PRAS40 Is a Functionally Critical Target for EWS Repression in Ewing Sarcoma

Huang, Lin; Nakai, Yuji; Kuwahara, Iku; Matsumoto, Ken

doi:10.1158/0008-5472.can-11-2254

Cited by 26 publications

(28 citation statements)

References 38 publications

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“…This triggers protein stabilization of the tumor suppressor p53, leading to cell cycle arrest, senescence, or apoptosis mediated by p53’s transcriptional targets. 3–6, 8, 46, 47 Because PRAS40 displays pro-survival 30, 34, 35 and pro-tumorigenic 29, 31 activity through an unknown mechanism, we hypothesized that PRAS40 negatively regulates p53 through association with RPL11 and inhibition of the RPL11-HDM2-p53 pathway. To explore this possibility, we depleted U2OS human osteosarcoma cells of PRAS40 using shRNAs targeted to various regions of the PRAS40 transcript.…”

Section: Resultsmentioning

confidence: 99%

“…29, 31 To clarify the tumorigenic function of PRAS40 we have interrogated its subcellular localization and interactome. Here we experimentally demonstrate that PRAS40 subcellular distribution is controlled at least in part by Crm1-dependent nuclear export directed by a NES sequence - 218 IAASMRALVL 227 .…”

Section: Discussionmentioning

confidence: 99%

“…25–28 However, in nearly all studies of PRAS40 in disease models, PRAS40 upregulation has been found to promote cell survival, tumorigenesis, or tumor progression. 29–31 Therefore, we hypothesize that phosphorylated, mTORC1-dissociated PRAS40 has its own pro-survival function, independent of mTORC1 inhibition. To explore this possibility we interrogated the subcellular localization and interactome of PRAS40.…”

Section: Introductionmentioning

confidence: 99%

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Nuclear PRAS40 couples the Akt/mTORC1 signaling axis to the RPL11-HDM2-p53 nucleolar stress response pathway

Havel

Cheng

et al. 2014

Oncogene

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The Ribosomal Protein (RP)-HDM2-p53 pathway has been shown to play key roles in oncogene-induced apoptosis and senescence, but the mechanism regulating this pathway remains elusive. The Proline-Rich Akt Substrate of 40 kDA (PRAS40) has recently been identified as a binding partner and inhibitor of the mechanistic Target of Rapamycin Complex 1 (mTORC1). Although other inhibitors of mTORC1 are known tumor suppressors, PRAS40 promotes cell survival and tumorigenesis. Here we demonstrate that Akt- and mTORC1-mediated phosphorylation of PRAS40 at T246 and S221, respectively, promotes nuclear-specific association of PRAS40 with Ribosomal Protein L11 (RPL11). Importantly, silencing of PRAS40 induces upregulation of p53 in a manner dependent upon RPL11. This effect is rescued by wild type PRAS40, but not by the RPL11 binding-null PRAS40 T246A mutant. We find that PRAS40 negatively regulates the RPL11-HDM2-p53 nucleolar stress response pathway and suppresses induction of p53-mediated cellular senescence. This work identifies nuclear PRAS40 as a dual-input signaling checkpoint that links cell growth and proliferation to inhibition of cellular senescence. These findings may help to explain the pro-tumorigenic effect of PRAS40 and identify the PRAS40-RPL11 complex as a promising target for p53-restorative anti-cancer drug discovery.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nuclear PRAS40 couples the Akt/mTORC1 signaling axis to the RPL11-HDM2-p53 nucleolar stress response pathway

Havel

Cheng

et al. 2014

Oncogene

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“…EWS has not previously been implicated in tumor suppression except that it has been shown to control cell proliferation via posttranscriptional regulation of the Akt substrate PRAS40. 53 Dysfunction of REST is evident in several cancers and is achieved through diverse mechanisms. In prostate cancer, loss of REST results in the derepression of IB1/JIP1 (Islet-Brain1/c-Jun amino-terminal kinase interacting protein 1) to prevent JNK activation and apoptosis.…”

Section: Discussionmentioning

confidence: 99%

EWS and RE1-Silencing Transcription Factor Inhibit Neuronal Phenotype Development and Oncogenic Transformation in Ewing Sarcoma

Sankar

Gomez²,

Bell

et al. 2013

Genes & Cancer

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The gene encoding EWS (EWSR1) is involved in various chromosomal translocations that cause the production of oncoproteins responsible for multiple cancers including Ewing sarcoma, myxoid liposarcoma, soft tissue clear cell sarcoma, and desmoplastic small round cell sarcoma. It is well known that EWS fuses to FLI to create EWS/FLI, which is the abnormal transcription factor that drives tumor development in Ewing sarcoma. However, the role of wildtype EWS in Ewing sarcoma pathogenesis remains unclear. In the current study, we identified EWS-regulated genes and cellular processes through RNA interference combined with RNA sequencing and functional annotation analyses. Interestingly, we found that EWS and EWS/FLI co-regulate a significant cluster of genes, indicating an interplay between the 2 proteins in regulating cellular functions. We found that among the EWS-down-regulated genes are a subset of neuronal genes that contain binding sites for the RE1-silencing transcription factor (REST or neuron-restrictive silencer factor [NRSF]), neuronrestrictive silencer element (NRSE), suggesting a cooperative interaction between REST and EWS in gene regulation. Co-immunoprecipitation analysis demonstrated that EWS interacts directly with REST. Genome-wide binding analysis showed that EWS binds chromatin at or near NRSE. Furthermore, functional studies revealed that both EWS and REST inhibit neuronal phenotype development and oncogenic transformation in Ewing sarcoma cells. Our data implicate an important role of EWS in the development of Ewing sarcoma phenotype and highlight a potential value in modulating EWS function in the treatment of Ewing sarcoma and other EWS translocation-based cancers.

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“…Downregulation of PRAS40 or inhibition of its upstream Akt3 decreases the anchorageindependent growth of cells in culture and tumor development in mice (51). Similar findings were reported in breast and lung cancer cells (52). Kazi et al showed that silencing PRAS40 reduced proliferation of C2C12 cells due to a cell cycle arrest in the G 1 phase (53).…”

Section: Discussionmentioning

confidence: 58%

PRAS40 Connects Microenvironmental Stress Signaling to Exosome-Mediated Secretion

Guo

Jayaprakash

Jian

et al. 2017

Molecular and Cellular Biology

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Secreted exosomes carrying lipids, proteins, and nucleic acids conduct cell-cell communications within the microenvironment of both physiological and pathological conditions. Exosome secretion is triggered by extracellular or intracellular stress signals. Little is known, however, about the signal transduction between stress cues and exosome secretion. To identify the linker protein, we took advantage of a unique finding in human keratinocytes. In these cells, although transforming growth factor alpha (TGF-␣) and epidermal growth factor (EGF) share the same EGF receptor and previously indistinguishable intracellular signaling networks, only TGF-␣ stimulation causes exosome-mediated secretion. However, deduction of EGF-activated pathways from TGF␣-activated pathways in the same cells allowed us to identify the proline-rich Akt substrate of 40 kDa (PRAS40) as the unique downstream effector of TGF-␣ but not EGF signaling via threonine 308-phosphorylated Akt. PRAS40 knockdown (KD) or PRAS40 dominant-negative (DN) mutant overexpression blocks not only TGF-␣-but also hypoxia-and H 2 O 2 -induced exosome secretion in a variety of normal and tumor cells. Site-directed mutagenesis and gene rescue studies show that Akt-mediated activation of PRAS40 via threonine 246 phosphorylation is both necessary and sufficient to cause exosome secretion without affecting the endoplasmic reticulum/Golgi pathway. Identification of PRAS40 as a linker protein paves the way for understanding how stress regulates exosome secretion under pathophysiological conditions.

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PRAS40 Is a Functionally Critical Target for EWS Repression in Ewing Sarcoma

Cited by 26 publications

References 38 publications

Nuclear PRAS40 couples the Akt/mTORC1 signaling axis to the RPL11-HDM2-p53 nucleolar stress response pathway

Nuclear PRAS40 couples the Akt/mTORC1 signaling axis to the RPL11-HDM2-p53 nucleolar stress response pathway

EWS and RE1-Silencing Transcription Factor Inhibit Neuronal Phenotype Development and Oncogenic Transformation in Ewing Sarcoma

PRAS40 Connects Microenvironmental Stress Signaling to Exosome-Mediated Secretion

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