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Chakraborty S, Mukherjee S, Biswas P, Ghosh A, Siddhanta A. FRB domain of human TOR protein induces compromised proliferation and mitochondrial dysfunction in Labrus donovani promastigotes. Parasitol Int 2022; 89:102591. [PMID: 35472440 DOI: 10.1016/j.parint.2022.102591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 04/14/2022] [Accepted: 04/19/2022] [Indexed: 11/26/2022]
Abstract
Visceral leishmaniasis (VL) or Kala-azar, the second-largest parasitic killer worldwide, is caused by Leishmania donovani. The drugs to treat VL are toxic and expensive. Moreover, their indiscriminate use gave rise to resistant strains. The high rate of parasite proliferation within the host macrophage cells causes pathogenesis. In the proliferative pathway, FRB domain of TOR protein is ubiquitously essential. Although orthologues of mTOR protein are reported in trypanosomatids and Leishmania but therein depth molecular characterization is yet to be done. Considerable protein sequence homology exists between the TOR of kinetoplastidas and mammals. Interestingly, exogenous human FRB domain was shown to block G1 to S transition in mammalian cancer cells. Thus, we hypothesized that expression of human FRB domain would inhibit the proliferation of Labrus donovani. Indeed, promastigotes stably expressing wild type human FRB domain show 4.7 and 1.5 folds less intra- and extra-cellular proliferations than that of untransfected controls. They also manifested 2.65 times lower rate of glucose stimulated oxygen consumption. The activities of all respiratory complexes were compromised in the hFRB expressing promastigotes. In these cells, depolarized mitochondria were 2-fold more than control cells. However, promastigotes expressing its mutant version (Trp2027-Phe) has shown similar characteristics like untransfected cells. Thus, this study reveals greater insights on the conserved role of TOR in the regulation of the respiratory complexes in L. donovani. The slow growing variant of FRB expressing promastigotes will have great potential to be exploited as a prophylactic agent against leishmaniasis.
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Affiliation(s)
- Sudipta Chakraborty
- Department of Biochemistry, University of Calcutta, India; Department of Microbiology, Bidhannagar College, Kolkata, India
| | | | - Priyam Biswas
- Department of Biochemistry, University of Calcutta, India
| | - Alok Ghosh
- Department of Biochemistry, University of Calcutta, India
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He B, Bai J, Wu Z. Glucosamine enhances proliferation, barrier, and anti-oxidative functions in porcine trophectoderm cells. Food Funct 2022; 13:4551-4561. [PMID: 35352734 DOI: 10.1039/d1fo04086c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Trophectoderm (TE) is the first epithelium that appears during mammalian embryogenesis, and is a polarized transporting single cell layer that comprises the wall of the blastocyst. Previous studies have revealed the functional roles of glucose (Gluc), fructose (Fruc), and glutamine (Gln), which play a positive role in porcine trophectoderm (pTr) cell proliferation and migration, suggesting the importance of nutrients for normal development of the conceptus and implantation. This work was conducted to test the hypothesis that glucosamine (GlcN), which is synthesized from Gln and Fruc-6-phosphate through the hexosamine biosynthesis pathway (HBP), can stimulate proliferation and sustain the barrier and anti-oxidative functions of pTr cells. Cells were treated with 0, 0.25, or 0.5 mmol L-1 GlcN in the presence or absence of adiquat (DQ) for the indicated time points. The results showed that 0.25 or 0.5 mmol L-1 GlcN stimulated pTr cell viability and DNA replication compared to the control group. The addition of 0.25 mmol L-1 GlcN enhanced the phosphorylation of mTOR signaling proteins, which can be inhibited by the inhibitor of phosphatidylinositol 3-kinase (PI3K), LY294002. Transepithelial electrical resistance (TEER) was increased, and paracellular permeability was correspondingly reduced in GlcN treatment. GlcN attenuated DQ-induced cell death and reduced the level of reactive oxygen species (ROS). The decreased TEER values and increased paracellular permeability caused by DQ treatment were also inhibited by GlcN treatment. The addition of 0.5 mmol L-1 GlcN increased the protein expression of zonula occludens-3 (ZO-3), claudin-3, and claudin-4 in pTr cells, while inhibited the downregulation protein of claudin-1 and claudin-3 brought about by oxidative stress. Collectively, GlcN plays an important role in promoting proliferation and stimulating the mTOR cell signaling pathway, as well as ameliorating oxidative stress and augmenting barrier functions in pTr cells.
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Affiliation(s)
- Beibei He
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China 100193.
| | - Jun Bai
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China 100193.
| | - Zhenlong Wu
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China 100193.
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Expression of phosphorylated ribosomal protein S6 in mesothelioma patients - correlation with clinico-pathological characteristics and outcome: results from the European Thoracic Oncology Platform (ETOP) Mesoscape project. Mod Pathol 2022; 35:1888-1899. [PMID: 36115922 PMCID: PMC9708564 DOI: 10.1038/s41379-022-01145-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 07/13/2022] [Accepted: 07/20/2022] [Indexed: 12/24/2022]
Abstract
Pleural mesothelioma (PM) is an aggressive malignancy with poor prognosis. Although histology and pathologic stage are important prognostic factors, better prognostic biomarkers are needed. The ribosomal protein S6 is a downstream target of the phosphatidylinositol 3-kinase (PI3K) pathway involved in protein synthesis and cell proliferation. In previous studies, low phosphorylated S6 (pS6) immunoreactivity was significantly correlated with longer progression-free survival (PFS) and overall survival (OS) in PM patients. We aimed to correlate pS6 expression to clinical data in a large multi-centre PM cohort as part of the European Thoracic Oncology Platform (ETOP) Mesoscape project. Tissue Micro Arrays (TMAs) of PM were constructed and expression of pS6 was evaluated by a semi-quantitatively aggregate H-score. Expression results were correlated to patient characteristics as well as OS/PFS. pS6 IHC results of 364 patients from 9 centres, diagnosed between 1999 and 2017 were available. The primary histology of included tumours was epithelioid (70.3%), followed by biphasic (24.2%) and sarcomatoid (5.5%). TMAs included both treatment-naïve and tumour tissue taken after induction chemotherapy. High pS6 expression (181 patients with H-score>1.41) was significantly associated with less complete resection. In the overall cohort, OS/PFS were not significantly different between pS6-low and pS6-high patients. In a subgroup analysis non-epithelioid (biphasic and sarcomatoid) patients with high pS6 expression showed a significantly shorter OS (p < 0.001, 10.7 versus 16.9 months) and PFS (p < 0.001, 6.2 versus 10.8 months). In subgroup analysis, in non-epithelioid PM patients high pS6 expression was associated with significantly shorter OS and PFS. These exploratory findings suggest a clinically relevant PI3K pathway activation in non-epithelioid PM which might lay the foundation for future targeted treatment strategies.
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Amin AG, Jeong SW, Gillick JL, Sursal T, Murali R, Gandhi CD, Jhanwar-Uniyal M. Targeting the mTOR pathway using novel ATP‑competitive inhibitors, Torin1, Torin2 and XL388, in the treatment of glioblastoma. Int J Oncol 2021; 59:83. [PMID: 34523696 PMCID: PMC8448541 DOI: 10.3892/ijo.2021.5263] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 08/11/2021] [Indexed: 12/13/2022] Open
Abstract
Mechanistic target of rapamycin (mTOR), which functions via two multiprotein complexes termed mTORC1 and mTORC2, is positioned in the canonical phosphoinositide 3-kinase-related kinase (PI3K)/AKT (PI3K/AKT) pathways. These complexes exert their actions by regulating other important kinases, such as 40S ribosomal S6 kinases (S6K), eukaryotic translation initiation factor 4E (elF4E)-binding protein 1 (4E-BP1) and AKT, to control cell growth, proliferation, migration and survival in response to nutrients and growth factors. Glioblastoma (GB) is a devastating form of brain cancer, where the mTOR pathway is deregulated due to frequent upregulation of the Receptor Tyrosine Kinase/PI3K pathways and loss of the tumor suppressor phosphatase and tensin homologue (PTEN). Rapamycin and its analogs were less successful in clinical trials for patients with GB due to their incomplete inhibition of mTORC1 and the activation of mitogenic pathways via negative feedback loops. Here, the effects of selective ATP-competitive dual inhibitors of mTORC1 and mTORC2, Torin1, Torin2 and XL388, are reported. Torin2 exhibited concentration-dependent pharmacodynamic effects on inhibition of phosphorylation of the mTORC1 substrates S6KSer235/236 and 4E-BP1Thr37/46 as well as the mTORC2 substrate AKTSer473 resulting in suppression of tumor cell migration, proliferation and S-phase entry. Torin1 demonstrated similar effects, but only at higher doses. XL388 suppressed cell proliferation at a higher dose, but failed to inhibit cell migration. Treatment with Torin1 suppressed phosphorylation of proline rich AKT substrate of 40 kDa (PRAS40) at Threonine 246 (PRAS40Thr246) whereas Torin2 completely abolished it. XL388 treatment suppressed the phosphorylation of PRAS40Thr246 only at higher doses. Drug resistance analysis revealed that treatment of GB cells with XL388 rendered partial drug resistance, which was also seen to a lesser extent with rapamycin and Torin1 treatments. However, treatment with Torin2 completely eradicated the tumor cell population. These results strongly suggest that Torin2, compared to Torin1 or XL388, is more effective in suppressing mTORC1 and mTORC2, and therefore in the inhibition of the GB cell proliferation, dissemination and in overcoming resistance to therapy. These findings underscore the significance of Torin2 in the treatment of GB.
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Affiliation(s)
- Anubhav G Amin
- Department of Neurosurgery, New York Medical College/Westchester Medical Center, Valhalla, NY 10595, USA
| | - Seung Won Jeong
- Department of Neurosurgery, New York Medical College/Westchester Medical Center, Valhalla, NY 10595, USA
| | - John L Gillick
- Department of Neurosurgery, New York Medical College/Westchester Medical Center, Valhalla, NY 10595, USA
| | - Tolga Sursal
- Department of Neurosurgery, New York Medical College/Westchester Medical Center, Valhalla, NY 10595, USA
| | - Raj Murali
- Department of Neurosurgery, New York Medical College/Westchester Medical Center, Valhalla, NY 10595, USA
| | - Chirag D Gandhi
- Department of Neurosurgery, New York Medical College/Westchester Medical Center, Valhalla, NY 10595, USA
| | - Meena Jhanwar-Uniyal
- Department of Neurosurgery, New York Medical College/Westchester Medical Center, Valhalla, NY 10595, USA
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Weiss B, Allen GE, Kloehn J, Abid K, Jaquier-Gubler P, Curran JA. eIF4E3 forms an active eIF4F complex during stresses (eIF4FS) targeting mTOR and re-programs the translatome. Nucleic Acids Res 2021; 49:5159-5176. [PMID: 33893802 PMCID: PMC8136781 DOI: 10.1093/nar/gkab267] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 03/24/2021] [Accepted: 03/31/2021] [Indexed: 12/13/2022] Open
Abstract
The eIF4E are a family of initiation factors that bind the mRNA 5' cap, regulating the proteome and the cellular phenotype. eIF4E1 mediates global translation and its activity is controlled via the PI3K/AKT/mTOR pathway. mTOR down-regulation results in eIF4E1 sequestration into an inactive complex with the 4E binding proteins (4EBPs). The second member, eIF4E2, regulates the translatome during hypoxia. However, the exact function of the third member, eIF4E3, has remained elusive. We have dissected its function using a range of techniques. Starting from the observation that it does not interact with 4EBP1, we demonstrate that eIF4E3 recruitment into an eIF4F complex occurs when Torin1 inhibits the mTOR pathway. Ribo-seq studies demonstrate that this complex (eIF4FS) is translationally active during stress and that it selects specific mRNA populations based on 5' TL (UTR) length. The interactome reveals that it associates with cellular proteins beyond the cognate initiation factors, suggesting that it may have 'moon-lighting' functions. Finally, we provide evidence that cellular metabolism is altered in an eIF4E3 KO background but only upon Torin1 treatment. We propose that eIF4E3 acts as a second branch of the integrated stress response, re-programming the translatome to promote 'stress resistance' and adaptation.
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Affiliation(s)
- Benjamin Weiss
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Switzerland
| | - George Edward Allen
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Switzerland
| | - Joachim Kloehn
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Switzerland
| | - Karim Abid
- Catecholamine and Peptides Laboratory, Service of Clinical Pharmacology, Lausanne University Hospital and University of Lausanne, Switzerland
| | - Pascale Jaquier-Gubler
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Switzerland
| | - Joseph Alphonsus Curran
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Switzerland
- Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, Switzerland
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Ibrahim K, Abdul Murad NA, Harun R, Jamal R. Knockdown of Tousled‑like kinase 1 inhibits survival of glioblastoma multiforme cells. Int J Mol Med 2020; 46:685-699. [PMID: 32468002 PMCID: PMC7307829 DOI: 10.3892/ijmm.2020.4619] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 01/17/2020] [Indexed: 12/27/2022] Open
Abstract
Glioblastoma multiforme (GBM) is an aggressive type of brain tumour that commonly exhibits resistance to treatment. The tumour is highly heterogenous and complex kinomic alterations have been reported leading to dysregulation of signalling pathways. The present study aimed to investigate the novel kinome pathways and to identify potential therapeutic targets in GBM. Meta‑analysis using Oncomine identified 113 upregulated kinases in GBM. RNAi screening was performed on identified kinases using ON‑TARGETplus siRNA library on LN18 and U87MG. Tousled‑like kinase 1 (TLK1), which is a serine/threonine kinase was identified as a potential hit. In vitro functional validation was performed as the role of TLK1 in GBM is unknown. TLK1 knockdown in GBM cells significantly decreased cell viability, clonogenicity, proliferation and induced apoptosis. TLK1 knockdown also chemosensitised the GBM cells to the sublethal dose of temozolomide. The downstream pathways of TLK1 were examined using microarray analysis, which identified the involvement of DNA replication, cell cycle and focal adhesion signalling pathways. In vivo validation of the subcutaneous xenografts of stably transfected sh‑TLK1 U87MG cells demonstrated significantly decreased tumour growth in female BALB/c nude mice. Together, these results suggested that TLK1 may serve a role in GBM survival and may serve as a potential target for glioma.
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Affiliation(s)
- Kamariah Ibrahim
- UKM Medical Molecular Biology Institute, Universiti Kebangsaan Malaysia, Kuala Lumpur 56000, Malaysia
| | - Nor Azian Abdul Murad
- UKM Medical Molecular Biology Institute, Universiti Kebangsaan Malaysia, Kuala Lumpur 56000, Malaysia
| | - Roslan Harun
- KPJ Ampang Puteri Specialist Hospital, Ampang, Selangor 68000, Malaysia
| | - Rahman Jamal
- UKM Medical Molecular Biology Institute, Universiti Kebangsaan Malaysia, Kuala Lumpur 56000, Malaysia
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Wei Y, Han X, Zhao C. PDK1 regulates the survival of the developing cortical interneurons. Mol Brain 2020; 13:65. [PMID: 32366272 PMCID: PMC7197138 DOI: 10.1186/s13041-020-00604-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2019] [Accepted: 04/22/2020] [Indexed: 01/08/2023] Open
Abstract
Inhibitory interneurons are critical for maintaining the excitatory/inhibitory balance. During the development cortical interneurons originate from the ganglionic eminence and arrive at the dorsal cortex through two tangential migration routes. However, the mechanisms underlying the development of cortical interneurons remain unclear. 3-Phosphoinositide-dependent protein kinase-1 (PDK1) has been shown to be involved in a variety of biological processes, including cell proliferation and migration, and plays an important role in the neurogenesis of cortical excitatory neurons. However, the function of PDK1 in interneurons is still unclear. Here, we reported that the disruption of Pdk1 in the subpallium achieved by crossing the Dlx5/6-Cre-IRES-EGFP line with Pdk1fl/fl mice led to the severely increased apoptosis of immature interneurons, subsequently resulting in a remarkable reduction in cortical interneurons. However, the tangential migration, progenitor pools and cell proliferation were not affected by the disruption of Pdk1. We further found the activity of AKT-GSK3β signaling pathway was decreased after Pdk1 deletion, suggesting it might be involved in the regulation of the survival of cortical interneurons. These results provide new insights into the function of PDK1 in the development of the telencephalon.
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Affiliation(s)
- Yongjie Wei
- Key Laboratory of Developmental Genes and Human Diseases, MOE, School of Medicine, Southeast University, Nanjing, 210009, China
| | - Xiaoning Han
- Key Laboratory of Developmental Genes and Human Diseases, MOE, School of Medicine, Southeast University, Nanjing, 210009, China
| | - Chunjie Zhao
- Key Laboratory of Developmental Genes and Human Diseases, MOE, School of Medicine, Southeast University, Nanjing, 210009, China.
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Wang SW, Lee CH, Lin MS, Chi CW, Chen YJ, Wang GS, Liao KW, Chiu LP, Wu SH, Huang DM, Chen L, Shen YS. ZnO Nanoparticles Induced Caspase-Dependent Apoptosis in Gingival Squamous Cell Carcinoma through Mitochondrial Dysfunction and p70S6K Signaling Pathway. Int J Mol Sci 2020; 21:ijms21051612. [PMID: 32111101 PMCID: PMC7084801 DOI: 10.3390/ijms21051612] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 02/07/2020] [Accepted: 02/20/2020] [Indexed: 12/17/2022] Open
Abstract
Zinc oxide nanoparticles (ZnO-NPs) are increasingly used in sunscreens, food additives, pigments, rubber manufacture, and electronic materials. Several studies have shown that ZnO-NPs inhibit cell growth and induce apoptosis by the production of oxidative stress in a variety of human cancer cells. However, the anti-cancer property and molecular mechanism of ZnO-NPs in human gingival squamous cell carcinoma (GSCC) are not fully understood. In this study, we found that ZnO-NPs induced growth inhibition of GSCC (Ca9-22 and OECM-1 cells), but no damage in human normal keratinocytes (HaCaT cells) and gingival fibroblasts (HGF-1 cells). ZnO-NPs caused apoptotic cell death of GSCC in a concentration-dependent manner by the quantitative assessment of oligonucleosomal DNA fragmentation. Flow cytometric analysis of cell cycle progression revealed that sub-G1 phase accumulation was dramatically induced by ZnO-NPs. In addition, ZnO-NPs increased the intracellular reactive oxygen species and specifically superoxide levels, and also decreased the mitochondrial membrane potential. ZnO-NPs further activated apoptotic cell death via the caspase cascades. Importantly, anti-oxidant and caspase inhibitor clearly prevented ZnO-NP-induced cell death, indicating the fact that superoxide-induced mitochondrial dysfunction is associated with the ZnO-NP-mediated caspase-dependent apoptosis in human GSCC. Moreover, ZnO-NPs significantly inhibited the phosphorylation of ribosomal protein S6 kinase (p70S6K kinase). In a corollary in vivo study, our results demonstrated that ZnO-NPs possessed an anti-cancer effect in a zebrafish xenograft model. Collectively, these results suggest that ZnO-NPs induce apoptosis through the mitochondrial oxidative damage and p70S6K signaling pathway in human GSCC. The present study may provide an experimental basis for ZnO-NPs to be considered as a promising novel anti-tumor agent for the treatment of gingival cancer.
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Affiliation(s)
- Shih-Wei Wang
- Department of Medicine, MacKay Medical College, New Taipei City 252, Taiwan;
- Graduate Institute of Natural Products, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Chien-Hsing Lee
- Department of Pharmacology, Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan;
- Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan
| | - Ming-Shen Lin
- Department of Water Resources and Environmental Engineering, Tamkang University, New Taipei City 251, Taiwan;
| | - Chih-Wen Chi
- Department of Nursing, MacKay Medical College, New Taipei City 252, Taiwan;
- Department of Medical Research, MacKay Memorial Hospital, Taipei 104, Taiwan
| | - Yu-Jen Chen
- MacKay Junior College of Medicine, Nursing, and Management, Taipei 112, Taiwan;
- Department of Radiation Oncology, MacKay Memorial Hospital, Taipei 104, Taiwan
| | - Guo-Shou Wang
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu 300, Taiwan; (G.-S.W.); (K.-W.L.)
- Department of Orthopaedics, MacKay Memorial Hospital, Taipei 104, Taiwan
| | - Kuang-Wen Liao
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu 300, Taiwan; (G.-S.W.); (K.-W.L.)
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu 300, Taiwan
| | - Li-Pin Chiu
- General Education Center, University of Taipei, Taipei 100, Taiwan;
- Division of General Surgery, Taipei City Hospital, Taipei 103, Taiwan
| | - Shu-Hui Wu
- Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, Miaoli County 350, Taiwan;
| | - Dong-Ming Huang
- Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, Miaoli County 350, Taiwan;
- Correspondence: (D.-M.H.); (L.C.); (Y.-S.S.); Tel.: +886-37-246-166 (ext. 38105) (D.-M.H.); +886-2-2621-5656 (ext. 2682) (L.C.); +886-2-2636-0303 (ext. 1422) (Y.-S.S.)
| | - Luke Chen
- Department of Water Resources and Environmental Engineering, Tamkang University, New Taipei City 251, Taiwan;
- Correspondence: (D.-M.H.); (L.C.); (Y.-S.S.); Tel.: +886-37-246-166 (ext. 38105) (D.-M.H.); +886-2-2621-5656 (ext. 2682) (L.C.); +886-2-2636-0303 (ext. 1422) (Y.-S.S.)
| | - Yung-Shuen Shen
- Institute of Geriatric Welfare Technology and Science, MacKay Medical College, New Taipei City 252, Taiwan
- Correspondence: (D.-M.H.); (L.C.); (Y.-S.S.); Tel.: +886-37-246-166 (ext. 38105) (D.-M.H.); +886-2-2621-5656 (ext. 2682) (L.C.); +886-2-2636-0303 (ext. 1422) (Y.-S.S.)
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Zhang Z, Yang J, Maimaitiyimin R, Ma M, Zhang H, Wang R. Radiation-induced mitotic catastrophe is associated with down-regulated ribosomal biosynthesis and mitosis genes. ALL LIFE 2020. [DOI: 10.1080/26895293.2020.1806117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Affiliation(s)
- Zegao Zhang
- Department of Radiation Oncology, Tumor Hospital Affiliated To Xinjiang Medical University, Urumqi, People’s Republic of China
- Second Department of Radiation Oncology, People’s Hospital of Xinjiang Uyghur Autonomous Region, Urumqi, People’s Republic of China
| | - Jie Yang
- Second Department of Radiation Oncology, People’s Hospital of Xinjiang Uyghur Autonomous Region, Urumqi, People’s Republic of China
| | - Reyila Maimaitiyimin
- Second Department of Radiation Oncology, People’s Hospital of Xinjiang Uyghur Autonomous Region, Urumqi, People’s Republic of China
| | - Miaomiao Ma
- Second Department of Radiation Oncology, People’s Hospital of Xinjiang Uyghur Autonomous Region, Urumqi, People’s Republic of China
| | - Hui Zhang
- Research and Education Center, People’ s Hospital of Xinjiang Uyghur Autonomous Region
| | - Ruozheng Wang
- Department of Radiation Oncology, Tumor Hospital Affiliated To Xinjiang Medical University, Urumqi, People’s Republic of China
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Yoneda Y, Kuramoto N, Kawada K. The role of glutamine in neurogenesis promoted by the green tea amino acid theanine in neural progenitor cells for brain health. Neurochem Int 2019; 129:104505. [PMID: 31310779 DOI: 10.1016/j.neuint.2019.104505] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Revised: 07/11/2019] [Accepted: 07/12/2019] [Indexed: 12/15/2022]
Abstract
The green tea amino acid theanine is abundant in green tea rather than black and oolong teas, which are all made of the identical tea plant "Chanoki" (Camellia sinensis). Theanine has a molecular structure close to glutamine (GLN) compared to glutamic acid (Glu), in terms of the absence of a free carboxylic acid moiety from the gamma carbon position. Theanine efficiently inhibits [3H]GLN uptake without affecting [3H]Glu uptake in rat brain synaptosomes. In contrast to GLN, however, theanine markedly stimulates the abilities to replicate and to commit to a neuronal lineage following prolonged exposure in cultured neural progenitor cells (NPCs) prepared from embryonic and adult rodent brains. Upregulation of transcript expression is found for one of the GLN transporter isoforms, Slc38a1, besides the promotion of both proliferation and neuronal commitment along with acceleration of the phosphorylation of mechanistic target of rapamycin (mTOR) and relevant downstream proteins, in murine NPCs cultured with theanine. Stable overexpression of Slc38a1 similarly facilitates both cellular replication and neuronal commitment in pluripotent embryonic carcinoma P19 cells. In P19 cells with stable overexpression of Slc38a1, marked phosphorylation is seen for mTOR and downstream proteins in a manner insensitive to further additional phosphorylation by theanine. Taken together, theanine would exhibit a novel pharmacological property to up-regulate Slc38a1 expression for activation of the intracellular mTOR signaling pathway required for neurogenesis after sustained exposure in undifferentiated NPCs in the brain. In this review, a novel neurogenic property of the green tea amino acid theanine is summarized for embryonic and adult neurogenesis with a focus on the endogenous amino acid GLN on the basis of our accumulating evidence to date.
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Affiliation(s)
- Yukio Yoneda
- Department of Pharmacology, Osaka University Graduate School of Dentistry, Suita, 565-0871, Japan; The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, 140-0001, Tokyo, Japan.
| | - Nobuyuki Kuramoto
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, 140-0001, Tokyo, Japan; Laboratory of Molecular Pharmacology, Setsunan University Faculty of Pharmaceutical Sciences, Hirakata, 573-0101, Japan
| | - Koichi Kawada
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, 140-0001, Tokyo, Japan; Department of Pharmacology, Chiba Institute of Science Faculty of Pharmaceutical Sciences, Chiba, 288-0025, Japan
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Jhanwar-Uniyal M, Wainwright JV, Mohan AL, Tobias ME, Murali R, Gandhi CD, Schmidt MH. Diverse signaling mechanisms of mTOR complexes: mTORC1 and mTORC2 in forming a formidable relationship. Adv Biol Regul 2019; 72:51-62. [PMID: 31010692 DOI: 10.1016/j.jbior.2019.03.003] [Citation(s) in RCA: 173] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 03/25/2019] [Accepted: 03/25/2019] [Indexed: 02/07/2023]
Abstract
Activation of Mechanistic target of rapamycin (mTOR) signaling plays a crucial role in tumorigenesis of numerous malignancies including glioblastoma (GB). The Canonical PI3K/Akt/mTOR signaling cascade is commonly upregulated due to loss of the tumor suppressorm PTEN, a phosphatase that acts antagonistically to the kinase (PI3K) in conversion of PIP2 to PIP3. mTOR forms two multiprotein complexes, mTORC1 and mTORC2 which are composed of discrete protein binding partners to regulate cell growth, motility, and metabolism. These complexes are sensitive to distinct stimuli, as mTORC1 is sensitive to nutrients while mTORC2 is regulated via PI3K and growth factor signaling. The main function of mTORC1 is to regulate protein synthesis and cell growth through downstream molecules: 4E-BP1 (also called EIF4E-BP1) and S6K. On the other hand, mTORC2 is responsive to growth factor signaling by phosphorylating the C-terminal hydrophobic motif of some AGC kinases like Akt and SGK and it also plays a crucial role in maintenance of normal and cancer cells through its association with ribosomes, and is involved in cellular metabolic regulation. mTORC1 and mTORC2 regulate each other, as shown by the fact that Akt regulates PRAS40 phosphorylation, which disinhibits mTORC1 activity, while S6K regulates Sin1 to modulate mTORC2 activity. Allosteric inhibitors of mTOR, rapamycin and rapalogs, remained ineffective in clinical trials of Glioblastoma (GB) patients, in part due to their incomplete inhibition of mTORC1 as well as unexpected activation of mTOR via the loss of negative feedback loops. In recent years, novel ATP binding inhibitors of mTORC1 and mTORC2 suppress mTORC1 activity completely by total dephosphorylation of its downstream substrate pS6KSer235/236, while effectively suppressing mTORC2 activity, as demonstrated by complete dephosphorylation of pAKTSer473. Furthermore by these novel combined mTORC1/mTORC2 inhibitors reduced the proliferation and self-renewal of GB cancer stem cells. However, a search of more effective way to target mTOR has generated a third generation inhibitor of mTOR, "Rapalink", that bivalently combines rapamycin with an ATP-binding inhibitor, which effectively abolishes the mTORC1 activity. All in all, the effectiveness of inhibitors of mTOR complexes can be judged by their ability to suppress both mTORC1/mTORC2 and their ability to impede both cell proliferation and migration along with aberrant metabolic pathways.
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Affiliation(s)
- Meena Jhanwar-Uniyal
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA.
| | - John V Wainwright
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
| | - Avinash L Mohan
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
| | - Michael E Tobias
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
| | - Raj Murali
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
| | - Chirag D Gandhi
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
| | - Meic H Schmidt
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
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12
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Ozmen A, Kipmen-Korgun D, Korgun ET. Rapamycin administration during normal and diabetic pregnancy effects the mTOR and angiogenesis signaling in the rat placenta. J Gynecol Obstet Hum Reprod 2019; 48:193-199. [DOI: 10.1016/j.jogoh.2018.12.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 12/04/2018] [Accepted: 12/12/2018] [Indexed: 12/21/2022]
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13
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A novel PI3K/mTOR dual inhibitor, CMG002, overcomes the chemoresistance in ovarian cancer. Gynecol Oncol 2019; 153:135-148. [PMID: 30686552 DOI: 10.1016/j.ygyno.2019.01.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 01/07/2019] [Accepted: 01/09/2019] [Indexed: 11/23/2022]
Abstract
OBJECTIVE Ovarian cancer is the leading cause of gynecologic-related mortality worldwide. Despite successful initial treatment, overall survival rates are very low because tumors develop resistance to chemotherapeutic drugs. The PI3K/mTOR pathway is a key signaling pathway involved in drug resistance of ovarian cancer cells. The aim of this study was to examine the effect of a newly developed PI3K/mTOR dual inhibitor, CMG002, on chemoresistant ovarian cancer cells. METHODS We examined the effects of CMG002, and its synergistic effects when combined with paclitaxel or cisplatin, on cell viability, cell cycle arrest, and apoptosis of PTX-resistant SKpac17 or cisplatin-resistant A2780cis ovarian cancer cells in vitro. Western blot analysis was performed to assess expression of PI3K, p-mTOR, p-Akt, p-S6, Bim, and caspase-3. In vivo studies were carried out in a xenograft mouse model, followed by TUNEL and immunohistochemical staining of excised tumor tissue. RESULTS CMG002 showed marked toxicity against chemoresistant ovarian cancer cells and re-sensitized these cells to chemotherapeutic agents by suppressing cell proliferation and inducing G1 cell cycle arrest and apoptosis. In vivo xenograft studies revealed that treatment with CMG002, either alone or in combination with paclitaxel or cisplatin, led to a marked reduction in tumor growth. CMG002 caused marked suppression of mTOR (Ser2448), Akt (Ser473), Akt (Thr308), and S6 (Ser235/236) phosphorylation, both in vitro and in vivo. CONCLUSION Taken together, CMG002, a very potent PI3K/mTOR dual inhibitor, induced cytotoxicity in chemoresistant ovarian cancer cells, suggesting that this novel inhibitor might be a new therapeutic strategy for chemoresistant ovarian cancer.
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Calamita P, Gatti G, Miluzio A, Scagliola A, Biffo S. Translating the Game: Ribosomes as Active Players. Front Genet 2018; 9:533. [PMID: 30498507 PMCID: PMC6249331 DOI: 10.3389/fgene.2018.00533] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 10/22/2018] [Indexed: 12/18/2022] Open
Abstract
Ribosomes have been long considered as executors of the translational program. The fact that ribosomes can control the translation of specific mRNAs or entire cellular programs is often neglected. Ribosomopathies, inherited diseases with mutations in ribosomal factors, show tissue specific defects and cancer predisposition. Studies of ribosomopathies have paved the way to the concept that ribosomes may control translation of specific mRNAs. Studies in Drosophila and mice support the existence of heterogeneous ribosomes that differentially translate mRNAs to coordinate cellular programs. Recent studies have now shown that ribosomal activity is not only a critical regulator of growth but also of metabolism. For instance, glycolysis and mitochondrial function have been found to be affected by ribosomal availability. Also, ATP levels drop in models of ribosomopathies. We discuss findings highlighting the relevance of ribosome heterogeneity in physiological and pathological conditions, as well as the possibility that in rate-limiting situations, ribosomes may favor some translational programs. We discuss the effects of ribosome heterogeneity on cellular metabolism, tumorigenesis and aging. We speculate a scenario in which ribosomes are not only executors of a metabolic program but act as modulators.
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Affiliation(s)
- Piera Calamita
- INGM, National Institute of Molecular Genetics, "Romeo ed Enrica Invernizzi", Milan, Italy.,Dipartimento di Bioscienze, Università Degli Studi Di Milano, Milan, Italy
| | - Guido Gatti
- INGM, National Institute of Molecular Genetics, "Romeo ed Enrica Invernizzi", Milan, Italy.,Dipartimento di Bioscienze, Università Degli Studi Di Milano, Milan, Italy
| | - Annarita Miluzio
- INGM, National Institute of Molecular Genetics, "Romeo ed Enrica Invernizzi", Milan, Italy
| | - Alessandra Scagliola
- INGM, National Institute of Molecular Genetics, "Romeo ed Enrica Invernizzi", Milan, Italy.,Dipartimento di Bioscienze, Università Degli Studi Di Milano, Milan, Italy
| | - Stefano Biffo
- INGM, National Institute of Molecular Genetics, "Romeo ed Enrica Invernizzi", Milan, Italy.,Dipartimento di Bioscienze, Università Degli Studi Di Milano, Milan, Italy
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Li Y, Zhu M, Huo Y, Zhang X, Liao M. Anti-fibrosis activity of combination therapy with epigallocatechin gallate, taurine and genistein by regulating glycolysis, gluconeogenesis, and ribosomal and lysosomal signaling pathways in HSC-T6 cells. Exp Ther Med 2018; 16:4329-4338. [PMID: 30542382 PMCID: PMC6257822 DOI: 10.3892/etm.2018.6743] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 12/21/2017] [Indexed: 12/24/2022] Open
Abstract
A previous study by our group indicated that combined treatment with taurine, epigallocatechin gallate (EGCG) and genistein protects against liver fibrosis. The aim of the present study was to elucidate the antifibrotic mechanism of this combination treatment using isobaric tag for relative and absolute quantification (iTRAQ)-based proteomics in an activated rat hepatic stellate cell (HSC) line. In the present study, HSC-T6 cells were incubated with taurine, EGCG and genistein, and cellular proteins were extracted and processed for iTRAQ labeling. Quantification and identification of proteins was performed using two-dimensional liquid chromatography coupled with tandem mass spectrometry. Proteomic analysis indicated that the expression of 166 proteins were significantly altered in response to combination treatment with taurine, EGCG and genistein. A total 76 of these proteins were upregulated and 90 were downregulated. Differentially expressed proteins were grouped according to their association with specific Kyoto Encyclopedia of Genes and Genomes pathways. The results indicated that the differentially expressed proteins hexokinase-2 and lysosome-associated membrane glycoprotein 1 were associated with glycolysis, gluconeogenesis and lysosome signaling pathways. The expression of these proteins was validated using western blot analysis; the expression of hexokinase-2 was significantly decreased and the expression of lysosome-associated membrane glycoprotein 1 was significantly increased in HSC-T6 cells treated with taurine, EGCG and genistein compared with the control, respectively (P<0.05). These results were in accordance with the changes in protein expression identified using the iTRAQ approach. Therefore, the antifibrotic effect of combined therapy with taurine, EGCG and genistein may be associated with the activation of several pathways in HSCs, including glycolysis, gluconeogenesis, and the ribosome and lysosome signaling pathways. The differentially expressed proteins identified in the current study may be useful for treatment of liver fibrosis in the future.
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Affiliation(s)
- Yan Li
- Guangxi University Library, Guangxi University, Nanning, Guangxi 530004, P.R. China
| | - Min Zhu
- Guangxi University Library, Guangxi University, Nanning, Guangxi 530004, P.R. China
| | - Yani Huo
- Medical Scientific Research Centre, Key Laboratory of High-Incidence-Tumor Prevention and Treatment, Guangxi Medical University, Ministry of Education, Nanning, Guangxi 530021, P.R. China
| | - Xuerong Zhang
- Medical Scientific Research Centre, Key Laboratory of High-Incidence-Tumor Prevention and Treatment, Guangxi Medical University, Ministry of Education, Nanning, Guangxi 530021, P.R. China
| | - Ming Liao
- Medical Scientific Research Centre, Key Laboratory of High-Incidence-Tumor Prevention and Treatment, Guangxi Medical University, Ministry of Education, Nanning, Guangxi 530021, P.R. China
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Cross Talk Networks of Mammalian Target of Rapamycin Signaling With the Ubiquitin Proteasome System and Their Clinical Implications in Multiple Myeloma. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2018; 343:219-297. [PMID: 30712673 DOI: 10.1016/bs.ircmb.2018.06.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Multiple myeloma (MM) is the second most common hematological malignancy and results from the clonal amplification of plasma cells. Despite recent advances in treatment, MM remains incurable with a median survival time of only 5-6years, thus necessitating further insights into MM biology and exploitation of novel therapeutic approaches. Both the ubiquitin proteasome system (UPS) and the PI3K/Akt/mTOR signaling pathways have been implicated in the pathogenesis, and treatment of MM and different lines of evidence suggest a close cross talk between these central cell-regulatory signaling networks. In this review, we outline the interplay between the UPS and mTOR pathways and discuss their implications for the pathophysiology and therapy of MM.
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17
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Kostyniuk DJ, Culbert BM, Mennigen JA, Gilmour KM. Social status affects lipid metabolism in rainbow trout, Oncorhynchus mykiss. Am J Physiol Regul Integr Comp Physiol 2018; 315:R241-R255. [PMID: 29561648 DOI: 10.1152/ajpregu.00402.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Juvenile rainbow trout ( Oncorhynchus mykiss) confined in pairs form social hierarchies in which socially subordinate fish display characteristic traits, including reduced growth rates and altered glucose metabolism. These effects are, in part, mediated by chronically elevated cortisol levels and/or reduced feeding. To determine the effects of social status on lipid metabolism, trout were held in pairs for 4 days, following which organismal and liver-specific indexes of lipid metabolism were measured. At the organismal level, circulating triglycerides were elevated in dominant trout, whereas subordinate trout exhibited elevated concentrations of circulating free fatty acids (FFAs) and lowered plasma total cholesterol levels. At the molecular level, increased expression of lipogenic genes in dominant trout and cpt1a in subordinate trout was identified, suggesting a contribution of increased de novo lipogenesis to circulating triglycerides in dominant trout and reliance on circulating FFAs for β-oxidation in the liver of subordinates. Given the emerging importance of microRNAs (miRNA) in the regulation of hepatic lipid metabolism, candidate miRNAs were profiled, revealing increased expression of the lipogenic miRNA-33 in dominant fish. Because the Akt-TOR-S6-signaling pathway is an important upstream regulator of hepatic lipid metabolism, its signaling activity was quantified. However, the only difference detected among groups was a strong increase in S6 phosphorylation in subordinate trout. In general, the changes observed in lipid metabolism of subordinates were not mimicked by either cortisol treatment or fasting alone, indicating the existence of specific, emergent effects of subordinate social status itself on this fuel.
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Affiliation(s)
| | - Brett M Culbert
- Department of Biology, University of Ottawa , Ottawa, Ontario , Canada
| | - Jan A Mennigen
- Department of Biology, University of Ottawa , Ottawa, Ontario , Canada
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Different concentrations of docosahexanoic acid supplement during lactation result in different outcomes in preterm Sprague-Dawley rats. Brain Res 2017; 1678:367-373. [PMID: 29146112 DOI: 10.1016/j.brainres.2017.11.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 10/25/2017] [Accepted: 11/09/2017] [Indexed: 11/21/2022]
Abstract
PROPOSE In this study, we evaluated the effects of different concentrations of docosahexanoic acid (DHA) supplement on preterm Sprague-Dawley rat pups, and in parallel, measured the phosphorylation activity of the mTOR pathway in the hippocampal CA1 area. METHODS Preterm Sprague-Dawley rat pups were randomly assigned to experimental groups which included; a sufficient DHA group (100 mg/kg/day); an enriched DHA group (300 mg/kg/day); an excess DHA group (800 mg/kg/day); and a deficient DHA group (normal saline gavage 0.1 ml/10 g). Body weight (g) was measured at days 1/7/14/21/28/42, respectively. Spatial learning and memory were also tested using the Morris water maze at week 6 (day 42). Finally, activation of the mTOR signaling pathway in hippocampal CA1 area were evaluated by western blotting. RESULTS Postnatal sufficient/enriched docosahexanoic acid supplement ameliorated body weight restriction, spatial learning and memory restriction, and decreased phosphorylation of AKT, mTOR, P70S6K1, and 4EBP1 in hippocampal CA1 area. Furthermore, excess docosahexanoic acid supplement impeded weight gain and spatial learning and memory, perturbed serum unsaturated fatty acid, and downregulated phosphorylation of AKT, mTOR, P70S6K1, and 4EBP1 in hippocampal CA1 area. CONCLUSION Postnatal sufficient/enriched DHA supplement ameliorated growth and spatial learning and memory impairment and upregulated the mTOR pathway in preterm pups, although excessive DHA supplement did not have any beneficial effects.
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19
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Discrete signaling mechanisms of mTORC1 and mTORC2: Connected yet apart in cellular and molecular aspects. Adv Biol Regul 2017; 64:39-48. [PMID: 28189457 DOI: 10.1016/j.jbior.2016.12.001] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 12/23/2016] [Accepted: 12/23/2016] [Indexed: 12/19/2022]
Abstract
Activation of PI3K/Akt/mTOR (mechanistic target of rapamycin) signaling cascade has been shown in tumorigenesis of numerous malignancies including glioblastoma (GB). This signaling cascade is frequently upregulated due to loss of the tumor suppressor PTEN, a phosphatase that functions antagonistically to PI3K. mTOR regulates cell growth, motility, and metabolism by forming two multiprotein complexes, mTORC1 and mTORC2, which are composed of special binding partners. These complexes are sensitive to distinct stimuli. mTORC1 is sensitive to nutrients and mTORC2 is regulated via PI3K and growth factor signaling. mTORC1 regulates protein synthesis and cell growth through downstream molecules: 4E-BP1 (also called EIF4E-BP1) and S6K. Also, mTORC2 is responsive to growth factor signaling by phosphorylating the C-terminal hydrophobic motif of some AGC kinases like Akt and SGK. mTORC2 plays a crucial role in maintenance of normal and cancer cells through its association with ribosomes, and is involved in cellular metabolic regulation. Both complexes control each other as Akt regulates PRAS40 phosphorylation, which disinhibits mTORC1 activity, while S6K regulates Sin1 to modulate mTORC2 activity. Another significant component of mTORC2 is Sin1, which is crucial for mTORC2 complex formation and function. Allosteric inhibitors of mTOR, rapamycin and rapalogs, have essentially been ineffective in clinical trials of patients with GB due to their incomplete inhibition of mTORC1 or unexpected activation of mTOR via the loss of negative feedback loops. Novel ATP binding inhibitors of mTORC1 and mTORC2 suppress mTORC1 activity completely by total dephosphorylation of its downstream substrate pS6KSer235/236, while effectively suppressing mTORC2 activity, as demonstrated by complete dephosphorylation of pAKTSer473. Furthermore, proliferation and self-renewal of GB cancer stem cells are effectively targetable by these novel mTORC1 and mTORC2 inhibitors. Therefore, the effectiveness of inhibitors of mTOR complexes can be estimated by their ability to suppress both mTORC1 and 2 and their ability to impede both cell proliferation and migration.
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20
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Decreased activation of placental mTOR family members is associated with the induction of intrauterine growth restriction by secondhand smoke in the mouse. Cell Tissue Res 2016; 367:387-395. [PMID: 27613305 DOI: 10.1007/s00441-016-2496-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 08/17/2016] [Indexed: 12/15/2022]
Abstract
Cigarette smoke is known to be a risk for the development of intrauterine growth restriction (IUGR). Our objective was to assess the effects of secondhand smoke (SHS) during pregnancy and to what extent it regulates the activation of mTOR family members and murine trophoblast invasion. Mice were treated to SHS for 4 days. Placental and fetal weights were recorded at the time of necropsy. Immunohistochemistry was used to determine the level of placental trophoblast invasion. Western blots were utilized to assess the activation of caspase 3, XIAP, mTOR, p70 and 4EBP1 in treated and control placental lysates. As compared to controls, treated animals showed: (1) decreased placental (1.4-fold) and fetal (2.3-fold) weights (p < 0.05); (2) decreased trophoblast invasion; (3) significantly decreased active caspase 3 (1.3-fold; p < 0.02) and increased active XIAP (3.6-fold; p < 0.05) in the placenta; and (4) a significant decrease in the activation of placental mTOR (2.1-fold; p < 0.05), p70 (1.9-fold; p < 0.05) and 4EBP1 (1.3-fold; p < 0.05). Confirmatory in vitro experiments revealed decreased trophoblast invasion when SW71 cells were treated with 0.5 or 1.0 % cigarette smoke extract (CSE). Similar to primary smoking, SHS may induce IUGR via decreased activation of the mTOR family of proteins in the placenta. Increased activation of the placental XIAP protein could be a survival mechanism for abnormal trophoblast cells during SHS exposure. Further, CSE reduced trophoblast invasion, suggesting a direct causative effect of smoke on susceptible trophoblast cells involved in IUGR progression. These results provide important insight into the physiological consequences of SHS exposure and smoke-mediated placental disease.
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Bhattacharya K, Maiti S, Mandal C. PTEN negatively regulates mTORC2 formation and signaling in grade IV glioma via Rictor hyperphosphorylation at Thr1135 and direct the mode of action of an mTORC1/2 inhibitor. Oncogenesis 2016; 5:e227. [PMID: 27239959 PMCID: PMC4945751 DOI: 10.1038/oncsis.2016.34] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 03/10/2016] [Accepted: 03/14/2016] [Indexed: 02/07/2023] Open
Abstract
To investigate the role of PTEN (phosphatase and tensin homolog) in mammalian target of rapamycin complex 2 (mTORC2) signaling in glioblastoma multiforme (GBM), we found higher activation of mTORC2 in PTEN(mu) cells, as evidenced by enhanced phosphorylation of mTOR (Ser2481), AKT (Ser473) and glycogen synthase kinase 3 beta (GSK3β) (Ser9) as compared with PTEN(wt) cells. In addition, PTEN(wt) cells upon PTEN depletion showed mTORC2 activation. The reduced mTORC2 signaling in PTEN(wt) cells was related to higher Rictor phosphorylation at Thr1135 residue. Phosphorylation of Rictor at Thr1135 inhibited its association with mTORC and thus there was a reduction in mTORC2 complex formation. In addition, PTEN(wt) cells expressing mutated Rictor in which Thr1135 was substituted with alanine, showed enhanced mTORC2 formation and signaling. This enhanced mTORC2 signaling promoted inactivation of GSK3β. Thus, we established the reciprocal activation of mTORC2 and GSK3β in GBM. To the best of our knowledge, this is the first report describing role of PTEN in mTORC2 formation by promoting Rictor phosphorylation (Thr1135) in GBM. Furthermore, the drug sensitivity of mTORC2 was evaluated. A newly identified carbazole alkaloid, mahanine, showed cytotoxicity in both PTEN(mu) and PTEN(wt) cells. It inhibited both mTORC1/2 and AKT completely in PTEN(mu) cells, whereas it inhibited only mTORC1 in PTEN(wt) cells. Cytotoxity and AKT-inhibitory activity of the mTORC1/2 inhibitor was increased either by depleting PTEN or in combination with phosphatidylinositol 3 kinase inhibitors in PTEN(wt) cells. In contrast, depletion of Rictor decreased the cytotoxicity of the mTORC1/2 inhibitor in PTEN(mu) cells. Thus, PTEN has an important role in mTORC2 formation and also influences the effectiveness of an mTORC1/2 inhibitor in GBM.
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Affiliation(s)
- K Bhattacharya
- Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research (CSIR)-Indian Institute of Chemical Biology, Kolkata, India
| | - S Maiti
- Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research (CSIR)-Indian Institute of Chemical Biology, Kolkata, India
| | - C Mandal
- Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research (CSIR)-Indian Institute of Chemical Biology, Kolkata, India
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Nayak S, Siddiqui JK, Varner JD. Modelling and analysis of an ensemble of eukaryotic translation initiation models. IET Syst Biol 2016; 5:2. [PMID: 21261397 DOI: 10.1049/iet-syb.2009.0065] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Programmed protein synthesis plays an important role in the cell cycle. Deregulated translation has been observed in several cancers. In this study, the authors constructed an ensemble of mathematical models describing the integration of growth factor signals with translation initiation. Using these models, the authors estimated critical structural features of the translation architecture. Sensitivity and robustness analysis with and without growth factors suggested that a balance between competing regulatory programmes governed translation initiation. Proteins such as Akt and mTor promoted initiation by integrating growth factor signals with the assembly of the 80S initiation complex. However, negative regulators such as PTEN and 4EBP1 restrained initiation in the absence of stimulation. Other proteins such as eIF4E were also found to be structurally critical as deletion of amplification of these components resulted in a network incapable of nominal operation. These findings could help understand the molecular basis of translation deregulation observed in cancer and perhaps lead to new anti-cancer therapeutic strategies. [Includes supplementary material].
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Affiliation(s)
- S Nayak
- Cornell University, School of Chemical and Biomolecular Engineering, Ithaca, USA
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Liu J, Wang H, Wang B, Chen T, Wang X, Huang P, Xu L, Guo Z. Microcystin-LR promotes proliferation by activating Akt/S6K1 pathway and disordering apoptosis and cell cycle associated proteins phosphorylation in HL7702 cells. Toxicol Lett 2016; 240:214-25. [DOI: 10.1016/j.toxlet.2015.10.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Revised: 09/30/2015] [Accepted: 10/17/2015] [Indexed: 12/14/2022]
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Sati L, Soygur B, Celik-Ozenci C. Expression of Mammalian Target of Rapamycin and Downstream Targets in Normal and Gestational Diabetic Human Term Placenta. Reprod Sci 2015; 23:324-32. [DOI: 10.1177/1933719115602765] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Leyla Sati
- Department of Histology and Embryology, Akdeniz University School of Medicine, Antalya, Turkey
| | - Bikem Soygur
- Department of Histology and Embryology, Akdeniz University School of Medicine, Antalya, Turkey
| | - Ciler Celik-Ozenci
- Department of Histology and Embryology, Akdeniz University School of Medicine, Antalya, Turkey
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Yelick PC, Trainor PA. Ribosomopathies: Global process, tissue specific defects. Rare Dis 2015; 3:e1025185. [PMID: 26442198 PMCID: PMC4590025 DOI: 10.1080/21675511.2015.1025185] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 02/18/2015] [Accepted: 02/26/2015] [Indexed: 01/01/2023] Open
Abstract
Disruptions in ribosomal biogenesis would be expected to have global and in fact lethal effects on a developing organism. However, mutations in ribosomal protein genes have been shown in to exhibit tissue specific defects. This seemingly contradictory finding - that globally expressed genes thought to play fundamental housekeeping functions can in fact exhibit tissue and cell type specific functions - provides new insight into roles for ribosomes, the protein translational machinery of the cell, in regulating normal development and disease. Furthermore it illustrates the surprisingly dynamic nature of processes regulating cell type specific protein translation. In this review, we discuss our current knowledge of a variety of ribosomal protein mutations associated with human disease, and models to better understand the molecular mechanisms associated with each. We use specific examples to emphasize both the similarities and differences between the effects of various human ribosomal protein mutations. Finally, we discuss areas of future study that are needed to further our understanding of the role of ribosome biogenesis in normal development, and possible approaches that can be used to treat debilitating ribosomopathy diseases.
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Affiliation(s)
| | - Paul A Trainor
- Stowers Institute ; Kansas City, MO USA ; University of Kansas Medical Center ; Kansas City, KS USA
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Padmanabhan J, Brown KR, Padilla A, Shelanski ML. Functional role of RNA polymerase II and P70 S6 kinase in KCl withdrawal-induced cerebellar granule neuron apoptosis. J Biol Chem 2015; 290:5267-79. [PMID: 25568312 DOI: 10.1074/jbc.m114.575225] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
KCl withdrawal-induced apoptosis in cerebellar granule neurons is associated with aberrant cell cycle activation, and treatment with cyclin-dependent kinase (Cdk) inhibitors protects cells from undergoing apoptosis. Because the Cdk inhibitor flavopiridol is known to inhibit RNA polymerase II (Pol II)-dependent transcription elongation by inhibiting the positive transcription elongation factor b (P-TEFb, a complex of CDK9 and cyclin T), we examined whether inhibition of RNA Pol II protects neurons from apoptosis. Treatment of neurons with 5, 6-dichloro-1-β-D-ribobenzimidazole (DRB), an RNA Pol II-dependent transcription elongation inhibitor, and flavopiridol inhibited phosphorylation and activation of Pol II and protected neurons from undergoing apoptosis. In addition to Pol II, neurons subjected to KCl withdrawal showed increased phosphorylation and activation of p70 S6 kinase, which was inhibited by both DRB and flavopiridol. Immunostaining analysis of the neurons deprived of KCl showed increased nuclear levels of phospho-p70 S6 kinase, and neurons protected with DRB and flavopiridol showed accumulation of the kinase into large spliceosome assembly factor-positive speckle domains within the nuclei. The formation of these foci corresponded with cell survival, and removal of the inhibitors resulted in dispersal of the speckles into smaller foci with subsequent apoptosis induction. Because p70 S6 kinase is known to induce translation of mRNAs containing a 5'-terminal oligopyrimidine tract, our data suggest that transcription and translation of this subset of mRNAs may contribute to KCl withdrawal-induced apoptosis in neurons.
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Affiliation(s)
- Jaya Padmanabhan
- From the Department of Molecular Medicine, University of South Florida Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613 and
| | - Kristy R Brown
- the Department of Pathology and Cell Biology, Taub Center for Alzheimer's Disease, College of Physicians and Surgeons, Columbia University, New York, New York 10032
| | - Amelia Padilla
- From the Department of Molecular Medicine, University of South Florida Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613 and
| | - Michael L Shelanski
- the Department of Pathology and Cell Biology, Taub Center for Alzheimer's Disease, College of Physicians and Surgeons, Columbia University, New York, New York 10032
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Knuth A, Liu L, Nielsen H, Merril D, Torry DS, Arroyo JA. Placenta growth factor induces invasion and activates p70 during rapamycin treatment in trophoblast cells. Am J Reprod Immunol 2014; 73:330-40. [PMID: 25271148 DOI: 10.1111/aji.12327] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 09/05/2014] [Indexed: 12/25/2022] Open
Abstract
PROBLEM Aberrant trophoblast invasion has been associated with human intrauterine growth restriction (IUGR) and preeclampsia (PE). Our objective was to determine placenta growth factor (PlGF)-mediated regulation of cell invasion in trophoblast cells with reduced mammalian target of Rapamycin (mTOR) signaling. METHOD OF STUDY First trimester SW 71 trophoblast cells were subjected to invasion assays with the following conditions: 10% FBS, 10% FBS with Rapamycin, and 10% FBS with Rapamycin and PlGF. mTOR siRNA was also done in these cells. Western blots were performed on cell lysates with antibodies against phospho- and total mTOR, 70-kDa ribosomal protein kinase I (p70), 4EBP1, extracellular regulated kinase (ERK), and phosphatidylinositol-3 kinase (AKT). RESULTS Compared to controls, trophoblast cells showed: (i) a 33% decrease in invasion following Rapamycin treatment, (ii) protection from decreased invasion following Rapamycin and PlGF treatment, (iii) a 31% decrease in mTOR phosphorylation with Rapamycin, (iv) increased phosphorylation of p70 (43%) with Rapamycin and PlGF, and (v) a 76% decrease in invasion following mTOR depletion. CONCLUSION We conclude that first trimester trophoblast invasion is functionally decreased when phosphorylation of mTOR is prevented and this decrease is recovered with the addition of PlGF. Mechanistically, this recovery involves the phosphorylation of p70 independent of mTOR.
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Affiliation(s)
- Allison Knuth
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT, USA
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Jhanwar-Uniyal M, Gillick JL, Neil J, Tobias M, Thwing ZE, Murali R. Distinct signaling mechanisms of mTORC1 and mTORC2 in glioblastoma multiforme: a tale of two complexes. Adv Biol Regul 2014; 57:64-74. [PMID: 25442674 DOI: 10.1016/j.jbior.2014.09.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 09/09/2014] [Indexed: 02/07/2023]
Abstract
Mechanistic target of rapamycin (mTOR) is a serine-threonine kinase that functions via two multiprotein complexes, namely mTORC1 and mTORC2, each characterized by different binding partners that confer separate functions. mTORC1 function is tightly regulated by PI3-K/Akt and is sensitive to rapamycin. mTORC2 is sensitive to growth factors, not nutrients, and is associated with rapamycin-insensitivity. mTORC1 regulates protein synthesis and cell growth through downstream molecules: 4E-BP1 (also called EIF4E-BP1) and S6K. Also, mTORC2 is thought to modulate growth factor signaling by phosphorylating the C-terminal hydrophobic motif of some AGC kinases such as Akt and SGK. Recent evidence has suggested that mTORC2 may play an important role in maintenance of normal as well as cancer cells by virtue of its association with ribosomes, which may be involved in metabolic regulation of the cell. Rapamycin (sirolimus) and its analogs known as rapalogues, such as RAD001 (everolimus) and CCI-779 (temsirolimus), suppress mTOR activity through an allosteric mechanism that acts at a distance from the ATP-catalytic binding site, and are considered incomplete inhibitors. Moreover, these compounds suppress mTORC1-mediated S6K activation, thereby blocking a negative feedback loop, leading to activation of mitogenic pathways promoting cell survival and growth. Consequently, mTOR is a suitable target of therapy in cancer treatments. However, neither of these complexes is fully inhibited by the allosteric inhibitor rapamycin or its analogs. In recent years, new pharmacologic agents have been developed which can inhibit these complexes via ATP-binding mechanism, or dual inhibition of the canonical PI3-K/Akt/mTOR signaling pathway. These compounds include WYE-354, KU-003679, PI-103, Torin1, and Torin2, which can target both complexes or serve as a dual inhibitor for PI3-K/mTOR. This investigation describes the mechanism of action of pharmacological agents that effectively target mTORC1 and mTORC2 resulting in suppression of growth, proliferation, and migration of tumor and cancer stem cells.
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Affiliation(s)
| | - John L Gillick
- Department of Neurosurgery, New York Medical College, Valhalla, NY 10595, USA
| | - Jayson Neil
- Department of Neurosurgery, New York Medical College, Valhalla, NY 10595, USA
| | - Michael Tobias
- Department of Neurosurgery, New York Medical College, Valhalla, NY 10595, USA
| | - Zachary E Thwing
- Department of Neurosurgery, New York Medical College, Valhalla, NY 10595, USA
| | - Raj Murali
- Department of Neurosurgery, New York Medical College, Valhalla, NY 10595, USA
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Savada RP, Bonham-Smith PC. Differential transcript accumulation and subcellular localization of Arabidopsis ribosomal proteins. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2014; 223:134-45. [PMID: 24767123 DOI: 10.1016/j.plantsci.2014.03.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Revised: 03/12/2014] [Accepted: 03/14/2014] [Indexed: 05/26/2023]
Abstract
Arabidopsis cytoplasmic ribosomes are an assembly of four rRNAs and 81 ribosomal proteins (RPs). With only a single molecule of each RP incorporated into any given ribosome, an adequate level of each RP in the nucleolus is a prerequisite for efficient ribosome biogenesis. Using Genevestigator (microarray data analysis tool), we have studied transcript levels of 192 of the 254 Arabidopsis RP genes, as well as the sub-cellular localization of each of five two-member RP families, to identify the extent to which these two processes contribute to the nucleolar pool of RPs available for ribosome biogenesis. While transcript levels from different RP genes show up to a 300-fold difference across the RP population, this difference is drastically reduced to ∼8-fold when considering RP gene families. Under various stimuli, while the transcript level for most RP genes remains unchanged some show a significantly increased or decreased level. Subcellular localization studies in tobacco not only showed differential targeting of RPs to the cytoplasm, nucleus and nucleolus, but also differential nucleolar import rates. This degree of variation in gene regulation and subcellular localization of RPs hints at the possibility of extra-ribosomal functions for some RP isoforms.
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Affiliation(s)
- Raghavendra P Savada
- Department of Biology, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada
| | - Peta C Bonham-Smith
- Department of Biology, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada.
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Licona-Cassani C, Lim S, Marcellin E, Nielsen LK. Temporal dynamics of the Saccharopolyspora erythraea phosphoproteome. Mol Cell Proteomics 2014; 13:1219-30. [PMID: 24615062 DOI: 10.1074/mcp.m113.033951] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Actinomycetes undergo a dramatic reorganization of metabolic and cellular machinery during a brief period of growth arrest ("metabolic switch") preceding mycelia differentiation and the onset of secondary metabolite biosynthesis. This study explores the role of phosphorylation in coordinating the metabolic switch in the industrial actinomycete Saccharopolyspora erythraea. A total of 109 phosphopeptides from 88 proteins were detected across a 150-h fermentation using open-profile two-dimensional LC-MS proteomics and TiO(2) enrichment. Quantitative analysis of the phosphopeptides and their unphosphorylated cognates was possible for 20 pairs that also displayed constant total protein expression. Enzymes from central carbon metabolism such as putative acetyl-coenzyme A carboxylase, isocitrate lyase, and 2-oxoglutarate dehydrogenase changed dramatically in the degree of phosphorylation during the stationary phase, suggesting metabolic rearrangement for the reutilization of substrates and the production of polyketide precursors. In addition, an enzyme involved in cellular response to environmental stress, trypsin-like serine protease (SACE_6340/NC_009142_6216), decreased in phosphorylation during the growth arrest stage. More important, enzymes related to the regulation of protein synthesis underwent rapid phosphorylation changes during this stage. Whereas the degree of phosphorylation of ribonuclease Rne/Rng (SACE_1406/NC_009142_1388) increased during the metabolic switch, that of two ribosomal proteins, S6 (SACE_7351/NC_009142_7233) and S32 (SACE_6101/NC_009142_5981), dramatically decreased during this stage of the fermentation, supporting the hypothesis that ribosome subpopulations differentially regulate translation before and after the metabolic switch. Overall, we show the great potential of phosphoproteomic studies to explain microbial physiology and specifically provide evidence of dynamic protein phosphorylation events across the developmental cycle of actinomycetes.
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Affiliation(s)
- Cuauhtemoc Licona-Cassani
- §Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, St Lucia, QLD 4072, Australia
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Bursac S, Brdovcak MC, Donati G, Volarevic S. Activation of the tumor suppressor p53 upon impairment of ribosome biogenesis. Biochim Biophys Acta Mol Basis Dis 2013; 1842:817-30. [PMID: 24514102 DOI: 10.1016/j.bbadis.2013.08.014] [Citation(s) in RCA: 114] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 08/27/2013] [Indexed: 12/31/2022]
Abstract
Errors in ribosome biogenesis can result in quantitative or qualitative defects in protein synthesis and consequently lead to improper execution of the genetic program and the development of specific diseases. Evidence has accumulated over the last decade suggesting that perturbation of ribosome biogenesis triggers a p53-activating checkpoint signaling pathway, often referred to as the ribosome biogenesis stress checkpoint pathway. Although it was originally suggested that p53 has a prominent role in preventing diseases by monitoring the fidelity of ribosome biogenesis, recent work has demonstrated that p53 activation upon impairment of ribosome biogenesis also mediates pathological manifestations in humans. Perturbations of ribosome biogenesis can trigger a p53-dependent checkpoint signaling pathway independent of DNA damage and the tumor suppressor ARF through inhibitory interactions of specific ribosomal components with the p53 negative regulator, Mdm2. Here we review the recent advances made toward understanding of this newly-recognized checkpoint signaling pathway, its role in health and disease, and discuss possible future directions in this exciting research field. This article is part of a Special Issue entitled: Role of the Nucleolus in Human Disease.
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Affiliation(s)
- Sladana Bursac
- Department of Molecular Medicine and Biotechnology, School of Medicine, University of Rijeka, Braće Branchetta 20, 51000 Rijeka, Croatia
| | - Maja Cokaric Brdovcak
- Department of Molecular Medicine and Biotechnology, School of Medicine, University of Rijeka, Braće Branchetta 20, 51000 Rijeka, Croatia
| | - Giulio Donati
- Catalan Institute of Oncology, Bellvitge Biomedical Research Institute, Institut d'Investigacio' Biome'dica de Bellvitge (IDIBELL), 08908 Hospitalet de Llobregat, Barcelona, Spain
| | - Sinisa Volarevic
- Department of Molecular Medicine and Biotechnology, School of Medicine, University of Rijeka, Braće Branchetta 20, 51000 Rijeka, Croatia.
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Jhanwar-Uniyal M, Jeevan D, Neil J, Shannon C, Albert L, Murali R. Deconstructing mTOR complexes in regulation of Glioblastoma Multiforme and its stem cells. Adv Biol Regul 2013; 53:202-210. [PMID: 23231881 DOI: 10.1016/j.jbior.2012.10.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Accepted: 10/03/2012] [Indexed: 06/01/2023]
Abstract
Atypical serine-threonine kinase, mTOR (mechanistic target of Rapamycin; originally coined "mammalian TOR"), exists in two distinct multi-protein complexes termed mTOR complex 1 (mTORC1) and 2 (mTORC2), that senses and integrates a variety of environmental signals to control organism growth and homeostasis via non-overlapping signaling pathways. mTOR belongs to the phosphoinositide 3-kinase (PI3-K)-related kinase family, and an aberrant activation of mTORC1 is a potential contributing factor in uncontrolled cell growth, proliferation, and survival of tumor cells via specific effects on cap-dependent translation initiation, as well as in a more sustained manner via advancing ribosome biogenesis. It is thereby shown to be deregulated in numerous pathological conditions including cancer, obesity, type 2 diabetes, and neurodegeneration. Notably, mTOR itself, or through its substrates, regulates stem cell differentiation and maintenance of plueropotency. mTORC2 has been linked to cytoskeletal reorganization and cell survival through Akt, and is crucial to many divergent physiological functions, which may include stem cell regulation.
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Sami A, Karsy M. Targeting the PI3K/AKT/mTOR signaling pathway in glioblastoma: novel therapeutic agents and advances in understanding. Tumour Biol 2013; 34:1991-2002. [PMID: 23625692 DOI: 10.1007/s13277-013-0800-5] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 04/08/2013] [Indexed: 02/06/2023] Open
Abstract
Glioblastoma multiforme (GBM) is a grade IV astrocytoma with a median survival of 12 months despite current multi-modal treatment options. GBM is distinguished clinicopathologically into primary and secondary subtypes. Mutations of phosphatase and tensin homolog, and subsequent upregulation of the downstream protein kinase B/mammalian target of rapamycin (mTOR) signaling pathway, are commonly seen in primary GBM and less predominantly in secondary GBM. While investigations into targeted treatments of mTOR have been attempted, feedback regulation within the mTOR signaling pathway may account for therapeutic resistance. Currently, rapamycin analogs, dual-targeted mTOR complex 1 and 2 agents as well as dual mTOR and phosphatidylinositol-3 kinase-targeted agents are being investigated experimentally and in clinical trials. This review will discuss the experimental potential of these agents in the treatment of GBM and their current stage in the GBM drug pipeline. Knowledge obtained from the application of these agents can help in understanding the pathogenesis of GBM as well as delineating subsequent treatment strategies.
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Affiliation(s)
- Arshawn Sami
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA 30329, USA
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Smith GST, Samborska B, Hawley SP, Klaiman JM, Gillis TE, Jones N, Boggs JM, Harauz G. Nucleus-localized 21.5-kDa myelin basic protein promotes oligodendrocyte proliferation and enhances neurite outgrowth in coculture, unlike the plasma membrane-associated 18.5-kDa isoform. J Neurosci Res 2012. [PMID: 23184356 DOI: 10.1002/jnr.23166] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The classic myelin basic protein (MBP) family of central nervous system (CNS) myelin arises from transcription start site 3 of the Golli (gene of oligodendrocyte lineage) complex and comprises splice isoforms ranging in nominal molecular mass from 14 kDa to (full-length) 21.5 kDa. We have determined here a number of distinct functional differences between the major 18.5-kDa and minor 21.5-kDa isoforms of classic MBP with respect to oligodendrocyte (OLG) proliferation. We have found that, in contrast to 18.5-kDa MBP, 21.5-kDa MBP increases proliferation of early developmental immortalized N19-OLGs by elevating the levels of phosphorylated ERK1/2 and Akt1 kinases and of ribosomal protein S6. Coculture of N2a neuronal cells with N19-OLGs transfected with the 21.5-kDa isoform (or conditioned medium from), but not the 18.5-kDa isoform, caused the N2a cells to have increased neurite outgrowth and process branching complexity. These roles were dependent on subcellular localization of 21.5-kDa MBP to the nucleus and on the exon II-encoded segment, suggesting that the nuclear localization of early minor isoforms of MBP may play a crucial role in regulating and/or initiating myelin and neuronal development in the mammalian CNS.
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Affiliation(s)
- Graham S T Smith
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
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Mutual protection of ribosomal proteins L5 and L11 from degradation is essential for p53 activation upon ribosomal biogenesis stress. Proc Natl Acad Sci U S A 2012; 109:20467-72. [PMID: 23169665 DOI: 10.1073/pnas.1218535109] [Citation(s) in RCA: 161] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Impairment of ribosomal biogenesis can activate the p53 protein independently of DNA damage. The ability of ribosomal proteins L5, L11, L23, L26, or S7 to bind Mdm2 and inhibit its ubiquitin ligase activity has been suggested as a critical step in p53 activation under these conditions. Here, we report that L5 and L11 are particularly important for this response. Whereas several other newly synthesized ribosomal proteins are degraded by proteasomes upon inhibition of Pol I activity by actinomycin D, L5 and L11 accumulate in the ribosome-free fraction where they bind to Mdm2. This selective accumulation of free L5 and L11 is due to their mutual protection from proteasomal degradation. Furthermore, the endogenous, newly synthesized L5 and L11 continue to be imported into nucleoli even after nucleolar disruption and colocalize with Mdm2, p53, and promyelocytic leukemia protein. This suggests that the disrupted nucleoli may provide a platform for L5- and L11-dependent p53 activation, implying a role for the nucleolus in p53 activation by ribosomal biogenesis stress. These findings may have important implications with respect to understanding the pathogenesis of diseases caused by impaired ribosome biogenesis.
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Horos R, von Lindern M. Molecular mechanisms of pathology and treatment in Diamond Blackfan Anaemia. Br J Haematol 2012; 159:514-27. [DOI: 10.1111/bjh.12058] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Fumagalli S, Ivanenkov VV, Teng T, Thomas G. Suprainduction of p53 by disruption of 40S and 60S ribosome biogenesis leads to the activation of a novel G2/M checkpoint. Genes Dev 2012; 26:1028-40. [PMID: 22588717 DOI: 10.1101/gad.189951.112] [Citation(s) in RCA: 156] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Impairment of ribosome biogenesis leads to p53 induction and cell cycle arrest, a checkpoint involved in human disease. Induction of p53 is attributed to the binding and inhibition of human double minute 2 (Hdm2) by a subset of ribosomal proteins (RPs): RPS7, RPL5, RPL11, and RPL23. However, we found that only RPL11 or RPL5, in a mutually dependent manner, elicit this response. We show that depletion of RPS7 or RPL23, like depletion of other RPs, except for RPL11 and RPL5, induces a p53 response and that the effects of RPS7 and RPL23 on p53 induction reported earlier may be ascribed to inhibition of global translation. Moreover, we made the surprising observation that codepletion of two essential RPs, one from each subunit, but not the same subunit, leads to suprainduction of p53. This led to the discovery that the previously proposed RPL11-dependent mechanism of p53 induction, thought to be caused by abrogation of 40S biogenesis and continued 60S biogenesis, is still operating, despite abrogation of 60S biogenesis. This response leads to both a G1 block and a novel G2/M block not observed when disrupting either subunit alone. Thus, induction of p53 is mediated by distinct mechanisms, with the data pointing to an essential role for ribosomal subunits beyond translation.
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Affiliation(s)
- Stefano Fumagalli
- Division of Hematology and Oncology, Department of Internal Medicine, College of Medicine, Metabolic Diseases Institute, University of Cincinnati, Cincinnati, Ohio 45237, USA.
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Xing XL, Sha LZ, Yao Y, Shen Y, Wu LW, Xu Q. Spatio-temporal expression study of phosphorylated 70-kDa ribosomal S6 kinase (p70S6k) in mesial temporal lobe epilepsy. ACTA ACUST UNITED AC 2012; 27:7-10. [PMID: 22734207 DOI: 10.1016/s1001-9294(12)60015-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To determine the spatio-temporal expression of p70S6k activation in hippocampus in mesial temporal lobe epilepsy. METHODS Temporal lobe epilepsy model was established by stereotaxically unilateral and intrahippocampal injection of kainite acid (KA) in adult male C57BL/6 mice. Latent and chronic epileptogenesis were represented by mice 5 days after KA injection (n = 5) and mice 5 weeks after KA injection (n = 8), respectively. Control mice (n = 5) were injected with saline. Immunohistochemical assays were performed on brain sections of the mice. RESULTS Hippocampus both ipsilateral and contralateral to the KA injection displayed significantly up-regulated pS6 immunoreactivity in dispersed granule cells in 5-day and 5-week model mice. CONCLUSION The activation of p70S6k is mainly located in the dentate gyrus in KA-induced mouse model of temporal lobe epilepsy, indicating that the activation may be related with the disperse degree and hypertrophy of granule cells.
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Affiliation(s)
- Xiao-Liang Xing
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China
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Abstract
BACKGROUND The pathogenesis of tumour formation in the anterior pituitary including adrenocorticotropic hormone (ACTH)-secreting tumours has been intensively studied, but the causative mechanisms involved in pituitary cell transformation and tumourigenesis remain unclear. MATERIALS AND METHODS We searched PubMed on any paper related with molecular pathology of pituitary corticotroph adenomas and have included to this review all relevant references published up to June 2011. RESULTS Current studies increased our knowledge on the genetic basis of McCune-Albright syndrome (MAS), multiple endocrine neoplasia type 1 (MEN1), Carney complex (CNC), pituitary adenoma predisposition syndromes and tuberous sclerosis, but they have performed little to elucidate the causes of sporadic pituitary tumours including Cushing disease. DISCUSSION The aim of this review was to focus on the most recently published advances in the molecular pathology of corticotroph adenomas, which are presented in the context of changes seen in all types of pituitary adenomas, as well as in terms of corticotrophin-releasing hormone/ACTH/cortisol-specific pathways. CONCLUSIONS We would expect that over the next 5 years, more detailed analysis of inter-cellular communication pathways between pituitary cells, including the cadherins and integrins, and their interactions with other signalling pathways such as the β-catenin cascade will help elucidate what exactly goes awry in the formation of a benign corticotroph adenoma. This should in turn predict novel forms of pharmacological tumour control.
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Affiliation(s)
- Dorota Dworakowska
- Department of Endocrinology, Kings College Hospital, Denmark Hill, London, UK
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Cedrés S, Montero MA, Martinez P, Martinez A, Rodríguez-Freixinós V, Torrejon D, Gabaldon A, Salcedo M, Ramon Y Cajal S, Felip E. Exploratory analysis of activation of PTEN-PI3K pathway and downstream proteins in malignant pleural mesothelioma (MPM). Lung Cancer 2012; 77:192-8. [PMID: 22459204 DOI: 10.1016/j.lungcan.2012.02.022] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2011] [Revised: 02/10/2012] [Accepted: 02/29/2012] [Indexed: 11/30/2022]
Abstract
BACKGROUND Malignant pleural mesothelioma (MPM) is a highly aggressive neoplasm with elevated AKT/mTOR activity. We aimed to identify the expression and phosphorylation status of PTEN, PI3K and downstream signaling in MPM. PATIENTS AND METHODS Thirty consecutive MPM patients were identified. Clinical data analyzed: sex, age, histology, performance status (PS), white blood count, and neutrophil-lymphocyte ratio (NLR). Paraffin-embedded biopsies were used for immunohistochemical analysis. RESULTS Overexpression of PTEN, pMAPK, mTOR, pAKT, 4E-BP1, p4E-BP1, eIF-4E, peIF-4E, p-S6 and FOXO3a in MPM was found in 90%, 100%, 93.3%, 80%, 100%, 43.3%, 96.7%, 100%, 63.3% and 100% of tumors respectively. There was a significant correlation between low pS6 protein expression and longer progression free survival (PFS: 7.9 vs 5.6 months; p = 0.04) and overall survival (OS: 23.4 vs 5.6 months; p = 0.05). Patients with concomitant low expression of pS6 and p4E-BP1 and overexpression of FOXO3a had significantly better prognosis (34.6 vs 1.9 months; p = 0.004). In multivariate analysis, histology and NLR were independent prognostic factors (p = 0.02 and p = 0.04 respectively), but pS6 only showed a trend (p = 0.8). CONCLUSIONS This study shows PI3K pathway and downstream proteins in MPM are frequently activated and provides prognostic information. The role of PI3K pathway is worth of prospective validation in future studies on MPM.
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Affiliation(s)
- S Cedrés
- Medical Oncology Service/Vall d'Hebron University Hospital, Barcelona, Spain.
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A polymerase chain reaction-based methodology to detect gene doping. Eur J Appl Physiol 2011; 112:1527-36. [PMID: 21847575 DOI: 10.1007/s00421-011-2113-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2011] [Accepted: 07/29/2011] [Indexed: 10/17/2022]
Abstract
The non-therapeutic use of genes to enhance athletic performance (gene doping) is a novel threat to the world of sports. Skeletal muscle is a prime target of gene therapy and we asked whether we can develop a test system to produce and detect gene doping. Towards this end, we introduced a plasmid (pCMV-FAK, 3.8 kb, 50 μg) for constitutive expression of the chicken homologue for the regulator of muscle growth, focal adhesion kinase (FAK), via gene electro transfer in the anti-gravitational muscle, m. soleus, or gastrocnemius medialis of rats. Activation of hypertrophy signalling was monitored by assessing the ribosomal kinase p70S6K and muscle fibre cross section. Detectability of the introduced plasmid was monitored with polymerase chain reaction in deoxyribonucleic acids (DNA) from transfected muscle and serum. Muscle transfection with pCMV-FAK elevated FAK expression 7- and 73-fold, respectively, and increased mean cross section by 52 and 16% in targeted muscle fibres of soleus and gastrocnemius muscle 7 days after gene electro transfer. Concomitantly p70S6K content was increased in transfected soleus muscle (+110%). Detection of the exogenous plasmid sequence was possible in DNA and cDNA of muscle until 7 days after transfection, but not in serum except close to the site of plasmid deposition, 1 h after injection and surgery. The findings suggest that the reliable detection of gene doping in the immoral athlete is not possible unless a change in the current practice of tissue sampling is applied involving the collection of muscle biopsy close to the site of gene injection.
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Sankhala K, Giles FJ. Potential of mTOR inhibitors as therapeutic agents in hematological malignancies. Expert Rev Hematol 2011; 2:399-414. [PMID: 21082945 DOI: 10.1586/ehm.09.31] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Despite significant advances in the treatment of hematological malignancies over the last decade, morbidity and mortality from these disorders remain high. New discoveries in the pathogenesis of these malignancies have led to better understanding of these diseases and new thinking in drug development. mTOR is a downstream effector of the PI3K/Akt (protein kinase B) signaling pathway that mediates cell survival and proliferation and is known to be deregulated in many cancers. Preclinical activity of mTOR inhibitors has been very promising in various hematological malignancies. Rapamycin analogs with relatively favorable pharmaceutical properties, including temsirolimus (CCI-779), everolimus (RAD001) and deforolimus (AP23573), are under clinical evaluations in patients with hematologic malignancies. They have shown encouraging results thus far and a favorable toxicity profile. Their utility, mainly as cytostatic agents, needs to be further explored in combination with pre-existing chemotherapeutic agents for various hematological malignancies.
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Affiliation(s)
- Kamalesh Sankhala
- Institute for Drug Development, Cancer Therapy and Research Center, University of Texas Health Science Center at San Antonio, 7979 Wurzbach Road, San Antonio, TX 78229, USA.
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Dobashi Y, Suzuki S, Kimura M, Matsubara H, Tsubochi H, Imoto I, Ooi A. Paradigm of kinase-driven pathway downstream of epidermal growth factor receptor/Akt in human lung carcinomas. Hum Pathol 2011; 42:214-26. [DOI: 10.1016/j.humpath.2010.05.025] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2010] [Revised: 05/22/2010] [Accepted: 05/26/2010] [Indexed: 01/01/2023]
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Depletion of ribosomal protein L8 impairs Drosophila development and is associated with apoptosis. SCIENCE CHINA-LIFE SCIENCES 2010; 53:1092-7. [PMID: 21104369 DOI: 10.1007/s11427-010-4059-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2010] [Accepted: 04/20/2010] [Indexed: 10/18/2022]
Abstract
Ribosomal protein L8 is a component of the 60S subunit of the ribosome and is involved in protein synthesis but its role in Drosophila development is not well understood. We depleted L8 through RNA interference (RNAi) to examine its effects on fly development both in vivo and in vitro. The results demonstrated that L8 RNAi caused embryonic or first-larval lethality, delay of larval development, defects in eye and wing morphology, and dramatically reduced the number of S2 cells. This indicated that L8 plays a crucial role in Drosophila development. Acridine orange staining of the wing discs showed that apoptosis occurred when L8 was depleted, indicating that depletion of L8 is tightly connected to apoptosis. RT-PCR analyses of the transcription level of genes that are known to be key factors in apoptosis (p53, hid, reaper, dark, Dcp-1) and cell cycle regulation (cdc45, MCM3, cyclin B, incenp) in L8-deficient S2 cells, were consistent with their role in apoptosis induction and cell cycle arrest. These results indicate that depletion of L8 strongly impairs Drosophila development, and that this depletion is associated with cell proliferation arrest and apoptosis, in which p53 may play a central role.
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Arko L, Katsyv I, Park GE, Luan WP, Park JK. Experimental approaches for the treatment of malignant gliomas. Pharmacol Ther 2010; 128:1-36. [PMID: 20546782 PMCID: PMC2939300 DOI: 10.1016/j.pharmthera.2010.04.015] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Accepted: 04/28/2010] [Indexed: 12/13/2022]
Abstract
Malignant gliomas, which include glioblastomas and anaplastic astrocytomas, are the most common primary tumors of the brain. Over the past 30 years, the standard treatment for these tumors has evolved to include maximal safe surgical resection, radiation therapy and temozolomide chemotherapy. While the median survival of patients with glioblastomas has improved from 6 months to 14.6 months, these tumors continue to be lethal for the vast majority of patients. There has, however, been recent substantial progress in our mechanistic understanding of tumor development and growth. The translation of these genetic, epigenetic and biochemical findings into therapies that have been tested in clinical trials is the subject of this review.
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Affiliation(s)
- Leopold Arko
- Surgical and Molecular Neuro-oncology Unit, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD 20892, USA
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Chrostowski MK, McGonnigal BG, Stabila JP, Padbury JF. Role of the L-amino acid transporter-1 (LAT-1) in mouse trophoblast cell invasion. Placenta 2010; 31:528-34. [PMID: 20421131 DOI: 10.1016/j.placenta.2009.12.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2009] [Revised: 12/06/2009] [Accepted: 12/08/2009] [Indexed: 11/15/2022]
Abstract
LAT-1 (L-type amino acid transporter 1) is a system L, Na(+)-independent amino acid transporter responsible for transport of large neutral amino acids. Dysregulated expression of LAT-1 is characteristic of many primary human cancers and it's over expression is related to tumor invasion. LAT-1 is highly expressed in the trophoblast giant cells (TGCs) at the time of implantation. Since trophoblast giant cells are highly invasive during the process of endometrial implantation and placentation, LAT-1 may play a role in the invasive phenotype. Our objectives were to identify the effects of increased and decreased LAT-1 expression on mouse trophoblast invasion. We therefore examined the role of amino acid deprivation, pharmacologic blockade specific to leucine transport and gene silencing (siRNA) on LAT-1 expression and trophoblast cell invasion. We utilized mouse primary trophoblast stem (TS) cells. LAT-1 mRNA expression was quantified by real time qPCR, protein by Western blotting and cell invasion was measured in Transwell plates through Matrigel. Amino acid transport using uptake of tritiated leucine. Under limited leucine availability and/or pharmacologic blockage, LAT-1 gene expression was significantly increased, p<0.05. This was associated with a 3-fold increase in cell invasion, p<0.05. In contrast, following siRNA-mediated gene silencing decreased LAT-1 expression (both mRNA and protein) was associated with decreased cell invasion and decreased leucine uptake, p<0.05. Upregulation of LAT-1 gene expression via limited amino acid availability or following pharmacologic blockade of transport leads to an increase in mouse trophoblast stem cell invasiveness. Downregulation of LAT-1 expression via genetic silencing leads to inhibition of invasiveness. These results demonstrate that LAT-1 plays an important role in trophoblast invasion.
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Affiliation(s)
- M K Chrostowski
- Division of Biology and Medicine, Graduate Program in Pathobiology, Brown University, Providence, Rhode Island, USA
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Shigematsu H, Yoshida K, Sanada Y, Osada S, Takahashi T, Wada Y, Konishi K, Okada M, Fukushima M. Rapamycin enhances chemotherapy-induced cytotoxicity by inhibiting the expressions of TS and ERK in gastric cancer cells. Int J Cancer 2010; 126:2716-25. [PMID: 19856312 DOI: 10.1002/ijc.24990] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We have previously reported the synergistic cytotoxic effects of Docetaxel (TXT) and S-1 in gastric cancer in vitro and in vivo, and the combination regimen is now under phase III clinical trail. In this study, to elucidate whether the rapamycin, the inhibitor of the mTOR (mammalian target of rapamaycin), can enhance the potentiation of TXT and 5-fluorouracil (5-Fu) in gastric carcinoma cells. Rapamycin inhibited the growth of TMK-1, MKN-28, MKN-45 and MKN-74 cell lines by MTT assay, and it demonstrated the cytostatic effects as G1 arrest shown by flowcytometry. However, the cytotoxic effects of 5-Fu, TXT and cisplatin were enhanced by 2 to 4 times with the concomitant administration of rapamycin. To clarify the mechanism of the potentiation, the expression changes of the enzymes relating DNA metabolism and cell growth signal transduction pathways were examined by western blot analysis. Interestingly, the expression of thymidilate synthase was markedly decreased by the administration of rapamycin in TMK-1 cells in a time- and dose-dependent manner. Moreover, rapamycin decreased the phosphorylation of 4E-BP1, the phosphorylation of ERK1/2 and enhanced the phosphorylation of c-Jun NH2-terminal kinase, and the activation of caspase of apoptotic pathways in combination with TXT. These results strongly indicate that the mTOR inhibitor can enhance the potentiation of TXT and 5-Fu or S-1 and can serve as a new therapeutic tool for advanced and recurrent gastric cancer patients.
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Affiliation(s)
- Hideo Shigematsu
- Department of Surgical Oncology, Research Institute for Radiation Biology and Medicine, Hirsoshima University, Japan
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Kelly P, Bailey CL, Fueger PT, Newgard CB, Casey PJ, Kimple ME. Rap1 promotes multiple pancreatic islet cell functions and signals through mammalian target of rapamycin complex 1 to enhance proliferation. J Biol Chem 2010; 285:15777-85. [PMID: 20339002 DOI: 10.1074/jbc.m109.069112] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Recent studies have implicated Epac2, a guanine-nucleotide exchange factor for the Rap subfamily of monomeric G proteins, as an important regulator of insulin secretion from pancreatic beta-cells. Although the Epac proteins were originally identified as cAMP-responsive activators of Rap1 GTPases, the role of Rap1 in beta-cell biology has not yet been defined. In this study, we examined the direct effects of Rap1 signaling on beta-cell biology. Using the Ins-1 rat insulinoma line, we demonstrate that activated Rap1A, but not related monomeric G proteins, promotes ribosomal protein S6 phosphorylation. Using isolated rat islets, we show that this signaling event is rapamycin-sensitive, indicating that it is mediated by the mammalian target of rapamycin complex 1-p70 S6 kinase pathway, a known growth regulatory pathway. This newly defined beta-cell signaling pathway acts downstream of cAMP, in parallel with the stimulation of cAMP-dependent protein kinase, to drive ribosomal protein S6 phosphorylation. Activated Rap1A promotes glucose-stimulated insulin secretion, islet cell hypertrophy, and islet cell proliferation, the latter exclusively through mammalian target of rapamycin complex 1, suggesting that Rap1 is an important regulator of beta-cell function. This newly defined signaling pathway may yield unique targets for the treatment of beta-cell dysfunction in diabetes.
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Affiliation(s)
- Patrick Kelly
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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Arroyo JA, Brown LD, Galan HL. Placental mammalian target of rapamycin and related signaling pathways in an ovine model of intrauterine growth restriction. Am J Obstet Gynecol 2009; 201:616.e1-7. [PMID: 19800600 DOI: 10.1016/j.ajog.2009.07.031] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Revised: 06/13/2009] [Accepted: 07/14/2009] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Both phosphorylated (p) mammalian target of rapamycin (mTOR) and protein S6 kinase 1 (p70S6K) are known to regulate protein synthesis and are affected during intrauterine growth restriction (IUGR). We studied the mTOR pathway during hyperthermia (HT)-induced IUGR in sheep. STUDY DESIGN Beginning at 40 days gestational age, 4 ewes were exposed to HT for 55 days and 4 were exposed for 80 days to induce IUGR. Western blot analyses were performed for mTOR, p70S6K, 4E-binding protein 1, extracellularly regulated kinase (ERK), and AKT. RESULTS HT animals showed: smaller fetuses and placentas near term; reduced placental weight at midgestation; increased p-mTOR, p-ERK, and p-AKT; decreased p70S6K in the near-term cotyledons; decreased p- p70S6K; and increased p-ERK in the caruncles (maternal) near term. CONCLUSION Near-term IUGR ovine cotyledons showed up-regulation of p-mTOR, whereas p70S6K was decreased. This suggests that the changes in placental mTOR signaling proteins could be driven by the fetal stress observed near term in this model of IUGR.
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Affiliation(s)
- Juan A Arroyo
- Division of Perinatal Medicine, Department of Obstetrics and Gynecology, University of Colorado Denver and Health Sciences Center, Aurora, CO 80045, USA.
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Zhao XF, Gartenhaus RB. Phospho-p70S6K and cdc2/cdk1 as therapeutic targets for diffuse large B-cell lymphoma. Expert Opin Ther Targets 2009; 13:1085-93. [PMID: 19614561 DOI: 10.1517/14728220903103833] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
p70S6K/p85S6K and cdc2/cdk1 are members of the serine/threonine protein kinase family. p70S6K/p85S6K is one of the downstream effectors of the PI3K/Akt/mTOR signal transduction pathway. It phosphorylates S6 protein of 40S ribosomal subunit and thus functions in protein synthesis and cell growth. cdc2/cdk1 is a cyclin-dependent protein kinase that controls the cell cycle entry from G2 to M phase. Overexpression of phospho-p70S6K and cdc2/cdk1 has recently been identified in the majority of diffuse large B-cell lymphoma (DLBCL) specimens. Combination of small molecules that target phosphorylation of p70S6K and cdc2/cdk1 synergistically induced cell apoptosis and cell cycle G1 and G2 arrest, suggesting that they are potential molecular targets for DLBCL therapy. This review will summarize recent advances in the study of phospho-p70S6K and cdc2/cdk1 as molecular markers and therapeutic targets for DLBCL. We propose that multilevel inhibition of the PI3K/Akt/mTOR pathway and double brake at the G1 and G2 phases of the cell cycle progression are effective strategies in treating DLBCL that overexpress phospho-p70S6K and cdc2/cdk1.
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Affiliation(s)
- Xianfeng Frank Zhao
- University of Maryland, Marlene and Stewart Greenebaum Cancer Center, Baltimore, Maryland 21201, USA.
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