Suppression of the mTOR-Raptor Signaling Pathway by the Inhibitor of Heat Shock Protein 90 Geldanamycin

Ohji, Goh; Sujuti, Hidayat; Nakashima, Akio; Tokunaga, Chiharu; Oshiro, Noriko; Yoshino, Ken‐ichi; Yokono, Koichi; Kikkawa, Ushio; Yonezawa, Kazuyoshi

doi:10.1093/jb/mvj008

Cited by 45 publications

(47 citation statements)

References 38 publications

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“…Whereas the interaction between Tel2 and Tti1, Tti2, and Reptin was not affected, the binding of ATM, mTOR, ATR, and DNA-PKcs was diminished by Hsp90 inhibition. Consistent with this finding, our previous data indicated that prolonged (16-24 h) treatment with 17-AAG substantially diminished the levels of ATM and DNA-PKcs and had a minor effect on mTOR (Takai et al 2007), and an inhibitory effect of geldanamycin on mTOR activation has been reported (Ohji et al 2006).…”

Section: Inhibition Of Hsp90 Affects Binding Of Tel2 To Atm Atr Mtosupporting

confidence: 83%

Tel2 structure and function in the Hsp90-dependent maturation of mTOR and ATR complexes

Takai

Xie²,

Lange³

et al. 2010

Genes Dev.

176

267

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We reported previously that the stability of all mammalian phosphatidylinositol 3-kinase-related protein kinases (PIKKs) depends on their interaction with Tel2, the ortholog of yeast Tel2 and Caenorhabditis elegans Clk-2. Here we provide evidence that Tel2 acts with Hsp90 in the maturation of PIKK complexes. Quantitative immunoblotting showed that the abundance of Tel2 is low compared with the PIKKs, and Tel2 preferentially bound newly synthesized ATM, ATR, mTOR, and DNA-PKcs. Tel2 complexes contained, in addition to Tti1-Tti2, the Hsp90 chaperone, and inhibition of Hsp90 interfered with the interaction of Tel2 with the PIKKs. Analysis of in vivo labeled nascent protein complexes showed that Tel2 and Hsp90 mediate the formation of the mTOR TORC1 and TORC2 complexes and the association of ATR with ATRIP. The structure of yeast Tel2, reported here, shows that Tel2 consists of HEAT-like helical repeats that assemble into two separate a-solenoids. Through mutagenesis, we identify a surface patch of conserved residues involved in binding to the Tti1-Tti2 complex in vitro. In vivo, mutation of this conserved patch affects cell growth, levels of PIKKs, and ATM/ATR-mediated checkpoint signaling, highlighting the importance of Tti1-Tti2 binding to the function of Tel2. Taken together, our data suggest that the Tel2-Tti1-Tti2 complex is a PIKK-specific cochaperone for Hsp90.[Keywords: Tel2; Hsp90; ATR; mTOR; PIKK; structure] Supplemental material is available at http://www.genesdev.org.

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Section: Inhibition Of Hsp90 Affects Binding Of Tel2 To Atm Atr Mtosupporting

confidence: 83%

Tel2 structure and function in the Hsp90-dependent maturation of mTOR and ATR complexes

Takai

Xie²,

Lange³

et al. 2010

Genes Dev.

176

267

View full text Add to dashboard Cite

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“…However, there was no detectable loss (degradation) of any of the MRN components nor did 17DMAG disrupt the complex. Ohji et al (46) reported that raptor is an Hsp90 client, and although inhibition of Hsp90 does not result in raptor degradation, it does suppress raptor-mammalian target of rapamycin signaling. Similarly, the activity of the MRN complex may require a stabilizing interaction with Hsp90.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of Hsp90 Compromises the DNA Damage Response to Radiation

et al. 2006

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Inhibitors of the molecular chaperone Hsp90 have been shown to enhance tumor cell radiosensitivity. To begin to address the mechanism responsible, we have determined the effect of the Hsp90 inhibitor 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17DMAG) on the DNA damage response to radiation. Exposure of MiaPaCa tumor cells to 17DMAG, which results in radiosensitization, inhibited the repair of DNA double-strand breaks according to ;H2AX foci dispersal and the neutral comet assay. This repair inhibition was associated with reduced DNA-PK catalytic subunit (DNA-PKcs) phosphorylation after irradiation and a disruption of DNA-PKcs/ ErbB1 interaction. These data suggest that the previously established 17DMAG-mediated reduction in ErbB1 activity reduces its interaction with DNA-PKcs and thus accounts for the attenuation of radiation-induced DNA-PK activation. 17DMAG was also found to abrogate the activation of the G 2 -and S-phase cell cycle checkpoints. Associated with these events was a reduction in radiation-induced ataxia-telangiectasia mutated (ATM) activation and foci formation in 17DMAG-treated cells. Although no interaction between ATM and Hsp90 was detected, Hsp90 was found to interact with the MRE11/Rad50/NBS1 (MRN) complex. 17DMAG exposure reduced the ability of the MRN components to form nuclear foci after irradiation. Moreover, 17DMAG exposure reduced the interaction between NBS1 and ATM, although no degradation of the MRN complex was detected. These results suggest that the diminished radiation-induced activation of ATM in 17DMAG-treated cells was the result of a compromise in the function of the MRN complex. These data indicate that Hsp90 can contribute to the DNA damage response to radiation affecting both DNA repair and cell cycle checkpoint activation. (Cancer Res 2006; 66(18): 9211-20)

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“…Hsp90 binds to raptor in mammalian cells and positively regulates S6K activity. Geldanamycin, an Hsp90 inhibitor in clinical trials for cancer treatment, suppressed binding of raptor to Hsp90 and reduced S6K phosphorylation (Ohji et al, 2006). Some years ago, the Blenis group found that heat shock unexpectedly increased phosphorylation of S6K1 in fibroblasts (Jurivich et al, 1991), a finding also made by another group (Lin et al, 1997).…”

Section: Heat Shockmentioning

confidence: 95%