EGF-induced activation of Akt results in mTOR-dependent p70S6 kinase phosphorylation and inhibition of HC11 cell lactogenic differentiation

Galbaugh, Traci; Cerrito, Maria Grazia; Jose, Cynthia C.; Cutler, Mary Lou

doi:10.1186/1471-2121-7-34

Cited by 56 publications

(32 citation statements)

References 71 publications

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“…To examine specificity of effects, normal mouse fibroblasts were cotransfected with the Stat3-independent luciferase reporters pLuc-SRE (23) or ␤-casein promoter-driven Luc (24) together with v-Src plasmid and treated with S3I-201 or without (0.05% DMSO). In contrast to the effect on the induction of pLucTKS3 luciferase reporter, v-Src-mediated induction of Stat3-independent pLucSRE (23) or the ␤-casein promoter-driven Luc (24) was not affected by treatment with S3I-201 ( Fig. 3 Center and Right).…”

Section: S3i-201 Does Not Interfere With Lck-sh2 Domain-phosphotyrosinementioning

confidence: 83%

Selective chemical probe inhibitor of Stat3, identified through structure-based virtual screening, induces antitumor activity

Siddiquee

Zhang

Guida

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

685

669

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P roteins of the STAT (signal transducer and activator of transcription) family are activated in response to cytokines and growth factors and promote proliferation, survival, and other biological processes (1-3). STATs are activated by phosphorylation of a critical tyrosine residue, which is mediated by growth factor receptor tyrosine kinases, Janus kinases, or the Src family kinases. Upon tyrosine phosphorylation, dimers of STATs formed between two phosphorylated monomers translocate to the nucleus, bind to specific DNA-response elements in the promoters of target genes, and induce gene expression. Aberrant activity of one of the family members, Stat3, contributes to carcinogenesis and tumor progression by up-regulating gene expression and promoting dysregulated growth, survival, and angiogenesis and modulating immune responses (2-9).As a critical step in STAT activation (10), the dimerization between two STAT monomers presents an attractive target to abolish Stat3 DNA-binding and transcriptional activity and to inhibit Stat3 biological functions (11, 12). Stat3 dimerization relies on the reciprocal binding of the SH2 domain of one monomer to the Pro-pTyr-Leu-Lys-Thr-Lys sequence of the other Stat3 monomer. To pursue the development of inhibitors of Stat3 signaling, key structural information gleaned from the x-ray crystal structure of the Stat3␤ homodimer (13) was used in the computational modeling and automated docking of small molecules into the SH2 domain of a Stat3 monomer, relative to the bound native pTyr peptide, to identify binders of the Stat3 SH2 domain, and potentially disruptors of Stat3⅐Stat3 dimers (14, 15).Structure-based high-throughput virtual screening of the National Cancer Institute (NCI) chemical libraries identified the high-scoring compound NSC 74859 (resynthesized as a pure sample and named S3I-201), which selectively inhibits Stat3 DNA-binding activity in vitro with an IC 50 value of 86 Ϯ 33 M. Furthermore, S3I-201 induces growth inhibition and apoptosis of malignant cells in part by constitutively inhibiting active Stat3 and induces human breast tumor regression in xenograft models. ResultsComputational Modeling and Virtual Screening. Our computational modeling and virtual screening study used the GLIDE (Grid-based Ligand Docking from Energetics) software (16, 17) (available from Schrödinger, Portland, OR) for the docking simulations and relied on the x-ray crystal structure of the Stat3␤ homodimer bound to DNA (13) determined at 2.25-Å resolution (1BG1 in the Protein Data Bank). For the virtual screening, DNA was removed and only one of the two monomers was used (see Fig. 1). To validate the docking approach, the native pTyr (pY) peptide, APpYLKT, was extracted from the crystal structure of one of the monomers and docked to the other monomer, whereby GLIDE produced a docking mode that closely resembled the x-ray crystal structure (data not shown). Three-dimensional structures of compounds from the NCI's chemical libraries were downloaded from the NCI Developmental Therapeutics Progra...

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Section: S3i-201 Does Not Interfere With Lck-sh2 Domain-phosphotyrosinementioning

confidence: 83%

Selective chemical probe inhibitor of Stat3, identified through structure-based virtual screening, induces antitumor activity

Siddiquee

Zhang

Guida

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

685

669

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“…Though mTOR regulates MEC growth in cell lines [ 8 , 9 ] and milk protein expression [ 8 , 10 – 12 ], mTOR-mediated regulation of mammary ductal morphogenesis remains under-investigated. The signaling complexity of mTOR, its pleiotropic functions, and a lack of mTORC2-specific inhibitors present a challenge to dissecting the relative roles of mTORC1 and mTORC2 in mammary development.…”

Section: Introductionmentioning

confidence: 99%

mTOR Directs Breast Morphogenesis through the PKC-alpha-Rac1 Signaling Axis

et al. 2015

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Akt phosphorylation is a major driver of cell survival, motility, and proliferation in development and disease, causing increased interest in upstream regulators of Akt like mTOR complex 2 (mTORC2). We used genetic disruption of Rictor to impair mTORC2 activity in mouse mammary epithelia, which decreased Akt phosphorylation, ductal length, secondary branching, cell motility, and cell survival. These effects were recapitulated with a pharmacological dual inhibitor of mTORC1/mTORC2, but not upon genetic disruption of mTORC1 function via Raptor deletion. Surprisingly, Akt re-activation was not sufficient to rescue cell survival or invasion, and modestly increased branching of mTORC2-impaired mammary epithelial cells (MECs) in culture and in vivo. However, another mTORC2 substrate, protein kinase C (PKC)-alpha, fully rescued mTORC2-impaired MEC branching, invasion, and survival, as well as branching morphogenesis in vivo. PKC-alpha-mediated signaling through the small GTPase Rac1 was necessary for mTORC2-dependent mammary epithelial development during puberty, revealing a novel role for Rictor/mTORC2 in MEC survival and motility during branching morphogenesis through a PKC-alpha/Rac1-dependent mechanism.

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“…In contrast, constitutive activation of mTORC1 can lead to uncontrolled cell growth and cancer (11). mTORC1 signaling is activated in response to growth-promoting hormones such as insulin (12), IGF-1 (13), or EGF (14). The signaling pathways through which these hormones act to increase mTOR signaling (e.g.…”

mentioning

confidence: 99%

Rapid Turnover of the mTOR Complex 1 (mTORC1) Repressor REDD1 and Activation of mTORC1 Signaling following Inhibition of Protein Synthesis

Kimball

Dang

Kutzler

et al. 2008

Journal of Biological Chemistry

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mTORC1 is a complex of proteins that includes the mammalian target of rapamycin (mTOR) and several regulatory proteins. It is activated by a variety of hormones (e.g. insulin) and nutrients (e.g. amino acids) that act to stimulate cell growth and proliferation and repressed by hormones (e.g. glucocorticoids) that act to reduce cell growth. Curiously, mTORC1 signaling is reported to be rapidly (e.g. within 1-2 h) activated by inhibitors of protein synthesis that act on either mRNA translation elongation or gene transcription. However, the basis for the mTORC1 activation has not been satisfactorily delineated. In the present study, mTORC1 signaling was found to be activated in response to inhibition of either the initiation or elongation phases of mRNA translation. Changes in mTORC1 signaling were inversely proportional to alterations in the expression of the mTORC1 repressor, REDD1, but not the expression of TRB3 or TSC2. Moreover the cycloheximide-induced increase in mTORC1 signaling was significantly attenuated in cells lacking REDD1, showing that REDD1 plays an integral role in the response. Finally, the half-life of REDD1 was estimated to be 5 min or less. Overall, the results are consistent with a model in which inhibition of protein synthesis leads to a loss of REDD1 protein because of its rapid degradation, and in part reduced REDD1 expression subsequently leads to de-repression of mTORC1 activity.

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EGF-induced activation of Akt results in mTOR-dependent p70S6 kinase phosphorylation and inhibition of HC11 cell lactogenic differentiation

Cited by 56 publications

References 71 publications

Selective chemical probe inhibitor of Stat3, identified through structure-based virtual screening, induces antitumor activity

Selective chemical probe inhibitor of Stat3, identified through structure-based virtual screening, induces antitumor activity

mTOR Directs Breast Morphogenesis through the PKC-alpha-Rac1 Signaling Axis

Rapid Turnover of the mTOR Complex 1 (mTORC1) Repressor REDD1 and Activation of mTORC1 Signaling following Inhibition of Protein Synthesis

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