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The Potential Role of R4 Regulators of G Protein Signaling (RGS) Proteins in Type 2 Diabetes Mellitus. Cells 2022; 11:cells11233897. [PMID: 36497154 PMCID: PMC9739376 DOI: 10.3390/cells11233897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/26/2022] [Accepted: 11/30/2022] [Indexed: 12/05/2022] Open
Abstract
Type 2 diabetes mellitus (T2DM) is a complex and heterogeneous disease that primarily results from impaired insulin secretion or insulin resistance (IR). G protein-coupled receptors (GPCRs) are proposed as therapeutic targets for T2DM. GPCRs transduce signals via the Gα protein, playing an integral role in insulin secretion and IR. The regulators of G protein signaling (RGS) family proteins can bind to Gα proteins and function as GTPase-activating proteins (GAP) to accelerate GTP hydrolysis, thereby terminating Gα protein signaling. Thus, RGS proteins determine the size and duration of cellular responses to GPCR stimulation. RGSs are becoming popular targeting sites for modulating the signaling of GPCRs and related diseases. The R4 subfamily is the largest RGS family. This review will summarize the research progress on the mechanisms of R4 RGS subfamily proteins in insulin secretion and insulin resistance and analyze their potential value in the treatment of T2DM.
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Layeghi-Ghalehsoukhteh S, Pal Choudhuri S, Ocal O, Zolghadri Y, Pashkov V, Niederstrasser H, Posner BA, Kantheti HS, Azevedo-Pouly AC, Huang H, Girard L, MacDonald RJ, Brekken RA, Wilkie TM. Concerted cell and in vivo screen for pancreatic ductal adenocarcinoma (PDA) chemotherapeutics. Sci Rep 2020; 10:20662. [PMID: 33244070 PMCID: PMC7693321 DOI: 10.1038/s41598-020-77373-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 10/23/2020] [Indexed: 12/22/2022] Open
Abstract
PDA is a major cause of US cancer-related deaths. Oncogenic Kras presents in 90% of human PDAs. Kras mutations occur early in pre-neoplastic lesions but are insufficient to cause PDA. Other contributing factors early in disease progression include chronic pancreatitis, alterations in epigenetic regulators, and tumor suppressor gene mutation. GPCRs activate heterotrimeric G-proteins that stimulate intracellular calcium and oncogenic Kras signaling, thereby promoting pancreatitis and progression to PDA. By contrast, Rgs proteins inhibit Gi/q-coupled GPCRs to negatively regulate PDA progression. Rgs16::GFP is expressed in response to caerulein-induced acinar cell dedifferentiation, early neoplasia, and throughout PDA progression. In genetically engineered mouse models of PDA, Rgs16::GFP is useful for pre-clinical rapid in vivo validation of novel chemotherapeutics targeting early lesions in patients following successful resection or at high risk for progressing to PDA. Cultured primary PDA cells express Rgs16::GFP in response to cytotoxic drugs. A histone deacetylase inhibitor, TSA, stimulated Rgs16::GFP expression in PDA primary cells, potentiated gemcitabine and JQ1 cytotoxicity in cell culture, and Gem + TSA + JQ1 inhibited tumor initiation and progression in vivo. Here we establish the use of Rgs16::GFP expression for testing drug combinations in cell culture and validation of best candidates in our rapid in vivo screen.
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Affiliation(s)
- Somayeh Layeghi-Ghalehsoukhteh
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX, 75390, USA
- Department of Basic Science, School of Veterinary Medicine, Shiraz University, Shiraz, Iran
| | - Shreoshi Pal Choudhuri
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX, 75390, USA
| | - Ozhan Ocal
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX, 75390, USA
- Department of Molecular Biology and Genetics, Bilkent University, 06800, Ankara, Turkey
| | - Yalda Zolghadri
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX, 75390, USA
- Department of Basic Science, School of Veterinary Medicine, Shiraz University, Shiraz, Iran
| | - Victor Pashkov
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX, 75390, USA
| | - Hanspeter Niederstrasser
- Department of Biochemistry, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - Bruce A Posner
- Department of Biochemistry, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - Havish S Kantheti
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX, 75390, USA
- Cancer Discovery (CanDisc) Group, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX, 75390, USA
| | - Ana C Azevedo-Pouly
- Department of Surgery, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Huocong Huang
- Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Luc Girard
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX, 75390, USA
- Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Raymond J MacDonald
- Department of Molecular Biology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - Rolf A Brekken
- Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Thomas M Wilkie
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX, 75390, USA.
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Xu W, Li H, Wang L, Zhang J, Liu C, Wan X, Liu X, Hu Y, Fang Q, Xiao Y, Bu Q, Wang H, Tian J, Zhao Y, Cen X. Endocannabinoid signaling regulates the reinforcing and psychostimulant effects of ketamine in mice. Nat Commun 2020; 11:5962. [PMID: 33235205 PMCID: PMC7686380 DOI: 10.1038/s41467-020-19780-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 10/27/2020] [Indexed: 02/05/2023] Open
Abstract
The abuse potential of ketamine limits its clinical application, but the precise mechanism remains largely unclear. Here we discovered that ketamine significantly remodels the endocannabinoid-related lipidome and activates 2-arachidonoylglycerol (2-AG) signaling in the dorsal striatum (caudate nucleus and putamen, CPu) of mice. Elevated 2-AG in the CPu is essential for the psychostimulant and reinforcing effects of ketamine, whereas blockade of the cannabinoid CB1 receptor, a predominant 2-AG receptor, attenuates ketamine-induced remodeling of neuronal dendrite structure and neurobehaviors. Ketamine represses the transcription of the monoacylglycerol lipase (MAGL) gene by promoting the expression of PRDM5, a negative transcription factor of the MAGL gene, leading to increased 2-AG production. Genetic overexpression of MAGL or silencing of PRDM5 expression in the CPu robustly reduces 2-AG production and ketamine effects. Collectively, endocannabinoid signaling plays a critical role in mediating the psychostimulant and reinforcing properties of ketamine.
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Affiliation(s)
- Wei Xu
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Hongchun Li
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Liang Wang
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Jiamei Zhang
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Chunqi Liu
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Xuemei Wan
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Xiaochong Liu
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Yiming Hu
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Qiyao Fang
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Yuanyuan Xiao
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Qian Bu
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Hongbo Wang
- Ministry of Education, Collaborative Innovation Center of Advanced Drug Delivery System and Biotech Drugs in Universities of Shandong, Yantai University, 264005, Yantai, People's Republic of China
| | - Jingwei Tian
- Ministry of Education, Collaborative Innovation Center of Advanced Drug Delivery System and Biotech Drugs in Universities of Shandong, Yantai University, 264005, Yantai, People's Republic of China
| | - Yinglan Zhao
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China
| | - Xiaobo Cen
- National Chengdu Center for Safety Evaluation of Drugs, State Key Laboratory of Biotherapy/Collaborative Innovation Center for Biotherapy, West China Hospital, Sichuan University, 610041, Chengdu, People's Republic of China.
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Klepac K, Yang J, Hildebrand S, Pfeifer A. RGS2: A multifunctional signaling hub that balances brown adipose tissue function and differentiation. Mol Metab 2019; 30:173-183. [PMID: 31767169 PMCID: PMC6807268 DOI: 10.1016/j.molmet.2019.09.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 09/12/2019] [Accepted: 09/28/2019] [Indexed: 12/28/2022] Open
Abstract
Objective Recruitment of brown adipose tissue (BAT) is a potential new strategy for increasing energy expenditure (EE) to treat obesity. G protein–coupled receptors (GPCRs) represent promising targets to activate BAT, as they are the major regulators of BAT biological function. To identify new regulators of GPCR signaling in BAT, we studied the role of Regulator of G protein Signaling 2 (RGS2) in brown adipocytes and BAT. Methods We combined pharmacological and genetic tools to investigate the role of RGS2 in BAT in vitro and in vivo. Adipocyte progenitors were isolated from wild-type (WT) and RGS2 knockout (RGS2−/−) BAT and differentiated to brown adipocytes. This approach was complemented with knockdown of RGS2 using lentiviral shRNAs (shRGS2). Adipogenesis was analyzed by Oil Red O staining and by determining the expression of adipogenic and thermogenic markers. Pharmacological modulators and fluorescence staining of F-acting stress fibers were employed to identify the underlying signaling pathways. In vivo, the activity of BAT was assessed by ex vivo lipolysis and by measuring whole-body EE by indirect calorimetry in metabolic cages. Results RGS2 is highly expressed in BAT, and treatment with cGMP—an important enhancer of brown adipocyte differentiation—further increased RGS2 expression. Loss of RGS2 strongly suppressed adipogenesis and the expression of thermogenic genes in brown adipocytes. Mechanistically, we found increased Gq/Rho/Rho kinase (ROCK) signaling in the absence of RGS2. Surprisingly, in vivo analysis revealed elevated BAT activity in RGS2-deficient mice that was caused by enhanced Gs/cAMP signaling. Conclusion Overall, RGS2 regulates two major signaling pathways in BAT: Gq and Gs. On the one hand, RGS2 promotes brown adipogenesis by counteracting the inhibitory action of Gq/Rho/ROCK signaling. On the other hand, RGS2 decreases the activity of BAT through the inhibition of Gs signaling and cAMP production. Thus, RGS2 might represent a stress modulator that protects BAT from overstimulation. RGS2 regulates brown adipose tissue (BAT) by inhibiting two major G protein-coupled receptor (GPCR) pathways – Gq and Gs. Deletion of RGS2 impairs the differentiation of murine brown adipocytes due to elevated Gq/Rho/ROCK signaling. In vivo, RGS2 knock-out mice show an increase in BAT lipolysis and whole-body energy expenditure.
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Affiliation(s)
- Katarina Klepac
- Institute of Pharmacology and Toxicology, University of Bonn, 53127 Bonn, Germany; Research Training Group 1873, University of Bonn, 53127 Bonn, Germany.
| | - JuHee Yang
- Institute of Pharmacology and Toxicology, University of Bonn, 53127 Bonn, Germany; Research Training Group 1873, University of Bonn, 53127 Bonn, Germany
| | - Staffan Hildebrand
- Institute of Pharmacology and Toxicology, University of Bonn, 53127 Bonn, Germany
| | - Alexander Pfeifer
- Institute of Pharmacology and Toxicology, University of Bonn, 53127 Bonn, Germany; Research Training Group 1873, University of Bonn, 53127 Bonn, Germany; PharmaCenter, University of Bonn, 53127 Bonn, Germany.
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Kjalarsdottir L, Tersey SA, Vishwanath M, Chuang JC, Posner BA, Mirmira RG, Repa JJ. 1,25-Dihydroxyvitamin D 3 enhances glucose-stimulated insulin secretion in mouse and human islets: a role for transcriptional regulation of voltage-gated calcium channels by the vitamin D receptor. J Steroid Biochem Mol Biol 2019; 185:17-26. [PMID: 30071248 DOI: 10.1016/j.jsbmb.2018.07.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 06/26/2018] [Accepted: 07/06/2018] [Indexed: 12/12/2022]
Abstract
AIM Vitamin D deficiency in rodents negatively affects glucose-stimulated insulin secretion (GSIS) and human epidemiological studies connect poor vitamin D status with type 2 diabetes. Previous studies performed primarily in rat islets have shown that vitamin D can enhance GSIS. However the molecular pathways linking vitamin D and insulin secretion are currently unknown. Therefore, experiments were undertaken to elucidate the transcriptional role(s) of the vitamin D receptor (VDR) in islet function. METHODS Human and mouse islets were cultured with vehicle or 1,25-dihydroxyvitamin-D3 (1,25D3) and then subjected to GSIS assays. Insulin expression, insulin content, glucose uptake and glucose-stimulated calcium influx were tested. Microarray analysis was performed. In silico analysis was used to identify VDR response elements (VDRE) within target genes and their activity was tested using reporter assays. RESULTS Vdr mRNA is abundant in islets and Vdr expression is glucose-responsive. Preincubation of mouse and human islets with 1,25D3 enhances GSIS and increases glucose-stimulated calcium influx. Microarray analysis identified the R-type voltage-gated calcium channel (VGCC) gene, Cacna1e, which is highly upregulated by 1,25D3 in human and mouse islets and contains a conserved VDRE in intron 7. Results from GSIS assays suggest that 1,25D3 might upregulate a variant of R-type VGCC that is resistant to chemical inhibition. CONCLUSION These results suggest that the role of 1,25D3 in regulating calcium influx acts through the R-Type VGCC during GSIS, thereby modulating the capacity of beta cells to secrete insulin.
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Affiliation(s)
- Lilja Kjalarsdottir
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, United States.
| | - Sarah A Tersey
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, 46202, United States; Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, IN, 46202, United States
| | - Mridula Vishwanath
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, 75390, United States
| | - Jen-Chieh Chuang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, United States
| | - Bruce A Posner
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, 75390, United States
| | - Raghavendra G Mirmira
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, 46202, United States; Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, 46202, United States; Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN, 46202, United States
| | - Joyce J Repa
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, United States; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, 75390, United States.
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Squires KE, Montañez-Miranda C, Pandya RR, Torres MP, Hepler JR. Genetic Analysis of Rare Human Variants of Regulators of G Protein Signaling Proteins and Their Role in Human Physiology and Disease. Pharmacol Rev 2018; 70:446-474. [PMID: 29871944 DOI: 10.1124/pr.117.015354] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Regulators of G protein signaling (RGS) proteins modulate the physiologic actions of many neurotransmitters, hormones, and other signaling molecules. Human RGS proteins comprise a family of 20 canonical proteins that bind directly to G protein-coupled receptors/G protein complexes to limit the lifetime of their signaling events, which regulate all aspects of cell and organ physiology. Genetic variations account for diverse human traits and individual predispositions to disease. RGS proteins contribute to many complex polygenic human traits and pathologies such as hypertension, atherosclerosis, schizophrenia, depression, addiction, cancers, and many others. Recent analysis indicates that most human diseases are due to extremely rare genetic variants. In this study, we summarize physiologic roles for RGS proteins and links to human diseases/traits and report rare variants found within each human RGS protein exome sequence derived from global population studies. Each RGS sequence is analyzed using recently described bioinformatics and proteomic tools for measures of missense tolerance ratio paired with combined annotation-dependent depletion scores, and protein post-translational modification (PTM) alignment cluster analysis. We highlight selected variants within the well-studied RGS domain that likely disrupt RGS protein functions and provide comprehensive variant and PTM data for each RGS protein for future study. We propose that rare variants in functionally sensitive regions of RGS proteins confer profound change-of-function phenotypes that may contribute, in newly appreciated ways, to complex human diseases and/or traits. This information provides investigators with a valuable database to explore variation in RGS protein function, and for targeting RGS proteins as future therapeutic targets.
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Affiliation(s)
- Katherine E Squires
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - Carolina Montañez-Miranda
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - Rushika R Pandya
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - Matthew P Torres
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
| | - John R Hepler
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia (K.E.S., C.M.-M., J.R.H.); and School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia (R.R.P., M.P.T.)
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Kong J, Du C, Jiang L, Jiang W, Deng P, Shao X, Zhang B, Li Y, Zhu R, Zhao Q, Fu D, Gu H, Luo L, Long H, Zhao Y, Cen X. Nicotinamide phosphoribosyltransferase regulates cocaine reward through Sirtuin 1. Exp Neurol 2018; 307:52-61. [DOI: 10.1016/j.expneurol.2018.05.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Revised: 05/05/2018] [Accepted: 05/09/2018] [Indexed: 12/21/2022]
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Kim K, Lee J, Ghil S. The regulators of G protein signaling
RGS
16 and
RGS
18 inhibit protease‐activated receptor 2/Gi/o signaling through distinct interactions with Gα in live cells. FEBS Lett 2018; 592:3126-3138. [DOI: 10.1002/1873-3468.13220] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 07/24/2018] [Accepted: 08/02/2018] [Indexed: 12/12/2022]
Affiliation(s)
- Kiman Kim
- Department of Life Science Kyonggi University Suwon Korea
| | - Jinyong Lee
- Department of Life Science Kyonggi University Suwon Korea
| | - Sungho Ghil
- Department of Life Science Kyonggi University Suwon Korea
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O'Hern PJ, do Carmo G Gonçalves I, Brecht J, López Soto EJ, Simon J, Chapkis N, Lipscombe D, Kye MJ, Hart AC. Decreased microRNA levels lead to deleterious increases in neuronal M2 muscarinic receptors in Spinal Muscular Atrophy models. eLife 2017; 6. [PMID: 28463115 PMCID: PMC5413352 DOI: 10.7554/elife.20752] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 04/01/2017] [Indexed: 12/17/2022] Open
Abstract
Spinal Muscular Atrophy (SMA) is caused by diminished Survival of Motor Neuron (SMN) protein, leading to neuromuscular junction (NMJ) dysfunction and spinal motor neuron (MN) loss. Here, we report that reduced SMN function impacts the action of a pertinent microRNA and its mRNA target in MNs. Loss of the C. elegans SMN ortholog, SMN-1, causes NMJ defects. We found that increased levels of the C. elegans Gemin3 ortholog, MEL-46, ameliorates these defects. Increased MEL-46 levels also restored perturbed microRNA (miR-2) function in smn-1(lf) animals. We determined that miR-2 regulates expression of the C. elegans M2 muscarinic receptor (m2R) ortholog, GAR-2. GAR-2 loss ameliorated smn-1(lf) and mel-46(lf) synaptic defects. In an SMA mouse model, m2R levels were increased and pharmacological inhibition of m2R rescued MN process defects. Collectively, these results suggest decreased SMN leads to defective microRNA function via MEL-46 misregulation, followed by increased m2R expression, and neuronal dysfunction in SMA. DOI:http://dx.doi.org/10.7554/eLife.20752.001 Spinal muscular atrophy is a genetic disease that causes muscles to gradually weaken. In people with the disease, the nerve cells that control the movement of muscles – called motor neurons – deteriorate over time, hindering the person’s mobility and shortening their life expectancy. Spinal muscular atrophy is usually caused by genetic faults affecting a protein called SMN (which is short for “Survival of motor neuron”) and recent research suggested that disrupting this protein alters the function of short pieces of genetic material called microRNAs. However, the precise role that microRNAs play in the disease and their connection to the SMN protein was not clear. MicroRNAs interfere with the production of proteins by disrupting molecules called messenger RNAs, which are temporary strings of genetic code that carry the instructions for making protein. By disrupting messenger RNAs, microRNAs can delay or halt the production of specific proteins. This is an important part of the normal behavior of a cell, but disturbing the activity of microRNAs can lead to an unwanted rise or fall in crucial proteins. O’Hern et al. made use of engineered nematode worms and mice that share genetic features with spinal muscular atrophy patients, including disruption of the gene responsible for producing the SMN protein. These animal models of the disease were used to examine the relationship between decreased SMN levels and microRNAs in motor neurons. The experiments showed that reduced SMN activity affects a specific microRNA, which in turn causes motor neurons to produce more of a protein called m2R. This protein is a receptor for a molecule, called acetylcholine, which motor neurons use to send signals to muscle cells. Increased m2R may be detrimental to motor neurons. As such, O’Hern et al. decreased m2R protein activity to determine whether this could reverse the defects in motor neurons that arise in the animal models of the disease. Indeed, blocking this receptor rescued some of the defects seen in the animal models, supporting the link to spinal muscular atrophy. Several treatments that block m2R are already available to treat other conditions. As such, the next step is to determine whether these existing treatments are able to protect mice models of spinal muscular atrophy against muscle deterioration or increase their lifespan. If successful, this could open new avenues for the development of treatments in people. DOI:http://dx.doi.org/10.7554/eLife.20752.002
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Affiliation(s)
- Patrick J O'Hern
- Department of Neuroscience, Brown University, Providence, United States
| | | | - Johanna Brecht
- Institute of Human Genetics, University of Cologne, Cologne, Germany
| | | | - Jonah Simon
- Department of Neuroscience, Brown University, Providence, United States
| | - Natalie Chapkis
- Department of Neuroscience, Brown University, Providence, United States
| | - Diane Lipscombe
- Department of Neuroscience, Brown University, Providence, United States.,Brown Institute for Brain Science, Providence, United States
| | - Min Jeong Kye
- Institute of Human Genetics, University of Cologne, Cologne, Germany
| | - Anne C Hart
- Department of Neuroscience, Brown University, Providence, United States
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López Soto EJ, Agosti F, Cabral A, Mustafa ER, Damonte VM, Gandini MA, Rodríguez S, Castrogiovanni D, Felix R, Perelló M, Raingo J. Constitutive and ghrelin-dependent GHSR1a activation impairs CaV2.1 and CaV2.2 currents in hypothalamic neurons. ACTA ACUST UNITED AC 2015; 146:205-19. [PMID: 26283199 PMCID: PMC4555474 DOI: 10.1085/jgp.201511383] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 07/13/2015] [Indexed: 12/22/2022]
Abstract
Constitutive and ligand-dependent GHSR1a activity attenuates CaV2 current and hypothalamic GABA release through distinct mechanisms and signaling pathways. The growth hormone secretagogue receptor type 1a (GHSR1a) has the highest known constitutive activity of any G protein–coupled receptor (GPCR). GHSR1a mediates the action of the hormone ghrelin, and its activation increases transcriptional and electrical activity in hypothalamic neurons. Although GHSR1a is present at GABAergic presynaptic terminals, its effect on neurotransmitter release remains unclear. The activities of the voltage-gated calcium channels, CaV2.1 and CaV2.2, which mediate neurotransmitter release at presynaptic terminals, are modulated by many GPCRs. Here, we show that both constitutive and agonist-dependent GHSR1a activity elicit a strong impairment of CaV2.1 and CaV2.2 currents in rat and mouse hypothalamic neurons and in a heterologous expression system. Constitutive GHSR1a activity reduces CaV2 currents by a Gi/o-dependent mechanism that involves persistent reduction in channel density at the plasma membrane, whereas ghrelin-dependent GHSR1a inhibition is reversible and involves altered CaV2 gating via a Gq-dependent pathway. Thus, GHSR1a differentially inhibits CaV2 channels by Gi/o or Gq protein pathways depending on its mode of activation. Moreover, we present evidence suggesting that GHSR1a-mediated inhibition of CaV2 attenuates GABA release in hypothalamic neurons, a mechanism that could contribute to neuronal activation through the disinhibition of postsynaptic neurons.
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Affiliation(s)
- Eduardo Javier López Soto
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Francina Agosti
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Agustina Cabral
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Emilio Roman Mustafa
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Valentina Martínez Damonte
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Maria Alejandra Gandini
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute, 07000 México D.F., México
| | - Silvia Rodríguez
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Daniel Castrogiovanni
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Ricardo Felix
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute, 07000 México D.F., México
| | - Mario Perelló
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
| | - Jesica Raingo
- Laboratory of Electrophysiology and Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE), B1904CMA La Plata, Buenos Aires, Argentina
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Woodard GE, Jardín I, Berna-Erro A, Salido GM, Rosado JA. Regulators of G-protein-signaling proteins: negative modulators of G-protein-coupled receptor signaling. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 317:97-183. [PMID: 26008785 DOI: 10.1016/bs.ircmb.2015.02.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Regulators of G-protein-signaling (RGS) proteins are a category of intracellular proteins that have an inhibitory effect on the intracellular signaling produced by G-protein-coupled receptors (GPCRs). RGS along with RGS-like proteins switch on through direct contact G-alpha subunits providing a variety of intracellular functions through intracellular signaling. RGS proteins have a common RGS domain that binds to G alpha. RGS proteins accelerate GTPase and thus enhance guanosine triphosphate hydrolysis through the alpha subunit of heterotrimeric G proteins. As a result, they inactivate the G protein and quickly turn off GPCR signaling thus terminating the resulting downstream signals. Activity and subcellular localization of RGS proteins can be changed through covalent molecular changes to the enzyme, differential gene splicing, and processing of the protein. Other roles of RGS proteins have shown them to not be solely committed to being inhibitors but behave more as modulators and integrators of signaling. RGS proteins modulate the duration and kinetics of slow calcium oscillations and rapid phototransduction and ion signaling events. In other cases, RGS proteins integrate G proteins with signaling pathways linked to such diverse cellular responses as cell growth and differentiation, cell motility, and intracellular trafficking. Human and animal studies have revealed that RGS proteins play a vital role in physiology and can be ideal targets for diseases such as those related to addiction where receptor signaling seems continuously switched on.
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Affiliation(s)
- Geoffrey E Woodard
- Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, USA; Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, Bethesda, MD, USA
| | - Isaac Jardín
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - A Berna-Erro
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - Gines M Salido
- Department of Physiology, University of Extremadura, Caceres, Spain
| | - Juan A Rosado
- Department of Physiology, University of Extremadura, Caceres, Spain
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Jones RD, Lopez AM, Tong EY, Posey KS, Chuang JC, Repa JJ, Turley SD. Impact of physiological levels of chenodeoxycholic acid supplementation on intestinal and hepatic bile acid and cholesterol metabolism in Cyp7a1-deficient mice. Steroids 2015; 93:87-95. [PMID: 25447797 PMCID: PMC4297738 DOI: 10.1016/j.steroids.2014.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 11/07/2014] [Indexed: 01/07/2023]
Abstract
Mice deficient in cholesterol 7α-hydroxylase (Cyp7a1) have a diminished bile acid pool (BAP) and therefore represent a useful model for investigating the metabolic effects of restoring the pool with a specific BA. Previously we carried out such studies in Cyp7a1(-/-) mice fed physiological levels of cholic acid (CA) and achieved BAP restoration, along with an increased CA enrichment, at a dietary level of just 0.03% (w/w). Here we demonstrate that in Cyp7a1(-/-) mice fed chenodeoxycholic acid (CDCA) at a level of 0.06% (w/w), the BAP was restored to normal size and became substantially enriched with muricholic acid (MCA) (>70%), leaving the combined contribution of CA and CDCA to be <15%. This resulted in a partial to complete reversal of the main changes in cholesterol and BA metabolism associated with Cyp7a1 deficiency such as an elevated rate of intestinal sterol synthesis, an enhanced level of mRNA for Cyp8b1 in the liver, and depressed mRNA levels for Ibabp, Shp and Fgf15 in the distal small intestine. When Cyp7a1(-/-) and matching Cyp7a1(+/+) mice were fed a diet with added cholesterol (0.2%) (w/w), either alone, or also containing CDCA (0.06%) (w/w) or CA (0.03%) (w/w) for 18days, the hepatic total cholesterol concentrations (mg/g) in the Cyp7a1(-/-) mice were 26.9±3.7, 16.4±0.9 and 47.6±1.9, respectively, vs. 4.9±0.4, 5.0±0.7 and 6.4±1.9, respectively in the corresponding Cyp7a1(+/+) controls. These data affirm the importance of using moderate levels of dietary BA supplementation to elicit changes in hepatic cholesterol metabolism through shifts in BAP size and composition.
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Affiliation(s)
- Ryan D Jones
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Adam M Lopez
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Ernest Y Tong
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Kenneth S Posey
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Jen-Chieh Chuang
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Joyce J Repa
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States; Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
| | - Stephen D Turley
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, United States.
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Lührig S, Siamishi I, Tesmer-Wolf M, Zechner U, Engel W, Nolte J. Lrrc34, a novel nucleolar protein, interacts with npm1 and ncl and has an impact on pluripotent stem cells. Stem Cells Dev 2014; 23:2862-74. [PMID: 24991885 PMCID: PMC4236065 DOI: 10.1089/scd.2013.0470] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 07/02/2014] [Indexed: 11/13/2022] Open
Abstract
The gene Lrrc34 (leucine rich repeat containing 34) is highly expressed in pluripotent stem cells and its expression is strongly downregulated upon differentiation. These results let us to suggest a role for Lrrc34 in the regulation and maintenance of pluripotency. Expression analyses revealed that Lrrc34 is predominantly expressed in pluripotent stem cells and has an impact on the expression of known pluripotency genes, such as Oct4. Methylation studies of the Lrrc34 promoter showed a hypomethylation in undifferentiated stem cells and chromatin immunoprecipitation-quantitative polymerase chain reaction analyses of histone modifications revealed an enrichment of activating histone modifications on the Lrrc34 promoter region. Further, we could verify the nucleolus-the place of ribosome biogenesis-as the major subcellular localization of the LRRC34 protein. We have verified the interaction of LRRC34 with two major nucleolar proteins, Nucleophosmin and Nucleolin, by two independent methods, suggesting a role for Lrrc34 in ribosome biogenesis of pluripotent stem cells. In conclusion, LRRC34 is a novel nucleolar protein that is predominantly expressed in pluripotent stem cells. Its altered expression has an impact on pluripotency-regulating genes and it interacts with proteins known to be involved in ribosome biogenesis. Therefore we suggest a role for Lrrc34 in ribosome biogenesis of pluripotent stem cells.
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Affiliation(s)
- Sandra Lührig
- Institute of Human Genetics, University of Göttingen, Göttingen, Germany
| | - Iliana Siamishi
- Institute of Human Genetics, University of Göttingen, Göttingen, Germany
| | | | - Ulrich Zechner
- Institute of Human Genetics, University of Mainz, Mainz, Germany
| | - Wolfgang Engel
- Institute of Human Genetics, University of Göttingen, Göttingen, Germany
| | - Jessica Nolte
- Institute of Human Genetics, University of Göttingen, Göttingen, Germany
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Mundy DI, Lopez AM, Posey KS, Chuang JC, Ramirez CM, Scherer PE, Turley SD. Impact of the loss of caveolin-1 on lung mass and cholesterol metabolism in mice with and without the lysosomal cholesterol transporter, Niemann-Pick type C1. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:995-1002. [PMID: 24747682 DOI: 10.1016/j.bbalip.2014.04.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 04/08/2014] [Accepted: 04/11/2014] [Indexed: 11/17/2022]
Abstract
Caveolin-1 (Cav-1) is a major structural protein in caveolae in the plasma membranes of many cell types, particularly endothelial cells and adipocytes. Loss of Cav-1 function has been implicated in multiple diseases affecting the cardiopulmonary and central nervous systems, as well as in specific aspects of sterol and lipid metabolism in the liver and intestine. Lungs contain an exceptionally high level of Cav-1. Parameters of cholesterol metabolism in the lung were measured, initially in Cav-1-deficient mice (Cav-1(-/-)), and subsequently in Cav-1(-/-) mice that also lacked the lysosomal cholesterol transporter Niemann-Pick C1 (Npc1) (Cav-1(-/-):Npc1(-/-)). In 50-day-old Cav-1(-/-) mice fed a low- or high-cholesterol chow diet, the total cholesterol concentration (mg/g) in the lungs was marginally lower than in the Cav-1(+/+) controls, but due to an expansion in their lung mass exceeding 30%, whole-lung cholesterol content (mg/organ) was moderately elevated. Lung mass (g) in the Cav-1(-/-):Npc1(-/-) mice (0.356±0.022) markedly exceeded that in their Cav-1(+/+):Npc1(+/+) controls (0.137±0.009), as well as in their Cav-1(-/-):Npc1(+/+) (0.191±0.013) and Cav-1(+/+):Npc1(-/-) (0.213±0.022) littermates. The corresponding lung total cholesterol contents (mg/organ) in mice of these genotypes were 6.74±0.17, 0.71±0.05, 0.96±0.05 and 3.12±0.43, respectively, with the extra cholesterol in the Cav-1(-/-):Npc1(-/-) and Cav-1(+/+):Npc1(-/-) mice being nearly all unesterified (UC). The exacerbation of the Npc1 lung phenotype and increase in the UC level in the Cav-1(-/-):Npc1(-/-) mice imply a regulatory role of Cav-1 in pulmonary cholesterol metabolism when lysosomal sterol transport is disrupted.
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Affiliation(s)
- Dorothy I Mundy
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, USA.
| | - Adam M Lopez
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, USA.
| | - Kenneth S Posey
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, USA.
| | - Jen-Chieh Chuang
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, USA.
| | - Charina M Ramirez
- Department of Pediatrics, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, USA.
| | - Philipp E Scherer
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, USA.
| | - Stephen D Turley
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, USA.
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15
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Levay K, Slepak VZ. Regulation of Cop9 signalosome activity by the EF-hand Ca2+-binding protein tescalcin. J Cell Sci 2014; 127:2448-59. [PMID: 24659803 DOI: 10.1242/jcs.139592] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Ca(2+)-binding protein tescalcin is known to be involved in hematopoietic cell differentiation; however, this mechanism is poorly understood. Here, we identify CSN4 (subunit 4 of the COP9 signalosome) as a novel binding partner of tescalcin. The COP9 signalosome (CSN) is a multiprotein complex that is essential for development in all eukaryotes. This interaction is selective, Ca(2+)-dependent and involves the PCI domain of CSN4 subunit. We then investigated tescalcin and CSN activity in human erythroleukemia HEL and promyelocytic leukemia K562 cells and find that phorbol 12-myristate 13-acetate (PMA)-induced differentiation, resulting in the upregulation of tescalcin, coincides with reduced deneddylation of cullin-1 (Cul1) and stabilization of p27(Kip1) - molecular events that are associated with CSN activity. The knockdown of tescalcin led to an increase in Cul1 deneddylation, expression of F-box protein Skp2 and the transcription factor c-Jun, whereas the levels of cell cycle regulators p27(Kip1) and p53 decreased. These effects are consistent with the hypothesis that tescalcin might play a role as a negative regulator of CSN activity towards Cul1 in the process of induced cell differentiation.
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Affiliation(s)
- Konstantin Levay
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Vladlen Z Slepak
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA Neuroscience Program, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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16
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Ruggles KV, Garbarino J, Liu Y, Moon J, Schneider K, Henneberry A, Billheimer J, Millar JS, Marchadier D, Valasek MA, Joblin-Mills A, Gulati S, Munkacsi AB, Repa JJ, Rader D, Sturley SL. A functional, genome-wide evaluation of liposensitive yeast identifies the "ARE2 required for viability" (ARV1) gene product as a major component of eukaryotic fatty acid resistance. J Biol Chem 2013; 289:4417-31. [PMID: 24273168 DOI: 10.1074/jbc.m113.515197] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The toxic subcellular accumulation of lipids predisposes several human metabolic syndromes, including obesity, type 2 diabetes, and some forms of neurodegeneration. To identify pathways that prevent lipid-induced cell death, we performed a genome-wide fatty acid sensitivity screen in Saccharomyces cerevisiae. We identified 167 yeast mutants as sensitive to 0.5 mm palmitoleate, 45% of which define pathways that were conserved in humans. 63 lesions also impacted the status of the lipid droplet; however, this was not correlated to the degree of fatty acid sensitivity. The most liposensitive yeast strain arose due to deletion of the "ARE2 required for viability" (ARV1) gene, encoding an evolutionarily conserved, potential lipid transporter that localizes to the endoplasmic reticulum membrane. Down-regulation of mammalian ARV1 in MIN6 pancreatic β-cells or HEK293 cells resulted in decreased neutral lipid synthesis, increased fatty acid sensitivity, and lipoapoptosis. Conversely, elevated expression of human ARV1 in HEK293 cells or mouse liver significantly increased triglyceride mass and lipid droplet number. The ARV1-induced hepatic triglyceride accumulation was accompanied by up-regulation of DGAT1, a triglyceride synthesis gene, and the fatty acid transporter, CD36. Furthermore, ARV1 was identified as a transcriptional of the protein peroxisome proliferator-activated receptor α (PPARα), a key regulator of lipid homeostasis whose transcriptional targets include DGAT1 and CD36. These results implicate ARV1 as a protective factor in lipotoxic diseases due to modulation of fatty acid metabolism. In conclusion, a lipotoxicity-based genetic screen in a model microorganism has identified 75 human genes that may play key roles in neutral lipid metabolism and disease.
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Progranulin does not bind tumor necrosis factor (TNF) receptors and is not a direct regulator of TNF-dependent signaling or bioactivity in immune or neuronal cells. J Neurosci 2013; 33:9202-13. [PMID: 23699531 DOI: 10.1523/jneurosci.5336-12.2013] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Progranulin (PGRN) is a secreted glycoprotein expressed in neurons and glia that is implicated in neuronal survival on the basis that mutations in the GRN gene causing haploinsufficiency result in a familial form of frontotemporal dementia (FTD). Recently, a direct interaction between PGRN and tumor necrosis factor receptors (TNFR I/II) was reported and proposed to be a mechanism by which PGRN exerts anti-inflammatory activity, raising the possibility that aberrant PGRN-TNFR interactions underlie the molecular basis for neuroinflammation in frontotemporal lobar degeneration pathogenesis. Here, we report that we find no evidence for a direct physical or functional interaction between PGRN and TNFRs. Using coimmunoprecipitation and surface plasmon resonance (SPR) we replicated the interaction between PGRN and sortilin and that between TNF and TNFRI/II, but not the interaction between PGRN and TNFRs. Recombinant PGRN or transfection of a cDNA encoding PGRN did not antagonize TNF-dependent NFκB, Akt, and Erk1/2 pathway activation; inflammatory gene expression; or secretion of inflammatory factors in BV2 microglia and bone marrow-derived macrophages (BMDMs). Moreover, PGRN did not antagonize TNF-induced cytotoxicity on dopaminergic neuroblastoma cells. Last, co-addition or pre-incubation with various N- or C-terminal-tagged recombinant PGRNs did not alter lipopolysaccharide-induced inflammatory gene expression or cytokine secretion in any cell type examined, including BMDMs from Grn+/- or Grn-/- mice. Therefore, the neuroinflammatory phenotype associated with PGRN deficiency in the CNS is not a direct consequence of the loss of TNF antagonism by PGRN, but may be a secondary response by glia to disrupted interactions between PGRN and Sortilin and/or other binding partners yet to be identified.
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18
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Ha Thi HT, Lim HS, Kim J, Kim YM, Kim HY, Hong S. Transcriptional and post-translational regulation of Bim is essential for TGF-β and TNF-α-induced apoptosis of gastric cancer cell. Biochim Biophys Acta Gen Subj 2013; 1830:3584-92. [DOI: 10.1016/j.bbagen.2013.03.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 03/04/2013] [Accepted: 03/07/2013] [Indexed: 12/14/2022]
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19
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Nguyen TA, Frank-Cannon T, Martinez TN, Ruhn KA, Marvin M, Casey B, Treviño I, Hong JJ, Goldberg MS, Tansey MG. Analysis of inflammation-related nigral degeneration and locomotor function in DJ-1(-/-) mice. J Neuroinflammation 2013; 10:50. [PMID: 23622116 PMCID: PMC3769147 DOI: 10.1186/1742-2094-10-50] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2012] [Accepted: 03/26/2013] [Indexed: 11/26/2022] Open
Abstract
Background Complex interactions involving genetic susceptibility and environmental factors are thought to underlie the pathogenesis of Parkinson’s disease (PD). Although the role of inflammatory processes in modulating risk for development of PD has yet to be fully understood, prospective studies suggest that chronic use of NSAIDs reduce the incidence of PD. Loss-of-function mutations in the DJ-1 gene cause a rare form of familial PD with an autosomal recessive pattern of inheritance; however, DJ-1−/− mice do not display nigrostriatal pathway degeneration, suggesting that additional factors such as inflammation may be needed to induce neurodegeneration on the background of DJ-1 gene mutations. Neuroinflammation causes oxidative stress and, based on evidence that DJ-1 plays a protective role against oxidative stress, we investigated whether DJ-1−/− mice display increased vulnerability to inflammation-induced nigral degeneration. Methods We exposed adult wild-type and DJ-1−/− mice to repeated intranasal administration of soluble TNF (inTNF) or repeated intraperitoneal injections of low-dose lipopolysaccharide (LPS) or saline vehicle. We measured locomotor performance using a variety of behavior tasks, striatal dopamine (DA) content by HPLC, DA neuron (TH+ cells) and total neuron (NeuN+ cells) number in the substantia nigra pars compacta and ventral tegmental area by unbiased stereology, number of Iba1-positive microglia, and mRNA levels of inflammatory and oxidative stress genes by quantitative PCR in the midbrain, cortex and isolated peritoneal macrophages of DJ-1−/− and wild-type mice. Results We found that chronic LPS injections induced similar neuroinflammatory responses in the midbrains of DJ-1−/− mice and wild-type mice and neither group developed locomotor deficits or nigral degeneration. inTNF administration did not appear to induce neuroinflammatory responses in LPS-treated wild-type or DJ-1−/− mice. The lack of vulnerability to inflammation-induced nigral degeneration was not due to enhanced anti-oxidant gene responses in the midbrains of DJ-1−/− mice which, in fact, displayed a blunted response relative to that of wild-type mice. Peripheral macrophages from wild-type and DJ-1−/− mice displayed similar basal and LPS-induced inflammatory and oxidative stress markers in vitro. Conclusions Our studies indicate that DJ-1−/− mice do not display increased vulnerability to inflammation-related nigral degeneration in contrast to what has been reported for 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine. We conclude that either DJ-1 does not have a critical role in protecting DA neurons against inflammation-induced oxidative stress and/or there is compensatory gene expression in the midbrain of DJ-1−/− mice that renders them resistant to the cytotoxic effects triggered by chronic peripheral inflammation.
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Affiliation(s)
- Thi A Nguyen
- Department of Physiology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390, USA
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20
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Walker AK, Ibia IE, Zigman JM. Disruption of cue-potentiated feeding in mice with blocked ghrelin signaling. Physiol Behav 2012; 108:34-43. [PMID: 23063723 DOI: 10.1016/j.physbeh.2012.10.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Accepted: 10/04/2012] [Indexed: 12/22/2022]
Abstract
The peptide hormone ghrelin regulates a variety of eating behaviors. Not only does it potently increase intake of freely-available food, but it also shifts food preference toward diets rich in fat, enhances operant responding for food rewards, and induces conditioned place preference for food rewards. Here, we postulated that ghrelin also enables cue-potentiated feeding, in which eating is enhanced upon presentation of a food-conditioned stimulus. To test this hypothesis, a novel cue-potentiated feeding protocol adapted for use in mice was designed and validated, and then the effects of pharmacologic ghrelin receptor (GHSR) antagonism and GHSR transcriptional blockade (as occurs in GHSR-null mice) were assessed. Sated C57BL/6J mice indeed demonstrated cue-potentiated intake of grain-based pellets specifically upon presentation of a positive conditioned stimulus (CS+) but not a negative conditioned stimulus (CS-). Treatment with a GHSR antagonist blocked potentiated feeding in sated C57BL/6J mice in response to the CS+. In contrast, while GHSR-null mice also lacked a potentiation of feeding specifically in response to the CS+, they displayed an enhanced intake of pellets in response to both the positive and negative conditioned stimuli. The pattern of immediate early gene expression within the basolateral amygdala - a brain region previously linked to cue-potentiated feeding - paralleled the observed behavior of these mice, suggesting uncharacteristic activation of the amygdala in response to negative conditioned stimuli in GHSR-null mice as compared to wild-type littermates. Thus, although the observed disruptions in cue-potentiated feeding are different depending upon whether GHSR activity or GHSR expression is blocked, a key role for GHSRs in establishing a specific positive cue-food association has now been established.
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Affiliation(s)
- Angela K Walker
- Department of Internal Medicine (Divisions of Hypothalamic Research and of Endocrinology & Metabolism), The University of Texas Southwestern Medical Center, Dallas, TX 75390-9077, United States
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21
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Jones RD, Taylor AM, Tong EY, Repa JJ. Carboxylesterases are uniquely expressed among tissues and regulated by nuclear hormone receptors in the mouse. Drug Metab Dispos 2012; 41:40-9. [PMID: 23011759 DOI: 10.1124/dmd.112.048397] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Carboxylesterases (CES) are a well recognized, yet incompletely characterized family of proteins that catalyze neutral lipid hydrolysis. Some CES have well-defined roles in xenobiotic clearance, pharmacologic prodrug activation, and narcotic detoxification. In addition, emerging evidence suggests other CES may have roles in lipid metabolism. Humans have six CES genes, whereas mice have 20 Ces genes grouped into five isoenzyme classes. Perhaps due to the high sequence similarity shared by the mouse Ces genes, the tissue-specific distribution of expression for these enzymes has not been fully addressed. Therefore, we performed studies to provide a comprehensive tissue distribution analysis of mouse Ces mRNAs. These data demonstrated that while the mouse Ces family 1 is highly expressed in liver and family 2 in intestine, many Ces genes have a wide and unique tissue distribution defined by relative mRNA levels. Furthermore, evaluating Ces gene expression in response to pharmacologic activation of lipid- and xenobiotic-sensing nuclear hormone receptors showed differential regulation. Finally, specific shifts in Ces gene expression were seen in peritoneal macrophages following lipopolysaccharide treatment and in a steatotic liver model induced by high-fat feeding, two model systems relevant to disease. Overall these data show that each mouse Ces gene has its own distinctive tissue expression pattern and suggest that some CES may have tissue-specific roles in lipid metabolism and xenobiotic clearance.
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Affiliation(s)
- Ryan D Jones
- Departments of Physiology, UT Southwestern Medical Center, Dallas, TX 75390-9077, USA
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22
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Taylor AM, Liu B, Mari Y, Liu B, Repa JJ. Cyclodextrin mediates rapid changes in lipid balance in Npc1-/- mice without carrying cholesterol through the bloodstream. J Lipid Res 2012; 53:2331-42. [PMID: 22892156 DOI: 10.1194/jlr.m028241] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An injection of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) to mice lacking Niemann Pick type C (NPC) protein results in delayed neurodegeneration, decreased inflammation, and prolonged lifespan. Changes in sterol balance observed in Npc1(-/-) mice 24 h after HP-β-CD administration suggest that HP-β-CD facilitates the release of accumulated lysosomal cholesterol, the molecular hallmark of this genetic disorder. Current studies were performed to evaluate the time course of HP-β-CD effects. Within 3 h after HP-β-CD injection, decreases in cholesterol synthesis rates and increases in cholesteryl ester levels were detected in tissues of Npc1(-/-) mice. The levels of RNAs for target genes of sterol-sensing transcription factors were altered by 6 h in liver, spleen, and ileum. Despite the cholesterol-binding capacity of HP-β-CD, there was no evidence of increased cholesterol in plasma or urine of treated Npc1(-/-) mice, suggesting that HP-β-CD does not carry sterol from the lysosome into the bloodstream for ultimate urinary excretion. Similar changes in sterol balance were observed in cultured cells from Npc1(-/-) mice using HP-β-CD and sulfobutylether-β-CD, a variant that can interact with sterol but not facilitate its solubilization. Taken together, our results demonstrate that HP-β-CD works in cells of Npc1(-/-) mice by rapidly liberating lysosomal cholesterol for normal sterol processing within the cytosolic compartment.
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Affiliation(s)
- Anna M Taylor
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9077, USA
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Jones RD, Repa JJ, Russell DW, Dietschy JM, Turley SD. Delineation of biochemical, molecular, and physiological changes accompanying bile acid pool size restoration in Cyp7a1(-/-) mice fed low levels of cholic acid. Am J Physiol Gastrointest Liver Physiol 2012; 303:G263-74. [PMID: 22628034 PMCID: PMC3404571 DOI: 10.1152/ajpgi.00111.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cholesterol 7α-hydroxylase (CYP7A1) is the initiating and rate-limiting enzyme in the neutral pathway that converts cholesterol to primary bile acids (BA). CYP7A1-deficient (Cyp7a1(-/-)) mice have a depleted BA pool, diminished intestinal cholesterol absorption, accelerated fecal sterol loss, and increased intestinal cholesterol synthesis. To determine the molecular and physiological effects of restoring the BA pool in this model, adult female Cyp7a1(-/-) mice and matching Cyp7a1(+/+) controls were fed diets containing cholic acid (CA) at modest levels [0.015, 0.030, and 0.060% (wt/wt)] for 15-18 days. A level of just 0.03% provided a CA intake of ~12 μmol (4.8 mg) per day per 100 g body wt and was sufficient in the Cyp7a1(-/-) mice to normalize BA pool size, fecal BA excretion, fractional cholesterol absorption, and fecal sterol excretion but caused a significant rise in the cholesterol concentration in the small intestine and liver, as well as a marked inhibition of cholesterol synthesis in these organs. In parallel with these metabolic changes, there were marked shifts in intestinal and hepatic expression levels for many target genes of the BA sensor farnesoid X receptor, as well as genes involved in cholesterol transport, especially ATP-binding cassette (ABC) transporter A1 (ABCA1) and ABCG8. In Cyp7a1(+/+) mice, this level of CA supplementation did not significantly disrupt BA or cholesterol metabolism, except for an increase in fecal BA excretion and marginal changes in mRNA expression for some BA synthetic enzymes. These findings underscore the importance of using moderate dietary BA levels in studies with animal models.
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Affiliation(s)
- Ryan D. Jones
- 2Department of Physiology, University of Texas Southwestern Medical School, Dallas, Texas; and
| | - Joyce J. Repa
- 1Department of Internal Medicine, University of Texas Southwestern Medical School, Dallas, Texas; ,2Department of Physiology, University of Texas Southwestern Medical School, Dallas, Texas; and
| | - David W. Russell
- 3Department of Molecular Genetics, University of Texas Southwestern Medical School, Dallas, Texas
| | - John M. Dietschy
- 1Department of Internal Medicine, University of Texas Southwestern Medical School, Dallas, Texas;
| | - Stephen D. Turley
- 1Department of Internal Medicine, University of Texas Southwestern Medical School, Dallas, Texas;
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Regulator of G protein signaling 2 is a key modulator of airway hyperresponsiveness. J Allergy Clin Immunol 2012; 130:968-76.e3. [PMID: 22704538 DOI: 10.1016/j.jaci.2012.05.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2011] [Revised: 03/29/2012] [Accepted: 05/01/2012] [Indexed: 01/28/2023]
Abstract
BACKGROUND Drugs targeting individual G protein-coupled receptors are used as asthma therapies, but this strategy is limited because of G protein-coupled receptor signal redundancy. Regulator of G protein signaling 2 (RGS2), an intracellular selective inhibitor of multiple bronchoconstrictor receptors, may play a central role in the pathophysiology and treatment of asthma. OBJECTIVE We defined functions and mechanisms of RGS2 in regulating airway hyperresponsiveness (AHR), the pathophysiologic hallmark of asthma. METHODS Real-time PCR and Western blot were used to determine changes in RGS2 expression in ovalbumin-sensitized/-challenged mice. We also used immunohistochemistry and real-time PCR to compare RGS2 expression between human asthmatic and control subjects. The AHR of RGS2 knockout mice was assessed by using invasive tracheostomy and unrestrained plethysmography. Effects of loss of RGS2 on mouse airway smooth muscle (ASM) remodeling, contraction, intracellular Ca(2+), and mitogenic signaling were determined in vivo and in vitro. RESULTS RGS2 was highly expressed in human and murine bronchial epithelium and ASM and was markedly downregulated in lungs of ovalbumin-sensitized/-challenged mice. Lung tissues and blood monocytes from asthma patients expressed significantly lower RGS2 protein (lung) and mRNA (monocytes) than from nonasthma subjects. The extent of reduction of RGS2 on human monocytes correlated with increased AHR. RGS2 knockout caused spontaneous AHR in mice. Loss of RGS2 augmented Ca(2+) mobilization and contraction of ASM cells. Loss of RGS2 also increased ASM mass and stimulated ASM cell growth via extracellular signal-regulated kinase and phosphatidylinositol 3-kinase pathways. CONCLUSION We identified RGS2 as a potent modulator of AHR and a potential novel therapeutic target for asthma.
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Lee JK, Chung J, Druey KM, Tansey MG. RGS10 exerts a neuroprotective role through the PKA/c-AMP response-element (CREB) pathway in dopaminergic neuron-like cells. J Neurochem 2012; 122:333-43. [PMID: 22564151 DOI: 10.1111/j.1471-4159.2012.07780.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Regulator of G-protein signaling-10 (RGS10) is a GTPase activating protein for Gαi/q/z subunits that is highly expressed in the immune system and in a broad range of brain regions including the hippocampus, striatum, dorsal raphe, and ventral midbrain. Previously, we reported that RGS10-null mice display increased vulnerability to chronic systemic inflammation-induced degeneration of nigral dopaminergic (DA) neurons. Given that RGS10 is expressed in DA neurons, we investigated the extent to which RGS10 regulates cell survival under conditions of inflammatory stress. Because of the inherent limitations associated with use of primary DA neurons for biochemical analyses, we employed a well-characterized ventral mesencephalon DA neuroblastoma cell line (MN9D) for our studies. We found that stable over-expression of RGS10 rendered them resistant to TNF-induced cytotoxicity; whereas MN9D cells expressing mutant RGS10-S168A (which is resistant to phosphorylation by protein kinase A at a serine residue that promotes its nuclear translocation) showed similar sensitivity to TNF as the parental MN9D cells. Using biochemical and pharmacologic approaches, we identified protein kinase A and the downstream phospho-cAMP response element-binding signaling pathway (and ruled out ERK 1/2, JNK, and NFkB) as key mediators of the neuroprotective effect of RGS10 against inflammatory stress.
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Affiliation(s)
- Jae-Kyung Lee
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, USA
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Abstract
To identify potential microRNA (miRNA) links between Smad3, a mediator of TGF-β (transforming growth factor-β) signaling, and E-cadherin, we characterized the miRNA profiles of two gastric cancer cell lines: SNU484-LPCX, which does not express Smad3, and SNU484-Smad3, in which Smad3 is overexpressed. We found that among differentially expressed miRNAs, miR-200 family members are overexpressed in SNU484-Smad3 cells. Subsequent studies, including analysis of the effects of silencing Smad3 in SNU484-Smad3 cells and a luciferase reporter assay, revealed that Smad3 directly binds to a Smad-binding element located in the promoter region of miR-200b/a, where it functions as a transcriptional activator. TGF-β did not affect the regulatory role of Smad3 in transcription of miR-200 and expression of epithelial-mesenchymal transition markers. We conclude that Smad3 regulates, at the transcriptional level, miR-200 family members, which themselves regulate ZEB1 and ZEB2, known transcriptional repressors of E-cadherin, at the posttranscriptional level in a TGF-β-independent manner. This represents a novel link between Smad3 and posttranscriptional regulation by miRNAs in epithelial-mesenchymal transition in gastric cancer cells.
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Zhang H, Gu S, Al-Sabeq B, Wang S, He J, Tam A, Cifelli C, Mathalone N, Tirgari S, Boyd S, Heximer SP. Origin-specific epigenetic program correlates with vascular bed-specific differences in Rgs5 expression. FASEB J 2011; 26:181-91. [PMID: 21965603 DOI: 10.1096/fj.11-185454] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cells from multiple origins contribute to vascular smooth muscle cell (VSMC) development. Phenotypic heterogeneity of VSMCs is associated with their point of developmental origin; however, the mechanisms driving such differences are unknown. We here examined the mechanisms controlling vascular bed-specific differences in Rgs5 expression during development. Rgs5 levels were similar across different regions of the vasculature in neonatal animals but were >15-fold higher in descending aortas compared with carotid arteries of adult mice. Thus, vessel bed-specific changes in regulation of Rgs5 expression occurred during vessel maturation. Examination of adult Rgs5-LacZ reporter mice revealed lower Rgs5 expression in VSMCs originating from the third (carotid artery) branchial arch compared with those originating in the fourth and sixth (aortic B segment, right subclavian, and ductus arteriosus) branchial arches. Indeed, a mosaic Rgs5 expression pattern, with discreet LacZ boundaries between VSMCs derived from different developmental origins, was observed. Furthermore, Rgs5-LacZ expression was correlated with the site of VSMC origin (splanchic mesoderm ≈ local mesenchyme > somites > proepicardium > mesothelium). Surprisingly, Rgs5 reporter activity in cultured carotid artery- and descending aorta-derived cells did not recapitulate the differences observed in vivo. Consistent with a developmental origin-specific epigenetic mechanism driving the observed expression differences in vivo, the Rgs5 promoter showed increased methylation on CpG dinucleotides in carotid arteries compared with that in descending aortas in adult but not in neonatal mice. In vitro methylation of the Rgs5 promoter confirmed that its activity is sensitive to transcriptional down-regulation by CpG methylation. These data suggest that an origin-dependent epigenetic program regulates vascular bed- and maturation state-dependent regulation of VSMC-specific gene transcription.
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Affiliation(s)
- Hangjun Zhang
- Department of Physiology, Heart, and Stroke, University of Toronto, Toronto, ON Canada
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28
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Unesterified cholesterol accumulation in late endosomes/lysosomes causes neurodegeneration and is prevented by driving cholesterol export from this compartment. J Neurosci 2011; 31:9404-13. [PMID: 21697390 DOI: 10.1523/jneurosci.1317-11.2011] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
While unesterified cholesterol (C) is essential for remodeling neuronal plasma membranes, its role in certain neurodegenerative disorders remains poorly defined. Uptake of sterol from pericellular fluid requires processing that involves two lysosomal proteins, lysosomal acid lipase, which hydrolyzes C esters, and NPC1 (Niemann-Pick type C1). In systemic tissues, inactivation of either protein led to sterol accumulation and cell death, but in the brain, inactivation of only NPC1 caused C sequestration and neurodegeneration. When injected into the CNS of the npc1(-/-) mouse, 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), a compound known to prevent this C accumulation, diffused throughout the brain and was excreted with a t(½) of 6.5 h. This agent caused suppression of C synthesis, elevation of C esters, suppression of sterol regulatory-binding protein 2 (SREBP2) target genes, and activation of liver X receptor-controlled genes. These findings indicated that HP-β-CD promoted movement of the sequestered C from lysosomes to the metabolically active pool of C in the cytosolic compartment of cells in the CNS. The ED(50) for this agent in the brain was ∼0.5 mg/kg, and the therapeutic effect lasted >7 d. Continuous infusion of HP-β-CD into the ventricular system of npc1(-/-) animals between 3 and 7 weeks of age normalized the biochemical abnormalities and completely prevented the expected neurodegeneration. These studies support the concept that neurons continuously acquire C from interstitial fluid to permit plasma membrane turnover and remodeling. Inactivation of NPC1 leads to lysosomal C sequestration and neurodegeneration, but this is prevented by the continuous, direct administration of HP-β-CD into the CNS.
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Tran TA, Nguyen AD, Chang J, Goldberg MS, Lee JK, Tansey MG. Lipopolysaccharide and tumor necrosis factor regulate Parkin expression via nuclear factor-kappa B. PLoS One 2011; 6:e23660. [PMID: 21858193 PMCID: PMC3157435 DOI: 10.1371/journal.pone.0023660] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 07/22/2011] [Indexed: 11/18/2022] Open
Abstract
Inflammation and oxidative stress have been implicated in the pathophysiology of Parkinson's disease (PD) and inhibition of microglial activation attenuates degeneration of dopaminergic (DA) neurons in animal models of PD. Loss-of-function mutations in the parkin gene, which encodes an E3 ubiquitin ligase, cause autosomal recessive parkinsonism. While most studies on Parkin have focused on its function in neurons, here we demonstrate that Parkin mRNA and protein is detectable in brain-resident microglia and peripheral macrophages. Using pharmacologic and genetic approaches, we found that Parkin levels are regulated by inflammatory signaling. Specifically, exposure to LPS or Tumor Necrosis Factor (TNF) induced a transient and dose-dependent decrease in Parkin mRNA and protein in microglia, macrophages and neuronal cells blockable by inhibitors of Nuclear Factor-Kappa B (NF-κB) signaling and not observed in MyD88-null cells. Moreover, using luciferase reporter assays, we identified an NF-κB response element in the mouse parkin promoter responsible for mediating the transcriptional repression, which was abrogated when the consensus sequence was mutated. Functionally, activated macrophages from Parkin-null mice displayed increased levels of TNF, IL-1β, and iNOS mRNA compared to wild type macrophages but no difference in levels of Nrf2, HO-1, or NQO1. One implication of our findings is that chronic inflammatory conditions may reduce Parkin levels and phenocopy parkin loss-of-function mutations, thereby increasing the vulnerability for degeneration of the nigrostriatal pathway and development of PD.
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Affiliation(s)
- Thi A. Tran
- Departments of Physiology, The University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Andrew D. Nguyen
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Jianjun Chang
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Matthew S. Goldberg
- Department of Neurology, The University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Jae-Kyung Lee
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Malú G. Tansey
- Departments of Physiology, The University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, United States of America
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30
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Jeong YS, Kim D, Lee YS, Kim HJ, Han JY, Im SS, Chong HK, Kwon JK, Cho YH, Kim WK, Osborne TF, Horton JD, Jun HS, Ahn YH, Ahn SM, Cha JY. Integrated expression profiling and genome-wide analysis of ChREBP targets reveals the dual role for ChREBP in glucose-regulated gene expression. PLoS One 2011; 6:e22544. [PMID: 21811631 PMCID: PMC3141076 DOI: 10.1371/journal.pone.0022544] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Accepted: 06/29/2011] [Indexed: 01/23/2023] Open
Abstract
The carbohydrate response element binding protein (ChREBP), a basic helix-loop-helix/leucine zipper transcription factor, plays a critical role in the control of lipogenesis in the liver. To identify the direct targets of ChREBP on a genome-wide scale and provide more insight into the mechanism by which ChREBP regulates glucose-responsive gene expression, we performed chromatin immunoprecipitation-sequencing and gene expression analysis. We identified 1153 ChREBP binding sites and 783 target genes using the chromatin from HepG2, a human hepatocellular carcinoma cell line. A motif search revealed a refined consensus sequence (CABGTG-nnCnG-nGnSTG) to better represent critical elements of a functional ChREBP binding sequence. Gene ontology analysis shows that ChREBP target genes are particularly associated with lipid, fatty acid and steroid metabolism. In addition, other functional gene clusters related to transport, development and cell motility are significantly enriched. Gene set enrichment analysis reveals that ChREBP target genes are highly correlated with genes regulated by high glucose, providing a functional relevance to the genome-wide binding study. Furthermore, we have demonstrated that ChREBP may function as a transcriptional repressor as well as an activator.
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Affiliation(s)
- Yun-Seung Jeong
- Department of Molecular Medicine, Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea
| | - Deokhoon Kim
- Department of Molecular Medicine, Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea
| | - Yong Seok Lee
- Korean BioInformation Center (KOBIC), KRIBB, Daejeon, Korea
- Healthcare Service Group, Samsung SDS, Seoul, Korea
| | - Ha-Jung Kim
- Department of Molecular Medicine, Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea
| | - Jung-Youn Han
- Department of Molecular Medicine, Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea
| | - Seung-Soon Im
- Sanford-Burnham Medical Research Institute, Orlando, Florida, United States of America
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, California, United States of America
| | - Hansook Kim Chong
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, California, United States of America
| | - Je-Keun Kwon
- Korean BioInformation Center (KOBIC), KRIBB, Daejeon, Korea
| | - Yun-Ho Cho
- Department of Molecular Medicine, Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea
| | - Woo Kyung Kim
- Department of Molecular Medicine, Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea
| | - Timothy F. Osborne
- Sanford-Burnham Medical Research Institute, Orlando, Florida, United States of America
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, California, United States of America
| | - Jay D. Horton
- Department of Molecular Genetics, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Hee-Sook Jun
- Department of Molecular Medicine, Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea
| | - Yong-Ho Ahn
- Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, Seoul, Korea
| | - Sung-Min Ahn
- Department of Molecular Medicine, Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea
- Department of Translational Medicine, Gachon University Gil Hospital, Incheon, Korea
- * E-mail: (JYC); (SMA)
| | - Ji-Young Cha
- Department of Molecular Medicine, Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea
- * E-mail: (JYC); (SMA)
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Drusenheimer N, Nayernia K, Meinhardt A, Jung B, Arnold HH, Engel W. Overexpression of Lis1 in Different Stages of Spermatogenesis Does Not Result in an Aberrant Phenotype. Cytogenet Genome Res 2011; 134:269-82. [DOI: 10.1159/000329482] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/09/2011] [Indexed: 01/15/2023] Open
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Chuang JC, Perello M, Sakata I, Osborne-Lawrence S, Savitt JM, Lutter M, Zigman JM. Ghrelin mediates stress-induced food-reward behavior in mice. J Clin Invest 2011; 121:2684-92. [PMID: 21701068 DOI: 10.1172/jci57660] [Citation(s) in RCA: 240] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Accepted: 04/13/2011] [Indexed: 11/17/2022] Open
Abstract
The popular media and personal anecdotes are rich with examples of stress-induced eating of calorically dense "comfort foods." Such behavioral reactions likely contribute to the increased prevalence of obesity in humans experiencing chronic stress or atypical depression. However, the molecular substrates and neurocircuits controlling the complex behaviors responsible for stress-based eating remain mostly unknown, and few animal models have been described for probing the mechanisms orchestrating this response. Here, we describe a system in which food-reward behavior, assessed using a conditioned place preference (CPP) task, is monitored in mice after exposure to chronic social defeat stress (CSDS), a model of prolonged psychosocial stress, featuring aspects of major depression and posttraumatic stress disorder. Under this regime, CSDS increased both CPP for and intake of high-fat diet, and stress-induced food-reward behavior was dependent on signaling by the peptide hormone ghrelin. Also, signaling specifically in catecholaminergic neurons mediated not only ghrelin's orexigenic, antidepressant-like, and food-reward behavioral effects, but also was sufficient to mediate stress-induced food-reward behavior. Thus, this mouse model has allowed us to ascribe a role for ghrelin-engaged catecholaminergic neurons in stress-induced eating.
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Affiliation(s)
- Jen-Chieh Chuang
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-9077, USA
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Altered expression and function of regulator of G-protein signaling-17 (RGS17) in hepatocellular carcinoma. Cell Signal 2011; 23:1603-10. [PMID: 21620966 DOI: 10.1016/j.cellsig.2011.05.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 05/10/2011] [Accepted: 05/12/2011] [Indexed: 11/22/2022]
Abstract
Guanine nucleotide regulatory proteins (G-proteins) are central to normal hepatocyte function and are implicated in hepatic disease initiation and progression. Regulators of G-protein signaling (RGS) are critical to defining G-protein-dependent signal fidelity, yet the role of RGS proteins in the liver is poorly defined. The aims of this study were to determine RGS17 expression in normal and transformed hepatic tissue and cells, and address the function of RGS17 in hepatic tumorgenicity. RGS17 expression was determined in human and rat HCC tissue and cell lines. Molecular approaches were used to alter RGS17 expression in HCC cells, effects on cell function measured, and RGS17 association with specific Gα-subunits determined. Using these approaches RGS17 mRNA, but not protein, was detectable in human and rat HCC tissue and cells. Conversely, RGS17 mRNA was not detected in normal tissue, isolated hepatocytes, or non-tumorigenic hepatic cells. Subsequent studies using transfected cells demonstrated that RGS17 proteins were not post-translationally modified in HCC cells, and RGS17 expression is governed by protein degradation and not via miRNAs. Notwithstanding inherently low RGS17 protein levels, altering RGS17 expression profoundly affected HCC cell mitogenesis and migration. Analysis of RGS17-G-protein interaction demonstrated RGS17 associates with both Giα- and Gqα-subunits in HCC cells of human and rat origin. In conclusion, these data demonstrate that, despite difficulties in measuring endogenous RGS protein expression, RGS17 is differentially expressed in HCC and plays a central role in regulating transformed hepatocyte tumorgenicity.
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Pashkov V, Huang J, Parameswara VK, Kedzierski W, Kurrasch DM, Tall GG, Esser V, Gerard RD, Uyeda K, Towle HC, Wilkie TM. Regulator of G protein signaling (RGS16) inhibits hepatic fatty acid oxidation in a carbohydrate response element-binding protein (ChREBP)-dependent manner. J Biol Chem 2011; 286:15116-25. [PMID: 21357625 DOI: 10.1074/jbc.m110.216234] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
G protein-coupled receptor (GPCR) pathways control glucose and fatty acid metabolism and the onset of obesity and diabetes. Regulators of G protein signaling (RGS) are GTPase-activating proteins (GAPs) for G(i) and G(q) α-subunits that control the intensity and duration of GPCR signaling. Herein we determined the role of Rgs16 in GPCR regulation of liver metabolism. Rgs16 is expressed during the last few hours of the daily fast in periportal hepatocytes, the oxygen-rich zone of the liver where lipolysis and gluconeogenesis predominate. Rgs16 knock-out mice had elevated expression of fatty acid oxidation genes in liver, higher rates of fatty acid oxidation in liver extracts, and higher plasma β-ketone levels compared with wild type mice. By contrast, transgenic mice that overexpressed RGS16 protein specifically in liver exhibited reciprocal phenotypes as well as low blood glucose levels compared with wild type littermates and fatty liver after overnight fasting. The transcription factor carbohydrate response element-binding protein (ChREBP), which induces fatty acid synthesis genes in response to high carbohydrate feeding, was unexpectedly required during fasting for maximal Rgs16 transcription in liver and in cultured primary hepatocytes during gluconeogenesis. Thus, RGS16 provides a signaling mechanism for glucose production to inhibit GPCR-stimulated fatty acid oxidation in hepatocytes.
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Affiliation(s)
- Victor Pashkov
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041, USA
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35
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Ramirez CM, Liu B, Aqul A, Taylor AM, Repa JJ, Turley SD, Dietschy JM. Quantitative role of LAL, NPC2, and NPC1 in lysosomal cholesterol processing defined by genetic and pharmacological manipulations. J Lipid Res 2011; 52:688-98. [PMID: 21289032 DOI: 10.1194/jlr.m013789] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipoprotein cholesterol taken up by cells is processed in the endosomal/lysosomal (E/L) compartment by the sequential action of lysosomal acid lipase (LAL), Niemann-Pick C2 (NPC2), and Niemann-Pick C1 (NPC1). Inactivation of NPC2 in mouse caused sequestration of unesterified cholesterol (UC) and expanded the whole animal sterol pool from 2,305 to 4,337 mg/kg. However, this pool increased to 5,408 and 9,480 mg/kg, respectively, when NPC1 or LAL function was absent. The transport defect in mutants lacking NPC2 or NPC1, but not in those lacking LAL, was reversed by cyclodextrin (CD), and the ED₅₀ values for this reversal varied from ~40 mg/kg in kidney to >20,000 mg/kg in brain in both groups. This reversal occurred only with a CD that could interact with UC. Further, a CD that could interact with, but not solubilize, UC still overcame the transport defect. These studies showed that processing and export of sterol from the late E/L compartment was quantitatively different in mice lacking LAL, NPC2, or NPC1 function. In both npc2(-/-) and npc1(-/-) mice, the transport defect was reversed by a CD that interacted with UC, likely at the membrane/bulk-water interface, allowing sterol to move rapidly to the export site of the E/L compartment.
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Affiliation(s)
- Charina M Ramirez
- Department of Pediatrics, University of Texas Southwestern Medical School, Dallas, TX 75390-9151, USA
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PSCDGs of mouse multipotent adult germline stem cells can enter and progress through meiosis to form haploid male germ cells in vitro. Differentiation 2010; 80:184-94. [DOI: 10.1016/j.diff.2010.08.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 08/03/2010] [Accepted: 08/12/2010] [Indexed: 11/22/2022]
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37
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Blazer LL, Roman DL, Chung A, Larsen MJ, Greedy BM, Husbands SM, Neubig RR. Reversible, allosteric small-molecule inhibitors of regulator of G protein signaling proteins. Mol Pharmacol 2010; 78:524-33. [PMID: 20571077 PMCID: PMC2939488 DOI: 10.1124/mol.110.065128] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Accepted: 06/15/2010] [Indexed: 12/20/2022] Open
Abstract
Regulators of G protein signaling (RGS) proteins are potent negative modulators of G protein signaling and have been proposed as potential targets for small-molecule inhibitor development. We report a high-throughput time-resolved fluorescence resonance energy transfer screen to identify inhibitors of RGS4 and describe the first reversible small-molecule inhibitors of an RGS protein. Two closely related compounds, typified by CCG-63802 [((2E)-2-(1,3-benzothiazol-2-yl)-3-[9-methyl-2-(3-methylphenoxy)-4-oxo-4H-pyrido[1,2-a]pyrimidin-3-yl]prop-2-enenitrile)], inhibit the interaction between RGS4 and Galpha(o) with an IC(50) value in the low micromolar range. They show selectivity among RGS proteins with a potency order of RGS 4 > 19 = 16 > 8 >> 7. The compounds inhibit the GTPase accelerating protein activity of RGS4, and thermal stability studies demonstrate binding to the RGS but not to Galpha(o). On RGS4, they depend on an interaction with one or more cysteines in a pocket that has previously been identified as an allosteric site for RGS regulation by acidic phospholipids. Unlike previous small-molecule RGS inhibitors identified to date, these compounds retain substantial activity under reducing conditions and are fully reversible on the 10-min time scale. CCG-63802 and related analogs represent a useful step toward the development of chemical tools for the study of RGS physiology.
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Affiliation(s)
- Levi L Blazer
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109, USA
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Kim G, Lee Y, Jeong EY, Jung S, Son H, Lee DH, Roh GS, Kang SS, Cho GJ, Choi WS, Kim HJ. Acute stress responsive RGS proteins in the mouse brain. Mol Cells 2010; 30:161-5. [PMID: 20680490 DOI: 10.1007/s10059-010-0102-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 05/20/2010] [Accepted: 05/25/2010] [Indexed: 11/30/2022] Open
Abstract
Regulator of G-protein signaling (RGS) proteins play an important role in G-protein coupled receptor (GPCR) signaling and the activity of some GPCRs is modulated via RGS protein levels during stress response. The aim of this study was to investigate changes in RGS protein mRNA expressions in the mouse brain after 2h restraint stress. The mRNA level of 19 RGS proteins was analyzed using real-time PCR in six brain regions, which included the prefrontal cortex, amygdala, hippocampus, hypothalamus, striatum, and pituitary gland, from control and stressed mouse. We found that the level of mRNA of each RGS varied according to brain region and that two to eight RGS proteins exhibited changes in mRNA levels in each brain region by restraint stress. It was also revealed that RGS4 protein amount was consistent with mRNA level, indicating RGS4 protein may have regulatory roles in the acute stress response.
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Affiliation(s)
- Gyeongwha Kim
- Department of Anatomy and Neurobiology, Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju 660-751, Korea
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Kenchappa RS, Tep C, Korade Z, Urra S, Bronfman FC, Yoon SO, Carter BD. p75 neurotrophin receptor-mediated apoptosis in sympathetic neurons involves a biphasic activation of JNK and up-regulation of tumor necrosis factor-alpha-converting enzyme/ADAM17. J Biol Chem 2010; 285:20358-68. [PMID: 20421303 PMCID: PMC2888447 DOI: 10.1074/jbc.m109.082834] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 04/13/2010] [Indexed: 02/05/2023] Open
Abstract
During the development of the sympathetic nervous system, the p75 neurotrophin receptor (p75NTR) has a dual function: promoting survival together with TrkA in response to NGF, but inducing cell death upon binding pro or mature brain-derived neurotrophic factor (BDNF). Apoptotic signaling through p75NTR requires activation of the stress kinase, JNK. However, the receptor also undergoes regulated proteolysis, first by a metalloprotease, and then by gamma-secretase, in response to pro-apoptotic ligands and this is necessary for receptor mediated neuronal death (Kenchappa, R. S., Zampieri, N., Chao, M. V., Barker, P. A., Teng, H. K., Hempstead, B. L., and Carter, B. D. (2006) Neuron 50, 219-232). Hence, the relationship between JNK activation and receptor proteolysis remains to be defined. Here, we report that JNK3 activation is necessary for p75NTR cleavage; however, following release of the intracellular domain, there is a secondary activation of JNK3 that is cleavage dependent. Receptor proteolysis and apoptosis were prevented in sympathetic neurons from jnk3(-/-) mice, while activation of JNK by ectopic expression of MEKK1 induced p75NTR cleavage and cell death. Proteolysis of the receptor was not detected until 6 h after BDNF treatment, suggesting that JNK3 promotes cleavage through a transcriptional mechanism. In support of this hypothesis, BDNF up-regulated tumor necrosis factor-alpha-converting enzyme (TACE)/ADAM17 mRNA and protein in wild-type, but not jnk3(-/-) sympathetic neurons. Down-regulation of TACE by RNA interference blocked BDNF-induced p75NTR cleavage and apoptosis, indicating that this metalloprotease is responsible for the initial processing of the receptor. Together, these results demonstrate that p75NTR-mediated activation of JNK3 is required for up-regulation of TACE, which promotes receptor proteolysis, leading to prolonged activation of JNK3 and subsequent apoptosis in sympathetic neurons.
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Affiliation(s)
- Rajappa S. Kenchappa
- From the Department of Biochemistry and Center for Molecular Neuroscience, Vanderbilt University Medical School, Nashville, Tennessee 37232
| | - Chhavy Tep
- the Center for Molecular Neurobiology and Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210
| | - Zeljka Korade
- From the Department of Biochemistry and Center for Molecular Neuroscience, Vanderbilt University Medical School, Nashville, Tennessee 37232
| | - Soledad Urra
- the Department of Physiology, Neurobiology Unit, Center of Aging and Regeneration, Nucleus Millenium in Regenerative Biology, Faculty of Biological Sciences, Pontificia Universidad Catolica, Alameda 340, Santiago 8320000, Chile
| | - Francisca C. Bronfman
- the Department of Physiology, Neurobiology Unit, Center of Aging and Regeneration, Nucleus Millenium in Regenerative Biology, Faculty of Biological Sciences, Pontificia Universidad Catolica, Alameda 340, Santiago 8320000, Chile
| | - Sung Ok Yoon
- the Center for Molecular Neurobiology and Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210
| | - Bruce D. Carter
- From the Department of Biochemistry and Center for Molecular Neuroscience, Vanderbilt University Medical School, Nashville, Tennessee 37232
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Kostromina E, Gustavsson N, Wang X, Lim CY, Radda GK, Li C, Han W. Glucose intolerance and impaired insulin secretion in pancreas-specific signal transducer and activator of transcription-3 knockout mice are associated with microvascular alterations in the pancreas. Endocrinology 2010; 151:2050-9. [PMID: 20215569 PMCID: PMC2869255 DOI: 10.1210/en.2009-1199] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Maintenance of glucose homeostasis depends on adequate amount and precise pattern of insulin secretion, which is determined by both beta-cell secretory processes and well-developed microvascular network within endocrine pancreas. The development of highly organized microvasculature and high degrees of capillary fenestrations in endocrine pancreas is greatly dependent on vascular endothelial growth factor-A (VEGF-A) from islet cells. However, it is unclear how VEGF-A production is regulated in endocrine pancreas. To understand whether signal transducer and activator of transcription (STAT)-3 is involved in VEGF-A regulation and subsequent islet and microvascular network development, we generated a mouse line carrying pancreas-specific deletion of STAT3 (p-KO) and performed physiological analyses both in vivo and using isolated islets, including glucose and insulin tolerance tests, and insulin secretion measurements. We also studied microvascular network and islet development by using immunohistochemical methods. The p-KO mice exhibited glucose intolerance and impaired insulin secretion in vivo but normal insulin secretion in isolated islets. Microvascular density in the pancreas was reduced in p-KO mice, along with decreased expression of VEGF-A, but not other vasotropic factors in islets in the absence of pancreatic STAT3 signaling. Together, our study suggests that pancreatic STAT3 signaling is required for the normal development and maintenance of endocrine pancreas and islet microvascular network, possibly through its regulation of VEGF-A.
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Affiliation(s)
- Elena Kostromina
- Singapore Bioimaging Consortium, Agency for Science, Technology, and Research, Singapore 138667
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RGS4 is a negative regulator of insulin release from pancreatic beta-cells in vitro and in vivo. Proc Natl Acad Sci U S A 2010; 107:7999-8004. [PMID: 20385802 DOI: 10.1073/pnas.1003655107] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Therapeutic strategies that augment insulin release from pancreatic beta-cells are considered beneficial in the treatment of type 2 diabetes. We previously demonstrated that activation of beta-cell M(3) muscarinic receptors (M3Rs) greatly promotes glucose-stimulated insulin secretion (GSIS), suggesting that strategies aimed at enhancing signaling through beta-cell M3Rs may become therapeutically useful. M3R activation leads to the stimulation of G proteins of the G(q) family, which are under the inhibitory control of proteins known as regulators of G protein signaling (RGS proteins). At present, it remains unknown whether RGS proteins play a role in regulating insulin release. To address this issue, we initially demonstrated that MIN6 insulinoma cells express functional M3Rs and that RGS4 was by far the most abundant RGS protein expressed by these cells. Strikingly, siRNA-mediated knockdown of RGS4 expression in MIN6 cells greatly enhanced M3R-mediated augmentation of GSIS and calcium release. We obtained similar findings using pancreatic islets prepared from RGS4-deficient mice. Interestingly, RGS4 deficiency had little effect on insulin release caused by activation of other beta-cell GPCRs. Finally, treatment of mutant mice selectively lacking RGS4 in pancreatic beta-cells with a muscarinic agonist (bethanechol) led to significantly increased plasma insulin and reduced blood glucose levels, as compared to control littermates. Studies with beta-cell-specific M3R knockout mice showed that these responses were mediated by beta-cell M3Rs. These findings indicate that RGS4 is a potent negative regulator of M3R function in pancreatic beta-cells, suggesting that RGS4 may represent a potential target to promote insulin release for therapeutic purposes.
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Ogihara T, Chuang JC, Vestermark GL, Garmey JC, Ketchum RJ, Huang X, Brayman KL, Thorner MO, Repa JJ, Mirmira RG, Evans-Molina C. Liver X receptor agonists augment human islet function through activation of anaplerotic pathways and glycerolipid/free fatty acid cycling. J Biol Chem 2010; 285:5392-404. [PMID: 20007976 PMCID: PMC2820768 DOI: 10.1074/jbc.m109.064659] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Recent studies in rodent models suggest that liver X receptors (LXRs) may play an important role in the maintenance of glucose homeostasis and islet function. To date, however, no studies have comprehensively examined the role of LXRs in human islet biology. Human islets were isolated from non-diabetic donors and incubated in the presence or absence of two synthetic LXR agonists, TO-901317 and GW3965, under conditions of low and high glucose. LXR agonist treatment enhanced both basal and stimulated insulin secretion, which corresponded to an increase in the expression of genes involved in anaplerosis and reverse cholesterol transport. Furthermore, enzyme activity of pyruvate carboxylase, a key regulator of pyruvate cycling and anaplerotic flux, was also increased. Whereas LXR agonist treatment up-regulated known downstream targets involved in lipogenesis, we observed no increase in the accumulation of intra-islet triglyceride at the dose of agonist used in our study. Moreover, LXR activation increased expression of the genes encoding hormone-sensitive lipase and adipose triglyceride lipase, two enzymes involved in lipolysis and glycerolipid/free fatty acid cycling. Chronically, insulin gene expression was increased after treatment with TO-901317, and this was accompanied by increased Pdx-1 nuclear protein levels and enhanced Pdx-1 binding to the insulin promoter. In conclusion, our data suggest that LXR agonists have a direct effect on the islet to augment insulin secretion and expression, actions that should be considered either as therapeutic or unintended side effects, as these agents are developed for clinical use.
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Affiliation(s)
- Takeshi Ogihara
- From the Herman B Wells Center for Pediatric Research and
- the Departments of Pediatrics and
| | | | | | | | - Robert J. Ketchum
- the Department of Structural Medicine, Rocky Vista University, Parker, Colorado 80134
| | - Xiaolun Huang
- Surgery, University of Virginia, Charlottesville, Virginia 22904, and
| | | | | | - Joyce J. Repa
- the Departments of Physiology and
- Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Raghavendra G. Mirmira
- From the Herman B Wells Center for Pediatric Research and
- the Departments of Pediatrics and
- Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Carmella Evans-Molina
- From the Herman B Wells Center for Pediatric Research and
- Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202
- To whom correspondence should be addressed: Indiana University School of Medicine, 635 Barnhill Dr., MS 2031A, Indianapolis, IN 46202. Tel.: 317-274-4145; Fax: 317-274-4107; E-mail:
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Chuang JC, Cui H, Mason BL, Mahgoub M, Bookout AL, Yu HG, Perello M, Elmquist JK, Repa JJ, Zigman JM, Lutter M. Chronic social defeat stress disrupts regulation of lipid synthesis. J Lipid Res 2010; 51:1344-53. [PMID: 20129912 DOI: 10.1194/jlr.m002196] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Several psychiatric disorders increase the risk of cardiovascular disease, including posttraumatic stress disorder and major depression. While the precise mechanism for this association has not yet been established, it has been shown that certain disorders promote an unfavorable lipid profile. To study the interaction of stress and lipid dysregulation, we utilized chronic social defeat stress (CSDS), a mouse model of chronic stress with features of posttraumatic stress disorder and major depression. Following exposure to CSDS, mice were given access to either regular chow or a Western-style diet high in fat and cholesterol (HFD). The combination of social stress and HFD resulted in significant perturbations in lipid regulation, including two key features of the metabolic syndrome: increased plasma levels of non-HDL cholesterol and intrahepatic accumulation of triglycerides. These effects were accompanied by a number of changes in the expression of hepatic genes involved in lipid regulation. Transcriptional activity of LXR, SREBP1c, and ChREBP were significantly affected by exposure to HFD and CSDS. We present CSDS as a model of social stress induced lipid dysregulation and propose that social stress alters lipid metabolism by increasing transcriptional activity of genes involved in lipid synthesis.
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Affiliation(s)
- Jen-Chieh Chuang
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Liu B, Ramirez CM, Miller AM, Repa JJ, Turley SD, Dietschy JM. Cyclodextrin overcomes the transport defect in nearly every organ of NPC1 mice leading to excretion of sequestered cholesterol as bile acid. J Lipid Res 2009; 51:933-44. [PMID: 19965601 DOI: 10.1194/jlr.m000257] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A mutation in NPC1 leads to sequestration of unesterified cholesterol in the late endosomal/lysosomal compartment of every cell culminating in the development of pulmonary, hepatic, and neurodegenerative disease. Acute administration of 2-hydroxypropyl-beta-cyclodextrin (CYCLO) rapidly overcomes this transport defect in both the 7-day-old pup and 49-day-old mature npc1(-/-) mouse, even though this compound is cleared from the body and plasma six times faster in the mature mouse than in the neonatal animal. The liberated cholesterol flows into the cytosolic ester pool, suppresses sterol synthesis, down-regulates SREBP2 and its target genes, and reduces expression of macrophage-associated inflammatory genes. These effects are seen in the liver and brain, as well as in peripheral organs like the spleen and kidney. Only the lung appears to be resistant to these effects. Forty-eight h after CYCLO administration to the 49-day-old animals, fecal acidic, but not neutral, sterol output increases, whole-animal cholesterol burden is reduced, and the hepatic and neurological inflammation is ameliorated. However, lifespan is extended only when the CYCLO is administered to the 7-day-old animals. These studies demonstrate that CYCLO administration acutely reverses the cholesterol transport defect seen in the NPC1 mouse at any age, and this reversal allows the sequestered sterol to be excreted from the body as bile acid.
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Affiliation(s)
- Benny Liu
- Departments of Internal Medicine, University of Texas Southwestern Medical School, Dallas, TX 75390-9151, USA
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45
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Kurrasch DM, Nevin LM, Wong JS, Baier H, Ingraham HA. Neuroendocrine transcriptional programs adapt dynamically to the supply and demand for neuropeptides as revealed in NSF mutant zebrafish. Neural Dev 2009; 4:22. [PMID: 19549326 PMCID: PMC2715394 DOI: 10.1186/1749-8104-4-22] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Accepted: 06/23/2009] [Indexed: 02/26/2023] Open
Abstract
BACKGROUND Regulated secretion of specialized neuropeptides in the vertebrate neuroendocrine system is critical for ensuring physiological homeostasis. Expression of these cell-specific peptide markers in the differentiating hypothalamus commences prior to birth, often predating the physiological demand for secreted neuropeptides. The conserved function and spatial expression of hypothalamic peptides in vertebrates prompted us to search for critical neuroendocrine genes in newly hatched zebrafish larvae. RESULTS We screened mutant 5 days post-fertilization zebrafish larvae that fail to undergo visually mediated background adaptation for disruption in hypothalamic pomc expression. To our surprise, the ATPase N-ethylmaleimide sensitive factor (nsf) was identified as an essential gene for maintenance of neuroendocrine transcriptional programs during the embryo-to-larva transition. Despite normal hypothalamic development in nsf(st53) mutants, neuropeptidergic cells exhibited a dramatic loss of cell-specific markers by 5 days post-fertilization that is accompanied by elevated intracellular neuropeptide protein. Consistent with the role of NSF in vesicle-membrane fusion events and intracellular trafficking, cytoplasmic endoplasmic reticulum-like membranes accumulate in nsf(-/-) hypothalamic neurons similar to that observed for SEC18 (nsf ortholog) yeast mutants. Our data support a model in which unspent neuropeptide cargo feedbacks to extinguish transcription in neuropeptidergic cells just as they become functionally required. In support of this model we found that gnrh3 transcripts remained unchanged in pre-migratory, non-functional gonadotropin-releasing hormone (GnRH) neurons in nsf(-/-) zebrafish. Furthermore, oxytocin-like (oxtl, intp) transcripts, which are found in osmoreceptive neurons and persist in mutant zebrafish, drop precipitously after mutant zebrafish are acutely challenged with high salt. CONCLUSION Our analyses of nsf mutant zebrafish reveal an unexpected role for NSF in hypothalamic development, with mutant 5 days post-fertilization larvae exhibiting a stage-dependent loss of neuroendocrine transcripts and a corresponding accumulation of neuropeptides in the soma. Based on our collective findings, we speculate that neuroendocrine transcriptional programs adapt dynamically to both the supply and demand for neuropeptides to ensure adequate homeostatic responses.
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Affiliation(s)
- Deborah M Kurrasch
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, USA.
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Korade Z, Kenworthy AK, Mirnics K. Molecular consequences of altered neuronal cholesterol biosynthesis. J Neurosci Res 2009; 87:866-75. [PMID: 18951487 DOI: 10.1002/jnr.21917] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The first dedicated step in de novo cholesterol biosynthesis begins with formation of squalene and ends with the reduction of 7-dehydrocholesterol by 7-dehydrocholesterol reductase (Dhcr7) into cholesterol, which is an essential structural and signaling molecule. Mutations in the Dhcr7 gene lead to Smith-Lemli-Opitz syndrome (SLOS), which is characterized by developmental deformities, incomplete myelination, and mental retardation. To understand better the molecular consequences of Dhcr7 deficiency in neuronal tissue, we analyzed the effect of cholesterol deficiency on the transcriptome in Neuro2a cells. Transient down-regulation of Dhcr7 by siRNA led to altered expression of multiple molecules that play critical roles in intracellular signaling or vesicular transport or are inserted into membrane rafts (e.g. Egr1, Snx, and Adam19). A similar down-regulation was also observed in stable Dhrc7-shRNA-transfected cell lines, and the findings were verified by qPCR. Furthermore, we investigated the Dhcr7-deficient and control cells for the expression of several critical genes involved in lipid biosynthesis. Among these, fatty acid synthase, sterol-regulatory element binding protein 2, SREBF chaperone, site-1 protease, and squalene synthase showed a significant down-regulation, suggesting that, in a neuronal cell line, Dhcr7 is a potent regulator of lipid biosynthesis. Importantly, the gene expression changes were present in both lipid-containing and cholesterol-deficient media, suggesting that intrinsic cholesterol biosynthesis is necessary for normal neuronal function and cannot be supplemented from extrinsic sources.
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Affiliation(s)
- Zeljka Korade
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee 37232, USA.
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Abstract
The loss of nigral dopaminergic (DA) neurons in idiopathic Parkinson's disease (PD) is believed to result from interactions between genetic susceptibility and environmental factors. Evidence that inflammatory processes modulate PD risk comes from prospective studies that suggest that higher plasma concentrations of a number of proinflammatory cytokines correlate with an increased risk of developing PD and chronic nonsteroidal anti-inflammatory drug regimens reduce the incidence of PD. Although loss-of-function mutations in the parkin gene cause early-onset familial PD, Parkin-deficient (parkin-/-) mice do not display nigrostriatal pathway degeneration, suggesting that a genetic factor is not sufficient, and an environmental trigger may be needed to cause nigral DA neuron loss. To test the hypothesis that parkin-/- mice require an inflammatory stimulus to develop nigral DA neuron loss, low-dose lipopolysaccaride (LPS) was administered intraperitoneally for prolonged periods. Quantitative real-time PCR and immunofluorescence labeling of inflammatory markers indicated that this systemic LPS treatment regimen triggered persistent neuroinflammation in wild-type and parkin-/- mice. Although inflammatory and oxidative stress responses to the inflammation regimen did not differ significantly between the two genotypes, only parkin-/- mice displayed subtle fine-motor deficits and selective loss of DA neurons in substantia nigra. Therefore, our studies suggest that loss of Parkin function increases the vulnerability of nigral DA neurons to inflammation-related degeneration. This new model of nigral DA neuron loss may enable identification of early biomarkers of degeneration and aid in preclinical screening efforts to identify compounds that can halt or delay the progressive degeneration of the nigrostriatal pathway.
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Valasek MA, Repa JJ, Quan G, Dietschy JM, Turley SD. Inhibiting intestinal NPC1L1 activity prevents diet-induced increase in biliary cholesterol in Golden Syrian hamsters. Am J Physiol Gastrointest Liver Physiol 2008; 295:G813-22. [PMID: 18718997 PMCID: PMC2575918 DOI: 10.1152/ajpgi.90372.2008] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Niemann-Pick C1-like 1 (NPC1L1) facilitates the uptake of sterols into the enterocyte and is the target of the novel cholesterol absorption inhibitor, ezetimibe. These studies used the Golden Syrian hamster as a model to delineate the changes in the relative mRNA expression of NPC1L1 and other proteins that regulate sterol homeostasis in the enterocyte during and following cessation of ezetimibe treatment and also to address the clinically important question of whether the marked inhibition of cholesterol absorption alters biliary lipid composition. In hamsters fed a low-cholesterol, low-fat basal diet, the abundance of mRNA for NPC1L1 in the small intestine far exceeded that in other regions of the gastrointestinal tract, liver, and gallbladder. In the first study, female hamsters were fed the basal diet containing ezetimibe at doses up to 2.0 mg.day(-1).kg body wt(-1). At this dose, cholesterol absorption fell by 82%, fecal neutral sterol excretion increased by 5.3-fold, and hepatic and intestinal cholesterol synthesis increased more than twofold, but there were no significant changes in either fecal bile acid excretion or biliary lipid composition. The ezetimibe-induced changes in intestinal cholesterol handling were reversed when treatment was withdrawn. In a second study, male hamsters were given a diet enriched in cholesterol and safflower oil without or with ezetimibe. The lipid-rich diet raised the absolute and relative cholesterol levels in bile more than fourfold. This increase was largely prevented by ezetimibe. These data are consistent with the recent finding that ezetimibe treatment significantly reduced biliary cholesterol saturation in patients with gallstones.
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Affiliation(s)
- Mark A. Valasek
- Departments of Internal Medicine and Physiology, University of Texas Southwestern Medical School, Dallas, Texas
| | - Joyce J. Repa
- Departments of Internal Medicine and Physiology, University of Texas Southwestern Medical School, Dallas, Texas
| | - Gang Quan
- Departments of Internal Medicine and Physiology, University of Texas Southwestern Medical School, Dallas, Texas
| | - John M. Dietschy
- Departments of Internal Medicine and Physiology, University of Texas Southwestern Medical School, Dallas, Texas
| | - Stephen D. Turley
- Departments of Internal Medicine and Physiology, University of Texas Southwestern Medical School, Dallas, Texas
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49
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Korade Z, Kenchappa RS, Mirnics K, Carter BD. NRIF is a regulator of neuronal cholesterol biosynthesis genes. J Mol Neurosci 2008; 38:152-8. [PMID: 18677445 DOI: 10.1007/s12031-008-9136-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Accepted: 07/09/2008] [Indexed: 11/30/2022]
Abstract
Cholesterol is a critical component of neuronal membranes, required for normal signal transduction. We showed previously that adult hippocampal neurons co-express high levels of cholesterogenic enzymes, and that their expression is under the control of the p75 neurotrophin receptor (p75NTR). Most of the cellular effects of p75NTR are mediated via interacting proteins, including neurotrophin receptor interacting factor (NRIF). In this study, we tested the hypothesis that p75NTR-dependent regulation of cholesterol and lipid biosynthesis genes is mediated by NRIF. We found that in vitro down regulation of NRIF expression decreased the mRNA for two main cholesterogenic enzymes, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (Hmgcr; EC 2.3.3.10) and 7-dehydrocholesterol reductase (Dhcr7; EC 1.3.1.21). Further analyses revealed that NRIF-dependent and Dhcr7-dependent transcriptional changes show a high degree of overlap, and that NRIF reduction resulted in reduced expression of sterol-sensing domain protein SCAP, followed by a decrease in mRNA levels of SRE-motif containing genes (HMGCR, FASN, SREBP2, S1P, and SQS1). Finally, a reduction in cholesterol biosynthesis-related gene expression was also observed in hippocampal tissue of mice with NRIF deletion. Our combined in vitro and in vivo studies suggest that hippocampal neuronal cholesterol biosynthesis is regulated through the p75NTR interacting factor NRIF.
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Affiliation(s)
- Zeljka Korade
- Department of Biochemistry, Vanderbilt University School of Medicine, 8124A MRB III, Nashville, TN 37232, USA.
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50
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Chuang JC, Cha JY, Garmey JC, Mirmira RG, Repa JJ. Research resource: nuclear hormone receptor expression in the endocrine pancreas. Mol Endocrinol 2008; 22:2353-63. [PMID: 18669644 DOI: 10.1210/me.2007-0568] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The endocrine pancreas comprises the islets of Langerhans, tiny clusters of cells that contribute only about 2% to the total pancreas mass. However, this little endocrine organ plays a critical role in maintaining glucose homeostasis by the regulated secretion of insulin (by beta-cells) and glucagon (by alpha-cells). The rapid increase in the incidence of diabetes worldwide has spurred renewed interest in islet cell biology. Some of the most widely prescribed oral drugs for treating type 2 diabetes include agents that bind and activate the nuclear hormone receptor, peroxisome proliferator-activated receptor-gamma. As a first step in addressing potential roles of peroxisome proliferator-activated receptor-gamma and other nuclear hormone receptors (NHRs) in the biology of the endocrine pancreas, we have used quantitative real-time PCR to profile the expression of all 49 members of the mouse NHR superfamily in primary islets, and cell lines that represent alpha-cells (alphaTC1) and beta-cells (betaTC6 and MIN6). In summary, 19 NHR members were highly expressed in both alpha- and beta-cell lines, 13 receptors showed predominant expression (at least an 8-fold difference) in alpha- vs. beta-cell lines, and 10 NHRs were not expressed in the endocrine pancreas. In addition we evaluated the relative expression of these transcription factors during hyperglycemia and found that 16 NHRs showed significantly altered mRNA levels in mouse islets. A similar survey was conducted in primary human islets to reveal several significant differences in NHR expression between mouse and man. These data identify potential therapeutic targets in the endocrine pancreas for the treatment of diabetes mellitus.
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Affiliation(s)
- Jen-Chieh Chuang
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9077, USA
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