51
|
Molecular dynamics study on inhibition mechanism of CDK-2 and GSK-3β by CHEMBL272026 molecule. Struct Chem 2016. [DOI: 10.1007/s11224-016-0803-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
52
|
De Souza EO, Lowery RP, Wilson JM, Sharp MH, Mobley CB, Fox CD, Lopez HL, Shields KA, Rauch JT, Healy JC, Thompson RM, Ormes JA, Joy JM, Roberts MD. Effects of Arachidonic Acid Supplementation on Acute Anabolic Signaling and Chronic Functional Performance and Body Composition Adaptations. PLoS One 2016; 11:e0155153. [PMID: 27182886 PMCID: PMC4868363 DOI: 10.1371/journal.pone.0155153] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 04/25/2016] [Indexed: 12/25/2022] Open
Abstract
Background The primary purpose of this investigation was to examine the effects of arachidonic acid (ARA) supplementation on functional performance and body composition in trained males. In addition, we performed a secondary study looking at molecular responses of ARA supplementation following an acute exercise bout in rodents. Methods Thirty strength-trained males (age: 20.4 ± 2.1 yrs) were randomly divided into two groups: ARA or placebo (i.e. CTL). Then, both groups underwent an 8-week, 3-day per week, non-periodized training protocol. Quadriceps muscle thickness, whole-body composition scan (DEXA), muscle strength, and power were assessed at baseline and post-test. In the rodent model, male Wistar rats (~250 g, ~8 weeks old) were pre-fed with either ARA or water (CTL) for 8 days and were fed the final dose of ARA prior to being acutely strength trained via electrical stimulation on unilateral plantar flexions. A mixed muscle sample was removed from the exercised and non-exercised leg 3 hours post-exercise. Results Lean body mass (2.9%, p<0.0005), upper-body strength (8.7%, p<0.0001), and peak power (12.7%, p<0.0001) increased only in the ARA group. For the animal trial, GSK-β (Ser9) phosphorylation (p<0.001) independent of exercise and AMPK phosphorylation after exercise (p-AMPK less in ARA, p = 0.041) were different in ARA-fed versus CTL rats. Conclusions Our findings suggest that ARA supplementation can positively augment strength-training induced adaptations in resistance-trained males. However, chronic studies at the molecular level are required to further elucidate how ARA combined with strength training affect muscle adaptation.
Collapse
Affiliation(s)
- Eduardo O De Souza
- Department of Health Sciences and Human Performance, The University of Tampa, Tampa, FL, United States of America
| | - Ryan P Lowery
- Department of Health Sciences and Human Performance, The University of Tampa, Tampa, FL, United States of America
| | - Jacob M Wilson
- Department of Health Sciences and Human Performance, The University of Tampa, Tampa, FL, United States of America
| | - Matthew H Sharp
- Department of Health Sciences and Human Performance, The University of Tampa, Tampa, FL, United States of America
| | - Christopher Brooks Mobley
- Molecular and Applied Sciences Laboratory, School of Kinesiology, Auburn University, Auburn, AL, United States of America
| | - Carlton D Fox
- Molecular and Applied Sciences Laboratory, School of Kinesiology, Auburn University, Auburn, AL, United States of America
| | - Hector L Lopez
- The Center for Applied Health Sciences, 4302 Allen Road, STE 120, Stow, OH, 44224, United States of America
| | - Kevin A Shields
- Department of Health Sciences and Human Performance, The University of Tampa, Tampa, FL, United States of America
| | - Jacob T Rauch
- Department of Health Sciences and Human Performance, The University of Tampa, Tampa, FL, United States of America
| | - James C Healy
- Molecular and Applied Sciences Laboratory, School of Kinesiology, Auburn University, Auburn, AL, United States of America
| | - Richard M Thompson
- Molecular and Applied Sciences Laboratory, School of Kinesiology, Auburn University, Auburn, AL, United States of America
| | - Jacob A Ormes
- Department of Health Sciences and Human Performance, The University of Tampa, Tampa, FL, United States of America
| | - Jordan M Joy
- Department of Health Sciences and Human Performance, The University of Tampa, Tampa, FL, United States of America
| | - Michael D Roberts
- Molecular and Applied Sciences Laboratory, School of Kinesiology, Auburn University, Auburn, AL, United States of America
| |
Collapse
|
53
|
Patel D, Kharkar PS, Nandave M. Emerging roles of system antiporter and its inhibition in CNS disorders. Mol Membr Biol 2015; 32:89-116. [PMID: 26508554 DOI: 10.3109/09687688.2015.1096972] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
| | - Prashant S. Kharkar
- Department of Pharmaceutical Chemistry, SPP School of Pharmacy and Technology Management, SVKM’s NMIMS University, Mumbai, India
| | | |
Collapse
|
54
|
Swetha M, Ramaiah KVA. Insulin treatment promotes tyrosine phosphorylation of PKR and inhibits polyIC induced PKR threonine phosphorylation. Arch Biochem Biophys 2015; 585:98-108. [PMID: 26321373 DOI: 10.1016/j.abb.2015.07.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 07/18/2015] [Accepted: 07/20/2015] [Indexed: 12/17/2022]
Abstract
Tyrosine phosphorylation of insulin receptor beta (IRβ) in insulin treated HepG2 cells is inversely correlated to ser(51) phosphorylation in the alpha-subunit of eukaryotic initiation factor 2 (eIF2α) that regulates protein synthesis. Insulin stimulates interaction between IRβ and PKR, double stranded RNA-dependent protein kinase, also known as EIF2AK2, and phosphorylation of tyrosine residues in PKR, as analyzed by immunoprecipitation and pull down assays using anti-IRβ and anti-phosphotyrosine antibodies, recombinant IRβ and immunopurified PKR. Further polyIC or synthetic double stranded RNA-induced threonine phosphorylation or activation of immunopurified and cellular PKR is suppressed in the presence of insulin treated purified IRβ and cell extracts. Acute, but not chronic, insulin treatment enhances tyrosine phosphorylation of IRβ, its interaction with PKR and tyrosine phosphorylation of PKR. In contrast, lipopolysaccharide that stimulates threonine phosphorylation of PKR and eIF2α phosphorylation and AG 1024, an inhibitor of the tyrosine kinase activity of IRβ, reduces PKR association with the receptor, IRβ in HepG2 cells. These findings therefore may suggest that tyrosine phosphorylated PKR plays a role in the regulation of insulin induced protein synthesis and in maintaining insulin sensitivity, whereas, suppression of polyIC-mediated threonine phosphorylation of PKR by insulin compromises its ability to fight against virus infection in host cells.
Collapse
Affiliation(s)
- Medchalmi Swetha
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, 500 046, Telangana, India
| | - Kolluru V A Ramaiah
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, 500 046, Telangana, India.
| |
Collapse
|
55
|
Doelman J, Curtis R, Carson M, Kim J, Metcalf J, Cant J. Essential amino acid infusions stimulate mammary expression of eukaryotic initiation factor 2Bε but milk protein yield is not increased during an imbalance. J Dairy Sci 2015; 98:4499-508. [DOI: 10.3168/jds.2014-9051] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 03/16/2015] [Indexed: 01/08/2023]
|
56
|
Rahmati M, Taherabadi SJ, Mehrabi M. Decreased Activity in Neuropathic Pain Form and Gene Expression of Cyclin-Dependent Kinase5 and Glycogen Synthase Kinase-3 Beta in Soleus Muscle of Wistar Male Rats. IRANIAN RED CRESCENT MEDICAL JOURNAL 2015; 17:e23324. [PMID: 26290750 PMCID: PMC4537785 DOI: 10.5812/ircmj.23324] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2014] [Revised: 11/18/2014] [Accepted: 03/25/2015] [Indexed: 02/07/2023]
Abstract
BACKGROUND The relationship between decreased activity/neuropathic pain and gene expression alterations in soleus muscle has remained elusive. OBJECTIVES In this experimental study, we investigated the effects of decreased activity in neuropathic pain form on Cyclin-Dependent Kinase 5 (CDK5) and Glycogen Synthase Kinase-3 β (GSK-3β) gene expression in soleus muscle of rats. MATERIALS AND METHODS Twelve male Wistar rats were randomly divided into three groups: (1) tight ligation of the L5 spinal nerve (SNL: n = 4); (2) sham surgery (Sham: n = 4), and (3) control (C: n = 4). The threshold to produce a withdrawal response to a mechanical and thermal stimulus was measured using von Frey filaments and radiation heat apparatus, respectively. Following 4 weeks after surgery, the left soleus muscle was removed and mRNA levels were determined by real-time Polymerase Chain Reaction (PCR). RESULTS Compared to control animals, L5 ligated animals developed mechanical and heat hypersensitivity during total period of study. Soleus muscle weight as well as CDK5 mRNA levels (less than ~ 0.4 fold) was decreased and GSK-3β mRNA levels (up to ~ 7 folds) increased in L5 ligated animals. CONCLUSIONS These results showed enhanced muscle atrophy processes following peripheral nerve damage and might provide a useful approach to study underlying muscle mechanisms associated with clinical neuropathic pain syndromes.
Collapse
Affiliation(s)
- Masoud Rahmati
- Department of Physical Education and Sport Sciences, Lorestan University, Khoram Abad, IR Iran
- Corresponding Author: Masoud Rahmati, Department of Physical Education and Sport Sciences, Lorestan University, Khoram Abad, IR Iran. Tel: +98-9124525538, Fax: +98-6614215393, E-mail:
| | - Seyed Jalal Taherabadi
- Department of Physical Education and Sport Sciences, Lorestan University, Khoram Abad, IR Iran
| | - Mahmoud Mehrabi
- Department of Physical Education and Sport Sciences, Lorestan University, Khoram Abad, IR Iran
| |
Collapse
|
57
|
Bakker AD, Jaspers RT. IL-6 and IGF-1 Signaling Within and Between Muscle and Bone: How Important is the mTOR Pathway for Bone Metabolism? Curr Osteoporos Rep 2015; 13:131-9. [PMID: 25712618 PMCID: PMC4417129 DOI: 10.1007/s11914-015-0264-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Insulin-like growth factor 1 (IGF-1) and interleukin 6 (IL-6) play an important role in the adaptation of both muscle and bone to mechanical stimuli. Here, we provide an overview of the functions of IL-6 and IGF-1 in bone and muscle metabolism, and the intracellular signaling pathways that are well known to mediate these functions. In particular, we discuss the Akt/mammalian target of rapamycin (mTOR) pathway which in skeletal muscle is known for its key role in regulating the rate of mRNA translation (protein synthesis). Since the role of the mTOR pathway in bone is explored to a much lesser extent, we discuss what is known about this pathway in bone and the potential role of this pathway in bone remodeling. We will also discuss the possible ways of influencing IGF-1 or IL-6 signaling by osteocytes and the clinical implications of pharmacological or nutritional modulation of the Akt/mTOR pathway.
Collapse
Affiliation(s)
- Astrid D. Bakker
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Gustav Mahlerlaan 3004, 1081 LA Amsterdam, The Netherlands
| | - Richard T. Jaspers
- Laboratory for Myology, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands
| |
Collapse
|
58
|
Abstract
The insulin-like growth factor 1 (IGF-1) signaling pathway regulates critical biological processes including development, homeostasis, and aging. Dysregulation of this pathway has been implicated in a myriad of diseases such as cancers, neurodegenerative diseases, and metabolic disorders, making the IGF-1 signaling pathway a prime target to develop therapeutic and intervention strategies. Recently, small non-coding RNA molecules in ∼22 nucleotide length, microRNAs (miRNAs), have emerged as a new regulator of biological processes in virtually all organ systems and increasing studies are linking altered miRNA function to disease mechanisms. A miRNA binds to 3'UTRs of multiple target genes and coordinately downregulates their expression, thereby exerting a profound influence on gene regulatory networks. Here we review the components of the IGF-1 signaling pathway that are known targets of miRNA regulation, and highlight recent studies that suggest therapeutic potential of these miRNAs against various diseases.
Collapse
Affiliation(s)
- Hwa Jin Jung
- Department of Genetics, Albert Einstein College of Medicine New York, NY, USA
| | - Yousin Suh
- Department of Genetics, Albert Einstein College of Medicine New York, NY, USA ; Department of Medicine, Albert Einstein College of Medicine New York, NY, USA ; Institute for Aging Research, Diabetes Research and Training Center, Albert Einstein College of Medicine New York, NY, USA
| |
Collapse
|
59
|
Muscle-specific GSK-3β ablation accelerates regeneration of disuse-atrophied skeletal muscle. Biochim Biophys Acta Mol Basis Dis 2014; 1852:490-506. [PMID: 25496993 DOI: 10.1016/j.bbadis.2014.12.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 11/26/2014] [Accepted: 12/03/2014] [Indexed: 01/08/2023]
Abstract
Muscle wasting impairs physical performance, increases mortality and reduces medical intervention efficacy in chronic diseases and cancer. Developing proficient intervention strategies requires improved understanding of the molecular mechanisms governing muscle mass wasting and recovery. Involvement of muscle protein- and myonuclear turnover during recovery from muscle atrophy has received limited attention. The insulin-like growth factor (IGF)-I signaling pathway has been implicated in muscle mass regulation. As glycogen synthase kinase 3 (GSK-3) is inhibited by IGF-I signaling, we hypothesized that muscle-specific GSK-3β deletion facilitates the recovery of disuse-atrophied skeletal muscle. Wild-type mice and mice lacking muscle GSK-3β (MGSK-3β KO) were subjected to a hindlimb suspension model of reversible disuse-induced muscle atrophy and followed during recovery. Indices of muscle mass, protein synthesis and proteolysis, and post-natal myogenesis which contribute to myonuclear accretion, were monitored during the reloading of atrophied muscle. Early muscle mass recovery occurred more rapidly in MGSK-3β KO muscle. Reloading-associated changes in muscle protein turnover were not affected by GSK-3β ablation. However, coherent effects were observed in the extent and kinetics of satellite cell activation, proliferation and myogenic differentiation observed during reloading, suggestive of increased myonuclear accretion in regenerating skeletal muscle lacking GSK-3β. This study demonstrates that muscle mass recovery and post-natal myogenesis from disuse-atrophy are accelerated in the absence of GSK-3β.
Collapse
|
60
|
Mariappan MM, Prasad S, D'Silva K, Cedillo E, Sataranatarajan K, Barnes JL, Choudhury GG, Kasinath BS. Activation of glycogen synthase kinase 3β ameliorates diabetes-induced kidney injury. J Biol Chem 2014; 289:35363-75. [PMID: 25339176 DOI: 10.1074/jbc.m114.587840] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Increase in protein synthesis contributes to kidney hypertrophy and matrix protein accumulation in diabetes. We have previously shown that high glucose-induced matrix protein synthesis is associated with inactivation of glycogen synthase kinase 3β (GSK3β) in renal cells and in the kidneys of diabetic mice. We tested whether activation of GSK3β by sodium nitroprusside (SNP) mitigates kidney injury in diabetes. Studies in kidney-proximal tubular epithelial cells showed that SNP abrogated high glucose-induced laminin increment by stimulating GSK3β and inhibiting Akt, mTORC1, and events in mRNA translation regulated by mTORC1 and ERK. NONOate, an NO donor, also activated GSK3β, indicating that NO may mediate SNP stimulation of GSK3β. SNP administered for 3 weeks to mice with streptozotocin-induced type 1 diabetes ameliorated kidney hypertrophy, accumulation of matrix proteins, and albuminuria without changing blood glucose levels. Signaling studies showed that diabetes caused inactivation of GSK3β by activation of Src, Pyk2, Akt, and ERK; GSK3β inhibition activated mTORC1 and downstream events in mRNA translation in the kidney cortex. These reactions were abrogated by SNP. We conclude that activation of GSK3β by SNP ameliorates kidney injury induced by diabetes.
Collapse
Affiliation(s)
- Meenalakshmi M Mariappan
- From the Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78245 and Medical Service, South Texas Veterans Health Care System, San Antonio, Texas 78229
| | - Sanjay Prasad
- From the Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78245 and
| | - Kristin D'Silva
- From the Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78245 and
| | - Esteban Cedillo
- From the Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78245 and
| | | | - Jeffrey L Barnes
- From the Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78245 and
| | - Goutam Ghosh Choudhury
- From the Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78245 and Medical Service, South Texas Veterans Health Care System, San Antonio, Texas 78229 the Geriatric Research, Education, and Clinical Center and
| | - Balakuntalam S Kasinath
- From the Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78245 and Medical Service, South Texas Veterans Health Care System, San Antonio, Texas 78229
| |
Collapse
|
61
|
Hou Y, Wang Y, Wang Y, Zhong T, Li L, Zhang H, Wang L. Multiple alternative splicing and differential expression pattern of the glycogen synthase kinase-3β (GSK3β) gene in goat (Capra hircus). PLoS One 2014; 9:e109555. [PMID: 25334049 PMCID: PMC4198110 DOI: 10.1371/journal.pone.0109555] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Accepted: 09/06/2014] [Indexed: 12/22/2022] Open
Abstract
Glycogen synthase kinase-3β (GSK3β) has been identified as a key protein kinase involved in several signaling pathways, such as Wnt, IGF-Ι and Hedgehog. However, knowledge regarding GSK3β in the goat is limited. In this study, we cloned and characterized the goat GSK3β gene. Six novel GSK3β transcripts were identified in different tissues and designated as GSK3β1, 2, 3, 4, 5 and 6. RT-PCR was used to further determine whether the six GSK3β transcripts existed in different goat tissues. Bioinformatics analysis revealed that the catalytic domain (S_TKc domain) is missing from GSK3β2 and GSK3β4. GSK3β3 and GSK3β6 do not contain the negative regulatory sites that are controlled by p38 MAPK. Furthermore, qRT-PCR and western blot analysis revealed that all the GSK3β transcripts were expressed at the highest level in the heart, whereas their expression levels in the liver, spleen, kidney, brain, longissimus dorsi muscle and uterus were different. These studies provide useful information for further research on the functions of GSK3β isoforms.
Collapse
Affiliation(s)
- Yuguo Hou
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu, Sichuan, P.R. China
| | - Yilin Wang
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu, Sichuan, P.R. China
| | - Yan Wang
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu, Sichuan, P.R. China
| | - Tao Zhong
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu, Sichuan, P.R. China
| | - Li Li
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu, Sichuan, P.R. China
| | - Hongping Zhang
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu, Sichuan, P.R. China
| | - Linjie Wang
- Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu, Sichuan, P.R. China
- * E-mail:
| |
Collapse
|
62
|
Droppelmann CA, Campos-Melo D, Volkening K, Strong MJ. The emerging role of guanine nucleotide exchange factors in ALS and other neurodegenerative diseases. Front Cell Neurosci 2014; 8:282. [PMID: 25309324 PMCID: PMC4159981 DOI: 10.3389/fncel.2014.00282] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 08/25/2014] [Indexed: 12/11/2022] Open
Abstract
Small GTPases participate in a broad range of cellular processes such as proliferation, differentiation, and migration. The exchange of GDP for GTP resulting in the activation of these GTPases is catalyzed by a group of enzymes called guanine nucleotide exchange factors (GEFs), of which two classes: Dbl-related exchange factors and the more recently described dedicator of cytokinesis proteins family exchange factors. Increasingly, deregulation of normal GEF activity or function has been associated with a broad range of disease states, including neurodegeneration and neurodevelopmental disorders. In this review, we examine this evidence with special emphasis on the novel role of Rho guanine nucleotide exchange factor (RGNEF/p190RhoGEF) in the pathogenesis of amyotrophic lateral sclerosis. RGNEF is the first neurodegeneration-linked GEF that regulates not only RhoA GTPase activation but also functions as an RNA binding protein that directly acts with low molecular weight neurofilament mRNA 3' untranslated region to regulate its stability. This dual role for RGNEF, coupled with the increasing understanding of the key role for GEFs in modulating the GTPase function in cell survival suggests a prominent role for GEFs in mediating a critical balance between cytotoxicity and neuroprotection which, when disturbed, contributes to neuronal loss.
Collapse
Affiliation(s)
- Cristian A Droppelmann
- Molecular Medicine Group, Robarts Research Institute, Western University London, ON, Canada
| | - Danae Campos-Melo
- Molecular Medicine Group, Robarts Research Institute, Western University London, ON, Canada
| | - Kathryn Volkening
- Molecular Medicine Group, Robarts Research Institute, Western University London, ON, Canada ; Department of Clinical Neurological Sciences, Schulich School of Medicine & Dentistry, Western University London, ON, Canada
| | - Michael J Strong
- Molecular Medicine Group, Robarts Research Institute, Western University London, ON, Canada ; Department of Clinical Neurological Sciences, Schulich School of Medicine & Dentistry, Western University London, ON, Canada
| |
Collapse
|
63
|
Wortham NC, Martinez M, Gordiyenko Y, Robinson CV, Proud CG. Analysis of the subunit organization of the eIF2B complex reveals new insights into its structure and regulation. FASEB J 2014; 28:2225-37. [DOI: 10.1096/fj.13-243329] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Noel C. Wortham
- Centre for Biological SciencesUniversity of SouthamptonSouthamptonUK
| | | | | | | | | |
Collapse
|
64
|
Verhees KJP, Pansters NAM, Baarsma HA, Remels AHV, Haegens A, de Theije CC, Schols AMWJ, Gosens R, Langen RCJ. Pharmacological inhibition of GSK-3 in a guinea pig model of LPS-induced pulmonary inflammation: II. Effects on skeletal muscle atrophy. Respir Res 2013; 14:117. [PMID: 24180420 PMCID: PMC4176095 DOI: 10.1186/1465-9921-14-117] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 10/14/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Chronic obstructive pulmonary disease (COPD) is accompanied by pulmonary inflammation and associated with extra-pulmonary manifestations, including skeletal muscle atrophy. Glycogen synthase kinase-3 (GSK-3) has been implicated in the regulation of muscle protein- and myonuclear turnover; two crucial processes that determine muscle mass. In the present study we investigated the effect of the selective GSK-3 inhibitor SB216763 on muscle mass in a guinea pig model of lipopolysaccharide (LPS)-induced pulmonary inflammation-associated muscle atrophy. METHODS Guinea pigs were pretreated with either intranasally instilled SB216763 or corresponding vehicle prior to each LPS/saline challenge twice weekly. Pulmonary inflammation was confirmed and indices of muscle mass were determined after 12 weeks. Additionally, cultured skeletal muscle cells were incubated with tumor necrosis factor α (TNF-α) or glucocorticoids (GCs) to model the systemic effects of pulmonary inflammation on myogenesis, in the presence or absence of GSK-3 inhibitors. RESULTS Repeated LPS instillation induced muscle atrophy based on muscle weight and muscle fiber cross sectional area. Intriguingly, GSK-3 inhibition using SB216763 prevented the LPS-induced muscle mass decreases and myofiber atrophy. Indices of protein turnover signaling were unaltered in guinea pig muscle. Interestingly, inhibition of myogenesis of cultured muscle cells by TNF-α or synthetic GCs was prevented by GSK-3 inhibitors. CONCLUSIONS In a guinea pig model of LPS-induced pulmonary inflammation, GSK-3 inhibition prevents skeletal muscle atrophy without affecting pulmonary inflammation. Resistance to inflammation- or GC-induced impairment of myogenic differentiation, imposed by GSK-3 inhibition, suggests that sustained myogenesis may contribute to muscle mass maintenance despite persistent pulmonary inflammation. Collectively, these results warrant further exploration of GSK-3 as a potential novel drug target to prevent or reverse muscle wasting in COPD.
Collapse
Affiliation(s)
- Koen J P Verhees
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre + (MUMC+), PO box 5800, 6202, AZ Maastricht, The Netherlands.
| | | | | | | | | | | | | | | | | |
Collapse
|
65
|
PI3K signaling mediates diverse regulation of ATF4 expression for the survival of HK-2 cells exposed to cadmium. Arch Toxicol 2013; 88:403-14. [PMID: 24057571 DOI: 10.1007/s00204-013-1129-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 09/11/2013] [Indexed: 02/07/2023]
Abstract
Cadmium exposure causes endoplasmic reticulum (ER) stress and accumulation of activating transcription factor 4 (ATF4), an ER stress marker. To elucidate the role of phosphatidylinositol-3-kinase (PI3K) signaling in this process, we examined the effects of PI3K signaling on cadmium chloride (CdCl2) exposure-induced ATF4 expression in HK-2 human renal proximal tubular cells. ATF4 knockdown by siRNA enhanced CdCl2-induced cellular damage, indicating a cytoprotective function of ATF4. Treatment with LY294002, a PI3K inhibitor, suppressed CdCl2-induced ATF4 expression and Akt phosphorylation at Thr308 with little effect on phosphorylation of eukaryotic translation initiation factor 2 subunit α at Ser51. Activation of PI3K signaling with epidermal growth factor treatment enhanced CdCl2-induced Akt phosphorylation and ATF4 expression. Suppression of CdCl2-induced ATF4 expression by LY294002 treatment was markedly blocked by cycloheximide, a translation inhibitor, but not by MG-132, a proteasome inhibitor, or actinomycin D, a transcription inhibitor. CdCl2 exposure also induced phosphorylation of mammalian target of rapamycin (mTOR) at Ser2448, glycogen synthase kinase-3α (GSK-3α) at Ser21, GSK-3β at Ser9, and 90 kDa ribosomal S6 kinase 2 (RSK2) at Ser227 in HK-2 cells. Treatment with rapamycin, an mTOR inhibitor, MK2206, an Akt inhibitor, and BI-D1870, a RSK inhibitor, partially suppressed CdCl2-induced ATF4 expression. Conversely, SB216763, a GSK-3 inhibitor, markedly inhibited the potency of LY294002 to suppress CdCl2-induced ATF4 expression. These results suggest that PI3K signaling diversely regulates the expression of ATF4 in a translation-dependent manner via downstream molecules, including mTOR, GSK-3α/β, and RSK2, and plays a role in protecting HK-2 cells from cadmium-induced damage.
Collapse
|
66
|
Crisan L, Pacureanu L, Avram S, Bora A, Avram S, Kurunczi L. PLS and shape-based similarity analysis of maleimides--GSK-3 inhibitors. J Enzyme Inhib Med Chem 2013; 29:599-610. [PMID: 24047148 DOI: 10.3109/14756366.2013.833196] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
CONTEXT Glycogen synthase kinase-3 (GSK-3) overactivity was correlated with several pathologies including type 2 diabetes mellitus, Alzheimer's disease, cancer, inflammation, obesity, etc. OBJECTIVE The aim of the current investigation was to model the inhibitory activity of maleimide derivatives--inhibitors of GSK-3, to evaluate the impact of alignment on statistical performances of the Quantitative Structure-Activity Relationship (QSAR) and the effect of the template on shape-similarity--binding affinity relationship. MATERIALS AND METHODS Dragon descriptors were used to generate Projection to Latent Structures (PLS) models in order to identify the structural prerequisites of maleimides to inhibit GSK-3. Additionally, shape/volume structural analysis of binding site interactions was evaluated. RESULTS Reliable statistics R(2)(Y(CUM)) = 0.938/0.920, Q((2)(Y)(CUM)) = 0.866/0.838 for aligned and alignment free QSAR models and significant (Pearson, Kendall and Spearman) correlations between shape/volume similarity and affinities were obtained. DISCUSSION AND CONCLUSIONS The crucial structural features modulating the activity of maleimides include topology, charge, geometry, 2D autocorrelations, 3D-MoRSE as well as shape/volume and molecular flexibility.
Collapse
Affiliation(s)
- Luminita Crisan
- Department of Computational Chemistry, Institute of Chemistry of Romanian Academy , Timisoara , Romania
| | | | | | | | | | | |
Collapse
|
67
|
Gordon BS, Kelleher AR, Kimball SR. Regulation of muscle protein synthesis and the effects of catabolic states. Int J Biochem Cell Biol 2013; 45:2147-57. [PMID: 23769967 DOI: 10.1016/j.biocel.2013.05.039] [Citation(s) in RCA: 148] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 05/29/2013] [Accepted: 05/31/2013] [Indexed: 12/20/2022]
Abstract
Protein synthesis and degradation are dynamically regulated processes that act in concert to control the accretion or loss of muscle mass. The present article focuses on the mechanisms involved in the impairment of protein synthesis that are associated with skeletal muscle atrophy. The vast majority of mechanisms known to regulate protein synthesis involve modulation of the initiation phase of mRNA translation, which comprises a series of reactions that result in the binding of initiator methionyl-tRNAi and mRNA to the 40S ribosomal subunit. The function of the proteins involved in both events has been shown to be repressed under atrophic conditions such as sepsis, cachexia, chronic kidney disease, sarcopenia, and disuse atrophy. The basis for the inhibition of protein synthesis under such conditions is likely to be multifactorial and includes insulin/insulin-like growth factor 1 resistance, pro-inflammatory cytokine expression, malnutrition, corticosteroids, and/or physical inactivity. The present article provides an overview of the existing literature regarding mechanisms and signaling pathways involved in the regulation of mRNA translation as they apply to skeletal muscle wasting, as well as the efficacy of potential clinical interventions such as nutrition and exercise in the maintenance of skeletal muscle protein synthesis under atrophic conditions. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.
Collapse
Affiliation(s)
- Bradley S Gordon
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | | | | |
Collapse
|
68
|
Peng Z, Ji Z, Mei F, Lu M, Ou Y, Cheng X. Lithium inhibits tumorigenic potential of PDA cells through targeting hedgehog-GLI signaling pathway. PLoS One 2013; 8:e61457. [PMID: 23626687 PMCID: PMC3634073 DOI: 10.1371/journal.pone.0061457] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2013] [Accepted: 03/09/2013] [Indexed: 12/31/2022] Open
Abstract
Hedgehog signaling pathway plays a critical role in the initiation and development of pancreatic ductal adenocarcinoma (PDA) and represents an attractive target for PDA treatment. Lithium, a clinical mood stabilizer for mental disorders, potently inhibits the activity of glycogen synthase kinase 3β (GSK3β) that promotes the ubiquitin-dependent proteasome degradation of GLI1, an important downstream component of hedgehog signaling. Herein, we report that lithium inhibits cell proliferation, blocks G1/S cell-cycle progression, induces cell apoptosis and suppresses tumorigenic potential of PDA cells through down-regulation of the expression and activity of GLI1. Moreover, lithium synergistically enhances the anti-cancer effect of gemcitabine. These findings further our knowledge of mechanisms of action for lithium and provide a potentially new therapeutic strategy for PDA through targeting GLI1.
Collapse
Affiliation(s)
- Zhonglu Peng
- State Key Laboratory of Natural Medicines and School of Life Science and Technology, China Pharmaceutical University, Nanjing, China
| | - Zhengyu Ji
- Department of Pharmacology and Toxicology, The University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Fang Mei
- Department of Pharmacology and Toxicology, The University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Meiling Lu
- State Key Laboratory of Natural Medicines and School of Life Science and Technology, China Pharmaceutical University, Nanjing, China
| | - Yu Ou
- State Key Laboratory of Natural Medicines and School of Life Science and Technology, China Pharmaceutical University, Nanjing, China
- * E-mail: (XC); (YO)
| | - Xiaodong Cheng
- Department of Pharmacology and Toxicology, The University of Texas Medical Branch, Galveston, Texas, United States of America
- * E-mail: (XC); (YO)
| |
Collapse
|
69
|
Sanchez-Ripoll Y, Bone HK, Owen T, Guedes AMV, Abranches E, Kumpfmueller B, Spriggs RV, Henrique D, Welham MJ. Glycogen synthase kinase-3 inhibition enhances translation of pluripotency-associated transcription factors to contribute to maintenance of mouse embryonic stem cell self-renewal. PLoS One 2013; 8:e60148. [PMID: 23577087 PMCID: PMC3618116 DOI: 10.1371/journal.pone.0060148] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 02/25/2013] [Indexed: 11/18/2022] Open
Abstract
Maintenance of embryonic stem cell (ESC) self-renewal and pluripotency are controlled by extrinsic factors, molecular signaling pathways and transcriptional regulators. While many of the key players have been studied in depth, how the molecular signals interact with transcription factors of the pluripotency network to regulate their action remains less well understood. Inhibition of glycogen synthase kinase 3 (Gsk-3) has been implicated in the maintenance of mouse ESC pluripotency, although there is contradictory data on its role, with enhancement of cell survival and metabolism, stabilisation of c-Myc and activation of Wnt signalling proposed as potential mechanisms. We have discovered that suppression of Gsk-3 activity leads to enhanced protein levels of key transcriptional regulators of the pluripotency network, notably Nanog, Tbx3 and c-Myc. Protein stability was unchanged following Gsk-3 inhibition, although interestingly, Nanog and Tbx3 proteins were found to have half-lives of 1-3 h, while that of Oct4 protein was longer, at 6 h. We demonstrate that the effects on protein levels seen following inhibition of Gsk-3 are due to both enhanced de novo synthesis of Nanog protein and increases in the proportion of Nanog and Tbx3 RNAs bound to polysomes, findings consistent with Gsk-3 regulating translation of these factors. These effects were not due to changes in regulators of general translation initiation machinery nor mediated via the 5' or 3' UTR sequences of Nanog alone. The data we present provide both new conceptual insight into the mechanisms regulated by Gsk-3 that may contribute to ESC self-renewal and, importantly, establish control of protein translation as an additional mechanism involved in modulation of ESC pluripotency.
Collapse
Affiliation(s)
- Yolanda Sanchez-Ripoll
- Centre for Regenerative Medicine and Department of Pharmacy & Pharmacology, University of Bath, Bath, United Kingdom
| | - Heather K. Bone
- Centre for Regenerative Medicine and Department of Pharmacy & Pharmacology, University of Bath, Bath, United Kingdom
| | - Tom Owen
- Centre for Regenerative Medicine and Department of Pharmacy & Pharmacology, University of Bath, Bath, United Kingdom
| | - Ana M. V. Guedes
- Instituto Medicina Molecular, and Instituto de Histologia e Biologia do Desenvolvimento, Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal
| | - Elsa Abranches
- Instituto Medicina Molecular, and Instituto de Histologia e Biologia do Desenvolvimento, Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal
| | - Benjamin Kumpfmueller
- Centre for Regenerative Medicine and Department of Pharmacy & Pharmacology, University of Bath, Bath, United Kingdom
| | - Ruth V. Spriggs
- Medical Research Centre Toxicology Unit, University of Leicester, Hodgkin Building, Leicester, United Kingdom
| | - Domingos Henrique
- Instituto Medicina Molecular, and Instituto de Histologia e Biologia do Desenvolvimento, Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal
| | - Melanie J. Welham
- Centre for Regenerative Medicine and Department of Pharmacy & Pharmacology, University of Bath, Bath, United Kingdom
| |
Collapse
|
70
|
Edgett BA, Fortner ML, Bonen A, Gurd BJ. Mammalian target of rapamycin pathway is up-regulated by both acute endurance exercise and chronic muscle contraction in rat skeletal muscle. Appl Physiol Nutr Metab 2013; 38:862-9. [PMID: 23855274 DOI: 10.1139/apnm-2012-0405] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study examined changes in the expression of translation initiation regulatory proteins and mRNA following both an acute bout of endurance exercise and chronic muscle contractile activity. Female Sprague Dawley rats ran for 2 h at 15 m·min(-1) followed by an increase in speed of 5 m·min(-1) every 5 min until volitional fatigue. The red gastrocnemius muscle was harvested from nonexercised animals (control; n = 6) and from animals that exercised either immediately after exercise (n = 6) or following 3 h of recovery from exercise (n = 6). Compared with control, ribosomal protein S6 (rpS6) mRNA was elevated (p < 0.05) at both 0 h (+32%) and 3 h (+47%). Both a catalytic subunit of eukaryotic initiation factor 2B (eIF2Bε) (+127%) and mammalian target of rapamycin (mTOR) mRNA (+44%) were increased at 3 h, compared with control. Phosphorylation of mTOR (+40%) and S6 kinase 1 (S6K1) (+266%) were increased immediately after exercise (p < 0.05). Female Sprague Dawley rats also underwent chronic stimulation of the peroneal nerve continuously for 7 days. The red gastrocnemius muscle was removed 24 h after cessation of the stimulation. Chronic muscle stimulation increased (p < 0.05) mTOR protein (+74%), rpS6 (+31%), and eukaryotic initiation factor 2α (+44%, p = 0.069), and this was accompanied by an increase in cytochrome c (+31%). Increased resting phosphorylation was observed for rpS6 (+51%) (p < 0.05) but not for mTOR or eukaryotic initiation factor 4E binding protein 1. These experiments demonstrate that both acute and chronic contractile activity up-regulate the mTOR pathway and mitochondrial content in murine skeletal muscle. This up-regulation of the mTOR pathway may increase translation efficiency and may also represent an important control point in exercise-mediated mitochondrial biogenesis.
Collapse
Affiliation(s)
- Brittany A Edgett
- a School of Kinesiology and Health Studies, Queen's University, Kingston, ON K7L 3N6, Canada
| | | | | | | |
Collapse
|
71
|
Changes in translational control after pro-apoptotic stress. Int J Mol Sci 2012; 14:177-90. [PMID: 23344027 PMCID: PMC3565257 DOI: 10.3390/ijms14010177] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 11/06/2012] [Accepted: 12/10/2012] [Indexed: 01/17/2023] Open
Abstract
In stressed cells, a general decrease in the rate of protein synthesis occurs due to modifications in the activity of translation initiation factors. Compelling data now indicate that these changes also permit a selective post-transcriptional expression of proteins necessary for either cell survival or completion of apoptosis when cells are exposed to severe or prolonged stress. In this review, we summarize the modifications that inhibit the activity of the main canonical translation initiation factors, and the data explaining how certain mRNAs encoding proteins involved in either cell survival or apoptosis can be selectively translated.
Collapse
|
72
|
Ikui AE, Rossio V, Schroeder L, Yoshida S. A yeast GSK-3 kinase Mck1 promotes Cdc6 degradation to inhibit DNA re-replication. PLoS Genet 2012; 8:e1003099. [PMID: 23236290 PMCID: PMC3516531 DOI: 10.1371/journal.pgen.1003099] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 10/01/2012] [Indexed: 11/18/2022] Open
Abstract
Cdc6p is an essential component of the pre-replicative complex (pre-RC), which binds to DNA replication origins to promote initiation of DNA replication. Only once per cell cycle does DNA replication take place. After initiation, the pre-RC components are disassembled in order to prevent re-replication. It has been shown that the N-terminal region of Cdc6p is targeted for degradation after phosphorylation by Cyclin Dependent Kinase (CDK). Here we show that Mck1p, a yeast homologue of GSK-3 kinase, is also required for Cdc6 degradation through a distinct mechanism. Cdc6 is an unstable protein and is accumulated in the nucleus only during G1 and early S-phase in wild-type cells. In mck1 deletion cells, CDC6p is stabilized and accumulates in the nucleus even in late S phase and mitosis. Overexpression of Mck1p induces rapid Cdc6p degradation in a manner dependent on Threonine-368, a GSK-3 phosphorylation consensus site, and SCF(CDC4). We show evidence that Mck1p-dependent degradation of Cdc6 is required for prevention of DNA re-replication. Loss of Mck1 activity results in synthetic lethality with other pre-RC mutants previously implicated in re-replication control, and these double mutant strains over-replicate DNA within a single cell cycle. These results suggest that a GSK3 family protein plays an unexpected role in preventing DNA over-replication through Cdc6 degradation in Saccharomyces cerevisiae. We propose that both CDK and Mck1 kinases are required for Cdc6 degradation to ensure a tight control of DNA replication.
Collapse
Affiliation(s)
- Amy E Ikui
- Department of Biology, Brooklyn College, The City University of New York, Brooklyn, New York, United States of America.
| | | | | | | |
Collapse
|
73
|
Abstract
mRNA translation is the most energy consuming process in the cell. In addition, it plays a pivotal role in the control of gene expression and is therefore tightly regulated. In response to various extracellular stimuli and intracellular cues, signaling pathways induce quantitative and qualitative changes in mRNA translation by modulating the phosphorylation status and thus the activity of components of the translational machinery. In this work we focus on the phosphoinositide 3-kinase (PI3K)/AKT and the mitogen-activated protein kinase (MAPK) pathways, as they are strongly implicated in the regulation of translation in homeostasis, whereas their malfunction has been linked to aberrant translation in human diseases, including cancer.
Collapse
Affiliation(s)
- Philippe P Roux
- Institute for Research in Immunology and Cancer, Université de Montréal, Québec, Canada.
| | | |
Collapse
|
74
|
p53 is a major component of the transcriptional and apoptotic program regulated by PI 3-kinase/Akt/GSK3 signaling. Cell Death Dis 2012; 3:e400. [PMID: 23059819 PMCID: PMC3481126 DOI: 10.1038/cddis.2012.138] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The phosphatidylinositol (PI) 3-kinase/Akt signaling pathway has a prominent role in cell survival and proliferation, in part, by regulating gene expression at the transcriptional level. Previous work using global expression profiling identified FOXOs and the E-box-binding transcription factors MITF and USF1 as key targets of PI 3-kinase signaling that lead to the induction of proapoptotic and cell cycle arrest genes in response to inhibition of PI 3-kinase. In this study, we investigated the role of p53 downstream of PI 3-kinase signaling by analyzing the effects of inhibition of PI 3-kinase in Rat-1 cells, which have wild-type p53, compared with Rat-1 cells expressing a dominant-negative p53 mutant. Expression of dominant-negative p53 conferred partial resistance to apoptosis induced by inhibition of PI 3-kinase. Global gene expression profiling combined with computational and experimental analysis of transcription factor binding sites demonstrated that p53, along with FOXO, MITF and USF1, contributed to gene induction in response to PI 3-kinase inhibition. Activation of p53 was mediated by phosphorylation of the histone acetyltransferase Tip60 by glycogen synthase kinase (GSK) 3, leading to activation of p53 by acetylation. Many of the genes targeted by p53 were also targeted by FOXO and E-box-binding transcription factors, indicating that p53 functions coordinately with these factors to regulate gene expression downstream of PI 3-kinase/Akt/GSK3 signaling.
Collapse
|
75
|
Sachse R, Wüstenhagen D, Šamalíková M, Gerrits M, Bier FF, Kubick S. Synthesis of membrane proteins in eukaryotic cell‐free systems. Eng Life Sci 2012. [DOI: 10.1002/elsc.201100235] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Affiliation(s)
- Rita Sachse
- Fraunhofer Institute for Biomedical Engineering (IBMT) Potsdam Germany
| | | | - Mária Šamalíková
- Fraunhofer Institute for Biomedical Engineering (IBMT) Potsdam Germany
| | | | - Frank F. Bier
- Fraunhofer Institute for Biomedical Engineering (IBMT) Potsdam Germany
- University of Potsdam Institute for Biochemistry and Biology Potsdam Germany
| | - Stefan Kubick
- Fraunhofer Institute for Biomedical Engineering (IBMT) Potsdam Germany
| |
Collapse
|
76
|
In silico classification and virtual screening of maleimide derivatives using projection to latent structures discriminant analysis (PLS-DA) and hybrid docking. MONATSHEFTE FUR CHEMIE 2012. [DOI: 10.1007/s00706-012-0816-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
77
|
Grzmil M, Hemmings BA. Translation Regulation as a Therapeutic Target in Cancer: Figure 1. Cancer Res 2012; 72:3891-900. [DOI: 10.1158/0008-5472.can-12-0026] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
78
|
Kelly GM, Buckley DA, Kiely PA, Adams DR, O'Connor R. Serine phosphorylation of the insulin-like growth factor I (IGF-1) receptor C-terminal tail restrains kinase activity and cell growth. J Biol Chem 2012; 287:28180-94. [PMID: 22685298 DOI: 10.1074/jbc.m112.385757] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Insulin-like growth factor I receptor (IGF-1R) signaling is essential for cell, organ, and animal growth. The C-terminal tail of the IGF-1R exhibits regulatory function, but the mechanism is unknown. Here, we show that mutation of Ser-1248 (S1248A) enhances IGF-1R in vitro kinase activity, autophosphorylation, Akt/mammalian target of rapamycin activity, and cell growth. Ser-1248 phosphorylation is mediated by GSK-3β in a mechanism that involves a priming phosphorylation on Ser-1252. GSK-3β knock-out cells exhibit reduced IGF-1R cell surface expression, enhanced IGF-1R kinase activity, and signaling. Examination of crystallographic structures of the IGF-1R kinase domain revealed that the (1248)SFYYS(1252) motif adopts a conformation tightly packed against the kinase C-lobe when Ser-1248 is in the unphosphorylated state that favors kinase activity. S1248A mutation is predicted to lock the motif in this position. In contrast, phosphorylation of Ser-1248 will drive profound structural transition of the sequence, critically affecting connection of the C terminus as well as exposing potential protein docking sites. Decreased kinase activity of a phosphomimetic S1248E mutant and enhanced kinase activity in mutants of its predicted target residue Lys-1081 support this auto-inhibitory model. Thus, the SFYYS motif controls the organization of the IGF-1R C terminus relative to the kinase domain. Its phosphorylation by GSK-3β restrains kinase activity and regulates receptor trafficking and signaling.
Collapse
Affiliation(s)
- Geraldine M Kelly
- Cell Biology Laboratory, Department of Biochemistry, BioSciences Institute, University College Cork, Cork, Ireland
| | | | | | | | | |
Collapse
|
79
|
Mitotic and mitogenic Wnt signalling. EMBO J 2012; 31:2705-13. [PMID: 22617425 DOI: 10.1038/emboj.2012.124] [Citation(s) in RCA: 231] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 04/02/2012] [Indexed: 11/08/2022] Open
Abstract
Canonical Wnt signalling plays an important role in development, tissue homeostasis, and cancer. At the cellular level, canonical Wnt signalling acts by regulating cell fate, cell growth, and cell proliferation. With regard to proliferation, there is increasing evidence for a complex interaction between canonical Wnt signalling and the cell cycle. Mitogenic Wnt signalling regulates cell proliferation by promoting G1 phase. In mitosis, components of the Wnt signalling cascade function directly in spindle formation. Moreover, Wnt signalling is strongly activated in mitosis, suggesting that 'mitotic Wnt signalling' plays an important role to orchestrate a cell division program. Here, we review the complex interplay between Wnt signalling and the cell cycle.
Collapse
|
80
|
Abstract
Muscle plasticity is defined as the ability of a given muscle to alter its structural and functional properties in accordance with the environmental conditions imposed on it. As such, respiratory muscle is in a constant state of remodeling, and the basis of muscle's plasticity is its ability to change protein expression and resultant protein balance in response to varying environmental conditions. Here, we will describe the changes of respiratory muscle imposed by extrinsic changes in mechanical load, activity, and innervation. Although there is a large body of literature on the structural and functional plasticity of respiratory muscles, we are only beginning to understand the molecular-scale protein changes that contribute to protein balance. We will give an overview of key mechanisms regulating protein synthesis and protein degradation, as well as the complex interactions between them. We suggest future application of a systems biology approach that would develop a mathematical model of protein balance and greatly improve treatments in a variety of clinical settings related to maintaining both muscle mass and optimal contractile function of respiratory muscles.
Collapse
Affiliation(s)
- Heather M Gransee
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | | | | |
Collapse
|
81
|
Signaling mechanisms in the regulation of renal matrix metabolism in diabetes. EXPERIMENTAL DIABETES RESEARCH 2012; 2012:749812. [PMID: 22454628 PMCID: PMC3290898 DOI: 10.1155/2012/749812] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 11/02/2011] [Indexed: 02/06/2023]
Abstract
Renal hypertrophy and accumulation of extracellular matrix proteins are among cardinal manifestations of diabetic nephropathy. TGF beta system has been implicated in the pathogenesis of these manifestations. Among signaling pathways activated in the kidney in diabetes, mTOR- (mammalian target of rapamycin-)regulated pathways are pivotal in orchestrating high glucose-induced production of ECM proteins leading to functional and structural changes in the kidney culminating in adverse outcomes. Understanding signaling pathways that influence individual matrix protein expression could lead to the development of new interventional strategies. This paper will highlight some of the diverse components of the signaling network stimulated by hyperglycemia with an emphasis on extracellular matrix protein metabolism in the kidney in diabetes.
Collapse
|
82
|
Tognon CE, Sorensen PHB. Targeting the insulin-like growth factor 1 receptor (IGF1R) signaling pathway for cancer therapy. Expert Opin Ther Targets 2012; 16:33-48. [PMID: 22239439 DOI: 10.1517/14728222.2011.638626] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
INTRODUCTION The IGF system controls growth, differentiation, and development at the cellular, organ and organismal levels. IGF1 receptor (IGF1R) signaling is dysregulated in many cancers. Numerous clinical trials are currently assessing therapies that inhibit either growth factor binding or IGF1R itself. Therapeutic benefit, often in the form of stable disease, has been reported for many different cancer types. AREAS COVERED Canonical IGF signaling and non-canonical pathways involved in carcinogenesis. Three recent insights into IGF1R signaling, namely hybrid receptor formation with insulin receptor (INSR), insulin receptor substrate 1 nuclear translocation, and evidence for IGF1R/INSR as dependence receptors. Different approaches to targeting IGF1R and mechanisms of acquired resistance. Possible mechanisms by which IGF1R signaling supports carcinogenesis and specific examples in different human tumors. EXPERT OPINION Pre-clinical data justifies IGF1R as a target and early clinical trials have shown modest efficacy in selected tumor types. Future work will focus upon assessing the usefulness or disadvantages of simultaneously targeting the IGF1R and INSR, biomarker development to identify potentially responsive patients, and the use of IGF1R inhibitors in combination therapies or as an adjunct to conventional chemotherapy.
Collapse
Affiliation(s)
- Cristina E Tognon
- British Columbia Cancer Research Centre , Department of Molecular Oncology, Vancouver, British Columbia, Canada
| | | |
Collapse
|
83
|
Toll-like receptor activation suppresses ER stress factor CHOP and translation inhibition through activation of eIF2B. Nat Cell Biol 2012; 14:192-200. [PMID: 22231169 PMCID: PMC3271190 DOI: 10.1038/ncb2408] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 11/23/2011] [Indexed: 12/17/2022]
Abstract
Activation of toll-like receptors (TLRs) induces the endoplasmic reticulum (ER) Unfolded Protein Response (UPR) to accommodate essential protein translation1,2. However, despite increased p-eIF2α, a TLR-TRIF-dependent pathway assures that the cells avoid CHOP induction, apoptosis, and translational suppression of critical proteins3. Because p-eIF2α decreases the functional interaction of eIF2 with eIF2B, a guanine nucleotide exchange factor (GEF), we explored the hypothesis that TLR-TRIF signaling activates eIF2B-GEF activity to counteract the effects of p-eIF2α. We now show that TLR-TRIF signaling activates eIF2B-GEF through PP2A-mediated Ser-dephosphorylation of the eIF2B ε-subunit. PP2A itself is activated by decreased Src-family-kinase-induced Tyr-phosphorylation of its catalytic subunit. Each of these processes are required for TLR-TRIF-mediated CHOP suppression in ER-stressed cells in vitro and in vivo. Thus, in the setting of prolonged, physiologic ER stress, a unique TLR-TRIF-dependent translational control pathway enables cells to carry out essential protein synthesis and avoid CHOP-induced apoptosis while still benefitting from the protective arms of the UPR.
Collapse
|
84
|
Abstract
Airway smooth muscle has classically been of interest for its contractile response linked to bronchoconstriction. However, terminally differentiated smooth muscle cells are phenotypically plastic and have multifunctional capacity for proliferation, cellular hypertrophy, migration, and the synthesis of extracellular matrix and inflammatory mediators. These latter properties of airway smooth muscle are important in airway remodeling which is a structural alteration that compounds the impact of contractile responses on limiting airway conductance. In this overview, we describe the important signaling components and the functional evidence supporting a view of smooth muscle cells at the core of fibroproliferative remodeling of hollow organs. Signal transduction components and events are summarized that control the basic cellular processes of proliferation, cell survival, apoptosis, and cellular migration. We delineate known intracellular control mechanisms and suggest future areas of interest to pursue to more fully understand factors that regulate normal myocyte function and airway remodeling in obstructive lung diseases.
Collapse
Affiliation(s)
- William T Gerthoffer
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA.
| | | | | | | | | |
Collapse
|
85
|
Kaidanovich-Beilin O, Woodgett JR. GSK-3: Functional Insights from Cell Biology and Animal Models. Front Mol Neurosci 2011; 4:40. [PMID: 22110425 PMCID: PMC3217193 DOI: 10.3389/fnmol.2011.00040] [Citation(s) in RCA: 365] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 10/23/2011] [Indexed: 12/13/2022] Open
Abstract
Glycogen synthase kinase-3 (GSK-3) is a widely expressed and highly conserved serine/threonine protein kinase encoded in mammals by two genes that generate two related proteins: GSK-3α and GSK-3β. GSK-3 is active in cells under resting conditions and is primarily regulated through inhibition or diversion of its activity. While GSK-3 is one of the few protein kinases that can be inactivated by phosphorylation, the mechanisms of GSK-3 regulation are more varied and not fully understood. Precise control appears to be achieved by a combination of phosphorylation, localization, and sequestration by a number of GSK-3-binding proteins. GSK-3 lies downstream of several major signaling pathways including the phosphatidylinositol 3′ kinase pathway, the Wnt pathway, Hedgehog signaling and Notch. Specific pools of GSK-3, which differ in intracellular localization, binding partner affinity, and relative amount are differentially sensitized to several distinct signaling pathways and these sequestration mechanisms contribute to pathway insulation and signal specificity. Dysregulation of signaling pathways involving GSK-3 is associated with the pathogenesis of numerous neurological and psychiatric disorders and there are data suggesting GSK-3 isoform-selective roles in several of these. Here, we review the current knowledge of GSK-3 regulation and targets and discuss the various animal models that have been employed to dissect the functions of GSK-3 in brain development and function through the use of conventional or conditional knockout mice as well as transgenic mice. These studies have revealed fundamental roles for these protein kinases in memory, behavior, and neuronal fate determination and provide insights into possible therapeutic interventions.
Collapse
|
86
|
Verhees KJP, Schols AMWJ, Kelders MCJM, Op den Kamp CMH, van der Velden JLJ, Langen RCJ. Glycogen synthase kinase-3β is required for the induction of skeletal muscle atrophy. Am J Physiol Cell Physiol 2011; 301:C995-C1007. [DOI: 10.1152/ajpcell.00520.2010] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Skeletal muscle atrophy commonly occurs in acute and chronic disease. The expression of the muscle-specific E3 ligases atrogin-1 (MAFbx) and muscle RING finger 1 (MuRF1) is induced by atrophy stimuli such as glucocorticoids or absence of IGF-I/insulin and subsequent Akt signaling. We investigated whether glycogen synthase kinase-3β (GSK-3β), a downstream molecule in IGF-I/Akt signaling, is required for basal and atrophy stimulus-induced expression of atrogin-1 and MuRF1, and myofibrillar protein loss in C2C12 skeletal myotubes. Abrogation of basal IGF-I signaling, using LY294002, resulted in a prominent induction of atrogin-1 and MuRF1 mRNA and was accompanied by a loss of myosin heavy chain fast (MyHC-f) and myosin light chains 1 (MyLC-1) and -3 (MyLC-3). The synthetic glucocorticoid dexamethasone (Dex) also induced the expression of both atrogenes and likewise resulted in the loss of myosin protein abundance. Genetic ablation of GSK-3β using small interfering RNA resulted in specific sparing of MyHC-f, MyLC-1, and MyLC-3 protein levels after Dex treatment or impaired IGF-I/Akt signaling. Interestingly, loss of endogenous GSK-3β suppressed both basal and atrophy stimulus-induced atrogin-1 and MuRF1 expression, whereas pharmacological GSK-3β inhibition, using CHIR99021 or LiCl, only reduced atrogin-1 mRNA levels in response to LY294002 or Dex. In conclusion, our data reveal that myotube atrophy and myofibrillar protein loss are GSK-3β dependent, and demonstrate for the first time that basal and atrophy stimulus-induced atrogin-1 mRNA expression requires GSK-3β enzymatic activity, whereas MuRF1 expression depends solely on the physical presence of GSK-3β.
Collapse
Affiliation(s)
- Koen J. P. Verhees
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
| | - Annemie M. W. J. Schols
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
| | - Marco C. J. M. Kelders
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
| | - Céline M. H. Op den Kamp
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
| | - Jos L. J. van der Velden
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
| | - Ramon C. J. Langen
- Department of Respiratory Medicine, School for Nutrition, Toxicology and Metabolism (NUTRIM), Maastricht University Medical Centre (MUMC+), Maastricht, the Netherlands
| |
Collapse
|
87
|
Sussman MA, Völkers M, Fischer K, Bailey B, Cottage CT, Din S, Gude N, Avitabile D, Alvarez R, Sundararaman B, Quijada P, Mason M, Konstandin MH, Malhowski A, Cheng Z, Khan M, McGregor M. Myocardial AKT: the omnipresent nexus. Physiol Rev 2011; 91:1023-70. [PMID: 21742795 PMCID: PMC3674828 DOI: 10.1152/physrev.00024.2010] [Citation(s) in RCA: 180] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
One of the greatest examples of integrated signal transduction is revealed by examination of effects mediated by AKT kinase in myocardial biology. Positioned at the intersection of multiple afferent and efferent signals, AKT exemplifies a molecular sensing node that coordinates dynamic responses of the cell in literally every aspect of biological responses. The balanced and nuanced nature of homeostatic signaling is particularly essential within the myocardial context, where regulation of survival, energy production, contractility, and response to pathological stress all flow through the nexus of AKT activation or repression. Equally important, the loss of regulated AKT activity is primarily the cause or consequence of pathological conditions leading to remodeling of the heart and eventual decompensation. This review presents an overview compendium of the complex world of myocardial AKT biology gleaned from more than a decade of research. Summarization of the widespread influence that AKT exerts upon myocardial responses leaves no doubt that the participation of AKT in molecular signaling will need to be reckoned with as a seemingly omnipresent regulator of myocardial molecular biological responses.
Collapse
Affiliation(s)
- Mark A Sussman
- Department of Biology, San Diego State University, SDSU Heart Institute, San Diego, California 92182, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
88
|
Mascher H, Ekblom B, Rooyackers O, Blomstrand E. Enhanced rates of muscle protein synthesis and elevated mTOR signalling following endurance exercise in human subjects. Acta Physiol (Oxf) 2011; 202:175-84. [PMID: 21385328 DOI: 10.1111/j.1748-1716.2011.02274.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
AIM The major aim of this study was to determine the fractional rate of protein synthesis (FSR) during the early period of recovery after intensive aerobic exercise in the absence of nutritional supplementation. METHODS Sixteen male subjects performed one-legged cycling exercise for 1 h at approx. 65-70% of their one-legged maximal oxygen uptake. Using the stable isotope technique, the FSR in the vastus lateralis of both legs were determined during two periods, 0-90 min (n = 8) and 90-180 min (n = 8) after exercise. Biopsies were taken from both exercising and resting muscle before exercise, immediately after and following 90 or 180 min of recovery. RESULTS During the initial 90 min of recovery, FSR in the exercising muscle tended to be higher than in the resting muscle (1.57 ± 0.12 vs. 1.44 ± 0.07% 24 h(-1); P = 0.1) and was significantly higher during the period 90-180 min after exercise (1.74 ± 0.14 vs. 1.43 ± 0.12% 24 h(-1) ; P < 0.05). Exercise induced a 60% increase (P < 0.05) in phosphorylation of mTOR and a fivefold increase (P < 0.05) in Thr(389) phosphorylation of p70S6 kinase as well as a 30% reduction (P < 0.05) in phosphorylation of eEF2. Phosphorylation of AMP-activated protein kinase was enhanced by 40% (P < 0.05) after exercise, but no significant effect on phosphorylation of Akt, or eIF2Bε was observed immediately after exercise. CONCLUSION These findings indicate that during the first 3 h of recovery after intensive endurance exercise FSR gradually increases. Moreover, a stimulation of the mTOR-signalling pathway may be at least partially responsible for this elevated protein synthesis.
Collapse
Affiliation(s)
- H Mascher
- The Åstrand Laboratory, The Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | | | | | | |
Collapse
|
89
|
Sutherland C. What Are the bona fide GSK3 Substrates? Int J Alzheimers Dis 2011; 2011:505607. [PMID: 21629754 PMCID: PMC3100594 DOI: 10.4061/2011/505607] [Citation(s) in RCA: 203] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Accepted: 03/09/2011] [Indexed: 01/07/2023] Open
Abstract
Nearly 100 proteins are proposed to be substrates for GSK3, suggesting that this enzyme is a fundamental regulator of almost every process in the cell, in every tissue in the body. However, it is not certain how many of these proposed substrates are regulated by GSK3 in vivo. Clearly, the identification of the physiological functions of GSK3 will be greatly aided by the identification of its bona fide substrates, and the development of GSK3 as a therapeutic target will be highly influenced by this range of actions, hence the need to accurately establish true GSK3 substrates in cells. In this paper the evidence that proposed GSK3 substrates are likely to be physiological targets is assessed, highlighting the key cellular processes that could be modulated by GSK3 activity and inhibition.
Collapse
Affiliation(s)
- Calum Sutherland
- Biomedical Research Institute, University of Dundee, Dundee DD1 9SY, UK
| |
Collapse
|
90
|
Sklepkiewicz P, Schermuly RT, Tian X, Ghofrani HA, Weissmann N, Sedding D, Kashour T, Seeger W, Grimminger F, Pullamsetti SS. Glycogen synthase kinase 3beta contributes to proliferation of arterial smooth muscle cells in pulmonary hypertension. PLoS One 2011; 6:e18883. [PMID: 21533110 PMCID: PMC3078925 DOI: 10.1371/journal.pone.0018883] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 03/24/2011] [Indexed: 01/17/2023] Open
Abstract
Rationale Pulmonary arterial hypertension (PAH) is a rare progressive pulmonary vascular disorder associated with vascular remodeling and right heart failure. Vascular remodeling involves numerous signaling cascades governing pulmonary arterial smooth muscle cell (PASMC) proliferation, migration and differentiation. Glycogen synthase kinase 3beta (GSK3ß) is a serine/threonine kinase and can act as a downstream regulatory switch for numerous signaling pathways. Hence, we hypothesized that GSK3ß plays a crucial role in pulmonary vascular remodeling. Methods All experiments were done with lung tissue or isolated PASMCs in a well-established monocrotaline (MCT)-induced PAH rat model. The mRNA expression of Wnt ligands (Wnt1, Wnt3a, Wnt5a), upstream Wnt signaling regulator genes (Frizzled Receptors 1, 2 and secreted Frizzled related protein sFRP-1) and canonical Wnt intracellular effectors (GSK3ß, Axin1) were assessed by real-time polymerase chain reaction and protein levels of GSK3ß, phospho-GSK3ß (ser 9) by western blotting and localization by immunohistochemistry. The role of GSK3ß in PASMCs proliferation was assessed by overexpression of wild-type GSK3ß (WT) and constitutively active GSK3ß S9A by [3H]-thymidine incorporation assay. Results Increased levels of total and phosphorylated GSK3ß (inhibitory phosphorylation) were observed in lungs and PASMCs isolated from MCT-induced PAH rats compared to controls. Further, stimulation of MCT-PASMCs with growth factors induced GSK3ß inactivation. Most importantly, treatment with the PDGFR inhibitor, Imatinib, attenuated PDGF-BB and FCS induced GSK3ß phosphorylation. Increased expression of GSK3ß observed in lungs and PASMC isolated from MCT-induced PAH rats was confirmed to be clinically relevant as the same observation was identified in human iPAH lung explants. Overexpression of GSK3ß significantly increased MCT-PASMCs proliferation by regulating ERK phosphorylation. Constitutive activation of GSK3ß (GSK3ß S9A, 9th serine replaced to alanine) inhibited MCT-PASMCs proliferation by decreasing ERK phosphorylation. Conclusion This study supports a central role for GSK3ß in vascular remodeling processes and suggests a novel therapeutic opportunity for the treatment of PAH.
Collapse
MESH Headings
- Animals
- Arteries/enzymology
- Arteries/pathology
- Base Sequence
- Blotting, Western
- Cell Proliferation
- Cells, Cultured
- Cloning, Molecular
- DNA Primers
- Disease Models, Animal
- Glycogen Synthase Kinase 3/genetics
- Glycogen Synthase Kinase 3/metabolism
- Glycogen Synthase Kinase 3 beta
- Humans
- Hypertension, Pulmonary/enzymology
- Hypertension, Pulmonary/pathology
- Immunohistochemistry
- Male
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/pathology
- Mutagenesis
- Phosphorylation
- Polymerase Chain Reaction
- Rats
- Wnt Proteins/metabolism
Collapse
Affiliation(s)
| | - Ralph Theo Schermuly
- Medical Clinic II/V, University Hospital, Giessen, Germany
- Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Xia Tian
- Medical Clinic II/V, University Hospital, Giessen, Germany
| | | | | | | | | | - Werner Seeger
- Medical Clinic II/V, University Hospital, Giessen, Germany
- Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
| | | | - Soni Savai Pullamsetti
- Medical Clinic II/V, University Hospital, Giessen, Germany
- Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
- * E-mail:
| |
Collapse
|
91
|
Ma L, Brown M, Kogut P, Serban K, Li X, McConville J, Chen B, Bentley JK, Hershenson MB, Dulin N, Solway J, Camoretti-Mercado B. Akt activation induces hypertrophy without contractile phenotypic maturation in airway smooth muscle. Am J Physiol Lung Cell Mol Physiol 2011; 300:L701-9. [PMID: 21378028 DOI: 10.1152/ajplung.00119.2009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Airway smooth muscle (ASM) hypertrophy is a cardinal feature of severe asthma, but the underlying molecular mechanisms remain uncertain. Forced protein kinase B/Akt 1 activation is known to induce myocyte hypertrophy in other muscle types, and, since a number of mediators present in asthmatic airways can activate Akt signaling, we hypothesized that Akt activation could contribute to ASM hypertrophy in asthma. To test this hypothesis, we evaluated whether Akt activation occurs naturally within airway myocytes in situ, whether Akt1 activation is sufficient to cause hypertrophy of normal airway myocytes, and whether such hypertrophy is accompanied by excessive accumulation of contractile apparatus proteins (contractile phenotype maturation). Immunostains of human airway sections revealed concordant activation of Akt (reflected in Ser(473) phosphorylation) and of its downstream effector p70(S6Kinase) (reflected in Thr(389) phosphorylation) within airway muscle bundles, but there was no phosphorylation of the alternative Akt downstream target glycogen synthase kinase (GSK) 3β. Artificial overexpression of constitutively active Akt1 (by plasmid transduction or lentiviral infection) caused a progressive increase in size and protein content of cultured canine tracheal myocytes and increased p70(S6Kinase) phosphorylation but not GSK3β phosphorylation; however, constitutively active Akt1 did not cause disproportionate overaccumulation of smooth muscle (sm) α-actin and SM22. Furthermore, mRNAs encoding sm-α-actin and SM22 were reduced. These results indicate that forced Akt1 signaling causes hypertrophy of cultured airway myocytes without inducing further contractile phenotypic maturation, possibly because of opposing effects on contractile protein gene transcription and translation, and suggest that natural activation of Akt1 plays a similar role in asthmatic ASM.
Collapse
Affiliation(s)
- Lan Ma
- Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
92
|
Tuckow AP, Jefferson SJ, Kimball SR, Jefferson LS. Simvastatin represses protein synthesis in the muscle-derived C₂C₁₂ cell line with a concomitant reduction in eukaryotic initiation factor 2B expression. Am J Physiol Endocrinol Metab 2011; 300:E564-70. [PMID: 21224482 PMCID: PMC3064004 DOI: 10.1152/ajpendo.00383.2010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Statins are a widely prescribed class of cholesterol lowering drugs whose use is frequently associated with muscle-related ailments. A number of mechanisms have been implicated in statin-induced myotoxicity including alterations in both protein synthesis and protein degradation. The objective of the present study was to explore the mechanism(s) contributing to the statin-induced reduction in protein synthesis in the muscle-derived C₂C₁₂ cell line. Cells were treated with 10 μM simvastatin or vehicle alone for 24 h in 1% serum. Cells exposed to simvastatin exhibited reduced rates of protein synthesis, as evidenced by [(35)S]methionine and [(35)S]cysteine incorporation into protein. The reduction in protein synthesis occurred with a concomitant decrease in expression and activity of eukaryotic initiation factor 2B (eIF2B), a regulated and rate-controlling guanine nucleotide exchange factor known to affect global rates of protein synthesis. The reductions in protein synthesis and eIF2B expression were prevented by coincubation with mevalonate. Simvastatin treatment also resulted in a proteasome-sensitive reduction in the protein expression of all the subunits of the eIF2B heteropentameric complex. Finally, increased phosphorylation of the catalytic ε-subunit at Ser(535) was observed, an event consistent with an observed reduction in eIF2B activity. These results suggest that repression of eIF2B expression and activity may contribute, at least in part, to the statin-induced reduction in protein synthesis.
Collapse
Affiliation(s)
- Alexander P Tuckow
- Dept. of Cellular & Molecular Physiology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | | | | | | |
Collapse
|
93
|
Noël A, Barrier L, Rinaldi F, Hubert C, Fauconneau B, Ingrand S. Lithium chloride and staurosporine potentiate the accumulation of phosphorylated glycogen synthase kinase 3β/Tyr216, resulting in glycogen synthase kinase 3β activation in SH-SY5Y human neuroblastoma cell lines. J Neurosci Res 2011; 89:755-63. [PMID: 21360572 DOI: 10.1002/jnr.22587] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 11/26/2010] [Accepted: 11/29/2010] [Indexed: 12/27/2022]
Abstract
Glycogen synthase kinase 3β (GSK3β) activity is regulated by phosphorylation processes and regulates in turn through phosphorylation several proteins, including eukaryotic initiation factor 2B (eIF2B). Serine 9 phosphorylation of GSK3β (pGSK3βSer9), usually promoted by activation of the PI3K/Akt survival pathway, triggers GSK3β inhibition. By contrast, tyrosine 216 phosphorylation of GSK3β (pGSK3βTyr216) increases under apoptotic conditions, leading to GSK3β activation. Lithium chloride (LiCl) is usually described to increase pGSK3βSer9 through the PI3K/Akt pathway, resulting in GSK3β inhibition. The purpose of this study is to demonstrate that in some cases LiCl is also able to increase pGSK3βTyr216, resulting in GSK3β activation. For this, we used SH-SY5Y cells and primary neuronal cultures and investigated the effects of LiCl on the two phosphorylated forms of GSK3β under staurosporine (STS)-intoxicated conditions. The ratios between the phosphorylated and total forms of GSK3β and eIF2B were determined by Western blotting. Our results revealed that, besides its ability to increase pGSK3βSer9, LiCl is also able to increase pGSK3βTyr216 greatly in STS-intoxicated SH-SY5Y cells but not in STS-intoxicated primary neuronal cultures. This accumulation of both Ser9 and Tyr216 phosphorylation results in GSK3β activation in STS-intoxicated SH-SY5Y cells in spite of the presence of LiCl. These findings indicate that LiCl treatment is not necessarily correlated with GSK3β inhibition even though it generates Ser9 phosphorylation. Consequently, the ratio pGSK3βSer9/pGSK3βTyr216, which takes into account the balance between the two inactive (Ser9) and active (Tyr216) forms of GSK3β, could be more useful for predicting GSK3β inhibition.
Collapse
|
94
|
Leng X, Wu Y, Wang X, Pan Y, Wang J, Li J, Du L, Dai L, Wu X, Proud CG, Jiang Y. Functional analysis of recently identified mutations in eukaryotic translation initiation factor 2Bɛ (eIF2Bɛ) identified in Chinese patients with vanishing white matter disease. J Hum Genet 2011; 56:300-5. [PMID: 21307862 DOI: 10.1038/jhg.2011.9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Vanishing white matter disease (VWM) is the first human hereditary disease known to be caused by defects in initiation of protein synthesis. Gene defects in each of the five subunits of eukaryotic translation initiation factor 2B (eIF2B α-ɛ) are responsible for the disease, although the mechanism of the pathogenesis is not well understood. In our previous study, four novel eIF2Bɛ mutations were found in Chinese patients: p.Asp62Val, p.Cys335Ser, p.Asn376Asp and p.Ser610-Asp613del. Functional analysis was performed on these mutations and the recently reported p.Arg269X. Our data showed that all resulted in a decrease in the guanine nucleotide exchange (GEF) activity of the eIF2B complex. p.Arg269X and p.Ser610-Asp613del mutants displayed the lowest activity, followed by p.Cys335Ser, p.Asn376Asp and p.Asp62Val. p.Arg269X and p.Ser610-Asp613del could not produce stable eIF2Bɛ, leading to almost complete loss-of-function. No evidence was obtained for the three missense mutations in changes in eIF2Bɛ protein level or eIF2BɛSer(540) phosphorylation, and disruption of holocomplex assembly, or binding to eIF2. All patients in our study had the classical phenotype. p.Asp62Val and p.Asn376Asp mutations caused only mildly decreased GEF activity, were probably responsible for relatively mild phenotype in cases of classical VWM.
Collapse
Affiliation(s)
- Xuerong Leng
- Pediatric Department, Peking University First Hospital, Beijing, China
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
95
|
Toth MJ, Ward K, van der Velden J, Miller MS, Vanburen P, Lewinter MM, Ades PA. Chronic heart failure reduces Akt phosphorylation in human skeletal muscle: relationship to muscle size and function. J Appl Physiol (1985) 2010; 110:892-900. [PMID: 21193562 DOI: 10.1152/japplphysiol.00545.2010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Patients with chronic heart failure (HF) frequently lose muscle mass and function during the course of the disease. A reduction in anabolic stimuli to the muscle has been put forth as a potential mechanism underlying these alterations. The present study examined the hypothesis that skeletal muscle tissue from HF patients would show reduced IGF-1 expression and phosphorylation of signaling molecules downstream of receptor activation. To isolate the unique effect of HF on these variables, we limited the confounding effects of muscle disuse and/or acute disease exacerbation by recruiting controls (n = 11) with similar physical activity levels as HF patients (n = 11) and by testing patients at least 6 mo following any bouts of disease exacerbation/hospitalization. IGF-1 expression in skeletal muscle was similar between patients and controls. Despite this, HF patients were characterized by reduced levels of phospho-Akt/Akt (S473; -43%; P < 0.05), whereas no differences were found in total Akt protein content or phospho- or total protein content of mammalian target of rapamycin (mTOR; S2448), glycogen synthase kinase-3β (GSK-3β; S9), eukaryotic translation initiation factor 4E binding protein-1 (eIF4E-BP; T37/46), p70 ribosomal S6 kinase (p70 S6K; T389), or eIF2Bε (S540). Reduced phospho-Akt/Akt levels and phospho-mTOR/mTOR were related to decreased skeletal muscle myosin protein content (r = 0.602; P < 0.02) and knee extensor isometric torque (r = 0.550; P < 0.05), respectively. Because patients and controls were similar for age, muscle mass, and physical activity, we ascribe the observed alterations in Akt phosphorylation and its relationship to myosin protein content to the unique effects of the HF syndrome.
Collapse
Affiliation(s)
- Michael J Toth
- Health Science Research Facility, Univ. of Vermont, Burlington, VT 05405, USA
| | | | | | | | | | | | | |
Collapse
|
96
|
Abstract
Recent evidence suggests that glycogen synthase kinase 3 (GSK3) proteins and their upstream and downstream regulators have key roles in many fundamental processes during neurodevelopment. Disruption of GSK3 signalling adversely affects brain development and is associated with several neurodevelopmental disorders. Here, we discuss the mechanisms by which GSK3 activity is regulated in the nervous system and provide an overview of the recent advances in the understanding of how GSK3 signalling controls neurogenesis, neuronal polarization and axon growth during brain development. These recent advances suggest that GSK3 is a crucial node that mediates various cellular processes that are controlled by multiple signalling molecules--for example, disrupted in schizophrenia 1 (DISC1), partitioning defective homologue 3 (PAR3), PAR6 and Wnt proteins--that regulate neurodevelopment.
Collapse
Affiliation(s)
- Eun-Mi Hur
- Department of Orthopaedic Surgery, The Johns Hopkins University School of Medicine, Baltimore, MD 21287
| | - Feng-Quan Zhou
- Department of Orthopaedic Surgery, The Johns Hopkins University School of Medicine, Baltimore, MD 21287
- The Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21287
- Address all correspondence to: Feng-Quan Zhou, Ph.D., 215 Ross Research Building, 720 Rutland Ave, Baltimore, MD 21287. (Phone: 443-2875649, Fax: 410-5026414, )
| |
Collapse
|
97
|
Tuckow AP, Vary TC, Kimball SR, Jefferson LS. Ectopic expression of eIF2Bepsilon in rat skeletal muscle rescues the sepsis-induced reduction in guanine nucleotide exchange activity and protein synthesis. Am J Physiol Endocrinol Metab 2010; 299:E241-8. [PMID: 20484009 PMCID: PMC2928514 DOI: 10.1152/ajpendo.00151.2010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Eukaryotic initiation factor 2B (eIF2B) is a guanine nucleotide exchange factor (GEF) whose activity is both tightly regulated and rate-controlling with regard to global rates of protein synthesis. Skeletal muscle eIF2B activity and expression of its catalytic epsilon-subunit (eIF2Bepsilon) have been implicated as potential contributors to the altered rates of protein synthesis in a number of physiological conditions and experimental models. The objective of this study was to directly examine the effects of exogenously expressed eIF2Bepsilon in vivo on GEF activity and protein synthetic rates in rat skeletal muscle. A plasmid encoding FLAG-eIF2Bepsilon was transfected into the tibialis anterior (TA) of one leg, while the contralateral TA received a control plasmid. Ectopic expression of eIF2Bepsilon resulted in increased GEF activity in TA homogenates of healthy rats, demonstrating that the expressed protein was catalytically active. In an effort to restore a deficit in eIF2B activity, we utilized an established model of chronic sepsis in which skeletal muscle eIF2B activity is known to be impaired. Ectopic expression of eIF2Bepsilon in the TA rescued the sepsis-induced deficit in GEF activity and muscle protein synthesis. The results demonstrate that modulation of eIF2Bepsilon expression may be sufficient to correct deficits in skeletal muscle protein synthesis associated with sepsis and other muscle-wasting conditions.
Collapse
Affiliation(s)
- Alexander P Tuckow
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | | | | | | |
Collapse
|
98
|
Deng H, Hershenson MB, Lei J, Anyanwu AC, Pinsky DJ, Bentley JK. Pulmonary artery smooth muscle hypertrophy: roles of glycogen synthase kinase-3beta and p70 ribosomal S6 kinase. Am J Physiol Lung Cell Mol Physiol 2010; 298:L793-803. [PMID: 20190034 DOI: 10.1152/ajplung.00108.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Increased medial arterial thickness is a structural change in pulmonary arterial hypertension (PAH). The role of smooth muscle hypertrophy in this process has not been well studied. Bone morphogenetic proteins (BMPs), transforming growth factor (TGF)-beta1, serotonin (or 5-hydroxytryptamine; 5-HT), and endothelin (ET)-1 have been implicated in PAH pathogenesis. We examined the effect of these mediators on human pulmonary artery smooth muscle cell size, contractile protein expression, and contractile function, as well on the roles of glycogen synthase kinase (GSK)-3beta and p70 ribosomal S6 kinase (p70S6K), two proteins involved in translational control, in this process. Unlike epidermal growth factor, BMP-4, TGF-beta1, 5-HT, and ET-1 each increased smooth muscle cell size, contractile protein expression, fractional cell shortening, and GSK-3beta phosphorylation. GSK-3beta inhibition by lithium or SB-216763 increased cell size, protein synthesis, and contractile protein expression. Expression of a non-phosphorylatable GSK-3beta mutant blocked BMP-4-, TGF-beta1-, 5-HT-, and ET-1-induced cell size enlargement, suggesting that GSK-3beta phosphorylation is required and sufficient for cellular hypertrophy. However, BMP-4, TGF-beta1, 5-HT, and ET-1 stimulation was accompanied by an increase in serum response factor transcriptional activation but not eIF2 phosphorylation, suggesting that GSK-3beta-mediated hypertrophy occurs via transcriptional, not translational, control. Finally, BMP-4, TGF-beta1, 5-HT, and ET-1 treatment induced phosphorylation of p70S6K and ribosomal protein S6, and siRNAs against p70S6K and S6 blocked the hypertrophic response. We conclude that mediators implicated in the pathogenesis of PAH induce pulmonary arterial smooth muscle hypertrophy. Identification of the signaling pathways regulating vascular smooth muscle hypertrophy may define new therapeutic targets for PAH.
Collapse
Affiliation(s)
- Huan Deng
- Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, Michigan 48109-5688, USA
| | | | | | | | | | | |
Collapse
|
99
|
Graham JR, Tullai JW, Cooper GM. GSK-3 represses growth factor-inducible genes by inhibiting NF-kappaB in quiescent cells. J Biol Chem 2009; 285:4472-80. [PMID: 20018891 DOI: 10.1074/jbc.m109.053785] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
GSK-3 is active in the absence of growth factor stimulation and generally acts to induce apoptosis or inhibit cell proliferation. We previously identified a subset of growth factor-inducible genes that can also be induced in quiescent T98G cells solely by inhibition of GSK-3 in the absence of growth factor stimulation. Computational predictions verified by chromatin immunoprecipitation assays identified NF-kappaB binding sites in the upstream regions of 75% of the genes regulated by GSK-3. p50 bound to most of these sites in quiescent cells, and for one-third of the genes, binding of p65 to the predicted sites increased upon inhibition of GSK-3. The functional role of p65 in gene induction following inhibition of GSK-3 was demonstrated by RNA interference experiments. Furthermore, inhibition of GSK-3 in quiescent cells resulted in activation of IkappaB kinase, leading to phosphorylation and degradation of IkappaB alpha and nuclear translocation of p65 and p50. Taken together, these results indicate that the high levels of GSK-3 activity in quiescent cells repress gene expression by negatively regulating NF-kappaB through inhibition of IkappaB kinase. This inhibition of NF-kappaB is consistent with the role of GSK-3 in the induction of apoptosis or cell cycle arrest in cells deprived of growth factors.
Collapse
Affiliation(s)
- Julie R Graham
- Program in Molecular Biology, Cell Biology and Biochemistry, Boston University, Boston, Massachusetts 02215, USA
| | | | | |
Collapse
|
100
|
Nguyen CH, Ming H, Zhao P, Hugendubler L, Gros R, Kimball SR, Chidiac P. Translational control by RGS2. ACTA ACUST UNITED AC 2009; 186:755-65. [PMID: 19736320 PMCID: PMC2742185 DOI: 10.1083/jcb.200811058] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The regulator of G protein signaling (RGS) proteins are a family of guanosine triphosphatase (GTPase)-accelerating proteins. We have discovered a novel function for RGS2 in the control of protein synthesis. RGS2 was found to bind to eIF2Bepsilon (eukaryotic initiation factor 2B epsilon subunit) and inhibit the translation of messenger RNA (mRNA) into new protein. This effect was not observed for other RGS proteins tested. This novel function of RGS2 is distinct from its ability to regulate G protein-mediated signals and maps to a stretch of 37 amino acid residues within its conserved RGS domain. Moreover, RGS2 was capable of interfering with the eIF2-eIF2B GTPase cycle, which is a requisite step for the initiation of mRNA translation. Collectively, this study has identified a novel role for RGS2 in the control of protein synthesis that is independent of its established RGS domain function.
Collapse
Affiliation(s)
- Chau H Nguyen
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario N6A5C1, Canada
| | | | | | | | | | | | | |
Collapse
|