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Salerno-Goncalves R, Chen H, Bafford AC, Izquierdo M, Hormazábal JC, Lagos R, Tettelin H, D'Mello A, Booth JS, Fasano A, Levine MM, Sztein MB. Early host immune responses in a human organoid-derived gallbladder monolayer to Salmonella Typhi strains from patients with acute and chronic infections: a comparative analysis. Front Immunol 2024; 15:1334762. [PMID: 38533492 PMCID: PMC10963533 DOI: 10.3389/fimmu.2024.1334762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 02/26/2024] [Indexed: 03/28/2024] Open
Abstract
Salmonella enterica serovar Typhi (S. Typhi), a human-restricted pathogen, invades the host through the gut to cause typhoid fever. Recent calculations of the typhoid fever burden estimated that more than 10 million new typhoid fever cases occur in low and middle-income countries, resulting in 65,400-187,700 deaths yearly. Interestingly, if not antibiotic-treated, upon the resolution of acute disease, 1%-5% of patients become asymptomatic chronic carriers. Chronically infected hosts are not only critical reservoirs of infection that transmit the disease to naive individuals but are also predisposed to developing gallbladder carcinoma. Nevertheless, the molecular mechanisms involved in the early interactions between gallbladder epithelial cells and S. Typhi remain largely unknown. Based on our previous studies showing that closely related S. Typhi strains elicit distinct innate immune responses, we hypothesized that host molecular pathways activated by S. Typhi strains derived from acutely and chronically infected patients would differ. To test this hypothesis, we used a novel human organoid-derived polarized gallbladder monolayer model, and S. Typhi strains derived from acutely and chronically infected patients. We found that S. Typhi strains derived from acutely and chronically infected patients differentially regulate host mitogen-activated protein kinase (MAPK) and S6 transcription factors. These variations might be attributed to differential cytokine signaling, predominantly via TNF-α and IL-6 production and appear to be influenced by the duration the isolate was subjected to selective pressures in the gallbladder. These findings represent a significant leap in understanding the complexities behind chronic S. Typhi infections in the gallbladder and may uncover potential intervention targets.
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Affiliation(s)
- Rosângela Salerno-Goncalves
- Center for Vaccine Development and Global Health and Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Haiyan Chen
- Center for Vaccine Development and Global Health and Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Andrea C Bafford
- Division of General and Oncologic Surgery, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Mariana Izquierdo
- Center for Vaccine Development and Global Health and Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Juan Carlos Hormazábal
- Seccion Bacteriologia, Subdepartamento de Enfermedades Infecciosas, Departamento de Laboratorio Biomédico, Instituto de Salud Pública de Chile (ISP), Santiago, Chile
| | - Rosanna Lagos
- Seccion Bacteriologia, Subdepartamento de Enfermedades Infecciosas, Departamento de Laboratorio Biomédico, Instituto de Salud Pública de Chile (ISP), Santiago, Chile
| | - Hervé Tettelin
- Department of Microbiology and Immunology and Institute for Genome Sciences (IGS), University of Maryland School of Medicine, Baltimore, MD, United States
| | - Adonis D'Mello
- Department of Microbiology and Immunology and Institute for Genome Sciences (IGS), University of Maryland School of Medicine, Baltimore, MD, United States
| | - Jayaum S Booth
- Center for Vaccine Development and Global Health and Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Alessio Fasano
- Mucosal Immunology and Biology Research Center, Massachusetts General Hospital for Children, Boston, MA, United States
| | - Myron M Levine
- Center for Vaccine Development and Global Health and Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Marcelo B Sztein
- Center for Vaccine Development and Global Health and Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, United States
- Program in Oncology, University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center, Baltimore, MD, United States
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2
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Joechle K, Jumaa H, Thriene K, Hellerbrand C, Kulemann B, Fichtner-Feigl S, Lang SA, Guenzle J. Dual Inhibition of mTORC1/2 Reduces Migration of Cholangiocarcinoma Cells by Regulation of Matrixmetalloproteinases. Front Cell Dev Biol 2022; 9:785979. [PMID: 35096817 PMCID: PMC8793831 DOI: 10.3389/fcell.2021.785979] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 12/17/2021] [Indexed: 12/30/2022] Open
Abstract
Cholangiocarcinoma (CCA) is a rare but highly aggressive tumor entity for which systemic therapies only showed limited efficacy so far. As OSI-027—a dual kinase inhibitor targeting both mTOR complexes, mTORC1 and mTORC2 - showed improved anti-cancer effects, we sought to evaluate its impact on the migratory and metastatic capacity of CCA cells in vitro. We found that treatment with OSI-027 leads to reduced cell mobility and migration as well as a reduced surviving fraction in colony-forming ability. While neither cell viability nor proliferation rate was affected, OSI-027 decreased the expression of MMP2 and MMP9. Moreover, survival as well as anti-apoptotic signaling was impaired upon the use of OSI-027 as determined by AKT and MAPK blotting. Dual targeting of mTORC1/2 might therefore be a viable option for anti-neoplastic therapy in CCA.
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Affiliation(s)
- Katharina Joechle
- Department of Surgery and Transplantation, University Hospital RWTH Aachen, Aachen, Germany.,Department of General and Visceral Surgery, Medical Center-University of Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Huda Jumaa
- Department of General and Visceral Surgery, Medical Center-University of Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Kerstin Thriene
- Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Claus Hellerbrand
- Institute of Biochemistry, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Birte Kulemann
- Department of Surgery, University Medical Center Schleswig-Holstein Campus Lübeck, Lübeck, Germany
| | - Stefan Fichtner-Feigl
- Department of General and Visceral Surgery, Medical Center-University of Freiburg, Faculty of Medicine, Freiburg, Germany.,Comprehensive Cancer Center Freiburg-CCCF, Medical Center-University, Freiburg, Germany
| | - Sven A Lang
- Department of Surgery and Transplantation, University Hospital RWTH Aachen, Aachen, Germany.,Department of General and Visceral Surgery, Medical Center-University of Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Jessica Guenzle
- Department of General and Visceral Surgery, Medical Center-University of Freiburg, Faculty of Medicine, Freiburg, Germany
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3
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Morris G, Walder K, Carvalho AF, Tye SJ, Lucas K, Berk M, Maes M. The role of hypernitrosylation in the pathogenesis and pathophysiology of neuroprogressive diseases. Neurosci Biobehav Rev 2017; 84:453-469. [PMID: 28789902 DOI: 10.1016/j.neubiorev.2017.07.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 07/02/2017] [Accepted: 07/31/2017] [Indexed: 12/12/2022]
Abstract
There is a wealth of data indicating that de novo protein S-nitrosylation in general and protein transnitrosylation in particular mediates the bulk of nitric oxide signalling. These processes enable redox sensing and facilitate homeostatic regulation of redox dependent protein signalling, function, stability and trafficking. Increased S-nitrosylation in an environment of increasing oxidative and nitrosative stress (O&NS) is initially a protective mechanism aimed at maintaining protein structure and function. When O&NS becomes severe, mechanisms governing denitrosylation and transnitrosylation break down leading to the pathological state referred to as hypernitrosylation (HN). Such a state has been implicated in the pathogenesis and pathophysiology of several neuropsychiatric and neurodegenerative diseases and we investigate its potential role in the development and maintenance of neuroprogressive disorders. In this paper, we propose a model whereby the hypernitrosylation of a range of functional proteins and enzymes lead to changes in activity which conspire to produce at least some of the core abnormalities contributing to the development and maintenance of pathology in these illnesses.
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Affiliation(s)
- Gerwyn Morris
- Tir Na Nog, Bryn Road seaside 87, Llanelli, SA152LW, Wales, United Kingdom
| | - Ken Walder
- Deakin University, The Centre for Molecular and Medical Research, School of Medicine, P.O. Box 291, Geelong, 3220, Australia
| | - André F Carvalho
- Department of Clinical Medicine and Translational Psychiatry Research Group, Faculty of Medicine, Federal University of Ceará, 60430-040, Fortaleza, CE, Brazil
| | - Susannah J Tye
- Deakin University, The Centre for Molecular and Medical Research, School of Medicine, P.O. Box 291, Geelong, 3220, Australia; Department of Clinical Medicine and Translational Psychiatry Research Group, Faculty of Medicine, Federal University of Ceará, 60430-040, Fortaleza, CE, Brazil; Deakin University, IMPACT Strategic Research Centre, School of Medicine, P.O. Box 281, Geelong, 3220, Australia; Orygen Youth Health Research Centre and the Centre of Youth Mental Health, The Florey Institute for Neuroscience and Mental Health and the Department of Psychiatry, University of Melbourne, Parkville, 3052, Australia
| | - Kurt Lucas
- Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
| | - Michael Berk
- Deakin University, IMPACT Strategic Research Centre, School of Medicine, P.O. Box 281, Geelong, 3220, Australia; Orygen Youth Health Research Centre and the Centre of Youth Mental Health, The Florey Institute for Neuroscience and Mental Health and the Department of Psychiatry, University of Melbourne, Parkville, 3052, Australia.
| | - Michael Maes
- Deakin University, IMPACT Strategic Research Centre, School of Medicine, P.O. Box 281, Geelong, 3220, Australia; Department of Psychiatry, Chulalongkorn University, Faculty of Medicine, Bangkok, Thailand; Department of Psychiatry, Medical University of Plovdiv, Plovdiv, Bulgaria
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Wang W, Sun H, Che Y, Jiang X. Rasfonin promotes autophagy and apoptosis via upregulation of reactive oxygen species (ROS)/JNK pathway. Mycology 2016; 7:64-73. [PMID: 30123617 PMCID: PMC6059153 DOI: 10.1080/21501203.2016.1170073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 03/21/2016] [Indexed: 02/03/2023] Open
Abstract
Rasfonin is a fungal secondary metabolite demonstrating with antitumour effects. Reactive oxygen species (ROS) are formed as a natural by-product of the normal metabolism of oxygen and have important roles in cell signalling and homeostasis. Studies reported that many fungal secondary metabolites activated either autophagy or apoptosis through ROS generation. In former study, we revealed that rasfonin induced both autophagy and apoptosis, however, whether it promoted aforementioned processes via upregulation of ROS generation remains explored. In the current work, we demonstrated that rasfonin induced autophagy and apoptosis concomitant with a dramatically ROS production. N-Acetylcysteine (NAC), an often used ROS inhibitor, decreased both autophagic flux and caspase-dependent apoptosis by rasfonin. Flow cytometry analysis revealed NAC was able to reduce rasfonin-dependent apoptosis and necrosis. In methanethiosulfonate (MTS) assay, we observed that NAC significantly blocked rasfonin-induced cell viability loss. In addition, we found that rasfonin increased the phosphorylation of c-Jun NH2-terminal kinase (JNK), which was inhibited by NAC. SP600125, an inhibitor of JNK, reduced rasfonin-dependent autophagic flux and apoptosis. Moreover, we demonstrated that rasfonin inhibited the phosphorylation of both 4E-binding protein 1 (4E-BP1) and S6 kinase 1 (S6K1), two main substrates of mammalian target of rapamycin (mTOR). Collectively, rasfonin activated autophagy and apoptosis through upregulation of ROS/JNK signalling.
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Affiliation(s)
- Weijun Wang
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Hui Sun
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yongsheng Che
- Beijing Institute of Pharmacology & Toxicology, Beijing, China
| | - Xuejun Jiang
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
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Sosunov AA, McGovern RA, Mikell CB, Wu X, Coughlin DG, Crino PB, Weiner HL, Ghatan S, Goldman JE, McKhann GM. Epileptogenic but MRI-normal perituberal tissue in Tuberous Sclerosis Complex contains tuber-specific abnormalities. Acta Neuropathol Commun 2015; 3:17. [PMID: 25853525 PMCID: PMC4383198 DOI: 10.1186/s40478-015-0191-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 02/03/2015] [Indexed: 01/08/2023] Open
Abstract
INTRODUCTION Recent evidence has implicated perituberal, MRI-normal brain tissue as a possible source of seizures in tuberous sclerosis complex (TSC). Data on aberrant structural features in this area that may predispose to the initiation or progression of seizures are very limited. We used immunohistochemistry and confocal microscopy to compare epileptogenic, perituberal, MRI-normal tissue with cortical tubers. RESULTS In every sample of epileptogenic, perituberal tissue, we found many abnormal cell types, including giant cells and cytomegalic neurons. The majority of giant cells were surrounded by morphologically abnormal astrocytes with long processes typical of interlaminar astrocytes. Perituberal giant cells and astrocytes together formed characteristic "microtubers". A parallel analysis of tubers showed that many contained astrocytes with features of both protoplasmic and gliotic cells. CONCLUSIONS Microtubers represent a novel pathognomonic finding in TSC and may represent an elementary unit of cortical tubers. Microtubers and cytomegalic neurons in perituberal parenchyma may serve as the source of seizures in TSC and provide potential targets for therapeutic and surgical interventions in TSC.
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Neural plasticity and proliferation in the generation of antidepressant effects: hippocampal implication. Neural Plast 2013; 2013:537265. [PMID: 23862076 PMCID: PMC3703717 DOI: 10.1155/2013/537265] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 05/01/2013] [Accepted: 05/08/2013] [Indexed: 12/15/2022] Open
Abstract
It is widely accepted that changes underlying depression and antidepressant-like effects involve not only alterations in the levels of neurotransmitters as monoamines and their receptors in the brain, but also structural and functional changes far beyond. During the last two decades, emerging theories are providing new explanations about the neurobiology of depression and the mechanism of action of antidepressant strategies based on cellular changes at the CNS level. The neurotrophic/plasticity hypothesis of depression, proposed more than a decade ago, is now supported by multiple basic and clinical studies focused on the role of intracellular-signalling cascades that govern neural proliferation and plasticity. Herein, we review the state-of-the-art of the changes in these signalling pathways which appear to underlie both depressive disorders and antidepressant actions. We will especially focus on the hippocampal cellularity and plasticity modulation by serotonin, trophic factors as brain-derived neurotrophic factor (BDNF), and vascular endothelial growth factor (VEGF) through intracellular signalling pathways—cAMP, Wnt/β-catenin, and mTOR. Connecting the classic monoaminergic hypothesis with proliferation/neuroplasticity-related evidence is an appealing and comprehensive attempt for improving our knowledge about the neurobiological events leading to depression and associated to antidepressant therapies.
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7
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Wang L, Li W, Kong S, Wu P, Zhang C, Gu L, Wang M, Wang W, Gu R. Insulin-like growth factor-1 (IGF-1) inhibits the basolateral Cl channels in the thick ascending limb of the rat kidney. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1163-9. [PMID: 22575459 DOI: 10.1016/j.bbamcr.2012.04.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 03/23/2012] [Accepted: 04/30/2012] [Indexed: 12/17/2022]
Abstract
The aim of the present study is to test the hypothesis that insulin-like-growth factor-1 (IGF-1) plays a role in the regulation of basolateral Cl channels in the thick ascending limb (TAL). The patch-clamp experiments demonstrated that application of IGF-I or insulin inhibited the basolateral 10-pS Cl channels. However, the concentration of insulin required for the inhibition of the Cl channels by 50% (K(1/2)) was ten times higher than those of IGF-1. The inhibitory effect of IGF-I on the 10-pS Cl channels was blocked by suppressing protein tyrosine kinase or by blocking phosphoinositide 3-kinase (PI3K). In contrast, inhibition of phospholipase C (PLC) failed to abolish the inhibitory effect of IGF-1 on the Cl channels in the TAL. Western blot analysis demonstrated that IGF-1 significantly increased the phosphorylation of phospholipid-dependent kinase (PDK) at serine residue 241 (Ser(241)) and AKT at Ser(473) in the isolated medullary TAL. Moreover, inhibition of PI3K with LY294002 abolished the effect of IGF-1 on the phosphorylation of PDK and AKT. The notion that the effect of IGF-1 on the 10-pS Cl channels was induced by stimulation of PDK-AKT-mTOR pathway was further suggested by the finding that rapamycin completely abolished the effect of IGF-1 on the 10-pS Cl channels in the TAL. We conclude that IGF-1 inhibits the basolateral Cl channels by activating PI3K-AKT-mTOR pathways. The inhibitory effect of IGF-1 on the Cl channels may play a role in ameliorating the ischemia-induced renal injury through IGF-1 administration.
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Affiliation(s)
- Lijun Wang
- Department of Pharmacology, Harbin Medical University, Harbin 150086, China
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8
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Chen W, Liu L, Luo Y, Odaka Y, Awate S, Zhou H, Shen T, Zheng S, Lu Y, Huang S. Cryptotanshinone activates p38/JNK and inhibits Erk1/2 leading to caspase-independent cell death in tumor cells. Cancer Prev Res (Phila) 2012; 5:778-87. [PMID: 22490436 DOI: 10.1158/1940-6207.capr-11-0551] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cryptotanshinone (CPT), a natural compound isolated from the plant Salvia miltiorrhiza Bunge, is a potential anticancer agent. However, the underlying mechanism is not well understood. Here, we show that CPT induced caspase-independent cell death in human tumor cells (Rh30, DU145, and MCF-7). Besides downregulating antiapoptotic protein expression of survivin and Mcl-1, CPT increased phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-jun N-terminal kinase (JNK), and inhibited phosphorylation of extracellular signal-regulated kinases 1/2 (Erk1/2). Inhibition of p38 with SB202190 or JNK with SP600125 attenuated CPT-induced cell death. Similarly, silencing p38 or c-Jun also in part prevented CPT-induced cell death. In contrast, expression of constitutively active mitogen-activated protein kinase kinase 1 (MKK1) conferred resistance to CPT inhibition of Erk1/2 phosphorylation and induction of cell death. Furthermore, we found that all of these were attributed to CPT induction of reactive oxygen species (ROS). This is evidenced by the findings that CPT induced ROS in a concentration- and time-dependent manner; CPT induction of ROS was inhibited by N-acetyl-L-cysteine (NAC), a ROS scavenger; and NAC attenuated CPT activation of p38/JNK, inhibition of Erk1/2, and induction of cell death. The results suggested that CPT induction of ROS activates p38/JNK and inhibits Erk1/2, leading to caspase-independent cell death in tumor cells.
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Affiliation(s)
- Wenxing Chen
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, 71130, USA
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Fielhaber JA, Tan J, Joung KB, Attias O, Huegel S, Bader M, Roux PP, Kristof AS. Regulation of karyopherin α1 and nuclear import by mammalian target of rapamycin. J Biol Chem 2012; 287:14325-35. [PMID: 22399302 DOI: 10.1074/jbc.m111.246785] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Under conditions of reduced mitogen or nutritional substrate levels, the serine/threonine kinase target of rapamycin can augment the nuclear content of distinct transcription factors and promote the induction of stress response genes. In its latent (i.e., unphosphorylated) form, the transcription factor STAT1 regulates a subset of genes involved in immune modulation and apoptosis. Based on previous work indicating a functional relationship between mammalian target of rapamycin (mTOR) and the nuclear content of latent STAT1, we investigated the mechanism by which mTOR controls STAT1 nuclear import. By fluorescence confocal microscopy, inactivation of mTOR with rapamycin promoted the nuclear translocation of unphosphorylated STAT1, but not that of a STAT1 mutant incapable of binding its nuclear import adaptor karyopherin-α1 (KPNA1). By immunoprecipitation, KPNA1 was physically associated with mTOR and STAT1 in a complex that translocated to the nucleus in response to rapamycin. Although mTOR is not a kinase for KPNA1, the mTOR-associated phosphatase protein phosphatase 2A catalytic interacted directly with KPNA1 and regulated nuclear import of the mTOR-KPNA1 complex. KPNA1, or its interaction with STAT1, was required for the nuclear import of latent STAT1, transcriptional induction of the STAT1 gene, and caspase-3 activation under conditions of reduced mTOR activity (i.e. rapamycin, glucose starvation, serum withdrawal). Therefore, at low mitogen or nutrient levels, mTOR and protein phosphatase 2A catalytically control the constitutive nuclear import of latent STAT1 by KPNA1, which are key modulators of STAT1 expression and apoptosis.
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Affiliation(s)
- Jill A Fielhaber
- Critical Care Division and Meakins-Christie Laboratories, Faculty of Medicine, McGill University, Montreal, Quebec H3A 1A1, Canada
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10
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Zhou H, Huang S. Role of mTOR signaling in tumor cell motility, invasion and metastasis. Curr Protein Pept Sci 2011; 12:30-42. [PMID: 21190521 DOI: 10.2174/138920311795659407] [Citation(s) in RCA: 206] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 12/20/2010] [Indexed: 01/30/2023]
Abstract
Tumor cell migration and invasion play fundamental roles in cancer metastasis. The mammalian target of rapamycin (mTOR), a highly conserved and ubiquitously expressed serine/threonine (Ser/Thr) kinase, is a central regulator of cell growth, proliferation, differentiation and survival. Recent studies have shown that mTOR also plays a critical role in the regulation of tumor cell motility, invasion and cancer metastasis. Current knowledge indicates that mTOR functions as two distinct complexes, mTORC1 and mTORC2. mTORC1 phosphorylates p70 S6 kinase (S6K1) and eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1), and regulates cell growth, proliferation, survival and motility. mTORC2 phosphorylates Akt, protein kinase C α (PKCα) and the focal adhesion proteins, and controls the activities of the small GTPases (RhoA, Cdc42 and Rac1), and regulates cell survival and the actin cytoskeleton. Here we briefly review recent knowledge of mTOR complexes and the role of mTOR signaling in tumor cell migration and invasion. We also discuss recent efforts about the mechanism by which rapamycin, a specific inhibitor of mTOR, inhibits cell migration, invasion and cancer metastasis.
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Affiliation(s)
- Hongyu Zhou
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA
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Abstract
Studies of epilepsy have mainly focused on the membrane proteins that control neuronal excitability. Recently, attention has been shifting to intracellular proteins and their interactions, signaling cascades and feedback regulation as they relate to epilepsy. The mTOR (mammalian target of rapamycin) signal transduction pathway, especially, has been suggested to play an important role in this regard. These pathways are involved in major physiological processes as well as in numerous pathological conditions. Here, involvement of the mTOR pathway in epilepsy will be reviewed by presenting; an overview of the pathway, a brief description of key signaling molecules, a summary of independent reports and possible implications of abnormalities of those molecules in epilepsy, a discussion of the lack of experimental data, and questions raised for the understanding its epileptogenic mechanism.
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Affiliation(s)
- Chang Hoon Cho
- Epilepsy Research Laboratory Department of Pediatrics Children's Hospital of Philadelphia, Pennsylvania 19104, USA.
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12
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Chong ZZ, Shang YC, Zhang L, Wang S, Maiese K. Mammalian target of rapamycin: hitting the bull's-eye for neurological disorders. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2010; 3:374-91. [PMID: 21307646 PMCID: PMC3154047 DOI: 10.4161/oxim.3.6.14787] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The mammalian target of rapamycin (mTOR) and its associated cell signaling pathways have garnered significant attention for their roles in cell biology and oncology. Interestingly,the explosion of information in this field has linked mTOR to neurological diseases with promising initial studies. mTOR, a 289 kDa serine/threonine protein kinase, plays an important role in cell growth and proliferation and is activated through phosphorylation in response to growth factors, mitogens and hormones. Growth factors, amino acids, cellular nutrients and oxygen deficiency can downregulate mTOR activity. The function of mTOR signaling is mediated primarily through two mTOR complexes: mTORC1 and mTORC2. mTORC1 initiates cap-dependent protein translation, a rate-limiting step of protein synthesis, through the phosphorylation of the targets eukaryotic initiation factor 4E-binding protein 1 (4EBP1) and p70 ribosomal S6 kinase (p70S6K). In contrast, mTORC2 regulates development of the cytoskeleton and also controls cell survival. Although closely tied to tumorigenesis, mTOR and the downstream signaling pathways are significantly involved in the central nervous system (CNS) with synaptic plasticity, memory retention, neuroendocrine regulation associated with food intake and puberty and modulation of neuronal repair following injury. The signaling pathways of mTOR also are believed to be a significant component in a number of neurological diseases, such as Alzheimer disease, Parkinson disease and Huntington disease, tuberous sclerosis, neurofibromatosis, fragile X syndrome, epilepsy, traumatic brain injury and ischemic stroke. Here we describe the role of mTOR in the CNS and illustrate the potential for new strategies directed against neurological disorders.
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Affiliation(s)
- Zhao Zhong Chong
- Department of Neurology and Neurosciences, Cancer Center, University of Medicine and Dentistry - New Jersey Medical School, Newark, NJ, USA
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13
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Ayuso MI, Hernández-Jiménez M, Martín ME, Salinas M, Alcázar A. New hierarchical phosphorylation pathway of the translational repressor eIF4E-binding protein 1 (4E-BP1) in ischemia-reperfusion stress. J Biol Chem 2010; 285:34355-63. [PMID: 20736160 PMCID: PMC2966049 DOI: 10.1074/jbc.m110.135103] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Eukaryotic initiation factor (eIF) 4E-binding protein 1 (4E-BP1) is a translational repressor that is characterized by its capacity to bind specifically to eIF4E and inhibit its interaction with eIF4G. Phosphorylation of 4E-BP1 regulates eIF4E availability, and therefore, cap-dependent translation, in cell stress. This study reports a physiological study of 4E-BP1 regulation by phosphorylation using control conditions and a stress-induced translational repression condition, ischemia-reperfusion (IR) stress, in brain tissue. In control conditions, 4E-BP1 was found in four phosphorylation states that were detected by two-dimensional gel electrophoresis and Western blotting, which corresponded to Thr69-phosphorylated alone, Thr69- and Thr36/Thr45-phosphorylated, all these plus Ser64 phosphorylation, and dephosphorylation of the sites analyzed. In control or IR conditions, no Thr36/Thr45 phosphorylation alone was detected without Thr69 phosphorylation, and neither was Ser64 phosphorylation without Thr36/Thr45/Thr69 phosphorylation detected. Ischemic stress induced 4E-BP1 dephosphorylation at Thr69, Thr36/Thr45, and Ser64 residues, with 4E-BP1 remaining phosphorylated at Thr69 alone or dephosphorylated. In the subsequent reperfusion, 4E-BP1 phosphorylation was induced at Thr36/Thr45 and Ser64, in addition to Thr69. Changes in 4E-BP1 phosphorylation after IR were according to those found for Akt and mammalian target of rapamycin (mTOR) kinases. These results demonstrate a new hierarchical phosphorylation for 4E-BP1 regulation in which Thr69 is phosphorylated first followed by Thr36/Thr45 phosphorylation, and Ser64 is phosphorylated last. Thr69 phosphorylation alone allows binding to eIF4E, and subsequent Thr36/Thr45 phosphorylation was sufficient to dissociate 4E-BP1 from eIF4E, which led to eIF4E-4G interaction. These data help to elucidate the physiological role of 4E-BP1 phosphorylation in controlling protein synthesis.
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Affiliation(s)
- María I Ayuso
- Department of Investigation, Hospital Ramón y Cajal, 28034 Madrid, Spain
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Abstract
Tumor cell migration is a key step in the formation of cancer metastasis. The mammalian target of rapamycin (mTOR), a highly conserved and ubiquitously expressed serinethreonine kinase, has been intensely studied for over a decade as a central regulator of cell growth, proliferation, differentiation, and survival. Recent data have shown that mTOR also plays a critical role in the regulation of tumor cell motility and cancer metastasis. Here, we briefly review recent advances regarding mTOR signaling in tumor cell motility. We also discuss recent findings about the mechanism by which rapamycin, a specific inhibitor of mTOR, inhibits cell motility in vitro and metastasis in vivo.
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Affiliation(s)
- Hongyu Zhou
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA
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15
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Kolb EA, Kamara D, Zhang W, Lin J, Hingorani P, Baker L, Houghton P, Gorlick R. R1507, a fully human monoclonal antibody targeting IGF-1R, is effective alone and in combination with rapamycin in inhibiting growth of osteosarcoma xenografts. Pediatr Blood Cancer 2010; 55:67-75. [PMID: 20486173 DOI: 10.1002/pbc.22479] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND The combination of rapamycin and R1507, a fully human IgG1 monoclonal antibody targeting the IGF-1 receptor (IGF-1R), in osteosarcoma xenograft tumors in vivo is evaluated in this report. PROCEDURE Six osteosarcoma xenograft tumor models were evaluated for growth inhibition after monotherapy with R1507, rapamycin, and the combination of both drugs. Phosphorylation of proteins involved in IGF-1R signaling is evaluated at various time points by immunoblotting. RESULTS IGF-1R was expressed in five of the six human osteosarcoma tumor lines. Objective responses to R1507 were seen in four of the six tumor lines (OS1, OS2, OS9, and OS17) including one complete response in OS1. IGF-1R protein levels did not predict degree of response to R1507 in the sensitive tumors. However, in one of the two R1507-resistant tumors (OS33), there was a minimal expression of IGF-1R. An increase in AKT phosphorylation was observed in all the osteosarcoma tumors treated with rapamycin. However, phosphorylation of AKT was inhibited when rapamycin was used in combination with R1507. In three of the xenograft tumor lines, there was an improvement in response when R1507 was used in combination with rapamycin. CONCLUSIONS IGF-1R inhibition by R1507 induced tumor growth delays and improvement in event-free survival in four of six osteosarcoma xenograft tumor lines. R1507 negates increased signaling through AKT in response to mammalian target of rapamycin inhibition, suggesting that the combination is worthy of further evaluation in patients. As R1507 and other IGF-1R inhibitors advance in clinical trials, it will be important to understand biomarkers of response and pathways of resistance.
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Affiliation(s)
- E Anders Kolb
- Division of Hematology and Oncology, Alfred I. duPont Hospital for Children, Nemours Center for Childhood Cancer Research, Wilmington, Delaware 19803, USA.
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16
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Liu L, Chen L, Luo Y, Chen W, Zhou H, Xu B, Han X, Shen T, Huang S. Rapamycin inhibits IGF-1 stimulated cell motility through PP2A pathway. PLoS One 2010; 5:e10578. [PMID: 20485667 PMCID: PMC2868031 DOI: 10.1371/journal.pone.0010578] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Accepted: 04/20/2010] [Indexed: 01/11/2023] Open
Abstract
Serine/threonine (Ser/Thr) protein phosphatase 2A (PP2A) has been implicated as a novel component of the mammalian target of rapamycin (mTOR) signaling pathway. Recently we have demonstrated that mTOR regulates cell motility in part through p70 S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1) pathways. Little is known about the role of PP2A in the mTOR-mediated cell motility. Here we show that rapamycin inhibited the basal or insulin-like growth factor 1 (IGF-1)-induced motility of human Ewing sarcoma (Rh1) and rhabdomyosarcoma (Rh30) cells. Treatment of the cells with rapamycin activated PP2A activity, and concurrently inhibited IGF-1 stimulated phosphorylation of Erk1/2. Inhibition of Erk1/2 with PD98059 did not significantly affect the basal mobility of the cells, but dramatically inhibited IGF-1-induced cell motility. Furthermore, inhibition of PP2A with okadaic acid significantly attenuated the inhibitory effect of rapamycin on IGF-1-stimulated phosphorylation of Erk1/2 as well as cell motility. Consistently, expression of dominant negative PP2A conferred resistance to IGF-1-stimulated phosphorylation of Erk1/2 and cell motility. Expression of constitutively active MKK1 also attenuated rapamycin inhibition of IGF-1-stimulated phosphorylation of Erk1/2 and cell motility. The results suggest that rapamycin inhibits cell motility, in part by targeting PP2A-Erk1/2 pathway.
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Affiliation(s)
- Lei Liu
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Long Chen
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Yan Luo
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Wenxing Chen
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Hongyu Zhou
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Baoshan Xu
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Xiuzhen Han
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Tao Shen
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
| | - Shile Huang
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, United States of America
- * E-mail:
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17
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Braunstein S, Badura ML, Xi Q, Formenti SC, Schneider RJ. Regulation of protein synthesis by ionizing radiation. Mol Cell Biol 2009; 29:5645-56. [PMID: 19704005 PMCID: PMC2772731 DOI: 10.1128/mcb.00711-09] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 07/13/2009] [Accepted: 08/17/2009] [Indexed: 12/22/2022] Open
Abstract
Ionizing radiation (IR) is a physiologically important stress to which cells respond by the activation of multiple signaling pathways. Using a panel of immortalized and transformed breast epithelial cell lines, we demonstrate that IR regulation of protein synthesis occurs in nontransformed cells and is lost with transformation. In nontransformed cells, IR rapidly activates the MAP kinases ERK1/2, resulting in an early transient increase in cap-dependent mRNA translation that involves mTOR and is radioprotective, enhancing the translation of a subset of mRNAs encoding proteins involved in DNA repair and cell survival. Following a transient increase in translation, IR-sensitive (nontransformed) cells inhibit cap-dependent protein synthesis through a mechanism that involves activation of p53, induction of Sestrin 1 and 2 genes, and stimulation of AMP kinase, inhibiting mTOR and hypophosphorylating 4E-BP1. IR is shown to block proteasome-mediated decay of 4E-BP1, increasing its abundance and the sequestration of eIF4E. The IR signal that impairs mTOR-dependent protein synthesis at late times is assembly of the DNA damage response machinery, consisting of Mre11, Rad50, and NBS1 (MRN); activation of the MRN complex kinase ATM; and p53. These results link genotoxic signaling from the DNA damage response complex to the control of protein synthesis.
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Affiliation(s)
- Steve Braunstein
- Department of Microbiology, 550 First Avenue, Department of Radiation Oncology, 160 East 34th Street, New York University School of Medicine, New York, New York 10016
| | - Michelle L. Badura
- Department of Microbiology, 550 First Avenue, Department of Radiation Oncology, 160 East 34th Street, New York University School of Medicine, New York, New York 10016
| | - Qiaoran Xi
- Department of Microbiology, 550 First Avenue, Department of Radiation Oncology, 160 East 34th Street, New York University School of Medicine, New York, New York 10016
| | - Silvia C. Formenti
- Department of Microbiology, 550 First Avenue, Department of Radiation Oncology, 160 East 34th Street, New York University School of Medicine, New York, New York 10016
| | - Robert J. Schneider
- Department of Microbiology, 550 First Avenue, Department of Radiation Oncology, 160 East 34th Street, New York University School of Medicine, New York, New York 10016
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Thorn SR, Regnault TRH, Brown LD, Rozance PJ, Keng J, Roper M, Wilkening RB, Hay WW, Friedman JE. Intrauterine growth restriction increases fetal hepatic gluconeogenic capacity and reduces messenger ribonucleic acid translation initiation and nutrient sensing in fetal liver and skeletal muscle. Endocrinology 2009; 150:3021-30. [PMID: 19342452 PMCID: PMC2703533 DOI: 10.1210/en.2008-1789] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Expression of key metabolic genes and proteins involved in mRNA translation, energy sensing, and glucose metabolism in liver and skeletal muscle were investigated in a late-gestation fetal sheep model of placental insufficiency intrauterine growth restriction (PI-IUGR). PI-IUGR fetuses weighed 55% less; had reduced oxygen, glucose, isoleucine, insulin, and IGF-I levels; and had 40% reduction in net branched chain amino acid uptake. In PI-IUGR skeletal muscle, levels of insulin receptor were increased 80%, whereas phosphoinositide-3 kinase (p85) and protein kinase B (AKT2) were reduced by 40%. Expression of eukaryotic initiation factor-4e was reduced 45% in liver, suggesting a unique mechanism limiting translation initiation in PI-IUGR liver. There was either no change (AMP activated kinase, mammalian target of rapamycin) or a paradoxical decrease (protein phosphatase 2A, eukaryotic initiation factor-2 alpha) in activation of major energy and cell stress sensors in PI-IUGR liver and skeletal muscle. A 13- to 20-fold increase in phosphoenolpyruvate carboxykinase and glucose 6 phosphatase mRNA expression in the PI-IUGR liver was-associated with a 3-fold increase in peroxisome proliferator-activated receptor-gamma coactivator-1 alpha mRNA and increased phosphorylation of cAMP response element binding protein. Thus PI-IUGR is-associated with reduced branched chain amino acid uptake and growth factors, yet up-regulation of proximal insulin signaling and a marked increase in the gluconeogenic pathway. Lack of activation of several energy and stress sensors in fetal liver and skeletal muscle, despite hypoxia and low energy status, suggests a novel strategy for survival in the PI-IUGR fetus but with potential maladaptive consequences for reduced nutrient sensing and insulin sensitivity in postnatal life.
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Affiliation(s)
- Stephanie R Thorn
- Department of Pediatrics, University of Colorado Denver, Aurora, Colorado 80045, USA
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19
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Lesma E, Grande V, Ancona S, Carelli S, Di Giulio AM, Gorio A. Anti-EGFR antibody efficiently and specifically inhibits human TSC2-/- smooth muscle cell proliferation. Possible treatment options for TSC and LAM. PLoS One 2008; 3:e3558. [PMID: 18958173 PMCID: PMC2570214 DOI: 10.1371/journal.pone.0003558] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Accepted: 10/06/2008] [Indexed: 11/28/2022] Open
Abstract
Background Tuberous sclerosis complex (TSC), a tumor syndrome caused by mutations in TSC1 or TSC2 genes, is characterized by the development of hamartomas. We previously isolated, from an angiomyolipoma of a TSC2 patient, a homogenous population of smooth muscle-like cells (TSC2−/− ASM cells) that have a mutation in the TSC2 gene as well as TSC2 loss of heterozygosity (LOH) and consequently, do not produce the TSC2 gene product, tuberin. TSC2−/− ASM cell proliferation is EGF-dependent. Methods and Findings Effects of EGF on proliferation of TSC2−/− ASM cells and TSC2−/− ASM cells transfected with TSC2 gene were determined. In contrast to TSC2−/− ASM cells, growth of TSC2-transfected cells was not dependent on EGF. Moreover, phosphorylation of Akt, PTEN, Erk and S6 was significantly decreased. EGF is a proliferative factor of TSC2−/− ASM cells. Exposure of TSC2−/− ASM cells to anti-EGFR antibodies significantly inhibited their proliferation, reverted reactivity to HMB45 antibody, a marker of TSC2−/− cell phenotype, and inhibited constitutive phosphorylation of S6 and ERK. Exposure of TSC2−/− ASM cells to rapamycin reduced the proliferation rate, but only when added at plating time. Although rapamycin efficiently inhibited S6 phosphorylation, it was less efficient than anti-EGFR antibody in reverting HMB45 reactivity and blocking ERK phosphorylation. In TSC2−/− ASM cells specific PI3K inhibitors (e.g. LY294002, wortmannin) and Akt1 siRNA had little effect on S6 and ERK phosphorylation. Following TSC2-gene transfection, Akt inhibitor sensitivity was observed. Conclusion Our results show that an EGF independent pathway is more important than that involving IGF-I for growth and survival of TSC−/− ASM cells, and such EGF-dependency is the result of the lack of tuberin.
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MESH Headings
- Adult
- Antibodies/pharmacology
- Antibodies/therapeutic use
- Antibody Affinity
- Antibody Specificity
- Cell Proliferation/drug effects
- Cells, Cultured
- ErbB Receptors/immunology
- Female
- Humans
- Lymphangioleiomyomatosis/genetics
- Lymphangioleiomyomatosis/metabolism
- Lymphangioleiomyomatosis/pathology
- Lymphangioleiomyomatosis/therapy
- Models, Biological
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/pathology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Myocytes, Smooth Muscle/physiology
- Smooth Muscle Tumor/genetics
- Smooth Muscle Tumor/metabolism
- Smooth Muscle Tumor/pathology
- Smooth Muscle Tumor/therapy
- Transfection
- Tuberous Sclerosis/genetics
- Tuberous Sclerosis/metabolism
- Tuberous Sclerosis/pathology
- Tuberous Sclerosis/therapy
- Tuberous Sclerosis Complex 2 Protein
- Tumor Suppressor Proteins/genetics
- Tumor Suppressor Proteins/metabolism
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Affiliation(s)
- Elena Lesma
- Laboratory of Pharmacology , Department of Medicine, Surgery and Dentistry- Polo H. San Paolo, Faculty of Medicine, University of Milan, Milan, Italy.
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20
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Good DW, George T, Watts BA. Nerve growth factor inhibits Na+/H+ exchange and formula absorption through parallel phosphatidylinositol 3-kinase-mTOR and ERK pathways in thick ascending limb. J Biol Chem 2008; 283:26602-11. [PMID: 18660503 DOI: 10.1074/jbc.m803019200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In the medullary thick ascending limb, inhibiting the basolateral NHE1 Na(+)/H(+) exchanger with nerve growth factor (NGF) induces actin cytoskeleton remodeling that secondarily inhibits apical NHE3 and transepithelial HCO(3)(-) absorption. The inhibition by NGF is mediated 50% through activation of extracellular signal-regulated kinase (ERK). Here we examined the signaling pathway responsible for the remainder of the NGF-induced inhibition. Inhibition of HCO(3)(-) absorption was reduced 45% by the phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin or LY294002 and 50% by rapamycin, a specific inhibitor of mammalian target of rapamycin (mTOR), a downstream effector of PI3K. The combination of a PI3K inhibitor plus rapamycin did not cause a further reduction in the inhibition by NGF. In contrast, the combination of a PI3K inhibitor plus the MEK/ERK inhibitor U0126 completely eliminated inhibition by NGF. Rapamycin decreased NGF-induced inhibition of basolateral NHE1 by 45%. NGF induced a 2-fold increase in phosphorylation of Akt, a PI3K target linked to mTOR activation, and a 2.2-fold increase in the activity of p70 S6 kinase, a downstream effector of mTOR. p70 S6 kinase activation was blocked by wortmannin and rapamycin, consistent with PI3K, mTOR, and p70 S6 kinase in a linear pathway. Rapamycin-sensitive inhibition of NHE1 by NGF was associated with an increased level of phosphorylated mTOR in the basolateral membrane domain. These findings indicate that NGF inhibits HCO(3)(-) absorption in the medullary thick ascending limb through the parallel activation of PI3K-mTOR and ERK signaling pathways, which converge to inhibit NHE1. The results identify a role for mTOR in the regulation of Na(+)/H(+) exchange activity and implicate NHE1 as a possible downstream effector contributing to mTOR's effects on cell growth, proliferation, survival, and tumorigenesis.
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Affiliation(s)
- David W Good
- Departments of Medicine, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
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21
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Molhoek KR, Griesemann H, Shu J, Gershenwald JE, Brautigan DL, Slingluff CL. Human melanoma cytolysis by combined inhibition of mammalian target of rapamycin and vascular endothelial growth factor/vascular endothelial growth factor receptor-2. Cancer Res 2008; 68:4392-7. [PMID: 18519701 PMCID: PMC2727753 DOI: 10.1158/0008-5472.can-07-5844] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Vascular endothelial growth factor (VEGF) plays a vital role in tumor angiogenesis. VEGF is produced by human melanomas, and the VEGF receptor 2 (VEGFR-2) is expressed by most advanced stage melanomas, suggesting the possibility of an autocrine loop. Here, we show that bevacizumab, an anti-VEGF antibody, inhibits proliferation of VEGFR-2(+) melanoma cell lines by an average of 41%; however, it failed to inhibit proliferation of VEGFR-2(neg) melanoma cell lines. The growth inhibitory effect of bevacizumab was eliminated by VEGFR-2 knockdown with small interfering RNA, showing that VEGF autocrine growth in melanoma is mediated through VEGFR-2. However, bevacizumab inhibition of autocrine signals did not completely inhibit cell proliferation nor cause cell death. Cell survival is mediated partially through mammalian target of rapamycin (mTOR), which is inhibited by rapamycin. Combination of bevacizumab with rapamycin caused loss of half of the VEGFR-2(+) melanoma cells, but no reduction in the number of VEGFR-2(neg) melanoma cells. The results show (a) an autocrine growth loop active in VEGFR-2(+) melanoma, (b) a nonangiogenic mechanism for inhibition of melanoma by blocking autocrine VEGFR-2 activation, and (c) a possible therapeutic role for combination of inhibitors of mTOR plus VEGF in selected melanomas.
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Affiliation(s)
- Kerrington R. Molhoek
- Department of Surgery, Division of Surgical Oncology, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Heinrich Griesemann
- Department of Immunology, Institute for Cell Biology, Eberhard Karls University Tuebingen, Germany
| | - Jianfen Shu
- Department of Public Health Sciences, Division of Biostatistics and Epidemiology, University of Virginia, Charlottesville, VA, USA
| | - Jeffrey E. Gershenwald
- Departments of Surgical Oncology and Cancer Biology, University of Texas M. D. Anderson Cancer Center, Houston, TX, USA
| | - David L. Brautigan
- Center for Cell Signaling, University of Virginia Health System, Charlottesville, VA, USA
| | - Craig L. Slingluff
- Department of Surgery, Division of Surgical Oncology, University of Virginia School of Medicine, Charlottesville, VA, USA
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The yeast Tor signaling pathway is involved in G2/M transition via polo-kinase. PLoS One 2008; 3:e2223. [PMID: 18493323 PMCID: PMC2375053 DOI: 10.1371/journal.pone.0002223] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Accepted: 04/02/2008] [Indexed: 12/20/2022] Open
Abstract
The target of rapamycin (Tor) protein plays central roles in cell growth. Rapamycin inhibits cell growth and promotes cell cycle arrest at G1 (G0). However, little is known about whether Tor is involved in other stages of the cell division cycle. Here we report that the rapamycin-sensitive Tor complex 1 (TORC1) is involved in G2/M transition in S. cerevisiae. Strains carrying a temperature-sensitive allele of KOG1 (kog1-105) encoding an essential component of TORC1, as well as yeast cell treated with rapamycin show mitotic delay with prolonged G2. Overexpression of Cdc5, the yeast polo-like kinase, rescues the growth defect of kog1-105, and in turn, Cdc5 activity is attenuated in kog1-105 cells. The TORC1-Type2A phosphatase pathway mediates nucleocytoplasmic transport of Cdc5, which is prerequisite for its proper localization and function. The C-terminal polo-box domain of Cdc5 has an inhibitory role in nuclear translocation. Taken together, our results indicate a novel function of Tor in the regulation of cell cycle and proliferation.
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