The Mammalian Target of Rapamycin (mTOR) Partner, Raptor, Binds the mTOR Substrates p70 S6 Kinase and 4E-BP1 through Their TOR Signaling (TOS) Motif

Hiroki Nojima,Chiharu Tokunaga,Satoshi Eguchi,Noriko Oshiro,Sujuti Hidayat,Ken-Ichi Yoshino,Kenta Hara,Noriaki Tanaka,Joseph Avruch,Kazuyoshi Yonezawa

doi:10.1074/jbc.c200665200

Abstract

The mammalian target of rapamycin (mTOR) controls multiple cellular functions in response to amino acids and growth factors, in part by regulating the phosphorylation of p70 S6 kinase (p70S6k) and eukaryotic initiation factor 4E-binding protein 1 (4E-BP1). Raptor (regulatory associated protein of mTOR) is a recently identified mTOR binding partner that also binds p70S6k and 4E-BP1 and is essential for TOR signaling in vivo. Herein we demonstrate that raptor binds to p70S6k and 4E-BP1 through their respective TOS (conserved TOR signaling) motifs to be required for amino acid- and mTOR-dependent regulation of these mTOR substrates in vivo. A point mutation of the TOS motif also eliminates all in vitro mTOR-catalyzed 4E-BP1 phosphorylation and abolishes the raptor-dependent component of mTOR-catalyzed p70S6k phosphorylation in vitro. Raptor appears to serve as an mTOR scaffold protein, the binding of which to the TOS motif of mTOR substrates is necessary for effective mTOR-catalyzed phosphorylation in vivo and perhaps for conferring their sensitivity to rapamycin and amino acid sufficiency.

Highlights

From the ‡Biosignal Research Center, Kobe University, Kobe 657-8501, Japan, ¶CREST, Japan Science and Technology Corporation, the §Department of Gastroenterological Surgery, Transplant, and Surgical Oncology, Okayama University Graduate School of Medicine and Dentistry, Okayama, 700-0914, Japan, and the ʈDepartment of Molecular Biology and the Diabetes Unit, Medical Services, Massachusetts General Hospital and the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114
We demonstrate that raptor binds to p70 S6 kinase (p70S6k) and 4E-binding protein 1 (4E-BP1) through their respective TOS motifs to be required for amino acid- and mammalian target of rapamycin (mTOR)-dependent regulation of these mTOR substrates in vivo
Raptor appears to serve as an mTOR scaffold protein, the binding of which to the TOS motif of mTOR substrates is necessary for effective mTOR-catalyzed phosphorylation in vivo and perhaps for conferring their sensitivity to rapamycin and amino acid sufficiency

Summary

Accelerated Publication

The Mammalian Target of Rapamycin (mTOR) Partner, Raptor, Binds the mTOR Substrates p70 S6 Kinase and 4E-BP1 through Their TOR Signaling (TOS) Motif*. The mammalian target of rapamycin (mTOR) controls multiple cellular functions in response to amino acids and growth factors, in part by regulating the phosphorylation of p70 S6 kinase (p70S6k) and eukaryotic initiation factor 4E-binding protein 1 (4E-BP1). We demonstrate that raptor binds to p70S6k and 4E-BP1 through their respective TOS (conserved TOR signaling) motifs to be required for amino acid- and mTOR-dependent regulation of these mTOR substrates in vivo. Raptor appears to serve as an mTOR scaffold protein, the binding of which to the TOS motif of mTOR substrates is necessary for effective mTOR-catalyzed phosphorylation in vivo and perhaps for conferring their sensitivity to rapamycin and amino acid sufficiency. Raptor Binds to the TOS Motif suggest that the binding of these mTOR substrates to raptor may be necessary for their sensitivity to regulation by amino acids and rapamycin

EXPERIMENTAL PROCEDURES

RESULTS AND DISCUSSION

Additions and Corrections