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Dai HC, Ji RL, Tao YX. SHU9119 and MBP10 are biased ligands at the human melanocortin-4 receptor. Biochem Pharmacol 2024:116325. [PMID: 38815629 DOI: 10.1016/j.bcp.2024.116325] [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: 01/22/2024] [Revised: 05/24/2024] [Accepted: 05/27/2024] [Indexed: 06/01/2024]
Abstract
The melanocortin-4 receptor (MC4R), a G protein-coupled receptor, is critically involved in regulating energy homeostasis as well as modulation of reproduction and sexual function. Two peptide antagonists (SHU9119 and MBP10) were derived from the endogenous agonist α-melanocyte stimulating hormone. But their pharmacology at human MC4R is not fully understood. Herein, we performed detailed pharmacological studies of SHU9119 and MBP10 on wild-type (WT) and six naturally occurring constitutively active MC4Rs. Both ligands had no or negligible agonist activity in Gαs-cAMP signaling on WT MC4R, but stimulated extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation on WT and mutant MC4Rs. Mechanistic studies revealed that SHU9119 and MBP10 stimulated ERK1/2 signaling of MC4R by different mechanisms, with SHU9119-stimulated ERK1/2 signaling mediated by phosphatidylinositol 3-kinase (PI3K) and MBP10-initiated ERK1/2 activation through PI3K and β-arrestin. In summary, our studies demonstrated that SHU9119 and MBP10 were biased ligands for MC4R, preferentially activating ERK1/2 signaling through different mechanisms. SHU9119 acted as a biased ligand and MBP10 behaved as a biased allosteric modulator.
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Affiliation(s)
- Han-Chuan Dai
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States; College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei 430070, China.
| | - Ren-Lei Ji
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
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2
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Saneyasu T. Recent Research on Mechanisms of Feeding Regulation in Chicks. J Poult Sci 2024; 61:2024012. [PMID: 38681189 PMCID: PMC11039390 DOI: 10.2141/jpsa.2024012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Accepted: 04/02/2024] [Indexed: 05/01/2024] Open
Abstract
Food intake affects poultry productivity. A complete understanding of these regulatory mechanisms provides new strategies to improve productivity. Food intake is regulated by complex mechanisms involving many factors, including the central nervous system, gastrointestinal tract, hormones, and nutrients. Although several studies have been conducted to elucidate regulatory mechanisms in chickens, the mechanisms remain unclear. To update the current knowledge on feeding regulation in chickens, this review focuses on recent findings that have not been summarized in previous reviews, including spexins, adipokines, neurosecretory proteins GL and GM, and central intracellular signaling factors.
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Affiliation(s)
- Takaoki Saneyasu
- Graduate School of Agricultural Science, Kobe University, Kobe 657-8501,
Japan
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3
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Orlandi P, Banchi M, Vaglini F, Carli M, Aringhieri S, Bandini A, Pardini C, Viaggi C, Lai M, Alì G, Ottani A, Vandini E, Guidi P, Bernardeschi M, La Rocca V, Francia G, Fontanini G, Pistello M, Frenzilli G, Giuliani D, Scarselli M, Bocci G. Melanocortin receptor 4 as a new target in melanoma therapy: Anticancer activity of the inhibitor ML00253764 alone and in association with B-raf inhibitor vemurafenib. Biochem Pharmacol 2024; 219:115952. [PMID: 38036189 DOI: 10.1016/j.bcp.2023.115952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Accepted: 11/27/2023] [Indexed: 12/02/2023]
Abstract
The aim of our study is to investigate in vitro and in vivo MC4R as a novel target in melanoma using the selective antagonist ML00253764 (ML) alone and in combination with vemurafenib, a B-rafV600E inhibitor. The human melanoma B-raf mutated A-2058 and WM 266-4 cell lines were used. An MC4R null A-2058 cell line was generated using a CRISPR/Cas9 system. MC4R protein expression was analysed by western blotting, immunohistochemistry, and immunofluorescence. Proliferation and apoptotic assays were performed with ML00253764, whereas the synergism with vemurafenib was evaluated by the combination index (CI) and Loewe methods. ERK1/2 phosphorylation and BCL-XL expression were quantified by western blot. In vivo experiments were performed in Athymic Nude-Foxn1nu male mice, injecting subcutaneously melanoma cells, and treating animals with ML, vemurafenib and their concomitant combination. Comet and cytome assays were performed. Our results show that human melanoma cell lines A-2058 and WM 266-4, and melanoma human tissue, express functional MC4R receptors on their surface. MC4R receptors on melanoma cells can be inhibited by the selective antagonist ML, causing antiproliferative and proapoptotic activity through the inhibition of phosphorylation of ERK1/2 and a reduction of BCL-XL. The concomitant combination of vemurafenib and ML caused a synergistic effect on melanoma cells in vitro and inhibited in vivo tumor growth in a preclinical model, without causing mouse weight loss or genotoxicity. Our original research contributes to the landscape of pharmacological treatments for melanoma, providing MC4R antagonists as drugs that can be added to established therapies.
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Affiliation(s)
- Paola Orlandi
- Dipartimento di Medicina Clinica e Sperimentale, Università di Pisa, Pisa, Italy
| | - Marta Banchi
- Dipartimento di Medicina Clinica e Sperimentale, Università di Pisa, Pisa, Italy
| | - Francesca Vaglini
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Pisa, Italy
| | - Marco Carli
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Pisa, Italy
| | - Stefano Aringhieri
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Pisa, Italy
| | - Arianna Bandini
- Dipartimento di Medicina Clinica e Sperimentale, Università di Pisa, Pisa, Italy
| | - Carla Pardini
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Pisa, Italy
| | - Cristina Viaggi
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Pisa, Italy
| | - Michele Lai
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Pisa, Italy
| | - Greta Alì
- Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa, Pisa, Italy
| | - Alessandra Ottani
- Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Sezione di Farmacologia e Medicina Molecolare, Università di Modena e Reggio Emilia, Modena, Italy
| | - Eleonora Vandini
- Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Sezione di Farmacologia e Medicina Molecolare, Università di Modena e Reggio Emilia, Modena, Italy
| | - Patrizia Guidi
- Dipartimento di Medicina Clinica e Sperimentale, Università di Pisa, Pisa, Italy
| | | | - Veronica La Rocca
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Pisa, Italy; Scuola Superiore Sant'Anna, Pisa, Italy
| | - Giulio Francia
- Border Biomedical Research Center, University of Texas at El Paso (UTEP), El Paso, TX, USA
| | - Gabriella Fontanini
- Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa, Pisa, Italy
| | - Mauro Pistello
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Pisa, Italy
| | - Giada Frenzilli
- Dipartimento di Medicina Clinica e Sperimentale, Università di Pisa, Pisa, Italy
| | - Daniela Giuliani
- Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Sezione di Farmacologia e Medicina Molecolare, Università di Modena e Reggio Emilia, Modena, Italy
| | - Marco Scarselli
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Pisa, Italy
| | - Guido Bocci
- Dipartimento di Medicina Clinica e Sperimentale, Università di Pisa, Pisa, Italy.
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4
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Townsend LK, Steinberg GR. AMPK and the Endocrine Control of Metabolism. Endocr Rev 2023; 44:910-933. [PMID: 37115289 DOI: 10.1210/endrev/bnad012] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 03/10/2023] [Accepted: 04/24/2023] [Indexed: 04/29/2023]
Abstract
Complex multicellular organisms require a coordinated response from multiple tissues to maintain whole-body homeostasis in the face of energetic stressors such as fasting, cold, and exercise. It is also essential that energy is stored efficiently with feeding and the chronic nutrient surplus that occurs with obesity. Mammals have adapted several endocrine signals that regulate metabolism in response to changes in nutrient availability and energy demand. These include hormones altered by fasting and refeeding including insulin, glucagon, glucagon-like peptide-1, catecholamines, ghrelin, and fibroblast growth factor 21; adipokines such as leptin and adiponectin; cell stress-induced cytokines like tumor necrosis factor alpha and growth differentiating factor 15, and lastly exerkines such as interleukin-6 and irisin. Over the last 2 decades, it has become apparent that many of these endocrine factors control metabolism by regulating the activity of the AMPK (adenosine monophosphate-activated protein kinase). AMPK is a master regulator of nutrient homeostasis, phosphorylating over 100 distinct substrates that are critical for controlling autophagy, carbohydrate, fatty acid, cholesterol, and protein metabolism. In this review, we discuss how AMPK integrates endocrine signals to maintain energy balance in response to diverse homeostatic challenges. We also present some considerations with respect to experimental design which should enhance reproducibility and the fidelity of the conclusions.
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Affiliation(s)
- Logan K Townsend
- Centre for Metabolism Obesity and Diabetes Research, Hamilton, ON L8S 4L8, Canada
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Gregory R Steinberg
- Centre for Metabolism Obesity and Diabetes Research, Hamilton, ON L8S 4L8, Canada
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, ON L8S 4L8, Canada
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
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5
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Neurotransmitters in Type 2 Diabetes and the Control of Systemic and Central Energy Balance. Metabolites 2023; 13:metabo13030384. [PMID: 36984824 PMCID: PMC10058084 DOI: 10.3390/metabo13030384] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Revised: 02/10/2023] [Accepted: 02/13/2023] [Indexed: 03/08/2023] Open
Abstract
Efficient signal transduction is important in maintaining the function of the nervous system across tissues. An intact neurotransmission process can regulate energy balance through proper communication between neurons and peripheral organs. This ensures that the right neural circuits are activated in the brain to modulate cellular energy homeostasis and systemic metabolic function. Alterations in neurotransmitters secretion can lead to imbalances in appetite, glucose metabolism, sleep, and thermogenesis. Dysregulation in dietary intake is also associated with disruption in neurotransmission and can trigger the onset of type 2 diabetes (T2D) and obesity. In this review, we highlight the various roles of neurotransmitters in regulating energy balance at the systemic level and in the central nervous system. We also address the link between neurotransmission imbalance and the development of T2D as well as perspectives across the fields of neuroscience and metabolism research.
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6
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da Silva RKB, de Vasconcelos DAA, da Silva AVE, da Silva RPB, de Oliveira Neto OB, Galindo LCM. Effects of maternal high-fat diet on the hypothalamic components related to food intake and energy expenditure in mice offspring. Life Sci 2022; 307:120880. [PMID: 35963301 DOI: 10.1016/j.lfs.2022.120880] [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: 06/26/2022] [Revised: 08/02/2022] [Accepted: 08/08/2022] [Indexed: 11/25/2022]
Abstract
Maternal exposure to a high-fat diet (HFD) during pregnancy and lactation has been related to changes in the hypothalamic circuits involved in the regulation of food intake. Furthermore, maternal HFD during the critical period of development can alter the offspring's metabolic programming with long-term repercussions. This study systematically reviewed the effects of HFD consumption during pre-pregnancy, pregnancy and/or lactation. The main outcomes evaluated were food intake; body weight; cellular or molecular aspects of peptides and hypothalamic receptors involved in the regulation of energy balance in mice. Two independent authors performed a search in the electronic databases Medline/PubMed, LILACS, Web of Science, EMBASE, SCOPUS and Sigle via Open Gray. Included were experimental studies of mice exposed to HFD during pregnancy and/or lactation that evaluated body composition, food intake, energy expenditure and hypothalamic components related to energy balance. Internal validity was assessed using the SYRCLE risk of bias. The Kappa index was measured to analyze the agreement between reviewers. The PRISMA statement was used to report this systematic review. Most studies demonstrated that there was a higher body weight, body fat deposits and food intake, as well as alterations in the expression of hypothalamic neuropeptides in offspring that consumed HFD. Therefore, the maternal diet can affect the phenotype and metabolism of the offspring, in addition to harming the hypothalamic circuits and favoring the orexigenic pathways.
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Affiliation(s)
- Regina Katiuska Bezerra da Silva
- Post-Graduate Program in Nutrition, Physical Activity and Phenotypic Plasticity, Federal University of Pernambuco, 55608-680 Vitória de Santo Antão, PE, Brazil
| | - Diogo Antonio Alves de Vasconcelos
- Post-Graduate Program in Nutrition, Physical Activity and Phenotypic Plasticity, Federal University of Pernambuco, 55608-680 Vitória de Santo Antão, PE, Brazil; Department of Nutrition, Federal University of Pernambuco, 50670-901 Recife, PE, Brazil; Nutrition and Phenotypic Plasticity Study Unit, Department of Nutrition, Federal University of Pernambuco, 50670-901 Recife, PE, Brazil
| | | | - Roxana Patrícia Bezerra da Silva
- Post-Graduate Program in Nutrition, Physical Activity and Phenotypic Plasticity, Federal University of Pernambuco, 55608-680 Vitória de Santo Antão, PE, Brazil
| | | | - Lígia Cristina Monteiro Galindo
- Post-Graduate Program in Nutrition, Physical Activity and Phenotypic Plasticity, Federal University of Pernambuco, 55608-680 Vitória de Santo Antão, PE, Brazil; Department of Anatomy, Federal University of Pernambuco, 50670-901 Recife, PE, Brazil; Nutrition and Phenotypic Plasticity Study Unit, Department of Nutrition, Federal University of Pernambuco, 50670-901 Recife, PE, Brazil.
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7
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Hammad MM, Mohammad A, Alam-Eldin N, Madhu D, Al-Mulla F, Abu-Farha M, Abubaker J. Structural analysis of setmelanotide binding to MC4R variants in comparison to wild-type receptor. Life Sci 2022; 307:120857. [PMID: 35931197 DOI: 10.1016/j.lfs.2022.120857] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 07/18/2022] [Accepted: 07/30/2022] [Indexed: 11/27/2022]
Abstract
AIMS Melanocortin 4 receptor (MC4R) has a well-established role in regulating appetite, food intake and energy homeostasis. Setmelanotide is an MC4R agonist currently approved for weight loss in obese adults and children with mutations in components of the leptin-melanocortin pathway. This study aims to compare structural and functional aspects of the physiological MC4R agonist α-melanocyte-stimulating hormone (α-MSH) with setmelanotide. We also aim to show the binding affinity of setmelanotide to known MC4R human missense mutations associated with obesity. MAIN METHODS AutoDock Vina was used in the structural analysis to calculate induced fit docking scores of ligand binding to MC4R wild type or the selected variants. HEK293-MC4R were utilized in the functional analysis of MC4R-actiavted pathways upon stimulating with α-MSH or setmelanotide. KEY FINDINGS Our data shows that setmelanotide has a higher potency for cAMP formation and a weaker effect on ERK1/2 phosphorylation when compared to α-MSH indicating functional selectivity otherwise known as biased agonism. We also present structural data showing that setmelanotide has a higher binding affinity to MC4R compared to α-MSH. Lastly, we show that two loss-of-function and two gain-of-function MC4R variants change the conformation not only of the ligand binding pocket of the receptor but also of the peptide when bound to the receptor because the interaction network and the residues involved in the binding are altered. SIGNIFICANCE Taken together, our study provides important insights into the diversity of MC4R signaling pathways which will facilitate the development of personalized anti-obesity drugs via refining MC4R agonists.
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Affiliation(s)
- Maha M Hammad
- Biochemistry and Molecular Biology Department, Dasman Diabetes Institute, Kuwait
| | - Anwar Mohammad
- Biochemistry and Molecular Biology Department, Dasman Diabetes Institute, Kuwait
| | - Nada Alam-Eldin
- Biochemistry and Molecular Biology Department, Dasman Diabetes Institute, Kuwait
| | - Dhanya Madhu
- Biochemistry and Molecular Biology Department, Dasman Diabetes Institute, Kuwait
| | - Fahd Al-Mulla
- Genetics and Bioinformatics Department, Dasman Diabetes Institute, Kuwait
| | - Mohamed Abu-Farha
- Biochemistry and Molecular Biology Department, Dasman Diabetes Institute, Kuwait.
| | - Jehad Abubaker
- Biochemistry and Molecular Biology Department, Dasman Diabetes Institute, Kuwait.
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8
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The role of liver kinase B1 in tumor progression through regulation of lipid metabolism. CLINICAL & TRANSLATIONAL ONCOLOGY : OFFICIAL PUBLICATION OF THE FEDERATION OF SPANISH ONCOLOGY SOCIETIES AND OF THE NATIONAL CANCER INSTITUTE OF MEXICO 2022; 24:2045-2054. [PMID: 35896782 PMCID: PMC9522762 DOI: 10.1007/s12094-022-02863-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Accepted: 05/19/2022] [Indexed: 10/30/2022]
Abstract
The somatic mutation of liver kinase B1 (LKB1) has been implicated in various tumors, which is reflected in the survival, proliferation, and metastasis of tumor cells. However, the regulation of LKB1 in lipid metabolism, a process that is involved in tumor progression is not completely clear. We conclude that LKB1 deficiency results in abnormal expression and activation of multiple molecules related to lipid metabolism which locate downstream of AMP-activated protein kinase (AMPK) or salt-induced kinase (SIK). Abnormal lipid metabolism induced by LKB1 deficiency contributes to the proliferation and metastasis of tumor cells through energy regulation.
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9
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Analysis of the Glucose-Dependent Transcriptome in Murine Hypothalamic Cells. Cells 2022; 11:cells11040639. [PMID: 35203289 PMCID: PMC8870115 DOI: 10.3390/cells11040639] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 02/10/2022] [Accepted: 02/10/2022] [Indexed: 11/16/2022] Open
Abstract
Glucose provides vital energy for cells and contributes to gene expression. The hypothalamus is key for metabolic homeostasis, but effects of glucose on hypothalamic gene expression have not yet been investigated in detail. Thus, herein, we monitored the glucose-dependent transcriptome in murine hypothalamic mHypoA-2/10 cells by total RNA-seq analysis. A total of 831 genes were up- and 1390 genes were downregulated by at least 50%. Key genes involved in the cholesterol biosynthesis pathway were upregulated, and total cellular cholesterol levels were significantly increased by glucose. Analysis of single genes involved in fundamental cellular signaling processes also suggested a significant impact of glucose. Thus, we chose ≈100 genes involved in signaling and validated the effects of glucose on mRNA levels by qRT-PCR. We identified Gnai1–3, Adyc6, Irs1, Igfr1, Hras, and Elk3 as new glucose-dependent genes. In line with this, cAMP measurements revealed enhanced noradrenalin-induced cAMP levels, and reporter gene assays elevated activity of the insulin-like growth factor at higher glucose levels. Key data of our studies were confirmed in a second hypothalamic cell line. Thus, our findings link extra cellular glucose levels with hypothalamic lipid synthesis and pivotal intracellular signaling processes, which might be of particular interest in situations of continuously increased glucose levels.
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10
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Yang LK, Hou ZS, Tao YX. Biased signaling in naturally occurring mutations of G protein-coupled receptors associated with diverse human diseases. Biochim Biophys Acta Mol Basis Dis 2021; 1867:165973. [PMID: 32949766 PMCID: PMC7722056 DOI: 10.1016/j.bbadis.2020.165973] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 09/07/2020] [Accepted: 09/14/2020] [Indexed: 12/15/2022]
Abstract
G protein-coupled receptors (GPCRs) play critical roles in transmitting a variety of extracellular signals into the cells and regulate diverse physiological functions. Naturally occurring mutations that result in dysfunctions of GPCRs have been known as the causes of numerous diseases. Significant progresses have been made in elucidating the pathophysiology of diseases caused by mutations. The multiple intracellular signaling pathways, such as G protein-dependent and β-arrestin-dependent signaling, in conjunction with recent advances on biased agonism, have broadened the view on the molecular mechanism of disease pathogenesis. This review aims to briefly discuss biased agonism of GPCRs (biased ligands and biased receptors), summarize the naturally occurring GPCR mutations that cause biased signaling, and propose the potential pathophysiological relevance of biased mutant GPCRs associated with various endocrine diseases.
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Affiliation(s)
- Li-Kun Yang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Zhi-Shuai Hou
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
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11
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Yang LK, Tao YX. Alanine Scanning Mutagenesis of the DRYxxI Motif and Intracellular Loop 2 of Human Melanocortin-4 Receptor. Int J Mol Sci 2020; 21:ijms21207611. [PMID: 33076233 PMCID: PMC7589821 DOI: 10.3390/ijms21207611] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/10/2020] [Accepted: 10/11/2020] [Indexed: 12/15/2022] Open
Abstract
The melanocortin-4 receptor (MC4R) is a member of the G-protein-coupled receptor (GPCR) superfamily, which has been extensively studied in obesity pathogenesis due to its critical role in regulating energy homeostasis. Both the Gs-cAMP and ERK1/2 cascades are known as important intracellular signaling pathways initiated by the MC4R. The DRYxxI motif at the end of transmembrane domain 3 and the intracellular loop 2 (ICL2) are thought to be crucial for receptor function in several GPCRs. To study the functions of this domain in MC4R, we performed alanine-scanning mutagenesis on seventeen residues. We showed that one residue was critical for receptor cell surface expression. Eight residues were important for ligand binding. Mutations of three residues impaired Gs-cAMP signaling without changing the binding properties. Investigation on constitutive activities of all the mutants in the cAMP pathway revealed that six residues were involved in constraining the receptor in inactive states and five residues were important for receptor activation in the absence of an agonist. In addition, mutations of four residues impaired the ligand-stimulated ERK1/2 signaling pathway without affecting the binding properties. We also showed that some mutants were biased to the Gs-cAMP or ERK1/2 signaling pathway. In summary, we demonstrated that the DRYxxI motif and ICL2 were important for MC4R function.
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12
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Jayarajan V, Appukuttan A, Aslam M, Reusch P, Regitz-Zagrosek V, Ladilov Y. Regulation of AMPK activity by type 10 adenylyl cyclase: contribution to the mitochondrial biology, cellular redox and energy homeostasis. Cell Mol Life Sci 2019; 76:4945-4959. [PMID: 31172217 PMCID: PMC11105217 DOI: 10.1007/s00018-019-03152-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 05/06/2019] [Accepted: 05/13/2019] [Indexed: 01/28/2023]
Abstract
The downregulation of AMP-activated protein kinase (AMPK) activity contributes to numerous pathologies. Recent reports suggest that the elevation of cellular cAMP promotes AMPK activity. However, the source of the cAMP pool that controls AMPK activity remains unknown. Mammalian cells possess two cAMP sources: membrane-bound adenylyl cyclase (tmAC) and intracellularly localized, type 10 soluble adenylyl cyclase (sAC). Due to the localization of sAC and AMPK in similar intracellular compartments, we hypothesized that sAC may control AMPK activity. In this study, sAC expression and activity were manipulated in H9C2 cells, adult rat cardiomyocytes or endothelial cells. sAC knockdown depleted the cellular cAMP content and decreased AMPK activity in an EPAC-dependent manner. Functionally, sAC knockdown reduced cellular ATP content, increased mitochondrial ROS formation and led to mitochondrial depolarization. Furthermore, sAC downregulation led to EPAC-dependent mitophagy disturbance, indicated by an increased mitochondrial mass and unaffected mitochondrial biogenesis. Consistently, sAC overexpression or stimulation with bicarbonate significantly increased AMPK activity and cellular ATP content. In contrast, tmAC inhibition or stimulation produced no effect on AMPK activity. Therefore, the sAC-EPAC axis may regulate basal and induced AMPK activity and support mitophagy, cellular energy and redox homeostasis. The study argues for sAC as a potential target in treating pathologies associated with AMPK downregulation.
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Affiliation(s)
- Vignesh Jayarajan
- Charité, Universitätsmedizin Berlin, Institute of Gender in Medicine, Center for Cardiovascular Research, Berlin, Germany
- DZHK (German Center for Cardiovascular Research), Berlin Partner Site, Berlin, Germany
- Department of Clinical Pharmacology, Ruhr-University Bochum, Bochum, Germany
| | - Avinash Appukuttan
- Department of Clinical Pharmacology, Ruhr-University Bochum, Bochum, Germany
| | - Muhammad Aslam
- Internal Medicine I/Cardiology and Angiology, University Hospital of Giessen and Marburg, Giessen, Germany
- Experimental Cardiology, Justus Liebig University Giessen, Giessen, Germany
| | - Peter Reusch
- Department of Clinical Pharmacology, Ruhr-University Bochum, Bochum, Germany
| | - Vera Regitz-Zagrosek
- Charité, Universitätsmedizin Berlin, Institute of Gender in Medicine, Center for Cardiovascular Research, Berlin, Germany
- DZHK (German Center for Cardiovascular Research), Berlin Partner Site, Berlin, Germany
| | - Yury Ladilov
- Charité, Universitätsmedizin Berlin, Institute of Gender in Medicine, Center for Cardiovascular Research, Berlin, Germany.
- DZHK (German Center for Cardiovascular Research), Berlin Partner Site, Berlin, Germany.
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13
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Vamecq J, Papegay B, Nuyens V, Boogaerts J, Leo O, Kruys V. Mitochondrial dysfunction, AMPK activation and peroxisomal metabolism: A coherent scenario for non-canonical 3-methylglutaconic acidurias. Biochimie 2019; 168:53-82. [PMID: 31626852 DOI: 10.1016/j.biochi.2019.10.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 10/10/2019] [Indexed: 12/13/2022]
Abstract
The occurrence of 3-methylglutaconic aciduria (3-MGA) is a well understood phenomenon in leucine oxidation and ketogenesis disorders (primary 3-MGAs). In contrast, its genesis in non-canonical (secondary) 3-MGAs, a growing-up group of disorders encompassing more than a dozen of inherited metabolic diseases, is a mystery still remaining unresolved for three decades. To puzzle out this anthologic problem of metabolism, three clues were considered: (i) the variety of disorders suggests a common cellular target at the cross-road of metabolic and signaling pathways, (ii) the response to leucine loading test only discriminative for primary but not secondary 3-MGAs suggests these latter are disorders of extramitochondrial HMG-CoA metabolism as also attested by their failure to increase 3-hydroxyisovalerate, a mitochondrial metabolite accumulating only in primary 3-MGAs, (iii) the peroxisome is an extramitochondrial site possessing its own pool and displaying metabolism of HMG-CoA, suggesting its possible involvement in producing extramitochondrial 3-methylglutaconate (3-MG). Following these clues provides a unifying common basis to non-canonical 3-MGAs: constitutive mitochondrial dysfunction induces AMPK activation which, by inhibiting early steps in cholesterol and fatty acid syntheses, pipelines cytoplasmic acetyl-CoA to peroxisomes where a rise in HMG-CoA followed by local dehydration and hydrolysis may lead to 3-MGA yield. Additional contributors are considered, notably for 3-MGAs associated with hyperammonemia, and to a lesser extent in CLPB deficiency. Metabolic and signaling itineraries followed by the proposed scenario are essentially sketched, being provided with compelling evidence from the literature coming in their support.
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Affiliation(s)
- Joseph Vamecq
- Inserm, CHU Lille, Univ Lille, Department of Biochemistry and Molecular Biology, Laboratory of Hormonology, Metabolism-Nutrition & Oncology (HMNO), Center of Biology and Pathology (CBP) Pierre-Marie Degand, CHRU Lille, EA 7364 RADEME, University of North France, Lille, France.
| | - Bérengère Papegay
- Laboratory of Experimental Medicine (ULB unit 222), University Hospital Center, Charleroi, (CHU Charleroi), Belgium
| | - Vincent Nuyens
- Laboratory of Experimental Medicine (ULB unit 222), University Hospital Center, Charleroi, (CHU Charleroi), Belgium
| | - Jean Boogaerts
- Laboratory of Experimental Medicine (ULB unit 222), University Hospital Center, Charleroi, (CHU Charleroi), Belgium
| | - Oberdan Leo
- Laboratory of Immunobiology, Department of Molecular Biology, ULB Immunology Research Center (UIRC), Free University of Brussels (ULB), Gosselies, Belgium
| | - Véronique Kruys
- Laboratory of Molecular Biology of the Gene, Department of Molecular Biology, ULB Immunology Research Center (UIRC), Free University of Brussels (ULB), Gosselies, Belgium
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14
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Metabolism and mitochondria in polycystic kidney disease research and therapy. Nat Rev Nephrol 2019; 14:678-687. [PMID: 30120380 DOI: 10.1038/s41581-018-0051-1] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common, potentially lethal, monogenic diseases and is caused predominantly by mutations in polycystic kidney disease 1 (PKD1) and PKD2, which encode polycystin 1 (PC1) and PC2, respectively. Over the decades-long course of the disease, patients develop large fluid-filled renal cysts that impair kidney function, leading to end-stage renal disease in ~50% of patients. Despite the identification of numerous dysregulated pathways in ADPKD, the molecular mechanisms underlying the renal dysfunction from mutations in PKD genes and the physiological functions of the polycystin proteins are still unclear. Alterations in cell metabolism have emerged in the past decade as a hallmark of ADPKD. ADPKD cells shift their mode of energy production from oxidative phosphorylation to alternative pathways, such as glycolysis. In addition, the polycystins seem to play regulatory roles in modulating mechanisms and machinery related to energy production and utilization, including AMPK, PPARα, PGC1α, calcium signalling at mitochondria-associated membranes, mTORC1, cAMP and CFTR-mediated ion transport as well as the expression of crucial components of the mitochondrial energy production apparatus. In this Review, we explore these metabolic changes and discuss in detail the relationship between energy metabolism and ADPKD pathogenesis and identify potential therapeutic targets.
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15
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Aerobic Exercise Training Decreases Hepatic Asprosin in Diabetic Rats. J Clin Med 2019; 8:jcm8050666. [PMID: 31083617 PMCID: PMC6572469 DOI: 10.3390/jcm8050666] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 04/29/2019] [Accepted: 05/10/2019] [Indexed: 12/31/2022] Open
Abstract
Asprosin, a novel hormone released from white adipose tissue, regulates hepatic glucose metabolism and is pathologically elevated in the presence of insulin resistance. It is unknown whether aerobic exercise training affects asprosin levels in type 1 diabetes mellitus (T1DM). The aim of this study was to determine whether (1) aerobic exercise training could decrease asprosin levels in the liver of streptozotocin (STZ)-induced diabetic rats and (2) the reduction in asprosin levels could induce asprosin-dependent downstream pathways. Five-week-old male Sprague–Dawley rats were randomly divided into control, STZ-induced diabetes (STZ), and STZ with aerobic exercise training groups (n = 6/group). T1DM was induced by a single dose of STZ (65 mg/kg intraperitoneally (i.p.)). The exercise group was made to run on a treadmill for 60 min at a speed of 20 m/min, 4 days per week for 8 weeks. Aerobic exercise training reduced the protein levels of asprosin, PKA, and TGF-β but increased those of AMPK, Akt, PGC-1β, and MnSOD. These results suggest that aerobic exercise training affects hepatic asprosin-dependent PKA/TGF-β and AMPK downstream pathways in T1DM.
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16
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Wang W, Geng X, Lei L, Jia Y, Li Y, Zhou H, Verkman AS, Yang B. Aquaporin-3 deficiency slows cyst enlargement in experimental mouse models of autosomal dominant polycystic kidney disease. FASEB J 2019; 33:6185-6196. [PMID: 30768374 PMCID: PMC6463927 DOI: 10.1096/fj.201801338rrr] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Human autosomal dominant polycystic kidney disease (ADPKD) is characterized by bilateral renal cysts that lead to a decline in kidney function. Previous studies reported aquaporin (AQP)-3 expression in cysts derived from collecting ducts in ADPKD. To study the role of AQP3 in cyst development, we generated 2 polycystic kidney disease (PKD) mouse models: kidney-specific Pkd1 knockout mice and inducible Pkd1 knockout mice, each without and with AQP3 deletion. In both models, kidney sizes and cyst indexes were significantly reduced in AQP3-null PKD mice compared with AQP3-expressing PKD mice, with the difference seen mainly in collecting duct cysts. AQP3-deficient kidneys showed significantly reduced ATP content, increased phosphorylated (p)-AMPK, and decreased p-ERK and p-mammalian target of rapamycin (mTOR). In a matrix-grown Madin-Darby canine kidney cyst model, AQP3 expression promoted cyst enlargement and was associated with increased expression of hypoxia-inducible factor 1-α and glucose transporter 1 and increased glucose uptake. Our data suggest that the slowed renal cyst enlargement in AQP3 deficiency involves impaired energy metabolism in the kidney through AMPK and mTOR signaling and impaired cellular glucose uptake. These findings implicate AQP3 as a novel determinant of renal cyst enlargement and hence a potential drug target in ADPKD.-Wang, W., Geng, X., Lei, L., Jia, Y., Li, Y., Zhou, H., Verkman, A. S., Yang, B. Aquaporin-3 deficiency slows cyst enlargement in experimental mouse models of autosomal dominant polycystic kidney disease.
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Affiliation(s)
- Weiling Wang
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China;,State Key Laboratory of Natural and Biomimetic Drugs, Beijing, China;,Beijing Research Institute of Chinese Medicine, Beijing University of Chinese Medicine, Beijing, China
| | - Xiaoqiang Geng
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China;,State Key Laboratory of Natural and Biomimetic Drugs, Beijing, China
| | - Lei Lei
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China;,State Key Laboratory of Natural and Biomimetic Drugs, Beijing, China
| | - Yingli Jia
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China;,State Key Laboratory of Natural and Biomimetic Drugs, Beijing, China
| | - Yingjie Li
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China;,State Key Laboratory of Natural and Biomimetic Drugs, Beijing, China
| | - Hong Zhou
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China;,State Key Laboratory of Natural and Biomimetic Drugs, Beijing, China
| | - Alan S. Verkman
- Department of Medicine, University of California–San Francisco, San Francisco, California, USA; ,Department of Physiology, University of California–San Francisco, San Francisco, California, USA
| | - Baoxue Yang
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing, China;,State Key Laboratory of Natural and Biomimetic Drugs, Beijing, China;,Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing, China;,Correspondence: Department of Pharmacology, School of Basic Medical Sciences, Peking University, 38 Xueyuan Lu, Haidian District, 211 Building of Physiology, Beijing 100191, China. E-mail:
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17
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Kühnen P, Krude H, Biebermann H. Melanocortin-4 Receptor Signalling: Importance for Weight Regulation and Obesity Treatment. Trends Mol Med 2019; 25:136-148. [PMID: 30642682 DOI: 10.1016/j.molmed.2018.12.002] [Citation(s) in RCA: 100] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 12/03/2018] [Accepted: 12/04/2018] [Indexed: 01/08/2023]
Abstract
The melanocortin-4 receptor (MC4R) - embedded in the leptin-melanocortin pathway - is activated by proopiomelanocortin (POMC)-derived neuropeptides such as α- and β-melanocyte-stimulating hormone (MSH) and plays an important role in hypothalamic body-weight regulation. Accordingly, MC4R is a potential drug target to combat obesity. Previous attempts to develop MC4R agonists failed due to ineffectiveness or severe adverse events. Recently, a new generation of MC4R ligands was developed. Specifically, setmelanotide was found to be effective by inducing biased signalling of the MC4R and thereby reducing feelings of hunger and leading to substantial weight loss in patients with POMC or leptin receptor deficiency. This new potential pharmacological treatment option could be beneficial for further groups of obese patients with defects in the leptin-melanocortin signalling pathway.
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Affiliation(s)
- Peter Kühnen
- Institute for Experimental Pediatric Endocrinology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
| | - Heiko Krude
- Institute for Experimental Pediatric Endocrinology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Heike Biebermann
- Institute for Experimental Pediatric Endocrinology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
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18
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Wang B, Chen T, Wang J, Jia Y, Ren H, Wu F, Hu M, Chen Y. Methamphetamine modulates the production of interleukin-6 and tumor necrosis factor-alpha via the cAMP/PKA/CREB signaling pathway in lipopolysaccharide-activated microglia. Int Immunopharmacol 2018; 56:168-178. [PMID: 29414647 DOI: 10.1016/j.intimp.2018.01.024] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 01/15/2018] [Accepted: 01/16/2018] [Indexed: 01/01/2023]
Abstract
Methamphetamine (METH) elicits neuroinflammatory effects that may implicate its regulatory role on the microglial immune response. However, the mechanism underlying this remains unclear. In the present study, the effects of METH on lipopolysaccharide (LPS)-induced interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) productions were tested in BV-2 cells and primary microglial cells. Additionally, western blot analysis was used to examine the phosphorylation of mitogenactivated protein kinases (MAPKs). Next, we detected the alterations in cAMP content and the phosphorylation levels of CREB in microglial cells to determine the involvement of the cAMP/CREB signaling pathway. We also used an adenylyl cyclase (AC) agonist (forskolin) and antagonist (MDL-12330A) and a PKA antagonist (H89) to confirm their participation. We observed that METH alone did not affect the production of IL-6 or TNF-α. In contrast, METH augmented the IL-6 production and inhibited the TNF-α production induced by LPS. A similar effect of forskolin was also observed in BV-2 cells. While MAPK activation was not influenced by METH alone, the LPS-induced phosphorylation of p38, JNK and ERK1/2 were all reduced by METH. Both the concentration of cAMP and the phosphorylation of CREB were increased by METH in LPS-activated microglial cells. The effects of METH were altered by MDL-12330A and H89. Moreover, the inhibition of the phosphorylation of ERK1/2 by METH was also reversed. These results suggest that the differential regulation of IL-6 and TNF-α by METH in LPS-activated microglial cells may be attributable to the cAMP/PKA/CREB signaling pathway.
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Affiliation(s)
- Biao Wang
- Department of Immunology and Pathogenic Biology, College of Basic Medicine, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China
| | - Teng Chen
- Forensic Medicine College of Xi'an Jiaotong University, Key Laboratory of the Health Ministry for Forensic Medicine, Xi'an 710061, China
| | - Jing Wang
- Department of Immunology and Pathogenic Biology, College of Basic Medicine, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China
| | - Yuwei Jia
- Department of Immunology and Pathogenic Biology, College of Basic Medicine, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China
| | - Huixun Ren
- Department of Immunology and Pathogenic Biology, College of Basic Medicine, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China
| | - Feng Wu
- Graduate Teaching and Experiment Centre, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China
| | - Mei Hu
- Editorial Department of Infectious Disease Information, 302 Hospital of PLA, Beijing 100039, China
| | - Yanjiong Chen
- Department of Immunology and Pathogenic Biology, College of Basic Medicine, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China.
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19
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Wang X, Zhang ZF, Zheng GH, Wang AM, Sun CH, Qin SP, Zhuang J, Lu J, Ma DF, Zheng YL. Attenuation of hepatic steatosis by purple sweet potato colour is associated with blocking Src/ERK/C/EBPβ signalling in high-fat-diet–treated mice. Appl Physiol Nutr Metab 2017. [DOI: 10.1139/apnm-2016-0635] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Our previous work showed that purple sweet potato colour (PSPC), a class of naturally occurring anthocyanins, effectively improved hepatic glucose metabolic dysfunction in high-fat-diet (HFD)–treated mice. This study investigated the effects of PSPC on HFD-induced hepatic steatosis and the signalling events associated with these effects. Mice were divided into 4 groups: control group, HFD group, HFD+PSPC group, and PSPC group. PSPC was administered daily for 20 weeks at oral doses of 700 mg/(kg·day)−1). Our results showed that PSPC significantly improved obesity and related metabolic parameters, as well as liver injury in HFD-treated mice. Moreover, PSPC dramatically attenuated hepatic steatosis in HFD-treated mice. PSPC markedly prevented oxidative stress-mediated Src activation in HFD-treated mouse livers. Furthermore, PSPC feeding remarkably suppressed mitogen-activated protein kinase kinase/extracellular-signal-regulated kinase (MEK/ERK) signalling and consequent CCAAT/enhancer binding protein β (C/EBPβ) activation and restored AMPK activation in HFD-treated mouse livers, which was confirmed by U0126 treatment. Ultimately, PSPC feeding dramatically reduced protein expression of FAS and CD36 and the activation of ACC, and increased the protein expression of CPT1A in the livers of HFD-treated mice, indicating decreased lipogenesis and fatty acid uptake and enhanced fatty acid oxidation. In conclusion, PSPC exhibited beneficial effects on hepatic steatosis, which were associated with blocking Src and C/EBPβ activation.
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Affiliation(s)
- Xin Wang
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province 221116, PR China
- Key Laboratory of Biology and Genetic Improvement of Sweetpotato, Ministry of Agriculture, Jiangsu Xuzhou Sweetpotato Research Center, Xuzhou 221131, Jiangsu Province, PR China
| | - Zi-Feng Zhang
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province 221116, PR China
| | - Gui-Hong Zheng
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province 221116, PR China
| | - Ai-Min Wang
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province 221116, PR China
| | - Chun-Hui Sun
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province 221116, PR China
| | - Su-Ping Qin
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province 221116, PR China
| | - Juan Zhuang
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province 221116, PR China
| | - Jun Lu
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province 221116, PR China
| | - Dai-Fu Ma
- Key Laboratory of Biology and Genetic Improvement of Sweetpotato, Ministry of Agriculture, Jiangsu Xuzhou Sweetpotato Research Center, Xuzhou 221131, Jiangsu Province, PR China
| | - Yuan-Lin Zheng
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Jiangsu Normal University, Xuzhou 221116, Jiangsu Province 221116, PR China
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20
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Kumar R, Deep G, Wempe MF, Surek J, Kumar A, Agarwal R, Agarwal C. Procyanidin B2 3,3″-di-O-gallate induces oxidative stress-mediated cell death in prostate cancer cells via inhibiting MAP kinase phosphatase activity and activating ERK1/2 and AMPK. Mol Carcinog 2017; 57:57-69. [PMID: 28876465 DOI: 10.1002/mc.22731] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/26/2017] [Accepted: 09/05/2017] [Indexed: 12/14/2022]
Abstract
Neoplastic cells exhibit higher oxidative stress compared to normal cells; however, antioxidants based clinical trials have mostly failed. Another attractive therapeutic approach is to further increase the oxidative stress in cancer cells leading to cell death. Herein, we show that Procyanidin B2 3,3″-di-O-gallate (B2G2), the most active constituent of grape seed extract, treatment causes cell death in human prostate cancer (PCa) cells (LNCaP and 22Rv1) via increasing the reactive oxygen species (ROS) generation. Mechanistically, B2G2 treatment decreased the mitochondrial electron transport chain complex III activity leading to enhanced mitochondrial superoxide generation and decreased ATP production in LNCaP cells. Additional molecular studies revealed that B2G2-induced cell death was mediated mainly through ROS-induced sustained activation of ERK1/2, which was due to inhibition of MAP kinase phosphatase (MKP) activity as over-expression of MKP3 in LNCaP cells conferred significant protection against B2G2-induced cell death. Along with ERK1/2, AMP-activated protein kinase α (AMPKα) was also activated by B2G2 treatment, and pre-treatment with AMPKα inhibitor compound C significantly reversed the cytotoxic effects of B2G2 in LNCaP cells. Furthermore, pre-treatment of MKP3 over-expressing LNCaP cells with compound C further reduced the B2G2-induced cell death, suggesting the involvement of AMPKα along with MKP3 and ERK1/2 in the biological effects of B2G2. Together, these results for the first time identified that oxidative stress and MKP3 inhibition play a critical role in B2G2-induced cell death in PCa cells through sustained activation of both ERK1/2 and AMPKα. These results offer a unique opportunity to control this deadly malignancy through B2G2 use.
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Affiliation(s)
- Rahul Kumar
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy, University of Colorado Denver, Aurora, Colorado
| | - Gagan Deep
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy, University of Colorado Denver, Aurora, Colorado.,University of Colorado Cancer Center, University of Colorado Denver, Aurora, Colorado
| | - Michael F Wempe
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy, University of Colorado Denver, Aurora, Colorado.,University of Colorado Cancer Center, University of Colorado Denver, Aurora, Colorado
| | - Joseph Surek
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy, University of Colorado Denver, Aurora, Colorado
| | - Amit Kumar
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy, University of Colorado Denver, Aurora, Colorado
| | - Rajesh Agarwal
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy, University of Colorado Denver, Aurora, Colorado.,University of Colorado Cancer Center, University of Colorado Denver, Aurora, Colorado
| | - Chapla Agarwal
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy, University of Colorado Denver, Aurora, Colorado.,University of Colorado Cancer Center, University of Colorado Denver, Aurora, Colorado
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21
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Aoyama K, Bhadhprasit W, Watabe M, Wang F, Matsumura N, Nakaki T. GTRAP3-18 regulates food intake and body weight by interacting with pro-opiomelanocortin. FASEB J 2017; 32:330-341. [PMID: 28904020 DOI: 10.1096/fj.201700421r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 08/28/2017] [Indexed: 01/16/2023]
Abstract
Pro-opiomelanocortin (POMC)-expressing neurons provide α-melanocyte-stimulating hormone (α-MSH), which stimulates melanocortin 4 receptor to induce hypophagia by AMPK inhibition in the hypothalamus. α-MSH is produced by POMC cleavage in secretory granules and released. However, it is not known yet whether any posttranscriptional regulatory mechanism of POMC signaling exists upstream of the secretory granules in neurons. Here we show that glutamate transporter-associated protein 3-18 (GTRAP3-18), an anchor protein that retains interacting proteins in the endoplasmic reticulum, is a critical regulator of food intake and body weight by interacting with POMC. GTRAP3-18-deficient mice showed hypophagia, lean bodies, and lower blood glucose, insulin, and leptin levels with increased serum and brain α-MSH levels, leading to AMPK inhibition. Intraperitoneal glucose tolerance tests revealed significantly decreased blood glucose levels and areas under the curve in GTRAP3-18-deficient mice compared to wild-type mice. An intracerebroventricular infusion of a selective melanocortin 4 receptor antagonist to GTRAP3-18-deficient mice significantly increased their food intake and body weight. A fluorescence resonance energy transfer study showed an interaction between GTRAP3-18 and POMC in vitro These findings suggest that activation of the melanocortin pathway by modulating GTRAP3-18/POMC interaction could be an alternative strategy for obesity and/or type 2 diabetes.-Aoyama, K., Bhadhprasit, W., Watabe, M., Wang, F., Matsumura, N., Nakaki, T. GTRAP3-18 regulates food intake and body weight by interacting with pro-opiomelanocortin.
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Affiliation(s)
- Koji Aoyama
- Department of Pharmacology, Teikyo University School of Medicine, Tokyo, Japan
| | | | - Masahiko Watabe
- General Medical Education Center (G-MEC), Teikyo University School of Medicine, Tokyo, Japan
| | - Fan Wang
- Department of Pharmacology, Teikyo University School of Medicine, Tokyo, Japan
| | - Nobuko Matsumura
- Department of Pharmacology, Teikyo University School of Medicine, Tokyo, Japan
| | - Toshio Nakaki
- Department of Pharmacology, Teikyo University School of Medicine, Tokyo, Japan;
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22
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Vaglini F, Pardini C, Di Desidero T, Orlandi P, Pasqualetti F, Ottani A, Pacini S, Giuliani D, Guarini S, Bocci G. Melanocortin Receptor-4 and Glioblastoma Cells: Effects of the Selective Antagonist ML00253764 Alone and in Combination with Temozolomide In Vitro and In Vivo. Mol Neurobiol 2017; 55:4984-4997. [DOI: 10.1007/s12035-017-0702-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 07/31/2017] [Indexed: 12/13/2022]
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23
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Tian Y, Qi M, Wang Z, Wu C, Sun Z, Li Y, Sha S, Du Y, Chen L, Chen L. Activation of Transient Receptor Potential Vanilloid 4 Impairs the Dendritic Arborization of Newborn Neurons in the Hippocampal Dentate Gyrus through the AMPK and Akt Signaling Pathways. Front Mol Neurosci 2017; 10:190. [PMID: 28663724 PMCID: PMC5471311 DOI: 10.3389/fnmol.2017.00190] [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: 02/22/2017] [Accepted: 05/29/2017] [Indexed: 11/13/2022] Open
Abstract
Neurite growth is an important process for the adult hippocampal neurogenesis which is regulated by a specific range of the intracellular free Ca2+ concentration ([Ca2+]i). Transient receptor potential vanilloid 4 (TRPV4) is a calcium-permeable channel and activation of it causes an increase in [Ca2+]i. We recently reported that TRPV4 activation promotes the proliferation of stem cells in the adult hippocampal dentate gyrus (DG). The present study aimed to examine the effect of TRPV4 activation on the dendrite morphology of newborn neurons in the adult hippocampal DG. Here, we report that intracerebroventricular injection of the TRPV4 agonist GSK1016790A for 5 days (GSK1016790A-injected mice) reduced the number of doublecortin immunopositive (DCX+) cells and DCX+ fibers in the hippocampal DG, showing the impaired dendritic arborization of newborn neurons. The phosphorylated AMP-activated protein kinase (p-AMPK) protein level increased from 30 min to 2 h, and then decreased from 1 to 5 days after GSK1016790A injection. The phosphorylated protein kinase B (p-Akt) protein level decreased from 30 min to 5 days after GSK1016790A injection; this decrease was markedly attenuated by the AMPK antagonist compound C (CC), but not by the AMPK agonist AICAR. Moreover, the phosphorylated mammalian target of rapamycin (mTOR) and p70 ribosomal S6 kinase (p70S6k) protein levels were decreased by GSK1016790A; these changes were sensitive to 740 Y-P and CC. The phosphorylation of glycogen synthase kinase 3β (GSK3β) at Y216 was increased by GSK1016790A, and this change was accompanied by increased phosphorylation of microtubule-associated protein 2 (MAP2) and collapsin response mediator protein-2 (CRMP-2). These changes were markedly blocked by 740 Y-P and CC. Finally, GSK1016790A-induced decrease of DCX+ cells and DCX+ fibers was markedly attenuated by 740 Y-P and CC, but was unaffected by AICAR. We conclude that TRPV4 activation impairs the dendritic arborization of newborn neurons through increasing AMPK and inhibiting Akt to inhibit the mTOR-p70S6k pathway, activate GSK3β and thereby result in the inhibition of MAP2 and CRMP-2 function.
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Affiliation(s)
- Yujing Tian
- Department of Physiology, Nanjing Medical UniversityNanjing, China
| | - Mengwen Qi
- Department of Physiology, Nanjing Medical UniversityNanjing, China
| | - Zhouqing Wang
- Department of Physiology, Nanjing Medical UniversityNanjing, China
| | - Chunfeng Wu
- Department of Neurology, Children's Hospital of Nanjing Medical UniversityNanjing, China
| | - Zhen Sun
- Department of Tangshan Branch, Jinling Hospital, Nanjing UniversityNanjing, China
| | - Yingchun Li
- Department of Physiology, Nanjing Medical UniversityNanjing, China
| | - Sha Sha
- Department of Physiology, Nanjing Medical UniversityNanjing, China
| | - Yimei Du
- Research Center of Ion Channelopathy, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and TechnologyWuhan, China
| | - Lei Chen
- Department of Physiology, Nanjing Medical UniversityNanjing, China.,Neuroprotective Drug Discovery Center, Nanjing Medical UniversityNanjing, China
| | - Ling Chen
- Department of Physiology, Nanjing Medical UniversityNanjing, China
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Yang LK, Tao YX. Biased signaling at neural melanocortin receptors in regulation of energy homeostasis. Biochim Biophys Acta Mol Basis Dis 2017; 1863:2486-2495. [PMID: 28433713 DOI: 10.1016/j.bbadis.2017.04.010] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 04/09/2017] [Accepted: 04/10/2017] [Indexed: 12/15/2022]
Abstract
The global prevalence of obesity highlights the importance of understanding on regulation of energy homeostasis. The central melanocortin system is an important intersection connecting the neural pathways controlling satiety and energy expenditure to regulate energy homeostasis by sensing and integrating the signals of external stimuli. In this system, neural melanocortin receptors (MCRs), melanocortin-3 and -4 receptors (MC3R and MC4R), play crucial roles in the regulation of energy homeostasis. Recently, multiple intracellular signaling pathways and biased signaling at neural MCRs have been discovered, providing new insights into neural MCR signaling. This review attempts to summarize biased signaling including biased receptor mutants (both naturally occurring and lab-generated) and biased ligands at neural MCRs, and to provide a better understanding of obesity pathogenesis and new therapeutic implications for obesity treatment.
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Affiliation(s)
- Li-Kun Yang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
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Abstract
Obesity-related co-morbidities decrease life quality, reduce working ability and lead to early death. The total amount of dietary fat consumption may be the most potent food-related risk factor for weight gain. In this respect, dietary intake of high-caloric, high-fat diets due to chronic over-eating and sedentary lifestyle lead to increased storage of triglycerides not only in adipose tissue but also ectopically in other tissues . Increased plasma concentrations of non-esterified free fatty acids and lipid-overloaded hypertrophic adipocytes may cause insulin resistance in an inflammation-independent manner. Even in the absence of metabolic disorders, mismatch between fatty acid uptake and utilization leads to the accumulation of toxic lipid species resulting in organ dysfunction. Lipid-induced apoptosis, ceramide accumulation, reactive oxygen species overproduction, endoplasmic reticulum stress, and mitochondrial dysfunction may play role in the pathogenesis of lipotoxicity. The hypothalamus senses availability of circulating levels of glucose, lipids and amino acids, thereby modifies feeding according to the levels of those molecules. However, the hypothalamus is also similarly vulnerable to lipotoxicity as the other ectopic lipid accumulated tissues. Chronic overnutrition most likely provides repetitive and persistent signals that up-regulate inhibitor of nuclear factor kappa B kinase beta subunit/nuclear factor kappa B (IKKβ/NF-κB) in the hypothalamus before the onset of obesity. However, the mechanisms by which high-fat diet induced peripheral signals affect the hypothalamic arcuate nucleus remain largely unknown. In this chapter, besides lipids and leptin, the role of glucose and insulin on specialized fuel-sensing neurons of hypothalamic neuronal circuits has been debated.
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Xu M, Alwahsh SM, Ramadori G, Kollmar O, Slotta JE. Upregulation of hepatic melanocortin 4 receptor during rat liver regeneration. J Surg Res 2016; 203:222-30. [DOI: 10.1016/j.jss.2013.12.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 11/10/2013] [Accepted: 12/20/2013] [Indexed: 12/19/2022]
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Yang Z, Tao YX. Biased signaling initiated by agouti-related peptide through human melanocortin-3 and -4 receptors. Biochim Biophys Acta Mol Basis Dis 2016; 1862:1485-94. [PMID: 27208795 DOI: 10.1016/j.bbadis.2016.05.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 05/09/2016] [Accepted: 05/16/2016] [Indexed: 01/01/2023]
Abstract
The neural melanocortin receptors (MCRs), melanocortin-3 and -4 receptors (MC3R and MC4R), have been increasingly recognized as important regulators of energy homeostasis. The orexigenic agouti-related peptide (AgRP), initially identified as an endogenous antagonist for both neural MCRs, has been suggested to be a biased agonist of MC4R independent of its antagonizing effects. In the present study, we sought to determine the potential of AgRP to regulate the activation of intracellular kinases, including extracellular signal-regulated kinase 1 and 2 (ERK1/2), AKT and AMP-activated protein kinase (AMPK), through neural MCRs. We showed that AgRP acted as a biased agonist in human MC3R (hMC3R), decreasing cAMP activity of constitutively active mutant (F347A) hMC3R but stimulating ERK1/2 activation in both wide type and F347A hMC3Rs. AgRP-stimulated ERK1/2 phosphorylation through MC3R was abolished by protein kinase A (PKA) inhibitor H-89 but not Rp-cAMPS, whereas AgRP-initiated ERK1/2 activation through MC4R was inhibited by phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin and LY294002. Both NDP-MSH and AgRP treatment induced significant AKT phosphorylation in GT1-7 cells but not in MC3R- or MC4R-transfected HEK293T cells. The phosphorylated AMPK levels in both GT1-7 cells and HERK293T cells transfected with neural MCRs were significantly decreased upon stimulation with NDP-MSH but not with AgRP. In summary, we provided novel data for AgRP-initiated multiple intracellular signaling pathways, demonstrating biased agonism of AgRP in both neural MCRs, leading to a better understanding of neural MCR pharmacology.
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MESH Headings
- AMP-Activated Protein Kinases/metabolism
- Agouti-Related Protein/metabolism
- Amino Acid Substitution
- Central Nervous System/metabolism
- Cyclic AMP/metabolism
- HEK293 Cells
- Humans
- Kinetics
- Ligands
- MAP Kinase Signaling System
- Mutagenesis, Site-Directed
- Peptide Fragments/metabolism
- Proto-Oncogene Proteins c-akt/metabolism
- Receptor, Melanocortin, Type 3/agonists
- Receptor, Melanocortin, Type 3/genetics
- Receptor, Melanocortin, Type 3/metabolism
- Receptor, Melanocortin, Type 4/agonists
- Receptor, Melanocortin, Type 4/genetics
- Receptor, Melanocortin, Type 4/metabolism
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Signal Transduction
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Affiliation(s)
- Zhao Yang
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
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Lauffer L, Glas E, Gudermann T, Breit A. Endogenous 5-HT2C Receptors Phosphorylate the cAMP Response Element Binding Protein via Protein Kinase C-Promoted Activation of Extracellular-Regulated Kinases-1/2 in Hypothalamic mHypoA-2/10 Cells. J Pharmacol Exp Ther 2016; 358:39-49. [PMID: 27189964 DOI: 10.1124/jpet.116.232397] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 04/25/2016] [Indexed: 02/01/2023] Open
Abstract
Serotonin 5-HT2C receptors (5-HT2CR) activate Gq proteins and are expressed in the central nervous system (CNS). 5-HT2CR regulate emotion, feeding, reward, or cognition and may serve as promising drug targets to treat psychiatric disorders or obesity. Owing to technical difficulties in isolating cells from the CNS and the lack of suitable cell lines endogenously expressing 5-HT2CR, our knowledge about this receptor subtype in native environments is rather limited. The hypothalamic mHypoA-2/10 cell line was recently established and resembles appetite-regulating hypothalamic neurons of the paraventricular nucleus (PVN), where 5-HT2CR have been detected in vivo. Therefore, we tested mHypoA-2/10 cells for endogenous 5-HT2CR expression. Serotonin or the 5-HT2CR preferential agonist WAY-161,503 initiated cAMP response element (CRE)-dependent gene transcription with EC50 values of 15.5 ± 9.8 and 1.1 ± 0.9 nM, respectively. Both responses were blocked by two unrelated 5-HT2CR-selective antagonists (SB-242,084, RS-102,221) but not by a 5-HT2AR (EMD-281,014) or 5-HT2BR (RS-127,455) antagonists. By single-cell calcium imaging, we found that serotonin and WAY-161,503 induced robust calcium transients, which were also blunted by both 5-HT2CR antagonists. Additionally we revealed, first, that 5-HT2CR induced CRE activation via protein kinase C (PKC)-mediated engagement of extracellular-regulated kinases-1/2 and, second, that intrinsic activity of WAY-161,503 was in the range of 0.3-0.5 compared with serotonin, defining the frequently used 5-HT2CR agonist as a partial agonist of endogenous 5-HT2CR. In conclusion, we have shown that hypothalamic mHypoA-2/10 cells endogenously express 5-HT2CR and thus are the first cell line in which to analyze 5-HT2CR pharmacology, signaling, and regulation in its natural environment.
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Affiliation(s)
- Lisa Lauffer
- Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität München, München, Germany
| | - Evi Glas
- Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität München, München, Germany
| | - Thomas Gudermann
- Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität München, München, Germany
| | - Andreas Breit
- Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität München, München, Germany
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Lee YJ, Choi SY, Yang JH. AMP-activated protein kinase is involved in perfluorohexanesulfonate-induced apoptosis of neuronal cells. CHEMOSPHERE 2016; 149:1-7. [PMID: 26826296 DOI: 10.1016/j.chemosphere.2016.01.073] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 11/24/2015] [Accepted: 01/18/2016] [Indexed: 06/05/2023]
Abstract
Perfluorohexanesulfonate (PFHxS), one of the major perfluoroalkyl compounds (PFCs), has been used in a variety of industrial and consumer applications and detected in serum in the general population. This raised a concern over its possible detrimental health effects, including neurotoxic effects. We have previously shown that PFHxS induced neuronal apoptosis via the NMDA receptor-mediated extracellular signal-regulated kinase (ERK) pathway. Recently, it has been reported that AMP-activated protein kinase (AMPK) acts as a key signal molecule in neuronal excitotoxicity as well as providing a neuroprotective function. In the present study, we have examined the involvement of AMPK in PFHxS-induced neuronal apoptosis using neuronal differentiated PC12 cells. PFHxS induced significant increases in intracellular [Ca(2+)] via the NMDA receptor and the L-type voltage-gated calcium channel (L-VGCC). The inhibition of Ca(2+) loading by the NMDA receptor antagonist, MK801 and the L-VGCC blockers, nifedipine and diltiazem significantly reduced PFHxS-induced apoptosis. PFHxS induced sustained activation of AMPK and the inhibition of AMPK activation by compound C and AMPK siRNA significantly reduced PFHxS-induced caspase-3 activity. These results indicate the pro-apoptotic role of AMPK. The activation of AMPK was attenuated by MK801, nifedipine and diltiazem. However, the activation of AMPK was not affected by the ERK inhibitor, PD98059. Likewise, ERK activation was not affected by compound C but was substantially reduced by MK801, nifedipine or diltiazem. This suggests that the activation of AMPK and ERK is regulated by intracellular Ca(2+) loading in distinct pathways. Taken together, PFHxS-induced neuronal apoptosis is mediated by AMPK and ERK pathways, which are distinctly regulated by increased intracellular Ca(2+) via the NMDA receptor and L-VGCC.
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Affiliation(s)
- Youn Ju Lee
- Department of Pharmacology/Toxicology, School of Medicine, Catholic University of Daegu, Daegu, Republic of Korea
| | - So-Young Choi
- Department of Pharmacology/Toxicology, School of Medicine, Catholic University of Daegu, Daegu, Republic of Korea
| | - Jae-Ho Yang
- Department of Pharmacology/Toxicology, School of Medicine, Catholic University of Daegu, Daegu, Republic of Korea.
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Quiñones M, Al-Massadi O, Gallego R, Fernø J, Diéguez C, López M, Nogueiras R. Hypothalamic CaMKKβ mediates glucagon anorectic effect and its diet-induced resistance. Mol Metab 2015; 4:961-70. [PMID: 26909312 PMCID: PMC4731730 DOI: 10.1016/j.molmet.2015.09.014] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 09/29/2015] [Accepted: 09/30/2015] [Indexed: 01/23/2023] Open
Abstract
Objective Glucagon receptor antagonists and humanized glucagon antibodies are currently studied as promising therapies for obesity and type II diabetes. Among its variety of actions, glucagon reduces food intake, but the molecular mechanisms mediating this effect as well as glucagon resistance are totally unknown. Methods Glucagon and adenoviral vectors were administered in specific hypothalamic nuclei of lean and diet-induced obese rats. The expression of neuropeptides controlling food intake was performed by in situ hybridization. The regulation of factors of the glucagon signaling pathway was assessed by western blot. Results The central injection of glucagon decreased feeding through a hypothalamic pathway involving protein kinase A (PKA)/Ca2+-calmodulin-dependent protein kinase kinase β (CaMKKβ)/AMP-activated protein kinase (AMPK)-dependent mechanism. More specifically, the central injection of glucagon increases PKA activity and reduces protein levels of CaMKKβ and its downstream target phosphorylated AMPK in the hypothalamic arcuate nucleus (ARC). Consistently, central glucagon significantly decreased AgRP expression. Inhibition of PKA and genetic activation of AMPK in the ARC blocked glucagon-induced anorexia in lean rats. Genetic down-regulation of glucagon receptors in the ARC stimulates fasting-induced hyperphagia. Although glucagon was unable to decrease food intake in DIO rats, glucagon sensitivity was restored after inactivation of CaMKKβ, specifically in the ARC. Thus, glucagon decreases food intake acutely via PKA/CaMKKβ/AMPK dependent pathways in the ARC, and CaMKKβ mediates its obesity-induced hypothalamic resistance. Conclusions This work reveals the molecular underpinnings by which glucagon controls feeding that may lead to a better understanding of disease states linked to anorexia and cachexia. Glucagon stimulates PKA and inhibits CaMKKβ and AMPK in the arcuate nucleus (ARC). Down-regulation of glucagon receptor in the ARC increases fasting-induced hyperphagia. Glucagon is unable to decrease food intake in diet-induced obese (DIO) rats. In DIO rats, glucagon fails to alter CaMKKβ and its downstream targets AMPK and pACC. Down-regulation of CaMKKβ in the ARC restores glucagon sensitivity in obese rodents.
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Affiliation(s)
- Mar Quiñones
- Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Omar Al-Massadi
- Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Rosalía Gallego
- Department of Morphological Sciences, School of Medicine, University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain
| | - Johan Fernø
- Department of Clinical Science, K. G. Jebsen Center for Diabetes Research, University of Bergen, Bergen, Norway
| | - Carlos Diéguez
- Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Miguel López
- Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Ruben Nogueiras
- Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela, 15782, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
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31
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Borth H, Weber N, Meyer D, Wartenberg A, Arlt E, Zierler S, Breit A, Wennemuth G, Gudermann T, Boekhoff I. The IP3 R Binding Protein Released With Inositol 1,4,5-Trisphosphate Is Expressed in Rodent Reproductive Tissue and Spermatozoa. J Cell Physiol 2015; 231:1114-29. [PMID: 26439876 DOI: 10.1002/jcp.25209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 09/30/2015] [Indexed: 11/08/2022]
Abstract
Besides its capacity to inhibit the 1,4,5-trisphosphate (IP3) receptor, the regulatory protein IRBIT (IP3 receptor binding protein released with IP3) is also able to control the activity of numerous ion channels and electrolyte transporters and thereby creates an optimal electrolyte composition of various biological fluids. Since a reliable execution of spermatogenesis and sperm maturation critically depends on the establishment of an adequate microenvironment, the expression of IRBIT in male reproductive tissue was examined using immunohistochemical approaches combined with biochemical fractionation methods. The present study documents that IRBIT is expressed in Leydig and Sertoli cells. In addition, pronounced IRBIT expression was detected in sperm precursors during early stages of spermatogenesis as well as in spermatozoa. Analyzing tissue sections of rodent epididymides, IRBIT was found to co-localize with the proton pumping V-ATPase and the cystic fibrosis transmembrane conductance regulator (CFTR) at the apical surface of narrow and clear cells. A similar co-localization of IRBIT with CFTR was also observed for Sertoli cells and developing germ cells. Remarkably, assaying caudal sperm in immunogold electron microscopy, IRBIT was found to localize to the acrosomal cap and the flagellum as well as to the sperm nucleus; moreover, a prominent oligomerization was observed for spermatozoa. The pronounced occurrence of IRBIT in the male reproductive system and mature spermatozoa indicates a potential role for IRBIT in establishing the essential luminal environment for a faithful execution of spermatogenesis and epididymal sperm maturation, and suggest a participation of IRBIT during maturation steps after ejaculation and/or the final fertilization process.
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Affiliation(s)
- Heike Borth
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-Universit, ä, t M, ü, nchen, München, Germany
| | - Nele Weber
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-Universit, ä, t M, ü, nchen, München, Germany
| | - Dorke Meyer
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-Universit, ä, t M, ü, nchen, München, Germany
| | - Andrea Wartenberg
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-Universit, ä, t M, ü, nchen, München, Germany
| | - Elisabeth Arlt
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-Universit, ä, t M, ü, nchen, München, Germany
| | - Susanna Zierler
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-Universit, ä, t M, ü, nchen, München, Germany
| | - Andreas Breit
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-Universit, ä, t M, ü, nchen, München, Germany
| | - Gunther Wennemuth
- Department of Anatomy, University Clinic Essen, University of Duisburg-Essen, Germany
| | - Thomas Gudermann
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-Universit, ä, t M, ü, nchen, München, Germany
| | - Ingrid Boekhoff
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-Universit, ä, t M, ü, nchen, München, Germany
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Molden BM, Cooney KA, West K, Van Der Ploeg LHT, Baldini G. Temporal cAMP Signaling Selectivity by Natural and Synthetic MC4R Agonists. Mol Endocrinol 2015; 29:1619-33. [PMID: 26418335 DOI: 10.1210/me.2015-1071] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The melanocortin-4 receptor (MC4R) is a G protein-coupled receptor expressed in the brain, where it controls energy balance through pathways including α-melanocyte-stimulating hormone (α-MSH)-dependent signaling. We have reported that the MC4R can exist in an active conformation that signals constitutively by increasing cAMP levels in the absence of receptor desensitization. We asked whether synthetic MC4R agonists differ in their ability to increase intracellular cAMP over time in Neuro2A cells expressing endogenous MC4R and exogenous, epitope-tagged hemagglutinin-MC4R-green fluorescent protein. By analyzing intracellular cAMP in a temporally resolved Förster resonance energy transfer assay, we show that withdrawal of α-MSH leads to a quick reversal of cAMP induction. By contrast, the synthetic agonist melanotan II (MTII) induces a cAMP signal that persists for at least 1 hour after removal of MTII from the medium and cannot be antagonized by agouti related protein. Similarly, in mHypoE-42 immortalized hypothalamic neurons, MTII, but not α-MSH, induced persistent AMP kinase signal, which occurs downstream of increased cAMP. By using a fluorescence recovery after photobleaching assay, it appears that the receptor exposed to MTII continues to signal after being internalized. Similar to MTII, the synthetic MC4R agonists, THIQ and BIM-22511, but not LY2112688, induced prolonged cAMP signaling after agonist withdrawal. However, agonist-exposed MC4R desensitized to the same extent, regardless of the ligand used and regardless of differences in receptor intracellular retention kinetics. In conclusion, α-MSH and LY2112688, when compared with MTII, THIQ, and BIM-22511, vary in the duration of the acute cAMP response, showing distinct temporal signaling selectivity, possibly linked to specific cell compartments from which cAMP signals may originate.
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Affiliation(s)
- Brent M Molden
- Department of Biochemistry and Molecular Biology (B.M.M., K.A.C., K.W., G.B.), University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199; and Rhythm Pharmaceuticals, Inc (L.H.T.V.D.P.), Boston, Massachusetts 02116
| | - Kimberly A Cooney
- Department of Biochemistry and Molecular Biology (B.M.M., K.A.C., K.W., G.B.), University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199; and Rhythm Pharmaceuticals, Inc (L.H.T.V.D.P.), Boston, Massachusetts 02116
| | - Kirk West
- Department of Biochemistry and Molecular Biology (B.M.M., K.A.C., K.W., G.B.), University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199; and Rhythm Pharmaceuticals, Inc (L.H.T.V.D.P.), Boston, Massachusetts 02116
| | - Lex H T Van Der Ploeg
- Department of Biochemistry and Molecular Biology (B.M.M., K.A.C., K.W., G.B.), University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199; and Rhythm Pharmaceuticals, Inc (L.H.T.V.D.P.), Boston, Massachusetts 02116
| | - Giulia Baldini
- Department of Biochemistry and Molecular Biology (B.M.M., K.A.C., K.W., G.B.), University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199; and Rhythm Pharmaceuticals, Inc (L.H.T.V.D.P.), Boston, Massachusetts 02116
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Ramírez D, Saba J, Carniglia L, Durand D, Lasaga M, Caruso C. Melanocortin 4 receptor activates ERK-cFos pathway to increase brain-derived neurotrophic factor expression in rat astrocytes and hypothalamus. Mol Cell Endocrinol 2015; 411:28-37. [PMID: 25892444 DOI: 10.1016/j.mce.2015.04.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 04/09/2015] [Accepted: 04/09/2015] [Indexed: 01/08/2023]
Abstract
Melanocortins are neuropeptides with well recognized anti-inflammatory and anti-apoptotic effects in the brain. Of the five melanocortin receptors (MCR), MC4R is abundantly expressed in the brain and is the only MCR present in astrocytes. We have previously shown that MC4R activation by the α-melanocyte stimulating hormone (α-MSH) analog, NDP-MSH, increased brain-derived neurotrophic factor (BDNF) expression through the classic cAMP-Protein kinase A-cAMP responsive element binding protein pathway in rat astrocytes. Now, we examined the participation of the mitogen activated protein kinases pathway in MC4R signaling. Rat cultured astrocytes treated with NDP-MSH 1 µM for 1 h showed increased BDNF expression. Inhibition of extracellular signal-regulated kinase (ERK) and ribosomal p90 S6 kinase (RSK), an ERK substrate, but not of p38 or JNK, prevented the increase in BDNF expression induced by NDP-MSH. Activation of MC4R increased cFos expression, a target of both ERK and RSK. ERK activation by MC4R involves cAMP, phosphoinositide-3 kinase (PI3K) and the non receptor tyrosine kinase, Src. Both PI3K and Src inhibition abolished NDP-MSH-induced BDNF expression. Moreover, we found that intraperitoneal injection of α-MSH induces BDNF and MC4R expression and activates ERK and cFos in male rat hypothalamus. Our results show for the first time that MC4R-induced BDNF expression in astrocytes involves ERK-RSK-cFos pathway which is dependent on PI3K and Src, and that melanocortins induce BDNF expression and ERK-cFos activation in rat hypothalamus.
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Affiliation(s)
- D Ramírez
- INBIOMED UBA-CONICET, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - J Saba
- INBIOMED UBA-CONICET, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - L Carniglia
- INBIOMED UBA-CONICET, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - D Durand
- INBIOMED UBA-CONICET, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - M Lasaga
- INBIOMED UBA-CONICET, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - C Caruso
- INBIOMED UBA-CONICET, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina.
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Yen CY, Chiang WF, Liu SY, Lin CC, Liao KA, Lin CY, Hsieh WF, Cheng YC, Hsu KC, Lin PY, Chen TC, Lee IL, Lin MH, Liu YC. Impacts of autophagy-inducing ingredient of areca nut on tumor cells. PLoS One 2015; 10:e0128011. [PMID: 26017803 PMCID: PMC4445909 DOI: 10.1371/journal.pone.0128011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 04/21/2015] [Indexed: 12/17/2022] Open
Abstract
Areca nut (AN) is a popular carcinogen used by about 0.6-1.2 billion people worldwide. Although AN contains apoptosis-inducing ingredients, we previously demonstrated that both AN extract (ANE) and its 30-100 kDa fraction (ANE 30-100K) predominantly induce autophagic cell death in both normal and malignant cells. In this study, we further explored the action mechanism of ANE 30-100K-induced autophagy (AIA) in Jurkat T lymphocytes and carcinoma cell lines including OECM-1 (mouth), CE81T/VGH (esophagus), SCC25 (tongue), and SCC-15 (tongue). The results showed that chemical- and small hairpin RNA (shRNA)-mediated inhibition of AMP-activated protein kinase (AMPK) resulted in the attenuation of AIA in Jurkat T but not in OECM-1 cells. Knockdown of Atg5 and Beclin 1 expressions ameliorated AIA in OECM-1/CE81T/VGH/Jurkat T and OECM-1/SCC25/SCC-15, respectively. Furthermore, ANE 30-100K could activate caspase-3 after inhibition of Beclin 1 expression in OECM-1/SCC25/SCC15 cells. Meanwhile, AMPK was demonstrated to be the upstream activator of the extracellular-regulated kinase (ERK) in Jurkat T cells, and inhibition of MEK attenuated AIA in Jurkat T/OECM-1/CE81T/VGH cells. Finally, we also found that multiple myeloma RPMI8226, lymphoma U937, and SCC15 cells survived from long-term non-cytotoxic ANE 30-100K treatment exhibited stronger resistance against serum deprivation through upregulated autophagy. Collectively, our studies indicate that Beclin-1 and Atg5 but not AMPK are commonly required for AIA, and MEK/ERK pathway is involved in AIA. Meanwhile, it is also suggested that long-term AN usage might increase the resistance of survived tumor cells against serum-limited conditions.
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Affiliation(s)
- Ching-Yu Yen
- Department of Dentistry, Taipei Medical University, Taipei, Taiwan
- Department of Dentistry, National Defense Medical Center, Taipei, Taiwan
- Oral and Maxillofacial Surgery Section, Chi Mei Medical Center, Tainan, Taiwan
| | - Wei-Fan Chiang
- Oral and Maxillofacial Surgery Section, Chi Mei Hospital, Liouying, Taiwan
- School of Dentistry, National Yang-Ming University, Taipei, Taiwan
| | - Shyun-Yeu Liu
- Department of Dentistry, Taipei Medical University, Taipei, Taiwan
- Department of Dentistry, National Defense Medical Center, Taipei, Taiwan
- Oral and Maxillofacial Surgery Section, Chi Mei Medical Center, Tainan, Taiwan
| | - Chung-Chih Lin
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan
| | - Kuo-An Liao
- Oral and Maxillofacial Surgery Section, Chi Mei Hospital, Liouying, Taiwan
| | - Che-Yi Lin
- Oral and Maxillofacial Surgery Section, Chi Mei Hospital, Liouying, Taiwan
| | - Wan-Fang Hsieh
- Department of Biotechnology, Chia Nan University of Pharmacy, Tainan, Taiwan
- Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan
| | - Yon-Chi Cheng
- Department of Biotechnology, Chia Nan University of Pharmacy, Tainan, Taiwan
- Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan
| | - Kai-Cheng Hsu
- Department of Biotechnology, Chia Nan University of Pharmacy, Tainan, Taiwan
- Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan
| | - Pin-Yen Lin
- Department of Biotechnology, Chia Nan University of Pharmacy, Tainan, Taiwan
- Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan
| | - Tai-Chi Chen
- Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan
| | - I-Ling Lee
- Oral and Maxillofacial Surgery Section, Chi Mei Hospital, Liouying, Taiwan
| | - Mei-Huei Lin
- Department of Biotechnology, Chia Nan University of Pharmacy, Tainan, Taiwan
- Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan
- * E-mail: (MHL); (YCL)
| | - Young-Chau Liu
- Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan
- Division of Natural Science, College of Liberal Education, Shu-Te University, Kaohsiung, Taiwan
- * E-mail: (MHL); (YCL)
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Zhou Y, Wu S, Liang C, Lin Y, Zou Y, Li K, Lu B, Shu M, Huang Y, Zhu W, Kang Z, Xu D, Hu J, Yan G. Transcriptional upregulation of microtubule-associated protein 2 is involved in the protein kinase A-induced decrease in the invasiveness of glioma cells. Neuro Oncol 2015; 17:1578-88. [PMID: 26014048 DOI: 10.1093/neuonc/nov060] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 03/14/2015] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Malignant glioma is the most lethal primary tumor of the central nervous system, with notable cell invasion causing significant recurrence. Suppression of glioma invasion is very important for improving clinical outcomes. Drugs that directly disrupt the cytoskeleton have been developed for this purpose; however, drug resistance and unsatisfactory selectivity have limited their clinical use. Previously, we reported that protein kinase A (PKA, also known as cyclic-AMP dependent protein kinase) activation induced the differentiation of glioma cells. METHODS We used several small molecular inhibitors and RNA interference, combined with wound healing assays, Matrigel transwell assay, and microscopic observation, to determine whether activation of the PKA pathway could inhibit the invasion of human glioma cells. RESULTS Activation of PKA decreased the invasion of glioma cells. The mechanism operated via transcriptional upregulation of microtubule-associated protein 2 (MAP2), which was activated by the PKA pathway and led to ossification of microtubule dynamics via polymerization of tubulin. This resulted in morphological changes and a reduction in glioma cell invasion. Furthermore, chromosome immunoprecipitation and quantitative real-time polymerase chain reaction showed that signal transducer and activator of transcription 3 (STAT3) is involved in the transcriptional upregulation of MAP2. CONCLUSION Our findings suggested that PKA may represent a potential target for anti-invasion glioma therapy and that the downstream modulators (eg, STAT3/MAP2) partially mediate the effects of PKA.
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Affiliation(s)
- Yuxi Zhou
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Sihan Wu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Chaofeng Liang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Yuan Lin
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Yan Zou
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Kai Li
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Bingzheng Lu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Minfeng Shu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Yijun Huang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Wenbo Zhu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Zhuang Kang
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Dong Xu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Jun Hu
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
| | - Guangmei Yan
- Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (Y.Z., S.W., Y.L., K.L., B.L., M.S., Y.H., W.Z., D.X., J.H., G.Y.); Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (C.L.); Department of Imaging, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China (Y.Z., Z.K.); Department of Microbiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China (J.H.)
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Breit A, Besik V, Solinski HJ, Muehlich S, Glas E, Yarwood SJ, Gudermann T. Serine-727 phosphorylation activates hypothalamic STAT-3 independently from tyrosine-705 phosphorylation. Mol Endocrinol 2015; 29:445-59. [PMID: 25584415 DOI: 10.1210/me.2014-1300] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Transcriptional activity of signal transducer and activator of transcription-3 (STAT-3) is a key element in the central regulation of appetite and energy homeostasis. Activation of hypothalamic STAT-3 has been attributed to cytokine-promoted phosphorylation at tyrosine-705 (Tyr-705). In nonhypothalamic cells, STAT-3 is also phosphorylated at serine-727 (Ser-727), but the functional significance of Ser-727 in the regulation of hypothalamic STAT-3 is not known. We used 2 hypothalamic cell lines and analyzed the effects of various hormones on STAT-3-dependent reporter gene activity and observed that IFN-γ, epidermal growth factor (EGF), and bradykinin (BK) induce similar STAT-3 reporter activation. EGF and BK solely increased Ser-727 and IFN-γ increased Tyr-705 phosphorylation of STAT-3. Specific inhibition of ERK-1/2 activity blocked EGF- and BK-induced STAT-3 activation and Ser-727 phosphorylation. BK-induced ERK-1/2 activation occurred via EGF receptor transactivation. Consequently, the BK-mediated effects on STAT-3 were blocked by a specific EGF receptor antagonist. Next, we analyzed the effects of IFN-γ and EGF on the expression of the STAT-3-dependent genes thyroliberin-releasing hormone and suppressors of cytokine signaling-3. EGF but not IFN-γ enhanced thyroliberin-releasing hormone expression via STAT-3. With regard to suppressors of cytokine signaling-3, we observed prolonged expression induced by IFN-γ and a transient effect of EGF that required coactivation of the activator protein-1. Thus, EGF-promoted Ser-727 phosphorylation by ERK-1/2 is not only sufficient to fully activate hypothalamic STAT-3, but, in terms of targeted genes and required cofactors, entails distinct modes of STAT-3 actions compared with IFN-γ-induced Tyr-705 phosphorylation.
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Affiliation(s)
- Andreas Breit
- Walther-Straub-Institut für Pharmakologie und Toxikologie (A.B., V.B., H.J.S., S.M., E.G., T.G.), Ludwig-Maximilians-Universität München, München, Germany 80336; and The Institute of Molecular, Cell and Systems Biology (S.J.Y.), College of Medical, Veterinary and Life Science, University of Glasgow, Glasgow GC12 8QQ, United Kingdom
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Kobashigawa LC, Xu YC, Padbury JF, Tseng YT, Yano N. Metformin protects cardiomyocyte from doxorubicin induced cytotoxicity through an AMP-activated protein kinase dependent signaling pathway: an in vitro study. PLoS One 2014; 9:e104888. [PMID: 25127116 PMCID: PMC4134245 DOI: 10.1371/journal.pone.0104888] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 07/18/2014] [Indexed: 12/16/2022] Open
Abstract
Doxorubicin (Dox) is one of the most widely used antitumor drugs, but its cumulative cardiotoxicity have been major concerns in cancer therapeutic practice for decades. Recent studies established that metformin (Met), an oral anti-diabetic drug, provides protective effects in Dox-induced cardiotoxicity. Met has been shown to increase fatty acid oxidation, an effect mediated by AMP activated protein kinase (AMPK). Here we delineate the intracellular signaling factors involved in Met mediated protection against Dox-induced cardiotoxicity in the H9c2 cardiomyoblast cell line. Treatment with low dose Met (0.1 mM) increased cell viabilities and Ki-67 expressions while decreasing LDH leakages, ROS generations and [Ca2+]i. The protective effect was reversed by a co-treatment with compound-C, an AMPK specific inhibitor, or by an over expression of a dominant-negative AMPKα cDNA. Inhibition of PKA with H89 or a suppression of Src kinase by a small hairpin siRNA also abrogated the protective effect of the low dose Met. Whereas, with a higher dose of Met (1.0 mM), the protective effects were abolished regardless of the enhanced AMPK, PKA/CREB1 and Src kinase activity. In high dose Met treated cells, expression of platelet-derived growth factor receptor (PDGFR) was significantly suppressed. Furthermore, the protective effect of low dose Met was totally reversed by co-treatment with AG1296, a PDGFR specific antagonist. These data provide in vitro evidence supporting a signaling cascade by which low dose Met exerts protective effects against Dox via sequential involvement of AMPK, PKA/CREB1, Src and PDGFR. Whereas high dose Met reverses the effect by suppressing PDGFR expression.
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Affiliation(s)
- Laura C. Kobashigawa
- Department of Pediatrics, Women & Infants Hospital, The Warren Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Yan Chun Xu
- Department of Pediatrics, Women & Infants Hospital, The Warren Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - James F. Padbury
- Department of Pediatrics, Women & Infants Hospital, The Warren Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Yi-Tang Tseng
- Department of Pediatrics, Women & Infants Hospital, The Warren Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
- * E-mail: (YT); (NY)
| | - Naohiro Yano
- Department of Pediatrics, Women & Infants Hospital, The Warren Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
- * E-mail: (YT); (NY)
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LaPierre MP, Abraham MA, Filippi BM, Yue JTY, Lam TKT. Glucagon and lipid signaling in the hypothalamus. Mamm Genome 2014; 25:434-41. [DOI: 10.1007/s00335-014-9510-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 03/25/2014] [Indexed: 12/12/2022]
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Abraham MA, Yue JTY, LaPierre MP, Rutter GA, Light PE, Filippi BM, Lam TKT. Hypothalamic glucagon signals through the KATP channels to regulate glucose production. Mol Metab 2013; 3:202-8. [PMID: 24634823 DOI: 10.1016/j.molmet.2013.11.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 11/18/2013] [Accepted: 11/20/2013] [Indexed: 12/11/2022] Open
Abstract
Insulin, leptin and GLP-1 signal in the mediobasal hypothalamus (MBH) to lower hepatic glucose production (GP). MBH glucagon action also inhibits GP but the downstream signaling mediators remain largely unknown. In parallel, a lipid-sensing pathway involving MBH AMPK→malonyl-CoA→CPT-1→LCFA-CoA→PKC-δ leading to the activation of KATP channels lowers GP. Given that glucagon signals through the MBH PKA to lower GP, and PKA inhibits AMPK in hypothalamic cell lines, a possibility arises that MBH glucagon-PKA inhibits AMPK, elevates LCFA-CoA levels to activate PKC-δ, and activates KATP channels to lower GP. We here report that neither molecular or chemical activation of MBH AMPK nor inhibition of PKC-δ negated the effect of MBH glucagon. In contrast, molecular and chemical inhibition of MBH KATP channels negated MBH glucagon's effect to lower GP. Thus, MBH glucagon signals through a lipid-sensing independent but KATP channel-dependent pathway to regulate GP.
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Affiliation(s)
- Mona A Abraham
- Toronto General Research Institute, University Health Network, Toronto, Canada ; Departments of Physiology, University of Toronto, Toronto, Canada
| | - Jessica T Y Yue
- Toronto General Research Institute, University Health Network, Toronto, Canada ; Departments of Medicine, University of Toronto, Toronto, Canada
| | - Mary P LaPierre
- Toronto General Research Institute, University Health Network, Toronto, Canada ; Departments of Physiology, University of Toronto, Toronto, Canada
| | - Guy A Rutter
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College of London, South Kensington, London, UK
| | - Peter E Light
- Department of Pharmacology, University of Alberta, Edmonton, Canada
| | - Beatrice M Filippi
- Toronto General Research Institute, University Health Network, Toronto, Canada ; Departments of Medicine, University of Toronto, Toronto, Canada
| | - Tony K T Lam
- Toronto General Research Institute, University Health Network, Toronto, Canada ; Departments of Physiology, University of Toronto, Toronto, Canada ; Departments of Medicine, University of Toronto, Toronto, Canada ; Banting and Best Diabetes Centre, University of Toronto, Toronto, Canada
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Exposure of MC4R to agonist in the endoplasmic reticulum stabilizes an active conformation of the receptor that does not desensitize. Proc Natl Acad Sci U S A 2013; 110:E4733-42. [PMID: 24248383 DOI: 10.1073/pnas.1219808110] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Melanocortin-4 receptor (MC4R) is a G protein-coupled receptor expressed in neurons of the hypothalamus where it regulates food intake. MC4R responds to an agonist, α-melanocyte-stimulating hormone (α-MSH) and to an antagonist/inverse agonist, agouti-related peptide (AgRP), which are released by upstream neurons. Binding to α-MSH leads to stimulation of receptor activity and suppression of food intake, whereas AgRP has opposite effects. MC4R cycles constantly between the plasma membrane and endosomes and undergoes agonist-mediated desensitization by being routed to lysosomes. MC4R desensitization and increased AgRP expression are thought to decrease the effectiveness of MC4R agonists as an antiobesity treatment. In this study, α-MSH, instead of being delivered extracellularly, is targeted to the endoplasmic reticulum (ER) of neuronal cells and cultured hypothalamic neurons. We find that the ER-targeted agonist associates with MC4R at this location, is transported to the cell surface, induces constant cAMP and AMP kinase signaling at maximal amplitude, abolishes desensitization of the receptor, and promotes both cell-surface expression and constant signaling by an obesity-linked MC4R variant, I316S, that otherwise is retained in the ER. Formation of the MC4R/agonist complex in the ER stabilizes the receptor in an active conformation that at the cell surface is insensitive to antagonism by AgRP and at the endosomes is refractory to routing to the lysosomes. The data indicate that targeting agonists to the ER can stabilize an active conformation of a G protein-coupled receptor that does not become desensitized, suggesting a target for therapy.
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Caruso C, Carniglia L, Durand D, Scimonelli TN, Lasaga M. Astrocytes: new targets of melanocortin 4 receptor actions. J Mol Endocrinol 2013; 51:R33-50. [PMID: 23881919 DOI: 10.1530/jme-13-0064] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Astrocytes exert a wide variety of functions with paramount importance in brain physiology. After injury or infection, astrocytes become reactive and they respond by producing a variety of inflammatory mediators that help maintain brain homeostasis. Loss of astrocyte functions as well as their excessive activation can contribute to disease processes; thus, it is important to modulate reactive astrocyte response. Melanocortins are peptides with well-recognized anti-inflammatory and neuroprotective activity. Although melanocortin efficacy was shown in systemic models of inflammatory disease, mechanisms involved in their effects have not yet been fully elucidated. Central anti-inflammatory effects of melanocortins and their mechanisms are even less well known, and, in particular, the effects of melanocortins in glial cells are poorly understood. Of the five known melanocortin receptors (MCRs), only subtype 4 is present in astrocytes. MC4R has been shown to mediate melanocortin effects on energy homeostasis, reproduction, inflammation, and neuroprotection and, recently, to modulate astrocyte functions. In this review, we will describe MC4R involvement in anti-inflammatory, anorexigenic, and anti-apoptotic effects of melanocortins in the brain. We will highlight MC4R action in astrocytes and discuss their possible mechanisms of action. Melanocortin effects on astrocytes provide a new means of treating inflammation, obesity, and neurodegeneration, making them attractive targets for therapeutic interventions in the CNS.
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Affiliation(s)
- Carla Caruso
- School of Medicine, Biomedical Research Institute (UBA-CONICET), University of Buenos Aires, Paraguay 2155 piso 10, 1121ABG Buenos Aires, Argentina IFEC (CONICET) Department of Pharmacology, School of Chemistry, National University of Córdoba, Córdoba, Argentina
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Cui H, Lutter M. The expression of MC4Rs in D1R neurons regulates food intake and locomotor sensitization to cocaine. GENES BRAIN AND BEHAVIOR 2013; 12:658-65. [PMID: 23786641 DOI: 10.1111/gbb.12057] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 06/14/2013] [Indexed: 12/27/2022]
Abstract
While it is known that mice lacking melanocortin 4 receptor (MC4R) expression develop hyperphagia resulting in early-onset obesity, the specific neural circuits that mediate this process remain unclear. Here, we report that selective restoration of MC4R expression within dopamine-1 receptor-expressing neurons [MC4R/dopamine 1 receptor (D1R) mice] partially blunts the severe obesity seen in MC4R-null mice by decreasing meal size, but not meal frequency, in the dark cycle. We also report that both acute cocaine-induced anorexia and the development of locomotor sensitization to repeated administration of cocaine are blunted in MC4R-null mice and normalized in MC4R/D1R mice. Neuronal retrograde tracing identifies the lateral hypothalamic area as the primary target of MC4R-expressing neurons in the nucleus accumbens. Biochemical studies in the ventral striatum show that phosphorylation of DARPP-32(Thr) (-34) and GluR1(Ser) (-845) is diminished in MC4R-null mice after chronic cocaine administration but rescued in MC4R/D1R mice. These findings highlight a physiological role of MC4R-mediated signaling within D1R neurons in the long-term regulation of energy balance and behavioral responses to cocaine.
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Affiliation(s)
- H Cui
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
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Mo XL, Tao YX. Activation of MAPK by inverse agonists in six naturally occurring constitutively active mutant human melanocortin-4 receptors. Biochim Biophys Acta Mol Basis Dis 2013; 1832:1939-48. [PMID: 23791567 DOI: 10.1016/j.bbadis.2013.06.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 05/17/2013] [Accepted: 06/05/2013] [Indexed: 01/14/2023]
Abstract
The melanocortin-4 receptor (MC4R) is a G protein-coupled receptor that plays an essential role in regulating energy homeostasis. Defects in MC4R are the most common monogenic form of obesity, with about 170 distinct mutations identified in human. In addition to the conventional Gs-stimulated adenylyl cyclase pathway, it has been recently demonstrated that MC4R also activates mitogen-activated protein kinases, extracellular signal-regulated kinases 1 and 2 (ERK1/2). Herein, we investigated the potential of four MC4R ligands that are inverse agonists at the Gs-cAMP signaling pathway, including agouti-related peptide (AgRP), MCL0020, Ipsen 5i and ML00253764, to regulate ERK1/2 activation (pERK1/2) in wild type and six naturally occurring constitutively active mutant (CAM) MC4Rs. We showed that these four inverse agonists acted as agonists for the ERK1/2 signaling cascade in wild type and CAM MC4Rs. Three mutants (P230L, L250Q and F280L) had significantly increased pERK1/2 level upon stimulation with all four inverse agonists, with maximal induction ranging from 1.6 to 4.2-fold. D146N had significantly increased pERK1/2 level upon stimulation with AgRP, MCL0020 or ML00253764, but not Ipsen 5i. The pERK1/2 levels of H76R and S127L were significantly increased only upon stimulation with AgRP or MCL0020. In summary, our studies demonstrated for the first time that MC4R inverse agonists at the Gs-cAMP pathway could serve as agonists in the MAPK pathway. These results suggested that there were multiple activation states of MC4R with ligand-specific and/or mutant-specific conformations capable of differentially coupling the MC4R to distinct signaling pathways.
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Affiliation(s)
- Xiu-Lei Mo
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA
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