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Park OS, Bang JK, Cheong C, Jeon YH. Structure of AQEE-30 of VGF Neuropeptide in Membrane-Mimicking Environments. Int J Mol Sci 2022; 23:ijms232213953. [PMID: 36430431 PMCID: PMC9696787 DOI: 10.3390/ijms232213953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 11/07/2022] [Accepted: 11/07/2022] [Indexed: 11/16/2022] Open
Abstract
AQEE-30 is one of the VGF peptides, which are derived from the VGF polypeptide precursor, and related to various physiological phenomena including neuroprotective effects in Huntington's disease and amyotrophic lateral sclerosis (ALS). Although various functions of AQEE-30 have been reported so far, the structure of this peptide has not been reported yet. In this study, the structure of human AQEE-30 was investigated in hexafluoroisopropanol (HFIP) and dodecyl phosphocholine (DPC) micelle solutions, using circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy. CD results showed that AQEE-30 had a partial helical structure in aqueous buffer, and the helical structure was stabilized in the HFIP and DPC micelle solutions. The 3D structures determined by NMR spectroscopy showed that AQEE-30 adopted mainly α-helical structure in both the HFIP and DPC micelle solutions. The surface of AQEE-30 showed that it was predominantly negatively charged. The residues from 601 to 611 in both the HFIP and DPC micelle solutions showed amphiphilicity with four negatively charged residues, glutamate. The C-terminal consecutive arginine residues formed a partial positively charged surface. These results suggest an α-helical active structure of AQEE-30 in the cell-membrane environment.
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Affiliation(s)
- One-Sung Park
- College of Pharmacy, Korea University Sejong Campus, Sejong 30019, Korea
- Division of Bioconvergence Analysis, Korea Basic Science Institute, Cheongju 28119, Korea
| | - Jeong-Kyu Bang
- Division of Bioconvergence Analysis, Korea Basic Science Institute, Cheongju 28119, Korea
| | - Chaejoon Cheong
- Division of Bioconvergence Analysis, Korea Basic Science Institute, Cheongju 28119, Korea
- Department of Bioanalytical Sciences, University of Science and Technology, Cheongju 28119, Korea
- Correspondence: (C.C.); (Y.-H.J.)
| | - Young-Ho Jeon
- College of Pharmacy, Korea University Sejong Campus, Sejong 30019, Korea
- Correspondence: (C.C.); (Y.-H.J.)
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2
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Mizoguchi T, Fujimori H, Ohba T, Shimazawa M, Nakamura S, Shinohara M, Hara H. Glutamatergic dysfunction is associated with phenotypes of VGF-overexpressing mice. Exp Brain Res 2022; 240:2051-2060. [PMID: 35587282 DOI: 10.1007/s00221-022-06384-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 05/04/2022] [Indexed: 11/04/2022]
Abstract
VGF nerve growth factor inducible (VGF) is a neuropeptide precursor, which is induced by several neurotrophic factors, including nerve growth factor and brain-derived neurotrophic factor. Clinically, an upregulation of VGF levels has been reported in the cerebrospinal fluid and prefrontal cortex of patients with schizophrenia. In our previous study, mice overexpressing VGF exhibited schizophrenia-related behaviors. In the current study, we characterized the biochemical changes in the brains of VGF-overexpressing mice. Metabolomics analysis of neurotransmitters revealed that glutamic acid and N-acetyl-L-aspartic acid were increased in the striatum of VGF-overexpressing mice. Additionally, the present study revealed that MK-801, which causes the disturbance in glutamic acid metabolism, increased the expression level of VGF-derived peptide (NAPP129, named VGF20), and VGF-overexpressing mice had higher sensitivity to MK-801. These results suggest that VGF may modulate the regulation of glutamic acid levels and the degree of glutamic acid signaling.
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Affiliation(s)
- Takahiro Mizoguchi
- Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan
| | - Honoka Fujimori
- Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan
| | - Takuya Ohba
- Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan
| | - Masamitsu Shimazawa
- Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan.
| | - Shinsuke Nakamura
- Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan
| | - Masakazu Shinohara
- The Integrated Center for Mass Spectrometry, Kobe University Graduate School of Medicine, Kobe, Japan.,Division of Epidemiology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hideaki Hara
- Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan
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3
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Khan D, Moffett RC, Flatt PR, Tarasov AI. Classical and non-classical islet peptides in the control of β-cell function. Peptides 2022; 150:170715. [PMID: 34958851 DOI: 10.1016/j.peptides.2021.170715] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 11/25/2021] [Accepted: 12/17/2021] [Indexed: 12/25/2022]
Abstract
The dual role of the pancreas as both an endocrine and exocrine gland is vital for food digestion and control of nutrient metabolism. The exocrine pancreas secretes enzymes into the small intestine aiding digestion of sugars and fats, whereas the endocrine pancreas secretes a cocktail of hormones into the blood, which is responsible for blood glucose control and regulation of carbohydrate, protein and fat metabolism. Classical islet hormones, insulin, glucagon, pancreatic polypeptide and somatostatin, interact in an autocrine and paracrine manner, to fine-tube the islet function and insulin secretion to the needs of the body. Recently pancreatic islets have been reported to express a number of non-classical peptide hormones involved in metabolic signalling, whose major production site was believed to reside outside pancreas, e.g. in the small intestine. We highlight the key non-classical islet peptides, and consider their involvement, together with established islet hormones, in regulation of stimulus-secretion coupling as well as proliferation, survival and transdifferentiation of β-cells. We furthermore focus on the paracrine interaction between classical and non-classical islet hormones in the maintenance of β-cell function. Understanding the functional relationships between these islet peptides might help to develop novel, more efficient treatments for diabetes and related metabolic disorders.
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Affiliation(s)
- Dawood Khan
- Biomedical Sciences Research Institute, School of Biomedical Sciences, Ulster University, Coleraine, Northern Ireland, UK.
| | - R Charlotte Moffett
- Biomedical Sciences Research Institute, School of Biomedical Sciences, Ulster University, Coleraine, Northern Ireland, UK
| | - Peter R Flatt
- Biomedical Sciences Research Institute, School of Biomedical Sciences, Ulster University, Coleraine, Northern Ireland, UK
| | - Andrei I Tarasov
- Biomedical Sciences Research Institute, School of Biomedical Sciences, Ulster University, Coleraine, Northern Ireland, UK
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4
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Dalbøge LS, Jacobsen JM, Mehrotra S, Mercer AJ, Cox N, Liu F, Bennett CM, Said M, Tang-Christensen M, Raun K, Hansen JL, Grove KL, Baquero AF. Evaluation of VGF peptides as potential anti-obesity candidates in pre-clinical animal models. Peptides 2021; 136:170444. [PMID: 33245952 DOI: 10.1016/j.peptides.2020.170444] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 09/03/2020] [Accepted: 11/09/2020] [Indexed: 12/24/2022]
Abstract
VGF is a peptide precursor expressed in neuroendocrine cells that is suggested to play a role in the regulation of energy homeostasis. VGF is proteolytically cleaved to yield multiple bioactive peptides. However, the specific actions of VGF-derived peptides on energy homeostasis remain unclear. The aim of the present work was to investigate the role of VGF-derived peptides in energy homeostasis and explore the pharmacological actions of VGF-derived peptides on body weight in preclinical animal models. VGF-derived peptides (NERP-1, NERP-2, PGH-NH2, PGH-OH, NERP-4, TLQP-21, TLQP-30, TLQP-62, HHPD-41, AQEE-30, and LQEQ-19) were synthesized and screened for their ability to affect neuronal activity in vitro on hypothalamic brain slices and modulate food intake and energy expenditure after acute central administration in vivo. In addition, the effects of NERP-1, NERP-2, PGH-NH2, TLQP-21, TLQP-62, and HHPD-41 on energy homeostasis were studied after chronic central infusion. NERP-1, PGH-NH2, HHPD-41, and TLQP-62 increased the functional activity of hypothalamic neuronal networks. However, none of the peptides altered energy homeostasis after either acute or chronic ICV administration. The present data do not support the potential use of the tested VGF-derived peptides as novel anti-obesity drug candidates.
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Affiliation(s)
- Louise S Dalbøge
- Novo Nordisk Research Center Seattle Inc., 530 Fairview Ave N, Seattle, WA, 98109, USA
| | - Julie M Jacobsen
- Novo Nordisk Research Center Seattle Inc., 530 Fairview Ave N, Seattle, WA, 98109, USA
| | - Suneet Mehrotra
- Novo Nordisk Research Center Seattle Inc., 530 Fairview Ave N, Seattle, WA, 98109, USA
| | - Aaron J Mercer
- Novo Nordisk Research Center Seattle Inc., 530 Fairview Ave N, Seattle, WA, 98109, USA
| | - Nick Cox
- Novo Nordisk Research Center Seattle Inc., 530 Fairview Ave N, Seattle, WA, 98109, USA
| | - Fa Liu
- Novo Nordisk Research Center Seattle Inc., 530 Fairview Ave N, Seattle, WA, 98109, USA
| | - Camdin M Bennett
- Novo Nordisk Research Center Seattle Inc., 530 Fairview Ave N, Seattle, WA, 98109, USA
| | - Meerit Said
- Novo Nordisk Research Center Seattle Inc., 530 Fairview Ave N, Seattle, WA, 98109, USA
| | | | - Kirsten Raun
- Novo Nordisk A/S, Novo Nordisk Park, 2760, Måløv, Denmark
| | - Jakob L Hansen
- Novo Nordisk A/S, Novo Nordisk Park, 2760, Måløv, Denmark
| | - Kevin L Grove
- Novo Nordisk Research Center Seattle Inc., 530 Fairview Ave N, Seattle, WA, 98109, USA
| | - Arian F Baquero
- Novo Nordisk Research Center Seattle Inc., 530 Fairview Ave N, Seattle, WA, 98109, USA.
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Corda G, Noli B, Manconi B, Brancia C, Pellegrini M, Naro F, Olianas A, Ferri GL, Cocco C. TLQP-21 changes in response to a glucose load. Tissue Cell 2020; 68:101471. [PMID: 33348234 DOI: 10.1016/j.tice.2020.101471] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 11/12/2020] [Accepted: 11/15/2020] [Indexed: 11/26/2022]
Abstract
BACKGROUND The TLQP-21 peptide potentiates glucose-stimulated insulin secretion, hence we investigated its endogenous response to glucose. METHODS Fasted mice received intraperitoneal glucose (3 g/kg), or saline (controls), and were sacrificed 30 and 120 min later (4 groups, n = 6/group). We investigated TLQP-21 in pancreas and plasma using immunohistochemistry, enzyme-linked immunosorbent assay (ELISA) and high performance liquid chromatography (HPLC), as well as TLQP-21 receptors (gC1q-R and C3a-R1) expression in pancreas by immunohistochemistry. RESULTS In pancreas, TLQP-immunoreactivity (TLQP-ir.) was shown in insulin-, glucagon- and somatostatin-containing cells. Upon glucose, TLQP-ir. decreased at 30 min (∼40 % vs. controls), while returning to basal values at 120 min. In all groups, C3a-R1 was localized in ∼50 % of TLQP labelled islet cells (mostly central), while gC1q-R was detected in ∼25 % of TLQP cells (mainly peripheral). HPLC fractions of control pancreas extracts, assessed by ELISA, confirmed the presence of a TLQP-21 compatible-form (∼2.5 kDa MW). In plasma, TLQP-ir. increased at 30 min (∼30 %), with highest concentrations at 120 min (both: p<0.05 vs. controls), while HPLC fractions showed an increase in the TLQP-21 compatible form. CONCLUSIONS Upon hyperglycaemia, TLQP-21 would be released from islets, to enhance insulin secretion but we cannot exclude an autocrine activity which may regulate insulin storage/secretion.
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Affiliation(s)
- Giulia Corda
- Department of Biomedical Sciences, University of Cagliari, Monserrato, CA, Italy.
| | - Barbara Noli
- Department of Biomedical Sciences, University of Cagliari, Monserrato, CA, Italy
| | - Barbara Manconi
- Department of Life and Enviromental Sciences, University of Cagliari, Monserrato, CA, Italy
| | - Carla Brancia
- Department of Biomedical Sciences, University of Cagliari, Monserrato, CA, Italy
| | - Manuela Pellegrini
- Department of Anatomical, Istological and Legal Medicine Sciences of the locomotor apparatus, University of "La Sapienza", Roma, Italy
| | - Fabio Naro
- Department of Anatomical, Istological and Legal Medicine Sciences of the locomotor apparatus, University of "La Sapienza", Roma, Italy
| | - Alessandra Olianas
- Department of Life and Enviromental Sciences, University of Cagliari, Monserrato, CA, Italy
| | - Gian-Luca Ferri
- Department of Biomedical Sciences, University of Cagliari, Monserrato, CA, Italy
| | - Cristina Cocco
- Department of Biomedical Sciences, University of Cagliari, Monserrato, CA, Italy
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6
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Park O, Bang JK, Ryu K, Hwang E, Hong KS, Byun Y, Cheong C, Jeon YH. Structure of neuroendocrine regulatory peptide‐2 in membrane‐mimicking environments. Pept Sci (Hoboken) 2020. [DOI: 10.1002/pep2.24206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- One‐Sung Park
- College of Pharmacy Korea University Sejong Campus Sejong South Korea
- Division of Bioconvergence Analysis Korea Basic Science Institute Cheongju South Korea
| | - Jeong Kyu Bang
- Division of Bioconvergence Analysis Korea Basic Science Institute Cheongju South Korea
| | - Kyoung‐Seok Ryu
- Division of Bioconvergence Analysis Korea Basic Science Institute Cheongju South Korea
| | - Eunha Hwang
- Division of Bioconvergence Analysis Korea Basic Science Institute Cheongju South Korea
| | - Kwan Soo Hong
- Division of Bioconvergence Analysis Korea Basic Science Institute Cheongju South Korea
| | - Youngjoo Byun
- College of Pharmacy Korea University Sejong Campus Sejong South Korea
| | - Chaejoon Cheong
- Division of Bioconvergence Analysis Korea Basic Science Institute Cheongju South Korea
| | - Young Ho Jeon
- College of Pharmacy Korea University Sejong Campus Sejong South Korea
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7
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Pakdel M, von Blume J. Exploring new routes for secretory protein export from the trans-Golgi network. Mol Biol Cell 2019; 29:235-240. [PMID: 29382805 PMCID: PMC5996961 DOI: 10.1091/mbc.e17-02-0117] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 11/30/2017] [Accepted: 12/01/2017] [Indexed: 12/21/2022] Open
Abstract
Sorting of soluble proteins for transport to intracellular compartments and for secretion from cells is essential for cell and tissue homeostasis. The trans-Golgi network (TGN) is a major sorting station that sorts secretory proteins into specific carriers to transport them to their final destinations. The sorting of lysosomal hydrolases at the TGN by the mannose 6-phosphate receptor is well understood. The recent discovery of a Ca2+-based sorting of secretory cargo at the TGN is beginning to uncover the mechanism by which cells sort secretory cargoes from Golgi residents and cargoes destined to the other cellular compartments. This Ca2+-based sorting involves the cytoplasmic actin cytoskeleton, which through membrane anchored Ca2+ ATPase SPCA1 and the luminal Ca2+ binding protein Cab45 sorts of a subset of secretory proteins at the TGN. We present this discovery and highlight important challenges that remain unaddressed in the overall pathway of cargo sorting at the TGN.
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Affiliation(s)
- Mehrshad Pakdel
- Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Julia von Blume
- Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
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8
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Stephens SB, Edwards RJ, Sadahiro M, Lin WJ, Jiang C, Salton SR, Newgard CB. The Prohormone VGF Regulates β Cell Function via Insulin Secretory Granule Biogenesis. Cell Rep 2018; 20:2480-2489. [PMID: 28877479 DOI: 10.1016/j.celrep.2017.08.050] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 07/25/2017] [Accepted: 08/15/2017] [Indexed: 12/18/2022] Open
Abstract
The prohormone VGF is expressed in neuroendocrine and endocrine tissues and regulates nutrient and energy status both centrally and peripherally. We and others have shown that VGF-derived peptides have direct action on the islet β cell as secretagogues and cytoprotective agents; however, the endogenous function of VGF in the β cell has not been described. Here, we demonstrate that VGF regulates secretory granule formation. VGF loss-of-function studies in both isolated islets and conditional knockout mice reveal a profound decrease in stimulus-coupled insulin secretion. Moreover, VGF is necessary to facilitate efficient exit of granule cargo from the trans-Golgi network and proinsulin processing. It also functions to replenish insulin granule stores following nutrient stimulation. Our data support a model in which VGF operates at a critical node of granule biogenesis in the islet β cell to coordinate insulin biosynthesis with β cell secretory capacity.
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Affiliation(s)
- Samuel B Stephens
- Sarah W. Stedman Nutrition and Metabolism Center, Duke University Medical Center, Durham, NC 27704, USA; Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27704, USA; Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27704, USA.
| | - Robert J Edwards
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27704, USA
| | - Masato Sadahiro
- Department of Neuroscience, Icahn School of Medicine at Mt. Sinai, New York, NY 10029, USA; Graduate School of Biomedical Sciences, Icahn School of Medicine at Mt. Sinai, New York, NY 10029, USA
| | - Wei-Jye Lin
- Department of Neuroscience, Icahn School of Medicine at Mt. Sinai, New York, NY 10029, USA
| | - Cheng Jiang
- Department of Neuroscience, Icahn School of Medicine at Mt. Sinai, New York, NY 10029, USA; Graduate School of Biomedical Sciences, Icahn School of Medicine at Mt. Sinai, New York, NY 10029, USA
| | - Stephen R Salton
- Department of Neuroscience, Icahn School of Medicine at Mt. Sinai, New York, NY 10029, USA; Friedman Brain Institute, Icahn School of Medicine at Mt. Sinai, New York, NY 10029, USA
| | - Christopher B Newgard
- Sarah W. Stedman Nutrition and Metabolism Center, Duke University Medical Center, Durham, NC 27704, USA; Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27704, USA; Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27704, USA; Department of Medicine, Division of Endocrinology, Duke University Medical Center, Durham, NC 27704, USA
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9
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Rivolta I, Binda A, Molteni L, Rizzi L, Bresciani E, Possenti R, Fehrentz JA, Verdié P, Martinez J, Omeljaniuk RJ, Locatelli V, Torsello A. JMV5656, A Novel Derivative of TLQP-21, Triggers the Activation of a Calcium-Dependent Potassium Outward Current in Microglial Cells. Front Cell Neurosci 2017; 11:41. [PMID: 28280458 PMCID: PMC5322282 DOI: 10.3389/fncel.2017.00041] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 02/08/2017] [Indexed: 01/13/2023] Open
Abstract
TLQP-21 (TLQPPASSRRRHFHHALPPAR) is a multifunctional peptide that is involved in the control of physiological functions, including feeding, reproduction, stress responsiveness, and general homeostasis. Despite the huge interest in TLQP-21 biological activity, very little is known about its intracellular mechanisms of action. In microglial cells, TLQP-21 stimulates increases of intracellular Ca2+ that may activate functions, including proliferation, migration, phagocytosis and production of inflammatory molecules. Our aim was to investigate whether JMV5656 (RRRHFHHALPPAR), a novel short analogue of TLQP-21, stimulates intracellular Ca2+ in the N9 microglia cells, and whether this Ca2+ elevation is coupled with the activation Ca2+-sensitive K+ channels. TLQP-21 and JMV5656 induced a sharp, dose-dependent increment in intracellular calcium. In 77% of cells, JMV5656 also caused an increase in the total outward currents, which was blunted by TEA (tetraethyl ammonium chloride), a non-selective blocker of voltage-dependent and Ca2+-activated potassium (K+) channels. Moreover, the effects of ion channel blockers charybdotoxin and iberiotoxin, suggested that multiple calcium-activated K+ channel types drove the outward current stimulated by JMV5656. Additionally, inhibition of JMV5656-stimulated outward currents by NS6180 (4-[[3-(trifluoromethyl)phenyl]methyl]-2H-1,4 benzothiazin-3(4H)-one) and TRAM-34 (triarylmethane-34), indicated that KCa3.1 channels are involved in this JMV5656 mechanisms of action. In summary, we demonstrate that, in N9 microglia cells, the interaction of JMV5656 with the TLQP-21 receptors induced an increase in intracellular Ca2+, and, following extracellular Ca2+ entry, the opening of KCa3.1 channels.
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Affiliation(s)
- Ilaria Rivolta
- Department of Medicine and Surgery, University of Milano-Bicocca Monza, Italy
| | - Anna Binda
- Department of Medicine and Surgery, University of Milano-Bicocca Monza, Italy
| | - Laura Molteni
- Department of Medicine and Surgery, University of Milano-Bicocca Monza, Italy
| | - Laura Rizzi
- Department of Medicine and Surgery, University of Milano-Bicocca Monza, Italy
| | - Elena Bresciani
- Department of Medicine and Surgery, University of Milano-Bicocca Monza, Italy
| | - Roberta Possenti
- Department of Medicine of Systems, University of Rome "Tor Vergata" Rome, Italy
| | - Jean-Alain Fehrentz
- CNRS, Institut des Biomolécules Max Mousseron UMR5247, École Nationale Supérieure de Chimie de Montpellier - University of Montpellier Montpellier, France
| | - Pascal Verdié
- CNRS, Institut des Biomolécules Max Mousseron UMR5247, École Nationale Supérieure de Chimie de Montpellier - University of Montpellier Montpellier, France
| | - Jean Martinez
- CNRS, Institut des Biomolécules Max Mousseron UMR5247, École Nationale Supérieure de Chimie de Montpellier - University of Montpellier Montpellier, France
| | | | - Vittorio Locatelli
- Department of Medicine and Surgery, University of Milano-Bicocca Monza, Italy
| | - Antonio Torsello
- Department of Medicine and Surgery, University of Milano-Bicocca Monza, Italy
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10
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Noli B, Brancia C, D’Amato F, Ferri GL, Cocco C. VGF changes during the estrous cycle: a novel endocrine role for TLQP peptides? PLoS One 2014; 9:e108456. [PMID: 25280008 PMCID: PMC4184793 DOI: 10.1371/journal.pone.0108456] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 08/29/2014] [Indexed: 01/25/2023] Open
Abstract
Although the VGF derived peptide TLQP-21 stimulates gonadotropin-releasing hormone (GnRH) and gonadotropin secretion, available data on VGF peptides and reproduction are limited. We used antibodies specific for the two ends of the VGF precursor, and for two VGF derived peptides namely TLQP and PGH, to be used in immunohistochemistry and enzyme-linked immunosorbent assay complemented with gel chromatography. In cycling female rats, VGF C-/N-terminus and PGH peptide antibodies selectively labelled neurones containing either GnRH, or kisspeptin (VGF N-terminus only), pituitary gonadotrophs and lactotrophs, or oocytes (PGH peptides only). Conversely, TLQP peptides were restricted to somatostatin neurones, gonadotrophs, and ovarian granulosa, interstitial and theca cells. TLQP levels were highest, especially in plasma and ovary, with several molecular forms shown in chromatography including one compatible with TLQP-21. Among the cycle phases, TLQP levels were higher during metestrus-diestrus in median eminence and pituitary, while increased in the ovary and decreased in plasma during proestrus. VGF N- and C-terminus peptides also showed modulations over the estrous cycle, in median eminence, pituitary and plasma, while PGH peptides did not. In ovariectomised rats, plasmatic TLQP peptide levels showed distinct reduction suggestive of a major origin from the ovary, while the estrogen-progesterone treatment modulated VGF C-terminus and TLQP peptides in the hypothalamus-pituitary complex. In in vitro hypothalamus, TLQP-21 stimulated release of growth hormone releasing hormone but not of somatostatin. In conclusion, various VGF peptides may regulate the hypothalamus-pituitary complex via specific neuroendocrine mechanisms while TLQP peptides may act at further, multiple levels via endocrine mechanisms involving the ovary.
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Affiliation(s)
- Barbara Noli
- Department of Biomedical Sciences, University of Cagliari, Monserrato (Cagliari), Italy
| | - Carla Brancia
- Department of Biomedical Sciences, University of Cagliari, Monserrato (Cagliari), Italy
| | - Filomena D’Amato
- Department of Biomedical Sciences, University of Cagliari, Monserrato (Cagliari), Italy
| | - Gian-Luca Ferri
- Department of Biomedical Sciences, University of Cagliari, Monserrato (Cagliari), Italy
- * E-mail: (CC); (GLF)
| | - Cristina Cocco
- Department of Biomedical Sciences, University of Cagliari, Monserrato (Cagliari), Italy
- * E-mail: (CC); (GLF)
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11
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Fargali S, Garcia AL, Sadahiro M, Jiang C, Janssen WG, Lin WJ, Cogliani V, Elste A, Mortillo S, Cero C, Veitenheimer B, Graiani G, Pasinetti GM, Mahata SK, Osborn JW, Huntley GW, Phillips GR, Benson DL, Bartolomucci A, Salton SR. The granin VGF promotes genesis of secretory vesicles, and regulates circulating catecholamine levels and blood pressure. FASEB J 2014; 28:2120-33. [PMID: 24497580 DOI: 10.1096/fj.13-239509] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Secretion of proteins and neurotransmitters from large dense core vesicles (LDCVs) is a highly regulated process. Adrenal LDCV formation involves the granin proteins chromogranin A (CgA) and chromogranin B (CgB); CgA- and CgB-derived peptides regulate catecholamine levels and blood pressure. We investigated function of the granin VGF (nonacronymic) in LDCV formation and the regulation of catecholamine levels and blood pressure. Expression of exogenous VGF in nonendocrine NIH 3T3 fibroblasts resulted in the formation of LDCV-like structures and depolarization-induced VGF secretion. Analysis of germline VGF-knockout mouse adrenal medulla revealed decreased LDCV size in noradrenergic chromaffin cells, increased adrenal norepinephrine and epinephrine content and circulating plasma epinephrine, and decreased adrenal CgB. These neurochemical changes in VGF-knockout mice were associated with hypertension. Germline knock-in of human VGF1-615 into the mouse Vgf locus rescued the hypertensive knockout phenotype, while knock-in of a truncated human VGF1-524 that lacks several C-terminal peptides, including TLQP-21, resulted in a small but significant increase in systolic blood pressure compared to hVGF1-615 mice. Finally, acute and chronic administration of the VGF-derived peptide TLQP-21 to rodents decreased blood pressure. Our studies establish a role for VGF in adrenal LDCV formation and the regulation of catecholamine levels and blood pressure.
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Affiliation(s)
- Samira Fargali
- 1Department of Neuroscience, Box 1065, Ichan School of Medicine at Mt. Sinai, 1 Gustave L. Levy Pl., New York, NY 10029, USA.
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12
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Mass spectrometry identification of granins and other proteins secreted by neuroblastoma cells. Tumour Biol 2013; 34:1773-81. [PMID: 23519838 PMCID: PMC3661923 DOI: 10.1007/s13277-013-0716-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 02/24/2013] [Indexed: 12/02/2022] Open
Abstract
We used mass spectrometry-based protein identification to determine the presence of granins and other proteins in the mouse neuroblastoma secretome. We detected polypeptides derived from four members of the granin family: chromogranin A, chromogranin B, secretogranin III, and VGF. Many of them are derived from previously described biologically active regions; however, for VGF and CgB, we detected peptides not related to known bioactivities. Along with granins, we identified 115 other proteins secreted by mouse neuroblastoma cells, belonging to different functional categories. Fifty-six out of 119 detected proteins possess the signal fragments required for translocation into endoplasmic reticulum. Sequences of remaining 63 proteins were analyzed using SecretomeP algorithm to determine probability of nonclassical secretion. Identified proteins are involved in the regulation of cell cycle, proliferation, apoptosis, angiogenesis, proteolysis, and cell adhesion.
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13
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Stephens SB, Schisler JC, Hohmeier HE, An J, Sun AY, Pitt GS, Newgard CB. A VGF-derived peptide attenuates development of type 2 diabetes via enhancement of islet β-cell survival and function. Cell Metab 2012; 16:33-43. [PMID: 22768837 PMCID: PMC3695697 DOI: 10.1016/j.cmet.2012.05.011] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 04/04/2012] [Accepted: 05/11/2012] [Indexed: 12/28/2022]
Abstract
Deterioration of functional islet β-cell mass is the final step in progression to Type 2 diabetes. We previously reported that overexpression of Nkx6.1 in rat islets has the dual effects of enhancing glucose-stimulated insulin secretion (GSIS) and increasing β-cell replication. Here we show that Nkx6.1 strongly upregulates the prohormone VGF in rat islets and that VGF is both necessary and sufficient for Nkx6.1-mediated enhancement of GSIS. Moreover, the VGF-derived peptide TLQP-21 potentiates GSIS in rat and human islets and improves glucose tolerance in vivo. Chronic injection of TLQP-21 in prediabetic ZDF rats preserves islet mass and slows diabetes onset. TLQP-21 prevents islet cell apoptosis by a pathway similar to that used by GLP-1, but independent of the GLP-1, GIP, or VIP receptors. Unlike GLP-1, TLQP-21 does not inhibit gastric emptying or increase heart rate. We conclude that TLQP-21 is a targeted agent for enhancing islet β-cell survival and function.
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Affiliation(s)
- Samuel B Stephens
- Sarah W. Stedman Nutrition and Metabolism Center, Duke University Medical Center, Durham, NC 27704, USA
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14
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Petrella C, Broccardo M, Possenti R, Severini C, Improta G. TLQP-21, a VGF-derived peptide, stimulates exocrine pancreatic secretion in the rat. Peptides 2012; 36:133-6. [PMID: 22561241 DOI: 10.1016/j.peptides.2012.03.035] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Revised: 03/29/2012] [Accepted: 03/30/2012] [Indexed: 02/01/2023]
Abstract
The aims of this paper were to study: (1) the effects of TLQP-21 (non-acronic name), the C-terminal region of the VGF (non-acronic name), polypeptide (from residue 557 to 576 of VGF), on in vitro amylase release from rat isolated pancreatic lobules and acinar cells; (2) the mechanism through which TLQP-21 regulates exocrine pancreatic secretion, by using the muscarinic receptor antagonist atropine (10(-6)M) and the cyclo-oxygenase inhibitor, indomethacin (10(-6)M). On pancreatic lobules of rats, concentrations of TLQP-21 from 10(-7) to 10(-5)M significantly (p<0.05) induced a 2-3-fold increase of baseline pancreatic amylase release, measured at the end of 60 min incubation period. Co-incubation with atropine 10(-6)M did not antagonise the enzyme outflow induced by the peptide. On the contrary, co-incubation of TLQP-21 (10(-7) and 10(-6)M) with indomethacin, at concentration of 10(-6)M, which alone did not modify enzyme secretion, completely suppressed the increase of amylase evoked by TLQP-21 on pancreatic lobules. On rat pancreatic acinar cells, TLQP-21, at all the concentrations tested, was unable to affect exocrine pancreatic secretion, indicating an indirect mechanism of action on acinar cells. These results put in evidence, for the first time, that TLQP-21, a VGF-derived peptide, modulates exocrine pancreatic secretion in rats through a stimulatory mechanism involving prostaglandin release. In conclusion, TLQP-21 could be included among the neurohumoral signals regulating pancreatic exocrine secretion, and increases the knowledge concerning the systems controlling this function.
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Affiliation(s)
- C Petrella
- Department of Physiology and Pharmacology V. Erspamer, Sapienza University of Rome, Rome, Italy.
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15
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Characterization of a novel peripheral pro-lipolytic mechanism in mice: role of VGF-derived peptide TLQP-21. Biochem J 2011; 441:511-22. [PMID: 21880012 DOI: 10.1042/bj20111165] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The peptides encoded by the VGF gene are gaining biomedical interest and are increasingly being scrutinized as biomarkers for human disease. An endocrine/neuromodulatory role for VGF peptides has been suggested but never demonstrated. Furthermore, no study has demonstrated so far the existence of a receptor-mediated mechanism for any VGF peptide. In the present study, we provide a comprehensive in vitro, ex vivo and in vivo identification of a novel pro-lipolytic pathway mediated by the TLQP-21 peptide. We show for the first time that VGF-immunoreactivity is present within sympathetic fibres in the WAT (white adipose tissue) but not in the adipocytes. Furthermore, we identified a saturable receptor-binding activity for the TLQP-21 peptide. The maximum binding capacity for TLQP-21 was higher in the WAT as compared with other tissues, and selectively up-regulated in the adipose tissue of obese mice. TLQP-21 increases lipolysis in murine adipocytes via a mechanism encompassing the activation of noradrenaline/β-adrenergic receptors pathways and dose-dependently decreases adipocytes diameters in two models of obesity. In conclusion, we demonstrated a novel and previously uncharacterized peripheral lipolytic pathway encompassing the VGF peptide TLQP-21. Targeting the sympathetic nerve–adipocytes interaction might prove to be a novel approach for the treatment of obesity-associated metabolic complications.
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16
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Bartolomucci A, Possenti R, Mahata SK, Fischer-Colbrie R, Loh YP, Salton SRJ. The extended granin family: structure, function, and biomedical implications. Endocr Rev 2011; 32:755-97. [PMID: 21862681 PMCID: PMC3591675 DOI: 10.1210/er.2010-0027] [Citation(s) in RCA: 228] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The chromogranins (chromogranin A and chromogranin B), secretogranins (secretogranin II and secretogranin III), and additional related proteins (7B2, NESP55, proSAAS, and VGF) that together comprise the granin family subserve essential roles in the regulated secretory pathway that is responsible for controlled delivery of peptides, hormones, neurotransmitters, and growth factors. Here we review the structure and function of granins and granin-derived peptides and expansive new genetic evidence, including recent single-nucleotide polymorphism mapping, genomic sequence comparisons, and analysis of transgenic and knockout mice, which together support an important and evolutionarily conserved role for these proteins in large dense-core vesicle biogenesis and regulated secretion. Recent data further indicate that their processed peptides function prominently in metabolic and glucose homeostasis, emotional behavior, pain pathways, and blood pressure modulation, suggesting future utility of granins and granin-derived peptides as novel disease biomarkers.
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Affiliation(s)
- Alessandro Bartolomucci
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, Minnesota 55455, USA
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17
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Cocco C, D'Amato F, Noli B, Ledda A, Brancia C, Bongioanni P, Ferri GL. Distribution of VGF peptides in the human cortex and their selective changes in Parkinson's and Alzheimer's diseases. J Anat 2010; 217:683-93. [PMID: 21039478 DOI: 10.1111/j.1469-7580.2010.01309.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
VGF mRNA and its precursor-derived products are selectively expressed in certain neurons and promptly respond to neurotrophins and to neural/electrical activity. Proteomic studies have previously revealed a reduction in some VGF peptides in the cerebrospinal fluid of patients affected by Alzheimer's disease and other conditions, suggesting their potential diagnostic and clinical significance. As the presence of VGF peptides within the human cortex has been somewhat elucidated, they were studied postmortem in the frontal, parietal, and temporal cortex areas of control subjects and patients affected by Parkinson's disease, and in parietal cortex samples from patients with Alzheimer's disease. We raised antibodies to the C-/N-terminal portions of the proVGF precursor protein, to the TPGH and TLQP sequences and to the neuroendocrine regulatory peptide (NERP)-1, all used for enzyme-linked immunosorbent assay coupled with gel chromatography and for immunohistochemistry. In the control brain samples, the levels of TPGH and C-terminus peptides were about 130-200 and 700-2000 pmol g⁻¹, respectively, the N-terminus and NERP-1 peptides were less represented (about 10-30 and 4-20 pmol g⁻¹, respectively), and the TLQP peptides were below detection limits. Upon gel chromatography, the VGF antisera mainly revealed small molecular weight forms (i.e. about 0.8-1.3 kDa), whereas VGF immunolocalisation was found within different types of neuron in rat and bovine brain cortices. In the Parkinson's disease samples, a clear-cut decrease was revealed in the parietal cortex only, exclusively for TPGH and NERP-1 peptides, whereas in the Alzheimer's disease samples, a reduction in all of the VGF peptides was shown. The results suggest the involvement of VGF in the physiological or pathophysiological mechanisms occurring in the parietal cortex of patients with Parkinson's and Alzheimer's diseases.
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Affiliation(s)
- Cristina Cocco
- Department of Cytomorphology, University of Cagliari, Monserrato, Cagliari, Italy.
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18
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Activation of kinase phosphorylation by heat-shift and mild heat-shock. CELL BIOLOGY INTERNATIONAL REPORTS 2010; 17:e00002. [PMID: 23119140 PMCID: PMC3476822 DOI: 10.1042/cbr20100002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Accepted: 04/21/2010] [Indexed: 11/17/2022]
Abstract
Most cells activate intracellular signalling to recover from heat damage. An increase of temperature, known as HS (heat shock), induces two major signalling events: the transcriptional induction of HSPs (heat-shock proteins) and the activation of the MAPK (mitogen-activated protein kinase) cascade. We performed the present study to examine the effects of HS, induced by different experimental conditions, on various kinases [ERK (extracellular-signal-regulated kinase), JNK (c-Jun N-terminal kinase), p38, Akt, AMPK (AMP-activated protein kinase) and PKC (protein kinase C)]. We investigated by Western blot analysis the phosphorylation of MAPK as a measure of cellular responsiveness to heat shift (37°C) and mild HS (40°C) in different cell lines. The results of the study indicate that every cell line responded to heat shift, and to a greater extent to HS, increasing ERK and JNK phosphorylation, whereas variable effects on activation or inhibition of PKC, AMPK, Akt and p38 were observed. Besides the implications of intracellular signalling activated by heat variations, these data may be of technical relevance, indicating possible sources of error due to different experimental temperature conditions.
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19
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Hickey AJR, Bradley JWI, Skea GL, Middleditch MJ, Buchanan CM, Phillips ARJ, Cooper GJS. Proteins associated with immunopurified granules from a model pancreatic islet beta-cell system: proteomic snapshot of an endocrine secretory granule. J Proteome Res 2009; 8:178-86. [PMID: 19055480 DOI: 10.1021/pr800675k] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
beta-Cell granules contain proteins involved in fuel regulation, which when altered, contribute to metabolic disorders including diabetes mellitus. We analyzed proteins present in purified granules from the INS-1E beta-cell model. Fifty-one component proteins were identified by LC-MS/MS including hormones, granins, protein processing components, cellular trafficking components, enzymes implicated in cellular metabolism and chaperone proteins. These findings may increase understanding of granule secretion and the processes leading to protein aggregation and beta-cell death in type-2 diabetes.
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Affiliation(s)
- Anthony J R Hickey
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
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20
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Thakker-Varia S, Alder J. Neuropeptides in depression: role of VGF. Behav Brain Res 2008; 197:262-78. [PMID: 18983874 DOI: 10.1016/j.bbr.2008.10.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Accepted: 10/05/2008] [Indexed: 12/20/2022]
Abstract
The monoamine hypothesis of depression is increasingly called into question by newer theories that revolve around changes in neuronal plasticity, primarily in the hippocampus, at both the structural and the functional levels. Chronic stress negatively regulates hippocampal function while antidepressants ameliorate the effects of stress on neuronal morphology and activity. Both stress and antidepressants have been shown to affect levels of brain-derived neurotrophic factor (BDNF) whose transcription is dependent on cAMP response element binding protein (CREB). BDNF itself has antidepressant-like actions and can induce transcription of a number of molecules. One class of genes regulated by both BDNF and serotonin (5-HT) are neuropeptides including VGF (non-acryonimic) which has a novel role in depression. Neuropeptides are important modulators of neuronal function but their role in affective disorders is just emerging. Recent studies demonstrate that VGF, which is also a CREB-dependent gene, is upregulated by antidepressant drugs and voluntary exercise and is reduced in animal models of depression. VGF enhances hippocampal synaptic plasticity as well as neurogenesis in the dentate gyrus but the mechanisms of antidepressant-like actions of VGF in behavioral paradigms are not known. We summarize experimental data describing the roles of BDNF, VGF and other neuropeptides in depression and how they may be acting through the generation of new neurons and altered synaptic activity. Understanding the molecular and cellular changes that underlie the actions of neuropeptides and how these adaptations result in antidepressant-like effects will aid in developing drugs that target novel pathways for major depressive disorders.
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Affiliation(s)
- Smita Thakker-Varia
- Department of Neuroscience and Cell Biology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, 683 Hoes Lane West, Robert Wood Johnson-School of Public Health 357A, Piscataway, NJ 08854-5635, United States
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21
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Bartolomucci A, Possenti R, Levi A, Pavone F, Moles A. The role of the vgf gene and VGF-derived peptides in nutrition and metabolism. GENES & NUTRITION 2007; 2:169-80. [PMID: 18850173 PMCID: PMC2474945 DOI: 10.1007/s12263-007-0047-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Accepted: 10/24/2006] [Indexed: 12/01/2022]
Abstract
Energy homeostasis is a complex physiological function coordinated at multiple levels. The issue of genetic regulation of nutrition and metabolism is attracting increasing interest and new energy homeostasis-regulatory genes are continuously identified. Among these genes, vgf is gaining increasing interest following two observations: (1) VGF-/- mice have a lean and hypermetabolic phenotype; (2) the first VGF-derived peptide involved in energy homeostasis, named TLQP-21, has been identified. The aim of this review will be to discuss the role of the vgf gene and VGF derived peptides in metabolic and nutritional functions. In particular we will: (1) provide a brief overview on the central systems regulating energy homeostasis and nutrition particularly focusing on the melanocortin system; (2) introduce the structure and molecular characteristic of vgf; (3) describe the phenotype of VGF deficient mice; (4) present recent data on the metabolic role of VGF-derived peptides, particularly focusing on one peptide named TLQP-21.
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Affiliation(s)
- Alessandro Bartolomucci
- Institute of Neuroscience, CNR, Via del Fosso di Fiorano 64, 00143 Rome, Italy
- Dipartimento di Biologia Evolutiva e Funzionale, Università di Parma, V.le G.P. Usberti 11A, 43100 Parma, Italy
| | - Roberta Possenti
- Department of Neuroscience, University of Roma II-Tor Vergata, Rome, Italy
- Institute of Neurobiology and Molecular Medicine, CNR, Rome, Italy
| | - Andrea Levi
- Institute of Neurobiology and Molecular Medicine, CNR, Rome, Italy
| | - Flaminia Pavone
- Institute of Neuroscience, CNR, Via del Fosso di Fiorano 64, 00143 Rome, Italy
| | - Anna Moles
- Institute of Neuroscience, CNR, Via del Fosso di Fiorano 64, 00143 Rome, Italy
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22
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Jethwa PH, Warner A, Nilaweera KN, Brameld JM, Keyte JW, Carter WG, Bolton N, Bruggraber M, Morgan PJ, Barrett P, Ebling FJP. VGF-derived peptide, TLQP-21, regulates food intake and body weight in Siberian hamsters. Endocrinology 2007; 148:4044-55. [PMID: 17463057 DOI: 10.1210/en.2007-0038] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The Siberian hamster survives winter by decreasing food intake and catabolizing abdominal fat reserves, resulting in a sustained, profound loss of body weight. VGF gene expression is photoperiodically regulated in the hypothalamus with significantly higher expression in lean Siberian hamsters. The aim of this study was to investigate the role of VGF in regulating these seasonal cycles by determining the effects of a VGF-derived peptide (TLQP-21) on food intake and body weight. Acute intracerebroventricular administration of TLQP-21 decreased food intake, and chronic treatment caused a sustained reduction in food intake and body weight and decreased abdominal fat depots. Behavioral analysis revealed that TLQP-21 reduced meal size but not the frequency of feeding bouts, suggesting a primary action on satiety. Hamsters treated with TLQP-21 lost a similar amount of weight as a pair-fed group in which food intake was matched to that of the TLQP-21-treated group. Central or peripheral treatment with TLQP-21 did not produce a significant effect on resting metabolic rate. We conclude that the primary action of TLQP-21 is to decrease food intake rather than increase energy expenditure. TLQP-21 treatment caused a decrease in UCP-1 mRNA in brown adipose tissue, but hypothalamic expression of orexigenic and anorexigenic neuropeptide genes remained unchanged after TLQP-21 treatment, although compensatory increases in NPY and AgRP mRNA were observed in the pair-fed hamsters. The effects of TLQP-21 administration are similar to those in hamsters in short days, suggesting that increased VGF activity may contribute to the hypophagia that underlies the seasonal catabolic state.
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Affiliation(s)
- Preeti H Jethwa
- School of Biomedical Sciences and Institute of Neuroscience, University of Nottingham Medical School, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom.
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23
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Dubois M, Vacher P, Roger B, Huyghe D, Vandewalle B, Kerr-Conte J, Pattou F, Moustaïd-Moussa N, Lang J. Glucotoxicity inhibits late steps of insulin exocytosis. Endocrinology 2007; 148:1605-14. [PMID: 17204559 DOI: 10.1210/en.2006-1022] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Prolonged exposure of beta-cells to high glucose (glucotoxicity) diminishes insulin secretion in response to glucose and has been linked to altered generation of metabolism-secretion coupling factors. We have investigated whether glucotoxicity may also alter calcium handling and late steps in secretion such as exocytosis. Clonal INS-1E beta-cells cultured at high glucose (20 or 30 mM vs. 5.5 mM) for 72 h exhibited elevated basal intracellular calcium ([Ca2+]i), which was KATP-channel dependent and due to long-term activation of protein kinase A. An increased amplitude and shortened duration of depolarization-evoked rises in [Ca2+]i were apparent. These changes were probably linked to the observed increased filling of intracellular stores and to short-term activation of protein kinase A. Insulin secretion was reduced not only by acute stimulation with either glucose or KCl but more importantly by direct calcium stimulation of permeabilized cells. These findings indicate a defect in the final steps of exocytosis. To confirm this, we measured expression levels of some 30 proteins implicated in trafficking/exocytosis of post-Golgi vesicles. Several proteins required for calcium-induced exocytosis of secretory granules were down-regulated, such as the soluble N-ethylmaleimide-sensitive factor-sensitive factor attachment receptor (SNARE) proteins VAMP-2 [vesicle (v)-SNARE, vesicle-associated membrane protein 2] and syntaxin 1 as well as complexin. VAMP-2 was also reduced in human islets. In contrast, cell immunostaining and expression levels of several fluorescent proteins suggested that other post-trans-Golgi trafficking steps and compartments are preserved and that cells were not degranulated. Thus, these studies indicate that, in addition to known metabolic changes, glucotoxicity impedes generation of signals for secretion and diminishes the efficiency of late steps in exocytosis.
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Affiliation(s)
- Mathilde Dubois
- Université de Bordeaux, Cell Biology Program, and Institut National de la Santé et de la Recherche Médicale E347, Pessac, France
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24
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Cocco C, Brancia C, Pirisi I, D'Amato F, Noli B, Possenti R, Ferri GL. VGF metabolic-related gene: distribution of its derived peptides in mammalian pancreatic islets. J Histochem Cytochem 2007; 55:619-28. [PMID: 17312015 DOI: 10.1369/jhc.6a7040.2007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The vgf gene has been shown to be involved in several metabolic pathways. Because the pancreas is crucial to metabolism and food intake, we studied the VGF peptides in bovine, rat, and pig Langherans islets using antisera raised against specific sites along the primary sequence of the rat/mouse and human VGF protein precursor. Whereas almost all of the pancreatic endocrine cells expressed vgf mRNA, when using the VGF antisera a different staining pattern became apparent. VGF(556-565) and VGF(282-291) immunoreactivity were exclusively found in delta somatostatin-producing cells, whereas the human C-terminus antiserum selectively immunolabeled alpha glucagon and pancreatic polypeptide cells. The same cells were decorated with the VGF(443-588) antiserum, which also weakly labeled beta insulin-secreting cells. Finally, the VGF(298-306) peptide and the rat C terminus were found in virtually all pancreatic endocrine cells. Using bovine, swine, and rat pancreatic extracts, data from chromatography and ELISA assay showed the presence of a high molecular mass form compatible with the proVGF and lower molecular mass fractions corresponding to short VGF peptides. In conclusion, selective VGF distribution may suggest a multifaceted cell type-specific processing of proVGF, resulting in different peptides probably involved in neuroendocrine regulatory metabolic mechanisms.
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Affiliation(s)
- Cristina Cocco
- Department of Cytomorphology, University of Cagliari, Monserrato, Italy.
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25
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Garcia AL, Han SK, Janssen WG, Khaing ZZ, Ito T, Glucksman MJ, Benson DL, Salton SRJ. A prohormone convertase cleavage site within a predicted alpha-helix mediates sorting of the neuronal and endocrine polypeptide VGF into the regulated secretory pathway. J Biol Chem 2005; 280:41595-608. [PMID: 16221685 DOI: 10.1074/jbc.m509122200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Distinct intracellular pathways are involved in regulated and constitutive protein secretion from neuronal and endocrine cells, yet the peptide signals and molecular mechanisms responsible for targeting and retention of soluble proteins in secretory granules are incompletely understood. By using confocal microscopy and subcellular fractionation, we examined trafficking of the neuronal and endocrine peptide precursor VGF that is stored in large dense core vesicles and undergoes regulated secretion. VGF cofractionated with secretory vesicle membranes but was not detected in detergent-resistant lipid rafts. Deletional analysis using epitope-tagged VGF suggested that the C-terminal 73-amino acid fragment of VGF, containing two predicted alpha-helical loops and four potential prohormone convertase (PC) cleavage sites, was necessary and sufficient with an N-terminal signal peptide-containing domain, for large dense core vesicle sorting and regulated secretion from PC12 and INS-1 cells. Further transfection analysis identified the sorting sequence as a compact C-terminal alpha-helix and embedded 564RRR566 PC cleavage site; mutation of the 564RRR566 PC site in VGF-(1-65): GFP:VGF-(545-617) blocked regulated secretion, whereas disruption of the alpha-helix had no effect. Mutation of the adjacent 567HFHH570 motif, a charged region that might enhance PC cleavage in acidic environments, also blocked regulated release. Finally, inhibition of PC cleavage in PC12 cells using the membrane-permeable synthetic peptide chloromethyl ketone (decanoyl-RVKR-CMK) blocked regulated secretion of VGF. Our studies define a critical RRR-containing C-terminal domain that targets VGF into the regulated pathway in neuronal PC12 and endocrine INS-1 cells, providing additional support for the proposed role that PCs and their cleavage sites play in regulated peptide secretion.
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Affiliation(s)
- Angelo L Garcia
- Fishberg Department of Neuroscience, Mount Sinai School of Medicine, New York, New York 10029, USA
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26
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Succu S, Cocco C, Mascia MS, Melis T, Melis MR, Possenti R, Levi A, Ferri GL, Argiolas A. Pro-VGF-derived peptides induce penile erection in male rats: possible involvement of oxytocin. Eur J Neurosci 2005; 20:3035-40. [PMID: 15579158 DOI: 10.1111/j.1460-9568.2004.03781.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The effect of five peptides derived from the C-terminal portion of rat pro-VGF (VGF(577-617), VGF(588-617), VGF(599-617), VGF(556-576) and VGF(588-597)) on penile erection was studied after injection into the hypothalamic paraventricular nucleus of male rats. VGF(577-617), VGF(588-617), VGF(599-617) and, to a lower extent, VGF(588-597) (0.1-2 microg) induced penile erection episodes in a dose-dependent manner when injected into the paraventricular nucleus, while VGF(556-576) was ineffective. VGF(588-617)-induced penile erection was reduced by nitro(omega)-L-arginine methylester (L-NAME; 20 microg), by morphine (5 microg) and by muscimol (1 microg), but not by dizocilpine [(+)MK-801; 1 microg], nor by cis-flupenthixol (10 microg) given into the paraventricular nucleus 10 min before the VGF peptide. d(CH2)5Tyr(Me)-Orn8-vasotocin (1 microg) effectively reduced VGF(588-617)-induced penile erection when given into the lateral ventricles but not when injected into the paraventricular nucleus. Immunocytochemistry with antibodies specific for the C-terminal nonapeptide sequence of pro-VGF (VGF(609-617)) revealed numerous neuronal fibres and terminals within the paraventricular nucleus, including its parvocellular components. Here, many immunostained neuronal terminals impinged on parvocellular oxytocinergic neurons. The present results show for the first time that certain pro-VGF C-terminus-derived peptides promote penile erection when injected into the paraventricular nucleus and suggest that, within this nucleus, these or closely related pro-VGF-derived peptides may be released to influence sexual function by activating paraventricular oxytocinergic neurons mediating penile erection.
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Affiliation(s)
- Salvatora Succu
- Bernard B. Brodie Department of Neuroscience and Center of Excellence for the Neurobiology of Addiction, S.P. Monserrato-Sestu, Km 0.700, 09042 Monserrato, University of Cagliari, Italy
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Levi A, Ferri GL, Watson E, Possenti R, Salton SRJ. Processing, distribution, and function of VGF, a neuronal and endocrine peptide precursor. Cell Mol Neurobiol 2004; 24:517-33. [PMID: 15233376 DOI: 10.1023/b:cemn.0000023627.79947.22] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
1. The vgf gene encodes a neuropeptide precursor with a restricted pattern of expression that is limited to a subset of neurons in the central and peripheral nervous systems and to specific populations of endocrine cells in the adenohypophysis, adrenal medulla, gastrointestinal tract, and pancreas. In responsive neurons, vgf transcription is upregulated by neurotrophins. the basis for the original identification of VGF as nerve growth factor- (NGF) inducible in PC12 cells (A. Levi, J. D. Eldridge, and B. M. Paterson, Science 229:393-395, 1985). 2. In this review, we shall summarize data concerning the transcriptional regulation of vgf in vitro, the structural organization of the vgf promoter as well as the transcription factors which regulate its activity. 3. On the basis of in situ hybridization and immunohistochemical studies, the in vivo tissue-specific expression of VGF during differentiation and in the adult will be summarized. 4. Parallel biochemical data will be reviewed, addressing the proteolytical processing of the pro-VGF precursor within the secretory compartment of neuroendocrine cells. 5. Finally, analysis of the phenotype of VGF knockout mice will be discussed, implying a nonredundant role of VGF products in the regulation of energy storage and expenditure.
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Affiliation(s)
- Andrea Levi
- Department of Neuroscience, University of Tor Vergata, Rome, Italy
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Brain-derived neurotrophic factor-induced gene expression reveals novel actions of VGF in hippocampal synaptic plasticity. J Neurosci 2003. [PMID: 14645472 DOI: 10.1523/jneurosci.23-34-10800.2003] [Citation(s) in RCA: 210] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Synaptic strengthening induced by brain-derived neurotrophic factor (BDNF) is associated with learning and is coupled to transcriptional activation. However, identification of the spectrum of genes associated with BDNF-induced synaptic plasticity and the correlation of expression with learning paradigms in vivo has not yet been studied. Transcriptional analysis of BDNF-induced synaptic strengthening in cultured hippocampal neurons revealed increased expression of the immediate early genes (IEGs), c-fos, early growth response gene 1 (EGR1), activity-regulated cytoskeletal-associated protein (Arc) at 20 min, and the secreted peptide VGF (non-acronymic) protein precursor at 3 hr. The induced genes served as prototypes to decipher mechanisms of both BDNF-induced transcription and plasticity. BDNF-mediated gene expression was tyrosine kinase B and mitogen-activated protein kinase-dependent, as demonstrated by pharmacological studies. Single-cell transcriptional analysis of Arc after whole-cell patch-clamp recordings indicated that increased gene expression correlated with enhancement of synaptic transmission by BDNF. Increased expression in vitro predicted elevations in vivo: VGF and the IEGs increased after trace eyeblink conditioning, a hippocampal-dependent learning paradigm. VGF protein was also upregulated by BDNF treatment and was expressed in a punctate manner in dissociated hippocampal neurons. Collectively, these findings suggested that the VGF neuropeptides may regulate synaptic function. We found a novel function for VGF by applying VGF peptides to neurons. C-terminal VGF peptides acutely increased synaptic charge in a dose-dependent manner, whereas N-terminal peptide had no effect. These observations indicate that gene profiling in vitro can reveal new mechanisms of synaptic strengthening associated with learning and memory.
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Trani E, Giorgi A, Canu N, Amadoro G, Rinaldi AM, Halban PA, Ferri GL, Possenti R, Schininà ME, Levi A. Isolation and characterization of VGF peptides in rat brain. Role of PC1/3 and PC2 in the maturation of VGF precursor. J Neurochem 2002; 81:565-74. [PMID: 12065665 DOI: 10.1046/j.1471-4159.2002.00842.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The neurotrophin responsive gene vgf is widely expressed in central and peripheral neurones, and in certain neuroendocrine cell populations. Its encoded VGF precursor protein (proVGF1: 617 amino acids in rat, 615 in man, > 85% homology) gives rise to several low molecular weight species. We studied a range of neuroendocrine and neuronal cells, in which VGF-processing products were prominent with an apparent molecular weight of 20 and 10 kDa (VGF20 and VGF10, respectively). Such peptides were recognized by antibodies specific for the C-terminal rat VGF nonapeptide, thus indicating that they included the C-terminus of proVGF. Ectopic expression of the neuroendocrine-specific prohormone convertases PC1/3 or PC2 in GH3 cells showed that both could generate VGF20, while VGF10 was preferentially produced by PC1/3. Site-directed mutagenesis was used to identify the KRKRKK(488) motif as the target within VGF sequence which leads to the production of VGF20. Molecular characterization of rat VGF10, on the other hand, revealed that this peptide is produced by cleavage at the RPR(555) site. By the combined use of high-resolution separation techniques, matrix-assisted laser desorption/ionization time of flight (MALDI-ToF) mass spectrometry and manual Edman degradation we identified in rat brain a VGF fragment analogous to bovine peptide V and two novel peptides also derived from the C-terminal region of proVGF.
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Affiliation(s)
- E Trani
- Istituto di Neurobiologia e Medicina Molecolare, CNR, Roma, Italy
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Groot M, Boxer LM, Thiel G. Nerve growth factor- and epidermal growth factor-regulated gene transcription in PC12 pheochromocytoma and INS-1 insulinoma cells. Eur J Cell Biol 2000; 79:924-35. [PMID: 11152283 DOI: 10.1078/0171-9335-00126] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
PC12 and INS-1 cells both express the nerve growth factor (NGF) receptors trkA and p75NTR and the epidermal growth factor receptor (EGF). In PC12 cells, NGF treatment initiates a signaling cascade that ultimately leads to a change of the genetic program of the cell. We have investigated the role of NGF in regulating gene transcription in PC12 and INS-1 cells, in order to define if there are NGF-regulated genes per se. Furthermore, to distinguish between growth factor stimulation via receptor tyrosine kinases in general and NGF-specific changes in gene transcription, we analyzed the effects of EGF on gene transcription. First, we tested the biological activities of fusion proteins consisting of the DNA-binding domain of the yeast transcription factor GAL4 and the phosphorylation-dependent activation domains of the transcription factors Elk1, CREB, ATF2 and c-jun in NGF- or EGF-treated PC12 cells. We found a striking increase in the transcriptional activity of the GAL4-Elk1 fusion protein that is a major substrate for the extracellular signal-regulated protein kinase (ERK). This effect was observed in NGF- as well as in EGF-treated PC12 cells. In INS-1 cells, however, the activity of the GAL4-Elk1 fusion protein was induced by NGF, but not by EGF. The effects of NGF and EGF on gene transcription were subsequently studied with plasmids containing reporter genes under control of the Egr-1, c-jun, HES-1 or Bc12 regulatory sequences. NGF stimulated Egr-1 promoter activities in PC12 and INS-1 cells, although the effect was much more pronounced in PC12 cells than in INS-1 cells. EGF also stimulated Egr-1 promoter activity in both PC12 and INS-1 cells. Stimulation of c-jun promoter activity by NGF was observed only in PC12 cells. Deletion mutagenesis demonstrated the importance of the 12-O-tetradecanoylphorbol-13-acetate response elements within the c-jun promoter for basal and NGF-mediated transcriptional induction. Likewise, NGF activated HES1 and Bcl2 P1 promoter activities in PC12 cells but not in INS-1 cells and EGF did not show any effects on these promoters. We conclude that in PC12 and INS-1 cells, NGF signaling leads to an activation of the ERK subtype of mitogen-activated protein kinases in the nucleus and a subsequent activation of Egr-1 gene transcription. The NGF-induced transcription of the c-jun, HES1 and Bc12 genes is, in contrast, cell type-specific, indicating that NGF can trigger different gene expression programs dependent on the signaling pathways present in a particular cell type. EGF is clearly able to activate gene transcription, suggesting that the differences in the biological activities of EGF and NGF cannot be explained by the inability of EGF to stimulate gene transcription.
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Affiliation(s)
- M Groot
- Medical Biochemistry and Molecular Biology, University of Saarland Medical School, Homburg, Germany
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31
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Salton SR, Ferri GL, Hahm S, Snyder SE, Wilson AJ, Possenti R, Levi A. VGF: a novel role for this neuronal and neuroendocrine polypeptide in the regulation of energy balance. Front Neuroendocrinol 2000; 21:199-219. [PMID: 10882540 DOI: 10.1006/frne.2000.0199] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insight into the mechanisms of action of neurotrophic growth factors has been obtained through the identification and characterization of gene products that are regulated or modified at the transcriptional, translational, and/or posttranslational level in response to neurotrophin treatment. VGF (non-acronymic) was identified approximately 15 years ago as a nerve growth factor (NGF)-regulated transcript in rat PC12 pheochromocytoma cells. Subsequent studies have demonstrated that neurotrophins such as NGF and brain-derived neurotrophic factor induce vgf gene expression relatively rapidly in PC12 cells and cultured cortical neurons, respectively, in comparison to less robust regulation by epidermal growth factor (EGF) and insulin, growth factors which do not trigger the neuronal differentiation of PC12 cells. vgf gene expression is stimulated in vitro by NGF and the ras/map kinase signaling cascade through a CREB-dependent mechanism, while in vivo, VGF mRNA levels are regulated by neuronal activity, including long-term potentiation, seizure, and injury. Both the mRNA and encoded approximately 68-kDa protein (VGF) are selectively synthesized in neuroendocrine and neuronal cells. The predicted VGF sequence is rich in paired basic amino acid residues that are potential sites for proteolytic processing, and VGF undergoes regulated release from dense core secretory vesicles. Although VGF mRNA is synthesized widely, by neurons in the brain, spinal cord, and peripheral nervous system, its expression is particularly abundant in the hypothalamus. In addition, VGF peptides are found in hypophysial, adrenal medullary, gastrointestinal, and pancreatic endocrine cells, suggesting important neuroendocrine functions. Recent analysis of VGF knockout mice indeed demonstrates that VGF plays a critical role in the control of energy homeostasis. VGF knockout mice are thin, small, hypermetabolic, hyperactive, and relatively infertile, with markedly reduced leptin levels and fat stores and altered hypothalamic pro-opiomelanocortin, neuropeptide Y, and agouti-related peptide expression. Coupled with the demonstration that VGF mRNA levels are induced in the normal mouse hypothalamic arcuate nuclei in response to fasting, important central and peripheral roles for VGF in the regulation of metabolism are suggested. Here we review previous studies of VGF in the broader context of its newly recognized role in the control of energy balance and propose several models and experimental approaches that may better define the mechanisms of action of VGF.
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Affiliation(s)
- S R Salton
- Fishberg Research Center for Neurobiology, Mount Sinai School of Medicine, New York, New York, 10029, USA.
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Comegys MM, Carreiro MP, Brown JF, Mazzacua A, Flanagan DL, Makarovskiy A, Lin SH, Hixson DC. C-CAM1 expression: differential effects on morphology, differentiation state and suppression of human PC-3 prostate carcinoma cells. Oncogene 1999; 18:3261-76. [PMID: 10359532 DOI: 10.1038/sj.onc.1202666] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Studies in rat prostate and liver have suggested that C-CAM1 is involved in the formation and maintenance of histotypic associations in tissues and possibly tumors. Most recently, C-CAM1 has been shown to suppress tumorigenicity of prostate and colon carcinoma cells. However, the mechanisms whereby C-CAM1 suppresses growth and the relationship of this activity to its proposed role in histotypic interactions remain largely unknown. In the present study, we have analysed the growth, phenotypic, morphological and ultrastructural characteristics of four human PC-3 prostate carcinoma cell lines transduced with C-CAM1 retrovirus. We report that three of four lines regained their tumorigenic phenotype in vivo while maintaining high levels of C-CAM1 expression and a growth retarded phenotype in vitro. These findings suggested that high levels of C-CAM1 expression were negatively influencing recovery during reconstitution after freezing or during the latency period after subcutaneous injection and that loss of suppression resulted from changes in expression of other molecules required for full disclosure of C-CAM1 mediated growth inhibition. Results from Northern blot and immunofluorescence analyses of tumor nodules demonstrated that C-CAM1 decreased rather than enhanced phenotypic differentiation and induced ultrastructural and morphological changes that occurred independently of tumor suppression.
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Affiliation(s)
- M M Comegys
- Department of Medical Oncology, Rhode Island Hospital/Brown University, Providence 02903, USA
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