1
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Tang X, Balachandran RC, Aschner M, Bowman AB. IGF/mTORC1/S6 Signaling Is Potentiated and Prolonged by Acute Loading of Subtoxicological Manganese Ion. Biomolecules 2023; 13:1229. [PMID: 37627294 PMCID: PMC10452562 DOI: 10.3390/biom13081229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2023] [Revised: 08/01/2023] [Accepted: 08/04/2023] [Indexed: 08/27/2023] Open
Abstract
The insulin-like growth factor (IGF)/insulin signaling (IIS) pathway is involved in cellular responses against intracellular divalent manganese ion (Mn2+) accumulation. As a pathway where multiple nodes utilize Mn2+ as a metallic co-factor, how the IIS signaling patterns are affected by Mn2+ overload is unresolved. In our prior studies, acute Mn2+ exposure potentiated IIS kinase activity upon physiological-level stimulation, indicated by elevated phosphorylation of protein kinase B (PKB, also known as AKT). AKT phosphorylation is associated with IIS activity; and provides direct signaling transduction input for the mammalian target of rapamycin complex 1 (mTORC1) and its downstream target ribosomal protein S6 (S6). Here, to better define the impact of Mn2+ exposure on IIS function, Mn2+-induced IIS activation was evaluated with serial concentrations and temporal endpoints. In the wild-type murine striatal neuronal line STHdh, the acute treatment of Mn2+ with IGF induced a Mn2+ concentration-sensitive phosphorylation of S6 at Ser235/236 to as low as 5 μM extracellular Mn2+. This effect required both the essential amino acids and insulin receptor (IR)/IGF receptor (IGFR) signaling input. Similar to simultaneous stimulation of Mn2+ and IGF, when a steady-state elevation of Mn2+ was established via a 24-h pre-exposure, phosphorylation of S6 also displayed higher sensitivity to sub-cytotoxic Mn2+ when compared to AKT phosphorylation at Ser473. This indicates a synergistic effect of sub-cytotoxic Mn2+ on IIS and mTORC1 signaling. Furthermore, elevated intracellular Mn2+, with both durations, led to a prolonged activation in AKT and S6 upon stimulation. Our data demonstrate that the downstream regulator S6 is a highly sensitive target of elevated Mn2+ and is well below the established acute cytotoxicity thresholds (<50 μM). These findings indicate that the IIS/mTORC1 pathways, in which Mn2+ normally serves as an essential co-factor, are dually responsible for the cellular changes in exposures to real-world Mn2+ concentrations.
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Affiliation(s)
- Xueqi Tang
- School of Health Sciences, Purdue University, West Lafayette, IN 47907, USA; (X.T.)
| | - Rekha C. Balachandran
- School of Health Sciences, Purdue University, West Lafayette, IN 47907, USA; (X.T.)
- Exponent Inc., Alexandria, VA 22314, USA
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Aaron B. Bowman
- School of Health Sciences, Purdue University, West Lafayette, IN 47907, USA; (X.T.)
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2
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Shi F, Collins S. Regulation of mTOR Signaling: Emerging Role of Cyclic Nucleotide-Dependent Protein Kinases and Implications for Cardiometabolic Disease. Int J Mol Sci 2023; 24:11497. [PMID: 37511253 PMCID: PMC10380887 DOI: 10.3390/ijms241411497] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 07/07/2023] [Accepted: 07/13/2023] [Indexed: 07/30/2023] Open
Abstract
The mechanistic target of rapamycin (mTOR) kinase is a central regulator of cell growth and metabolism. It is the catalytic subunit of two distinct large protein complexes, mTOR complex 1 (mTORC1) and mTORC2. mTOR activity is subjected to tight regulation in response to external nutrition and growth factor stimulation. As an important mechanism of signaling transduction, the 'second messenger' cyclic nucleotides including cAMP and cGMP and their associated cyclic nucleotide-dependent kinases, including protein kinase A (PKA) and protein kinase G (PKG), play essential roles in mediating the intracellular action of a variety of hormones and neurotransmitters. They have also emerged as important regulators of mTOR signaling in various physiological and disease conditions. However, the mechanism by which cAMP and cGMP regulate mTOR activity is not completely understood. In this review, we will summarize the earlier work establishing the ability of cAMP to dampen mTORC1 activation in response to insulin and growth factors and then discuss our recent findings demonstrating the regulation of mTOR signaling by the PKA- and PKG-dependent signaling pathways. This signaling framework represents a new non-canonical regulation of mTOR activity that is independent of AKT and could be a novel mechanism underpinning the action of a variety of G protein-coupled receptors that are linked to the mTOR signaling network. We will further review the implications of these signaling events in the context of cardiometabolic disease, such as obesity, non-alcoholic fatty liver disease, and cardiac remodeling. The metabolic and cardiac phenotypes of mouse models with targeted deletion of Raptor and Rictor, the two essential components for mTORC1 and mTORC2, will be summarized and discussed.
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Affiliation(s)
- Fubiao Shi
- Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Sheila Collins
- Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
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3
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Phosphorylation Signals Downstream of Dopamine Receptors in Emotional Behaviors: Association with Preference and Avoidance. Int J Mol Sci 2022; 23:ijms231911643. [PMID: 36232945 PMCID: PMC9570387 DOI: 10.3390/ijms231911643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 09/26/2022] [Accepted: 09/28/2022] [Indexed: 11/09/2022] Open
Abstract
Dopamine regulates emotional behaviors, including rewarding and aversive behaviors, through the mesolimbic dopaminergic pathway, which projects dopamine neurons from the ventral tegmental area to the nucleus accumbens (NAc). Protein phosphorylation is critical for intracellular signaling pathways and physiological functions, which are regulated by neurotransmitters in the brain. Previous studies have demonstrated that dopamine stimulated the phosphorylation of intracellular substrates, such as receptors, ion channels, and transcription factors, to regulate neuronal excitability and synaptic plasticity through dopamine receptors. We also established a novel database called KANPHOS that provides information on phosphorylation signals downstream of monoamines identified by our kinase substrate screening methods, including dopamine, in addition to those reported in the literature. Recent advances in proteomics techniques have enabled us to clarify the mechanisms through which dopamine controls rewarding and aversive behaviors through signal pathways in the NAc. In this review, we discuss the intracellular phosphorylation signals regulated by dopamine in these two emotional behaviors.
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4
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Xu H, Fang B, Bao C, Mao X, Zhu C, Ye L, Liu Q, Li Y, Du C, Qi H, Zhang X, Guan Y. The Prostaglandin E2 Receptor EP4 Promotes Vascular Neointimal Hyperplasia through Translational Control of Tenascin C via the cAPM/PKA/mTORC1/rpS6 Pathway. Cells 2022; 11:cells11172720. [PMID: 36078128 PMCID: PMC9454981 DOI: 10.3390/cells11172720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 08/27/2022] [Accepted: 08/29/2022] [Indexed: 12/05/2022] Open
Abstract
Prostaglandin E2 (PGE2) is an important metabolite of arachidonic acid which plays a crucial role in vascular physiology and pathophysiology via its four receptors (EP1-4). However, the role of vascular smooth muscle cell (VSMC) EP4 in neointimal hyperplasia is largely unknown. Here we showed that VSMC-specific deletion of EP4 (VSMC-EP4) ameliorated, while VSMC-specific overexpression of human EP4 promoted, neointimal hyperplasia in mice subjected to femoral artery wire injury or carotid artery ligation. In vitro studies revealed that pharmacological activation of EP4 promoted, whereas inhibition of EP4 suppressed, proliferation and migration of primary-cultured VSMCs. Mechanically, EP4 significantly increased the protein expression of tenascin C (TN-C), a pro-proliferative and pro-migratory extracellular matrix protein, at the translational level. Knockdown of TN-C markedly suppressed EP4 agonist-induced VSMC proliferation and migration. Further studies uncovered that EP4 upregulated TN-C protein expression via the PKA/mTORC1/Ribosomal protein S6 (rpS6) pathway. Together, our findings demonstrate that VSMC EP4 increases TN-C protein expression to promote neointimal hyperplasia via the PKA-mTORC1-rpS6 pathway. Therefore, VSMC EP4 may represent a potential therapeutic target for vascular restenosis.
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Affiliation(s)
- Hu Xu
- Advanced Institute for Medical Sciences, Dalian Medical University, Dalian 116041, China
| | - Bingying Fang
- Advanced Institute for Medical Sciences, Dalian Medical University, Dalian 116041, China
| | - Chengzhen Bao
- Advanced Institute for Medical Sciences, Dalian Medical University, Dalian 116041, China
| | - Xiuhui Mao
- Advanced Institute for Medical Sciences, Dalian Medical University, Dalian 116041, China
| | - Chunhua Zhu
- Advanced Institute for Medical Sciences, Dalian Medical University, Dalian 116041, China
| | - Lan Ye
- Advanced Institute for Medical Sciences, Dalian Medical University, Dalian 116041, China
| | - Qian Liu
- Advanced Institute for Medical Sciences, Dalian Medical University, Dalian 116041, China
| | - Yaqing Li
- Advanced Institute for Medical Sciences, Dalian Medical University, Dalian 116041, China
| | - Chunxiu Du
- Advanced Institute for Medical Sciences, Dalian Medical University, Dalian 116041, China
| | - Hang Qi
- Advanced Institute for Medical Sciences, Dalian Medical University, Dalian 116041, China
| | - Xiaoyan Zhang
- Health Science Center, East China Normal University, Shanghai 200241, China
- Correspondence: (X.Z.); (Y.G.)
| | - Youfei Guan
- Advanced Institute for Medical Sciences, Dalian Medical University, Dalian 116041, China
- Correspondence: (X.Z.); (Y.G.)
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5
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Ballerini P, Contursi A, Bruno A, Mucci M, Tacconelli S, Patrignani P. Inflammation and Cancer: From the Development of Personalized Indicators to Novel Therapeutic Strategies. Front Pharmacol 2022; 13:838079. [PMID: 35308229 PMCID: PMC8927697 DOI: 10.3389/fphar.2022.838079] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 02/09/2022] [Indexed: 12/15/2022] Open
Abstract
Colorectal (CRC) and hepatocellular carcinoma (HCC) are associated with chronic inflammation, which plays a role in tumor development and malignant progression. An unmet medical need in these settings is the availability of sensitive and specific noninvasive biomarkers. Their use will allow surveillance of high-risk populations, early detection, and monitoring of disease progression. Moreover, the characterization of specific fingerprints of patients with nonalcoholic fatty liver disease (NAFLD) without or with nonalcoholic steatohepatitis (NASH) at the early stages of liver fibrosis is necessary. Some lines of evidence show the contribution of platelets to intestinal and liver inflammation. Thus, low-dose Aspirin, an antiplatelet agent, reduces CRC and liver cancer incidence and mortality. Aspirin also produces antifibrotic effects in NAFLD. Activated platelets can trigger chronic inflammation and tissue fibrosis via the release of soluble mediators, such as thromboxane (TX) A2 and tumor growth factor (TGF)-β, and vesicles containing genetic material (including microRNA). These platelet-derived products contribute to cyclooxygenase (COX)-2 expression and prostaglandin (PG)E2 biosynthesis by tumor microenvironment cells, such as immune and endothelial cells and fibroblasts, alongside cancer cells. Enhanced COX-2-dependent PGE2 plays a crucial role in chronic inflammation and promotes tumor progression, angiogenesis, and metastasis. Antiplatelet agents can indirectly prevent the induction of COX-2 in target cells by inhibiting platelet activation. Differently, selective COX-2 inhibitors (coxibs) block the activity of COX-2 expressed in the tumor microenvironment and cancer cells. However, coxib chemopreventive effects are hampered by the interference with cardiovascular homeostasis via the coincident inhibition of vascular COX-2-dependent prostacyclin biosynthesis, resulting in enhanced risk of atherothrombosis. A strategy to improve anti-inflammatory agents' use in cancer prevention could be to develop tissue-specific drug delivery systems. Platelet ability to interact with tumor cells and transfer their molecular cargo can be employed to design platelet-mediated drug delivery systems to enhance the efficacy and reduce toxicity associated with anti-inflammatory agents in these settings. Another peculiarity of platelets is their capability to uptake proteins and transcripts from the circulation. Thus, cancer patient platelets show specific proteomic and transcriptomic expression profiles that could be used as biomarkers for early cancer detection and disease monitoring.
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Affiliation(s)
- Patrizia Ballerini
- Center for Advanced Studies and Technology (CAST), Chieti, Italy
- Department of Innovative Technologies in Medicine and Dentistry, Chieti, Italy
| | - Annalisa Contursi
- Center for Advanced Studies and Technology (CAST), Chieti, Italy
- Department of Neuroscience, Imaging and Clinical Science, G. d’Annunzio University, Chieti, Italy
| | - Annalisa Bruno
- Center for Advanced Studies and Technology (CAST), Chieti, Italy
- Department of Neuroscience, Imaging and Clinical Science, G. d’Annunzio University, Chieti, Italy
| | - Matteo Mucci
- Center for Advanced Studies and Technology (CAST), Chieti, Italy
- Department of Neuroscience, Imaging and Clinical Science, G. d’Annunzio University, Chieti, Italy
| | - Stefania Tacconelli
- Center for Advanced Studies and Technology (CAST), Chieti, Italy
- Department of Neuroscience, Imaging and Clinical Science, G. d’Annunzio University, Chieti, Italy
| | - Paola Patrignani
- Center for Advanced Studies and Technology (CAST), Chieti, Italy
- Department of Neuroscience, Imaging and Clinical Science, G. d’Annunzio University, Chieti, Italy
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6
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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: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [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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7
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Enhanced phosphorylation of S6 protein in mouse cortical layer V and subplate neurons. Neuroreport 2021; 31:762-769. [PMID: 32453020 DOI: 10.1097/wnr.0000000000001479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The mammalian neocortex is composed of six major layers of neurons. Each group of neurons in the cortical layers has distinct characteristics based on the expression of specific genes and connectivity patterns of neural circuits. Neuronal subtype transition and regional identity acquisition are established by temporal cues and interaction between several transcription factors during neurogenesis. The impairment of cortical lamination or neural circuits results in a wide range of neurodevelopmental disorders such as autism, schizophrenia, and certain forms of childhood epilepsy. Despite continuous efforts to classify neurons with the aid of genetic and epigenetic analyses, the neuron-specific properties associated with post-transcriptional modification remain unclear. In the present study, the distribution of phosphorylated S6-positive layers across the neocortex was examined using several layer markers. The development of pS6 S235/236 layers in layer V and the subplate was spatiotemporally regulated in the mouse brain. In addition, enhanced phosphorylation of ribosomal protein S6 in Ctip2-positive layer V neurons in vivo was sustained under in-vitro conditions using a culture of primary cortical neurons.
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8
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Moberg M, Apró W, Cervenka I, Ekblom B, van Hall G, Holmberg HC, Ruas JL, Blomstrand E. High-intensity leg cycling alters the molecular response to resistance exercise in the arm muscles. Sci Rep 2021; 11:6453. [PMID: 33742064 PMCID: PMC7979871 DOI: 10.1038/s41598-021-85733-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 03/02/2021] [Indexed: 11/09/2022] Open
Abstract
This study examined acute molecular responses to concurrent exercise involving different muscles. Eight men participated in a randomized crossover-trial with two sessions, one where they performed interval cycling followed by upper body resistance exercise (ER-Arm), and one with upper body resistance exercise only (R-Arm). Biopsies were taken from the triceps prior to and immediately, 90- and 180-min following exercise. Immediately after resistance exercise, the elevation in S6K1 activity was smaller and the 4E-BP1:eIF4E interaction greater in ER-Arm, but this acute attenuation disappeared during recovery. The protein synthetic rate in triceps was greater following exercise than at rest, with no difference between trials. The level of PGC-1α1 mRNA increased to greater extent in ER-Arm than R-Arm after 90 min of recovery, as was PGC-1α4 mRNA after both 90 and 180 min. Levels of MuRF-1 mRNA was unchanged in R-Arm, but elevated during recovery in ER-Arm, whereas MAFbx mRNA levels increased slightly in both trials. RNA sequencing in a subgroup of subjects revealed 862 differently expressed genes with ER-Arm versus R-Arm during recovery. These findings suggest that leg cycling prior to arm resistance exercise causes systemic changes that potentiate induction of specific genes in the triceps, without compromising the anabolic response.
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Affiliation(s)
- Marcus Moberg
- Department of Physiology, Nutrition and Biomechanics, Swedish School of Sport and Health Sciences, Stockholm, Sweden. .,The Swedish School of Sport and Health Sciences, Box 5626, 114 86, Stockholm, Sweden.
| | - William Apró
- Department of Physiology, Nutrition and Biomechanics, Swedish School of Sport and Health Sciences, Stockholm, Sweden.,Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Igor Cervenka
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Björn Ekblom
- Department of Physiology, Nutrition and Biomechanics, Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Gerrit van Hall
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Clinical Metabolomics Core Facility, Clinical Biochemistry, Rigshospitalet, Copenhagen, Denmark
| | | | - Jorge L Ruas
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Eva Blomstrand
- Department of Physiology, Nutrition and Biomechanics, Swedish School of Sport and Health Sciences, Stockholm, Sweden.,Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
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9
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Xie J, Shen K, Jones AT, Yang J, Tee AR, Shen MH, Yu M, Irani S, Wong D, Merrett JE, Lenchine RV, De Poi S, Jensen KB, Trim PJ, Snel MF, Kamei M, Martin SK, Fitter S, Tian S, Wang X, Butler LM, Zannettino ACW, Proud CG. Reciprocal signaling between mTORC1 and MNK2 controls cell growth and oncogenesis. Cell Mol Life Sci 2021; 78:249-270. [PMID: 32170339 PMCID: PMC11068017 DOI: 10.1007/s00018-020-03491-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 01/23/2020] [Accepted: 02/17/2020] [Indexed: 12/21/2022]
Abstract
eIF4E plays key roles in protein synthesis and tumorigenesis. It is phosphorylated by the kinases MNK1 and MNK2. Binding of MNKs to eIF4G enhances their ability to phosphorylate eIF4E. Here, we show that mTORC1, a key regulator of mRNA translation and oncogenesis, directly phosphorylates MNK2 on Ser74. This suppresses MNK2 activity and impairs binding of MNK2 to eIF4G. These effects provide a novel mechanism by which mTORC1 signaling impairs the function of MNK2 and thereby decreases eIF4E phosphorylation. MNK2[S74A] knock-in cells show enhanced phosphorylation of eIF4E and S6K1 (i.e., increased mTORC1 signaling), enlarged cell size, and increased invasive and transformative capacities. MNK2[Ser74] phosphorylation was inversely correlated with disease progression in human prostate tumors. MNK inhibition exerted anti-proliferative effects in prostate cancer cells in vitro. These findings define a novel feedback loop whereby mTORC1 represses MNK2 activity and oncogenic signaling through eIF4E phosphorylation, allowing reciprocal regulation of these two oncogenic pathways.
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Affiliation(s)
- Jianling Xie
- Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, 5000, Australia
| | - Kaikai Shen
- Medical Research Council Toxicology Unit, Leicester, UK
- School of Basic Medical Sciences, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China
| | - Ashley T Jones
- Division of Cancer and Genetics, Cardiff University, Heath Park, Cardiff, UK
| | - Jian Yang
- Division of Cancer and Genetics, Cardiff University, Heath Park, Cardiff, UK
| | - Andrew R Tee
- Division of Cancer and Genetics, Cardiff University, Heath Park, Cardiff, UK
| | - Ming Hong Shen
- Division of Cancer and Genetics, Cardiff University, Heath Park, Cardiff, UK
| | - Mengyuan Yu
- School of Basic Medical Sciences, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China
| | - Swati Irani
- Adelaide Medical School and Freemasons Foundation Centre for Men's Health, University of Adelaide, Adelaide, Australia
- Precision Medicine Theme, South Australian Health and Medical Research Institute, Adelaide, Australia
| | - Derick Wong
- Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, 5000, Australia
| | - James E Merrett
- Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, 5000, Australia
- Department of Molecular and Cellular Biology, University of Adelaide, Adelaide, Australia
| | - Roman V Lenchine
- Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, 5000, Australia
- Department of Molecular and Cellular Biology, University of Adelaide, Adelaide, Australia
| | - Stuart De Poi
- Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, 5000, Australia
- Department of Molecular and Cellular Biology, University of Adelaide, Adelaide, Australia
| | - Kirk B Jensen
- Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, 5000, Australia
- Department of Molecular and Cellular Biology, University of Adelaide, Adelaide, Australia
| | - Paul J Trim
- Hopwood Centre for Neurobiology, South Australian Health and Medical Research Institute, Adelaide, Australia
| | - Marten F Snel
- Hopwood Centre for Neurobiology, South Australian Health and Medical Research Institute, Adelaide, Australia
| | - Makoto Kamei
- Hopwood Centre for Neurobiology, South Australian Health and Medical Research Institute, Adelaide, Australia
| | - Sally Kim Martin
- Precision Medicine Theme, South Australian Health and Medical Research Institute, Adelaide, Australia
- Myeloma Research Laboratory, Adelaide Medical School, Faculty of Health and Medical Science, University of Adelaide, Adelaide, Australia
| | - Stephen Fitter
- Precision Medicine Theme, South Australian Health and Medical Research Institute, Adelaide, Australia
- Myeloma Research Laboratory, Adelaide Medical School, Faculty of Health and Medical Science, University of Adelaide, Adelaide, Australia
| | - Shuye Tian
- Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, 5000, Australia
- Department of Biology, Southern University of Science and Technology, Shenzhen, China
| | - Xuemin Wang
- Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, 5000, Australia
- Hopwood Centre for Neurobiology, South Australian Health and Medical Research Institute, Adelaide, Australia
| | - Lisa M Butler
- Adelaide Medical School and Freemasons Foundation Centre for Men's Health, University of Adelaide, Adelaide, Australia
- Precision Medicine Theme, South Australian Health and Medical Research Institute, Adelaide, Australia
| | - Andrew C W Zannettino
- Precision Medicine Theme, South Australian Health and Medical Research Institute, Adelaide, Australia
- Myeloma Research Laboratory, Adelaide Medical School, Faculty of Health and Medical Science, University of Adelaide, Adelaide, Australia
| | - Christopher G Proud
- Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA, 5000, Australia.
- Hopwood Centre for Neurobiology, South Australian Health and Medical Research Institute, Adelaide, Australia.
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10
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Multifaceted Functions of Platelets in Cancer: From Tumorigenesis to Liquid Biopsy Tool and Drug Delivery System. Int J Mol Sci 2020; 21:ijms21249585. [PMID: 33339204 PMCID: PMC7765591 DOI: 10.3390/ijms21249585] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 12/11/2020] [Accepted: 12/14/2020] [Indexed: 12/13/2022] Open
Abstract
Platelets contribute to several types of cancer through plenty of mechanisms. Upon activation, platelets release many molecules, including growth and angiogenic factors, lipids, and extracellular vesicles, and activate numerous cell types, including vascular and immune cells, fibroblasts, and cancer cells. Hence, platelets are a crucial component of cell-cell communication. In particular, their interaction with cancer cells can enhance their malignancy and facilitate the invasion and colonization of distant organs. These findings suggest the use of antiplatelet agents to restrain cancer development and progression. Another peculiarity of platelets is their capability to uptake proteins and transcripts from the circulation. Thus, cancer-patient platelets show specific proteomic and transcriptomic expression patterns, a phenomenon called tumor-educated platelets (TEP). The transcriptomic/proteomic profile of platelets can provide information for the early detection of cancer and disease monitoring. Platelet ability to interact with tumor cells and transfer their molecular cargo has been exploited to design platelet-mediated drug delivery systems to enhance the efficacy and reduce toxicity often associated with traditional chemotherapy. Platelets are extraordinary cells with many functions whose exploitation will improve cancer diagnosis and treatment.
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11
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Melick CH, Jewell JL. Regulation of mTORC1 by Upstream Stimuli. Genes (Basel) 2020; 11:genes11090989. [PMID: 32854217 PMCID: PMC7565831 DOI: 10.3390/genes11090989] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 08/22/2020] [Accepted: 08/23/2020] [Indexed: 01/08/2023] Open
Abstract
The mammalian target of rapamycin (mTOR) is an evolutionary conserved Ser/Thr protein kinase that senses multiple upstream stimuli to control cell growth, metabolism, and autophagy. mTOR is the catalytic subunit of mTOR complex 1 (mTORC1). A significant amount of research has uncovered the signaling pathways regulated by mTORC1, and the involvement of these signaling cascades in human diseases like cancer, diabetes, and ageing. Here, we review advances in mTORC1 regulation by upstream stimuli. We specifically focus on how growth factors, amino acids, G-protein coupled receptors (GPCRs), phosphorylation, and small GTPases regulate mTORC1 activity and signaling.
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Affiliation(s)
- Chase H. Melick
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA;
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jenna L. Jewell
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA;
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Correspondence:
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12
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Coles GL, Cristea S, Webber JT, Levin RS, Moss SM, He A, Sangodkar J, Hwang YC, Arand J, Drainas AP, Mooney NA, Demeter J, Spradlin JN, Mauch B, Le V, Shue YT, Ko JH, Lee MC, Kong C, Nomura DK, Ohlmeyer M, Swaney DL, Krogan NJ, Jackson PK, Narla G, Gordan JD, Shokat KM, Sage J. Unbiased Proteomic Profiling Uncovers a Targetable GNAS/PKA/PP2A Axis in Small Cell Lung Cancer Stem Cells. Cancer Cell 2020; 38:129-143.e7. [PMID: 32531271 PMCID: PMC7363571 DOI: 10.1016/j.ccell.2020.05.003] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 02/18/2020] [Accepted: 05/04/2020] [Indexed: 12/23/2022]
Abstract
Using unbiased kinase profiling, we identified protein kinase A (PKA) as an active kinase in small cell lung cancer (SCLC). Inhibition of PKA activity genetically, or pharmacologically by activation of the PP2A phosphatase, suppresses SCLC expansion in culture and in vivo. Conversely, GNAS (G-protein α subunit), a PKA activator that is genetically activated in a small subset of human SCLC, promotes SCLC development. Phosphoproteomic analyses identified many PKA substrates and mechanisms of action. In particular, PKA activity is required for the propagation of SCLC stem cells in transplantation studies. Broad proteomic analysis of recalcitrant cancers has the potential to uncover targetable signaling networks, such as the GNAS/PKA/PP2A axis in SCLC.
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Affiliation(s)
- Garry L Coles
- Department of Pediatrics, Stanford University, 265 Campus Drive, Stanford, CA 94305-5457, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Sandra Cristea
- Department of Pediatrics, Stanford University, 265 Campus Drive, Stanford, CA 94305-5457, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - James T Webber
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA 94158, USA
| | - Rebecca S Levin
- Howard Hughes Medical Institute, University of California San Francisco, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA
| | - Steven M Moss
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA
| | - Andy He
- Department of Pediatrics, Stanford University, 265 Campus Drive, Stanford, CA 94305-5457, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Jaya Sangodkar
- Division of Genetic Medicine, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Yeonjoo C Hwang
- Department of Medicine, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Julia Arand
- Department of Pediatrics, Stanford University, 265 Campus Drive, Stanford, CA 94305-5457, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Alexandros P Drainas
- Department of Pediatrics, Stanford University, 265 Campus Drive, Stanford, CA 94305-5457, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Nancie A Mooney
- Baxter Laboratory, Stanford University, Stanford, CA 94305, USA; Department of Microbiology & Immunology, Stanford University, Stanford, CA 94305, USA
| | - Janos Demeter
- Baxter Laboratory, Stanford University, Stanford, CA 94305, USA; Department of Microbiology & Immunology, Stanford University, Stanford, CA 94305, USA
| | - Jessica N Spradlin
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Brandon Mauch
- Department of Pediatrics, Stanford University, 265 Campus Drive, Stanford, CA 94305-5457, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Vicky Le
- Department of Pediatrics, Stanford University, 265 Campus Drive, Stanford, CA 94305-5457, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Yan Ting Shue
- Department of Pediatrics, Stanford University, 265 Campus Drive, Stanford, CA 94305-5457, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Julie H Ko
- Department of Pediatrics, Stanford University, 265 Campus Drive, Stanford, CA 94305-5457, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Myung Chang Lee
- Department of Pediatrics, Stanford University, 265 Campus Drive, Stanford, CA 94305-5457, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Christina Kong
- Department of Pathology, Stanford University, Stanford, CA 94305, USA
| | - Daniel K Nomura
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Michael Ohlmeyer
- Icahn School of Medicine at Mount Sinai, New York, NY, USA; Atux Iskay LLC, Plainsboro, New Jersey, NJ 08536, USA
| | - Danielle L Swaney
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA; Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, CA 94158, USA; David J. Gladstone Institute, University of California San Francisco, San Francisco, CA 94158, USA
| | - Nevan J Krogan
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA; Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, CA 94158, USA; David J. Gladstone Institute, University of California San Francisco, San Francisco, CA 94158, USA
| | - Peter K Jackson
- Baxter Laboratory, Stanford University, Stanford, CA 94305, USA; Department of Microbiology & Immunology, Stanford University, Stanford, CA 94305, USA; Department of Pathology, Stanford University, Stanford, CA 94305, USA
| | - Goutham Narla
- Division of Genetic Medicine, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - John D Gordan
- Department of Medicine, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143, USA; Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, CA 94158, USA
| | - Kevan M Shokat
- Howard Hughes Medical Institute, University of California San Francisco, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA
| | - Julien Sage
- Department of Pediatrics, Stanford University, 265 Campus Drive, Stanford, CA 94305-5457, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA.
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13
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Folgueira C, Beiroa D, Porteiro B, Duquenne M, Puighermanal E, Fondevila MF, Barja-Fernández S, Gallego R, Hernández-Bautista R, Castelao C, Senra A, Seoane P, Gómez N, Aguiar P, Guallar D, Fidalgo M, Romero-Pico A, Adan R, Blouet C, Labandeira-García JL, Jeanrenaud F, Kallo I, Liposits Z, Salvador J, Prevot V, Dieguez C, Lopez M, Valjent E, Frühbeck G, Seoane LM, Nogueiras R. Hypothalamic dopamine signaling regulates brown fat thermogenesis. Nat Metab 2019; 1:811-829. [PMID: 31579887 PMCID: PMC6774781 DOI: 10.1038/s42255-019-0099-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Dopamine signaling is a crucial part of the brain reward system and can affect feeding behavior. Dopamine receptors are also expressed in the hypothalamus, which is known to control energy metabolism in peripheral tissues. Here we show that pharmacological or chemogenetic stimulation of dopamine receptor 2 (D2R) expressing cells in the lateral hypothalamic area (LHA) and the zona incerta (ZI) decreases body weight and stimulates brown fat activity in rodents in a feeding-independent manner. LHA/ZI D2R stimulation requires an intact sympathetic nervous system and orexin system to exert its action and involves inhibition of PI3K in the LHA/ZI. We further demonstrate that, as early as 3 months after onset of treatment, patients treated with the D2R agonist cabergoline experience an increase in energy expenditure that persists for one year, leading to total body weight and fat loss through a prolactin-independent mechanism. Our results may provide a mechanistic explanation for how clinically used D2R agonists act in the CNS to regulate energy balance.
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Affiliation(s)
- Cintia Folgueira
- Grupo Fisiopatología Endocrina, Instituto de Investigación Sanitaria de Santiago de Compostela, Complexo. Hospitalario Universitario de Santiago (CHUS/SERGAS), Instituto de Investigación Sanitaria, Santiago de Compostela, Travesía da Choupana s/n, 15706 Santiago de Compostela, Spain
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Daniel Beiroa
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Begoña Porteiro
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Manon Duquenne
- Jean-Pierre Aubert Research Center (JPArc), Laboratory of Development and Plasticity of the Neuroendocrine Brain, Inserm UMR-S 1172, Lille, France
| | | | - Marcos F Fondevila
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Silvia Barja-Fernández
- Grupo Fisiopatología Endocrina, Instituto de Investigación Sanitaria de Santiago de Compostela, Complexo. Hospitalario Universitario de Santiago (CHUS/SERGAS), Instituto de Investigación Sanitaria, Santiago de Compostela, Travesía da Choupana s/n, 15706 Santiago de Compostela, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Rosalia Gallego
- Department of Morphological Sciences, School of Medicine, University of Santiago de Compostela, S. Francisco s/n, 15782 Santiago de Compostela (A Coruña), Spain
| | - René Hernández-Bautista
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
| | - Cecilia Castelao
- Grupo Fisiopatología Endocrina, Instituto de Investigación Sanitaria de Santiago de Compostela, Complexo. Hospitalario Universitario de Santiago (CHUS/SERGAS), Instituto de Investigación Sanitaria, Santiago de Compostela, Travesía da Choupana s/n, 15706 Santiago de Compostela, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Ana Senra
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
| | - Patricia Seoane
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Noemi Gómez
- Molecular Imaging Group, Department of Psychiatry, Radiology and Public Health, Faculty of Medicine Universidade de Santiago de Compostela (USC), Santiago de Compostela 15782 Spain; Molecular Imaging Group. Health Research Institute of Santiago de Compostela (IDIS). Travesía da Choupana s/n Santiago de Compostela. Zip Code: 15706. Spain; Nuclear Medicine Department University Clinical Hospital Santiago de Compostela (SERGAS) (CHUS), Travesía Choupana s/n. Santiago de Compostela 15706 Spain
| | - Pablo Aguiar
- Molecular Imaging Group, Department of Psychiatry, Radiology and Public Health, Faculty of Medicine Universidade de Santiago de Compostela (USC), Santiago de Compostela 15782 Spain; Molecular Imaging Group. Health Research Institute of Santiago de Compostela (IDIS). Travesía da Choupana s/n Santiago de Compostela. Zip Code: 15706. Spain; Nuclear Medicine Department University Clinical Hospital Santiago de Compostela (SERGAS) (CHUS), Travesía Choupana s/n. Santiago de Compostela 15706 Spain
| | - Diana Guallar
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
| | - Miguel Fidalgo
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
| | - Amparo Romero-Pico
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Roger Adan
- Brain Center Rudolf Magnus, Department of Neuroscience and Pharmacology, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands
| | - Clemence Blouet
- MRC Metabolic Disease Unit. Institute of Metabolic Science. University of Cambridge, UK
| | - Jose Luís Labandeira-García
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
- Networking Research Center on Neurodegenerative Diseases, CIBERNED, Madrid, Spain
| | - Françoise Jeanrenaud
- Laboratory of Metabolism, Division of Endocrinology, Diabetology and Nutrition, Department of Internal Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Imre Kallo
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, HAS, 1083, Budapest, Hungary
| | - Zsolt Liposits
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, HAS, 1083, Budapest, Hungary
| | - Javier Salvador
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
- Department of Endocrinology & Nutrition, Clínica Universidad de Navarra & IdiSNA, Pamplona, Spain
| | - Vincent Prevot
- Jean-Pierre Aubert Research Center (JPArc), Laboratory of Development and Plasticity of the Neuroendocrine Brain, Inserm UMR-S 1172, Lille, France
| | - Carlos Dieguez
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Miguel Lopez
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Emmanuel Valjent
- IGF, Inserm, CNRS, Univ. Montpellier, F-34094 Montpellier, France
| | - Gema Frühbeck
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
- Department of Endocrinology & Nutrition, Clínica Universidad de Navarra & IdiSNA, Pamplona, Spain
| | - Luisa M Seoane
- Grupo Fisiopatología Endocrina, Instituto de Investigación Sanitaria de Santiago de Compostela, Complexo. Hospitalario Universitario de Santiago (CHUS/SERGAS), Instituto de Investigación Sanitaria, Santiago de Compostela, Travesía da Choupana s/n, 15706 Santiago de Compostela, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Ruben Nogueiras
- CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
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14
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Romeo V, Gierke S, Edgar KA, Liu SD. Effects of PI3K Inhibition on Afucosylated Antibody-Driven FcγRIIIa Events and Phospho-S6 Activity in NK Cells. THE JOURNAL OF IMMUNOLOGY 2019; 203:137-147. [PMID: 31092639 DOI: 10.4049/jimmunol.1801418] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 04/20/2019] [Indexed: 11/19/2022]
Abstract
PI3K is one of the most frequently mutated genes in cancers and has been the target of numerous anticancer therapies. With the additional development of therapeutics that mobilize the immune system, such as Abs with effector functions, bispecific Abs, and checkpoint inhibitors, many small molecule inhibitors that target PI3K are being combined with these immunomodulatory treatments. However, the PI3K pathway is also essential for lymphocyte function, and the presence of the PI3K inhibitor may render the immunomodulatory therapeutic ineffective in these combinatorial treatments. Therefore, therapeutics with enhanced activity, such as afucosylated Abs, which promote signaling and function, may be ideal in these types of treatments to offset the negative effect of PI3K inhibitors on immune cell function. Indeed, we show that afucosylated Abs can counterbalance these inhibitory effects on FcγRIIIa-driven signaling in human NK cells to produce signals similar to cells treated only with fucosylated Ab. Furthermore, NK cell activation, degranulation, chemokine/cytokine production, and Ab-dependent cellular cytotoxicity were similar between inhibitor-treated, afucosylated Ab-stimulated NK cells and cells activated only with its fucosylated counterpart. To our knowledge, these studies also identified a previously undefined role for phospho-S6 in human NK cells. In this study, a kinetic delay in PI3K-driven phosphorylation of S6 was observed to control transcription of the temporally regulated production of IFN-γ and TNF-α but not MIP-1α, MIP-1β, and RANTES. Together, these studies demonstrate the importance of the PI3K pathway for S6 phosphorylation in human NK cells and the need to combine PI3K inhibitors with therapeutic molecules that enhance immunomodulatory function for anticancer therapies.
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Affiliation(s)
- Valentina Romeo
- Department of Cancer Immunology, Genentech, Inc., South San Francisco, CA 94080
| | - Sarah Gierke
- Department of Pathology, Genentech, Inc., South San Francisco, CA 94080; and
| | - Kyle A Edgar
- Department of Translation Oncology, Genentech, Inc., South San Francisco, CA 94080
| | - Scot D Liu
- Department of Pathology, Genentech, Inc., South San Francisco, CA 94080; and
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15
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Novel AU-rich proximal UTR sequences (APS) enhance CXCL8 synthesis upon the induction of rpS6 phosphorylation. PLoS Genet 2019; 15:e1008077. [PMID: 30969964 PMCID: PMC6476525 DOI: 10.1371/journal.pgen.1008077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2018] [Revised: 04/22/2019] [Accepted: 03/09/2019] [Indexed: 11/19/2022] Open
Abstract
The role of ribosomal protein S6 (rpS6) phosphorylation in mRNA translation remains poorly understood. Here, we reveal a potential role in modulating the translation rate of chemokine (C-X-C motif) ligand 8 (CXCL8 or Interleukin 8, IL8). We observed that more CXCL8 protein was being secreted from less CXCL8 mRNA in primary macrophages and macrophage-like HL-60 cells relative to other cell types. This correlated with an increase in CXCL8 polyribosome association, suggesting an increase in the rate of CXCL8 translation in macrophages. The cell type-specific expression levels were replicated by a CXCL8- UTR-reporter (Nanoluc reporter flanked by the 5' and 3' UTR of CXCL8). Mutations of the CXCL8-UTR-reporter revealed that cell type-specific expression required: 1) a 3' UTR of at least three hundred bases; and 2) an AU base content that exceeds fifty percent in the first hundred bases of the 3' UTR immediately after the stop codon, which we dub AU-rich proximal UTR sequences (APS). The 5' UTR of CXCL8 enhanced expression at the protein level and conferred cell type-specific expression when paired with a 3' UTR. A search for other APS-positive mRNAs uncovered TNF alpha induced protein 6 (TNFAIP6), another mRNA that was translationally upregulated in macrophages. The elevated translation of APS-positive mRNAs in macrophages coincided with elevated rpS6 S235/236 phosphorylation. Both were attenuated by the ERK1/2 signaling inhibitors, U0126 and AZD6244. In A549 cells, rpS6 S235/236 phosphorylation was induced by TAK1, Akt or PKA signaling. This enhanced the translation of the CXCL8-UTR-reporters. Thus, we propose that the induction of rpS6 S235/236 phosphorylation enhances the translation of mRNAs that contain APS motifs, such as CXCL8 and TNFAIP6. This may contribute to the role of macrophages as the primary producer of CXCL8, a cytokine that is essential for immune cell recruitment and activation.
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16
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Kalwat MA, Hwang IH, Macho J, Grzemska MG, Yang JZ, McGlynn K, MacMillan JB, Cobb MH. Chromomycin A 2 potently inhibits glucose-stimulated insulin secretion from pancreatic β cells. J Gen Physiol 2018; 150:1747-1757. [PMID: 30352794 PMCID: PMC6279362 DOI: 10.1085/jgp.201812177] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 09/10/2018] [Indexed: 12/31/2022] Open
Abstract
Drugs that target insulin secretion are useful to understand β cell function and the pathogenesis of diabetes. Kalwat et al. investigate an aureolic acid that inhibits insulin secretion and reveal that it disrupts Wnt signaling, interferes with gene expression, and suppresses Ca2+ influx in β cells. Modulators of insulin secretion could be used to treat diabetes and as tools to investigate β cell regulatory pathways in order to increase our understanding of pancreatic islet function. Toward this goal, we previously used an insulin-linked luciferase that is cosecreted with insulin in MIN6 β cells to perform a high-throughput screen of natural products for chronic effects on glucose-stimulated insulin secretion. In this study, using multiple phenotypic analyses, we found that one of the top natural product hits, chromomycin A2 (CMA2), potently inhibited insulin secretion by at least three potential mechanisms: disruption of Wnt signaling, interference of β cell gene expression, and partial suppression of Ca2+ influx. Chronic treatment with CMA2 largely ablated glucose-stimulated insulin secretion even after washout, but it did not inhibit glucose-stimulated generation of ATP or Ca2+ influx. However, by using the KATP channel opener diazoxide, we uncovered defects in depolarization-induced Ca2+ influx that may contribute to the suppressed secretory response. Glucose-responsive ERK1/2 and S6 phosphorylation were also disrupted by chronic CMA2 treatment. By querying the FUSION bioinformatic database, we revealed that the phenotypic effects of CMA2 cluster with a number of Wnt–GSK3 pathway-related genes. Furthermore, CMA2 consistently decreased GSK3β phosphorylation and suppressed activation of a β-catenin activity reporter. CMA2 and a related compound, mithramycin, are known to have DNA interaction properties, possibly abrogating transcription factor binding to critical β cell gene promoters. We observed that CMA2 but not mithramycin suppressed expression of PDX1 and UCN3. However, neither expression of INSI/II nor insulin content was affected by chronic CMA2. The mechanisms of CMA2-induced insulin secretion defects may involve components both proximal and distal to Ca2+ influx. Therefore, CMA2 is an example of a chemical that can simultaneously disrupt β cell function through both noncytotoxic and cytotoxic mechanisms. Future therapeutic applications of CMA2 and similar aureolic acid analogues should consider their potential effects on pancreatic islet function.
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Affiliation(s)
- Michael A Kalwat
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX
| | - In Hyun Hwang
- Department of Pharmacy, Woosuk University, Wanju, South Korea
| | - Jocelyn Macho
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA
| | - Magdalena G Grzemska
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Jonathan Z Yang
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Kathleen McGlynn
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX
| | - John B MacMillan
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA
| | - Melanie H Cobb
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX
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17
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Abstract
Lymphangioleiomyomatosis (LAM), a rare disease of women, is associated with cystic lung destruction resulting from the proliferation of abnormal smooth muscle-like LAM cells with mutations in the tuberous sclerosis complex (TSC) genes TSC1 and/or TSC2 The mutant genes and encoded proteins are responsible for activation of the mechanistic target of rapamycin (mTOR), which is inhibited by sirolimus (rapamycin), a drug used to treat LAM. Patients who have LAM may also be treated with bronchodilators for asthma-like symptoms due to LAM. We observed stabilization of forced expiratory volume in 1 s over time in patients receiving sirolimus and long-acting beta-agonists with short-acting rescue inhalers compared with patients receiving only sirolimus. Because beta-agonists increase cAMP and PKA activity, we investigated effects of PKA activation on the mTOR pathway. Human skin TSC2+/- fibroblasts or LAM lung cells incubated short-term with isoproterenol (beta-agonist) showed a sirolimus-independent increase in phosphorylation of S6, a downstream effector of the mTOR pathway, and increased cell growth. Cells incubated long-term with isoproterenol, which may lead to beta-adrenergic receptor desensitization, did not show increased S6 phosphorylation. Inhibition of PKA blocked the isoproterenol effect on S6 phosphorylation. Thus, activation of PKA by beta-agonists increased phospho-S6 independent of mTOR, an effect abrogated by beta-agonist-driven receptor desensitization. In agreement, retrospective clinical data from patients with LAM suggested that a combination of bronchodilators in conjunction with sirolimus may be preferable to sirolimus alone for stabilization of pulmonary function.
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18
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Puighermanal E, Biever A, Pascoli V, Melser S, Pratlong M, Cutando L, Rialle S, Severac D, Boubaker-Vitre J, Meyuhas O, Marsicano G, Lüscher C, Valjent E. Ribosomal Protein S6 Phosphorylation Is Involved in Novelty-Induced Locomotion, Synaptic Plasticity and mRNA Translation. Front Mol Neurosci 2017; 10:419. [PMID: 29311811 PMCID: PMC5742586 DOI: 10.3389/fnmol.2017.00419] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 12/01/2017] [Indexed: 11/29/2022] Open
Abstract
The phosphorylation of the ribosomal protein S6 (rpS6) is widely used to track neuronal activity. Although it is generally assumed that rpS6 phosphorylation has a stimulatory effect on global protein synthesis in neurons, its exact biological function remains unknown. By using a phospho-deficient rpS6 knockin mouse model, we directly tested the role of phospho-rpS6 in mRNA translation, plasticity and behavior. The analysis of multiple brain areas shows for the first time that, in neurons, phospho-rpS6 is dispensable for overall protein synthesis. Instead, we found that phospho-rpS6 controls the translation of a subset of mRNAs in a specific brain region, the nucleus accumbens (Acb), but not in the dorsal striatum. We further show that rpS6 phospho-mutant mice display altered long-term potentiation (LTP) in the Acb and enhanced novelty-induced locomotion. Collectively, our findings suggest a previously unappreciated role of phospho-rpS6 in the physiology of the Acb, through the translation of a selective subclass of mRNAs, rather than the regulation of general protein synthesis.
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Affiliation(s)
| | - Anne Biever
- IGF, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Vincent Pascoli
- Department of Basic Neurosciences, Medical Faculty, University of Geneva, Geneva, Switzerland
| | - Su Melser
- INSERM U1215, Université de Bordeaux, NeuroCentre Magendie, Bordeaux, France
| | - Marine Pratlong
- Montpellier GenomiX, BioCampus Montpellier, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Laura Cutando
- IGF, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Stephanie Rialle
- Montpellier GenomiX, BioCampus Montpellier, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Dany Severac
- Montpellier GenomiX, BioCampus Montpellier, CNRS, INSERM, University of Montpellier, Montpellier, France
| | | | - Oded Meyuhas
- Department of Biochemistry and Molecular Biology, IMRIC, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Giovanni Marsicano
- INSERM U1215, Université de Bordeaux, NeuroCentre Magendie, Bordeaux, France
| | - Christian Lüscher
- Department of Basic Neurosciences, Medical Faculty, University of Geneva, Geneva, Switzerland.,Clinic of Neurology, Department of Clinical Neurosciences, Geneva University Hospital, Geneva, Switzerland
| | - Emmanuel Valjent
- IGF, CNRS, INSERM, University of Montpellier, Montpellier, France
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19
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Rajamäki ML, Xi D, Sikorskaite-Gudziuniene S, Valkonen JPT, Whitham SA. Differential Requirement of the Ribosomal Protein S6 and Ribosomal Protein S6 Kinase for Plant-Virus Accumulation and Interaction of S6 Kinase with Potyviral VPg. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2017; 30:374-384. [PMID: 28437137 DOI: 10.1094/mpmi-06-16-0122-r] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Ribosomal protein S6 (RPS6) is an indispensable plant protein regulated, in part, by ribosomal protein S6 kinase (S6K) which, in turn, is a key regulator of plant responses to stresses and developmental cues. Increased expression of RPS6 was detected in Nicotiana benthamiana during infection by diverse plant viruses. Silencing of the RPS6 and S6K genes in N. benthamiana affected accumulation of Cucumber mosaic virus, Turnip mosaic virus (TuMV), and Potato virus A (PVA) in contrast to Turnip crinkle virus and Tobacco mosaic virus. In addition, the viral genome-linked protein (VPg) of TuMV and PVA interacted with S6K in plant cells, as detected by bimolecular fluorescence complementation assay. The VPg-S6K interaction was detected in cytoplasm, nucleus, and nucleolus, whereas the green fluorescent protein-tagged S6K alone showed cytoplasmic localization only. These results demonstrate that the requirement for RPS6 and S6K differs for diverse plant viruses with different translation initiation strategies and suggest that potyviral VPg-S6K interaction may affect S6K functions in both the cytoplasm and the nucleus.
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Affiliation(s)
- Minna-Liisa Rajamäki
- 1 Department of Agricultural Sciences, P.O. Box 27, FI-00014 University of Helsinki, Helsinki, Finland
| | - Dehui Xi
- 2 College of Life Science, Sichuan University, Chengdu, 610064, China; and
| | | | - Jari P T Valkonen
- 1 Department of Agricultural Sciences, P.O. Box 27, FI-00014 University of Helsinki, Helsinki, Finland
| | - Steven A Whitham
- 3 Department of Plant Pathology and Microbiology, Iowa State University, Ames 50011, U.S.A
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20
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Low-Dose Aspirin Acetylates Cyclooxygenase-1 in Human Colorectal Mucosa: Implications for the Chemoprevention of Colorectal Cancer. Clin Pharmacol Ther 2017; 102:52-61. [DOI: 10.1002/cpt.639] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 01/19/2017] [Accepted: 01/21/2017] [Indexed: 12/18/2022]
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21
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Guerra ML, Kalwat MA, McGlynn K, Cobb MH. Sucralose activates an ERK1/2-ribosomal protein S6 signaling axis. FEBS Open Bio 2017; 7:174-186. [PMID: 28174684 PMCID: PMC5292669 DOI: 10.1002/2211-5463.12172] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 10/13/2016] [Accepted: 11/28/2016] [Indexed: 12/20/2022] Open
Abstract
The sweetener sucralose can signal through its GPCR receptor to induce insulin secretion from pancreatic β cells, but the downstream signaling pathways involved are not well‐understood. Here we measure responses to sucralose, glucagon‐like peptide 1, and amino acids in MIN6 β cells. Our data suggest a signaling axis, whereby sucralose induces calcium and cAMP, activation of ERK1/2, and site‐specific phosphorylation of ribosomal protein S6. Interestingly, sucralose acted independently of mTORC1 or ribosomal S6 kinase (RSK). These results suggest that sweeteners like sucralose can influence β‐cell responses to secretagogues like glucose through metabolic as well as GPCR‐mediated pathways. Future investigation of novel sweet taste receptor signaling pathways in β cells will have implications for diabetes and other emergent fields involving these receptors.
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Affiliation(s)
- Marcy L Guerra
- Department of Pharmacology UT Southwestern Medical Center Dallas TX USA; Present address: Stem Synergy Therapeutics Nashville TN USA
| | - Michael A Kalwat
- Department of Pharmacology UT Southwestern Medical Center Dallas TX USA
| | - Kathleen McGlynn
- Department of Pharmacology UT Southwestern Medical Center Dallas TX USA
| | - Melanie H Cobb
- Department of Pharmacology UT Southwestern Medical Center Dallas TX USA
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22
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Pirbhoy PS, Farris S, Steward O. Synaptic activation of ribosomal protein S6 phosphorylation occurs locally in activated dendritic domains. ACTA ACUST UNITED AC 2016; 23:255-69. [PMID: 27194793 PMCID: PMC4880148 DOI: 10.1101/lm.041947.116] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 03/07/2016] [Indexed: 01/08/2023]
Abstract
Previous studies have shown that induction of long-term potentiation (LTP) induces phosphorylation of ribosomal protein S6 (rpS6) in postsynaptic neurons, but the functional significance of rpS6 phosphorylation is poorly understood. Here, we show that synaptic stimulation that induces perforant path LTP triggers phosphorylation of rpS6 (p-rpS6) locally near active synapses. Using antibodies specific for phosphorylation at different sites (ser235/236 versus ser240/244), we show that strong synaptic activation led to dramatic increases in immunostaining throughout postsynaptic neurons with selectively higher staining for p-ser235/236 in the activated dendritic lamina. Following LTP induction, phosphorylation at ser235/236 was detectable by 5 min, peaked at 30 min, and was maintained for hours. Phosphorylation at both sites was completely blocked by local infusion of the NMDA receptor antagonist, APV. Despite robust induction of p-rpS6 following high frequency stimulation, assessment of protein synthesis by autoradiography revealed no detectable increases. Exploration of a novel environment led to increases in the number of p-rpS6-positive neurons throughout the forebrain in a pattern reminiscent of immediate early gene induction and many individual neurons that were p-rpS6-positive coexpressed Arc protein. Our results constrain hypotheses about the possible role of rpS6 phosphorylation in regulating postsynaptic protein synthesis during induction of synaptic plasticity.
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Affiliation(s)
- Patricia Salgado Pirbhoy
- Reeve-Irvine Research Center, Center for the Neurobiology of Learning and Memory Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory
| | - Shannon Farris
- Reeve-Irvine Research Center, Center for the Neurobiology of Learning and Memory Department of Anatomy and Neurobiology, University of California, Irvine, California 92697, USA
| | - Oswald Steward
- Reeve-Irvine Research Center, Center for the Neurobiology of Learning and Memory Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory Department of Anatomy and Neurobiology, University of California, Irvine, California 92697, USA Department of Neurosurgery, University of California, Irvine, California 92697, USA
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23
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Cheng Q, Beltran VD, Chan SMH, Brown JR, Bevington A, Herbert TP. System-L amino acid transporters play a key role in pancreatic β-cell signalling and function. J Mol Endocrinol 2016; 56:175-87. [PMID: 26647387 DOI: 10.1530/jme-15-0212] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The branched-chain amino acids (BCAA) leucine, isoleucine and valine, are essential amino acids that play a critical role in cellular signalling and metabolism. They acutely stimulate insulin secretion and activate the regulatory serine/threonine kinase mammalian target of rapamycin complex 1 (mTORC1), a kinase that promotes increased β-cell mass and function. The effects of BCAA on cellular function are dependent on their active transport into the mammalian cells via amino acid transporters and thus the expression and activity of these transporters likely influence β-cell signalling and function. In this report, we show that the System-L transporters are required for BCAA uptake into clonal β-cell lines and pancreatic islets, and that these are essential for signalling to mTORC1. Further investigation revealed that the System-L amino acid transporter 1 (LAT1) is abundantly expressed in the islets, and that knockdown of LAT1 using siRNA inhibits mTORC1 signalling, leucine-stimulated insulin secretion and islet cell proliferation. In summary, we show that the LAT1 is required for regulating β-cell signalling and function in islets and thus may be a novel pharmacological/nutritional target for the treatment and prevention of type 2 diabetes.
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Affiliation(s)
- Qi Cheng
- Research School of BiologyAustralian National University, Acton, Australia
| | - Violeta D Beltran
- Department of InfectionImmunity and Inflammation, University of Leicester, UK
| | - Stanley M H Chan
- Health Innovations Research Institute (HIRI)School of Medical Sciences, RMIT University, Bundoora, Australia
| | - Jeremy R Brown
- Department of InfectionImmunity and Inflammation, University of Leicester, UK
| | - Alan Bevington
- Department of InfectionImmunity and Inflammation, University of Leicester, UK
| | - Terence P Herbert
- Health Innovations Research Institute (HIRI)School of Medical Sciences, RMIT University, Bundoora, Australia
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24
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Biever A, Valjent E, Puighermanal E. Ribosomal Protein S6 Phosphorylation in the Nervous System: From Regulation to Function. Front Mol Neurosci 2015; 8:75. [PMID: 26733799 PMCID: PMC4679984 DOI: 10.3389/fnmol.2015.00075] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 11/23/2015] [Indexed: 01/31/2023] Open
Abstract
Since the discovery of the phosphorylation of the 40S ribosomal protein S6 (rpS6) about four decades ago, much effort has been made to uncover the molecular mechanisms underlying the regulation of this post-translational modification. In the field of neuroscience, rpS6 phosphorylation is commonly used as a readout of the mammalian target of rapamycin complex 1 signaling activation or as a marker for neuronal activity. Nevertheless, its biological role in neurons still remains puzzling. Here we review the pharmacological and physiological stimuli regulating this modification in the nervous system as well as the pathways that transduce these signals into rpS6 phosphorylation. Altered rpS6 phosphorylation observed in various genetic and pathophysiological mouse models is also discussed. Finally, we examine the current state of knowledge on the physiological role of this post-translational modification and highlight the questions that remain to be addressed.
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Affiliation(s)
- Anne Biever
- Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique FonctionnelleMontpellier, France; Institut National de la Santé et de la Recherche Médicale, U1191Montpellier, France; Université de Montpellier, UMR-5203Montpellier, France
| | - Emmanuel Valjent
- Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique FonctionnelleMontpellier, France; Institut National de la Santé et de la Recherche Médicale, U1191Montpellier, France; Université de Montpellier, UMR-5203Montpellier, France
| | - Emma Puighermanal
- Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique FonctionnelleMontpellier, France; Institut National de la Santé et de la Recherche Médicale, U1191Montpellier, France; Université de Montpellier, UMR-5203Montpellier, France
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25
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Ribosomal Protein S6 Phosphorylation: Four Decades of Research. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 320:41-73. [PMID: 26614871 DOI: 10.1016/bs.ircmb.2015.07.006] [Citation(s) in RCA: 182] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The phosphorylation of ribosomal protein S6 (rpS6) has been described for the first time about four decades ago. Since then, numerous studies have shown that this modification occurs in response to a wide variety of stimuli on five evolutionarily conserved serine residues. However, despite a large body of information on the respective kinases and the signal transduction pathways, the physiological role of rpS6 phosphorylation remained obscure until genetic manipulations were applied in both yeast and mammals in an attempt to block this modification. Thus, studies based on both mice and cultured cells subjected to disruption of the genes encoding rpS6 and the respective kinases, as well as the substitution of the phosphorylatable serine residues in rpS6, have laid the ground for the elucidation of the multiple roles of this protein and its posttranslational modification. This review focuses primarily on newly identified kinases that phosphorylate rpS6, pathways that transduce various signals into rpS6 phosphorylation, and the recently established physiological functions of this modification. It should be noted, however, that despite the significant progress made in the last decade, the molecular mechanism(s) underlying the diverse effects of rpS6 phosphorylation on cellular and organismal physiology are still poorly understood.
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26
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Network analysis of gene expression in mice provides new evidence of involvement of the mTOR pathway in antipsychotic-induced extrapyramidal symptoms. THE PHARMACOGENOMICS JOURNAL 2015; 16:293-300. [PMID: 26122020 DOI: 10.1038/tpj.2015.48] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 04/10/2015] [Accepted: 05/18/2015] [Indexed: 11/08/2022]
Abstract
To identify potential candidate genes for future pharmacogenetic studies of antipsychotic (AP)-induced extrapyramidal symptoms (EPS), we used gene expression arrays to analyze changes induced by risperidone in mice strains with different susceptibility to EPS. We proposed a systems biology analytical approach that combined the identification of gene co-expression modules related to AP treatment, the construction of protein-protein interaction networks with genes included in identified modules and finally, gene set enrichment analysis of constructed networks. In response to risperidone, mice strain with susceptibility to develop EPS showed downregulation of genes involved in the mammalian target of rapamycin (mTOR) pathway and biological processes related to this pathway. Moreover, we also showed differences in the phosphorylation pattern of the ribosomal protein S6 (rpS6), which is a major downstream effector of mTOR. The present study provides new evidence of the involvement of the mTOR pathway in AP-induced EPS and offers new and valuable markers for pharmacogenetic studies.
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27
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PKA-dependent phosphorylation of ribosomal protein S6 does not correlate with translation efficiency in striatonigral and striatopallidal medium-sized spiny neurons. J Neurosci 2015; 35:4113-30. [PMID: 25762659 DOI: 10.1523/jneurosci.3288-14.2015] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Ribosomal protein S6 (rpS6), a component of the 40S ribosomal subunit, is phosphorylated on several residues in response to numerous stimuli. Although commonly used as a marker for neuronal activity, its upstream mechanisms of regulation are poorly studied and its role in protein synthesis remains largely debated. Here, we demonstrate that the psychostimulant d-amphetamine (d-amph) markedly increases rpS6 phosphorylation at Ser235/236 sites in both crude and synaptoneurosomal preparations of the mouse striatum. This effect occurs selectively in D1R-expressing medium-sized spiny neurons (MSNs) and requires the cAMP/PKA/DARPP-32/PP-1 cascade, whereas it is independent of mTORC1/p70S6K, PKC, and ERK signaling. By developing a novel assay to label nascent peptidic chains, we show that the rpS6 phosphorylation induced in striatonigral MSNs by d-amph, as well as in striatopallidal MSNs by the antipsychotic haloperidol or in both subtypes by papaverine, is not correlated with the translation of global or 5' terminal oligopyrimidine tract mRNAs. Together, these results provide novel mechanistic insights into the in vivo regulation of the post-translational modification of rpS6 in the striatum and point out the lack of a relationship between PKA-dependent rpS6 phosphorylation and translation efficiency.
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28
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Xie J, El Sayed NM, Qi C, Zhao X, Moore CE, Herbert TP. Exendin-4 stimulates islet cell replication via the IGF1 receptor activation of mTORC1/S6K1. J Mol Endocrinol 2014; 53:105-15. [PMID: 24994913 DOI: 10.1530/jme-13-0200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Glucagon-like peptide 1 receptor (GLP1R) agonists, such as exendin-4, potentiate glucose-stimulated insulin secretion and are currently used in the management of type 2 diabetes. Interestingly, GLP1R agonists also have the ability to augment β-cell mass. In this report, we provide evidence that in the presence of glucose, exendin-4 stimulates rodent islet cell DNA replication via the activation of ribosomal protein S6 kinase 1 (S6K1) and that this is mediated by the protein kinase B (PKB)-dependent activation of mTOR complex 1 (mTORC1). We show that activation of this pathway is caused by the autocrine or paracrine activation of the IGF1 receptor (IGF1R), as siRNA-mediated knockdown of the IGF1R effectively blocked exendin-4-stimulated PKB and mTORC1 activation. In contrast, pharmacological inactivation of the epidermal growth factor receptor has no discernible effect on exendin-4-stimulated PKB or mTORC1 activation. Therefore, we conclude that GLP1R agonists stimulate β-cell proliferation via the PKB-dependent stimulation of mTORC1/S6K1 whose activation is mediated through the autocrine/paracrine activation of the IGF1R. This work provides a better understanding of the molecular basis of GLP1 agonist-induced β-cell proliferation which could potentially be exploited in the identification of novel drug targets that increase β-cell mass.
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Affiliation(s)
- Jianling Xie
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
| | - Norhan M El Sayed
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
| | - Cheng Qi
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
| | - Xuechan Zhao
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
| | - Claire E Moore
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
| | - Terence P Herbert
- Department of Cell Physiology and PharmacologyUniversity of Leicester, Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
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29
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Gangarossa G, Ceolin L, Paucard A, Lerner-Natoli M, Perroy J, Fagni L, Valjent E. Repeated stimulation of dopamine D1-like receptor and hyperactivation of mTOR signaling lead to generalized seizures, altered dentate gyrus plasticity, and memory deficits. Hippocampus 2014; 24:1466-81. [DOI: 10.1002/hipo.22327] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/02/2014] [Indexed: 01/18/2023]
Affiliation(s)
- Giuseppe Gangarossa
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier France
- INSERM, U661; Montpellier France
- Universités de Montpellier 1 & 2; UMR-5203 Montpellier France
| | - Laura Ceolin
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier France
- INSERM, U661; Montpellier France
- Universités de Montpellier 1 & 2; UMR-5203 Montpellier France
| | - Alexia Paucard
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier France
- INSERM, U661; Montpellier France
- Universités de Montpellier 1 & 2; UMR-5203 Montpellier France
| | - Mireille Lerner-Natoli
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier France
- INSERM, U661; Montpellier France
- Universités de Montpellier 1 & 2; UMR-5203 Montpellier France
| | - Julie Perroy
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier France
- INSERM, U661; Montpellier France
- Universités de Montpellier 1 & 2; UMR-5203 Montpellier France
| | - Laurent Fagni
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier France
- INSERM, U661; Montpellier France
- Universités de Montpellier 1 & 2; UMR-5203 Montpellier France
| | - Emmanuel Valjent
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle; Montpellier France
- INSERM, U661; Montpellier France
- Universités de Montpellier 1 & 2; UMR-5203 Montpellier France
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30
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de Joussineau C, Sahut-Barnola I, Tissier F, Dumontet T, Drelon C, Batisse-Lignier M, Tauveron I, Pointud JC, Lefrançois-Martinez AM, Stratakis CA, Bertherat J, Val P, Martinez A. mTOR pathway is activated by PKA in adrenocortical cells and participates in vivo to apoptosis resistance in primary pigmented nodular adrenocortical disease (PPNAD). Hum Mol Genet 2014; 23:5418-28. [PMID: 24865460 DOI: 10.1093/hmg/ddu265] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Primary pigmented nodular adrenocortical disease (PPNAD) is associated with inactivating mutations of the PRKAR1A tumor suppressor gene that encodes the regulatory subunit R1α of the cAMP-dependent protein kinase (PKA). In human and mouse adrenocortical cells, these mutations lead to increased PKA activity, which results in increased resistance to apoptosis that contributes to the tumorigenic process. We used in vitro and in vivo models to investigate the possibility of a crosstalk between PKA and mammalian target of rapamycin (mTOR) pathways in adrenocortical cells and its possible involvement in apoptosis resistance. Impact of PKA signaling on activation of the mTOR pathway and apoptosis was measured in a mouse model of PPNAD (AdKO mice), in human and mouse adrenocortical cell lines in response to pharmacological inhibitors and in PPNAD tissues by immunohistochemistry. AdKO mice showed increased mTOR complex 1 (mTORC1) pathway activity. Inhibition of mTORC1 by rapamycin restored sensitivity of adrenocortical cells to apoptosis in AdKO but not in wild-type mice. In both cell lines and mouse adrenals, rapid phosphorylation of mTORC1 targets including BAD proapoptotic protein was observed in response to PKA activation. Accordingly, BAD hyperphosphorylation, which inhibits its proapoptotic activity, was increased in both AdKO mouse adrenals and human PPNAD tissues. In conclusion, mTORC1 pathway is activated by PKA signaling in human and mouse adrenocortical cells, leading to increased cell survival, which is correlated with BAD hyperphosphorylation. These alterations could be causative of tumor formation.
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Affiliation(s)
- Cyrille de Joussineau
- Génétique Reproduction et Développement (GReD), Clermont Université, Université Blaise Pascal, Clermont-Ferrand Cedex 1 63012, France, CNRS, UMR 6293, GReD, INSERM, U1103, Aubière Cedex 63171, France, GReD, INSERM, U1103, Aubière Cedex 63171, France
| | - Isabelle Sahut-Barnola
- Génétique Reproduction et Développement (GReD), Clermont Université, Université Blaise Pascal, Clermont-Ferrand Cedex 1 63012, France, CNRS, UMR 6293, GReD, INSERM, U1103, Aubière Cedex 63171, France, GReD, INSERM, U1103, Aubière Cedex 63171, France
| | - Frédérique Tissier
- Institut Cochin, Université Paris Descartes, INSERM U1016, CNRS UMR8104, Paris 75014, France, Department of Endocrinology and Department of Pathology, Reference Center for Rare Adrenal Diseases, Assistance Publique Hôpitaux de Paris, Hôpital Cochin, Paris 75014, France, Department of Pathology, Hôpital Pitié-Salpêtrière, Université Pierre et Marie Curie, 75013 Paris, France
| | - Typhanie Dumontet
- Génétique Reproduction et Développement (GReD), Clermont Université, Université Blaise Pascal, Clermont-Ferrand Cedex 1 63012, France, CNRS, UMR 6293, GReD, INSERM, U1103, Aubière Cedex 63171, France, GReD, INSERM, U1103, Aubière Cedex 63171, France
| | - Coralie Drelon
- Génétique Reproduction et Développement (GReD), Clermont Université, Université Blaise Pascal, Clermont-Ferrand Cedex 1 63012, France, CNRS, UMR 6293, GReD, INSERM, U1103, Aubière Cedex 63171, France, GReD, INSERM, U1103, Aubière Cedex 63171, France
| | - Marie Batisse-Lignier
- Génétique Reproduction et Développement (GReD), Clermont Université, Université Blaise Pascal, Clermont-Ferrand Cedex 1 63012, France, CNRS, UMR 6293, GReD, INSERM, U1103, Aubière Cedex 63171, France, GReD, INSERM, U1103, Aubière Cedex 63171, France, Service d'Endocrinologie, Centre Hospitalier Universitaire de Clermont-Ferrand, Clermont-Ferrand 63003, France and
| | - Igor Tauveron
- Génétique Reproduction et Développement (GReD), Clermont Université, Université Blaise Pascal, Clermont-Ferrand Cedex 1 63012, France, CNRS, UMR 6293, GReD, INSERM, U1103, Aubière Cedex 63171, France, GReD, INSERM, U1103, Aubière Cedex 63171, France, Service d'Endocrinologie, Centre Hospitalier Universitaire de Clermont-Ferrand, Clermont-Ferrand 63003, France and
| | - Jean-Christophe Pointud
- Génétique Reproduction et Développement (GReD), Clermont Université, Université Blaise Pascal, Clermont-Ferrand Cedex 1 63012, France, CNRS, UMR 6293, GReD, INSERM, U1103, Aubière Cedex 63171, France, GReD, INSERM, U1103, Aubière Cedex 63171, France
| | - Anne-Marie Lefrançois-Martinez
- Génétique Reproduction et Développement (GReD), Clermont Université, Université Blaise Pascal, Clermont-Ferrand Cedex 1 63012, France, CNRS, UMR 6293, GReD, INSERM, U1103, Aubière Cedex 63171, France, GReD, INSERM, U1103, Aubière Cedex 63171, France
| | - Constantine A Stratakis
- Section on Endocrinology and Genetics, PDEGEN, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jérôme Bertherat
- Institut Cochin, Université Paris Descartes, INSERM U1016, CNRS UMR8104, Paris 75014, France, Department of Endocrinology and Department of Pathology, Reference Center for Rare Adrenal Diseases, Assistance Publique Hôpitaux de Paris, Hôpital Cochin, Paris 75014, France
| | - Pierre Val
- Génétique Reproduction et Développement (GReD), Clermont Université, Université Blaise Pascal, Clermont-Ferrand Cedex 1 63012, France, CNRS, UMR 6293, GReD, INSERM, U1103, Aubière Cedex 63171, France, GReD, INSERM, U1103, Aubière Cedex 63171, France
| | - Antoine Martinez
- Génétique Reproduction et Développement (GReD), Clermont Université, Université Blaise Pascal, Clermont-Ferrand Cedex 1 63012, France, CNRS, UMR 6293, GReD, INSERM, U1103, Aubière Cedex 63171, France, GReD, INSERM, U1103, Aubière Cedex 63171, France,
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Okunishi K, DeGraaf AJ, Zasłona Z, Peters-Golden M. Inhibition of protein translation as a novel mechanism for prostaglandin E2 regulation of cell functions. FASEB J 2013; 28:56-66. [PMID: 24072780 DOI: 10.1096/fj.13-231720] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Prostaglandin E2 (PGE2) regulates numerous biological processes by modulating transcriptional activation, epigenetic control, proteolysis, and secretion of various proteins. Scar formation depends on fibroblast elaboration of matrix proteins such as collagen, and this process is strongly suppressed by PGE2 through activation of cAMP-dependent protein kinase A (PKA). However, the actual mechanism by which PGE2-PKA signaling inhibits collagen expression in fibroblasts has never been delineated, and that was the objective of this study. PGE2 unexpectedly induced a rapid reduction in procollagen I protein expression in adult lung fibroblasts, with a half-maximum effect at 1.5 h. This effect reflected its inhibition of translation rather than transcription. Global protein synthesis was also inhibited by PGE2. This action was mediated by PKA and involved both activation of ribosomal protein (rpS6) and suppression of mammalian target of rapamycin (mTOR). Similar effects of PGE2 were demonstrated in mouse peritoneal macrophages (PMs). These findings identify inhibition of translation as a new mechanism by which PGE2 regulates cellular function and a novel example of translational inhibition mediated by opposing actions on two distinct translational control pathways. Translational inhibition would be expected to contribute to dynamic alterations in cell function that accompany the changing PGE2 levels observed in disease states and with various pharmacotherapies.
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Zhang Z, Liu R, Townsend PA, Proud CG. p90RSKs mediate the activation of ribosomal RNA synthesis by the hypertrophic agonist phenylephrine in adult cardiomyocytes. J Mol Cell Cardiol 2013; 59:139-47. [DOI: 10.1016/j.yjmcc.2013.03.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Revised: 03/05/2013] [Accepted: 03/07/2013] [Indexed: 01/06/2023]
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Macias M, Blazejczyk M, Kazmierska P, Caban B, Skalecka A, Tarkowski B, Rodo A, Konopacki J, Jaworski J. Spatiotemporal characterization of mTOR kinase activity following kainic acid induced status epilepticus and analysis of rat brain response to chronic rapamycin treatment. PLoS One 2013; 8:e64455. [PMID: 23724051 PMCID: PMC3665782 DOI: 10.1371/journal.pone.0064455] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 04/15/2013] [Indexed: 01/09/2023] Open
Abstract
Mammalian target of rapamycin (mTOR) is a protein kinase that senses nutrient availability, trophic factors support, cellular energy level, cellular stress, and neurotransmitters and adjusts cellular metabolism accordingly. Adequate mTOR activity is needed for development as well as proper physiology of mature neurons. Consequently, changes in mTOR activity are often observed in neuropathology. Recently, several groups reported that seizures increase mammalian target of rapamycin (mTOR) kinase activity, and such increased activity in genetic models can contribute to spontaneous seizures. However, the current knowledge about the spatiotemporal pattern of mTOR activation induced by proconvulsive agents is rather rudimentary. Also consequences of insufficient mTOR activity on a status epilepticus are poorly understood. Here, we systematically investigated these two issues. We showed that mTOR signaling was activated by kainic acid (KA)-induced status epilepticus through several brain areas, including the hippocampus and cortex as well as revealed two waves of mTOR activation: an early wave (2 h) that occurs in neurons and a late wave that predominantly occurs in astrocytes. Unexpectedly, we found that pretreatment with rapamycin, a potent mTOR inhibitor, gradually (i) sensitized animals to KA treatment and (ii) induced gross anatomical changes in the brain.
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Affiliation(s)
- Matylda Macias
- Laboratory of Molecular and Cell Neurobiology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Magdalena Blazejczyk
- Laboratory of Molecular and Cell Neurobiology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | | | - Bartosz Caban
- Department of Neurobiology, University of Lodz, Lodz, Poland
| | - Agnieszka Skalecka
- Laboratory of Molecular and Cell Neurobiology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Bartosz Tarkowski
- Laboratory of Molecular and Cell Neurobiology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Anna Rodo
- Department of Pathology and Veterinary Diagnostics, Warsaw University of Life Sciences-SGGW, Warsaw, Poland
| | - Jan Konopacki
- Department of Neurobiology, University of Lodz, Lodz, Poland
| | - Jacek Jaworski
- Laboratory of Molecular and Cell Neurobiology, International Institute of Molecular and Cell Biology, Warsaw, Poland
- * E-mail:
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Salles MJ, Hervé D, Rivet JM, Longueville S, Millan MJ, Girault JA, Cour CML. Transient and rapid activation of Akt/GSK-3β and mTORC1 signaling by D3 dopamine receptor stimulation in dorsal striatum and nucleus accumbens. J Neurochem 2013; 125:532-44. [DOI: 10.1111/jnc.12206] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 01/26/2013] [Accepted: 02/06/2013] [Indexed: 01/08/2023]
Affiliation(s)
- Marie-Josèphe Salles
- Institut National de la Santé et de la Recherche Médicale (Inserm); Paris France
- Université Pierre et Marie Curie-Paris 6; Paris France
- Institut du Fer à Moulin; Paris France
- Psychopharmacology Department; Institut de Recherches Servier; Croissy sur Seine France
| | - Denis Hervé
- Institut National de la Santé et de la Recherche Médicale (Inserm); Paris France
- Université Pierre et Marie Curie-Paris 6; Paris France
- Institut du Fer à Moulin; Paris France
| | - Jean-Michel Rivet
- Psychopharmacology Department; Institut de Recherches Servier; Croissy sur Seine France
| | - Sophie Longueville
- Institut National de la Santé et de la Recherche Médicale (Inserm); Paris France
- Université Pierre et Marie Curie-Paris 6; Paris France
- Institut du Fer à Moulin; Paris France
| | - Mark J. Millan
- Psychopharmacology Department; Institut de Recherches Servier; Croissy sur Seine France
| | - Jean-Antoine Girault
- Institut National de la Santé et de la Recherche Médicale (Inserm); Paris France
- Université Pierre et Marie Curie-Paris 6; Paris France
- Institut du Fer à Moulin; Paris France
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Feliciano DM, Lin TV, Hartman NW, Bartley CM, Kubera C, Hsieh L, Lafourcade C, O'Keefe RA, Bordey A. A circuitry and biochemical basis for tuberous sclerosis symptoms: from epilepsy to neurocognitive deficits. Int J Dev Neurosci 2013; 31:667-78. [PMID: 23485365 DOI: 10.1016/j.ijdevneu.2013.02.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 02/15/2013] [Accepted: 02/18/2013] [Indexed: 01/17/2023] Open
Abstract
Tuberous sclerosis complex (TSC) is an autosomal dominant monogenetic disorder that is characterized by the formation of benign tumors in several organs as well as brain malformations and neuronal defects. TSC is caused by inactivating mutations in one of two genes, TSC1 and TSC2, resulting in increased activity of the mammalian Target of Rapamycin (mTOR). Here, we explore the cytoarchitectural and functional CNS aberrations that may account for the neurological presentations of TSC, notably seizures, hydrocephalus, and cognitive and psychological impairments. In particular, recent mouse models of brain lesions are presented with an emphasis on using electroporation to allow the generation of discrete lesions resulting from loss of heterozygosity during perinatal development. Cortical lesions are thought to contribute to epileptogenesis and worsening of cognitive defects. However, it has recently been suggested that being born with a mutant allele without loss of heterozygosity and associated cortical lesions is sufficient to generate cognitive and neuropsychiatric problems. We will thus discuss the function of mTOR hyperactivity on neuronal circuit formation and the potential consequences of being born heterozygous on neuronal function and the biochemistry of synaptic plasticity, the cellular substrate of learning and memory. Ultimately, a major goal of TSC research is to identify the cellular and molecular mechanisms downstream of mTOR underlying the neurological manifestations observed in TSC patients and identify novel therapeutic targets to prevent the formation of brain lesions and restore neuronal function.
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Affiliation(s)
- David M Feliciano
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT, USA; Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
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Miao XY, Gu ZY, Liu P, Hu Y, Li L, Gong YP, Shu H, Liu Y, Li CL. The human glucagon-like peptide-1 analogue liraglutide regulates pancreatic beta-cell proliferation and apoptosis via an AMPK/mTOR/P70S6K signaling pathway. Peptides 2013; 39:71-9. [PMID: 23116613 DOI: 10.1016/j.peptides.2012.10.006] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2012] [Revised: 10/15/2012] [Accepted: 10/22/2012] [Indexed: 02/07/2023]
Abstract
Glucagon-like peptide-1 (GLP-1), an effective therapeutic agent for the treatment of diabetes, has been proven to protect pancreatic beta cells through many pathways. Recent evidence demonstrates that AMP-activated protein kinase (AMPK), as a metabolic regulator, coordinates beta-cell protein synthesis through regulation of the mammalian target of rapamycin (mTOR) signaling pathway. The purpose of the present study was to explore whether liraglutide, a human GLP-1 analogue, protects beta cells via AMPK/mTOR signaling. We evaluated INS-1 beta-cell line proliferation using the Cell Counting Kit-8, and examined the effect of GLP-1 on cellular ATP levels using an ATP assay kit. mTOR pathway protein expression levels were tested by Western blotting and glucolipotoxicity-induced cell apoptosis was evaluated by flow cytometry. Liraglutide increased beta-cell viability at an optimum concentration of 100 nmol/L in the presence of 11.1 or 30 mmol/L glucose. Liraglutide (100 nmol/L) activated mTOR and its downstream effectors, 70-kDa ribosomal protein S6 kinase and eIF4E-binding protein-1, in INS-1 cells. This effect was abated by pathway blockers: the AMPK activator AICAR and the mTOR inhibitor rapamycin. Furthermore, the effect of liraglutide on beta-cell proliferation was inhibited by AICAR and rapamycin. Liraglutide increased cellular ATP levels. In addition, liraglutide protected beta cells from glucolipotoxicity-induced apoptosis. This response was also prevented by rapamycin treatment. These results suggest that the enhancement of beta-cell proliferation by that GLP-1 receptor agonist liraglutide is mediated, at least in part, by AMPK/mTOR signaling. Liraglutide also prevents beta-cell glucolipotoxicity by activating mTOR.
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Affiliation(s)
- Xin-Yu Miao
- Department of Geriatric Endocrinology, General Hospital of PLA, 100853 Beijing, China
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37
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The role of mTORC1 in regulating protein synthesis and skeletal muscle mass in response to various mechanical stimuli. Rev Physiol Biochem Pharmacol 2013; 166:43-95. [PMID: 24442322 DOI: 10.1007/112_2013_17] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Skeletal muscle plays a fundamental role in mobility, disease prevention, and quality of life. Skeletal muscle mass is, in part, determined by the rates of protein synthesis, and mechanical loading is a major regulator of protein synthesis and skeletal muscle mass. The mammalian/mechanistic target of rapamycin (mTOR), found in the multi-protein complex, mTORC1, is proposed to play an essential role in the regulation of protein synthesis and skeletal muscle mass. The purpose of this review is to examine the function of mTORC1 in relation to protein synthesis and cell growth, the current evidence from rodent and human studies for the activation of mTORC1 signaling by different types of mechanical stimuli, whether mTORC1 signaling is necessary for changes in protein synthesis and skeletal muscle mass that occur in response to different types of mechanical stimuli, and the proposed molecular signaling mechanisms that may be responsible for the mechanical activation of mTORC1 signaling.
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Bertran-Gonzalez J, Chieng BC, Laurent V, Valjent E, Balleine BW. Striatal cholinergic interneurons display activity-related phosphorylation of ribosomal protein S6. PLoS One 2012; 7:e53195. [PMID: 23285266 PMCID: PMC3532298 DOI: 10.1371/journal.pone.0053195] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Accepted: 11/27/2012] [Indexed: 01/10/2023] Open
Abstract
Cholinergic interneurons (CINs) provide the main source of acetylcholine to all striatal regions, and strongly modulate dopaminergic actions through complex regulation of pre- and post-synaptic acetylcholine receptors. Although striatal CINs have a well-defined electrophysiological profile, their biochemical properties are poorly understood, likely due to their low proportion within the striatum (2-3%). We report a strong and sustained phosphorylation of ribosomal protein S6 on its serine 240 and 244 residues (p-Ser²⁴⁰⁻²⁴⁴-S6rp), a protein integrant of the ribosomal machinery related to the mammalian target of the rapamycin complex 1 (mTORC1) pathway, which we found to be principally expressed in striatal CINs in basal conditions. We explored the functional relevance of this cellular event by pharmacologically inducing various sustained physiological activity states in CINs and assessing the effect on the levels of S6rp phosphorylation. Cell-attached electrophysiological recordings from CINs in a striatal slice preparation showed an inhibitory effect of tetrodotoxin (TTX) on action potential firing paralleled by a decrease in the p-Ser²⁴⁰⁻²⁴⁴-S6rp signal as detected by immunofluorescence after prolonged incubation. On the other hand, elevation in extracellular potassium concentration and the addition of apamin generated an increased firing rate and a burst-firing activity in CINs, respectively, and both stimulatory conditions significantly increased Ser²⁴⁰⁻²⁴⁴-S6rp phosphorylation above basal levels when incubated for one hour. Apamin generated a particularly large increase in phosphorylation that was sensitive to rapamycin. Taken together, our results demonstrate for the first time a link between the state of neuronal activity and a biochemical signaling event in striatal CINs, and suggest that immunofluorescence can be used to estimate the cellular activity of CINs under different pharmacological and/or behavioral conditions.
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Affiliation(s)
- Jesus Bertran-Gonzalez
- Behavioural Neuroscience Laboratory, Brain and Mind Research Institute, The University of Sydney, New South Wales, Australia
| | - Billy C. Chieng
- Behavioural Neuroscience Laboratory, Brain and Mind Research Institute, The University of Sydney, New South Wales, Australia
| | - Vincent Laurent
- Behavioural Neuroscience Laboratory, Brain and Mind Research Institute, The University of Sydney, New South Wales, Australia
| | - Emmanuel Valjent
- Institut de Génomique Fonctionnelle, Inserm U661, CNRS UMR 5203, Montpellier, France
| | - Bernard W. Balleine
- Behavioural Neuroscience Laboratory, Brain and Mind Research Institute, The University of Sydney, New South Wales, Australia
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Selway JL, Moore CE, Mistry R, John Challiss RA, Herbert TP. Molecular mechanisms of muscarinic acetylcholine receptor-stimulated increase in cytosolic free Ca(2+) concentration and ERK1/2 activation in the MIN6 pancreatic β-cell line. Acta Diabetol 2012; 49:277-89. [PMID: 21833779 PMCID: PMC3407357 DOI: 10.1007/s00592-011-0314-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 07/17/2011] [Indexed: 11/29/2022]
Abstract
Muscarinic acetylcholine receptor (mAChR) activation of pancreatic β-cells elevates intracellular Ca(2+) and potentiates glucose-stimulated insulin secretion. In addition, it activates a number of signaling molecules, including ERK1/2, whose activation has been shown to play an important role in regulating pancreatic β-cell function and mass. The aim of this work was to determine how mAChR activation elevates intracellular Ca(2+) concentration ([Ca(2+)]( i )) and activates ERK1/2 in the pancreatic β-cell line MIN6. We demonstrate that agonist-stimulated ERK1/2 activation is dependent on the activation of phospholipase C and an elevation in [Ca(2+)]( i ), but is independent of the activation of diacylglycerol-dependent protein kinase C isoenzymes. Using a pharmacological approach, we provide evidence that agonist-induced increases in [Ca(2+)]( i ) and ERK activity require (1) IP(3) receptor-mediated mobilization of Ca(2+) from the endoplasmic reticulum, (2) influx of extracellular Ca(2+) through store-operated channels, (3) closure of K(ATP) channels, and (4) Ca(2+) entry via L-type voltage-operated Ca(2+) channels. Moreover, this Ca(2+)-dependent activation of ERK is mediated via both Ras-dependent and Ras-independent mechanisms. In summary, this study provides important insights into the multifactorial signaling mechanisms linking mAChR activation to increases in [Ca(2+)]( i ) and ERK activity.
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Affiliation(s)
- Joanne L. Selway
- Department of Cell Physiology and Pharmacology, University of Leicester, Henry Wellcome Building, Leicester, LE1 9HN UK
| | - Claire E. Moore
- Department of Cell Physiology and Pharmacology, University of Leicester, Henry Wellcome Building, Leicester, LE1 9HN UK
| | - Rajendra Mistry
- Department of Cell Physiology and Pharmacology, University of Leicester, Henry Wellcome Building, Leicester, LE1 9HN UK
| | - R. A. John Challiss
- Department of Cell Physiology and Pharmacology, University of Leicester, Henry Wellcome Building, Leicester, LE1 9HN UK
| | - Terence P. Herbert
- Department of Cell Physiology and Pharmacology, University of Leicester, Henry Wellcome Building, Leicester, LE1 9HN UK
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Gangarossa G, Valjent E. Regulation of the ERK pathway in the dentate gyrus by in vivo dopamine D1 receptor stimulation requires glutamatergic transmission. Neuropharmacology 2012; 63:1107-17. [PMID: 22796106 DOI: 10.1016/j.neuropharm.2012.06.062] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2012] [Revised: 06/22/2012] [Accepted: 06/29/2012] [Indexed: 11/18/2022]
Abstract
Acute systemic administration of the dopamine D1/D5 receptors (D1Rs) agonist, SKF81297, activates the extracellular signal-regulated protein kinases (ERK) pathway selectively in the granule cells of the dentate gyrus. In this study, we examined the mechanisms involved in this regulation and investigated the molecular components that could promote ERK-dependent transcription and translation. SKF81297 induced phosphorylation of ERK and histone H3 required intact glutamatergic transmission. Blockade of glutamate release achieved by the mGluR2/3 agonist, LY354740 or the selective adenosine A1R agonist, CCPA as well as neurotoxic lesions of lateral entorhinal cortex reduced the ability of SKF81297 to induce ERK activation in the dentate gyrus. This activation required the combined stimulation of NR2B-containing NMDARs, mGluR1 and mGluR5. SKF81297 evoked phosphorylation of the ribosomal protein S6 (rpS6) selectively at the Ser235/236 site while the Ser240/244 site remains unchanged. The SKF81297 induced increased phosphorylation of rpS6 was dependent on PKC and ERK/p90RSK activation. Surprisingly, administration of D1Rs agonist suppressed mTORC1/p70S6K pathway suggesting an mTOR-independent regulation of rpS6 phosphorylation. Taken together, our results show that intact glutamatergic transmission plays a major role in the regulation of ERK-dependent phosphorylation of histone H3 and rpS6 observed in the mouse dentate gyrus after systemic administration of SKF81297.
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Barlow AD, Xie J, Moore CE, Campbell SC, Shaw JAM, Nicholson ML, Herbert TP. Rapamycin toxicity in MIN6 cells and rat and human islets is mediated by the inhibition of mTOR complex 2 (mTORC2). Diabetologia 2012; 55:1355-65. [PMID: 22314813 PMCID: PMC3328678 DOI: 10.1007/s00125-012-2475-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 01/09/2012] [Indexed: 11/05/2022]
Abstract
AIMS/HYPOTHESIS Rapamycin (sirolimus) is one of the primary immunosuppressants for islet transplantation. Yet there is evidence that the long-term treatment of islet-transplant patients with rapamycin may be responsible for subsequent loss of islet graft function and viability. Therefore, the primary objective of this study was to elucidate the molecular mechanism of rapamycin toxicity in beta cells. METHODS Experiments were performed on isolated rat and human islets of Langerhans and MIN6 cells. The effects of rapamycin and the roles of mammalian target of rapamycin complex 2 (mTORC2)/protein kinase B (PKB) on beta cell signalling, function and viability were investigated using cell viability assays, insulin ELISA assays, kinase assays, western blotting, pharmacological inhibitors, small interfering (si)RNA and through the overproduction of a constitutively active mutant of PKB. RESULTS Rapamycin treatment of MIN6 cells and islets of Langerhans resulted in a loss of cell function and viability. Although rapamycin acutely inhibited mTOR complex 1 (mTORC1), the toxic effects of rapamycin were more closely correlated to the dissociation and inactivation of mTORC2 and the inhibition of PKB. Indeed, the overproduction of constitutively active PKB protected islets from rapamycin toxicity whereas the inhibition of PKB led to a loss of cell viability. Moreover, the selective inactivation of mTORC2 using siRNA directed towards rapamycin-insensitive companion of target of rapamycin (RICTOR), mimicked the toxic effects of chronic rapamycin treatment. CONCLUSIONS/INTERPRETATION This report provides evidence that rapamycin toxicity is mediated by the inactivation of mTORC2 and the inhibition of PKB and thus reveals the molecular basis of rapamycin toxicity and the essential role of mTORC2 in maintaining beta cell function and survival.
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Affiliation(s)
- A. D. Barlow
- Transplant Surgery Group, Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK
| | - J. Xie
- Department of Cell Physiology and Pharmacology, University of Leicester, The Henry Wellcome Building, University Road, Leicester, LE1 9HN UK
| | - C. E. Moore
- Department of Cell Physiology and Pharmacology, University of Leicester, The Henry Wellcome Building, University Road, Leicester, LE1 9HN UK
| | - S. C. Campbell
- Institute of Cellular Medicine, Newcastle University, Newcastle, UK
| | - J. A. M. Shaw
- Institute of Cellular Medicine, Newcastle University, Newcastle, UK
| | - M. L. Nicholson
- Transplant Surgery Group, Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK
| | - T. P. Herbert
- Department of Cell Physiology and Pharmacology, University of Leicester, The Henry Wellcome Building, University Road, Leicester, LE1 9HN UK
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Xie J, Herbert TP. The role of mammalian target of rapamycin (mTOR) in the regulation of pancreatic β-cell mass: implications in the development of type-2 diabetes. Cell Mol Life Sci 2012; 69:1289-304. [PMID: 22068611 PMCID: PMC11114779 DOI: 10.1007/s00018-011-0874-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Revised: 10/20/2011] [Accepted: 10/20/2011] [Indexed: 12/22/2022]
Abstract
Type-2 diabetes mellitus (T2DM) is a disorder that is characterized by high blood glucose concentration in the context of insulin resistance and/or relative insulin deficiency. It causes metabolic changes that lead to the damage and functional impairment of organs and tissues resulting in increased morbidity and mortality. It is this form of diabetes whose prevalence is increasing at an alarming rate due to the 'obesity epidemic', as obesity is a key risk factor in the development of insulin resistance. However, the majority of individuals who have insulin resistance do not develop diabetes due to a compensatory increase in insulin secretion in response to an increase in insulin demand. This adaptive response is sustained by an increase in both β-cell function and mass. Importantly, there is increasing evidence that the Serine/Threonine kinase mammalian target of rapamycin (mTOR) plays a key role in the regulation of β-cell mass and therefore likely plays a critical role in β-cell adaptation. Therefore, the primary focus of this review is to summarize our current understanding of the role of mTOR in stimulating pancreatic β-cell mass and thus, in the prevention of type-2 diabetes.
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Affiliation(s)
- Jianling Xie
- Department of Cell Physiology and Pharmacology, University of Leicester, The Henry Wellcome Building, University Road, Leicester, LE1 9HN UK
| | - Terence P. Herbert
- Department of Cell Physiology and Pharmacology, University of Leicester, The Henry Wellcome Building, University Road, Leicester, LE1 9HN UK
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Haloperidol regulates the state of phosphorylation of ribosomal protein S6 via activation of PKA and phosphorylation of DARPP-32. Neuropsychopharmacology 2011; 36:2561-70. [PMID: 21814187 PMCID: PMC3194082 DOI: 10.1038/npp.2011.144] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Administration of typical antipsychotic drugs, such as haloperidol, promotes cAMP-dependent signaling in the medium spiny neurons (MSNs) of the striatum. In this study, we have examined the effect of haloperidol on the state of phosphorylation of the ribosomal protein S6 (rpS6), a component of the small 40S ribosomal subunit. We found that haloperidol increases the phosphorylation of rpS6 at the dual site Ser235/236, which is involved in the regulation of mRNA translation. This effect was exerted in the MSNs of the indirect pathway, which express specifically dopamine D2 receptors (D2Rs) and adenosine A2 receptors (A2ARs). The effect of haloperidol was decreased by blockade of A2ARs or by genetic attenuation of the Gα(olf) protein, which couples A2ARs to activation of adenylyl cyclase. Moreover, stimulation of cAMP-dependent protein kinase A (PKA) increased Ser235/236 phosphorylation in cultured striatal neurons. The ability of haloperidol to promote rpS6 phosphorylation was abolished in knock-in mice deficient for PKA activation of the protein phosphatase-1 inhibitor, dopamine- and cAMP-regulated phosphoprotein of 32 kDa. In contrast, pharmacological or genetic inactivation of p70 rpS6 kinase 1, or extracellular signal-regulated kinases did not affect haloperidol-induced rpS6 phosphorylation. These results identify PKA as a major rpS6 kinase in neuronal cells and suggest that regulation of protein synthesis through rpS6 may be a potential target of antipsychotic drugs.
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Xie J, Ponuwei GA, Moore CE, Willars GB, Tee AR, Herbert TP. cAMP inhibits mammalian target of rapamycin complex-1 and -2 (mTORC1 and 2) by promoting complex dissociation and inhibiting mTOR kinase activity. Cell Signal 2011; 23:1927-35. [PMID: 21763421 PMCID: PMC3189512 DOI: 10.1016/j.cellsig.2011.06.025] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 06/27/2011] [Indexed: 12/13/2022]
Abstract
cAMP and mTOR signalling pathways control a number of critical cellular processes including metabolism, protein synthesis, proliferation and cell survival and therefore understanding the signalling events which integrate these two signalling pathways is of particular interest. In this study, we show that the pharmacological elevation of [cAMP](i) in mouse embryonic fibroblasts (MEFs) and human embryonic kidney 293 (HEK293) cells inhibits mTORC1 activation via a PKA-dependent mechanism. Although the inhibitory effect of cAMP on mTOR could be mediated by impinging on signalling cascades (i.e. PKB, MAPK and AMPK) that inhibit TSC1/2, an upstream negative regulator of mTORC1, we show that cAMP inhibits mTORC1 in TSC2 knockout (TSC2(-/-)) MEFs. We also show that cAMP inhibits insulin and amino acid-stimulated mTORC1 activation independently of Rheb, Rag GTPases, TSC2, PKB, MAPK and AMPK, indicating that cAMP may act independently of known regulatory inputs into mTOR. Moreover, we show that the prolonged elevation in [cAMP](i) can also inhibit mTORC2. We provide evidence that this cAMP-dependent inhibition of mTORC1/2 is caused by the dissociation of mTORC1 and 2 and a reduction in mTOR catalytic activity, as determined by its auto-phosphorylation on Ser2481. Taken together, these results provide an important insight into how cAMP signals to mTOR and down-regulates its activity, which may lead to the identification of novel drug targets to inhibit mTOR that could be used for the treatment and prevention of human diseases such as cancer.
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Affiliation(s)
- Jianling Xie
- Department of Cell Physiology and Pharmacology, University of Leicester, The Henry Wellcome Building, University Road, Leicester LE1 9HN, UK
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Meyuhas O, Dreazen A. Ribosomal protein S6 kinase from TOP mRNAs to cell size. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 90:109-53. [PMID: 20374740 DOI: 10.1016/s1877-1173(09)90003-5] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Ribosomal protein S6 kinase (S6K) has been implicated in the phosphorylation of multiple substrates and is subject to activation by a wide variety of signals that converge at mammalian target of rapamycin (mTOR). In the course of the search for its physiological role, it was proposed that S6K activation and ribosomal protein S6 (rpS6) phosphorylation account for the translational activation of a subgroup of transcripts, the TOP mRNAs. The structural hallmark of these mRNAs is an oligopyrimidine tract at their 5'-terminus, known as the 5'-TOP motif. TOP mRNAs consists of about 90 members that encode multiple components of the translational machinery, such as ribosomal proteins and translation factors. The translation efficiency of TOP mRNAs indeed correlates with S6K activation and rpS6 phosphorylation, yet recent biochemical and genetic studies have established that, although S6K and TOP mRNAs respond to similar signals and are regulated by mTOR, they maintain no cause and effect relationship. Instead, S6K is primarily involved in regulation of cell size, and affects glucose homeostasis, but is dispensable for global protein synthesis, whereas translational efficiency of TOP mRNAs is a determinant of the cellular protein synthesis capacity. Despite extensive studies of their function and mode of regulation, the mechanism underlying the effect of S6K on the cell size, as well as the trans-acting factor that mediates the translational control of TOP mRNAs, still await their identification.
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Affiliation(s)
- Oded Meyuhas
- Department of Biochemistry and Molecular Biology, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
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