Ribosomal protein S6 phosphorylation is a determinant of cell size and glucose homeostasis

Igor Ruvinsky, Nitzan Sharon, Tal Lerer, Hannah Cohen, Miri Stolovich-Rain, Tomer Nir, Yuval Dor, Philip Zisman, Oded Meyuhas*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

502 Scopus citations


The regulated phosphorylation of ribosomal protein (rp) S6 has attracted much attention since its discovery in 1974, yet its physiological role has remained obscure. To directly address this issue, we have established viable and fertile knock-in mice, whose rpS6 contains alanine substitutions at all five phosphorylatable serine residues (rpS6P-/-). Here we show that contrary to the widely accepted model, this mutation does not affect the translational control of TOP mRNAs. rpS6P-/- mouse embryo fibroblasts (MEFs) display an increased rate of protein synthesis and accelerated cell division, and they are significantly smaller than rpS6P+/+ MEFs. This small size reflects a growth defect, rather than a by-product of their faster cell division. Moreover, the size of rpS6P-/- MEFs, unlike wild-type MEFs, is not further decreased upon rapamycin treatment, implying that the rpS6 is a critical downstream effector of mTOR in regulation of cell size. The small cell phenotype is not confined to embryonal cells, as it also selectively characterizes pancreatic β-cells in adult rpS6P-/- mice. These mice suffer from diminished levels of pancreatic insulin, hypoinsulinemia, and impaired glucose tolerance.

Original languageAmerican English
Pages (from-to)2199-2211
Number of pages13
JournalGenes and Development
Issue number18
StatePublished - 15 Sep 2005


  • Cell size
  • Glucose intolerance
  • Hypoinsulinemia
  • Knock-in mouse
  • TOP mRNAs
  • Translational control


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