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PMID: 16914728 Published · ppublish English Journal Article Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't

Turnover of the active fraction of IRS1 involves raptor-mTOR- and S6K1-dependent serine phosphorylation in cell culture models of tuberous sclerosis.

Molecular and cellular biology ·Vol. 26 ·No. 17 ·2006-09-00 ·Pages 6425-34

Shah OJ, Hunter T

Abstract

The TSC1-TSC2/Rheb/Raptor-mTOR/S6K1 cell growth cassette has recently been shown to regulate cell autonomous insulin and insulin-like growth factor I (IGF-I) sensitivity by transducing a negative feedback signal that targets insulin receptor substrates 1 and 2 (IRS1 and -2). Using two cell culture models of the familial hamartoma syndrome, tuberous sclerosis, we show here that Raptor-mTOR and S6K1 are required for phosphorylation of IRS1 at a subset of serine residues frequently associated with insulin resistance, including S307, S312, S527, S616, and S636 (of human IRS1). Using loss- and gain-of-function S6K1 constructs, we demonstrate a requirement for the catalytic activity of S6K1 in both direct and indirect regulation of IRS1 serine phosphorylation. S6K1 phosphorylates IRS1 in vitro on multiple residues showing strong preference for RXRXXS/T over S/T,P sites. IRS1 is preferentially depleted from the high-speed pellet fraction in TSC1/2-deficient mouse embryo fibroblasts or in HEK293/293T cells overexpressing Rheb. These studies suggest that, through serine phosphorylation, Raptor-mTOR and S6K1 cell autonomously promote the depletion of IRS1 from specific intracellular pools in pathological states of insulin and IGF-I resistance and thus potentially in lesions associated with tuberous sclerosis.

MeSH Terms
Adaptor Proteins, Signal Transducing Animals Cell Culture Techniques Cells, Cultured Humans Insulin Receptor Substrate Proteins Mice Monomeric GTP-Binding Proteins/metabolism Neuropeptides/metabolism Phosphoproteins/deficiency,metabolism Phosphoserine/metabolism Protein Kinases/metabolism Proteins/metabolism Ras Homolog Enriched in Brain Protein Regulatory-Associated Protein of mTOR Ribosomal Protein S6 Kinases/metabolism Subcellular Fractions TOR Serine-Threonine Kinases Tuberous Sclerosis/pathology Tuberous Sclerosis Complex 1 Protein Tuberous Sclerosis Complex 2 Protein Tumor Suppressor Proteins/deficiency
Chemicals
Adaptor Proteins, Signal Transducing IRS1 protein, human Insulin Receptor Substrate Proteins Irs1 protein, mouse Neuropeptides Phosphoproteins Proteins RHEB protein, human RPTOR protein, human Ras Homolog Enriched in Brain Protein Regulatory-Associated Protein of mTOR TSC1 protein, human TSC2 protein, human Tsc1 protein, mouse Tsc2 protein, mouse Tuberous Sclerosis Complex 1 Protein Tuberous Sclerosis Complex 2 Protein Tumor Suppressor Proteins Phosphoserine Protein Kinases MTOR protein, human mTOR protein, mouse Ribosomal Protein S6 Kinases TOR Serine-Threonine Kinases Monomeric GTP-Binding Proteins
Authors & Affiliations
2 authors, click to expand affiliations / ORCID
Shah O Jameel
Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
Hunter Tony
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Article Info
Journal
Molecular and cellular biology
Abbr.
Mol Cell Biol
ISSN
0270-7306
DOI
10.1128/MCB.01254-05
Published
2006-09-00
Pages
6425-34
Language
English
Region
United States
NLM ID
8109087
PMCID
PMC1592824
Subset
IM
Grants
NCI NIH HHS · R01 CA082683 · United States
NCI NIH HHS · CA82683 · United States
NIGMS NIH HHS · GM67407 · United States
NCI NIH HHS · CA14195 · United States
NCI NIH HHS · T32-CA09523 · United States
NIGMS NIH HHS · F32 GM067407 · United States
NCI NIH HHS · T32 CA009523 · United States
NCI NIH HHS · P30 CA014195 · United States
External Links
PubMed source DOI: 10.1128/MCB.01254-05 PMC Full Text View journal details
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