Ahmed M. Osman and Henk van Loveren
We report here that tributyltin oxide (TBTO) inhibits, like rapamycin, the p70S6k1 pathway, though by a different mechanism in EL4 cell line. Both TBTO and rapamycin downregulated the phosphorylation state of S6k1 assessed at Ser421/Thr424, but in contrast to rapamycin, TBTO decreased the total S6k1 protein. In addition, TBTO reduced the levels of RPS6 (Ser236) and eIF4B (Ser422), downstream substrates of S6k1. Further, TBTO and rapamycin differentially affected 4E-binding protein 1, a repressor of the cap-binding protein eIF4E.