scholarly journals Repurposing Potential of Riluzole as an ITAF Inhibitor in mTOR Therapy Resistant Glioblastoma

2020 ◽  
Vol 21 (1) ◽  
pp. 344 ◽  
Author(s):  
Angelica Benavides-Serrato ◽  
Jacquelyn T. Saunders ◽  
Brent Holmes ◽  
Robert N. Nishimura ◽  
Alan Lichtenstein ◽  
...  
Keyword(s):  
Rna Binding ◽  
Therapeutic Option ◽  
Mtor Inhibitors ◽  
Hnrnp A1 ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Docking Analysis ◽  
In Silico Docking ◽  
Effective Therapeutic Option

Internal ribosome entry site (IRES)-mediated protein synthesis has been demonstrated to play an important role in resistance to mechanistic target of rapamycin (mTOR) targeted therapies. Previously, we have demonstrated that the IRES trans-acting factor (ITAF), hnRNP A1 is required to promote IRES activity and small molecule inhibitors which bind specifically to this ITAF and curtail IRES activity, leading to mTOR inhibitor sensitivity. Here we report the identification of riluzole (Rilutek®), an FDA-approved drug for amyotrophic lateral sclerosis (ALS), via an in silico docking analysis of FDA-approved compounds, as an inhibitor of hnRNP A1. In a riluzole-bead coupled binding assay and in surface plasmon resonance imaging analyses, riluzole was found to directly bind to hnRNP A1 and inhibited IRES activity via effects on ITAF/RNA-binding. Riluzole also demonstrated synergistic anti-glioblastoma (GBM) affects with mTOR inhibitors in vitro and in GBM xenografts in mice. These data suggest that repurposing riluzole, used in conjunction with mTOR inhibitors, may serve as an effective therapeutic option in glioblastoma.

The Role of AKT and ERK in Regulating D-Cyclin Translation Inhibition and G1 Arrest in Multiple Myeloma Cells Treated with mTOR Inhibitors: Rationale for Combination Thereapy.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 4795-4795
Author(s):  
Patrick J. Frost ◽  
YiJiang Shi ◽  
Carolyne Bardalaban ◽  
Bao Hoang ◽  
Alan Lichtenstein
Keyword(s):  
Multiple Myeloma ◽  
Mtor Inhibitors ◽  
G1 Arrest ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Myeloma Cells ◽  
Transfected Cells ◽  
P38 Inhibitor

Abstract In a previous study, we showed that heightened AKT activity sensitized multiple myeloma (MM) cells to the in vivo anti-tumor effects of CCI-779. To test the mechanism of AKT’s regulatory role, we studied isogenic U266 MM cell lines transfected with an activated AKT allele or empty vector. The AKT-transfected cells were markedly more sensitive to cytostasis induced in vitro by rapamycin or in vivo by CCI-779. In contrast, cells with quiescent AKT were completely resistant. The ability of rapamycin and CCI-779 to inhibit D-cyclin expression was also significantly greater in AKT-transfected MM cells and this was, in part, due to a greater ability to curtail cap-independent translation and internal ribosome entry site (IRES) activity of D-cyclin transcripts. As ERK/p38 activity can facilitate IRES-mediated translation of some transcripts, we investigated ERK/p38 as regulators of rapamycin sensitivity. AKT-transfected cells demonstrated significantly decreased ERK and p38 activity, suggesting their involvement. However, only an ERK inhibitor prevented D-cyclin IRES activity in resistant “low AKT” myeloma cells while a p38 inhibitor had no effect. Furthermore, the combination of rapamycin and the ERK inhibitor successfully sensitized myeloma cells to rapamycin in terms of down regulated D-cyclin protein expression and G1 arrest. These data support a scenario where ERK facilitates D-cyclin IRES function and heightened AKT activity down regulates this ERK-dependent phenomenon. Thus ERK and AKT activity are potential predictors of responsiveness to mTOR inhibitors.

scholarly journals Cancer-associated mRNAs regulated by the Helix-Loop-Helix motif of human EIF3A

2018 ◽  
Author(s):  
Marina Volegova ◽  
Jamie H.D. Cate
Keyword(s):  
Translation Initiation ◽  
Rna Binding ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Binding Motif ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Helix Loop Helix ◽  
Small Set

AbstractImproper regulation of translation initiation, a vital check-point of protein synthesis in the cell, has been linked to a number of cancers. Overexpression of protein subunits of eukaryotic translation initiation factor 3 (eIF3) has been associated with increased translation of mRNAs involved in cell proliferation. In addition to playing a major role in general translation initiation by serving as a scaffold for the assembly of translation initiation complexes, eIF3 regulates translation of specific cellular mRNAs and viral RNAs. Mutations in the N-terminal Helix-Loop-Helix (HLH) RNA-binding motif of the EIF3A subunit in eIF3 interfere with Hepatitis C Virus Internal Ribosome Entry Site (IRES) mediated translation initiationin vitro. Here we show that the EIF3A HLH motif controls translation of a small set of cellular transcripts enriched in oncogenic mRNAs, includingMYC. We also demonstrate that the HLH motif of EIF3A acts specifically on the 5’-UTR ofMYCmRNA and modulates the function of EIF4A1 on select transcripts during translation initiation. In Ramos lymphoma cell lines, which are dependent on MYC overexpression, mutations in the HLH motif greatly reduce MYC expression, impede proliferation and sensitize cells to anti-cancer compounds. These results reveal the potential of the EIF3A HLH motif in eIF3 as a promising chemotherapeutic target.SummaryThe Helix Loop Helix motif of EIF3A controls translation of a small set of oncogenic cellular transcripts, includingMYC, and modulates the function of translation initiation factor EIF4A1 during translation initiation on select mRNAs.

scholarly journals Phosphomimetic Substitution of Heterogeneous Nuclear Ribonucleoprotein A1 at Serine 199 Abolishes AKT-dependent Internal Ribosome Entry Site-transacting Factor (ITAF) Function via Effects on Strand Annealing and Results in Mammalian Target of Rapamycin Complex 1 (mTORC1) Inhibitor Sensitivity

2011 ◽  
Vol 286 (18) ◽  
pp. 16402-16413 ◽  
Author(s):  
Jheralyn Martin ◽  
Janine Masri ◽  
Cheri Cloninger ◽  
Brent Holmes ◽  
Nicholas Artinian ◽  
...  
Keyword(s):  
Internal Ribosome Entry Site ◽  
Mammalian Target Of Rapamycin ◽  
Target Of Rapamycin ◽  
Hnrnp A1 ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Heterogeneous Nuclear Ribonucleoprotein ◽  
Nuclear Ribonucleoprotein ◽  
Mtor Complex 1

The relative activity of the AKT kinase has been demonstrated to be a major determinant of sensitivity of tumor cells to mammalian target of rapamycin (mTOR) complex 1 inhibitors. Our previous studies have shown that the multifunctional RNA-binding protein heterogeneous nuclear ribonucleoprotein (hnRNP) A1 regulates a salvage pathway facilitating internal ribosome entry site (IRES)-dependent mRNA translation of critical cellular determinants in an AKT-dependent manner following mTOR inhibitor exposure. This pathway functions by stimulating IRES-dependent translation in cells with relatively quiescent AKT, resulting in resistance to rapamycin. However, the pathway is repressed in cells with elevated AKT activity, rendering them sensitive to rapamycin-induced G1 arrest as a result of the inhibition of global eIF-4E-mediated translation. AKT phosphorylation of hnRNP A1 at serine 199 has been demonstrated to inhibit IRES-mediated translation initiation. Here we describe a phosphomimetic mutant of hnRNP A1 (S199E) that is capable of binding both the cyclin D1 and c-MYC IRES RNAs in vitro but lacks nucleic acid annealing activity, resulting in inhibition of IRES function in dicistronic mRNA reporter assays. Utilizing cells in which AKT is conditionally active, we demonstrate that overexpression of this mutant renders quiescent AKT-containing cells sensitive to rapamycin in vitro and in xenografts. We also demonstrate that activated AKT is strongly correlated with elevated Ser(P)199-hnRNP A1 levels in a panel of 22 glioblastomas. These data demonstrate that the phosphorylation status of hnRNP A1 serine 199 regulates the AKT-dependent sensitivity of cells to rapamycin and functionally links IRES-transacting factor annealing activity to cellular responses to mTOR complex 1 inhibition.

scholarly journals Subcellular Relocalization of a Trans-acting Factor Regulates XIAP IRES-dependent Translation

2007 ◽  
Vol 18 (4) ◽  
pp. 1302-1311 ◽  
Author(s):  
Stephen M. Lewis ◽  
Anne Veyrier ◽  
Nicoleta Hosszu Ungureanu ◽  
Sophie Bonnal ◽  
Stéphan Vagner ◽  
...  
Keyword(s):  
Osmotic Shock ◽  
Cellular Stress ◽  
Critical Role ◽  
Negative Regulator ◽  
Hnrnp A1 ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Xiap Expression

Translation of the X-linked inhibitor of apoptosis (XIAP) proceeds by internal ribosome entry site (IRES)-mediated initiation, a process that is physiologically important because XIAP expression is essential for cell survival under conditions of compromised cap-dependent translation, such as cellular stress. The regulation of internal initiation requires the interaction of IRES trans-acting factors (ITAFs) with the IRES element. We used RNA-affinity chromatography to identify XIAP ITAFs and isolated the heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1). We find that hnRNP A1 interacts with XIAP IRES RNA both in vitro and in vivo and that hnRNP A1 negatively regulates XIAP IRES activity. Moreover, XIAP IRES-dependent translation is significantly reduced when hnRNP A1 accumulates in the cytoplasm. Osmotic shock, a cellular stress that causes cytoplasmic accumulation of hnRNP A1, also leads to a decrease in XIAP levels that is abrogated by knockdown of hnRNP A1 expression. These results suggest that the subcellular localization of hnRNP A1 is an important determinant of its ability to negatively regulate XIAP IRES activity, suggesting that the subcellular distribution of ITAFs plays a critical role in regulating IRES-dependent translation. Our findings demonstrate that cytoplasmic hnRNP A1 is a negative regulator of XIAP IRES-dependent translation, indicating a novel function for the cytoplasmic form of this protein.

scholarly journals Akt-Mediated YB-1 Phosphorylation Activates Translation of Silent mRNA Species

2006 ◽  
Vol 26 (1) ◽  
pp. 277-292 ◽  
Author(s):  
Valentina Evdokimova ◽  
Peter Ruzanov ◽  
Michael S. Anglesio ◽  
Alexey V. Sorokin ◽  
Lev P. Ovchinnikov ◽  
...  
Keyword(s):  
Rna Binding ◽  
Mrna Transcription ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Affymetrix Microarrays ◽  
Messenger Ribonucleoprotein ◽  
Protein Kinase Akt ◽  
Related Proteins ◽  
Reporter Mrna

ABSTRACT YB-1 is a broad-specificity RNA-binding protein that is involved in regulation of mRNA transcription, splicing, translation, and stability. In both germinal and somatic cells, YB-1 and related proteins are major components of translationally inactive messenger ribonucleoprotein particles (mRNPs) and are mainly responsible for storage of mRNAs in a silent state. However, mechanisms regulating the repressor activity of YB-1 are not well understood. Here we demonstrate that association of YB-1 with the capped 5′ terminus of the mRNA is regulated via phosphorylation by the serine/threonine protein kinase Akt. In contrast to its nonphosphorylated form, phosphorylated YB-1 fails to inhibit cap-dependent but not internal ribosome entry site-dependent translation of a reporter mRNA in vitro. We also show that similar to YB-1, Akt is associated with inactive mRNPs and that activated Akt may relieve translational repression of the YB-1-bound mRNAs. Using Affymetrix microarrays, we found that many of the YB-1-associated messages encode stress- and growth-related proteins, raising the intriguing possibility that Akt-mediated YB-1 phosphorylation could, in part, increase production of proteins regulating cell proliferation, oncogenic transformation, and stress response.

scholarly journals RBMX suppresses tumorigenicity and progression of bladder cancer by interacting with the hnRNP A1 protein to regulate PKM alternative splicing

Oncogene ◽  
2021 ◽  
Author(s):  
Qiuxia Yan ◽  
Peng Zeng ◽  
Xiuqin Zhou ◽  
Xiaoying Zhao ◽  
Runqiang Chen ◽  
...  
Keyword(s):  
Bladder Cancer ◽  
Alternative Splicing ◽  
Rna Binding ◽  
Aerobic Glycolysis ◽  
Histological Grade ◽  
Migration And Invasion ◽  
Binding Motif ◽  
Hnrnp A1

AbstractThe prognosis for patients with metastatic bladder cancer (BCa) is poor, and it is not improved by current treatments. RNA-binding motif protein X-linked (RBMX) are involved in the regulation of the malignant progression of various tumors. However, the role of RBMX in BCa tumorigenicity and progression remains unclear. In this study, we found that RBMX was significantly downregulated in BCa tissues, especially in muscle-invasive BCa tissues. RBMX expression was negatively correlated with tumor stage, histological grade and poor patient prognosis. Functional assays demonstrated that RBMX inhibited BCa cell proliferation, colony formation, migration, and invasion in vitro and suppressed tumor growth and metastasis in vivo. Mechanistic investigations revealed that hnRNP A1 was an RBMX-binding protein. RBMX competitively inhibited the combination of the RGG motif in hnRNP A1 and the sequences flanking PKM exon 9, leading to the formation of lower PKM2 and higher PKM1 levels, which attenuated the tumorigenicity and progression of BCa. Moreover, RBMX inhibited aerobic glycolysis through hnRNP A1-dependent PKM alternative splicing and counteracted the PKM2 overexpression-induced aggressive phenotype of the BCa cells. In conclusion, our findings indicate that RBMX suppresses BCa tumorigenicity and progression via an hnRNP A1-mediated PKM alternative splicing mechanism. RBMX may serve as a novel prognostic biomarker for clinical intervention in BCa.

scholarly journals In vitro toxicity and in silico docking analysis of two novel selective AH-receptor modulators

2018 ◽  
Vol 52 ◽  
pp. 178-188 ◽  
Author(s):  
Selma Mahiout ◽  
Sara Giani Tagliabue ◽  
Atefeh Nasri ◽  
Iyekhoetin Matthew Omoruyi ◽  
Lars Pettersson ◽  
...  
Keyword(s):  
In Silico ◽  
In Vitro Toxicity ◽  
Ah Receptor ◽  
Docking Analysis ◽  
In Silico Docking ◽  
Receptor Modulators
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