely used as a phospho-readout in studies of growth factor, mitogen, and oncogenic Ras signaling. Investigators monitoring nutrient stress, serum re-stimulation after starvation, or pharmacological mTOR inhibition (rapamycin or active-site TOR inhibitors) routinely apply this reagent to lysates from HeLa, HEK-293, MCF-7, and other human cell lines, often pairing it with phospho-p70 S6K (Thr389) and total RPS6 antibodies to confirm pathway-specific engagement. The unconjugated format permits flexible pairing with HRP- or fluorophore-conjugated anti-rabbit secondaries, and aliquoting upon arrival with storage at -20 °C is recommended to preserve phospho-specific reactivity across repeated freeze-thaw cycles.