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Wolfe AR, Cui T, Baie S, Corrales-Guerrero S, Webb A, Castro-Aceituno V, Shyu DL, Karasinska JM, Topham JT, Renouf DJ, Schaeffer DF, Halloran M, Packard R, Robb R, Chen W, Denko N, Lisanti M, Thompson TC, Frank P, Williams TM. Nutrient scavenging-fueled growth in pancreatic cancer depends on caveolae-mediated endocytosis under nutrient-deprived conditions. Sci Adv 2024; 10:eadj3551. [PMID: 38427741 PMCID: PMC10906919 DOI: 10.1126/sciadv.adj3551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 01/26/2024] [Indexed: 03/03/2024]
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is characterized by its nutrient-scavenging ability, crucial for tumor progression. Here, we investigated the roles of caveolae-mediated endocytosis (CME) in PDAC progression. Analysis of patient data across diverse datasets revealed a strong association of high caveolin-1 (Cav-1) expression with higher histologic grade, the most aggressive PDAC molecular subtypes, and worse clinical outcomes. Cav-1 loss markedly promoted longer overall and tumor-free survival in a genetically engineered mouse model. Cav-1-deficient tumor cell lines exhibited significantly reduced proliferation, particularly under low nutrient conditions. Supplementing cells with albumin rescued the growth of Cav-1-proficient PDAC cells, but not in Cav-1-deficient PDAC cells under low glutamine conditions. In addition, Cav-1 depletion led to significant metabolic defects, including decreased glycolytic and mitochondrial metabolism, and downstream protein translation signaling pathways. These findings highlight the crucial role of Cav-1 and CME in fueling pancreatic tumorigenesis, sustaining tumor growth, and promoting survival through nutrient scavenging.
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Affiliation(s)
- Adam R. Wolfe
- Department of Radiation Oncology, The University of Arkansas for Medical Sciences, The Winthrop P. Rockefeller Cancer Institute, Little Rock, AR, USA
| | - Tiantian Cui
- Department of Radiation Oncology, City of Hope, Duarte, CA, USA
| | - Sooin Baie
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Arthur G. James Comprehensive Cancer Center and Richard J. Solove Research Institute, Columbus, OH, USA
| | | | - Amy Webb
- Department of Biomedical Informatics, The Ohio State University, Columbus, OH, USA
| | | | - Duan-Liang Shyu
- Department of Radiation Oncology, The Ohio State University Wexner Medical Center, Arthur G. James Comprehensive Cancer Center and Richard J. Solove Research Institute, Columbus, OH, USA
| | | | | | - Daniel J. Renouf
- Pancreas Centre BC, Vancouver, BC, Canada
- Department of Medical Oncology, BC Cancer, Vancouver, BC, Canada
| | - David F. Schaeffer
- Pancreas Centre BC, Vancouver, BC, Canada
- Department of Pathology and Laboratory Medicine, Vancouver General Hospital, Vancouver, BC, Canada
| | - Megan Halloran
- Department of Radiation Oncology, The Ohio State University Wexner Medical Center, Arthur G. James Comprehensive Cancer Center and Richard J. Solove Research Institute, Columbus, OH, USA
| | - Rebecca Packard
- Department of Radiation Oncology, The Ohio State University Wexner Medical Center, Arthur G. James Comprehensive Cancer Center and Richard J. Solove Research Institute, Columbus, OH, USA
| | - Ryan Robb
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Wei Chen
- Department of Pathology, The Ohio State University Wexner Medical Center, Arthur G. James Comprehensive Cancer Center and Richard J. Solove Research Institute, Columbus, OH, USA
| | - Nicholas Denko
- Department of Radiation Oncology, The Ohio State University Wexner Medical Center, Arthur G. James Comprehensive Cancer Center and Richard J. Solove Research Institute, Columbus, OH, USA
| | - Michael Lisanti
- Translational Medicine, University of Salford, Greater Manchester M5 4WT, UK
- Lunella Biotech, Inc., 145 Richmond Road, Ottawa, ON K1Z 1A1, Canada
| | - Timothy C. Thompson
- Department of Genitourinary Medical Oncology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX, USA
| | - Philippe Frank
- SGS France, Health & Nutrition, Saint-Benoît, France
- N2C, Nutrition Growth and Cancer, Faculté de Médecine, Université de Tours, Inserm, UMR, 1069 Tours, France
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Frappaolo A, Giansanti MG. Using Drosophila melanogaster to Dissect the Roles of the mTOR Signaling Pathway in Cell Growth. Cells 2023; 12:2622. [PMID: 37998357 PMCID: PMC10670727 DOI: 10.3390/cells12222622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 11/10/2023] [Accepted: 11/11/2023] [Indexed: 11/25/2023] Open
Abstract
The evolutionarily conserved target of rapamycin (TOR) serine/threonine kinase controls eukaryotic cell growth, metabolism and survival by integrating signals from the nutritional status and growth factors. TOR is the catalytic subunit of two distinct functional multiprotein complexes termed mTORC1 (mechanistic target of rapamycin complex 1) and mTORC2, which phosphorylate a different set of substrates and display different physiological functions. Dysregulation of TOR signaling has been involved in the development and progression of several disease states including cancer and diabetes. Here, we highlight how genetic and biochemical studies in the model system Drosophila melanogaster have been crucial to identify the mTORC1 and mTORC2 signaling components and to dissect their function in cellular growth, in strict coordination with insulin signaling. In addition, we review new findings that involve Drosophila Golgi phosphoprotein 3 in regulating organ growth via Rheb-mediated activation of mTORC1 in line with an emerging role for the Golgi as a major hub for mTORC1 signaling.
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Affiliation(s)
- Anna Frappaolo
- Istituto di Biologia e Patologia Molecolari del CNR, c/o Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, 00185 Roma, Italy
| | - Maria Grazia Giansanti
- Istituto di Biologia e Patologia Molecolari del CNR, c/o Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, 00185 Roma, Italy
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Hong PP, Li C, Niu GJ, Zhao XF, Wang JX. White spot syndrome virus directly activates mTORC1 signaling to facilitate its replication via polymeric immunoglobulin receptor-mediated infection in shrimp. PLoS Pathog 2022; 18:e1010808. [PMID: 36067252 PMCID: PMC9481175 DOI: 10.1371/journal.ppat.1010808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 09/16/2022] [Accepted: 08/11/2022] [Indexed: 11/19/2022] Open
Abstract
Previous studies have shown that the mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway has antiviral functions or is beneficial for viral replication, however, the detail mechanisms by which mTORC1 enhances viral infection remain unclear. Here, we found that proliferation of white spot syndrome virus (WSSV) was decreased after knockdown of mTor (mechanistic target of rapamycin) or injection inhibitor of mTORC1, rapamycin, in Marsupenaeus japonicus, which suggests that mTORC1 is utilized by WSSV for its replication in shrimp. Mechanistically, WSSV infects shrimp by binding to its receptor, polymeric immunoglobulin receptor (pIgR), and induces the interaction of its intracellular domain with Calmodulin. Calmodulin then promotes the activation of protein kinase B (AKT) by interaction with the pleckstrin homology (PH) domain of AKT. Activated AKT phosphorylates mTOR and results in the activation of the mTORC1 signaling pathway to promote its downstream effectors, ribosomal protein S6 kinase (S6Ks), for viral protein translation. Moreover, mTORC1 also phosphorylates eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), which will result in the separation of 4EBP1 from eukaryotic translation initiation factor 4E (eIF4E) for the translation of viral proteins in shrimp. Our data revealed a novel pathway for WSSV proliferation in shrimp and indicated that mTORC1 may represent a potential clinical target for WSSV control in shrimp aquaculture. White spot syndrome virus (WSSV) is the causative pathogen of white spot disease (WSD) and represents the most destructive viral disease of shrimp. The virus has evolved various strategies to escape from host defenses or exploit host biological pathways for its reproduction. Studies on viral immune-escape mechanisms can provide new strategies for disease prevention and control in shrimp aquaculture. Mechanistic target of rapamycin (mTOR) plays a central role in the regulation of cell growth and metabolism, which nucleates two distinct protein complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2) with diverse functions at different levels of the signaling pathway. mTORC1 is reported to be exploited by viruses in their reproduction. However, the detail mechanism remains unclear. In this study, we identified a new mechanism of mTOR being hijacked by WSSV in shrimp (Marsupenaeus japonicus). WSSV infects shrimp by its receptor, pIgR and induces the interaction of the intracellular domain of pIgR with Calmodulin. Calmodulin subsequently promotes the activation of AKT by interaction with the pleckstrin homology domain of the kinase. Activated AKT phosphorylates mTOR and results in the activation of the mTORC1 signaling pathway to promote its downstream effectors, S6Ks, for viral protein synthesis. Moreover, mTORC1 also phosphorylates 4EBP1, which results in the separation of 4EBP1 from eIF4E for the translation of viral proteins in shrimp. Our study reveals a novel strategy for WSSV proliferation in shrimp and indicates that the components of mTORC1 may represent potential clinical targets for WSSV control in shrimp aquaculture.
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Affiliation(s)
- Pan-Pan Hong
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, Shandong, China
| | - Cang Li
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, Shandong, China
| | - Guo-Juan Niu
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, Shandong, China
| | - Xiao-Fan Zhao
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, Shandong, China
| | - Jin-Xing Wang
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, Shandong, China
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong, China
- * E-mail:
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Abstract
Genetic evidence in living organisms from yeast to plants and animals, including humans, unquestionably identifies the Target Of Rapamycin kinase (TOR or mTOR for mammalian/mechanistic) signal transduction pathway as a master regulator of growth through the control of cell size and cell number. Among the mTOR targets, the activation of p70 S6 kinase 1 (S6K1) is exquisitely sensitive to nutrient availability and rapamycin inhibition. Of note, in vivo analysis of mutant flies and mice reveals that S6K1 predominantly regulates cell size versus cell proliferation. Here we review the putative mechanisms of S6K1 action on cell size by considering the main functional categories of S6K1 targets: substrates involved in nucleic acid and protein synthesis, fat mass accumulation, retrograde control of insulin action, senescence program and cytoskeleton organization. We discuss how S6K1 may be involved in the observed interconnection between cell size, regenerative and ageing responses.
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Affiliation(s)
| | - Mario Pende
- *Correspondence: Stefano Fumagalli, ; Mario Pende,
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Yi YW, You KS, Park JS, Lee SG, Seong YS. Ribosomal Protein S6: A Potential Therapeutic Target against Cancer? Int J Mol Sci 2021; 23:ijms23010048. [PMID: 35008473 PMCID: PMC8744729 DOI: 10.3390/ijms23010048] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 12/19/2021] [Accepted: 12/20/2021] [Indexed: 12/12/2022] Open
Abstract
Ribosomal protein S6 (RPS6) is a component of the 40S small ribosomal subunit and participates in the control of mRNA translation. Additionally, phospho (p)-RPS6 has been recognized as a surrogate marker for the activated PI3K/AKT/mTORC1 pathway, which occurs in many cancer types. However, downstream mechanisms regulated by RPS6 or p-RPS remains elusive, and the therapeutic implication of RPS6 is underappreciated despite an approximately half a century history of research on this protein. In addition, substantial evidence from RPS6 knockdown experiments suggests the potential role of RPS6 in maintaining cancer cell proliferation. This motivates us to investigate the current knowledge of RPS6 functions in cancer. In this review article, we reviewed the current information about the transcriptional regulation, upstream regulators, and extra-ribosomal roles of RPS6, with a focus on its involvement in cancer. We also discussed the therapeutic potential of RPS6 in cancer.
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Affiliation(s)
- Yong Weon Yi
- Department of Biochemistry, College of Medicine, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea; (Y.W.Y.); (K.S.Y.); (J.-S.P.)
- Department of Nanobiomedical Science, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea
| | - Kyu Sic You
- Department of Biochemistry, College of Medicine, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea; (Y.W.Y.); (K.S.Y.); (J.-S.P.)
- Graduate School of Convergence Medical Science, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea
| | - Jeong-Soo Park
- Department of Biochemistry, College of Medicine, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea; (Y.W.Y.); (K.S.Y.); (J.-S.P.)
| | - Seok-Geun Lee
- Graduate School, Kyung Hee University, Seoul 02447, Korea
- Correspondence: (S.-G.L.); (Y.-S.S.); Tel.: +82-2-961-2355 (S.-G.L.); +82-41-550-3875 (Y.-S.S.); Fax: +82-2-961-9623 (S.-G.L.)
| | - Yeon-Sun Seong
- Department of Biochemistry, College of Medicine, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea; (Y.W.Y.); (K.S.Y.); (J.-S.P.)
- Graduate School of Convergence Medical Science, Dankook University, Cheonan 31116, Chungcheongnam-do, Korea
- Correspondence: (S.-G.L.); (Y.-S.S.); Tel.: +82-2-961-2355 (S.-G.L.); +82-41-550-3875 (Y.-S.S.); Fax: +82-2-961-9623 (S.-G.L.)
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Gerstenecker S, Haarer L, Schröder M, Kudolo M, Schwalm MP, Wydra V, Serafim RAM, Chaikuad A, Knapp S, Laufer S, Gehringer M. Discovery of a Potent and Highly Isoform-Selective Inhibitor of the Neglected Ribosomal Protein S6 Kinase Beta 2 (S6K2). Cancers (Basel) 2021; 13:cancers13205133. [PMID: 34680283 PMCID: PMC8534050 DOI: 10.3390/cancers13205133] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 10/04/2021] [Accepted: 10/08/2021] [Indexed: 12/27/2022] Open
Abstract
Simple Summary The two human p70 ribosomal S6 kinases, S6K1 and S6K2, have been associated with a variety of cellular processes and human pathologies, especially cancer. Thus far, only S6K1 was thoroughly studied and selectively addressed by small molecule inhibitors. Despite growing evidence suggesting S6K2 as a promising anticancer target, this isoform has been severely neglected, which can partly be attributed to the lack of isoform-selective inhibitors to study its function. By exploiting a cysteine residue exclusive to S6K2, we were able to generate the first known isoform-selective S6K2 inhibitor. Besides its excellent selectivity against S6K1 and other human kinases, the compound showed weak intrinsic reactivity and promising in vitro metabolic stability. Our proof-of-concept study provides a basis for the development of high quality S6K2 chemical probes to validate this kinase as a target for therapeutic interventions. Abstract The ribosomal protein S6 kinase beta 2 (S6K2) is thought to play an important role in malignant cell proliferation, but is understudied compared to its closely related homolog S6 kinase beta 1 (S6K1). To better understand the biological function of S6K2, chemical probes are needed, but the high similarity between S6K2 and S6K1 makes it challenging to selectively address S6K2 with small molecules. We were able to design the first potent and highly isoform-specific S6K2 inhibitor from a known S6K1-selective inhibitor, which was merged with a covalent inhibitor engaging a cysteine located in the hinge region in the fibroblast growth factor receptor kinase (FGFR) 4 via a nucleophilic aromatic substitution (SNAr) reaction. The title compound shows a high selectivity over kinases with an equivalently positioned cysteine, as well as in a larger kinase panel. A good stability towards glutathione and Nα-acetyl lysine indicates a non-promiscuous reactivity pattern. Thus, the title compound represents an important step towards a high-quality chemical probe to study S6K2-specific signaling.
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Affiliation(s)
- Stefan Gerstenecker
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmaceutical Sciences, Eberhard Karls University Tübingen, 72076 Tübingen, Germany; (S.G.); (L.H.); (M.K.); (V.W.); (R.A.M.S.); (S.L.)
| | - Lisa Haarer
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmaceutical Sciences, Eberhard Karls University Tübingen, 72076 Tübingen, Germany; (S.G.); (L.H.); (M.K.); (V.W.); (R.A.M.S.); (S.L.)
| | - Martin Schröder
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Pharmaceutical Chemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany; (M.S.); (M.P.S.); (A.C.); (S.K.)
- Structural Genomics Consortium, Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, 60438 Frankfurt, Germany
| | - Mark Kudolo
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmaceutical Sciences, Eberhard Karls University Tübingen, 72076 Tübingen, Germany; (S.G.); (L.H.); (M.K.); (V.W.); (R.A.M.S.); (S.L.)
| | - Martin P. Schwalm
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Pharmaceutical Chemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany; (M.S.); (M.P.S.); (A.C.); (S.K.)
- Structural Genomics Consortium, Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, 60438 Frankfurt, Germany
| | - Valentin Wydra
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmaceutical Sciences, Eberhard Karls University Tübingen, 72076 Tübingen, Germany; (S.G.); (L.H.); (M.K.); (V.W.); (R.A.M.S.); (S.L.)
| | - Ricardo A. M. Serafim
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmaceutical Sciences, Eberhard Karls University Tübingen, 72076 Tübingen, Germany; (S.G.); (L.H.); (M.K.); (V.W.); (R.A.M.S.); (S.L.)
| | - Apirat Chaikuad
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Pharmaceutical Chemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany; (M.S.); (M.P.S.); (A.C.); (S.K.)
- Structural Genomics Consortium, Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, 60438 Frankfurt, Germany
| | - Stefan Knapp
- Department of Biochemistry, Chemistry and Pharmacy, Institute for Pharmaceutical Chemistry, Goethe University Frankfurt, 60438 Frankfurt, Germany; (M.S.); (M.P.S.); (A.C.); (S.K.)
- Structural Genomics Consortium, Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, 60438 Frankfurt, Germany
- German Translational Cancer Network (DKTK) Site Frankfurt/Mainz, Frankfurt Cancer Institute (FCI), 60596 Frankfurt, Germany
| | - Stefan Laufer
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmaceutical Sciences, Eberhard Karls University Tübingen, 72076 Tübingen, Germany; (S.G.); (L.H.); (M.K.); (V.W.); (R.A.M.S.); (S.L.)
- Cluster of Excellence iFIT (EXC 2180) ‘Image-Guided & Functionally Instructed Tumor Therapies’, Eberhard Karls University Tübingen, 72076 Tübingen, Germany
- Tübingen Center for Academic Drug Discovery, Eberhard Karls University Tübingen, 72076 Tübingen, Germany
| | - Matthias Gehringer
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmaceutical Sciences, Eberhard Karls University Tübingen, 72076 Tübingen, Germany; (S.G.); (L.H.); (M.K.); (V.W.); (R.A.M.S.); (S.L.)
- Cluster of Excellence iFIT (EXC 2180) ‘Image-Guided & Functionally Instructed Tumor Therapies’, Eberhard Karls University Tübingen, 72076 Tübingen, Germany
- Correspondence: ; Tel.: +49-7071-29-74582
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Jiang SL, Mo JL, Peng J, Lei L, Yin JY, Zhou HH, Liu ZQ, Hong WX. Targeting translation regulators improves cancer therapy. Genomics 2020; 113:1247-1256. [PMID: 33189778 DOI: 10.1016/j.ygeno.2020.11.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 10/14/2020] [Accepted: 11/11/2020] [Indexed: 02/07/2023]
Abstract
Deregulation of protein synthesis may be involved in multiple aspects of cancer, such as gene expression, signal transduction and drive specific cell biological responses, resulting in promoting cancer growth, invasion and metastasis. Study the molecular mechanisms about translational control may help us to find more effective anti-cancer drugs and develop novel therapeutic opportunities. Recently, the researchers had focused on targeting translational machinery to overcome cancer, and various small molecular inhibitors targeting translation factors or pathways have been tested in clinical trials and exhibited improving outcomes in several cancer types. There is no doubt that an insight into the class of translation regulation protein would provide new target for pharmacologic intervention and further provide opportunities to develop novel anti-tumor therapeutic interventions. In this review, we summarized the developments of translational control in cancer survival and progression et al, and highlighted the therapeutic approach targeted translation regulation to overcome the cancer.
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Affiliation(s)
- Shi-Long Jiang
- Department of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, and National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, PR China; Institute of Clinical Pharmacology, Engineering Research Center for applied Technology of Pharmacogenomics of Ministry of Education, Central South University, Changsha 410078, PR China
| | - Jun-Luan Mo
- Department of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, and National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, PR China; Institute of Clinical Pharmacology, Engineering Research Center for applied Technology of Pharmacogenomics of Ministry of Education, Central South University, Changsha 410078, PR China; Shenzhen Center for Chronic Disease Control and Prevention, Shenzhen 518020, PR China
| | - Ji Peng
- Shenzhen Center for Chronic Disease Control and Prevention, Shenzhen 518020, PR China
| | - Lin Lei
- Shenzhen Center for Chronic Disease Control and Prevention, Shenzhen 518020, PR China
| | - Ji-Ye Yin
- Department of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, and National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, PR China; Institute of Clinical Pharmacology, Engineering Research Center for applied Technology of Pharmacogenomics of Ministry of Education, Central South University, Changsha 410078, PR China
| | - Hong-Hao Zhou
- Department of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, and National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, PR China; Institute of Clinical Pharmacology, Engineering Research Center for applied Technology of Pharmacogenomics of Ministry of Education, Central South University, Changsha 410078, PR China
| | - Zhao-Qian Liu
- Department of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, and National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, PR China; Institute of Clinical Pharmacology, Engineering Research Center for applied Technology of Pharmacogenomics of Ministry of Education, Central South University, Changsha 410078, PR China.
| | - Wen-Xu Hong
- Shenzhen Center for Chronic Disease Control and Prevention, Shenzhen 518020, PR China.
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Sridharan S, Basu A. Distinct Roles of mTOR Targets S6K1 and S6K2 in Breast Cancer. Int J Mol Sci 2020; 21:E1199. [PMID: 32054043 DOI: 10.3390/ijms21041199] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Revised: 02/06/2020] [Accepted: 02/07/2020] [Indexed: 12/12/2022] Open
Abstract
The mechanistic target of rapamycin (mTOR) is a master regulator of protein translation, metabolism, cell growth and proliferation. It forms two complexes, mTOR complex 1 (mTORC1) and 2 (mTORC2). mTORC1 is frequently deregulated in many cancers, including breast cancer, and is an important target for cancer therapy. The immunosuppressant drug rapamycin and its analogs that inhibit mTOR are currently being evaluated for their potential as anti-cancer agents, albeit with limited efficacy. mTORC1 mediates its function via its downstream targets 40S ribosomal S6 kinases (S6K) and eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1). There are two homologs of S6K: S6K1 and S6K2. Most of the earlier studies focused on S6K1 rather than S6K2. Because of their high degree of structural homology, it was generally believed that they behave similarly. Recent studies suggest that while they may share some functions, they may also exhibit distinct or even opposite functions. Both homologs have been implicated in breast cancer, although how they contribute to breast cancer may differ. The purpose of this review article is to compare and contrast the expression, structure, regulation and function of these two S6K homologs in breast cancer.
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Zhang N, Ma S. Research Progress of 70 kDa Ribosomal Protein S6 Kinase (P70S6K) Inhibitors as Effective Therapeutic Tools for Obesity, Type II Diabetes and Cancer. Curr Med Chem 2020; 27:4699-4719. [PMID: 31942845 DOI: 10.2174/0929867327666200114113139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 10/06/2019] [Accepted: 01/05/2020] [Indexed: 01/07/2023]
Abstract
At present, diseases such as obesity, type Ⅱ diabetes and cancer have brought serious health problems, which are closely related to mTOR pathway. 70 kDa ribosomal protein S6 kinase (p70S6K), as a significant downstream effector of mTOR, mediates protein synthesis, RNA processing, glucose homeostasis, cell growth and apoptosis. Inhibiting the function of p70S6K can reduce the risk of obesity which helps to treat dyslipidemia, enhance insulin sensitivity, and extend the life span of mammals. Therefore, p70S6K has become a potential target for the treatment of these diseases. So far, except for the first p70S6K specific inhibitor PF-4708671 developed by Pfizer and LY2584702 developed by Lilai, all of them are in preclinical research. This paper briefly introduces the general situation of p70S6K and reviews their inhibitors in recent years, which are mainly classified into two categories: natural compounds and synthetic compounds. In particular, their inhibitory activities, structure-activity relationships (SARs) and mechanisms are highlighted.
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Affiliation(s)
- Na Zhang
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education) School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, Jinan 250012, China
| | - Shutao Ma
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education) School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, Jinan 250012, China
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10
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Meneguello L, Barbosa NM, Pereira KD, Proença ARG, Tamborlin L, Simabuco FM, Iwai LK, Zanelli CF, Valentini SR, Luchessi AD. The polyproline-motif of S6K2: eIF5A translational dependence and importance for protein-protein interactions. J Cell Biochem 2019; 120:6015-6025. [PMID: 30320934 DOI: 10.1002/jcb.27888] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 09/20/2018] [Indexed: 12/18/2022]
Abstract
Ribosomal S6 kinase 1 (S6K1) and S6K2 proteins are effectors of the mammalian target of rapamycin complex 1 pathway, which control the process of protein synthesis in eukaryotes. S6K2 is associated with tumor progression and has a conserved C-terminus polyproline rich motif predicted to be important for S6K2 interactions. It is noteworthy that the translation of proteins containing sequential prolines has been proposed to be dependent of eukaryotic translation initiation factor 5A (eIF5A) translation factor. Therefore, we investigated the importance of polyproline-rich region of the S6K2 for its intrinsic phosphorylation activity, protein-protein interaction and eIF5A role in S6K2 translation. In HeLa cell line, replacing S6K2 polyproline by the homologous S6K1-sequence did not affect its kinase activity and the S6K2 endogenous content was maintained after eIF5A gene silencing, even after near complete depletion of eIF5A protein. Moreover, no changes in S6K2 transcript content was observed, ruling out the possibility of compensatory regulation by increasing the mRNA content. However, in the budding yeast model, we observed that S6K2 production was impaired when compared with S6K2∆Pro, after reduction of eIF5A protein content. These results suggest that although the polyproline region of S6K2 is capable of generating ribosomal stalling, the depletion of eIF5A in HeLa cells seems to be insufficient to cause an expressive decrease in the content of endogenous S6K2. Finally, coimmunoprecipitation assays revealed that the replacement of the polyproline motif of S6K2 alters its interactome and impairs its interaction with RPS6, a key modulator of ribosome activity. These results evidence the importance of S6K2 polyproline motif in the context of S6Ks function.
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Affiliation(s)
- Leticia Meneguello
- Laboratory of Biotechnology, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
- Institute of Biosciences, Department of Biology, São Paulo State University (UNESP), Rio Claro, Brazil
| | - Natália M Barbosa
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University (UNESP), Araraquara, Brazil
| | - Karina D Pereira
- Laboratory of Biotechnology, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
- Institute of Biosciences, Department of Biology, São Paulo State University (UNESP), Rio Claro, Brazil
| | - André R G Proença
- Laboratory of Biotechnology, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
| | - Leticia Tamborlin
- Laboratory of Biotechnology, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
- Institute of Biosciences, Department of Biology, São Paulo State University (UNESP), Rio Claro, Brazil
| | - Fernando M Simabuco
- Laboratory of Functional Properties in Foods, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
| | - Leo K Iwai
- Special Laboratory of Applied Toxinology, Center of Toxins, Immune-Response and Cell Signaling, LETA/ CeTICS, Butantan Institute, Butanta, Brazil
| | - Cleslei F Zanelli
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University (UNESP), Araraquara, Brazil
| | - Sandro R Valentini
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University (UNESP), Araraquara, Brazil
| | - Augusto D Luchessi
- Laboratory of Biotechnology, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
- Institute of Biosciences, Department of Biology, São Paulo State University (UNESP), Rio Claro, Brazil
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Abstract
S6K2, the newer member of S6 Kinase family, is a crucial modulator of Akt/mTOR signaling pathway and is a member of AGC kinase family that regulates cellular growth and survival. S6K1 and S6K2 share high sequence similarity; therefore, S6K2 had been underestimated. However, recent studies displayed distinct functions of S6K2. Activated by both Akt/mTOR and Ras/Raf/Mek/Erk signaling pathways, S6K2 regulates cancer cell survival via different routes. Complexation with antiapoptotic proteins BRAF and PKCε avoids non-small-cell lung cancer cells from apoptosis upon FGF-2 stimulation. Indirect upregulation of the translation of antiapoptotic proteins Bcl-XL and XIAP in HEK293T cells and interference with TNF-induced apoptosis in MCF-7 cells are other routes of cancer cell survival. The aforementioned studies on S6K2 necessitate the development of therapies targeting only on S6K2. Studies targeting S6K2 may help to build important roads for cancer therapy.
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Affiliation(s)
- Nurettin İlter Sever
- Department of Molecular Biology & Genetics, Faculty of Science & Letters, Pamukkale University, Denizli, Turkey
| | - Sevilay Cengiz Şahin
- Department of Molecular Biology & Genetics, Faculty of Science & Letters, Pamukkale University, Denizli, Turkey
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12
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Nguyen JT, Ray C, Fox AL, Mendonça DB, Kim JK, Krebsbach PH. Mammalian EAK-7 activates alternative mTOR signaling to regulate cell proliferation and migration. Sci Adv 2018; 4:eaao5838. [PMID: 29750193 PMCID: PMC5942914 DOI: 10.1126/sciadv.aao5838] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Accepted: 03/27/2018] [Indexed: 06/06/2023]
Abstract
Nematode EAK-7 (enhancer-of-akt-1-7) regulates dauer formation and controls life span; however, the function of the human ortholog mammalian EAK-7 (mEAK-7) is unknown. We report that mEAK-7 activates an alternative mechanistic/mammalian target of rapamycin (mTOR) signaling pathway in human cells, in which mEAK-7 interacts with mTOR at the lysosome to facilitate S6K2 activation and 4E-BP1 repression. Despite interacting with mTOR and mammalian lethal with SEC13 protein 8 (mLST8), mEAK-7 does not interact with other mTOR complex 1 (mTORC1) or mTOR complex 2 (mTORC2) components; however, it is essential for mTOR signaling at the lysosome. This phenomenon is distinguished by S6 and 4E-BP1 activity in response to nutrient stimulation. Conventional S6K1 phosphorylation is uncoupled from S6 phosphorylation in response to mEAK-7 knockdown. mEAK-7 recruits mTOR to the lysosome, a crucial compartment for mTOR activation. Loss of mEAK-7 results in a marked decrease in lysosomal localization of mTOR, whereas overexpression of mEAK-7 results in enhanced lysosomal localization of mTOR. Deletion of the carboxyl terminus of mEAK-7 significantly decreases mTOR interaction. mEAK-7 knockdown decreases cell proliferation and migration, whereas overexpression of mEAK-7 enhances these cellular effects. Constitutively activated S6K rescues mTOR signaling in mEAK-7-knocked down cells. Thus, mEAK-7 activates an alternative mTOR signaling pathway through S6K2 and 4E-BP1 to regulate cell proliferation and migration.
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Affiliation(s)
- Joe Truong Nguyen
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48105, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48105, USA
| | - Connor Ray
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48105, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48105, USA
| | - Alexandra Lucienne Fox
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48105, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48105, USA
| | - Daniela Baccelli Mendonça
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48105, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48105, USA
| | - Jin Koo Kim
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48105, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48105, USA
- Section of Periodontics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Paul H. Krebsbach
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI 48105, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48105, USA
- Section of Periodontics, University of California, Los Angeles, Los Angeles, CA 90095, USA
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13
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Yaguchi M, Kozaki A. Plant S6 kinases do not require hydrophobic motif phosphorylation for activity in yeast lacking Ypk3. FEBS Lett 2018; 592:610-620. [PMID: 29355926 DOI: 10.1002/1873-3468.12980] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Revised: 12/25/2017] [Accepted: 01/15/2018] [Indexed: 11/09/2022]
Abstract
The ribosomal protein S6 kinases (S6K) are among the major substrates and crucial effectors of the target of rapamycin (TOR) kinase, which is an evolutionarily conserved regulator of cell growth and proliferation. Recent research indicates that yeast Ypk3 is an ortholog of mammalian S6Ks. Here, we find that plant S6Ks restore ribosomal protein S6 phosphorylation in a rapamycin-sensitive manner in yeast cells lacking Ypk3. However, phosphorylation of a hydrophobic motif, which is mediated through TOR signaling and essential for mammalian S6K activity, is not detected in plant S6Ks. Furthermore, deletion of the N-terminal region of rice S6Ks shows phosphorylation of the hydrophobic motif and reduced rapamycin sensitivity. Our findings suggest a mechanism of plant S6K activation distinct from that of mammalian S6Ks.
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Affiliation(s)
| | - Akiko Kozaki
- Department of Biology, Shizuoka University, Japan
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Liu Y, Wei M, Guo H, Shao C, Meng L, Xu W, Wang N, Wang L, Power DM, Hou J, Mahboob S, Cui Z, Yang Y, Li Y, Zhao F, Chen S. Locus Mapping, Molecular Cloning, and Expression Analysis of rps6kb2, a Novel Metamorphosis-Related Gene in Chinese Tongue Sole (Cynoglossus semilaevis). Mar Biotechnol (NY) 2017; 19:497-516. [PMID: 28779262 DOI: 10.1007/s10126-017-9769-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 06/26/2017] [Indexed: 06/07/2023]
Abstract
Flatfish metamorphosis denotes the extraordinary transformation of a symmetric pelagic larva into an asymmetric benthic juvenile. This unique process involves eye migration, a 90° rotation in posture, and asymmetrical pigmentation for adaptation to a benthic lifestyle. In the present study, we used genetics to map a metamorphosis-related locus (q-10M) in the male linkage group (LG10M), a small interval of 0.9 cM corresponding to a 1.8 M-bp physical area in chromosome 9 in the Chinese tongue sole (Cynoglossus semilaevis). Combined with single-marker analysis, ribosomal protein S6 kinase 2 (rps6kb2) a member of the family of AGC kinases was identified as a novel metamorphosis-related candidate gene. Its expression pattern during metamorphosis was determined by quantitative RT-PCR and whole-mount in situ hybridization analysis. rps6kb2 gene was significantly expressed in metamorphic climax stage larvae and distributed in all the tissues transforming during metamorphosis, including tail, jaw, eye and skin of larvae. The results suggest that rps6kb2 has a general role in tissue transformations during flatfish metamorphosis including tail changes, skull remodeling, eye migration, and asymmetrical pigmentation.
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Affiliation(s)
- Yang Liu
- Wuxi Fisheries College, Nanjing Agricultural University, Wuxi, 214081, China
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
| | - Min Wei
- Wuxi Fisheries College, Nanjing Agricultural University, Wuxi, 214081, China
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
| | - Hua Guo
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
- College of Fisheries and Life Science, Shanghai Ocean University, Ministry of Education, Shanghai, 201306, China
| | - Changwei Shao
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
| | - Liang Meng
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
| | - Wenteng Xu
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
| | - Na Wang
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
| | - Lei Wang
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
| | - Deborah M Power
- College of Fisheries and Life Science, Shanghai Ocean University, Ministry of Education, Shanghai, 201306, China
| | - Jilun Hou
- Beidaihe Central Experiment Station, Chinese Academy of Fishery Sciences, Qinhuangdao, 066100, China
| | - Shahid Mahboob
- Department of Zoology, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia
- Department of Zoology, GC University, Faisalabad, 38000, Pakistan
| | - Zhongkai Cui
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
- College of Fisheries and Life Science, Shanghai Ocean University, Ministry of Education, Shanghai, 201306, China
| | - Yingming Yang
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
| | - Yangzhen Li
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
| | - Fazhen Zhao
- Wuxi Fisheries College, Nanjing Agricultural University, Wuxi, 214081, China
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China
| | - Songlin Chen
- Wuxi Fisheries College, Nanjing Agricultural University, Wuxi, 214081, China.
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences (CAFS), Key Laboratory for Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China.
- Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China.
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15
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Pirbhoy PS, Farris S, Steward O. Synaptically driven phosphorylation of ribosomal protein S6 is differentially regulated at active synapses versus dendrites and cell bodies by MAPK and PI3K/mTOR signaling pathways. ACTA ACUST UNITED AC 2017; 24:341-357. [PMID: 28716954 PMCID: PMC5516686 DOI: 10.1101/lm.044974.117] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 05/18/2017] [Indexed: 12/04/2022]
Abstract
High-frequency stimulation of the medial perforant path triggers robust phosphorylation of ribosomal protein S6 (rpS6) in activated dendritic domains and granule cell bodies. Here we dissect the signaling pathways responsible for synaptically driven rpS6 phosphorylation in the dentate gyrus using pharmacological agents to inhibit PI3-kinase/mTOR and MAPK/ERK-dependent kinases. Using phospho-specific antibodies for rpS6 at different sites (ser235/236 versus ser240/244), we show that delivery of the PI3-kinase inhibitor, wortmannin, decreased rpS6 phosphorylation throughout the somatodendritic compartment (granule cell layer, inner molecular layer, outer molecular layer), especially in granule cell bodies while sparing phosphorylation at activated synapses (middle molecular layer). In contrast, delivery of U0126, an MEK inhibitor, attenuated rpS6 phosphorylation specifically in the dendritic laminae leaving phosphorylation in the granule cell bodies intact. Delivery of the mTOR inhibitor, rapamycin, abolished activation of rpS6 phosphorylation in granule cell bodies and dendrites, whereas delivery of a selective S6K1 inhibitor, PF4708671, or RSK inhibitor, SL0101-1, attenuated rpS6 phosphorylation throughout the postsynaptic cell. These results reveal that MAPK/ERK-dependent signaling is predominately responsible for the selective induction of rpS6 phosphorylation at active synapses. In contrast, PI3-kinase/mTOR-dependent signaling induces rpS6 phosphorylation throughout the somatodendritic compartment but plays a minimal role at active synapses. Collectively, these results suggest a potential mechanism by which PI3-kinase/mTOR and MAPK/ERK pathways regulate translation at specific subcellular compartments in response to synaptic activity.
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Affiliation(s)
- Patricia Salgado Pirbhoy
- Reeve-Irvine Research Center, University of California, Irvine, California 92697, USA.,Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California, Irvine, California 92697, USA
| | - Shannon Farris
- Reeve-Irvine Research Center, University of California, Irvine, California 92697, USA.,Department of Anatomy and Neurobiology
| | - Oswald Steward
- Reeve-Irvine Research Center, University of California, Irvine, California 92697, USA.,Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California, Irvine, California 92697, USA.,Department of Anatomy and Neurobiology.,Department of Neurosurgery, University of California, Irvine, California 92697, USA
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Razquin Navas P, Thedieck K. Differential control of ageing and lifespan by isoforms and splice variants across the mTOR network. Essays Biochem 2017; 61:349-68. [PMID: 28698309 DOI: 10.1042/EBC20160086] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 05/19/2017] [Accepted: 05/23/2017] [Indexed: 11/17/2022]
Abstract
Ageing can be defined as the gradual deterioration of physiological functions, increasing the incidence of age-related disorders and the probability of death. Therefore, the term ageing not only reflects the lifespan of an organism but also refers to progressive functional impairment and disease. The nutrient-sensing kinase mTOR (mammalian target of rapamycin) is a major determinant of ageing. mTOR promotes cell growth and controls central metabolic pathways including protein biosynthesis, autophagy and glucose and lipid homoeostasis. The concept that mTOR has a crucial role in ageing is supported by numerous reports on the lifespan-prolonging effects of the mTOR inhibitor rapamycin in invertebrate and vertebrate model organisms. Dietary restriction increases lifespan and delays ageing phenotypes as well and mTOR has been assigned a major role in this process. This may suggest a causal relationship between the lifespan of an organism and its metabolic phenotype. More than 25 years after mTOR's discovery, a wealth of metabolic and ageing-related effects have been reported. In this review, we cover the current view on the contribution of the different elements of the mTOR signalling network to lifespan and age-related metabolic impairment. We specifically focus on distinct roles of isoforms and splice variants across the mTOR network. The comprehensive analysis of mouse knockout studies targeting these variants does not support a tight correlation between lifespan prolongation and improved metabolic phenotypes and questions the strict causal relationship between them.
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Abstract
The anti-apoptotic Bcl-2 family protein myeloid cell leukemia-1 (Mcl-1) plays an important role in breast cancer cell survival and chemoresistance. We have previously shown that knockdown of the 40S ribosomal protein S6 kinase-2 (S6K2), which acts downstream of the mechanistic target of rapamycin complex 1 (mTORC1), enhanced breast cancer cell death by apoptotic stimuli. The increase in cell death by S6K2 depletion was partly due to inactivation of Akt. In the present study, we investigated if S6K2 regulates Mcl-1, which acts downstream of Akt. Silencing of S6K2 but not S6K1 in T47D cells decreased Mcl-1 level, and potentiated apoptosis induced by TRAIL and doxorubicin. Knockdown of S6K2 also decreased the level of anti-apoptotic Bcl-xl. Depletion of the tumor suppressor protein PDCD4 (programmed cell death 4), which regulates translation of several anti-apoptotic proteins, reversed downregulation of Bcl-xl but not Mcl-1 and failed to reverse the effect of S6K2 knockdown on potentiation of doxorubicin-induced apoptosis. Downregulation of Mcl-1 by S6K2 knockdown was partly restored by the proteasome inhibitor MG132. Overexpression of catalytically-active Akt or knockdown of glycogen synthase kinase-3 (GSK3)-β, a substrate for Akt, had little effect on Mcl-1 downregulation caused by S6K2 deficiency. Silencing of S6K2 increased the level of c-Jun N-terminal kinase (JNK) and knockdown of JNK1 increased basal Mcl-1 level and partly reversed the effect of S6K2 knockdown on Mcl-1 downregulation. JNK1 knockdown also had a modest effect in attenuating the increase in doxorubicin-induced apoptosis caused by S6K2 deficiency. These results suggest that S6K2 regulates apoptosis via multiple mechanisms, and involves both Akt and JNK.
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Diez H, Benitez MJ, Fernandez S, Torres-Aleman I, Garrido JJ, Wandosell F. Class I PI3-kinase or Akt inhibition do not impair axonal polarization, but slow down axonal elongation. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 2016; 1863:2574-2583. [DOI: 10.1016/j.bbamcr.2016.07.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 07/05/2016] [Accepted: 07/08/2016] [Indexed: 11/17/2022]
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Mucke HA. Patent highlights: February-March 2016. Pharm Pat Anal 2016; 5:203-9. [PMID: 27336587 DOI: 10.4155/ppa-2016-0019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.
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Karlsson E, Magić I, Bostner J, Dyrager C, Lysholm F, Hallbeck AL, Stål O, Lundström P. Revealing Different Roles of the mTOR-Targets S6K1 and S6K2 in Breast Cancer by Expression Profiling and Structural Analysis. PLoS One 2015; 10:e0145013. [PMID: 26698305 PMCID: PMC4689523 DOI: 10.1371/journal.pone.0145013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Accepted: 11/25/2015] [Indexed: 12/21/2022] Open
Abstract
Background The AKT/mTORC1/S6K pathway is frequently overstimulated in breast cancer, constituting a promising therapeutic target. The benefit from mTOR inhibitors varies, likely as a consequence of tumour heterogeneity, and upregulation of several compensatory feed-back mechanisms. The mTORC1 downstream effectors S6K1, S6K2, and 4EBP1 are amplified and overexpressed in breast cancer, associated with a poor outcome and divergent endocrine treatment benefit. S6K1 and S6K2 share high sequence homology, but evidence of partly distinct biological functions is emerging. The aim of this work was to explore possible different roles and treatment target potentials of S6K1 and S6K2 in breast cancer. Materials and methods Whole-genome expression profiles were compared for breast tumours expressing high levels of S6K1, S6K2 or 4EBP1, using public datasets, as well as after in vitro siRNA downregulation of S6K1 and/or S6K2 in ZR751 breast cancer cells. In silico homology modelling of the S6K2 kinase domain was used to evaluate its possible structural divergences to S6K1. Results Genome expression profiles were highly different in S6K1 and S6K2 high tumours, whereas S6K2 and 4EBP1 profiles showed significant overlaps, both correlated to genes involved in cell cycle progression, among these the master regulator E2F1. S6K2 and 4EBP1 were inversely associated with IGF1 levels, and their prognostic value was shown to be restricted to tumours positive for IGFR and/or HER2. In vitro, S6K1 and S6K2 silencing resulted in upregulation of genes in the mTORC1 and mTORC2 complexes. Isoform-specific silencing also showed distinct patterns, e.g. S6K2 downregulation lead to upregulation of several cell cycle associated genes. Structural analyses of the S6K2 kinase domain showed unique structure patterns, deviating from those of S6K1, facilitating the development of isoform-specific inhibitors. Our data support emerging proposals of distinct biological features of S6K1 and S6K2, suggesting their importance as separate oncogenes and clinical markers, where specific targeting in different breast cancer subtypes could facilitate further individualised therapies.
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Affiliation(s)
- Elin Karlsson
- Department of Clinical and Experimental Medicine, and Department of Oncology, Linköping University, SE-58185, Linköping, Sweden
| | - Ivana Magić
- Department of Clinical and Experimental Medicine, and Department of Oncology, Linköping University, SE-58185, Linköping, Sweden
- Division of Chemistry, Department of Physics, Chemistry and Biology, Linköping University, SE-58183, Linköping, Sweden
| | - Josefine Bostner
- Department of Clinical and Experimental Medicine, and Department of Oncology, Linköping University, SE-58185, Linköping, Sweden
| | - Christine Dyrager
- Division of Chemistry, Department of Physics, Chemistry and Biology, Linköping University, SE-58183, Linköping, Sweden
| | - Fredrik Lysholm
- Division of Bioinformatics and SeRC (Swedish e-Science Research Centre), Department of Physics, Chemistry and Biology, Linköping University, SE-581 83, Linköping, Sweden
| | - Anna-Lotta Hallbeck
- Department of Clinical and Experimental Medicine, and Department of Oncology, Linköping University, SE-58185, Linköping, Sweden
| | - Olle Stål
- Department of Clinical and Experimental Medicine, and Department of Oncology, Linköping University, SE-58185, Linköping, Sweden
- * E-mail: (OS); (PL)
| | - Patrik Lundström
- Division of Chemistry, Department of Physics, Chemistry and Biology, Linköping University, SE-58183, Linköping, Sweden
- * E-mail: (OS); (PL)
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Dasgupta A, Chen KH, Munk RB, Sasaki CY, Curtis J, Longo DL, Ghosh P. Mechanism of Activation-Induced Downregulation of Mitofusin 2 in Human Peripheral Blood T Cells. J Immunol 2015; 195:5780-6. [PMID: 26566676 DOI: 10.4049/jimmunol.1501023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 10/17/2015] [Indexed: 12/11/2022]
Abstract
Mitofusin 2 (Mfn2), a mitochondrial protein, was shown to have antiproliferative properties when overexpressed. In this article, we show that activation of resting human peripheral blood T cells caused downregulation of Mfn2 levels. This downregulation of Mfn2 was blocked by different inhibitors (mTOR inhibitor rapamycin, PI3K inhibitor LY294002, and Akt inhibitor A443654), producing cells that were arrested in the G0/G1 stage of the cell cycle. Furthermore, the activation-induced downregulation of Mfn2 preceded the entry of the cells into the cell cycle, suggesting that Mfn2 downregulation is a prerequisite for activated T cell entry into the cell cycle. Accordingly, small interfering RNA-mediated knockdown of Mfn2 resulted in increased T cell proliferation. Overexpression of constitutively active AKT resulted in the downregulation of Mfn2, which can be blocked by a proteasome inhibitor. Akt-mediated downregulation of Mfn2 was via the mTORC1 pathway because this downregulation was blocked by rapamycin, and overexpression of wild-type, but not kinase-dead mTOR, caused Mfn2 downregulation. Our data suggested that activation-induced reactive oxygen species production plays an important role in the downregulation of Mfn2. Collectively, our data suggest that the PI3K-AKT-mTOR pathway plays an important role in activation-induced downregulation of Mfn2 and subsequent proliferation of resting human T cells.
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Affiliation(s)
- Asish Dasgupta
- Lymphocyte Cell Biology Unit, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, MD; and
| | - Kuang-Hueih Chen
- Lymphocyte Cell Biology Unit, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, MD; and
| | - Rachel B Munk
- Lymphocyte Cell Biology Unit, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, MD; and
| | - Carl Y Sasaki
- Lymphocyte Cell Biology Unit, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, MD; and
| | - Jessica Curtis
- Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| | - Dan L Longo
- Lymphocyte Cell Biology Unit, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, MD; and
| | - Paritosh Ghosh
- Lymphocyte Cell Biology Unit, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, MD; and
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22
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Bostner J, Karlsson E, Eding CB, Perez-Tenorio G, Franzén H, Konstantinell A, Fornander T, Nordenskjöld B, Stål O. S6 kinase signaling: tamoxifen response and prognostic indication in two breast cancer cohorts. Endocr Relat Cancer 2015; 22:331-43. [PMID: 25972244 DOI: 10.1530/erc-14-0513] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Detection of signals in the mammalian target of rapamycin (mTOR) and the estrogen receptor (ER) pathways may be a future clinical tool for the prediction of adjuvant treatment response in primary breast cancer. Using immunohistological staining, we investigated the value of the mTOR targets p70-S6 kinase (S6K) 1 and 2 as biomarkers for tamoxifen benefit in two independent clinical trials comparing adjuvant tamoxifen with no tamoxifen or 5 years versus 2 years of tamoxifen treatment. In addition, the prognostic value of the S6Ks was evaluated. We found that S6K1 correlated with proliferation, HER2 status, and cytoplasmic AKT activity, whereas high protein expression levels of S6K2 and phosphorylated (p) S6K were more common in ER-positive, and low-proliferative tumors with pAKT-s473 localized to the nucelus. Nuclear accumulation of S6K1 was indicative of a reduced tamoxifen effect (hazard ratio (HR): 1.07, 95% CI: 0.53-2.81, P=0.84), compared with a significant benefit from tamoxifen treatment in patients without tumor S6K1 nuclear accumulation (HR: 0.42, 95% CI: 0.29-0.62, P<0.00001). Also S6K1 and S6K2 activation, indicated by pS6K-t389 expression, was associated with low benefit from tamoxifen (HR: 0.97, 95% CI: 0.50-1.87, P=0.92). In addition, high protein expression of S6K1, independent of localization, predicted worse prognosis in a multivariate analysis, P=0.00041 (cytoplasm), P=0.016 (nucleus). In conclusion, the mTOR-activated kinases S6K1 and S6K2 interfere with proliferation and response to tamoxifen. Monitoring their activity and intracellular localization may provide biomarkers for breast cancer treatment, allowing the identification of a group of patients less likely to benefit from tamoxifen and thus in need of an alternative or additional targeted treatment.
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Affiliation(s)
- Josefine Bostner
- Department of Clinical and Experimental MedicineDepartment of OncologyDepartment of Clinical and Experimental MedicineDivision of Dermatology, Linköping University, SE-58185 Linköping, SwedenDepartment of OncologyKarolinska University Hospital, Karolinska Institute, SE-17176 Stockholm, Sweden
| | - Elin Karlsson
- Department of Clinical and Experimental MedicineDepartment of OncologyDepartment of Clinical and Experimental MedicineDivision of Dermatology, Linköping University, SE-58185 Linköping, SwedenDepartment of OncologyKarolinska University Hospital, Karolinska Institute, SE-17176 Stockholm, Sweden
| | - Cecilia Bivik Eding
- Department of Clinical and Experimental MedicineDepartment of OncologyDepartment of Clinical and Experimental MedicineDivision of Dermatology, Linköping University, SE-58185 Linköping, SwedenDepartment of OncologyKarolinska University Hospital, Karolinska Institute, SE-17176 Stockholm, Sweden
| | - Gizeh Perez-Tenorio
- Department of Clinical and Experimental MedicineDepartment of OncologyDepartment of Clinical and Experimental MedicineDivision of Dermatology, Linköping University, SE-58185 Linköping, SwedenDepartment of OncologyKarolinska University Hospital, Karolinska Institute, SE-17176 Stockholm, Sweden
| | - Hanna Franzén
- Department of Clinical and Experimental MedicineDepartment of OncologyDepartment of Clinical and Experimental MedicineDivision of Dermatology, Linköping University, SE-58185 Linköping, SwedenDepartment of OncologyKarolinska University Hospital, Karolinska Institute, SE-17176 Stockholm, Sweden
| | - Aelita Konstantinell
- Department of Clinical and Experimental MedicineDepartment of OncologyDepartment of Clinical and Experimental MedicineDivision of Dermatology, Linköping University, SE-58185 Linköping, SwedenDepartment of OncologyKarolinska University Hospital, Karolinska Institute, SE-17176 Stockholm, Sweden
| | - Tommy Fornander
- Department of Clinical and Experimental MedicineDepartment of OncologyDepartment of Clinical and Experimental MedicineDivision of Dermatology, Linköping University, SE-58185 Linköping, SwedenDepartment of OncologyKarolinska University Hospital, Karolinska Institute, SE-17176 Stockholm, Sweden
| | - Bo Nordenskjöld
- Department of Clinical and Experimental MedicineDepartment of OncologyDepartment of Clinical and Experimental MedicineDivision of Dermatology, Linköping University, SE-58185 Linköping, SwedenDepartment of OncologyKarolinska University Hospital, Karolinska Institute, SE-17176 Stockholm, Sweden
| | - Olle Stål
- Department of Clinical and Experimental MedicineDepartment of OncologyDepartment of Clinical and Experimental MedicineDivision of Dermatology, Linköping University, SE-58185 Linköping, SwedenDepartment of OncologyKarolinska University Hospital, Karolinska Institute, SE-17176 Stockholm, Sweden
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23
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Hać A, Domachowska A, Narajczyk M, Cyske K, Pawlik A, Herman-Antosiewicz A. S6K1 controls autophagosome maturation in autophagy induced by sulforaphane or serum deprivation. Eur J Cell Biol 2015; 94:470-81. [PMID: 26054233 DOI: 10.1016/j.ejcb.2015.05.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 04/27/2015] [Accepted: 05/25/2015] [Indexed: 01/04/2023] Open
Abstract
It is well established that mTORC1 suppresses autophagy by phosphorylation and inactivation of proteins involved in autophagosome formation. However, the role of its substrate, p70S6 kinase1 (S6K1), in autophagy is quite controversial. In some models S6K1 activity correlates with autophagy suppression, however, some other studies show that S6K1 promotes rather than inhibits this process. Here, we investigated the role of S6K1 in prostate cancer cells (PC-3) and non-cancerous, mouse embryonic fibroblasts (MEF), either treated with autophagy inducer sulforaphane, an isothiocyanate derived from cruciferous plants, or deprived of serum. Our results indicate that constitutively active S6K1 decreases the level of LC3 processing and foci formation by autophagosomal vacuoles in cells treated with sulforaphane. On the other hand, presence of S6K1 is necessary for autophagosome maturation under conditions of autophagy induced by either sulforaphane or serum deprivation. Diminished level of S6K1 or lack of S6 kinases results in both, accumulation of autophagosomes and drop in the autophagolysosome number, and thus disturbs autophagy flux under stress conditions. Moreover, lack of S6 kinases reduces cell survival under stress conditions.
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Affiliation(s)
- Aleksandra Hać
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Anna Domachowska
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Magdalena Narajczyk
- Laboratory of Electron Microscopy, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Karolina Cyske
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Anna Pawlik
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
| | - Anna Herman-Antosiewicz
- Department of Molecular Biology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland.
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Fonseca BD, Smith EM, Yelle N, Alain T, Bushell M, Pause A. The ever-evolving role of mTOR in translation. Semin Cell Dev Biol 2014; 36:102-12. [PMID: 25263010 DOI: 10.1016/j.semcdb.2014.09.014] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 09/12/2014] [Accepted: 09/15/2014] [Indexed: 02/06/2023]
Abstract
Control of translation allows for the production of stoichiometric levels of each protein in the cell. Attaining such a level of fine-tuned regulation of protein production requires the coordinated temporal and spatial control of numerous cellular signalling cascades impinging on the various components of the translational machinery. Foremost among these is the mTOR signalling pathway. The mTOR pathway regulates both the initiation and elongation steps of protein synthesis through the phosphorylation of numerous translation factors, while simultaneously ensuring adequate folding of nascent polypeptides through co-translational degradation of misfolded proteins. Perhaps most remarkably, mTOR is also a key regulator of the synthesis of ribosomal proteins and translation factors themselves. Two seminal studies have recently shown in translatome analysis that the mTOR pathway preferentially regulates the translation of mRNAs encoding ribosomal proteins and translation factors. Therefore, the role of the mTOR pathway in the control of protein synthesis extends far beyond immediate translational control. By controlling ribosome production (and ultimately ribosome availability), mTOR is a master long-term controller of protein synthesis. Herein, we review the literature spanning the early discoveries of mTOR on translation to the latest advances in our understanding of how the mTOR pathway controls the synthesis of ribosomal proteins.
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Affiliation(s)
- Bruno D Fonseca
- Children's Hospital of Eastern Ontario Research Institute, 401 Smyth Road, Ottawa, ON K1H 8L1, Canada.
| | - Ewan M Smith
- MRC Toxicology Unit, Hodgkin Building, Lancaster Road, Leicester LE1 9HN, UK
| | - Nicolas Yelle
- Children's Hospital of Eastern Ontario Research Institute, 401 Smyth Road, Ottawa, ON K1H 8L1, Canada
| | - Tommy Alain
- Children's Hospital of Eastern Ontario Research Institute, 401 Smyth Road, Ottawa, ON K1H 8L1, Canada
| | - Martin Bushell
- MRC Toxicology Unit, Hodgkin Building, Lancaster Road, Leicester LE1 9HN, UK
| | - Arnim Pause
- Goodman Cancer Research Centre, Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada.
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25
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Abstract
The phosphoinositide 3-kinase pathway represents an important anticancer target because it has been implicated in cancer cell growth, survival, and motility. Recent studies show that PI3K may also play a role in the development of resistance to currently available therapies. In a broad range of cancers, various components of the phosphoinositide 3-kinase signaling axis are genetically modified, and the pathway can be activated through many different mechanisms. The frequency of genetic alterations in the phosphoinositide 3-kinase pathway, coupled with the impact in oncogenesis and disease progression, make this signaling axis an attractive target in anticancer therapy. A better understanding of the critical function of the phosphoinositide 3-kinase pathway in leukemias and lymphomas has led to the clinical evaluation of novel rationally designed inhibitors in this setting. Three main categories of phosphoinositide 3-kinase inhibitors have been developed so far: agents that target phosphoinositide 3-kinase and mammalian target of rapamycin (dual inhibitors), pan-phosphoinositide 3-kinase inhibitors that target all class I isoforms, and isoform-specific inhibitors that selectively target the α, -β, -γ, or -δ isoforms. Emerging data highlight the promise of phosphoinositide 3-kinase inhibitors in combination with other therapies for the treatment of patients with hematologic malignancies. Further evaluation of phosphoinositide 3-kinase inhibitors in first-line or subsequent regimens may improve clinical outcomes. This article reviews the role of phosphoinositide 3-kinase signaling in hematologic malignancies and the potential clinical utility of inhibitors that target this pathway.
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Abstract
The kinase mammalian target of rapamycin (mTOR) is a central regulator of cell growth and proliferation that integrates inputs from growth factor receptors, nutrient availability, intracellular ATP (adenosine 5'-triphosphate), and a variety of stressors. Since early works in the mid-1990s uncovered the role of mTOR in stimulating protein translation, this kinase has emerged as a rather multifaceted regulator of numerous processes. Whereas mTOR is generally activated by growth- and proliferation-stimulating signals, its activity can be reduced and even suppressed when cells are exposed to a variety of stress conditions. However, cells can also adapt to stress while maintaining their growth capacity and mTOR function. Despite knowledge accumulated on how stress represses mTOR, less is known about mTOR influencing stress responses. In this review, we discuss the capability of mTOR, in particular mTOR complex 1 (mTORC1), to activate stress-responsive transcription factors, and we outline open questions for future investigation.
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Affiliation(s)
- Jose Aramburu
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain.
| | - M Carmen Ortells
- Centre for Genomic Regulation and Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Sonia Tejedor
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Maria Buxadé
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Cristina López-Rodríguez
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain.
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27
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Hong S, Zhao B, Lombard DB, Fingar DC, Inoki K. Cross-talk between sirtuin and mammalian target of rapamycin complex 1 (mTORC1) signaling in the regulation of S6 kinase 1 (S6K1) phosphorylation. J Biol Chem 2014; 289:13132-41. [PMID: 24652283 PMCID: PMC4036325 DOI: 10.1074/jbc.m113.520734] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
p70 ribosomal S6 kinase (S6K1), a major substrate of the mammalian target of rapamycin (mTOR) kinase, regulates diverse cellular processes including protein synthesis, cell growth, and survival. Although it is well known that the activity of S6K1 is tightly coupled to its phosphorylation status, the regulation of S6K1 activity by other post-translational modifications such as acetylation has not been well understood. Here we show that the acetylation of the C-terminal region (CTR) of S6K1 blocks mTORC1-dependent Thr-389 phosphorylation, an essential phosphorylation site for S6K1 activity. The acetylation of the CTR of S6K1 is inhibited by the class III histone deacetylases, SIRT1 and SIRT2. An S6K1 mutant lacking acetylation sites in its CTR shows enhanced Thr-389 phosphorylation and kinase activity, whereas the acetylation-mimetic S6K1 mutant exhibits decreased Thr-389 phosphorylation and kinase activity. Interestingly, relative to the acetylation-mimetic S6K1 mutant, the acetylation-defective mutant displays higher affinity toward Raptor, an essential scaffolding component of mTORC1 that recruits mTORC1 substrates. These observations indicate that sirtuin-mediated regulation of S6K1 acetylation is an additional important regulatory modification that impinges on the mechanisms underlying mTORC1-dependent S6K1 activation.
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Affiliation(s)
| | - Bin Zhao
- the Life Sciences Institute and Innovation Center for Cell Biology, Zhejiang University, Hangzhou 310058, Zhejiang, China
| | | | | | - Ken Inoki
- From the Life Sciences Institute, ,Department of Molecular and Integrative Physiology, and ,Internal Medicine, The University of Michigan, Ann Arbor, Michigan 48109 and , To whom correspondence should be addressed: 210 Washtenaw Ave., Ann Arbor, MI 48109-2216. Fax: 734-647-9702; E-mail:
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28
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Ismail HM, Hurd PJ, Khalil MI, Kouzarides T, Bannister A, Gout I. S6 Kinase 2 Is Bound to Chromatin-Nuclear Matrix Cellular Fractions and Is Able to Phosphorylate Histone H3 at Threonine 45 In Vitro and In Vivo. J Cell Biochem 2014; 115:1048-62. [DOI: 10.1002/jcb.24566] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 03/28/2013] [Indexed: 11/08/2022]
Affiliation(s)
- Heba M.S. Ismail
- Institute of Structural and Molecular Biology; University College London; London WC1E 6BT United Kingdom
- Cancer Biology Department, National Cancer Institute; Cairo University; Cairo Egypt
| | - Paul J. Hurd
- Gurdon Institute and Department of Pathology; University of Cambridge; Cambridge UK
- School of Biological and Chemical Sciences; Queen Mary University of London; Mile End Road London E1 4NS United Kingdom
| | - Mahmoud I.M. Khalil
- Institute of Structural and Molecular Biology; University College London; London WC1E 6BT United Kingdom
- Molecular Biology Division, Zoology Department, Faculty of Science; Alexandria University; Alexandria Egypt
| | - Tony Kouzarides
- Gurdon Institute and Department of Pathology; University of Cambridge; Cambridge UK
| | - Andrew Bannister
- Gurdon Institute and Department of Pathology; University of Cambridge; Cambridge UK
| | - Ivan Gout
- Institute of Structural and Molecular Biology; University College London; London WC1E 6BT United Kingdom
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29
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Pende M, Treins C. Ribosomal Protein S6 and S6 Kinases. Translation and Its Regulation in Cancer Biology and Medicine 2014:345-362. [DOI: 10.1007/978-94-017-9078-9_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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30
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Mok KW, Mruk DD, Cheng CY. Regulation of blood-testis barrier (BTB) dynamics during spermatogenesis via the "Yin" and "Yang" effects of mammalian target of rapamycin complex 1 (mTORC1) and mTORC2. Int Rev Cell Mol Biol 2013; 301:291-358. [PMID: 23317821 DOI: 10.1016/b978-0-12-407704-1.00006-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In mammalian testes, haploid spermatozoa are formed from diploid spermatogonia during spermatogenesis, which is a complicated cellular process. While these cellular events were reported in the 1960s and 1970s, the underlying molecular mechanism(s) that regulates these events remained unexplored until the past ∼10 years. For instance, adhesion proteins were shown to be integrated components at the Sertoli cell-cell interface and/or the Sertoli-spermatid interface in the late 1980s. But only until recently, studies have demonstrated that some of the adhesion proteins serve as the platform for signal transduction that regulates cell adhesion. In this chapter, a brief summary and critical discussion are provided on the latest findings regarding these cell-adhesion proteins in the testis and their relationship to spermatogenesis. Moreover, antagonistic effects of two mammalian target of rapamycin (mTOR) complexes, known as mTORC1 and mTORC2, on cell-adhesion function in the testis are discussed. Finally, a hypothetic model is presented to depict how these two mTOR-signaling complexes having the "yin" and "yang" antagonistic effects on the Sertoli cell tight junction (TJ)-permeability barrier can maintain the blood-testis barrier (BTB) integrity during the epithelial cycle while preleptotene spermatocytes are crossing the BTB.
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Affiliation(s)
- Ka Wai Mok
- Mary M. Wohlford Laboratory for Male Contraceptive Research, Center for Biomedical Research, Population Council, New York, USA
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Abstract
S6 kinase 2 (S6K2) is a member of the AGC kinases super-family. Its closest homolog, S6K1, has been extensively studied along the years. However, due to the belief in the community that the high degree of identity between these two isoforms would translate in essentially identical biological functions, S6K2 has been largely neglected. Nevertheless, recent research has clearly highlighted that these two proteins significantly differ in their roles in vitro as well as in vivo. These findings are significant to our understanding of S6 kinase signaling and the development of therapeutic strategies for several diseases including cancer. Here, we will focus on S6K2 and review the protein–protein interactions and specific substrates that determine the selective functions of this kinase.
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Affiliation(s)
- Olivier E Pardo
- Division of Cancer, Department of Surgery and Cancer, Imperial College, Hammersmith Hospital , London , UK
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32
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Ismail HM, Myronova O, Tsuchiya Y, Niewiarowski A, Tsaneva I, Gout I. Identification of the general transcription factor Yin Yang 1 as a novel and specific binding partner for S6 Kinase 2. Cell Signal 2013; 25:1054-63. [DOI: 10.1016/j.cellsig.2013.02.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Revised: 02/02/2013] [Accepted: 02/04/2013] [Indexed: 11/21/2022]
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Ben-Hur V, Denichenko P, Siegfried Z, Maimon A, Krainer A, Davidson B, Karni R. S6K1 alternative splicing modulates its oncogenic activity and regulates mTORC1. Cell Rep 2012; 3:103-15. [PMID: 23273915 DOI: 10.1016/j.celrep.2012.11.020] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 10/09/2012] [Accepted: 11/27/2012] [Indexed: 10/27/2022] Open
Abstract
Ribosomal S6 kinase 1 (S6K1) is a major mTOR downstream signaling molecule that regulates cell size and translation efficiency. Here, we report that short isoforms of S6K1 are overproduced in breast cancer cell lines and tumors. Overexpression of S6K1 short isoforms induces transformation of human breast epithelial cells. The long S6K1 variant (Iso-1) induced opposite effects. It inhibits Ras-induced transformation and tumor formation, while its knockdown or knockout induces transformation, suggesting that Iso-1 has a tumor-suppressor activity. Furthermore, we found that S6K1 short isoforms bind and activate mTORC1, elevating 4E-BP1 phosphorylation, cap-dependent translation, and Mcl-1 protein levels. Both a phosphorylation-defective 4E-BP1 mutant and the mTORC1 inhibitor rapamycin partially blocked the oncogenic effects of S6K1 short isoforms, suggesting that these are mediated by mTORC1 and 4E-BP1. Thus, alternative splicing of S6K1 acts as a molecular switch in breast cancer cells, elevating oncogenic isoforms that activate mTORC1.
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Affiliation(s)
- Vered Ben-Hur
- Department of Biochemistry and Molecular Biology, the Institute for Medical Research Israel-Canada, Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
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Savinska L, Skorokhod O, Klipa O, Gout I, Filonenko V. Development of monoclonal antibodies specific to ribosomal protein S6 kinase 2. Hybridoma (Larchmt) 2012; 31:289-94. [PMID: 22894784 DOI: 10.1089/hyb.2012.0032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Ribosomal protein S6 kinase 2 (S6K2) is a serine/threonine kinase that belongs to the family of AGC kinases, which includes PKB/Akt, PKC, PDK1, and SGK1. Mammalian cells express two isoforms of S6K, termed S6K1 and S6K2. Each of these has nuclear and cytoplasmic spicing variants, which originate from different initiation start codons. Nuclear isoforms of S6K1 and S6K2 are slightly longer, as they possess additional sequences at the N-terminus with nuclear localization signals. Biochemical and genetic studies implicated S6Ks in the regulation of cell size, growth, and energy metabolism. Deregulation of S6K signaling has been linked to various human pathologies, making them excellent targets for drug discovery. The aim of this study was to produce monoclonal antibodies directed at the N-terminal regulatory region of S6K2, which shows very low homology to S6K1 or other members of the AGC family. To achieve this goal, two S6K2 fragments covering 1-64aa and 14-64aa N-terminal sequences were expressed in bacteria as GST/6His fusion proteins. Affinity purified recombinant proteins were used as antigens for immunization, hybridoma screening, and analysis of generated clones. We produced a panel of S6K2-specific antibodies, which recognized recombinant S6K2 proteins in ELISA and Western blot analysis. Further analysis of selected clones revealed that three clones, termed B1, B2, and B4, specifically recognized not only recombinant, but also endogenous S6K2 in Western blot analysis of HEK293 cell lysates. Specificity of B2 clone has been confirmed in additional commonly used immunoassays, including immunoprecipitation and immunocytochemistry. These properties make B2 MAb particularly valuable for elucidating signal transduction pathways involving S6K2 signaling under physiological conditions and in human pathologies.
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Affiliation(s)
- Lilia Savinska
- Department of Cell Signalling, Institute of Molecular Biology and Genetics, NAS of Ukraine, Zabolotnogo str 150, Kyiv, Ukraine
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35
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Goodman CA, Kotecki JA, Jacobs BL, Hornberger TA. Muscle fiber type-dependent differences in the regulation of protein synthesis. PLoS One 2012; 7:e37890. [PMID: 22629468 DOI: 10.1371/journal.pone.0037890] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 04/30/2012] [Indexed: 01/09/2023] Open
Abstract
This study examined fiber type-dependent differences in the regulation of protein synthesis in individual muscle fibers found within the same whole muscle. Specifically, the in vivo SUrface SEnsing of Translation (SUnSET) methodology was used to measure protein synthesis in type 1, 2A, 2X and 2B fibers of the mouse plantaris muscle, in response to food deprivation (FD), and mechanical overload induced by synergist ablation (SA). The results show that 48 h of FD induced a greater decrease in protein synthesis in type 2X and 2B fibers compared to type 1 and 2A fibers. Type 2X and 2B fibers also had the largest FD-induced decrease in total S6 protein and Ser240/244 S6 phosphorylation, respectively. Moreover, only type 2X and 2B fibers displayed a FD-induced decrease in cross-sectional area (CSA). Ten days of SA also induced fiber type-dependent responses, with type 2B fibers having the smallest SA-induced increases in protein synthesis, CSA and Ser240/244 S6 phosphorylation, but the largest increase in total S6 protein. Embryonic myosin heavy chain (MHCEmb) positive fibers were also found in SA muscles and the protein synthesis rates, levels of S6 Ser240/244 phosphorylation, and total S6 protein content, were 3.6-, 6.1- and 2.9-fold greater than that found in fibers from control muscles, respectively. Overall, these results reveal differential responses in the regulation of protein synthesis and fiber size between fiber types found within the same whole muscle. Moreover, these findings demonstrate that changes found at the whole muscle level do not necessarily reflect changes in individual fiber types.
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Abstract
Akt is a member of the AGC kinase family and consists of three isoforms. As one of the major regulators of the class I PI3 kinase pathway, it has a key role in the control of cell metabolism, growth, and survival. Although it has been extensively studied in the nervous system, we have only a faint knowledge of the specific role of each isoform in differentiated neurons. Here, we have used both cortical and hippocampal neuronal cultures to analyse their function. We characterized the expression and function of Akt isoforms, and some of their substrates along different stages of neuronal development using a specific shRNA approach to elucidate the involvement of each isoform in neuron viability, axon development, and cell signalling. Our results suggest that three Akt isoforms show substantial compensation in many processes. However, the disruption of Akt2 and Akt3 significantly reduced neuron viability and axon length. These changes correlated with a tendency to increase in active caspase 3 and a decrease in the phosphorylation of some elements of the mTORC1 pathway. Indeed, the decrease of Akt2 and more evident the inhibition of Akt3 reduced the expression and phosphorylation of S6. All these data indicate that Akt2 and Akt3 specifically regulate some aspects of apoptosis and cell growth in cultured neurons and may contribute to the understanding of mechanisms of neuron death and pathologies that show deregulated growth.
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Affiliation(s)
- Hector Diez
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED) and Centro de Biología Molecular “Severo Ochoa", CSIC-UAM, Univ. Autonoma de Madrid, Madrid, Spain
| | - Juan Jose Garrido
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED) and Centro de Biología Molecular “Severo Ochoa", CSIC-UAM, Univ. Autonoma de Madrid, Madrid, Spain
- Laboratory of Neuronal Polarity, Department of Molecular, Cellular and Developmental Neurobiology, Instituto Cajal, CSIC, Madrid, Spain
| | - Francisco Wandosell
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED) and Centro de Biología Molecular “Severo Ochoa", CSIC-UAM, Univ. Autonoma de Madrid, Madrid, Spain
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37
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Magnuson B, Ekim B, Fingar DC. Regulation and function of ribosomal protein S6 kinase (S6K) within mTOR signalling networks. Biochem J 2012; 441:1-21. [PMID: 22168436 DOI: 10.1042/BJ20110892] [Citation(s) in RCA: 704] [Impact Index Per Article: 58.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The ribosomal protein S6K (S6 kinase) represents an extensively studied effector of the TORC1 [TOR (target of rapamycin) complex 1], which possesses important yet incompletely defined roles in cellular and organismal physiology. TORC1 functions as an environmental sensor by integrating signals derived from diverse environmental cues to promote anabolic and inhibit catabolic cellular functions. mTORC1 (mammalian TORC1) phosphorylates and activates S6K1 and S6K2, whose first identified substrate was rpS6 (ribosomal protein S6), a component of the 40S ribosome. Studies over the past decade have uncovered a number of additional S6K1 substrates, revealing multiple levels at which the mTORC1-S6K1 axis regulates cell physiology. The results thus far indicate that the mTORC1-S6K1 axis controls fundamental cellular processes, including transcription, translation, protein and lipid synthesis, cell growth/size and cell metabolism. In the present review we summarize the regulation of S6Ks, their cellular substrates and functions, and their integration within rapidly expanding mTOR (mammalian TOR) signalling networks. Although our understanding of the role of mTORC1-S6K1 signalling in physiology remains in its infancy, evidence indicates that this signalling axis controls, at least in part, glucose homoeostasis, insulin sensitivity, adipocyte metabolism, body mass and energy balance, tissue and organ size, learning, memory and aging. As dysregulation of this signalling axis contributes to diverse disease states, improved understanding of S6K regulation and function within mTOR signalling networks may enable the development of novel therapeutics.
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38
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Ortells MC, Morancho B, Drews-Elger K, Viollet B, Laderoute KR, López-Rodríguez C, Aramburu J. Transcriptional regulation of gene expression during osmotic stress responses by the mammalian target of rapamycin. Nucleic Acids Res 2012; 40:4368-84. [PMID: 22287635 PMCID: PMC3378878 DOI: 10.1093/nar/gks038] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Although stress can suppress growth and proliferation, cells can induce adaptive responses that allow them to maintain these functions under stress. While numerous studies have focused on the inhibitory effects of stress on cell growth, less is known on how growth-promoting pathways influence stress responses. We have approached this question by analyzing the effect of mammalian target of rapamycin (mTOR), a central growth controller, on the osmotic stress response. Our results showed that mammalian cells exposed to moderate hypertonicity maintained active mTOR, which was required to sustain their cell size and proliferative capacity. Moreover, mTOR regulated the induction of diverse osmostress response genes, including targets of the tonicity-responsive transcription factor NFAT5 as well as NFAT5-independent genes. Genes sensitive to mTOR-included regulators of stress responses, growth and proliferation. Among them, we identified REDD1 and REDD2, which had been previously characterized as mTOR inhibitors in other stress contexts. We observed that mTOR facilitated transcription-permissive conditions for several osmoresponsive genes by enhancing histone H4 acetylation and the recruitment of RNA polymerase II. Altogether, these results reveal a previously unappreciated role of mTOR in regulating transcriptional mechanisms that control gene expression during cellular stress responses.
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Affiliation(s)
- M Carmen Ortells
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain
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39
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Suganya R, Chen SL, Lu KH. CDNA cloning and characterization of S6 kinase and its effect on yolk protein gene expression in the oriental fruit fly Bactrocera dorsalis (Hendel). Arch Insect Biochem Physiol 2011; 78:177-189. [PMID: 22105664 DOI: 10.1002/arch.20446] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
p70 S6 kinase (S6K), a serine/threonine protein kinase, is a downstream target of target of rapamycin (TOR) gene and an important regulator of protein synthesis responsible for cell growth and reproduction. In this study, a S6K gene, named BdS6K (GenBank Accession No. GQ203802), was isolated from the oriental fruit fly Bactrocera dorsalis (Hendel). Quantitative RT-PCR showed that BdS6K mRNA is expressed at a higher level in egg than in other developmental stages, as well as in ovary than in fat body. Downregulation of BdS6K activity by rapamycin treatment in larval stage resulted in the developmental defects of larvae, pupae, and adults, with a reduced yolk protein (YP) expression in the fat body throughout the first reproductive cycle with a substantial reduction in ovary size, and also repressed the egg development in female fruit fly. Knockdown of BdS6K gene by RNA interference in the adult significantly decreased the YP expression. These observations support the involvement of BdS6K signaling in the regulation of the YP synthesis and egg development in B. dorsalis.
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Affiliation(s)
- R Suganya
- Department of Entomology, National Chung Hsing University, Taichung City, Taiwan, Republic of China
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40
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Chen W, Dittmer DP. Ribosomal protein S6 interacts with the latency-associated nuclear antigen of Kaposi's sarcoma-associated herpesvirus. J Virol 2011; 85:9495-505. [PMID: 21734034 DOI: 10.1128/JVI.02620-10] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The latency-associated nuclear antigen (LANA) is central to the maintenance of Kaposi's sarcoma-associated herpesvirus (KSHV) and to the survival of KSHV-carrying tumor cells. In an effort to identify interaction partners of LANA, we purified authentic high-molecular-weight complexes of LANA by conventional chromatography followed by immunoprecipitation from the BC-3 cell line. This is the first analysis of LANA-interacting partners that is not based on forced ectopic expression of LANA. Subsequent tandem mass spectrometry (MS/MS) analysis identified many of the known LANA-interacting proteins. We confirmed LANA's interactions with histones. Three classes of proteins survived our stringent four-step purification procedure (size, heparin, anion, and immunoaffinity chromatography): two heat shock proteins (Hsp70 and Hsp96 precursor), signal recognition particle 72 (SRP72), and 10 different ribosomal proteins. These proteins are likely involved in structural interactions within LANA high-molecular-weight complexes. Here, we show that ribosomal protein S6 (RPS6) interacts with LANA. This interaction is mediated by the N-terminal domain of LANA and does not require DNA or RNA. Depletion of RPS6 from primary effusion lymphoma (PEL) cells dramatically decreases the half-life of full-length LANA. The fact that RPS6 has a well-established nuclear function beyond its role in ribosome assembly suggests that RPS6 (and by extension other ribosomal proteins) contributes to the extraordinary stability of LANA.
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41
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Evans DS, Kapahi P, Hsueh WC, Kockel L. TOR signaling never gets old: aging, longevity and TORC1 activity. Ageing Res Rev 2011; 10:225-37. [PMID: 20385253 DOI: 10.1016/j.arr.2010.04.001] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Revised: 03/31/2010] [Accepted: 04/01/2010] [Indexed: 12/21/2022]
Abstract
The target of rapamycin (TOR) signal transduction network monitors intra- and extracellular conditions that favor cell growth. Research during the last decade has revealed a modular structure of the TOR signaling network. Each signaling module senses a particular set of signals from the cellular milieu and exerts regulatory control towards TOR activity. The TOR pathway responds to growth factor signals, nutrient availability, and cellular stresses like hypoxia and energy stress. The signaling modules and their molecular components constituting the TOR network are remarkably conserved in both sequence and function across species. In yeast, roundworms, flies, and mice, the TOR pathway has been shown to regulate lifespan. Correspondingly, genetic, dietary or pharmacological manipulation of individual signaling modules as well as TOR activity itself extends lifespan in these model organisms. We discuss the potential impact of manipulating TOR activity for human health and lifespan.
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Affiliation(s)
- Daniel S Evans
- Department of Medicine, University of California, San Francisco, United States
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42
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Nardella C, Lunardi A, Fedele G, Clohessy JG, Alimonti A, Kozma SC, Thomas G, Loda M, Pandolfi PP. Differential expression of S6K2 dictates tissue-specific requirement for S6K1 in mediating aberrant mTORC1 signaling and tumorigenesis. Cancer Res 2011; 71:3669-75. [PMID: 21444676 DOI: 10.1158/0008-5472.can-10-3962] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The S6K1 and S6K2 kinases are considered important mTOR signaling effectors, yet their contribution to tumorigenesis remains unclear. Aberrant mTOR activation is a frequent event in cancer that commonly results from heterozygous loss of PTEN. Here, we show for the first time a differential protein expression between S6K1 and S6K2 in both mouse and human tissues. Additionally, the inactivation of S6k1 in the context of Pten heterozygosity (Pten(+/-)) suggests a differential requirement for this protein across multiple tissues. This tissue specificity appears to be governed by the relative protein expression of S6k2. Accordingly, we find that deletion of S6k1 markedly impairs Pten(+/-) mediated adrenal tumorigenesis, specifically due to low expression of S6k2. Concomitant observation of low S6K2 levels in the human adrenal gland supports the development of S6K1 inhibitors for treatment of PTEN loss-driven pheochromocytoma.
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Affiliation(s)
- Caterina Nardella
- Cancer Genetics Program, Beth Israel Deaconess Cancer Center, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02115, USA
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43
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Abstract
The 40S ribosomal protein S6 kinase (S6K) acts downstream of mTOR, which plays important roles in cell proliferation, protein translation, and cell survival and is a target for cancer therapy. mTOR inhibitors are, however, of limited success. Although Akt is believed to act upstream of mTOR, persistent inhibition of p70 S6 kinase or S6K1 can activate Akt via a negative feedback loop. S6K exists as two homologues, S6K1 and S6K2, but little is known about the function of S6K2. In the present study, we have examined the effects of S6K2 on Akt activation and cell survival. Silencing of S6K1 caused a modest decrease, whereas knockdown of S6K2 caused a substantial increase in TNF-α and TRAIL (TNF-related apoptosis-inducing ligand)-mediated apoptosis. In contrast to S6K1, depletion of S6K2 by siRNA decreased basal and TNF-induced Akt phosphorylation. Ectopic expression of constitutively active Akt in MCF-7 cells restored cell survival in S6K2-depleted cells. We have previously shown that activation of Akt induces downregulation of Bid via p53. Knockdown of S6K2 caused an increase in p53, and downregulation of p53 by siRNA decreased Bid level. Silencing of Bid blunted the ability of S6K2 deficiency to enhance TNF-induced apoptosis. Taken together, our study shows that the two homologues of S6K have distinct effects on Akt activation and cell survival. Thus, targeting S6K2 may be an effective therapeutic strategy to treat cancers.
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Affiliation(s)
- Savitha Sridharan
- Department of Molecular Biology & Immunology, University of North Texas Health Science Center, Fort Worth, Texas, USA
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44
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Sengupta S, Peterson TR, Sabatini DM. Regulation of the mTOR complex 1 pathway by nutrients, growth factors, and stress. Mol Cell 2010; 40:310-22. [PMID: 20965424 DOI: 10.1016/j.molcel.2010.09.026] [Citation(s) in RCA: 938] [Impact Index Per Article: 67.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 09/03/2010] [Accepted: 09/28/2010] [Indexed: 02/06/2023]
Abstract
The large serine/threonine protein kinase mTOR regulates cellular and organismal homeostasis by coordinating anabolic and catabolic processes with nutrient, energy, and oxygen availability and growth factor signaling. Cells and organisms experience a wide variety of insults that perturb the homeostatic systems governed by mTOR and therefore require appropriate stress responses to allow cells to continue to function. Stress can manifest from an excess or lack of upstream signals or as a result of genetic perturbations in upstream effectors of the pathway. mTOR nucleates two large protein complexes that are important nodes in the pathways that help buffer cells from stresses, and are implicated in the progression of stress-associated phenotypes and diseases, such as aging, tumorigenesis, and diabetes. This review focuses on the key components of the mTOR complex 1 pathway and on how various stresses impinge upon them.
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Affiliation(s)
- Shomit Sengupta
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA
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45
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Hagner PR, Mazan-Mamczarz K, Dai B, Balzer EM, Corl S, Martin SS, Zhao XF, Gartenhaus RB. Ribosomal protein S6 is highly expressed in non-Hodgkin lymphoma and associates with mRNA containing a 5' terminal oligopyrimidine tract. Oncogene 2011; 30:1531-41. [PMID: 21102526 DOI: 10.1038/onc.2010.533] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The molecular mechanism(s) linking tumorigenesis and morphological alterations in the nucleolus are presently coming into focus. The nucleolus is the cellular organelle in which the formation of ribosomal subunits occurs. Ribosomal biogenesis occurs through the transcription of ribosomal RNA (rRNA), rRNA processing and production of ribosomal proteins. An error in any of these processes may lead to deregulated cellular translation, evident in multiple cancers and 'ribosomopathies'. Deregulated protein synthesis may be achieved through the overexpression of ribosomal proteins as seen in primary leukemic blasts with elevated levels of ribosomal proteins S11 and S14. In this study, we demonstrate that ribosomal protein S6 (RPS6) is highly expressed in primary diffuse large B-cell lymphoma (DLBCL) samples. Genetic modulation of RPS6 protein levels with specifically targeted short hairpin RNA (shRNA) lentiviruses led to a decrease in the actively proliferating population of cells compared with control shRNA. Low-dose rapamycin treatments have been shown to affect the translation of 5' terminal oligopyrimidine (5' TOP) tract mRNA, which encodes the translational machinery, implicating RPS6 in 5' TOP translation. Recently, it was shown that disruption of 40S ribosomal biogenesis through specific small inhibitory RNA knockdown of RPS6 defined RPS6 as a critical regulator of 5' TOP translation. For the first time, we show that RPS6 associates with multiple mRNAs containing a 5' TOP tract. These findings expand our understanding of the mechanism(s) involved in ribosomal biogenesis and deregulated protein synthesis in DLBCL.
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46
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Khanna-Gupta A. Regulation and deregulation of mRNA translation during myeloid maturation. Exp Hematol 2010; 39:133-41. [PMID: 21093533 DOI: 10.1016/j.exphem.2010.10.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 10/28/2010] [Accepted: 10/28/2010] [Indexed: 01/07/2023]
Abstract
Gene expression in the eukaryotic cell is regulated at a number of levels, including transcription of genomic DNA into messenger RNA (mRNA), nucleocytoplasmic export of mRNA, and translation of the exported mRNA into proteins in the cytoplasm by ribosomes. The role played by epigenetics and transcription factors associated with the control of gene expression in the developing neutrophil has been well documented and appreciated over the years. A wealth of information on the role played by transcription factors in myeloid biology has contributed to our understanding of both normal and abnormal neutrophil development. However, regulation of mRNA translation in myeloid cell maturation is much less well-studied. A better understanding of the translational control of myeloid gene expression may provide important insights into both normal and abnormal myeloid maturation. This review summarizes our current understanding of the regulation of myeloid gene expression at the mRNA translational level.
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Affiliation(s)
- Arati Khanna-Gupta
- Division of Hematology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA.
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47
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Pérez-Tenorio G, Karlsson E, Waltersson MA, Olsson B, Holmlund B, Nordenskjöld B, Fornander T, Skoog L, Stål O. Clinical potential of the mTOR targets S6K1 and S6K2 in breast cancer. Breast Cancer Res Treat 2010; 128:713-23. [PMID: 20953835 DOI: 10.1007/s10549-010-1058-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Accepted: 07/08/2010] [Indexed: 01/22/2023]
Abstract
The mammalian target of rapamycin (mTOR) and its substrates S6K1 and S6K2 regulate cell growth, proliferation, and metabolism through translational control. RPS6KB1 (S6K1) and RPS6KB2 (S6K2) are situated in the commonly amplified 17q21-23 and 11q13 regions. S6K1 amplification and protein overexpression have earlier been associated with a worse outcome in breast cancer, but information regarding S6K2 is scarce. The aim of this study was to evaluate the prognostic and treatment predictive relevance of S6K1/S6K2 gene amplification, as well as S6K2 protein expression in breast cancer. S6K1/S6K2 gene copy number was determined by real-time PCR in 207 stage II breast tumors and S6K2 protein expression was investigated by immunohistochemistry in 792 node-negative breast cancers. S6K1 amplification/gain was detected in 10.7%/21.4% and S6K2 amplification/gain in 4.3%/21.3% of the tumors. S6K2 protein was detected in the nucleus (38%) and cytoplasm (76%) of the tumor cells. S6K1 amplification was significantly associated with HER2 gene amplification and protein expression. S6K2 amplification correlated significantly with high S6K2 mRNA levels, ER+ status and CCND1 amplification. S6K1 and S6K2 gene amplification was associated with a worse prognosis independent of HER2 and CCND1. S6K2 gain and nuclear S6K2 expression was related to an improved benefit from tamoxifen among patients with ER+, respectively ER+/PgR+ tumors. In the ER+/PgR- subgroup, nuclear S6K2 rather indicated decreased tamoxifen responsiveness. S6K1 amplification predicted reduced benefit from radiotherapy. This is the first study showing that S6K2 amplification and overexpression, like S6K1 amplification, have prognostic and treatment predictive significance in breast cancer.
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Affiliation(s)
- Gizeh Pérez-Tenorio
- Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
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48
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Fenton TR, Gout IT. Functions and regulation of the 70kDa ribosomal S6 kinases. Int J Biochem Cell Biol 2010; 43:47-59. [PMID: 20932932 DOI: 10.1016/j.biocel.2010.09.018] [Citation(s) in RCA: 250] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Revised: 09/17/2010] [Accepted: 09/23/2010] [Indexed: 01/01/2023]
Abstract
The 70kDa ribosomal protein S6 kinases, S6K1 and S6K2 are two highly homologous serine/threonine kinases that are activated in response to growth factors, cytokines and nutrients. The S6 kinases have been linked to diverse cellular processes, including protein synthesis, mRNA processing, glucose homeostasis, cell growth and survival. Studies in model organisms have highlighted the roles that S6K activity plays in a number of pathologies, including obesity, diabetes, ageing and cancer. The importance of S6K function in human diseases has led to the development of S6K-specific inhibitors by a number of companies, offering the promise of improved tools with which to study these enzymes and potentially the effective targeting of deregulated S6K signalling in patients. Here we review the current literature on the role of S6Ks in the regulation of cell growth, survival and proliferation downstream of various signalling pathways and how their dysregulation contributes to the pathogenesis of human diseases.
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Affiliation(s)
- Tim R Fenton
- Ludwig Institute for Cancer Research, University of California San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0660, USA
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49
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Pearce L, Alton G, Richter D, Kath J, Lingardo L, Chapman J, Hwang C, Alessi D. Characterization of PF-4708671, a novel and highly specific inhibitor of p70 ribosomal S6 kinase (S6K1). Biochem J 2010; 431:245-55. [DOI: 10.1042/bj20101024] [Citation(s) in RCA: 213] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
S6K1 (p70 ribosomal S6 kinase 1) is activated by insulin and growth factors via the PI3K (phosphoinositide 3-kinase) and mTOR (mammalian target of rapamycin) signalling pathways. S6K1 regulates numerous processes, such as protein synthesis, growth, proliferation and longevity, and its inhibition has been proposed as a strategy for the treatment of cancer and insulin resistance. In the present paper we describe a novel cell-permeable inhibitor of S6K1, PF-4708671, which specifically inhibits the S6K1 isoform with a Ki of 20 nM and IC50 of 160 nM. PF-4708671 prevents the S6K1-mediated phosphorylation of S6 protein in response to IGF-1 (insulin-like growth factor 1), while having no effect upon the PMA-induced phosphorylation of substrates of the highly related RSK (p90 ribosomal S6 kinase) and MSK (mitogen- and stress-activated kinase) kinases. PF-4708671 was also found to induce phosphorylation of the T-loop and hydrophobic motif of S6K1, an effect that is dependent upon mTORC1 (mTOR complex 1). PF-4708671 is the first S6K1-specific inhibitor to be reported and will be a useful tool for delineating S6K1-specific roles downstream of mTOR.
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50
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Goh ETH, Pardo OE, Michael N, Niewiarowski A, Totty N, Volkova D, Tsaneva IR, Seckl MJ, Gout I. Involvement of heterogeneous ribonucleoprotein F in the regulation of cell proliferation via the mammalian target of rapamycin/S6 kinase 2 pathway. J Biol Chem 2010; 285:17065-76. [PMID: 20308064 DOI: 10.1074/jbc.m109.078782] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The S6 kinases (S6Ks) have been linked to a number of cellular processes, including translation, insulin metabolism, cell survival, and RNA splicing. Signaling via the phosphotidylinositol 3-kinase and mammalian target of rapamycin (mTOR) pathways is critical in regulating the activity and subcellular localization of S6Ks. To date, nuclear functions of both S6K isoforms, S6K1 and S6K2, are not well understood. To better understand S6K nuclear roles, we employed affinity purification of S6Ks from nuclear preparations followed by mass spectrometry analysis for the identification of novel binding partners. In this study, we report that in contrast to S6K1, the S6K2 isoform specifically associates with a number of RNA-binding proteins, including heterogeneous ribonucleoproteins (hnRNPs). We focused on studying the mechanism and physiological relevance of the S6K2 interaction with hnRNP F/H. Interestingly, the S6K2-hnRNP F/H interaction was not affected by mitogenic stimulation, whereas mTOR binding to hnRNP F/H was induced by serum stimulation. In addition, we define a new role of hnRNP F in driving cell proliferation, which could be partially attenuated by rapamycin treatment. S6K2-driven cell proliferation, on the other hand, could be blocked by small interfering RNA-mediated down-regulation of hnRNP F. These results demonstrate that the specific interaction between mTOR and S6K2 with hnRNPs is implicated in the regulation of cell proliferation.
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Affiliation(s)
- Eddy T H Goh
- Research Department of Structural and Molecular Biology, University College London, London WC1E 6BT, United Kingdom
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