1
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Neuhaus M, Fryklund C, Taylor H, Borreguero-Muñoz A, Kopietz F, Ardalani H, Rogova O, Stirrat L, Bremner SK, Spégel P, Bryant NJ, Gould GW, Stenkula KG. EHD2 regulates plasma membrane integrity and downstream insulin receptor signaling events. Mol Biol Cell 2023; 34:ar124. [PMID: 37703099 PMCID: PMC10846623 DOI: 10.1091/mbc.e23-03-0078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 09/07/2023] [Accepted: 09/08/2023] [Indexed: 09/14/2023] Open
Abstract
Adipocyte dysfunction is a crucial driver of insulin resistance and type 2 diabetes. We identified EH domain-containing protein 2 (EHD2) as one of the most highly upregulated genes at the early stage of adipose-tissue expansion. EHD2 is a dynamin-related ATPase influencing several cellular processes, including membrane recycling, caveolae dynamics, and lipid metabolism. Here, we investigated the role of EHD2 in adipocyte insulin signaling and glucose transport. Using C57BL6/N EHD2 knockout mice under short-term high-fat diet conditions and 3T3-L1 adipocytes we demonstrate that EHD2 deficiency is associated with deterioration of insulin signal transduction and impaired insulin-stimulated GLUT4 translocation. Furthermore, we show that lack of EHD2 is linked with altered plasma membrane lipid and protein composition, reduced insulin receptor expression, and diminished insulin-dependent SNARE protein complex formation. In conclusion, these data highlight the importance of EHD2 for the integrity of the plasma membrane milieu, insulin receptor stability, and downstream insulin receptor signaling events, involved in glucose uptake and ultimately underscore its role in insulin resistance and obesity.
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Affiliation(s)
- Mathis Neuhaus
- Department of Experimental Medical Science, Lund University, 22184 Lund, Sweden
| | - Claes Fryklund
- Department of Experimental Medical Science, Lund University, 22184 Lund, Sweden
| | - Holly Taylor
- Strathclyde Institute for Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, UK
| | | | - Franziska Kopietz
- Department of Experimental Medical Science, Lund University, 22184 Lund, Sweden
| | - Hamidreza Ardalani
- Department of Chemistry, Centre for Analysis and Synthesis, Lund University, 22241 Lund, Sweden
| | - Oksana Rogova
- Department of Chemistry, Centre for Analysis and Synthesis, Lund University, 22241 Lund, Sweden
| | - Laura Stirrat
- Strathclyde Institute for Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, UK
| | - Shaun K. Bremner
- Strathclyde Institute for Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, UK
| | - Peter Spégel
- Department of Chemistry, Centre for Analysis and Synthesis, Lund University, 22241 Lund, Sweden
| | - Nia J. Bryant
- Department of Biology and York Biomedical Research Institute, University of York, York YO10 5DD, UK
| | - Gwyn W. Gould
- Strathclyde Institute for Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, UK
| | - Karin G. Stenkula
- Department of Experimental Medical Science, Lund University, 22184 Lund, Sweden
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2
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The insulin receptor endocytosis. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2023; 194:79-107. [PMID: 36631202 DOI: 10.1016/bs.pmbts.2022.06.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Insulin signaling controls multiple aspects of animal physiology. At the cell surface, insulin binds and activates the insulin receptor (IR), a receptor tyrosine kinase. Insulin promotes a large conformational change of IR and stabilizes the active conformation. The insulin-activated IR triggers signaling cascades, thus controlling metabolism, growth, and proliferation. The activated IR undergoes internalization by clathrin- or caveolae-mediated endocytosis. The IR endocytosis plays important roles in insulin clearance from blood, and distribution and termination of the insulin signaling. Despite decades of extensive studies, the mechanism and regulation of IR endocytosis and its contribution to pathophysiology remain incompletely understood. Here we discuss recent findings that provide insights into the molecular mechanisms and regulatory pathways that mediate the IR endocytosis.
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3
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Li Q, Spalding KL. The regulation of adipocyte growth in white adipose tissue. Front Cell Dev Biol 2022; 10:1003219. [PMID: 36483678 PMCID: PMC9723158 DOI: 10.3389/fcell.2022.1003219] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 11/03/2022] [Indexed: 10/25/2023] Open
Abstract
Adipocytes can increase in volume up to a thousand-fold, storing excess calories as triacylglycerol in large lipid droplets. The dramatic morphological changes required of adipocytes demands extensive cytoskeletal remodeling, including lipid droplet and plasma membrane expansion. Cell growth-related signalling pathways are activated, stimulating the production of sufficient amino acids, functional lipids and nucleotides to meet the increasing cellular needs of lipid storage, metabolic activity and adipokine secretion. Continued expansion gives rise to enlarged (hypertrophic) adipocytes. This can result in a failure to maintain growth-related homeostasis and an inability to cope with excess nutrition or respond to stimuli efficiently, ultimately leading to metabolic dysfunction. We summarize recent studies which investigate the functional and cellular structure remodeling of hypertrophic adipocytes. How adipocytes adapt to an enlarged cell size and how this relates to cellular dysfunction are discussed. Understanding the healthy and pathological processes involved in adipocyte hypertrophy may shed light on new strategies for promoting healthy adipose tissue expansion.
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Affiliation(s)
- Qian Li
- Department of Anatomy, Histology and Embryology, School of Basic Medical Sciences, Department of General Surgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Kirsty L. Spalding
- Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
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4
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Xia W, Li X, Wu Q, Xu A, Zhang L, Xia Z. The importance of caveolin as a target in the prevention and treatment of diabetic cardiomyopathy. Front Immunol 2022; 13:951381. [PMID: 36405687 PMCID: PMC9666770 DOI: 10.3389/fimmu.2022.951381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 10/21/2022] [Indexed: 08/30/2023] Open
Abstract
The diabetic population has been increasing in the past decades and diabetic cardiomyopathy (DCM), a pathology that is defined by the presence of cardiac remodeling and dysfunction without conventional cardiac risk factors such as hypertension and coronary heart diseases, would eventually lead to fatal heart failure in the absence of effective treatment. Impaired insulin signaling, commonly known as insulin resistance, plays an important role in the development of DCM. A family of integral membrane proteins named caveolins (mainly caveolin-1 and caveolin-3 in the myocardium) and a protein hormone adiponectin (APN) have all been shown to be important for maintaining normal insulin signaling. Abnormalities in caveolins and APN have respectively been demonstrated to cause DCM. This review aims to summarize recent research findings of the roles and mechanisms of caveolins and APN in the development of DCM, and also explore the possible interplay between caveolins and APN.
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Affiliation(s)
- Weiyi Xia
- Department of Anesthesiology, Affiliated Hospital of Guangdong Medical University, Guangdong, China
- Department of Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Xia Li
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Qingping Wu
- Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Aimin Xu
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Medicine, The University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Liangqing Zhang
- Department of Anesthesiology, Affiliated Hospital of Guangdong Medical University, Guangdong, China
| | - Zhengyuan Xia
- Department of Anesthesiology, Affiliated Hospital of Guangdong Medical University, Guangdong, China
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Medicine, The University of Hong Kong, Hong Kong, Hong Kong SAR, China
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5
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Suresh P, Miller WT, London E. Phospholipid exchange shows insulin receptor activity is supported by both the propensity to form wide bilayers and ordered raft domains. J Biol Chem 2021; 297:101010. [PMID: 34324831 PMCID: PMC8379460 DOI: 10.1016/j.jbc.2021.101010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 07/21/2021] [Accepted: 07/23/2021] [Indexed: 11/29/2022] Open
Abstract
Insulin receptor (IR) is a membrane tyrosine kinase that mediates the response of cells to insulin. IR activity has been shown to be modulated by changes in plasma membrane lipid composition, but the properties and structural determinants of lipids mediating IR activity are poorly understood. Here, using efficient methyl-alpha-cyclodextrin mediated lipid exchange, we studied the effect of altering plasma membrane outer leaflet phospholipid composition upon the activity of IR in mammalian cells. After substitution of endogenous lipids with lipids having an ability to form liquid ordered (Lo) domains (sphingomyelins) or liquid disordered (Ld) domains (unsaturated phosphatidylcholines (PCs)), we found that the propensity of lipids to form ordered domains is required for high IR activity. Additional substitution experiments using a series of saturated PCs showed that IR activity increased substantially with increasing acyl chain length, which increases both bilayer width and the propensity to form ordered domains. Incorporating purified IR into alkyl maltoside micelles with increasing hydrocarbon lengths also increased IR activity, but more modestly than by increasing lipid acyl chain length in cells. These results suggest that the ability to form Lo domains as well as wide bilayer width contributes to increased IR activity. Inhibition of phosphatases showed that some of the lipid dependence of IR activity upon lipid structure reflected protection from phosphatases by lipids that support Lo domain formation. These results are consistent with a model in which a combination of bilayer width and ordered domain formation modulates IR activity via IR conformation and accessibility to phosphatases.
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Affiliation(s)
- Pavana Suresh
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA
| | - W Todd Miller
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA; Department of Veterans Affairs Medical Center, Northport, New York, USA
| | - Erwin London
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA.
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6
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Morén B, Hansson B, Negoita F, Fryklund C, Lundmark R, Göransson O, Stenkula KG. EHD2 regulates adipocyte function and is enriched at cell surface-associated lipid droplets in primary human adipocytes. Mol Biol Cell 2019; 30:1147-1159. [PMID: 30811273 PMCID: PMC6724522 DOI: 10.1091/mbc.e18-10-0680] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Adipocytes play a central role in energy balance, and dysfunctional adipose tissue severely affects systemic energy homeostasis. The ATPase EH domain–containing 2 (EHD2) has previously been shown to regulate caveolae, plasma membrane-specific domains that are involved in lipid uptake and signal transduction. Here, we investigated the role of EHD2 in adipocyte function. We demonstrate that EHD2 protein expression is highly up-regulated at the onset of triglyceride accumulation during adipocyte differentiation. Small interfering RNA–mediated EHD2 silencing affected the differentiation process and impaired insulin sensitivity, lipid storage capacity, and lipolysis. Fluorescence imaging revealed localization of EHD2 to caveolae, close to cell surface–associated lipid droplets in primary human adipocytes. These lipid droplets stained positive for glycerol transporter aquaporin 7 and phosphorylated perilipin-1 following adrenergic stimulation. Further, EHD2 overexpression in human adipocytes increased the lipolytic signaling and suppressed the activity of transcription factor PPARγ. Overall, these data suggest that EHD2 plays a key role for adipocyte function.
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Affiliation(s)
- Björn Morén
- Department of Experimental Medical Science, Lund University, 223 84 Lund, Sweden
| | - Björn Hansson
- Department of Experimental Medical Science, Lund University, 223 84 Lund, Sweden
| | - Florentina Negoita
- Department of Experimental Medical Science, Lund University, 223 84 Lund, Sweden
| | - Claes Fryklund
- Department of Experimental Medical Science, Lund University, 223 84 Lund, Sweden
| | - Richard Lundmark
- Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden
| | - Olga Göransson
- Department of Experimental Medical Science, Lund University, 223 84 Lund, Sweden
| | - Karin G Stenkula
- Department of Experimental Medical Science, Lund University, 223 84 Lund, Sweden
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7
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Mariniello K, Min Y, Ghebremeskel K. Phosphorylation of protein kinase B, the key enzyme in insulin-signaling cascade, is enhanced in linoleic and arachidonic acid–treated HT29 and HepG2 cells. Nutrition 2019; 57:52-58. [DOI: 10.1016/j.nut.2018.05.033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 05/24/2018] [Accepted: 05/29/2018] [Indexed: 11/30/2022]
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8
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Trávez A, Rabanal-Ruiz Y, López-Alcalá J, Molero-Murillo L, Díaz-Ruiz A, Guzmán-Ruiz R, Catalán V, Rodríguez A, Frühbeck G, Tinahones FJ, Gasman S, Vitale N, Jiménez-Gómez Y, Malagón MM. The caveolae-associated coiled-coil protein, NECC2, regulates insulin signalling in Adipocytes. J Cell Mol Med 2018; 22:5648-5661. [PMID: 30160359 PMCID: PMC6201366 DOI: 10.1111/jcmm.13840] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Revised: 07/10/2018] [Accepted: 07/13/2018] [Indexed: 02/06/2023] Open
Abstract
Adipocyte dysfunction in obesity is commonly associated with impaired insulin signalling in adipocytes and insulin resistance. Insulin signalling has been associated with caveolae, which are coated by large complexes of caveolin and cavin proteins, along with proteins with membrane-binding and remodelling properties. Here, we analysed the regulation and function of a component of caveolae involved in growth factor signalling in neuroendocrine cells, neuroendocrine long coiled-coil protein-2 (NECC2), in adipocytes. Studies in 3T3-L1 cells showed that NECC2 expression increased during adipogenesis. Furthermore, NECC2 co-immunoprecipitated with caveolin-1 (CAV1) and exhibited a distribution pattern similar to that of the components of adipocyte caveolae, CAV1, Cavin1, the insulin receptor and cortical actin. Interestingly, NECC2 overexpression enhanced insulin-activated Akt phosphorylation, whereas NECC2 downregulation impaired insulin-induced phosphorylation of Akt and ERK2. Finally, an up-regulation of NECC2 in subcutaneous and omental adipose tissue was found in association with human obesity and insulin resistance. This effect was also observed in 3T3-L1 adipocytes exposed to hyperglycaemia/hyperinsulinemia. Overall, the present study identifies NECC2 as a component of adipocyte caveolae that is regulated in response to obesity and associated metabolic complications, and supports the contribution of this protein as a molecular scaffold modulating insulin signal transduction at these membrane microdomains.
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Affiliation(s)
- Andrés Trávez
- Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Córdoba, Spain.,Department of Cell Biology, Physiology, and Immunology, University of Córdoba, Córdoba, Spain.,Reina Sofía University Hospital, Córdoba, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Madrid, Spain
| | - Yoana Rabanal-Ruiz
- Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Córdoba, Spain.,Department of Cell Biology, Physiology, and Immunology, University of Córdoba, Córdoba, Spain.,Reina Sofía University Hospital, Córdoba, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Madrid, Spain
| | - Jaime López-Alcalá
- Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Córdoba, Spain.,Department of Cell Biology, Physiology, and Immunology, University of Córdoba, Córdoba, Spain.,Reina Sofía University Hospital, Córdoba, Spain
| | - Laura Molero-Murillo
- Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Córdoba, Spain.,Department of Cell Biology, Physiology, and Immunology, University of Córdoba, Córdoba, Spain.,Reina Sofía University Hospital, Córdoba, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Madrid, Spain
| | - Alberto Díaz-Ruiz
- Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Córdoba, Spain.,Department of Cell Biology, Physiology, and Immunology, University of Córdoba, Córdoba, Spain.,Reina Sofía University Hospital, Córdoba, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Madrid, Spain
| | - Rocío Guzmán-Ruiz
- Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Córdoba, Spain.,Department of Cell Biology, Physiology, and Immunology, University of Córdoba, Córdoba, Spain.,Reina Sofía University Hospital, Córdoba, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Madrid, Spain
| | - Victoria Catalán
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Madrid, Spain.,Metabolic Research Laboratory, Department of Endocrinology & Nutrition, Clínica Universidad de Navarra, IdiSNA, Pamplona, Spain
| | - Amaia Rodríguez
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Madrid, Spain.,Metabolic Research Laboratory, Department of Endocrinology & Nutrition, Clínica Universidad de Navarra, IdiSNA, Pamplona, Spain
| | - Gema Frühbeck
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Madrid, Spain.,Metabolic Research Laboratory, Department of Endocrinology & Nutrition, Clínica Universidad de Navarra, IdiSNA, Pamplona, Spain
| | - Francisco J Tinahones
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Madrid, Spain.,Unidad de Gestion Clínica de Endocrinología y Nutrición, Laboratorio del Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Universitario de Málaga (Virgen de la Victoria), Universidad de Málaga, Málaga, Spain
| | - Stéphane Gasman
- Institut des Neurosciences Cellulaires et Intégratives (INCI), Centre National de la Recherche Scientifique (CNRS UPR 3212), Université de Strasbourg, Strasbourg, France
| | - Nicolas Vitale
- Institut des Neurosciences Cellulaires et Intégratives (INCI), Centre National de la Recherche Scientifique (CNRS UPR 3212), Université de Strasbourg, Strasbourg, France
| | - Yolanda Jiménez-Gómez
- Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Córdoba, Spain.,Department of Cell Biology, Physiology, and Immunology, University of Córdoba, Córdoba, Spain.,Reina Sofía University Hospital, Córdoba, Spain
| | - María M Malagón
- Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Córdoba, Spain.,Department of Cell Biology, Physiology, and Immunology, University of Córdoba, Córdoba, Spain.,Reina Sofía University Hospital, Córdoba, Spain.,CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, Madrid, Spain
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9
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Li F, Han H, Lei Q, Gao J, Liu J, Liu W, Zhou Y, Li H, Cao D. Genome-wide association study of body weight in Wenshang Barred chicken based on the SLAF-seq technology. J Appl Genet 2018; 59:305-312. [PMID: 29946990 DOI: 10.1007/s13353-018-0452-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 06/13/2018] [Accepted: 06/19/2018] [Indexed: 12/19/2022]
Abstract
Chicken body weight (BW) is an economically important trait, and many studies have been conducted on genetic selection for BW. However, previous studies have detected functional chromosome mutations or regions using gene chips. The present study used the specific-locus amplified fragment sequencing (SLAF-seq) technology to perform a genome-wide association study (GWAS) on purebred Wengshang Barred chicken. A total of 1,286,715 single-nucleotide polymorphisms (SNPs) were detected, and 175,211 SNPs were selected as candidate SNPs for genome-wide association analysis using TASSEL general linear models. Six SNP markers reached genome-wide significance. Of these, rs732048524, rs735522839, rs738991545, and rs15837818 were significantly associated with body weight at 28 days (BW28), while rs314086457 and rs315694878 were significantly associated with BW120. These SNPs are close to seven genes (PRSS23, ME3, FAM181B, NABP1, SDPR, TSSK6L2, and RBBP8). Moreover, 24 BW-associated SNPs reached "suggestive" genome-wide significance. Of these, 6, 13, 1, and 4 SNPs were associated with BW28, BW56, BW80, and BW120, respectively. These results would enrich the studies on BW and promote the use of Chinese chicken, especially the Wenshang Barred chicken.
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Affiliation(s)
- Fuwei Li
- Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan, 250023, People's Republic of China.,Poultry Breeding Engineering Technology Center of Shandong Province, Jinan, 250023, Shandong, China
| | - Haixia Han
- Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan, 250023, People's Republic of China.,Poultry Breeding Engineering Technology Center of Shandong Province, Jinan, 250023, Shandong, China
| | - Qiuxia Lei
- Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan, 250023, People's Republic of China.,Poultry Breeding Engineering Technology Center of Shandong Province, Jinan, 250023, Shandong, China
| | - Jinbo Gao
- Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan, 250023, People's Republic of China.,Poultry Breeding Engineering Technology Center of Shandong Province, Jinan, 250023, Shandong, China
| | - Jie Liu
- Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan, 250023, People's Republic of China.,Poultry Breeding Engineering Technology Center of Shandong Province, Jinan, 250023, Shandong, China
| | - Wei Liu
- Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan, 250023, People's Republic of China.,Poultry Breeding Engineering Technology Center of Shandong Province, Jinan, 250023, Shandong, China
| | - Yan Zhou
- Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan, 250023, People's Republic of China.,Poultry Breeding Engineering Technology Center of Shandong Province, Jinan, 250023, Shandong, China
| | - Huimin Li
- Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan, 250023, People's Republic of China.,Poultry Breeding Engineering Technology Center of Shandong Province, Jinan, 250023, Shandong, China
| | - Dingguo Cao
- Poultry Institute, Shandong Academy of Agricultural Sciences, Jinan, 250023, People's Republic of China. .,Poultry Breeding Engineering Technology Center of Shandong Province, Jinan, 250023, Shandong, China.
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10
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Mora-García G, Gómez-Camargo D, Alario Á, Gómez-Alegría C. A Common Variation in the Caveolin 1 Gene Is Associated with High Serum Triglycerides and Metabolic Syndrome in an Admixed Latin American Population. Metab Syndr Relat Disord 2018; 16:453-463. [PMID: 29762069 PMCID: PMC6211369 DOI: 10.1089/met.2018.0004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Background: The caveolin 1 (CAV1) gene has been associated with metabolic traits in animal models and human cohorts. Recently, a prevalent variant in CAV1 has been found to be related to metabolic syndrome in Hispanics living in North America. Since Hispanics represent an admixed population at high risk for cardiovascular diseases, in this study a Latin American population with a similar genetic background was assessed. Objective: To analyze a genetic association between CAV1 and metabolic traits in an admixed Latin American population. Methods: A cross-sectional study was carried out with adults from the Colombian Caribbean Coast, selected in urban clusters and work places through a stratified sampling to include diverse ages and socioeconomic groups. Blood pressure and waist circumference were registered. Serum concentrations of glucose, triglycerides, and high-density lipoprotein cholesterol were measured from an 8-hr fasting whole-blood sample. Two previously analyzed CAV1 single nucleotide polymorphisms were genotyped (rs926198 and rs11773845). A logistic regression model was applied to estimate the associations. An admixture adjustment was performed through a Bayesian model. Results: A total of 605 subjects were included. rs11773845 was associated with hypertriglyceridemia [odds ratio (OR) = 1.33, p = 0.001] and the metabolic syndrome (OR = 1.53, p = 0.02). When admixture adjustment was performed these genetic associations preserved their statistical significance. There were no significant associations between rs926198 and metabolic traits. Conclusions: The CAV1 variation rs11773845 was found to be consistently associated with high serum triglycerides and the metabolic syndrome. This is the first report of a relationship between CAV1 variants and serum triglycerides in Latin America.
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Affiliation(s)
- Gustavo Mora-García
- 1 Grupo UNIMOL, Facultad de Medicina, Universidad de Cartagena , Cartagena de Indias, Colombia
| | - Doris Gómez-Camargo
- 1 Grupo UNIMOL, Facultad de Medicina, Universidad de Cartagena , Cartagena de Indias, Colombia
| | - Ángelo Alario
- 2 Departamento Médico, Facultad de Medicina, Universidad de Cartagena , Cartagena de Indias, Colombia
| | - Claudio Gómez-Alegría
- 3 Grupo de Investigación UNIMOL, Departamento de Farmacia, Facultad de Ciencias, Universidad Nacional de Colombia , Bogotá, Colombia
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11
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Animal models and natural products to investigate in vivo and in vitro antidiabetic activity. Biomed Pharmacother 2018; 101:833-841. [DOI: 10.1016/j.biopha.2018.02.137] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2017] [Revised: 02/26/2018] [Accepted: 02/26/2018] [Indexed: 11/17/2022] Open
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12
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Haczeyni F, Bell-Anderson KS, Farrell GC. Causes and mechanisms of adipocyte enlargement and adipose expansion. Obes Rev 2018; 19:406-420. [PMID: 29243339 DOI: 10.1111/obr.12646] [Citation(s) in RCA: 120] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 09/28/2017] [Accepted: 10/23/2017] [Indexed: 02/06/2023]
Abstract
Adipose tissue plays a significant role in whole body energy homeostasis. Obesity-associated diabetes, fatty liver and metabolic syndrome are closely linked to adipose stress and dysfunction. Genetic predisposition, overeating and physical inactivity influence the expansion of adipose tissues. Under conditions of constant energy surplus, adipocytes become hypertrophic and adipose tissues undergo hyperplasia so as to increase their lipid storage capacity, thereby keeping circulating blood glucose and fatty acids below toxic levels. Nonetheless, adipocytes have a saturation point where they lose capacity to store more lipids. At this stage, when adipocytes are fully lipid-engorged, they express stress signals. Adipose depots (particularly visceral compartments) from obese individuals with a severe metabolic phenotype are characterized by the high proportion of hypertrophic adipocytes. This review focuses on the mechanisms of adipocyte enlargement in relation to adipose fatty acid and cholesterol metabolism, and considers how this may be related to adipose dysfunction.
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Affiliation(s)
- F Haczeyni
- Liver Research Group, Australian National University Medical School at The Canberra Hospital, Canberra, ACT, Australia
| | - K S Bell-Anderson
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia
| | - G C Farrell
- Liver Research Group, Australian National University Medical School at The Canberra Hospital, Canberra, ACT, Australia
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Mora-Garcia GJ, Ruiz-Diaz MS, Gomez-Camargo DE, Gomez-Alegria CJ. Frequency of common polymorphisms in Caveolin 1 ( CAV1 ) gene in adults with high serum triglycerides from Colombian Caribbean Coast. COLOMBIA MEDICA (CALI, COLOMBIA) 2017; 48:167-173. [PMID: 29662258 PMCID: PMC5896723 DOI: 10.25100/cm.v48i4.2625] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Background Caveolin 1 gene (CAV1) has been associated with insulin resistance, metabolic syndrome and hypertension in humans. Also, it has been related to high serum triglycerides in rodents, however there is little evidence of this relation in humans. Aim To describe frequencies of common variations in CAV1 in adults with high serum triglycerides. Methods A case-control study was carried out with adults from Colombian Caribbean Coast. A whole blood sample was employed to measure serum concentrations of triglycerides, glucose, total cholesterol and HDLc. Six common Single Nucleotide Polymorphism (SNP) in CAV1 were genotyped (rs926198, rs3779512, rs10270569, rs11773845, rs7804372 and rs1049337). Allelic and genotypic frequencies were determined by direct count and Hardy-Weinberg Equilibrium (HWE) was assessed. Case and control groups were compared with null-hypothesis tests. Results A total of 220 cases and 220 controls were included. For rs3779512 an excess in homozygotes frequency was found within case group (40.4% (GG), 41.3% (GT) and 18.1% (TT); Fis=0.13, p=0.03). Another homozygotes excess among case group was found in rs7804372 (59.5% (TT), 32.3% (TA) and 8.2% (AA); Fis= 0.12, p= 0.04). In rs1049337, cases also showed an excess in homozygotes frequency (52.7% (CC), 35.0% (CT) and 12.3% (TT); Fis= 0.16, p= 0.01). Finally, for rs1049337 there were differences in genotype distribution between case and control groups (p <0.05). Conclusion An increased frequency of homozygote genotypes was found in subjects with high serum triglycerides. These findings suggest that minor alleles for SNPs rs3779512, rs7804372 and rs1049337 might be associated to higher risk of hypertriglyceridemia.
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Affiliation(s)
- Gustavo Jose Mora-Garcia
- Doctorado en Medicina Tropical, Facultad de Medicina, Universidad de Cartagena,Cartagena de Indias, Colombia
| | - Maria Stephany Ruiz-Diaz
- Doctorado en Medicina Tropical, Facultad de Medicina, Universidad de Cartagena,Cartagena de Indias, Colombia
| | - Doris Esther Gomez-Camargo
- Doctorado en Medicina Tropical, Facultad de Medicina, Universidad de Cartagena,Cartagena de Indias, Colombia
| | - Claudio Jaime Gomez-Alegria
- Grupo de Investigación UNIMOL . Departamento de Farmacia, Facultad de Ciencias, Universidad Nacional de Colombia. Bogotá, Colombia
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Rosiglitazone drives cavin-2/SDPR expression in adipocytes in a CEBPα-dependent manner. PLoS One 2017; 12:e0173412. [PMID: 28278164 PMCID: PMC5344386 DOI: 10.1371/journal.pone.0173412] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 02/10/2017] [Indexed: 12/26/2022] Open
Abstract
Caveolae are abundant adipocyte surface domains involved in insulin signaling, membrane trafficking and lipid homeostasis. Transcriptional control mechanisms for caveolins and cavins, the building blocks of caveolae, are thus arguably important for adipocyte biology and studies in this area may give insight into insulin resistance and diabetes. Here we addressed the hypothesis that one of the less characterized caveolar components, cavin-2 (SDPR), is controlled by CCAAT/Enhancer Binding Protein (CEBPα) and Peroxisome Proliferator-Activated Receptor Gamma (PPARG). Using human mRNA expression data we found that SDPR correlated with PPARG in several tissues. This was also observed during differentiation of 3T3-L1 fibroblasts into adipocytes. Treatment of 3T3-L1-derived adipocytes with the PPARγ-activator Rosiglitazone increased SDPR and CEBPα expression at both the mRNA and protein levels. Silencing of CEBPα antagonized these effects. Further, adenoviral expression of PPARγ/CEBPα or Rosiglitazone-treatment increased SDPR expression in primary rat adipocytes. The myocardin family coactivator MKL1 was recently shown to regulate SDPR expression in human coronary artery smooth muscle cells. However, we found that actin depolymerization, known to inhibit MKL1 and MKL2, was without effect on SDPR mRNA levels in adipocytes, even though overexpression of MKL1 and MKL2 had the capacity to increase caveolins and cavins and to repress PPARγ/CEBPα. Altogether, this work demonstrates that CEBPα expression and PPARγ-activity promote SDPR transcription and further supports the emerging notion that PPARγ/CEBPα and MKL1/MKL2 are antagonistic in adipocytes.
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Hofvander J, Arbajian E, Stenkula KG, Lindkvist-Petersson K, Larsson M, Nilsson J, Magnusson L, von Steyern FV, Rissler P, Hornick JL, Mertens F. Frequent low-level mutations of protein kinase D2 in angiolipoma. J Pathol 2017; 241:578-582. [PMID: 28139834 DOI: 10.1002/path.4865] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 12/05/2016] [Accepted: 12/19/2016] [Indexed: 12/13/2022]
Abstract
Tumours displaying differentiation towards normal fat constitute the most common subgroup of soft tissue neoplasms. A series of such tumours was investigated by whole-exome sequencing followed by targeted ultra-deep sequencing. Eighty per cent of angiolipomas, but not any other tumour type, displayed mutations in the protein kinase D2 (PRKD2) gene, typically in the part encoding the catalytic domain. The absence of other aberrations at the chromosome or RNA level suggests that PRKD2 mutations are critical for angiolipoma development. Consistently, the mutated PRKD2 alleles were present at low (3-15%) frequencies, indicating that only a subset of the tumour cells is affected. Indeed, by sequencing mature fat cells and other cells separately, the former typically showed the highest mutation frequencies. Thus, we hypothesize that altered PRKD2 signalling in the adipocytic cells drives tumourigenesis and, in agreement with its pivotal role in angiogenesis, induces the vessel formation that is characteristic for angiolipoma. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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Affiliation(s)
- Jakob Hofvander
- Division of Clinical Genetics, Department of Laboratory Medicine, Lund University, 221 84, Lund, Sweden
| | - Elsa Arbajian
- Division of Clinical Genetics, Department of Laboratory Medicine, Lund University, 221 84, Lund, Sweden
| | - Karin G Stenkula
- Department of Experimental Medical Science, Lund University, 221 84, Lund, Sweden
| | | | - Malin Larsson
- Science for Life Laboratory, Department of Physics, Chemistry and Biology, Linköping University, 581 83, Linköping, Sweden
| | - Jenny Nilsson
- Division of Clinical Genetics, Department of Laboratory Medicine, Lund University, 221 84, Lund, Sweden
| | - Linda Magnusson
- Division of Clinical Genetics, Department of Laboratory Medicine, Lund University, 221 84, Lund, Sweden
| | - Fredrik Vult von Steyern
- Department of Orthopedics, Clinical Sciences, Lund University and Skåne University Hospital, 221 85, Lund, Sweden
| | - Pehr Rissler
- Department of Pathology, Office for Medical Services, Division of Laboratory Medicine, 221 85, Lund, Sweden
| | - Jason L Hornick
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Fredrik Mertens
- Division of Clinical Genetics, Department of Laboratory Medicine, Lund University, 221 84, Lund, Sweden.,Department of Clinical Genetics, Office for Medical Services, Division of Laboratory Medicine, 221 85, Lund, Sweden
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Scaffolding protein IQGAP1: an insulin-dependent link between caveolae and the cytoskeleton in primary human adipocytes? Biochem J 2016; 473:3177-88. [PMID: 27458251 DOI: 10.1042/bcj20160581] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 07/25/2016] [Indexed: 12/15/2022]
Abstract
The ubiquitously expressed IQ motif-containing GTPase activating protein-1 (IQGAP1) is a scaffolding protein implicated in an array of cellular functions, in particular by binding to cytoskeletal elements and signaling proteins. A role of IQGAP1 in adipocytes has not been reported. We therefore investigated the cellular IQGAP1 interactome in primary human adipocytes. Immunoprecipitation and quantitative mass spectrometry identified caveolae and caveolae-associated proteins as the major IQGAP1 interactors alongside cytoskeletal proteins. We confirmed co-localization of IQGAP1 with the defining caveolar marker protein caveolin-1 by confocal microscopy and proximity ligation assay. Most interestingly, insulin enhanced the number of IQGAP1 interactions with caveolin-1 by five-fold. Moreover, we found a significantly reduced abundance of IQGAP1 in adipocytes from patients with type 2 diabetes compared with cells from nondiabetic control subjects. Both the abundance of IQGAP1 protein and mRNA were reduced, indicating a transcriptional defect in diabetes. Our findings suggest a novel role of IQGAP1 in insulin-regulated interaction between caveolae and cytoskeletal elements of the adipocyte, and that this is quelled in the diabetic state.
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High glucose-induced fibronectin upregulation in cultured mesangial cells involves caveolin-1-dependent RhoA-GTP activation via Src kinase. Mol Med Rep 2016; 14:963-8. [PMID: 27220778 DOI: 10.3892/mmr.2016.5312] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 03/21/2016] [Indexed: 11/05/2022] Open
Abstract
Increasing evidence indicates that diabetes-mediated renal interstitial fibrosis through extracellular matrix (ECM) protein accumulation is an important event in the development of diabetic kidney disease (DKD), however, the underlying mechanism remains unclear. In the current study, it was observed that high levels of glucose (HG) time‑ and dose-dependently increased the production of the ECM protein, fibronectin (FN), in primary rat mesangial cells. Inhibition of the Rho pathway blocked HG‑induced FN upregulation. HG‑induced RhoA activation was prevented by inhibiting caveolae with filipin III or caveolin‑1 siRNA and rescued by exogenous caveolin‑1. HG also increased caveolin-1/Src association and activated Src kinase, whereas the inhibition of Src blocked RhoA activation and FN upregulation. Src-mediated phosphorylation of caveolin‑1 on Y14 has also been implicated in signaling responses. Overexpression of the nonphosphorylatable caveolin‑1 Y14A mutant prevented the HG‑induced RhoA activation and FN upregulation. In conclusion, HG‑induced FN upregulation requires caveolae and caveolin‑1 to interact with RhoA and Src kinases. Interference with Src/caveolin-1/RhoA signaling may provide novel mechanistic targets for the treatment of DKD.
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Charming neighborhoods on the cell surface: plasma membrane microdomains regulate receptor tyrosine kinase signaling. Cell Signal 2015; 27:1963-76. [PMID: 26163824 DOI: 10.1016/j.cellsig.2015.07.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 07/07/2015] [Indexed: 12/14/2022]
Abstract
Receptor tyrosine kinases (RTK) are an important family of growth factor and hormone receptors that regulate many aspects of cellular physiology. Ligand binding by RTKs at the plasma membrane elicits activation of many signaling intermediates. The spatial and temporal regulation of RTK signaling within cells is an important determinant of receptor signaling outcome. In particular, the compartmentalization of the plasma membrane into a number of microdomains allows context-specific control of RTK signaling. Indeed various RTKs are recruited to and enriched within specific plasma membrane microdomains under various conditions, including lipid-ordered domains such as caveolae and lipid rafts, clathrin-coated structures, tetraspanin-enriched microdomains, and actin-dependent protrusive membrane microdomains such as dorsal ruffles and invadosomes. We examine the evidence for control of RTK signaling by each of these plasma membrane microdomains, as well as molecular mechanisms for how this spatial organization controls receptor signaling.
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Could caveolae be acting as warnings of mitochondrial ageing? Mech Ageing Dev 2015; 146-148:81-7. [PMID: 25959712 DOI: 10.1016/j.mad.2015.04.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 04/09/2015] [Accepted: 04/28/2015] [Indexed: 11/20/2022]
Abstract
Ageing is a cellular process with many facets, some of which are currently undergoing a paradigm change. It is the case of "mitochondrial theory of ageing", which, interestingly, has been found lately to cross paths with another ageing dysfunctional process - intracellular signalling - in an unexpected point (or place) - caveolae. The latter represent membrane microdomains altered in senescent cells, scaffolded by proteins modified (posttranslational or as expression) with ageing. An important determinant of these alterations is oxidative stress, through increased production of reactive oxygen species that originate at mitochondrial site. Spanning from physical contact points, to shared structural proteins and similar function domains, caveolae and mitochondria might have more in common than originally thought. By reviewing recent data on oxidative stress impact on caveolae and caveolins, as well as possible interactions between caveolae and mitochondria, we propose a hypothesis for senescence-related involvement of caveolins.
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20
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Brejchová J, Sýkora J, Ostašov P, Merta L, Roubalová L, Janáček J, Hof M, Svoboda P. TRH-receptor mobility and function in intact and cholesterol-depleted plasma membrane of HEK293 cells stably expressing TRH-R-eGFP. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:781-96. [DOI: 10.1016/j.bbamem.2014.11.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 11/24/2014] [Accepted: 11/26/2014] [Indexed: 01/03/2023]
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21
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Peng Q, Jia SH, Parodo J, Ai Y, Marshall JC. Pre-B cell colony enhancing factor induces Nampt-dependent translocation of the insulin receptor out of lipid microdomains in A549 lung epithelial cells. Am J Physiol Endocrinol Metab 2015; 308:E324-33. [PMID: 25516545 DOI: 10.1152/ajpendo.00006.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Pre-B cell colony-enhancing factor (PBEF) is a highly conserved pleiotropic protein reported to be an alternate ligand for the insulin receptor (IR). We sought to clarify the relationship between PBEF and insulin signaling by evaluating the effects of PBEF on the localization of the IRβ chain to lipid rafts in A549 epithelial cells. We isolated lipid rafts from A549 cells and detected the IR by immunoprecipitation from raft fractions or whole cell lysates. Cells were treated with rPBEF, its enzymatic product nicotinamide adenine dinucleotide (NAD), or the Nampt inhibitor daporinad to study the effect of PBEF on IRβ movement. We used coimmunoprecipitation studies in cells transfected with PBEF and IRβ constructs to detect interactions between PBEF, the IRβ, and caveolin-1 (Cav-1). PBEF was present in both lipid raft and nonraft fractions, whereas the IR was found only in lipid raft fractions of resting A549 cells. The IR-, PBEF-, and Cav-1-coimmunoprecipitated rPBEF treatment resulted in the movement of IRβ- and tyrosine-phosphorylated Cav-1 from lipid rafts to nonrafts, an effect that could be blocked by daporinad, suggesting that this effect was facilitated by the Nampt activity of PBEF. The addition of PBEF to insulin-treated cells resulted in reduced Akt phosphorylation of both Ser⁴⁷³ and Thr³⁰⁸. We conclude that PBEF can inhibit insulin signaling through the IR by Nampt-dependent promotion of IR translocation into the nonraft domains of A549 epithelial cells. PBEF-induced alterations in the spatial geometry of the IR provide a mechanistic explanation for insulin resistance in inflammatory states associated with upregulation of PBEF.
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Affiliation(s)
- Qianyi Peng
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and the Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada; and Department of Critical Care Medicine, Xiangya Hospital, Central South University, Changsha, China
| | - Song Hui Jia
- Department of Surgery, Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and the Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada; and
| | - Jean Parodo
- Department of Surgery, Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and the Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada; and
| | - Yuhang Ai
- Department of Critical Care Medicine, Xiangya Hospital, Central South University, Changsha, China
| | - John C Marshall
- Department of Surgery, Department of Critical Care Medicine, and Keenan Research Centre for Biomedical Science, St. Michael's Hospital, and the Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada; and
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23
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Hakuno F, Fukushima T, Yoneyama Y, Kamei H, Ozoe A, Yoshihara H, Yamanaka D, Shibano T, Sone-Yonezawa M, Yu BC, Chida K, Takahashi SI. The Novel Functions of High-Molecular-Mass Complexes Containing Insulin Receptor Substrates in Mediation and Modulation of Insulin-Like Activities: Emerging Concept of Diverse Functions by IRS-Associated Proteins. Front Endocrinol (Lausanne) 2015; 6:73. [PMID: 26074875 PMCID: PMC4443775 DOI: 10.3389/fendo.2015.00073] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 04/25/2015] [Indexed: 12/25/2022] Open
Abstract
Insulin-like peptides, such as insulin-like growth factors (IGFs) and insulin, induce a variety of bioactivities, such as growth, differentiation, survival, increased anabolism, and decreased catabolism in many cell types and in vivo. In general, IGFs or insulin bind to IGF-I receptor (IGF-IR) or insulin receptor (IR), activating the receptor tyrosine kinase. Insulin receptor substrates (IRSs) are known to be major substrates of receptor kinases, mediating IGF/insulin signals to direct bioactivities. Recently, we discovered that IRSs form high-molecular-mass complexes (referred to here as IRSomes) even without IGF/insulin stimulation. These complexes contain proteins (referred to here as IRSAPs; IRS-associated proteins), which modulate tyrosine phosphorylation of IRSs by receptor kinases, control IRS stability, and determine intracellular localization of IRSs. In addition, in these complexes, we found not only proteins that are involved in RNA metabolism but also RNAs themselves. Thus, IRSAPs possibly contribute to modulation of IGF/insulin bioactivities. Since it is established that disorder of modulation of insulin-like activities causes various age-related diseases including cancer, we could propose that the IRSome is an important target for treatment of these diseases.
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Affiliation(s)
- Fumihiko Hakuno
- Department of Animal Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Toshiaki Fukushima
- Laboratory of Biomedical Chemistry, Basic Life Sciences, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
- Department of Biological Sciences, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Kanagawa, Japan
| | - Yosuke Yoneyama
- Department of Animal Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Hiroyasu Kamei
- Department of Animal Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Atsufumi Ozoe
- Department of Animal Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Hidehito Yoshihara
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Daisuke Yamanaka
- Department of Animal Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Takashi Shibano
- Department of Animal Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Meri Sone-Yonezawa
- Department of Animal Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Bu-Chin Yu
- Department of Animal Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Kazuhiro Chida
- Department of Animal Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Shin-Ichiro Takahashi
- Department of Animal Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo, Japan
- *Correspondence: Shin-Ichiro Takahashi, Laboratory of Cell Regulation, Departments of Animal Sciences and Applied Biological Chemistry, Graduate School of Agriculture and Life Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan,
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Cerqueira DM, Tran U, Romaker D, Abreu JG, Wessely O. Sterol carrier protein 2 regulates proximal tubule size in the Xenopus pronephric kidney by modulating lipid rafts. Dev Biol 2014; 394:54-64. [PMID: 25127994 DOI: 10.1016/j.ydbio.2014.07.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 05/29/2014] [Accepted: 07/30/2014] [Indexed: 11/29/2022]
Abstract
The kidney is a homeostatic organ required for waste excretion and reabsorption of water, salts and other macromolecules. To this end, a complex series of developmental steps ensures the formation of a correctly patterned and properly proportioned organ. While previous studies have mainly focused on the individual signaling pathways, the formation of higher order receptor complexes in lipid rafts is an equally important aspect. These membrane platforms are characterized by differences in local lipid and protein compositions. Indeed, the cells in the Xenopus pronephric kidney were positive for the lipid raft markers ganglioside GM1 and Caveolin-1. To specifically interfere with lipid raft function in vivo, we focused on the Sterol Carrier Protein 2 (scp2), a multifunctional protein that is an important player in remodeling lipid raft composition. In Xenopus, scp2 mRNA was strongly expressed in differentiated epithelial structures of the pronephric kidney. Knockdown of scp2 did not interfere with the patterning of the kidney along its proximo-distal axis, but dramatically decreased the size of the kidney, in particular the proximal tubules. This phenotype was accompanied by a reduction of lipid rafts, but was independent of the peroxisomal or transcriptional activities of scp2. Finally, disrupting lipid micro-domains by inhibiting cholesterol synthesis using Mevinolin phenocopied the defects seen in scp2 morphants. Together these data underscore the importance for localized signaling platforms in the proper formation of the Xenopus kidney.
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Affiliation(s)
- Débora M Cerqueira
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA; Universidade Federal do Rio de Janeiro, Instituto de Ciências Biomédicas-CCS, Av. Carlos Chagas Filho, 373 bloco F2 sala 15, Rio de Janeiro 21949-590, Brazil
| | - Uyen Tran
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA
| | - Daniel Romaker
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA
| | - José G Abreu
- Universidade Federal do Rio de Janeiro, Instituto de Ciências Biomédicas-CCS, Av. Carlos Chagas Filho, 373 bloco F2 sala 15, Rio de Janeiro 21949-590, Brazil
| | - Oliver Wessely
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA.
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Kheterpal I, Scherp P, Kelley L, Wang Z, Johnson W, Ribnicky D, Cefalu WT. Bioactives from Artemisia dracunculus L. enhance insulin sensitivity via modulation of skeletal muscle protein phosphorylation. Nutrition 2014; 30:S43-51. [PMID: 24985106 DOI: 10.1016/j.nut.2014.05.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
OBJECTIVES A botanical extract from Artemisia dracunculus L., termed PMI 5011, has been shown to improve insulin sensitivity by increasing cellular insulin signaling in in vitro and in vivo studies. These studies suggest that PMI 5011 effects changes in phosphorylation levels of proteins involved in insulin signaling. The aim of this study was to explore the effects of this promising botanical extract on the human skeletal muscle phosphoproteome, by evaluating changes in site-specific protein phosphorylation levels in primary skeletal muscle cultures from obese, insulin-resistant individuals stimulated with and without insulin. METHODS Insulin resistance is a condition in which a normal or elevated insulin level results in an abnormal biologic response, e.g., glucose uptake. Using isobaric tagging for relative and absolute quantification (iTRAQ™) followed by phosphopeptide enrichment and liquid chromatography-tandem mass spectrometry, 125 unique phosphopeptides and 159 unique phosphorylation sites from 80 unique proteins were identified and quantified. RESULTS Insulin stimulation of primary cultured muscle cells from insulin-resistant individuals resulted in minimal increase in phosphorylation, demonstrating impaired insulin action in this condition. Treatment with PMI 5011 resulted in significant up-regulation of 35 phosphopeptides that were mapped to proteins participating in the regulation of transcription, translation, actin cytoskeleton signaling, caveolae translocation, and translocation of glucose transporter 4. These data further showed that PMI 5011 increased phosphorylation levels of specific amino acids in proteins in the insulin-resistant state that are normally phosphorylated by insulin (thus, increasing cellular insulin signaling) and PMI 5011 also increased the abundance of phosphorylation sites of proteins regulating anti-apoptotic effects. CONCLUSION This phosphoproteomics analysis demonstrated conclusively that PMI 5011 effects changes in phosphorylation levels of proteins and identified novel pathways by which PMI 5011 exerts its insulin-sensitizing effects in skeletal muscle.
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Affiliation(s)
- Indu Kheterpal
- Protein Structural Biology and Proteomics and Metabolomics Core Facility, Pennington Biomedical Research Center, Louisiana State University System, Louisiana, USA
| | - Peter Scherp
- Protein Structural Biology and Proteomics and Metabolomics Core Facility, Pennington Biomedical Research Center, Louisiana State University System, Louisiana, USA
| | - Lauren Kelley
- Protein Structural Biology and Proteomics and Metabolomics Core Facility, Pennington Biomedical Research Center, Louisiana State University System, Louisiana, USA
| | - Zhong Wang
- Diabetes and Nutrition Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Louisiana, USA
| | - William Johnson
- Biostatistics and Data Management, Pennington Biomedical Research Center, Louisiana State University System, Louisiana, USA
| | - David Ribnicky
- Department of Plant Biology and Pathology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
| | - William T Cefalu
- Diabetes and Nutrition Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Louisiana, USA.
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Liu JC, Yu Y, Wang G, Wang K, Yang XG. Bis(acetylacetonato)-oxovanadium(iv), bis(maltolato)-oxovanadium(iv) and sodium metavanadate induce antilipolytic effects by regulating hormone-sensitive lipase and perilipin via activation of Akt. Metallomics 2014; 5:813-20. [PMID: 23576171 DOI: 10.1039/c3mt00001j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The increased plasma free fatty acid levels due to the deregulated lipolysis in adipocytes are considered as one of the major risk factors for developing type II diabetes. Vanadium compounds are well-known for their antidiabetic effects both on glucose and lipid metabolism, but the mechanisms are still not completely understood. The present study suggests a mechanism for how vanadium compounds exert antilipolytic effects. It demonstrates that all the three vanadium compounds, bis(acetylacetonato)-oxovanadium(iv) (VO(acac)2), bis(maltolato)-oxovanadium(iv) (VO(ma)2) and sodium metavanadate (NaVO3), attenuated basal lipolysis in 3T3L1 adipocytes in a dose- (from 100 to 400 μM for VO(acac)2 and VO(ma)2, 1.0 to 4.0 mM for vanadate) and time-dependent (from 0.5 to 4 h) manner using the glycerol release as a marker of lipolysis. In addition, the three compounds inhibited lipolysis to a different extent. Among them, VO(acac)2 (from 100 to 400 μM) exerted the most potent effect and reduced the lipolysis to ∼60-20% of control after 4 h treatment. The antilipolytic effects of vanadium compounds were further evidenced by a decrease of the levels of phosphorylated HSL at Ser660 and phosphorylated perilipin, which were counteracted by inhibitors of PI3K or Akt but not by an MEK inhibitor. This indicates that though both Akt and ERK pathways are activated by the vanadium compounds, only Akt activation contributes to the antilipolytic effect of the vanadium compounds, without the involvement of ERK activation. We previously demonstrated that VO(acac)2 can block cell cycle progression at the G1/S phase via a highly activated ERK signal in human hepatoma HepG2 cells. Together with this study, we show that similar activated pathways may lead to differential biological consequences for cancer cells and adipocytes, indicating that vanadium compounds may be used in the prevention and treatment of both diabetes and cancer.
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Affiliation(s)
- Jing-Cheng Liu
- State Key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing, People's Republic of China
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Methyl-β-cyclodextrin alters adipokine gene expression and glucose metabolism in swine adipose tissue. Animal 2013; 7:1690-6. [PMID: 23866961 DOI: 10.1017/s1751731113001250] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
This study was designed to determine whether methyl-β-cyclodextrin (MCD) can substitute for albumin in incubation medium for neonatal swine adipose tissue explants, or whether MCD affects metabolism and cytokine expression. Subcutaneous adipose tissue explants (100 ± 10 mg) were prepared from 21-day-old pigs. Explants were incubated in medium 199 supplemented with 25 mM HEPES, 1.0 nM insulin at 37°C. The medium also contained bovine serum albumin (BSA) or MCD at 0%, 0.05%, 0.1%, 0.2% or 0.3%. Tissue explants were treated with these media for 1 h and then switched to the same basal incubation medium containing 0.05% BSA. Explants were removed from basal medium at 2 or 8 h of incubation, and real-time PCR was performed to assess expression of tumor necrosis α (TNF) and interleukin 6 (IL6), acetyl CoA carboxylase (ACAC) and fatty acid synthase (FASN). Alternatively, rates of 14C-glucose oxidation and lipogenesis were monitored ± insulin (100 nM), following MCD treatment. Incubation with BSA had minimal effects on gene expression or adipose tissue metabolism, only producing a doubling in TNF mRNA abundance (P < 0.01). Treatment with MCD increased TNF mRNA abundance by eightfold (P < 0.009), whereas IL6 gene expression increased a 100-fold (P < 0.001) with a suppression in ACAC and FASN expression (P < 0.01). This was paralleled by MCD inhibition of insulin-stimulated glucose oxidation and lipogenesis (P < 0.001). Addition of a TNF antibody to the incubation medium alleviated this inhibition of insulin-stimulated glucose metabolism by ~30% (P < 0.05).
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Li H, Li H, Guo H, Liu F. Cholesterol suppresses adipocytic differentiation of mouse adipose-derived stromal cells via PPARγ2 signaling. Steroids 2013; 78:454-61. [PMID: 23454216 DOI: 10.1016/j.steroids.2013.02.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2012] [Revised: 01/24/2013] [Accepted: 02/04/2013] [Indexed: 12/14/2022]
Abstract
The effects of cholesterol on cell proliferation and adipocytic differentiation have been evaluated for the first time in mouse adipose-derived stromal cells (mASCs). Cholesterol loading by using cholesterol:methyl- β-cyclodextrin (Chol:MβCD) complexes promoted cellular levels of free cholesterol (FC) and cholesteryl ester (CE), induced high cell proliferation of mASCs dose-dependently. Compared with control cells, cholesterol-treated mASCs showed an impaired differentiation process in both dose- and time-dependent manners, based on reduced oil red O-stained lipid droplets, SREBP-1, PPARγ2 and aP2 expression levels. The involvement of SREBP-1-mediated PPARγ2 in the effects of cholesterol on mASC adipogenesis was elucidated. These results point to cholesterol as a modulator of adipogenesis, which separate cholesterol itself from other components of modified lipoproteins.
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Affiliation(s)
- Haifang Li
- College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China.
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Morino-Koga S, Yano S, Kondo T, Shimauchi Y, Matsuyama S, Okamoto Y, Suico MA, Koga T, Sato T, Shuto T, Arima H, Wada I, Araki E, Kai H. Insulin receptor activation through its accumulation in lipid rafts by mild electrical stress. J Cell Physiol 2013; 228:439-46. [PMID: 22740366 DOI: 10.1002/jcp.24149] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Insulin resistance is due to the reduced cellular response to insulin in peripheral tissues. The interaction of insulin with its receptor is the first step in insulin action and thus the identified target of insulin resistance. It has been well established that defects or mutations in the insulin receptor (IR) cause insulin resistance. Therefore, an IR activator might be a novel therapeutic approach for insulin resistance. Our previous report showed that mild electrical stress (MES) enhanced the insulin-induced signaling pathway. However, the molecular mechanism of the effect of MES remains unclear. We assessed the effect of MES, which is characterized by low-intensity direct current, on insulin signaling in vitro and in vivo. Here, we showed that MES activated the insulin signaling in an insulin-independent manner and improved insulin resistance in peripheral tissues of high fat-fed mice. Moreover, we found that MES increased the localization of IR in lipid rafts and enhanced the level of phosphorylated Akt in insulin-resistant hepatic cells. Ablation of lipid rafts disrupted the effect of MES on Akt activation. Our findings indicate that MES has potential as an activator of IR in an insulin-independent manner, and might be beneficial for insulin resistance in type 2 diabetes.
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Affiliation(s)
- Saori Morino-Koga
- Department of Molecular Medicine, Global COE Cell Fate Regulation Research and Education Unit, Kumamoto University, Kumamoto, Japan
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Caré BR, Soula HA. Receptor clustering affects signal transduction at the membrane level in the reaction-limited regime. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 87:012720. [PMID: 23410372 DOI: 10.1103/physreve.87.012720] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 12/19/2012] [Indexed: 06/01/2023]
Abstract
Many types of membrane receptors are found to be organized as clusters on the cell surface. We investigate the potential effect of such receptor clustering on the intracellular signal transduction stage. We consider a canonical pathway with a membrane receptor (R) activating a membrane-bound intracellular relay protein (G). We use Monte Carlo simulations to recreate biochemical reactions using different receptor spatial distributions and explore the dynamics of the signal transduction. Results show that activation of G by R is severely impaired by R clustering, leading to an apparent blunted biological effect compared to control. Paradoxically, this clustering decreases the half maximal effective dose (ED50) of the transduction stage, increasing the apparent affinity. We study an example of inter-receptor interaction in order to account for possible compensatory effects of clustering and observe the parameter range in which such interactions slightly counterbalance the loss of activation of G. The membrane receptors' spatial distribution affects the internal stages of signal amplification, suggesting a functional role for membrane domains and receptor clustering independently of proximity-induced receptor-receptor interactions.
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Affiliation(s)
- Bertrand R Caré
- Université de Lyon, LIRIS UMR 5205 CNRS-INSA, F-69621, Villeurbanne, France.
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31
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Abstract
Emerging experimental and human evidence has linked altered hepatic cholesterol homeostasis and free cholesterol (FC) accumulation to the pathogenesis of non-alcoholic steatohepatits (NASH). This review focuses on cellular mechanisms of cholesterol toxicity involved in liver injury and on alterations in cholesterol homeostasis promoting hepatic cholesterol overload in NASH. FC accumulation injures hepatocytes directly, by disrupting mitochondrial and endoplasmic reticulum (ER) membrane integrity, triggering mitochondrial oxidative injury and ER stress, and by promoting generation of toxic oxysterols, and indirectly, by inducing adipose tissue dysfunction. Accumulation of oxidized LDL particles may also activate Kupffer and hepatic stellate cells, promoting liver inflammation and fibrogenesis. Hepatic cholesterol accumulation is driven by a deeply deranged cellular cholesterol homeostasis, characterized by elevated cholesterol synthesis and uptake from circulating lipoproteins and by a reduced cholesterol excretion. Extensive dysregulation of cellular cholesterol homeostasis by nuclear transcription factors sterol regulatory binding protein (SREBP)-2, liver X-receptor (LXR)-α and farnesoid X receptor (FXR) plays a key role in hepatic cholesterol accumulation in NASH. The therapeutic implications and opportunities for normalizing cellular cholesterol homeostasis in these patients are also discussed.
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Al-Qatati A, Winter PW, Wolf-Ringwall AL, Chatterjee PB, Van Orden AK, Crans DC, Roess DA, Barisas BG. Insulin receptors and downstream substrates associate with membrane microdomains after treatment with insulin or chromium(III) picolinate. Cell Biochem Biophys 2012; 62:441-50. [PMID: 22101510 DOI: 10.1007/s12013-011-9326-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have examined the association of insulin receptors (IR) and downstream signaling molecules with membrane microdomains in rat basophilic leukemia (RBL-2H3) cells following treatment with insulin or tris(2-pyridinecarbxylato)chromium(III) (Cr(pic)(3)). Single-particle tracking demonstrated that individual IR on these cells exhibited reduced lateral diffusion and increased confinement within 100 nm-scale membrane compartments after treatment with either 200 nM insulin or 10 μM Cr(pic)(3). These treatments also increased the association of native IR, phosphorylated insulin receptor substrate 1 and phosphorylated AKT with detergent-resistant membrane microdomains of characteristically high buoyancy. Confocal fluorescence microscopic imaging of Di-4-ANEPPDHQ labeled RBL-2H3 cells also showed that plasma membrane lipid order decreased following treatment with Cr(pic)(3) but was not altered by insulin treatment. Fluorescence correlation spectroscopy demonstrated that Cr(pic)(3) did not affect IR cell-surface density or compete with insulin for available binding sites. Finally, Fourier transform infrared spectroscopy indicated that Cr(pic)(3) likely associates with the lipid interface in reverse-micelle model membranes. Taken together, these results suggest that activation of IR signaling in a cellular model system by both insulin and Cr(pic)(3) involves retention of IR in specialized nanometer-scale membrane microdomains but that the insulin-like effects of Cr(pic)(3) are due to changes in membrane lipid order rather than to direct interactions with IR.
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Affiliation(s)
- Abeer Al-Qatati
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
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33
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Nyman E, Fagerholm S, Jullesson D, Strålfors P, Cedersund G. Mechanistic explanations for counter-intuitive phosphorylation dynamics of the insulin receptor and insulin receptor substrate-1 in response to insulin in murine adipocytes. FEBS J 2012; 279:987-99. [PMID: 22248283 DOI: 10.1111/j.1742-4658.2012.08488.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Insulin signaling through insulin receptor (IR) and insulin receptor substrate-1 (IRS1) is important for insulin control of target cells. We have previously demonstrated a rapid and simultaneous overshoot behavior in the phosphorylation dynamics of IR and IRS1 in human adipocytes. Herein, we demonstrate that in murine adipocytes a similar overshoot behavior is not simultaneous for IR and IRS1. The peak of IRS1 phosphorylation, which is a direct consequence of the phosphorylation and the activation of IR, occurs earlier than the peak of IR phosphorylation. We used a conclusive modeling framework to unravel the mechanisms behind this counter-intuitive order of phosphorylation. Through a number of rejections, we demonstrate that two fundamentally different mechanisms may create the reversed order of peaks: (i) two pools of phosphorylated IR, where a large pool of internalized IR peaks late, but phosphorylation of IRS1 is governed by a small plasma membrane-localized pool of IR with an early peak, or (ii) inhibition of the IR-catalyzed phosphorylation of IRS1 by negative feedback. Although (i) may explain the reversed order, this two-pool hypothesis alone requires extensive internalization of IR, which is not supported by experimental data. However, with the additional assumption of limiting concentrations of IRS1, (i) can explain all data. Also, (ii) can explain all available data. Our findings illustrate how modeling can potentiate reasoning, to help draw nontrivial conclusions regarding competing mechanisms in signaling networks. Our work also reveals new differences between human and murine insulin signaling.
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Affiliation(s)
- Elin Nyman
- Department of Clinical and Experimental Medicine, Diabetes and Integrative Systems Biology, Linköping University, Sweden
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Winter PW, Al-Qatati A, Wolf-Ringwall AL, Schoeberl S, Chatterjee PB, Barisas BG, Roess DA, Crans DC. The anti-diabetic bis(maltolato)oxovanadium(iv) decreases lipid order while increasing insulin receptor localization in membrane microdomains. Dalton Trans 2012; 41:6419-30. [DOI: 10.1039/c2dt30521f] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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35
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Strålfors P. Caveolins and Caveolae, Roles in Insulin Signalling and Diabetes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 729:111-26. [DOI: 10.1007/978-1-4614-1222-9_8] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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36
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Sekimoto J, Kabayama K, Gohara K, Inokuchi JI. Dissociation of the insulin receptor from caveolae during TNFα-induced insulin resistance and its recovery byd-PDMP. FEBS Lett 2011; 586:191-5. [DOI: 10.1016/j.febslet.2011.12.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 12/14/2011] [Indexed: 12/01/2022]
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37
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Abstract
The combination of carbohydrate and lipid generates unusual molecules in which the two distinctive halves of the glycoconjugate influence the function of each other. Membrane glycolipids can act as primary receptors for carbohydrate binding proteins to mediate transmembrane signaling despite restriction to the outer bilayer leaflet. The extensive heterogeneity of the lipid moiety plays a significant, but still largely unknown, role in glycosphingolipid function. Potential interplay between glycolipids and their fatty acid isoforms, together with their preferential interaction with cholesterol, generates a complex mechanism for the regulation of their function in cellular physiology.
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Affiliation(s)
- Clifford A Lingwood
- Research Institute, Hospital for Sick Children, Molecular Structure and Function, Toronto, Ontario M5G 1X8, Canada.
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38
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Bäck K, Brännmark C, Strålfors P, Arnqvist HJ. Differential effects of IGF-I, IGF-II and insulin in human preadipocytes and adipocytes--role of insulin and IGF-I receptors. Mol Cell Endocrinol 2011; 339:130-5. [PMID: 21524684 DOI: 10.1016/j.mce.2011.04.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 04/08/2011] [Accepted: 04/08/2011] [Indexed: 01/06/2023]
Abstract
We compared insulin and IGF effects in adipocytes expressing IR (insulin receptors), and preadipocytes expressing IR and IGF-IR (IGF-I receptors). Treatment of adipocytes with insulin, IGF-II or IGF-I resulted in phosphorylation of IR. Order of potency was insulin>IGF-II>IGF-I. In preadipocytes IR, IGF-IR and insulin/IGF-I hybrid receptors (HR) were detected. Treatment of preadipocytes with IGF-I and IGF-II 10(-8)M resulted in activation of IGF-IR and IR whereas insulin was more potent in activating IR, with no effect on IGF-IR. In adipocytes glucose transport was 100-fold more sensitive to insulin than to IGFs and the maximal effect was higher with insulin. In preadipocytes glucose accumulation and DNA synthesis was equally sensitive to insulin and IGFs but the maximal effect was higher with IGF-I. In conclusion, insulin and IGF-I activate their cognate receptors and IGF-I also HR. IGF-II activates IR, IGF-IR and HR. Insulin and IGF-I are partial agonists to each other's receptors.
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Affiliation(s)
- Karolina Bäck
- Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology and Linköping Diabetes Research Centre, Linköping, Sweden.
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Inokuchi JI. Physiopathological function of hematoside (GM3 ganglioside). PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2011; 87:179-98. [PMID: 21558756 PMCID: PMC3149380 DOI: 10.2183/pjab.87.179] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Since I was involved in the molecular cloning of GM3 synthase (SAT-I), which is the primary enzyme for the biosynthesis of gangliosides in 1998, my research group has been concentrating on our efforts to explore the physiological and pathological implications of gangliosides especially for GM3. During the course of study, we demonstrated the molecular pathogenesis of type 2 diabetes and insulin resistance focusing on the interaction between insulin receptor and gangliosides in membrane microdomains and propose a new concept: Life style-related diseases, such as type 2 diabetes, are a membrane microdomain disorder caused by aberrant expression of gangliosides. We also encountered an another interesting aspect indicating the indispensable role of gangliosides in auditory system. After careful behavioral examinations of SAT-I knockout mice, their hearing ability was seriously impaired with selective degeneration of the stereocilia of hair cells in the organ of Corti. This is the first observation demonstrating a direct link between gangliosides and hearing functions.
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Affiliation(s)
- Jin-ichi Inokuchi
- Division of Glycopathology, Institute of Molecular Biomembranes and Glycobiology, Tohoku Pharmaceutical University, Miyagi, Japan.
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40
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Inhibition of ganglioside biosynthesis as a novel therapeutic approach in insulin resistance. Handb Exp Pharmacol 2011:165-78. [PMID: 21484572 DOI: 10.1007/978-3-642-17214-4_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A new concept "Life style-related diseases, such as type 2 diabetes, are a membrane microdomain disorder caused by aberrant expression of gangliosides" has arisen. By examining this working hypothesis, we demonstrate the molecular pathogenesis of type 2 diabetes and insulin resistance focusing on the interaction between insulin receptor and gangliosides in microdomains microdomains and propose the new therapeutic strategy "membrane microdomain ortho-signaling therapy".
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41
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Brännmark C, Palmér R, Glad ST, Cedersund G, Strålfors P. Mass and information feedbacks through receptor endocytosis govern insulin signaling as revealed using a parameter-free modeling framework. J Biol Chem 2010; 285:20171-9. [PMID: 20421297 DOI: 10.1074/jbc.m110.106849] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin and other hormones control target cells through a network of signal-mediating molecules. Such networks are extremely complex due to multiple feedback loops in combination with redundancy, shared signal mediators, and cross-talk between signal pathways. We present a novel framework that integrates experimental work and mathematical modeling to quantitatively characterize the role and relation between co-existing submechanisms in complex signaling networks. The approach is independent of knowing or uniquely estimating model parameters because it only relies on (i) rejections and (ii) core predictions (uniquely identified properties in unidentifiable models). The power of our approach is demonstrated through numerous iterations between experiments, model-based data analyses, and theoretical predictions to characterize the relative role of co-existing feedbacks governing insulin signaling. We examined phosphorylation of the insulin receptor and insulin receptor substrate-1 and endocytosis of the receptor in response to various different experimental perturbations in primary human adipocytes. The analysis revealed that receptor endocytosis is necessary for two identified feedback mechanisms involving mass and information transfer, respectively. Experimental findings indicate that interfering with the feedback may substantially increase overall signaling strength, suggesting novel therapeutic targets for insulin resistance and type 2 diabetes. Because the central observations are present in other signaling networks, our results may indicate a general mechanism in hormonal control.
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Affiliation(s)
- Cecilia Brännmark
- Division of Cell Biology, Department of Clinical and Experimental Medicine, Laboratory of Diabetes and Integrated Systems Biology, Linköping University, SE58185 Linköping, Sweden
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Differential regulation of adipocyte PDE3B in distinct membrane compartments by insulin and the beta3-adrenergic receptor agonist CL316243: effects of caveolin-1 knockdown on formation/maintenance of macromolecular signalling complexes. Biochem J 2009; 424:399-410. [PMID: 19747167 DOI: 10.1042/bj20090842] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In adipocytes, PDE3B (phosphodiesterase 3B) is an important regulatory effector in signalling pathways controlled by insulin and cAMP-increasing hormones. Stimulation of 3T3-L1 adipocytes with insulin or the beta3-adrenergic receptor agonist CL316243 (termed CL) indicated that insulin preferentially phosphorylated/activated PDE3B associated with internal membranes (endoplasmic reticulum/Golgi), whereas CL preferentially phosphorylated/activated PDE3B associated with caveolae. siRNA (small interfering RNA)-mediated KD (knockdown) of CAV-1 (caveolin-1) in 3T3-L1 adipocytes resulted in down-regulation of expression of membrane-associated PDE3B. Insulin-induced activation of PDE3B was reduced, whereas CL-mediated activation was almost totally abolished. Similar results were obtained in adipocytes from Cav-1-deficient mice. siRNA-mediated KD of CAV-1 in 3T3-L1 adipocytes also resulted in inhibition of CL-stimulated phosphorylation of HSL (hormone-sensitive lipase) and perilipin A, and of lipolysis. Superose 6 gel-filtration chromatography of solubilized membrane proteins from adipocytes stimulated with insulin or CL demonstrated the reversible assembly of distinct macromolecular complexes that contained 32P-phosphorylated PDE3B and signalling molecules thought to be involved in its activation. Insulin- and CL-induced macromolecular complexes were enriched in cholesterol, and contained certain common signalling proteins [14-3-3, PP2A (protein phosphatase 2A) and cav-1]. The complexes present in insulin-stimulated cells contained tyrosine-phosphorylated IRS-1 (insulin receptor substrate 1) and its downstream signalling proteins, whereas CL-activated complexes contained beta3-adrenergic receptor, PKA-RII [PKA (cAMP-dependent protein kinase)-regulatory subunit] and HSL. Insulin- and CL-mediated macromolecular complex formation was significantly inhibited by CAV-1 KD. These results suggest that cav-1 acts as a molecular chaperone or scaffolding molecule in cholesterol-rich lipid rafts that may be necessary for the proper stabilization and activation of PDE3B in response to CL and insulin.
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Inokuchi JI. Membrane microdomains and insulin resistance. FEBS Lett 2009; 584:1864-71. [PMID: 19822143 DOI: 10.1016/j.febslet.2009.10.012] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Revised: 10/03/2009] [Accepted: 10/06/2009] [Indexed: 11/18/2022]
Abstract
A new concept, that "metabolic disorders, such as type 2 diabetes, are membrane microdomain disorders caused by aberrant expression of gangliosides", has arisen. By examining this working hypothesis, we demonstrate the molecular pathogenesis of type 2 diabetes and insulin resistance focusing on the interaction between insulin receptor and gangliosides in microdomains and propose the new therapeutic strategy "membrane microdomain ortho-signaling therapy".
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Affiliation(s)
- Jin-ichi Inokuchi
- Division of Glycopathology, Institute of Molecular Biomembranes and Glycobiology, Tohoku Pharmaceutical University, Aoba-ku, Sendai, Miyagi, Japan.
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44
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Sánchez-Wandelmer J, Dávalos A, Herrera E, Giera M, Cano S, de la Peña G, Lasunción MA, Busto R. Inhibition of cholesterol biosynthesis disrupts lipid raft/caveolae and affects insulin receptor activation in 3T3-L1 preadipocytes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1731-9. [DOI: 10.1016/j.bbamem.2009.05.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2008] [Revised: 04/08/2009] [Accepted: 05/04/2009] [Indexed: 01/08/2023]
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Fagerholm S, Örtegren U, Karlsson M, Ruishalme I, Strålfors P. Rapid insulin-dependent endocytosis of the insulin receptor by caveolae in primary adipocytes. PLoS One 2009; 4:e5985. [PMID: 19543529 PMCID: PMC2695004 DOI: 10.1371/journal.pone.0005985] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2009] [Accepted: 05/25/2009] [Indexed: 11/30/2022] Open
Abstract
Background The insulin receptor is localized in caveolae and is dependent on caveolae or cholesterol for signaling in adipocytes. When stimulated with insulin, the receptor is internalized. Methodology/Principal Findings We examined primary rat adipocytes by subcellular fractionation to examine if the insulin receptor was internalized in a caveolae-mediated process. Insulin induced a rapid, t1/2<3 min, endocytosis of the insulin receptor in parallel with receptor tyrosine autophosphorylation. Concomitantly, caveolin-1 was phosphorylated at tyrosine(14) and endocytosed. Vanadate increased the phosphorylation of caveolin-1 without affecting insulin receptor phosphorylation or endocytosis. Immunocapture of endosomal vesicles with antibodies against the insulin receptor co-captured caveolin-1 and immunocapture with antibodies against tyrosine(14)-phosphorylated caveolin-1 co-captured the insulin receptor, demonstrating that the insulin receptor was endocytosed together with tyrosine(14)-phosphorylated caveolin-1. By immunogold electron microscopy the insulin receptor and caveolin-1 were colocalized in endosome vesicles that resembled caveosomes. Clathrin was not endocytosed with the insulin receptor and the inhibitor of clathrin-coated pit-mediated endocytosis, chlorpromazine, did not inhibit internalization of the insulin receptor, while transferrin receptor internalization was inhibited. Conclusion It is concluded that in response to insulin stimulation the autophosphorylated insulin receptor in primary adipocytes is rapidly endocytosed in a caveolae-mediated process, involving tyrosine phosphorylation of caveolin-1.
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Affiliation(s)
- Siri Fagerholm
- Division of Cell Biology, Department of Clinical and Experimental Medicine and Diabetes Research Centre, University of Linköping, Linköping, Sweden
| | - Unn Örtegren
- Division of Cell Biology, Department of Clinical and Experimental Medicine and Diabetes Research Centre, University of Linköping, Linköping, Sweden
| | - Margareta Karlsson
- Division of Cell Biology, Department of Clinical and Experimental Medicine and Diabetes Research Centre, University of Linköping, Linköping, Sweden
| | - Iida Ruishalme
- Division of Cell Biology, Department of Clinical and Experimental Medicine and Diabetes Research Centre, University of Linköping, Linköping, Sweden
| | - Peter Strålfors
- Division of Cell Biology, Department of Clinical and Experimental Medicine and Diabetes Research Centre, University of Linköping, Linköping, Sweden
- * E-mail:
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The differential protein and lipid compositions of noncaveolar lipid microdomains and caveolae. Cell Res 2009; 19:497-506. [PMID: 19255590 DOI: 10.1038/cr.2009.27] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Morphologically, caveolae and lipid rafts are two different membrane structures. They are often reported to share similar lipid and protein compositions, and are considered to be two subtypes of membrane lipid microdomains. By modifying sucrose density gradient flotation centrifugation, which is used to isolate lipid microdomains, we were able to separate caveolae and noncaveolar lipid microdomains into two distinct fractions. The caveolar membranes are membrane vesicles of 100-nm diameter, enriched with caveolin-1 and flotillin-1. The noncaveolar lipid microdomains are amorphous membranes and most likely the coalescence of heterogeneous lipid rafts. They are depleted of caveolin-1 and are more enriched with cholesterol and sphingolipids than the caveolae. Many membrane proteins, such as insulin-like growth factor-1 receptor (membrane receptor), aquaporin-1 (membrane transporter), Thy-1 and N-cadherin (glycosylphosphatidylinositol-anchored membrane protein and membrane glycoprotein), are specifically associated with noncaveolar lipid microdomains, but not with caveolae. These results indicate that the lipid and protein compositions of caveolae differ from those of noncaveolar lipid microdomains. The difference in their protein compositions implies that these two membrane microdomains may have different cellular functions.
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Bäck K, Arnqvist HJ. Changes in insulin and IGF-I receptor expression during differentiation of human preadipocytes. Growth Horm IGF Res 2009; 19:101-111. [PMID: 18693051 DOI: 10.1016/j.ghir.2008.06.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2008] [Revised: 06/18/2008] [Accepted: 06/27/2008] [Indexed: 01/02/2023]
Abstract
Mature adipocytes originate from fibroblast-like precursor cells, preadipocytes, which differentiate to obtain the characteristics of adipocytes. Our aim was to investigate how differentiation of human preadipocytes affects the distribution of insulin receptors (IR) and IGF-I receptors (IGF-IR) and other cell characteristics. Preadipocytes were differentiated using indomethacine, dexamethasone, isobutyl-methylxantine (IBMX) and high concentration of insulin. Gene expression was quantified by real-time RT-PCR in preadipocytes (PA), differentiated preadipocytes (dPA) and mature adipocytes (mAD). The amount of expressed receptor protein was analyzed using receptor specific ELISAs and Western blot. We also studied DNA synthesis with radiolabeled thymidine incorporation and glucose accumulation with radiolabeled glucose. Differentiation of PA increased gene expression of IR but not IGF-IR. GLUT4, growth hormone receptor (GHR) and adiponectin appeared or increased. In PA and dPA only IR-A was expressed whereas also IR-B was detected in mAD. By Western blot and ELISA, IR and IGF-IR were detected in PA, dPA and mAD. During differentiation the ratio of IR to IGF-IR increased severalfold. In PA both the IR and the IGF-IR was phosphorylated by their own ligand at 1 nM and in dPA the activation of both receptors was stimulated by IGF-I, but not insulin, at 1 nM. Accumulation of glucose in PA was increased by insulin at 10nM and by IGF-I at 1 nM and 10nM. DNA synthesis was increased by insulin and IGF-I at 10nM. In conclusion, both IR and IGF-IR are present in human preadipocytes and adipocytes. Differentiation is characterized by an increased IR/IGF-IR ratio.
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Affiliation(s)
- Karolina Bäck
- Linköping University, Faculty of Health Sciences, Department of Clinical and Experimental Medicine, Division of Cell Biology, S-581 85 Linköping, Sweden.
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Anderson N, Borlak J. Molecular Mechanisms and Therapeutic Targets in Steatosis and Steatohepatitis. Pharmacol Rev 2008; 60:311-57. [DOI: 10.1124/pr.108.00001] [Citation(s) in RCA: 291] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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Hahn-Obercyger M, Graeve L, Madar Z. A high-cholesterol diet increases the association between caveolae and insulin receptors in rat liver. J Lipid Res 2008; 50:98-107. [PMID: 18757837 DOI: 10.1194/jlr.m800441-jlr200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Caveolin-1, a component of caveolae, regulates signaling pathway compartmentalization by interacting with tyrosine (Tyr) kinase receptors and their substrates. Perturbations in caveolae lipid composition have been shown in vitro to displace proteins from lipid microdomains, thereby altering their functionality and subsequent downstream signaling. The role of caveolin-1 in insulin receptor (IR) signaling has been widely investigated in vitro mainly in 3T3-L1 adipocyte cells. However, in vivo experiments investigating this connection in liver tissue have not been carried out. The objective of the present study was to investigate the effects of a high-cholesterol diet on caveolin-1 expression and IR localization and activity in the rat liver. Compared with a standard diet, rats fed with diet rich in cholesterol significantly altered liver caveolae by increasing both caveolin-1 (66%, P < 0.05) and caveolin-2 (55%, P < 0.05) expression while caveolin-1 mRNA levels were reduced. Concomitantly, a 25% increase in localization of the caveolae-resident signaling protein IR was observed. The distribution of caveolar and noncaveolar phosphorylated IR was unaffected but insulin-induced IR activation was significantly enhanced following consumption of the high-cholesterol diet (120%, P < 0.001). However, the downstream molecules IRS-1 and Akt have shown impaired activity in cholesterol-fed rats suggesting insulin resistance condition. Insulin stimulation failed to induce Tyr phosphorylation of caveolin-1 in cholesterol-fed rats. These findings suggest a mechanism by which a high-cholesterol diet altered caveolin-1 expression in vivo accompanied by altered IR localization and activity.
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Affiliation(s)
- Michal Hahn-Obercyger
- The Hebrew University of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, Institute of Biochemistry, Food Science and Nutrition, Rehovot, Israel
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Abstract
The mitogen-activated protein kinase (MAPK) pathway provides cells with the means to interpret external signal cues or conditions, and respond accordingly. This cascade regulates many cell functions such as differentiation, proliferation and migration. Through modulation of both the amplitude and duration of MAPK signalling, cells can control their responses to the multiple activators of the pathway. In addition, recent work has highlighted the importance of the cellular compartment from which the signalling occurs. Cells have developed intricate systems that enable them to localise MAPK components to specific subcellular domains in response to a particular stimulus. Consequently, different factors can activate the same kinase in separate locations. Crucial to this ability are molecular scaffolds, which act as signalling modules for MAPKs, confining them to the desired compartment. The participation of the MAPK network in fundamental physiological processes, such as cell proliferation and inflammation, and the derangement of the homeostasis that occurs in disease processes, renders MAPK a highly desirable target for therapeutic intervention. As we enhance our comprehension of scaffolds and other regulatory molecules, novel targets for drug design may be discovered that will afford selective and specific MAPK modulation.
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Affiliation(s)
- M D Brown
- Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
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