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Lee JK, Kamran H, Lee KY. L-asparaginase induces IP3R-mediated ER Ca 2+ release by targeting µ-OR1 and PAR2 and kills acute lymphoblastic leukemia cells. Cell Death Discov 2024; 10:366. [PMID: 39147734 PMCID: PMC11327372 DOI: 10.1038/s41420-024-02142-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 08/06/2024] [Accepted: 08/08/2024] [Indexed: 08/17/2024] Open
Abstract
L-asparaginase is a standard therapeutic option for acute lymphoblastic leukemia (aLL), a hematologic cancer that claims the most lives of pediatric cancer patients. Previously, we demonstrated that L-asparaginase kills aLL cells via a lethal rise in [Ca2+]i due to IP3R-mediated ER Ca2+ release followed by calpain-1-Bid-caspase-3/12 activation (Blood, 133, 2222-2232). However, upstream targets of L-asparaginase that trigger IP3R-mediated ER Ca2+ release remain elusive. Here, we show that L-asparaginase targets µ-OR1 and PAR2 and induces IP3R-mediated ER Ca2+ release in aLL cells. In doing so, µ-OR1 plays a major role while PAR2 plays a minor role. Utilizing PAR2- and µ-OR1-knockdown cells, we demonstrate that L-asparaginase stimulation of µ-OR1 and PAR2 relays its signal via Gαi and Gαq, respectively. In PAR2-knockdown cells, stimulation of adenylate cyclase with forskolin or treatment with 8-CPT-cAMP reduces L-asparaginase-induced µ-OR1-mediated ER Ca2+ release, suggesting that activation of µ-OR1 negatively regulates AC and cAMP. In addition, the PKA inhibitor 14-22 amide (myr) alone evokes ER Ca2+ release, and subsequent L-asparaginase treatment does not induce further ER Ca2+ release, indicating the involvement of PKA inhibition in L-asparaginase-induced µ-OR1-mediated ER Ca2+ release, which can bypass the L-asparaginase-µ-OR1-AC-cAMP loop. This coincides with (a) the decreases in PKA-dependent inhibitory PLCβ3 Ser1105 phosphorylation, which prompts PLCβ3 activation and ER Ca2+ release, and (b) BAD Ser118 phosphorylation, which leads to caspase activation and apoptosis. Thus, our findings offer new insights into the Ca2+-mediated mechanisms behind L-asparaginase-induced aLL cell apoptosis and suggest that PKA may be targeted for therapeutic intervention for aLL.
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Affiliation(s)
- Jung Kwon Lee
- Department of Cell Biology & Anatomy, Arnie Charbonneau Cancer and Alberta Children's Hospital Research Institutes, University of Calgary, Calgary, AB, Canada
| | - Hamza Kamran
- Department of Cell Biology & Anatomy, Arnie Charbonneau Cancer and Alberta Children's Hospital Research Institutes, University of Calgary, Calgary, AB, Canada
| | - Ki-Young Lee
- Department of Cell Biology & Anatomy, Arnie Charbonneau Cancer and Alberta Children's Hospital Research Institutes, University of Calgary, Calgary, AB, Canada.
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Neurotrophin Signaling Impairment by Viral Infections in the Central Nervous System. Int J Mol Sci 2022; 23:ijms23105817. [PMID: 35628626 PMCID: PMC9146244 DOI: 10.3390/ijms23105817] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 05/15/2022] [Accepted: 05/17/2022] [Indexed: 02/04/2023] Open
Abstract
Neurotrophins, such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin 3 (NT-3), NT-4, and NT-5, are proteins involved in several important functions of the central nervous system. The activation of the signaling pathways of these neurotrophins, or even by their immature form, pro-neurotrophins, starts with their recognition by cellular receptors, such as tropomyosin receptor kinase (Trk) and 75 kD NT receptors (p75NTR). The Trk receptor is considered to have a high affinity for attachment to specific neurotrophins, while the p75NTR receptor has less affinity for attachment with neurotrophins. The correct functioning of these signaling pathways contributes to proper brain development, neuronal survival, and synaptic plasticity. Unbalanced levels of neurotrophins and pro-neurotrophins have been associated with neurological disorders, illustrating the importance of these molecules in the central nervous system. Furthermore, reports have indicated that viruses can alter the normal levels of neurotrophins by interfering with their signaling pathways. This work discusses the importance of neurotrophins in the central nervous system, their signaling pathways, and how viruses can affect them.
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In Vivo Models and In Vitro Assays for the Assessment of Pertussis Toxin Activity. Toxins (Basel) 2021; 13:toxins13080565. [PMID: 34437436 PMCID: PMC8402560 DOI: 10.3390/toxins13080565] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/04/2021] [Accepted: 08/05/2021] [Indexed: 01/07/2023] Open
Abstract
One of the main virulence factors produced by Bordetella pertussis is pertussis toxin (PTx) which, in its inactivated form, is the major component of all marketed acellular pertussis vaccines. PTx ADP ribosylates Gαi proteins, thereby affecting the inhibition of adenylate cyclases and resulting in the accumulation of cAMP. Apart from this classical model, PTx also activates some receptors and can affect various ADP ribosylation- and adenylate cyclase-independent signalling pathways. Due to its potent ADP-ribosylation properties, PTx has been used in many research areas. Initially the research primarily focussed on the in vivo effects of the toxin, including histamine sensitization, insulin secretion and leukocytosis. Nowadays, PTx is also used in toxicology research, cell signalling, research involving the blood–brain barrier, and testing of neutralizing antibodies. However, the most important area of use is testing of acellular pertussis vaccines for the presence of residual PTx. In vivo models and in vitro assays for PTx often reflect one of the toxin’s properties or details of its mechanism. Here, the established and novel in vivo and in vitro methods used to evaluate PTx are reviewed, their mechanisms, characteristics and limitations are described, and their application for regulatory and research purposes are considered.
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Intracellular Trafficking and Translocation of Pertussis Toxin. Toxins (Basel) 2019; 11:toxins11080437. [PMID: 31349590 PMCID: PMC6723225 DOI: 10.3390/toxins11080437] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Accepted: 07/24/2019] [Indexed: 12/25/2022] Open
Abstract
Pertussis toxin (PT) is a multimeric complex of six proteins. The PTS1 subunit is an ADP-ribosyltransferase that inactivates the alpha subunit of heterotrimeric Gi/o proteins. The remaining PT subunits form a pentamer that positions PTS1 in and above the central cavity of the triangular structure. Adhesion of this pentamer to glycoprotein or glycolipid conjugates on the surface of a target cell leads to endocytosis of the PT holotoxin. Vesicle carriers then deliver the holotoxin to the endoplasmic reticulum (ER) where PTS1 dissociates from the rest of the toxin, unfolds, and exploits the ER-associated degradation pathway for export to the cytosol. Refolding of the cytosolic toxin allows it to regain an active conformation for the disruption of cAMP-dependent signaling events. This review will consider the intracellular trafficking of PT and the order-disorder-order transitions of PTS1 that are essential for its cellular activity.
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5
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Di Liberto V, Mudò G, Belluardo N. Crosstalk between receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCR) in the brain: Focus on heteroreceptor complexes and related functional neurotrophic effects. Neuropharmacology 2018; 152:67-77. [PMID: 30445101 DOI: 10.1016/j.neuropharm.2018.11.018] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Revised: 11/01/2018] [Accepted: 11/12/2018] [Indexed: 01/11/2023]
Abstract
Neuronal events are regulated by the integration of several complex signaling networks in which G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) are considered key players of an intense bidirectional cross-communication in the cell, generating signaling mechanisms that, at the same time, connect and diversify the traditional signal transduction pathways activated by the single receptor. For this receptor-receptor crosstalk, the two classes of receptors form heteroreceptor complexes resulting in RTKs transactivation and in growth-promoting signals. In this review, we describe heteroreceptor complexes between GPCR and RTKs in the central nervous system (CNS) and their functional effects in controlling a variety of neuronal effects, ranging from development, proliferation, differentiation and migration, to survival, repair, synaptic transmission and plasticity. In this interaction, RTKs can also recruit components of the G protein signaling cascade, creating a bidirectional intricate interplay that provides complex control over multiple cellular events. These heteroreceptor complexes, by the integration of different signals, have recently attracted a growing interest as novel molecular target for depressive disorders. This article is part of the Special Issue entitled 'Receptor heteromers and their allosteric receptor-receptor interactions'.
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Affiliation(s)
- Valentina Di Liberto
- Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Palermo, Italy
| | - Giuseppa Mudò
- Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Palermo, Italy
| | - Natale Belluardo
- Department of Experimental Biomedicine and Clinical Neurosciences, University of Palermo, Palermo, Italy.
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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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Sierra-Fonseca JA, Najera O, Martinez-Jurado J, Walker EM, Varela-Ramirez A, Khan AM, Miranda M, Lamango NS, Roychowdhury S. Nerve growth factor induces neurite outgrowth of PC12 cells by promoting Gβγ-microtubule interaction. BMC Neurosci 2014; 15:132. [PMID: 25552352 PMCID: PMC4302597 DOI: 10.1186/s12868-014-0132-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 11/27/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Assembly and disassembly of microtubules (MTs) is critical for neurite outgrowth and differentiation. Evidence suggests that nerve growth factor (NGF) induces neurite outgrowth from PC12 cells by activating the receptor tyrosine kinase, TrkA. G protein-coupled receptors (GPCRs) as well as heterotrimeric G proteins are also involved in regulating neurite outgrowth. However, the possible connection between these pathways and how they might ultimately converge to regulate the assembly and organization of MTs during neurite outgrowth is not well understood. RESULTS Here, we report that Gβγ, an important component of the GPCR pathway, is critical for NGF-induced neuronal differentiation of PC12 cells. We have found that NGF promoted the interaction of Gβγ with MTs and stimulated MT assembly. While Gβγ-sequestering peptide GRK2i inhibited neurite formation, disrupted MTs, and induced neurite damage, the Gβγ activator mSIRK stimulated neurite outgrowth, which indicates the involvement of Gβγ in this process. Because we have shown earlier that prenylation and subsequent methylation/demethylation of γ subunits are required for the Gβγ-MTs interaction in vitro, small-molecule inhibitors (L-28 and L-23) targeting prenylated methylated protein methyl esterase (PMPMEase) were tested in the current study. We found that these inhibitors disrupted Gβγ and ΜΤ organization and affected cellular morphology and neurite outgrowth. In further support of a role of Gβγ-MT interaction in neuronal differentiation, it was observed that overexpression of Gβγ in PC12 cells induced neurite outgrowth in the absence of added NGF. Moreover, overexpressed Gβγ exhibited a pattern of association with MTs similar to that observed in NGF-differentiated cells. CONCLUSIONS Altogether, our results demonstrate that βγ subunit of heterotrimeric G proteins play a critical role in neurite outgrowth and differentiation by interacting with MTs and modulating MT rearrangement.
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Affiliation(s)
- Jorge A Sierra-Fonseca
- />Neuromodulation Disorders Cluster, Border Biomedical Research Center, University of Texas, El Paso, TX 79968 USA
- />Department of Biological Sciences, University of Texas, El Paso, TX 79968 USA
- />Present Address: Department of Pathology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115 USA
| | - Omar Najera
- />Neuromodulation Disorders Cluster, Border Biomedical Research Center, University of Texas, El Paso, TX 79968 USA
- />Department of Biological Sciences, University of Texas, El Paso, TX 79968 USA
| | - Jessica Martinez-Jurado
- />Neuromodulation Disorders Cluster, Border Biomedical Research Center, University of Texas, El Paso, TX 79968 USA
- />Department of Biological Sciences, University of Texas, El Paso, TX 79968 USA
| | - Ellen M Walker
- />Neuromodulation Disorders Cluster, Border Biomedical Research Center, University of Texas, El Paso, TX 79968 USA
- />Department of Biological Sciences, University of Texas, El Paso, TX 79968 USA
| | - Armando Varela-Ramirez
- />Cytometry Screening and Imaging Core facility, Border Biomedical Research Center, University of Texas, El Paso, TX 79968 USA
- />Department of Biological Sciences, University of Texas, El Paso, TX 79968 USA
| | - Arshad M Khan
- />Neuromodulation Disorders Cluster, Border Biomedical Research Center, University of Texas, El Paso, TX 79968 USA
- />Department of Biological Sciences, University of Texas, El Paso, TX 79968 USA
| | - Manuel Miranda
- />Neuromodulation Disorders Cluster, Border Biomedical Research Center, University of Texas, El Paso, TX 79968 USA
- />Department of Biological Sciences, University of Texas, El Paso, TX 79968 USA
| | - Nazarius S Lamango
- />College of Pharmacy and Pharmaceutical Sciences, Florida A&M University, Tallahassee, FL 32307 USA
| | - Sukla Roychowdhury
- />Neuromodulation Disorders Cluster, Border Biomedical Research Center, University of Texas, El Paso, TX 79968 USA
- />Department of Biological Sciences, University of Texas, El Paso, TX 79968 USA
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Seaborn T, Ravni A, Au R, Chow BKC, Fournier A, Wurtz O, Vaudry H, Eiden LE, Vaudry D. Induction of serpinb1a by PACAP or NGF is required for PC12 cells survival after serum withdrawal. J Neurochem 2014; 131:21-32. [PMID: 24899316 DOI: 10.1111/jnc.12780] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 04/30/2014] [Accepted: 05/13/2014] [Indexed: 01/11/2023]
Abstract
PC12 cells are used to study the signaling mechanisms underlying the neurotrophic and neuroprotective activities of pituitary adenylate cyclase-activating polypeptide (PACAP) and nerve growth factor (NGF). Previous microarray experiments indicated that serpinb1a was the most induced gene after 6 h of treatment with PACAP or NGF. This study confirmed that serpinb1a is strongly activated by PACAP and NGF in a time-dependent manner with a maximum induction (~ 50-fold over control) observed after 6 h of treatment. Co-incubation with PACAP and NGF resulted in a synergistic up-regulation of serpinb1a expression (200-fold over control), suggesting that PACAP and NGF act through complementary mechanisms. Consistently, PACAP-induced serpinb1a expression was not blocked by TrkA receptor inhibition. Nevertheless, the stimulation of serpinb1a expression by PACAP and NGF was significantly reduced in the presence of extracellular signal-regulated kinase, calcineurin, protein kinase A, p38, and PI3K inhibitors, indicating that the two trophic factors share some common pathways in the regulation of serpinb1a. Finally, functional investigations conducted with siRNA revealed that serpinb1a is not involved in the effects of PACAP and NGF on PC12 cell neuritogenesis, proliferation or body cell volume but mediates their ability to block caspases 3/7 activity and to promote PC12 cell survival.
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Affiliation(s)
- Tommy Seaborn
- Neurotrophic Factor and Neuronal Differentiation Team, Inserm U982, DC2N, Mont-Saint-Aignan, France; International Associated Laboratory Samuel de Champlain, Mont-Saint-Aignan, France; Department of Pediatrics, Hôpital St-François d'Assise, Centre de Recherche du Centre Hospitalier Universitaire de Québec (CRCHUQ), Laval University, Québec, Canada
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Wang YC, Xia QJ, Ba YC, Wang TY, LiN N, Zou Y, Shang FF, Zhou XF, Wang TH, Fu XM, Qi JG. Transplantation of olfactory ensheathing cells promotes the recovery of neurological functions in rats with traumatic brain injury associated with downregulation of Bad. Cytotherapy 2014; 16:1000-10. [DOI: 10.1016/j.jcyt.2013.12.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 12/07/2013] [Accepted: 12/26/2013] [Indexed: 10/25/2022]
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10
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Kwan DHT, Yung LY, Ye RD, Wong YH. Activation of Ras-dependent signaling pathways by G(14) -coupled receptors requires the adaptor protein TPR1. J Cell Biochem 2013; 113:3486-97. [PMID: 22711498 DOI: 10.1002/jcb.24225] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Many G(q) -coupled receptors mediate mitogenic signals by stimulating extracellular signal-regulated protein kinases (ERKs) that are typically regulated by the small GTPase Ras. Recent studies have revealed that members of the Gα(q) family may possess the ability to activate Ras/ERK by interacting with the adaptor protein tetratricopeptide repeat 1 (TPR1). Within the Gα(q) family, the highly promiscuous Gα(14) can relay signals from numerous receptors. Here, we examined if Gα(14) interacts with TPR1 to stimulate Ras signaling pathways. Expression of the constitutively active Gα(14) QL mutant in HEK293 cells led to the formation of GTP-bound Ras as well as increased phosphorylations of downstream signaling molecules including ERK and IκB kinase. Stimulation of endogenous G(14) -coupled somatostatin type 2 and α(2) -adrenergic receptors produced similar responses in human hepatocellular HepG2 carcinoma cells. Co-immunoprecipitation assays using HEK293 cells demonstrated a stronger association of TPR1 for Gα(14) QL than Gα(14) , suggesting that TPR1 preferentially binds to the GTP-bound form of Gα(14) . Activated Gα(14) also interacted with the Ras guanine nucleotide exchange factors SOS1 and SOS2. Expression of a dominant negative mutant of TPR1 or siRNA-mediated knockdown of TPR1 effectively abolished the ability of Gα(14) to induce Ras signaling in native HepG2 or transfected HEK293 cells. Although expression of the dominant negative mutant of TPR1 suppressed Gα(14) QL-induced phosphorylations of ERK and IκB kinase, it did not affect Gα(14) QL-induced stimulation of phospholipase Cβ or c-Jun N-terminal kinase. Our results suggest that TPR1 is required for Gα(14) to stimulate Ras-dependent signaling pathways, but not for the propagation of signals along Ras-independent pathways.
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Affiliation(s)
- Dawna H T Kwan
- Division of Life Science and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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11
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Apelin–APJ induces ICAM-1, VCAM-1 and MCP-1 expression via NF-κB/JNK signal pathway in human umbilical vein endothelial cells. Amino Acids 2012; 43:2125-36. [DOI: 10.1007/s00726-012-1298-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 04/06/2012] [Indexed: 12/11/2022]
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12
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Hwang SL, Lin JA, Shih PH, Yeh CT, Yen GC. Pro-cellular survival and neuroprotection of citrus flavonoid: the actions of hesperetin in PC12 cells. Food Funct 2012; 3:1082-90. [DOI: 10.1039/c2fo30100h] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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13
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RGS19 stimulates cell proliferation by deregulating cell cycle control and enhancing Akt signaling. Cancer Lett 2011; 309:199-208. [DOI: 10.1016/j.canlet.2011.06.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Revised: 05/09/2011] [Accepted: 06/01/2011] [Indexed: 11/13/2022]
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Pyne NJ, Pyne S. Receptor tyrosine kinase-G-protein-coupled receptor signalling platforms: out of the shadow? Trends Pharmacol Sci 2011; 32:443-50. [PMID: 21612832 DOI: 10.1016/j.tips.2011.04.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Revised: 04/20/2011] [Accepted: 04/26/2011] [Indexed: 12/29/2022]
Abstract
Receptor tyrosine kinases (RTKs) and G-protein-coupled receptors (GPCRs) can form platforms in which protein signalling components specific for each receptor are shared (owing to close proximity) to produce an integrated response upon engagement of ligands. RTK-GPCR signalling platforms respond to growth factors and GPCR agonists to increase gain over and above that which is normally produced by separate receptors. They can also function to change the spatial context of signalling in response to growth factor activation. The function of RTK-GPCR signalling platforms can be modulated with conformational-specific inhibitors that stabilise defined GPCR states to abrogate both GPCR agonist- and growth factor-stimulated cell responses. In this paper, we provide an opinion of the biology and unusual pharmacology of RTK-GPCR signalling platforms and make comparisons with a more traditional model of crosstalk between RTKs and GPCRs.
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Affiliation(s)
- Nigel J Pyne
- Cell Biology Group, Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow, G4 0RE, UK.
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Neurosteroid dehydroepiandrosterone interacts with nerve growth factor (NGF) receptors, preventing neuronal apoptosis. PLoS Biol 2011; 9:e1001051. [PMID: 21541365 PMCID: PMC3082517 DOI: 10.1371/journal.pbio.1001051] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Accepted: 03/15/2011] [Indexed: 12/02/2022] Open
Abstract
The neurosteroid dehydroepiandrosterone (DHEA), produced by neurons and glia, affects multiple processes in the brain, including neuronal survival and neurogenesis during development and in aging. We provide evidence that DHEA interacts with pro-survival TrkA and pro-death p75NTR membrane receptors of neurotrophin nerve growth factor (NGF), acting as a neurotrophic factor: (1) the anti-apoptotic effects of DHEA were reversed by siRNA against TrkA or by a specific TrkA inhibitor; (2) [3H]-DHEA binding assays showed that it bound to membranes isolated from HEK293 cells transfected with the cDNAs of TrkA and p75NTR receptors (KD: 7.4±1.75 nM and 5.6±0.55 nM, respectively); (3) immobilized DHEA pulled down recombinant and naturally expressed TrkA and p75NTR receptors; (4) DHEA induced TrkA phosphorylation and NGF receptor-mediated signaling; Shc, Akt, and ERK1/2 kinases down-stream to TrkA receptors and TRAF6, RIP2, and RhoGDI interactors of p75NTR receptors; and (5) DHEA rescued from apoptosis TrkA receptor positive sensory neurons of dorsal root ganglia in NGF null embryos and compensated NGF in rescuing from apoptosis NGF receptor positive sympathetic neurons of embryonic superior cervical ganglia. Phylogenetic findings on the evolution of neurotrophins, their receptors, and CYP17, the enzyme responsible for DHEA biosynthesis, combined with our data support the hypothesis that DHEA served as a phylogenetically ancient neurotrophic factor. Dehydroepiandrosterone (DHEA) and its sulphate ester are the most abundant steroid hormones in humans, and DHEA was described as the first neurosteroid produced in the brain. DHEA is known to participate in multiple events in the brain, including neuronal survival and neurogenesis. However, to date no specific cellular receptor has been described for this important neurosteroid. In this study, we provide evidence that DHEA exerts its neurotrophic effects by directly interacting with the TrkA and p75NTR membrane receptors of nerve growth factor (NGF), and efficiently activates their downstream signaling pathways. This activation prevents the apoptotic loss of NGF receptor positive sensory and sympathetic neurons. The interaction of DHEA with NGF receptors may also offer a mechanistic explanation for the multiple actions of DHEA in other peripheral biological systems expressing NGF receptors, such as the immune, reproductive, and cardiovascular systems.
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16
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RGS19 enhances cell proliferation through its C-terminal PDZ motif. Cell Signal 2010; 22:1700-7. [PMID: 20599498 DOI: 10.1016/j.cellsig.2010.06.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Accepted: 06/24/2010] [Indexed: 01/18/2023]
Abstract
Regulator of G protein signaling 19 (RGS19), also known as Galpha-interacting protein (GAIP), is a GTPase activating protein (GAP) for Galpha(i) subunits. Apart from its GAP function, RGS19 has been implicated in growth factor signaling through binding to GAIP-interacting protein C-terminus (GIPC) via its C-terminal PDZ-binding motif. To gain additional insight on its function, we have stably expressed RGS19 in a number of mammalian cell lines and examined its effect on cell proliferation. Interestingly, overexpression of RGS19 stimulated the growth of HEK293, PC12, Caco2, and NIH3T3 cells. This growth promoting effect was not shared by other RGS proteins including RGS4, RGS10 and RGS20. Despite its ability to stimulate cell proliferation, RGS19 failed to induce neoplastic transformation in NIH3T3 cells as determined by focus formation and soft-agar assays, and it did not induce tumor growth in athymic nude mice. Deletion mutants of RGS19 lacking the PDZ-binding motif failed to complex with GIPC and did not exhibit any growth promoting effect. Overexpression of GIPC alone in HEK293 cells stimulated cell proliferation whereas its knockdown in H1299 non-small cell lung carcinomas suppressed cell proliferation. This study demonstrates that RGS19, in addition to acting as a GAP, is able to stimulate cell proliferation in a GIPC-dependent manner.
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17
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Yanamadala V, Negoro H, Denker BM. Heterotrimeric G proteins and apoptosis: intersecting signaling pathways leading to context dependent phenotypes. Curr Mol Med 2009; 9:527-45. [PMID: 19601805 PMCID: PMC2822437 DOI: 10.2174/156652409788488784] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Apoptosis, a programmed cell death mechanism, is a fundamental process during the normal development and somatic maintenance of all multicellular organisms and thus is highly conserved and tightly regulated through numerous signaling pathways. Apoptosis is of particular clinical importance as its dysregulation contributes significantly to numerous human diseases, primarily through changes in the expression and activation of key apoptotic regulators. Each of the four families of heterotrimeric G proteins (G(s), G(i/o), G(q/11) and G(12/13)) has been implicated in numerous cellular signaling processes, including proliferation, transformation, migration, differentiation, and apoptosis. Heterotrimeric G protein signaling is an important but not widely studied mechanism regulating apoptosis. G protein Signaling and Apoptosis broadly cover two large bodies of literature and share numerous signaling pathways. Examination of the intersection between these two areas is the focus of this review. Several studies have implicated signaling through each of the four heterotrimeric G protein families to regulate apoptosis within numerous disease contexts, but the mechanism(s) are not well defined. Each G protein family has been shown to stimulate and/or inhibit apoptosis in a context-dependent fashion through regulating numerous downstream effectors including the Bcl-2 family, NF-kappaB, PI3 Kinase, MAP Kinases, and small GTPases. These cell-type specific and G protein coupled receptor dependent effects have led to a complex body of literature of G protein regulation of apoptosis. Here, we review the literature and summarize apoptotic signaling through each of the four heterotrimeric G protein families (and the relevant G protein coupled receptors), and discuss limitations and future directions for research on regulating apoptosis through G protein coupled mechanisms. Continued investigation in this field is essential for the identification of important targets for pharmacological intervention in numerous diseases.
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Affiliation(s)
- Vijay Yanamadala
- Renal Division, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA
| | - Hideyuki Negoro
- Renal Division, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA
| | - Bradley M. Denker
- Renal Division, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA
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18
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Abstract
G protein-coupled receptors (GPCRs) detect a great diversity of extracellular stimuli ranging from hormonal peptides, chemokines, neurotransmitters, lipids, nucleotides, amino acids, biogenic amines to ions. G protein-coupled pathways regulate a rich collection of biological processes involved in normal physiological function of the body as well as in pathological progression of diseases. In addition to their function in postmitotic steady-state tissues, GPCRs have been implicated in the differentiation of stem cells and tissue specific progenitor cells during development. Examples of these include the functions of nucleotides and neuropeptides in neuronal differentiation and axon growth, chemokines in lymphocyte differentiation and activation, and other GPCR-mediated processes in the differentiation of adipocytes, osteoblasts and smooth muscle cells. This review summarizes the recent advances in our understanding of the importance of GPCR-linked signaling cascades in the differentiation of different cell lineages.
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Affiliation(s)
- Kepeng Wang
- Department of Biochemistry, The Molecular Neuroscience Center, The Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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19
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Cao C, Huang X, Han Y, Wan Y, Birnbaumer L, Feng GS, Marshall J, Jiang M, Chu WM. Galpha(i1) and Galpha(i3) are required for epidermal growth factor-mediated activation of the Akt-mTORC1 pathway. Sci Signal 2009; 2:ra17. [PMID: 19401591 DOI: 10.1126/scisignal.2000118] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The precise mechanism whereby epidermal growth factor (EGF) activates the serine-threonine kinase Akt and the mammalian target of rapamycin (mTOR) complex 1 (mTORC1) remains elusive. Here, we report that the alpha subunits of the heterotrimeric guanine nucleotide-binding proteins (G proteins) Galpha(i1) and Galpha(i3) are critical for this activation process. Both Galpha(i1) and Galpha(i3) formed complexes with growth factor receptor binding 2 (Grb2)-associated binding protein 1 (Gab1) and the EGF receptor (EGFR) and were required for the phosphorylation of Gab1 and its subsequent interaction with the p85 subunit of phosphatidylinositol 3-kinase in response to EGF. Loss of Galpha(i1) and Galpha(i3) severely impaired the activation of Akt and of p70 S6 kinase and 4E-BP1, downstream targets of mTORC1, in response to EGF, heparin-binding EGF-like growth factor, and transforming growth factor alpha, but not insulin, insulin-like growth factor, or platelet-derived growth factor. In addition, ablation of Galpha(i1) and Galpha(i3) largely inhibited EGF-induced cell growth, migration, and survival and the accumulation of cyclin D1. Overall, this study suggests that Galpha(i1) and Galpha(i3) lie downstream of EGFR, but upstream of Gab1-mediated activation of Akt and mTORC1, thus revealing a role for Galpha(i) proteins in mediating EGFR signaling.
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Affiliation(s)
- Cong Cao
- Department of Molecular Microbiology and Immunology, Brown University, Providence, RI 02912, USA
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20
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Tso PH, Morris CJ, Yung LY, Ip NY, Wong YH. Multiple Gi Proteins Participate in Nerve Growth Factor-Induced Activation of c-Jun N-terminal Kinases in PC12 Cells. Neurochem Res 2008; 34:1101-12. [DOI: 10.1007/s11064-008-9880-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/23/2008] [Indexed: 01/21/2023]
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21
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Yung LY, Tso PH, Wu EH, Yu JC, Ip NY, Wong YH. Nerve growth factor-induced stimulation of p38 mitogen-activated protein kinase in PC12 cells is partially mediated via Gi/o proteins. Cell Signal 2008; 20:1538-44. [DOI: 10.1016/j.cellsig.2008.04.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Revised: 04/10/2008] [Accepted: 04/11/2008] [Indexed: 12/21/2022]
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22
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Obara Y, Okano Y, Ono S, Yamauchi A, Hoshino T, Kurose H, Nakahata N. Betagamma subunits of G(i/o) suppress EGF-induced ERK5 phosphorylation, whereas ERK1/2 phosphorylation is enhanced. Cell Signal 2008; 20:1275-83. [PMID: 18407464 DOI: 10.1016/j.cellsig.2008.02.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 02/22/2008] [Accepted: 02/22/2008] [Indexed: 10/22/2022]
Abstract
Extracellular signal-regulated kinases (ERKs) play important physiological roles in proliferation, differentiation and gene expression. ERK5 is twice the size of ERK1/2, the amino-terminal half contains the kinase domain that shares the homology with ERK1/2 and TEY activation motif, whereas the carboxy-terminal half is unique. In this study, we examined the cross-talk mechanism between G-protein-coupled receptors (GPCRs) and receptor tyrosine kinases, focusing on ERK1/2 and 5. The pretreatment of rat pheochromocytoma cells (PC12) with pertussis toxin (PTX) specifically enhanced epidermal growth factor (EGF)-induced ERK5 phosphorylation. In addition, lysophosphatidic acid (LPA) attenuated the EGF-induced ERK5 phosphorylation in LPA(1) receptor- and G(i/o)-dependent manners. On the other hand, LPA alone activated ERK1/2 via Gbetagamma subunits and Ras and potentiated EGF-induced ERK1/2 phosphorylation at late time points. These results suggest G(i/o) negatively regulates ERK5, while it positively regulates ERK1/2. LPA did not affect cAMP levels after EGF treatment, and the reagents promoting cAMP production such as forskolin and cholera toxin also attenuated the EGF-induced ERK5 phosphorylation, indicating that the inhibitory effect of LPA on ERK5 inhibition via G(i/o) is not due to inhibition of adenylyl cyclase by Galpha(i/o). However, the inhibitory effect of LPA on ERK5 was abolished in PC12 cells stably overexpressing C-terminus of GPCR kinase2 (GRK2), and overexpression of Gbeta(1) and gamma(2) subunits also suppressed ERK5 phosphorylation by EGF. In response to LPA, Gbetagamma subunits interacted with EGF receptor in a time-dependent manner. These results strongly suggest that LPA negatively regulates the EGF-induced ERK5 phosphorylation through Gbetagamma subunits.
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Affiliation(s)
- Yutaro Obara
- Department of Cellular Signaling, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
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23
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Park SW, He Y, Ha SG, Loh HH, Wei LN. Epigenetic regulation of kappa opioid receptor gene in neuronal differentiation. Neuroscience 2008; 151:1034-41. [PMID: 18201839 DOI: 10.1016/j.neuroscience.2007.12.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Revised: 12/03/2007] [Accepted: 12/07/2007] [Indexed: 01/09/2023]
Abstract
The gene of mouse kappa opioid receptor (KOR) utilizes two promoters, P1 and P2. P1 is active in various brain areas and constitutively in P19 mouse embryonal carcinoma cells. P2 is active in limited brain stem areas of adult animals and only in late differentiated cells of P19 induced for neuronal differentiation in the presence of nerve growth factor (NGF). NGF response of P2 was found to be mediated by a specific binding site for transcription factor activation protein 2 (AP2) located in P2. Electrophoretic gel shift assay showed specific binding of this AP2 site by AP2beta, but not AP2alpha. Knockdown of endogenous AP2beta with siRNA abolished the stimulating effect of NGF on the expression of transcripts driven by P2. Binding of endogenous AP2beta on the endogenous KOR P2 chromatin region was also confirmed by chromatin immunoprecipitation. The effect of NGF was inhibited by LY2942002 (phosphatidylinositol 3-kinase, PI3K inhibitor), suggesting that PI3K was involved in signaling pathway mediating the effect of NGF stimulation on KOR P2. The chromatin of P2 in P19 was found to be specifically modified following NGF stimulation, which included demethylation at Lys9 and dimethylation at Lys4 of histone H3 and was consistent with the increased recruitment of RNA polymerase II to this promoter. This study presents the first evidence for epigenetic changes occurred on a specific KOR promoter triggered by NGF in cells undergoing neuronal differentiation. This epigenetic change is mediated by recruited AP2beta to this promoter and involves the PI3K system.
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Affiliation(s)
- S W Park
- Department of Pharmacology, University of Minnesota Medical School, 6-120 Jackson Hall, 321 Church Street Southeast, Minneapolis, MN 55455, USA
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24
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Wu EHT, Wu KKH, Wong YH. Tuberin: a stimulus-regulated tumor suppressor protein controlled by a diverse array of receptor tyrosine kinases and G protein-coupled receptors. Neurosignals 2007; 15:217-27. [PMID: 17389815 DOI: 10.1159/000101333] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Accepted: 02/09/2007] [Indexed: 02/02/2023] Open
Abstract
Tuberin, a tumor suppressor protein, is involved in various cellular functions including survival, proliferation, and growth. It has emerged as an important effector regulated by receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCRs). Regulation of tuberin by RTKs and GPCRs is highly complex and dependent on the type of receptors and their associated signaling molecules. Apart from Akt, the first kinase recognized to phosphorylate and inactivate tuberin upon growth factor stimulation, an increasing number of kinases upstream of tuberin have been identified. Furthermore, recruitment of different scaffolding adaptor components to the activated receptors appears to play an important role in the regulation of tuberin activity. More recently, the differential regulation of tuberin by various G protein family members have also been intensively studied, it appears that G proteins can both facilitate (e.g., G(i/o)) as well as inhibit (e.g., G(q)) tuberin phosphorylation. In the present review, we attempt to summarize our emerging understandings of the roles of RTKs, GPCRs, and their cross-talk on the regulation of tuberin.
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Affiliation(s)
- Eddy H T Wu
- Department of Biochemistry, Molecular Neuroscience Center, and Biotechnology Research Institute, Hong Kong University of Science and Technology, Hong Kong, SAR, China
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25
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El Zein N, Badran BM, Sariban E. The neuropeptide pituitary adenylate cyclase activating protein stimulates human monocytes by transactivation of the Trk/NGF pathway. Cell Signal 2007; 19:152-62. [PMID: 16914291 DOI: 10.1016/j.cellsig.2006.05.031] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Revised: 05/17/2006] [Accepted: 05/17/2006] [Indexed: 11/18/2022]
Abstract
Transactivation is a process whereby stimulation of G-protein-coupled receptors (GPCR) activates signaling from receptors tyrosine kinase (RTK). In neuronal cells, the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) acting through the GPCR VPAC-1 exerts trophic effects by transactivating the RTK TrkA receptor for the nerve growth factor (NGF). Both PACAP and NGF have pro-inflammatory activities on monocytes. We have tested the possibility that in monocytes, PACAP, as reported in neuronal cells, uses NGF/TrkA signaling pathway. In these cells, PACAP increases TrkA tyrosine phosphorylations through a PI-3kinase dependent but phospholipase C independent pathway. K252a, an inhibitor of TrkA decreases PACAP-induced Akt and ERK phosphorylation and calcium mobilisation resulting in decreases in intracellular H2O2 production and membrane upregulation of CD11b expression, both functions being inhibited after anti-NGF or anti-TrkA antibody treatment. K252a also inhibits PACAP-associated NF-KB activity. Monocytes increase in NGF production is seen after micromolar PACAP exposure while nanomolar treatment which desensitizes cells to high dose of PACAP prevents PACAP-induced TrkA phosphorylation, H2O2 production and CD11b expression. Finally, NGF-dependent ERK activation and H2O2 production is pertussis toxin sensitive. Altogether these data indicate that in PACAP-activated monocytes some pro-inflammatory activities occur through transactivation mechanisms involving VPAC-1, NGF and TrkA-associated tyrosine kinase activity.
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Affiliation(s)
- Nabil El Zein
- Laboratory of Pediatric Oncology, Hôpital des Enfants, 1020 Brussels, Belgium
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26
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Hobson SA, Holmes FE, Kerr NCH, Pope RJP, Wynick D. Mice deficient for galanin receptor 2 have decreased neurite outgrowth from adult sensory neurons and impaired pain-like behaviour. J Neurochem 2006; 99:1000-10. [PMID: 17076662 PMCID: PMC2725756 DOI: 10.1111/j.1471-4159.2006.04143.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Expression of the neuropeptide galanin is markedly up-regulated within the adult dorsal root ganglia (DRG) following peripheral nerve injury. We have previously demonstrated that galanin knockout (Gal-KO) mice have a developmental loss of a subset of DRG neurons. Galanin also plays a trophic role in the adult animal, and the rate of peripheral nerve regeneration and neurite outgrowth is reduced in adult Gal-KO mice. Here we describe the characterization of mice with an absence of GalR2 gene transcription (GalR2-MUT) and demonstrate that they have a 15% decrease in the number of calcitonin gene-related peptide (CGRP) expressing neuronal profiles in the adult DRG, associated with marked deficits in neuropathic and inflammatory pain behaviours. Adult GalR2-MUT animals also have a one third reduction in neurite outgrowth from cultured DRG neurons that cannot be rescued by either galanin or a high-affinity GalR2/3 agonist. Galanin activates extracellular signal-regulated kinase (ERK) and Akt in adult wild-type (WT) mouse DRG. Intact adult DRG from GalR2-MUT animals have lower levels of pERK and higher levels of pAkt than are found in WT controls. These data suggest that a lack of GalR2 activation in Gal-KO and GalR2-MUT animals is responsible for the observed developmental deficits in the DRG, and the decrease in neurite outgrowth in the adult.
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MESH Headings
- Animals
- Behavior, Animal/physiology
- Blotting, Western
- Extracellular Signal-Regulated MAP Kinases/metabolism
- Genotype
- Immunohistochemistry
- Male
- Mice
- Mice, Knockout
- Neurites/physiology
- Neurons, Afferent/physiology
- Pain/genetics
- Pain/psychology
- Peripheral Nerve Injuries
- Phenotype
- Phosphorylation
- Proto-Oncogene Proteins c-akt/physiology
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Receptor, Galanin, Type 2/genetics
- Receptor, Galanin, Type 2/physiology
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction/genetics
- Signal Transduction/physiology
- Transcription, Genetic
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Affiliation(s)
- Sally-Ann Hobson
- Departments of Pharmacology and Clinical Science at South Bristol, Bristol University, Bristol, UK
| | - Fiona E. Holmes
- Departments of Pharmacology and Clinical Science at South Bristol, Bristol University, Bristol, UK
| | - Niall C. H. Kerr
- Departments of Pharmacology and Clinical Science at South Bristol, Bristol University, Bristol, UK
| | - Robert J. P. Pope
- Departments of Pharmacology and Clinical Science at South Bristol, Bristol University, Bristol, UK
| | - David Wynick
- Departments of Pharmacology and Clinical Science at South Bristol, Bristol University, Bristol, UK
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27
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Moughal NA, Waters CM, Valentine WJ, Connell M, Richardson JC, Tigyi G, Pyne S, Pyne NJ. Protean agonism of the lysophosphatidic acid receptor-1 with Ki16425 reduces nerve growth factor-induced neurite outgrowth in pheochromocytoma 12 cells. J Neurochem 2006; 98:1920-9. [PMID: 16945108 DOI: 10.1111/j.1471-4159.2006.04009.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report here a novel role for the constitutively active lysophosphatidic acid receptor-1 (LPA(1)) receptor in providing Gbetagamma subunits for use by the Trk A receptor. This enhances the ability of nerve growth factor (NGF) to promote signalling and cell response. These conclusions were based on three lines of evidence. Firstly, the LPA(1) receptor was co-immunoprecipitated with the Trk A receptor from lysates, suggesting that these proteins form a complex. Secondly, Ki16425, a selective protean agonist of the LPA(1) receptor, decreased constitutive basal and LPA-induced LPA(1) receptor-stimulated GTPgammaS binding. Ki16425 reduced the LPA-induced activation of p42/p44 mitogen activated protein kinase (MAPK), while acting as a weak stimulator of p42/p44 MAPK on its own, properties typical of a protean agonist. Significantly, Ki16425 also reduced the NGF-induced stimulation of p42/p44 MAPK and inhibited NGF-stimulated neurite outgrowth. Thirdly, the over-expression of the C-terminal GRK-2 peptide, which sequesters Gbetagamma subunits, reduced the NGF-induced activation of p42/p44 MAPK. In contrast, the stimulation of PC12 cells with LPA leads to a predominant G(i)alpha2-mediated Trk A-independent activation of p42/p44 MAPK, where Gbetagamma subunits play a diminished role. These findings suggest a novel role for the constitutively active LPA(1) receptor in regulating NGF-induced neuronal differentiation.
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Affiliation(s)
- Noreen A Moughal
- Department of Physiology and Pharmacology, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, Glasgow, UK
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28
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Wu EHT, Tam BHL, Wong YH. Constitutively active alpha subunits of G(q/11) and G(12/13) families inhibit activation of the pro-survival Akt signaling cascade. FEBS J 2006; 273:2388-98. [PMID: 16704413 DOI: 10.1111/j.1742-4658.2006.05245.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Accumulating evidence indicates that G protein signaling plays an active role in the regulation of cell survival. Our previous study demonstrated the regulatory effects of G(i/o) proteins in nerve growth factor-induced activation of pro-survival Akt kinase. In the present study we explored the role of various members of the G(s), G(q/11) and G(12/13) subfamilies in the regulation of Akt in cultured mammalian cells. In human embryonic kidney 293 cells transiently expressing constitutively active mutants of G alpha11, G alpha14, G alpha16, G alpha12, or G alpha13 (G alpha11QL, G alpha14QL, G alpha16QL, G alpha12QL and G alpha13QL, respectively), basal phosphorylation of Akt was attenuated, as revealed by western blotting analysis using a phosphospecific anti-Akt immunoglobulin. In contrast, basal Akt phosphorylation was unaffected by the overexpression of a constitutively active G alpha(s) mutant (G alpha(s)QL). Additional experiments showed that G alpha11QL, G alpha14QL, G alpha16QL, G alpha12QL and G alpha13QL, but not G alpha(s)QL, attenuated phosphorylation of the Akt-regulated translation regulator tuberin. Moreover, they were able to inhibit the epidermal growth factor-induced Akt activation and tuberin phosphorylation. The inhibitory mechanism of Gq family members was independent of phospholipase Cbeta activation and calcium signaling because G alpha11QL, G alpha14QL and G alpha16QL remained capable of inhibiting epidermal growth factor-induced Akt activation in cells pretreated with U73122 and the intracellular calcium chelator, BAPTA/AM. Finally, overexpression of the dominant negative mutant of RhoA blocked G alpha12QL- and G alpha13QL-mediated inhibition, suggesting that activated G alpha12 and G alpha13 inhibit Akt signaling via RhoA. Collectively, this study demonstrated the inhibitory effect of activated G alpha11, G alpha14, G alpha16, G alpha12 and G alpha13 on pro-survival Akt signaling.
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Affiliation(s)
- Eddy H T Wu
- Department of Biochemistry, the Molecular Neuroscience Center, and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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29
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Wu EHT, Wong YH. Activation of delta-, kappa-, and mu-opioid receptors induces phosphorylation of tuberin in transfected HEK 293 cells and native cells. Biochem Biophys Res Commun 2006; 334:838-44. [PMID: 16053916 DOI: 10.1016/j.bbrc.2005.06.184] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2005] [Accepted: 06/29/2005] [Indexed: 12/27/2022]
Abstract
A number of G protein-coupled receptors have been shown to stimulate tuberin phosphorylation, which is critical for the regulation of translation and is apparently involved in neurotrophin-promoted survival of serum-deprived cells. Here, in HEK 293 cells transiently expressing the delta-, kappa-, or mu-opioid receptors, Western blotting analysis using a phosphospecific anti-tuberin antibody revealed a dose- and time-dependent increase in tuberin phosphorylation upon stimulation by specific opioid agonists. In NG108-15, PC12, and SH-SY5Y cells that endogenously express delta-, kappa-, and mu-opioid receptors, respectively, specific opioid agonists also stimulated tuberin phosphorylation in a dose- and time-dependent manner. Pretreatment of cells with pertussis toxin or PI3K inhibitor wortmannin blocked the opioid-stimulated tuberin phosphorylation, implicating the possible involvement of the G(i/o) proteins and the phosphatidylinositol-3 kinase/Akt pathway in opioid-induced tuberin phosphorylation. This is the first study that demonstrates the regulatory role of opioid receptors on tuberin.
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MESH Headings
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer/pharmacology
- Cell Line
- Cells, Cultured
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
- Enkephalin, D-Penicillamine (2,5)-/pharmacology
- ErbB Receptors/metabolism
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Humans
- Pertussis Toxin/pharmacology
- Phosphatidylinositol 3-Kinases/metabolism
- Phosphorylation
- Receptors, Opioid, delta/physiology
- Receptors, Opioid, kappa/physiology
- Receptors, Opioid, mu/physiology
- Transcriptional Activation
- Transfection
- Tuberous Sclerosis Complex 2 Protein
- Tumor Suppressor Proteins/metabolism
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Affiliation(s)
- Eddy H T Wu
- Department of Biochemistry, The Molecular Neuroscience Center, The Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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30
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Wu EHT, Wong YH. Activation of muscarinic M4 receptor augments NGF-induced pro-survival Akt signaling in PC12 cells. Cell Signal 2006; 18:285-93. [PMID: 15979279 DOI: 10.1016/j.cellsig.2005.04.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2005] [Revised: 04/28/2005] [Accepted: 04/28/2005] [Indexed: 01/10/2023]
Abstract
Survival or death of neurons during development is mediated by the integration of a diverse array of signal transduction cascades that are controlled by the availability and acquisition of neurotrophic factors and agonists acting at G protein-coupled receptors (GPCRs). Recent studies have demonstrated that GPCRs can modulate signals elicited by receptor tyrosine kinases (RTK) and vice versa. Here, we examined the activity of pro-survival Akt kinase, in response to stimulation by muscarinic acetylcholine receptors (mAChRs) and co-activation with the nerve growth factor (NGF) receptor in PC12 cells endogenously expressing Gi-coupled M4 mAChR and Gq-coupled M1 and M5 mAChRs. Western blotting analysis using a phosphospecific anti-Akt antibody revealed a dose- and time-dependent increase in Akt phosphorylation in cells stimulated with mAChR specific agonist carbachol (CCh). Co-stimulation with CCh and NGF resulted in augmentation of Akt activity in a pertussis toxin (PTX)-sensitive manner, suggesting that M4 mAChR, but not M1 and M5 mAChRs, was associated with this synergistic Akt activation. The use of transducin as a Gbetagamma scavenger indicated that Gbetagamma subunits rather than Galphai/o acted as the signal transducer. Additional experiments showed that CCh treatment augmented NGF-induced phosphorylation and degradation of the Akt-regulated translation regulator tuberin. This augmentation was also inhibited by PTX pre-treatment or overexpression of transducin. Finally, co-stimulation of PC12 cells with CCh and NGF resulted in enhancement of cell survival. This is the first study that demonstrates the augmentation effect between M4 mAChR and NGF receptor, and the regulatory role of mAChR on tuberin.
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Affiliation(s)
- Eddy H T Wu
- Department of Biochemistry, Molecular Neuroscience Center, Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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31
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Guan J, Luo Y, Denker B. Purkinje cell protein-2 (Pcp2) stimulates differentiation in PC12 cells by Gbetagamma-mediated activation of Ras and p38 MAPK. Biochem J 2006; 392:389-97. [PMID: 15948714 PMCID: PMC1316275 DOI: 10.1042/bj20042102] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Purkinje cell protein-2 (Pcp2 or L7) is highly expressed in cerebellar Purkinje cells and retinal bipolar neurons and interacts with the Galpha(i/o) family of G-proteins. Although the expression pattern of Pcp2 in the developing central nervous system suggests a role in differentiation, its function remains unknown. We established Tet-off inducible expression of Pcp2 in PC12 cells (rat pheochromocytoma cells) to determine whether Pcp2 regulates neuronal differentiation. Utilizing a polyclonal antibody, Pcp2 was localized in the cell body and throughout neurites of differentiated PC12 cells, similar to its localization in cerebellar Purkinje cells. Pcp2 expression in PC12 cells stimulated process formation (5-fold) and NGF (nerve growth factor)-stimulated neurite length (2-fold). Under basal conditions, Pcp2-PC12 cells demonstrated a 5-fold increase in Ras activation relative to non-induced PC12 cells and there was no change in extracellular-signal-regulated kinase 1/2 activity with Pcp2 expression. However, Pcp2 induction led to a >3-fold increase in basal p38 MAPK (mitogen-activated protein kinase) activity and the addition of NGF significantly stimulated both Ras and p38 MAPK in Pcp2-PC12 cells relative to the controls. Pretreatment of Pcp2-PC12 cells with the p38-specific inhibitor SB203580 blocked both the increased neurite formation and NGF-stimulated neurite growth. Pertussis toxin treatment had no effect on neurite growth in control cells, but completely blocked Pcp2-mediated increased neurite growth. Transient transfection of the beta-adrenergic receptor kinase C-terminus to prevent signalling through Gbetagamma in Pcp2-PC12 cells also inhibited the Pcp2-induced phenotype and reduced the Pcp2-stimulated Ras activation. Taken together, these findings demonstrate that Pcp2 induces differentiation in PC12 cells, in part through Gbetagamma-mediated Ras and p38 MAPK activation and suggest the potential for similar signalling mechanisms in Purkinje cells.
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Affiliation(s)
- Jiazhen Guan
- *Renal Division, Brigham and Women's Hospital and Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, U.S.A
| | - Yuan Luo
- †Department of Biological Sciences, University of Southern Mississippi, 2609 West 4th Street, Hattiesburg, MS 39406, U.S.A
| | - Bradley M. Denker
- *Renal Division, Brigham and Women's Hospital and Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, U.S.A
- To whom correspondence should be addressed (email )
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