Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 1995 Feb 3;270(5):2320-6.
doi: 10.1074/jbc.270.5.2320.

Phosphorylation of ribosomal protein S6 is inhibitory for autophagy in isolated rat hepatocytes

E F Blommaart  1 , J J Luiken, P J Blommaart, G M van Woerkom, A J Meijer
Affiliations
Free article

Phosphorylation of ribosomal protein S6 is inhibitory for autophagy in isolated rat hepatocytes

E F Blommaart et al. J Biol Chem. .
Free article

Abstract

In rat hepatocytes, autophagy is known to be inhibited by amino acids. Insulin and cell swelling promote inhibition by amino acids. Each of the conditions leading to inhibition of autophagic proteolysis was found to be associated with phosphorylation of a 31-kDa protein that we identified as ribosomal protein S6. A combination of leucine, tyrosine, and phenylalanine, which efficiently inhibits autophagic proteolysis, was particularly effective in stimulating S6 phosphorylation. The relationship between the percentage inhibition of proteolysis and the degree of S6 phosphorylation was linear. Thus, inhibition of autophagy and phosphorylation of S6 are under the control of the same signal transduction pathway. Stimulation of S6 phosphorylation by the presence of amino acids was due to activation of S6 kinase and not to inhibition of S6 phosphatase. The inhibition by amino acids of both autophagic proteolysis and autophagic sequestration of electro-injected cytosolic [14C]sucrose was partially prevented by rapamycin, a compound known to inhibit activation of p70 S6 kinase. In addition, rapamycin partially inhibited the rate of protein synthesis. We conclude that the fluxes through the autophagic and protein synthetic pathways are regulated in an opposite manner by the degree to which S6 is phosphorylated. Possible mechanisms by which S6 phosphorylation can cause inhibition of autophagy are discussed.

PubMed Disclaimer

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

Publication types

LinkOut - more resources

-