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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Aji G, Jiang S, Obulkasim H, Lu Z, Wang W, Xia P. Sphingosine kinase 2 regulates insulin receptor trafficking in hepatocytes. Exp Biol Med (Maywood) 2023; 248:44-51. [PMID: 36408724 PMCID: PMC9989153 DOI: 10.1177/15353702221131886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Disturbed insulin receptor (InsR) trafficking is associated with impaired insulin signaling and the development of diabetes. Sphingosine kinase (SphK), including SphK1 and SphK2, is a key enzyme of sphingolipid metabolism, which has been implicated in the regulation of membrane trafficking. More recently, we have reported that SphK2 is a key regulator of hepatic insulin signaling and glucose homeostasis. However, the role of SphK in InsR trafficking is still undefined. Huh7 cells were treated with specific SphK1 and SphK2 inhibitors or SphK1- and SphK2-specific small interfering RNA (siRNA) in the presence or absence of insulin. Flow cytometry and immunofluorescence assays were carried out to investigate the role of SphK in InsR trafficking. InsR endocytosis, recycling, and insulin signaling were analyzed. Inhibition of SphK2, but not SphK1, by either specific pharmaceutic inhibitors or siRNA, significantly suppressed InsR endocytosis and recycling following insulin stimulation. Consequently, the insulin-stimulated Akt activation was significantly attenuated by SphK2 inhibition in hepatocytes. Moreover, the effect of SphK2 on InsR trafficking was mediated via the clathrin-dependent mechanism. Thus, our results show that SphK2 is able to regulate InsR trafficking. These findings suggest that SphK2 may impinge on hepatic insulin signaling by regulating InsR trafficking, providing further mechanistic evidence that SphK2 could serve as a potential intervention target against insulin resistance and T2D (type 2 diabetes).
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Affiliation(s)
- Gulibositan Aji
- State Key Laboratory of Pathogenesis, Prevention and Treatment of High Incidence Diseases in Central Asia, Department of Endocrinology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830000, China.,Department of Endocrinology and Metabolism, Zhongshan Hospital and Fudan Institute for Metabolic Diseases, Fudan University, Shanghai 200032, China
| | - Sheng Jiang
- State Key Laboratory of Pathogenesis, Prevention and Treatment of High Incidence Diseases in Central Asia, Department of Endocrinology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830000, China
| | - Halmurat Obulkasim
- Department of General Surgery, Traditional Chinese Medicine Hospital Affiliated to Xinjiang Medical University, Urumqi 830000, China
| | - Zhiqiang Lu
- Department of Endocrinology and Metabolism, Zhongshan Hospital and Fudan Institute for Metabolic Diseases, Fudan University, Shanghai 200032, China
| | - Wei Wang
- Department of Endocrinology and Metabolism, Zhongshan Hospital and Fudan Institute for Metabolic Diseases, Fudan University, Shanghai 200032, China
| | - Pu Xia
- Department of Endocrinology and Metabolism, Zhongshan Hospital and Fudan Institute for Metabolic Diseases, Fudan University, Shanghai 200032, China
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4
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Umebayashi M, Takemoto S, Reymond L, Sundukova M, Hovius R, Bucci A, Heppenstall PA, Yokota H, Johnsson K, Riezman H. A covalently linked probe to monitor local membrane properties surrounding plasma membrane proteins. J Cell Biol 2022; 222:213783. [PMID: 36571579 PMCID: PMC9802683 DOI: 10.1083/jcb.202206119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 09/21/2022] [Accepted: 12/09/2022] [Indexed: 12/27/2022] Open
Abstract
Functional membrane proteins in the plasma membrane are suggested to have specific membrane environments that play important roles to maintain and regulate their function. However, the local membrane environments of membrane proteins remain largely unexplored due to the lack of available techniques. We have developed a method to probe the local membrane environment surrounding membrane proteins in the plasma membrane by covalently tethering a solvatochromic, environment-sensitive dye, Nile Red, to a GPI-anchored protein and the insulin receptor through a flexible linker. The fluidity of the membrane environment of the GPI-anchored protein depended upon the saturation of the acyl chains of the lipid anchor. The local environment of the insulin receptor was distinct from the average plasma membrane fluidity and was quite dynamic and heterogeneous. Upon addition of insulin, the local membrane environment surrounding the receptor specifically increased in fluidity in an insulin receptor-kinase dependent manner and on the distance between the dye and the receptor.
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Affiliation(s)
- Miwa Umebayashi
- https://ror.org/01swzsf04Department of Biochemistry and National Centre for Competence in Research in Chemical Biology, Sciences II, University of Geneva, Geneva, Switzerland,Myoridge Co. Ltd., Kyoto, Japan
| | - Satoko Takemoto
- Image Processing Research Team, RIKEN Centre for Advanced Photonics, Wako, Japan
| | - Luc Reymond
- Ecole Polytechnique Fédérale de Lausanne, Institute of Chemical Sciences and Engineering (ISIC), Institute of Bioengineering, National Centre of Competence in Research (NCCR) in Chemical Biology, Lausanne, Switzerland
| | - Mayya Sundukova
- Epigenetics and Neurobiology Unit, European Molecular Biology Laboratory Rome, Monterotondo, Italy,https://ror.org/000xsnr85Instituto Biofisika (UPV/EHU, CSIC), University of the Basque Country, Leioa, Spain,Fundación Biofísica Bizkaia/Biofisika Bizkaia Fundazioa (FBB), Leioa, Spain
| | - Ruud Hovius
- Ecole Polytechnique Fédérale de Lausanne, Institute of Chemical Sciences and Engineering (ISIC), Institute of Bioengineering, National Centre of Competence in Research (NCCR) in Chemical Biology, Lausanne, Switzerland
| | - Annalisa Bucci
- Epigenetics and Neurobiology Unit, European Molecular Biology Laboratory Rome, Monterotondo, Italy
| | - Paul A. Heppenstall
- Epigenetics and Neurobiology Unit, European Molecular Biology Laboratory Rome, Monterotondo, Italy
| | - Hideo Yokota
- Image Processing Research Team, RIKEN Centre for Advanced Photonics, Wako, Japan
| | - Kai Johnsson
- Department of Chemical Biology, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Howard Riezman
- https://ror.org/01swzsf04Department of Biochemistry and National Centre for Competence in Research in Chemical Biology, Sciences II, University of Geneva, Geneva, Switzerland,Correspondence to Howard Riezman:
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5
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Higuchi Y, Ogata T, Nakanishi N, Nishi M, Sakamoto A, Tsuji Y, Tomita S, Matoba S. Requirement of Cavin-2 for the expression and stability of IRβ in adequate adipocyte differentiation. Mol Metab 2021; 55:101416. [PMID: 34896640 PMCID: PMC8728525 DOI: 10.1016/j.molmet.2021.101416] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 11/29/2021] [Accepted: 12/07/2021] [Indexed: 12/22/2022] Open
Abstract
Objective Adipogenesis plays an essential role in maintaining energy and hormonal balance. Cavin-2, one of the caveolae-related proteins, is abundant in adipocytes, the leading site of adipogenesis. However, the details of the roles of Cavin-2 in adipogenesis remain unknown. Here, we demonstrate the requirement of Cavin-2 for the expression and stability of IRβ in adequate adipocyte differentiation. Methods Cavin-2 knockout (Cavin-2 KO) and wild-type (WT) mice were fed with a high-fat diet (HFD) for 8 weeks. We evaluated body weight, food intake, and several tissues. Glucose homeostasis was assessed by glucose and insulin tolerance tests. Insulin signaling in epididymal white adipose tissue (eWAT) was determined by Akt phosphorylation. In vitro study, we evaluated adipocyte differentiation, adipogenesis-related genes, and insulin signaling to clarify the relationship between Cavin-2 and adipogenesis under the manipulation of Cavin-2 expression. Results Caveolae structure decreased in eWAT of Cavin-2 KO mice and Cavin-2 knockdown 3T3-L1 cells. Cavin-2 enhanced the stability of insulin receptor (IR) through direct association at the plasma membrane in adipocytes, resulting in accelerated insulin/IR/Akt signaling-induced adipogenic gene expression in insulin-containing solution-stimulated 3T3-L1 adipocytes. IR-mediated Akt activation also enhanced Cavin-2 and IR expression. Cavin-2 knockout mice showed insulin resistance with dyslipidemia and pathological hypertrophic adipocytes after a HFD. Conclusions Cavin-2 enhances IR stability through binding IR and regulates insulin signaling, promoting adequate adipocyte differentiation. Our findings highlight the pivotal role of Cavin-2 in adipogenesis and lipid metabolism, which may help to develop novel therapies for pathological obesity and adipogenic disorders. Cavin-2 expression is increased progressively during adipocyte differentiation. Cavin-2 knockout shows little caveolae in 3T3L-1 adipocytes and eWAT of mice. Cavin-2 positively regulates adipogenesis through IR stabilization. Cavin-2 knockout mice with a high-fat diet show insulin resistance and dyslipidemia.
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Affiliation(s)
- Yusuke Higuchi
- Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
| | - Takehiro Ogata
- Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan; Department of Pathology and Cell Regulation, Graduate School of Medical Sciences, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
| | - Naohiko Nakanishi
- Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
| | - Masahiro Nishi
- Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
| | - Akira Sakamoto
- Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
| | - Yumika Tsuji
- Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
| | - Shinya Tomita
- Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
| | - Satoaki Matoba
- Department of Cardiovascular Medicine, Graduate School of Medical Sciences, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
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6
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Ferrara PJ, Rong X, Maschek JA, Verkerke AR, Siripoksup P, Song H, Green TD, Krishnan KC, Johnson JM, Turk J, Houmard JA, Lusis AJ, Drummond MJ, McClung JM, Cox JE, Shaikh SR, Tontonoz P, Holland WL, Funai K. Lysophospholipid acylation modulates plasma membrane lipid organization and insulin sensitivity in skeletal muscle. J Clin Invest 2021; 131:135963. [PMID: 33591957 DOI: 10.1172/jci135963] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 02/11/2021] [Indexed: 01/09/2023] Open
Abstract
Aberrant lipid metabolism promotes the development of skeletal muscle insulin resistance, but the exact identity of lipid-mediated mechanisms relevant to human obesity remains unclear. A comprehensive lipidomic analysis of primary myocytes from individuals who were insulin-sensitive and lean (LN) or insulin-resistant with obesity (OB) revealed several species of lysophospholipids (lyso-PLs) that were differentially abundant. These changes coincided with greater expression of lysophosphatidylcholine acyltransferase 3 (LPCAT3), an enzyme involved in phospholipid transacylation (Lands cycle). Strikingly, mice with skeletal muscle-specific knockout of LPCAT3 (LPCAT3-MKO) exhibited greater muscle lysophosphatidylcholine/phosphatidylcholine, concomitant with improved skeletal muscle insulin sensitivity. Conversely, skeletal muscle-specific overexpression of LPCAT3 (LPCAT3-MKI) promoted glucose intolerance. The absence of LPCAT3 reduced phospholipid packing of cellular membranes and increased plasma membrane lipid clustering, suggesting that LPCAT3 affects insulin receptor phosphorylation by modulating plasma membrane lipid organization. In conclusion, obesity accelerates the skeletal muscle Lands cycle, whose consequence might induce the disruption of plasma membrane organization that suppresses muscle insulin action.
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Affiliation(s)
- Patrick J Ferrara
- Diabetes and Metabolism Research Center and.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, USA.,East Carolina Diabetes and Obesity Institute and.,Human Performance Laboratory, East Carolina University, Greenville, North Carolina, USA.,Molecular Medicine Program, University of Utah, Salt Lake City, Utah, USA
| | - Xin Rong
- Department of Pathology and Laboratory Medicine, UCLA, Los Angeles, California, USA
| | - J Alan Maschek
- Diabetes and Metabolism Research Center and.,Metabolomics, Mass Spectrometry, and Proteomics Core and
| | - Anthony Rp Verkerke
- Diabetes and Metabolism Research Center and.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, USA.,East Carolina Diabetes and Obesity Institute and.,Human Performance Laboratory, East Carolina University, Greenville, North Carolina, USA
| | - Piyarat Siripoksup
- Diabetes and Metabolism Research Center and.,Department of Physical Therapy and Athletic Training, University of Utah, Salt Lake City, Utah, USA
| | - Haowei Song
- Division of Endocrinology Metabolism and Lipid Research, School of Medicine, Washington University in St. Louis, St. Louis, Missouri, USA
| | | | | | - Jordan M Johnson
- Diabetes and Metabolism Research Center and.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, USA.,East Carolina Diabetes and Obesity Institute and.,Human Performance Laboratory, East Carolina University, Greenville, North Carolina, USA
| | - John Turk
- Division of Endocrinology Metabolism and Lipid Research, School of Medicine, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Joseph A Houmard
- East Carolina Diabetes and Obesity Institute and.,Human Performance Laboratory, East Carolina University, Greenville, North Carolina, USA
| | - Aldons J Lusis
- Cardiology Division, Department of Medicine, UCLA, Los Angeles, California, USA
| | - Micah J Drummond
- Diabetes and Metabolism Research Center and.,Molecular Medicine Program, University of Utah, Salt Lake City, Utah, USA.,Department of Physical Therapy and Athletic Training, University of Utah, Salt Lake City, Utah, USA
| | | | - James E Cox
- Diabetes and Metabolism Research Center and.,Metabolomics, Mass Spectrometry, and Proteomics Core and.,Department of Biochemistry, University of Utah, Salt Lake City, Utah, USA
| | - Saame Raza Shaikh
- East Carolina Diabetes and Obesity Institute and.,Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, UCLA, Los Angeles, California, USA
| | - William L Holland
- Diabetes and Metabolism Research Center and.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, USA.,Molecular Medicine Program, University of Utah, Salt Lake City, Utah, USA
| | - Katsuhiko Funai
- Diabetes and Metabolism Research Center and.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, USA.,East Carolina Diabetes and Obesity Institute and.,Human Performance Laboratory, East Carolina University, Greenville, North Carolina, USA.,Molecular Medicine Program, University of Utah, Salt Lake City, Utah, USA.,Department of Physical Therapy and Athletic Training, University of Utah, Salt Lake City, Utah, USA
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7
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Lim K, Haider A, Adams C, Sleigh A, Savage DB. Lipodistrophy: a paradigm for understanding the consequences of "overloading" adipose tissue. Physiol Rev 2020; 101:907-993. [PMID: 33356916 DOI: 10.1152/physrev.00032.2020] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Lipodystrophies have been recognized since at least the nineteenth century and, despite their rarity, tended to attract considerable medical attention because of the severity and somewhat paradoxical nature of the associated metabolic disease that so closely mimics that of obesity. Within the last 20 yr most of the monogenic subtypes have been characterized, facilitating family genetic screening and earlier disease detection as well as providing important insights into adipocyte biology and the systemic consequences of impaired adipocyte function. Even more recently, compelling genetic studies have suggested that subtle partial lipodystrophy is likely to be a major factor in prevalent insulin-resistant type 2 diabetes mellitus (T2DM), justifying the longstanding interest in these disorders. This progress has also underpinned novel approaches to treatment that, in at least some patients, can be of considerable therapeutic benefit.
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Affiliation(s)
- Koini Lim
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom
| | - Afreen Haider
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom
| | - Claire Adams
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom
| | - Alison Sleigh
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom
| | - David B Savage
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom
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8
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Wu L, Liu T, Gu Y. Microvillar dynamic in renal tubular epithelial cells mediated by insulin/PLCγ signal pathway. Biochem Biophys Res Commun 2020; 534:1020-1025. [PMID: 33131771 DOI: 10.1016/j.bbrc.2020.10.046] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 10/17/2020] [Indexed: 10/23/2022]
Abstract
Significant cellular morphology changes in renal tubules were observed in diabetes patients and animal models. However, the interaction between insulin and tubular epithelial cells microvillar structure remains obscure. To understand microvillar dynamics, we used Scanning Ion Conductance Microscope to visualize microvillar in the living cell. Here, we found two layers of microvilli on the tubular epithelial cell surface: short compact microvilli and netlike long microvilli. Insulin treatment could increase microvilli length and density. This process was mediated by the PI3K/PLCγ signaling pathway, other than the PI3K/Arp2/3 signal pathway. In conclusion, our findings present a novel insulin signaling transduction mechanism, which contributes to understanding renal tubular epithelial cell microvilli dynamic regulation.
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Affiliation(s)
- Lida Wu
- Molecular Pharmacology Laboratory, Institute of Molecular Medicine, Peking University, 100871, Beijing, China; Translational and Regenerative Medicine Centre, Aston Medical School, Aston University, Birmingham, B4 7ET, UK
| | - Tongri Liu
- Molecular Pharmacology Laboratory, Institute of Molecular Medicine, Peking University, 100871, Beijing, China
| | - Yuchun Gu
- Molecular Pharmacology Laboratory, Institute of Molecular Medicine, Peking University, 100871, Beijing, China; Translational and Regenerative Medicine Centre, Aston Medical School, Aston University, Birmingham, B4 7ET, UK.
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9
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Keeping in touch with the membrane; protein- and lipid-mediated confinement of caveolae to the cell surface. Biochem Soc Trans 2020; 48:155-163. [PMID: 32049332 PMCID: PMC7054752 DOI: 10.1042/bst20190386] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 01/16/2020] [Accepted: 01/17/2020] [Indexed: 12/29/2022]
Abstract
Caveolae are small Ω-shaped invaginations of the plasma membrane that play important roles in mechanosensing, lipid homeostasis and signaling. Their typical morphology is characterized by a membrane funnel connecting a spherical bulb to the membrane. Membrane funnels (commonly known as necks and pores) are frequently observed as transient states during fusion and fission of membrane vesicles in cells. However, caveolae display atypical dynamics where the membrane funnel can be stabilized over an extended period of time, resulting in cell surface constrained caveolae. In addition, caveolae are also known to undergo flattening as well as short-range cycles of fission and fusion with the membrane, requiring that the membrane funnel closes or opens up, respectively. This mini-review considers the transition between these different states and highlights the role of the protein and lipid components that have been identified to control the balance between surface association and release of caveolae.
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10
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Wong SW, Lenzini S, Cooper MH, Mooney DJ, Shin JW. Soft extracellular matrix enhances inflammatory activation of mesenchymal stromal cells to induce monocyte production and trafficking. SCIENCE ADVANCES 2020; 6:eaaw0158. [PMID: 32284989 PMCID: PMC7141831 DOI: 10.1126/sciadv.aaw0158] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 01/14/2020] [Indexed: 05/17/2023]
Abstract
Mesenchymal stromal cells (MSCs) modulate immune cells to ameliorate multiple inflammatory pathologies. Biophysical signals that regulate this process are poorly defined. By engineering hydrogels with tunable biophysical parameters relevant to bone marrow where MSCs naturally reside, we show that soft extracellular matrix maximizes the ability of MSCs to produce paracrine factors that have been implicated in monocyte production and chemotaxis upon inflammatory stimulation by tumor necrosis factor-α (TNFα). Soft matrix increases clustering of TNF receptors, thereby enhancing NF-κB activation and downstream gene expression. Actin polymerization and lipid rafts, but not myosin-II contractility, regulate mechanosensitive activation of MSCs by TNFα. We functionally demonstrate that human MSCs primed with TNFα in soft matrix enhance production of human monocytes in marrow of xenografted mice and increase trafficking of monocytes via CCL2. The results suggest the importance of biophysical signaling in tuning inflammatory activation of stromal cells to control the innate immune system.
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Affiliation(s)
- Sing Wan Wong
- Department of Pharmacology and Department of Bioengineering, University of Illinois at Chicago College of Medicine, Chicago, IL, USA
| | - Stephen Lenzini
- Department of Pharmacology and Department of Bioengineering, University of Illinois at Chicago College of Medicine, Chicago, IL, USA
| | - Madeline H. Cooper
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - David J. Mooney
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Jae-Won Shin
- Department of Pharmacology and Department of Bioengineering, University of Illinois at Chicago College of Medicine, Chicago, IL, USA
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11
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Caveolae: Formation, dynamics, and function. Curr Opin Cell Biol 2020; 65:8-16. [PMID: 32146331 DOI: 10.1016/j.ceb.2020.02.001] [Citation(s) in RCA: 82] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 01/28/2020] [Accepted: 02/02/2020] [Indexed: 12/22/2022]
Abstract
Caveolae are abundant surface pits formed by the assembly of cytoplasmic proteins on a platform generated by caveolin integral membrane proteins and membrane lipids. This membranous assembly can bud off into the cell or can be disassembled releasing the cavin proteins into the cytosol. Disassembly can be triggered by increased membrane tension, or by stress stimuli, such as UV. Here, we discuss recent mechanistic studies showing how caveolae are formed and how their unique properties allow them to function as multifunctional protective and signaling structures.
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12
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Gunasekar SK, Xie L, Sah R. SWELL signalling in adipocytes: can fat 'feel' fat? Adipocyte 2019; 8:223-228. [PMID: 31112068 PMCID: PMC6768237 DOI: 10.1080/21623945.2019.1612223] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/18/2019] [Accepted: 04/19/2019] [Indexed: 01/04/2023] Open
Abstract
Obesity is becoming a global epidemic, predisposing to Type 2 diabetes, cardiovascular disease, fatty liver disease, pulmonary disease, osteoarthritis and cancer. Therefore, understanding the biology of adipocyte expansion in response to overnutrition is critical to devising strategies to treat obesity, and the associated burden of morbidity and mortality. Through exploratory patch-clamp experiments in freshly isolated primary murine and human adipocytes, we recently determined that SWELL1/LRRC8a, a leucine-rich repeat containing transmembrane protein, functionally encoded an ion channel signalling complex (the volume-regulated anion channel, or VRAC) on the adipocyte plasma membrane. The SWELL1-/LRRC8 channel complex activates in response to increases in adipocyte volume and in the context of obesity. SWELL1 is also required for insulin-PI3K-AKT2 signalling to regulate adipocyte growth and systemic glycaemia. This commentary delves further into our working models for the molecular mechanisms of adipocyte SWELL1-mediated VRAC activation, proposed signal transduction mechanisms, and putative impact on adipocyte hypertrophy during caloric excess.
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Affiliation(s)
- Susheel K. Gunasekar
- Department of Internal Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA
| | - Litao Xie
- Department of Internal Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA
| | - Rajan Sah
- Department of Internal Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA
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13
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Grice BA, Barton KJ, Covert JD, Kreilach AM, Tackett L, Brozinick JT, Elmendorf JS. Excess membrane cholesterol is an early contributing reversible aspect of skeletal muscle insulin resistance in C57BL/6NJ mice fed a Western-style high-fat diet. Am J Physiol Endocrinol Metab 2019; 317:E362-E373. [PMID: 31237447 PMCID: PMC6732462 DOI: 10.1152/ajpendo.00396.2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Skeletal muscle insulin resistance manifests shortly after high-fat feeding, yet mechanisms are not known. Here we set out to determine whether excess skeletal muscle membrane cholesterol and cytoskeletal derangement known to compromise glucose transporter (GLUT)4 regulation occurs early after high-fat feeding. We fed 6-wk-old male C57BL/6NJ mice either a low-fat (LF, 10% kcal) or a high-fat (HF, 45% kcal) diet for 1 wk. This HF feeding challenge was associated with an increase, albeit slight, in body mass, glucose intolerance, and hyperinsulinemia. Liver analyses did not reveal signs of hepatic insulin resistance; however, skeletal muscle immunoblots of triad-enriched regions containing transverse tubule membrane showed a marked loss of stimulated GLUT4 recruitment. An increase in cholesterol was also found in these fractions from HF-fed mice. These derangements were associated with a marked loss of cortical filamentous actin (F-actin) that is essential for GLUT4 regulation and known to be compromised by increases in membrane cholesterol. Both the withdrawal of the HF diet and two subcutaneous injections of the cholesterol-lowering agent methyl-β-cyclodextrin at 3 and 6 days during the 1-wk HF feeding intervention completely mitigated cholesterol accumulation, cortical F-actin loss, and GLUT4 dysregulation. Moreover, these beneficial membrane/cytoskeletal changes occurred concomitant with a full restoration of metabolic responses. These results identify skeletal muscle membrane cholesterol accumulation as an early, reversible, feature of insulin resistance and suggest cortical F-actin loss as an early derangement of skeletal muscle insulin resistance.
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Affiliation(s)
- Brian A Grice
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
| | - Kelly J Barton
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
| | - Jacob D Covert
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
| | - Alec M Kreilach
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
| | - Lixuan Tackett
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
| | - Joseph T Brozinick
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
- Eli Lilly and Company, Indianapolis, Indiana
| | - Jeffrey S Elmendorf
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, Indiana
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14
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Sugiyama MG, Fairn GD, Antonescu CN. Akt-ing Up Just About Everywhere: Compartment-Specific Akt Activation and Function in Receptor Tyrosine Kinase Signaling. Front Cell Dev Biol 2019; 7:70. [PMID: 31131274 PMCID: PMC6509475 DOI: 10.3389/fcell.2019.00070] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 04/09/2019] [Indexed: 12/12/2022] Open
Abstract
The serine/threonine kinase Akt is a master regulator of many diverse cellular functions, including survival, growth, metabolism, migration, and differentiation. Receptor tyrosine kinases are critical regulators of Akt, as a result of activation of phosphatidylinositol-3-kinase (PI3K) signaling leading to Akt activation upon receptor stimulation. The signaling axis formed by receptor tyrosine kinases, PI3K and Akt, as well as the vast range of downstream substrates is thus central to control of cell physiology in many different contexts and tissues. This axis must be tightly regulated, as disruption of PI3K-Akt signaling underlies the pathology of many diseases such as cancer and diabetes. This sophisticated regulation of PI3K-Akt signaling is due in part to the spatial and temporal compartmentalization of Akt activation and function, including in specific nanoscale domains of the plasma membrane as well as in specific intracellular membrane compartments. Here, we review the evidence for localized activation of PI3K-Akt signaling by receptor tyrosine kinases in various specific cellular compartments, as well as that of compartment-specific functions of Akt leading to control of several fundamental cellular processes. This spatial and temporal control of Akt activation and function occurs by a large number of parallel molecular mechanisms that are central to regulation of cell physiology.
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Affiliation(s)
- Michael G Sugiyama
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada.,Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON, Canada
| | - Gregory D Fairn
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON, Canada.,Department of Surgery, University of Toronto, Toronto, ON, Canada
| | - Costin N Antonescu
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada.,Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON, Canada
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15
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Functional link between plasma membrane spatiotemporal dynamics, cancer biology, and dietary membrane-altering agents. Cancer Metastasis Rev 2019; 37:519-544. [PMID: 29860560 DOI: 10.1007/s10555-018-9733-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The cell plasma membrane serves as a nexus integrating extra- and intracellular components, which together enable many of the fundamental cellular signaling processes that sustain life. In order to perform this key function, plasma membrane components assemble into well-defined domains exhibiting distinct biochemical and biophysical properties that modulate various signaling events. Dysregulation of these highly dynamic membrane domains can promote oncogenic signaling. Recently, it has been demonstrated that select membrane-targeted dietary bioactives (MTDBs) have the ability to remodel plasma membrane domains and subsequently reduce cancer risk. In this review, we focus on the importance of plasma membrane domain structural and signaling functionalities as well as how loss of membrane homeostasis can drive aberrant signaling. Additionally, we discuss the intricacies associated with the investigation of these membrane domain features and their associations with cancer biology. Lastly, we describe the current literature focusing on MTDBs, including mechanisms of chemoprevention and therapeutics in order to establish a functional link between these membrane-altering biomolecules, tuning of plasma membrane hierarchal organization, and their implications in cancer prevention.
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16
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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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17
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Fonseca MDC, França A, Florentino RM, Fonseca RC, Lima Filho ACM, Vidigal PTV, Oliveira AG, Dubuquoy L, Nathanson MH, Leite MF. Cholesterol-enriched membrane microdomains are needed for insulin signaling and proliferation in hepatic cells. Am J Physiol Gastrointest Liver Physiol 2018; 315:G80-G94. [PMID: 29471671 PMCID: PMC6109708 DOI: 10.1152/ajpgi.00008.2018] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Hepatocyte proliferation during liver regeneration is a well-coordinated process regulated by the activation of several growth factor receptors, including the insulin receptor (IR). The IR can be localized in part to cholesterol-enriched membrane microdomains, but the role of such domains in insulin-mediated events in hepatocytes is not known. We investigated whether partitioning of IRs into cholesterol-enriched membrane rafts is important for the mitogenic effects of insulin in the hepatic cells. IR and lipid rafts were labeled in HepG2 cells and primary rat hepatocytes. Membrane cholesterol was depleted in vitro with metyl-β-cyclodextrin (MβCD) and in vivo with lovastatin. Insulin-induced calcium (Ca2+) signals studies were examined in HepG2 cells and in freshly isolated rat hepatocytes as well as in whole liver in vivo by intravital confocal imaging. Liver regeneration was studied by 70% partial hepatectomy (PH), and hepatocyte proliferation was assessed by PCNA staining. A subpopulation of IR was found in membrane microdomains enriched in cholesterol. Depletion of cholesterol from plasma membrane resulted in redistribution of the IR along the cells, which was associated with impaired insulin-induced nuclear Ca2+ signals, a signaling event that regulates hepatocyte proliferation. Cholesterol depletion also led to ERK1/2 hyper-phosphorylation. Lovastatin administration to rats decreased hepatic cholesterol content, disrupted lipid rafts and decreased insulin-induced Ca2+ signaling in hepatocytes, and delayed liver regeneration after PH. Therefore, membrane cholesterol content and lipid rafts integrity showed to be important for the proliferative effects of insulin in hepatic cells. NEW & NOTEWORTHY One of insulin's actions is to stimulate liver regeneration. Here we show that a subpopulation of insulin receptors is in a specialized cholesterol-enriched region of the cell membrane and this subfraction is important for insulin's proliferative effects.
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Affiliation(s)
- Matheus de Castro Fonseca
- 1Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials, Campinas, Sao Paulo, Brazil,2Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Andressa França
- 2Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil,3Department of Molecular Medicine, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Rodrigo Machado Florentino
- 2Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Roberta Cristelli Fonseca
- 2Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil,4Center for Gastrointestinal Biology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | | | - Paula Teixeira Vieira Vidigal
- 5Department of Pathological Anatomy and Forensic Medicine, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - André Gustavo Oliveira
- 2Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil,4Center for Gastrointestinal Biology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Laurent Dubuquoy
- 6Lille Inflammation Research International Center–UMR995, INSERM, University of Lille, Lille, France
| | - Michael H. Nathanson
- 7Section of Digestive Diseases, Department of Internal Medicine, Yale University, New Haven, Connecticut
| | - M. Fátima Leite
- 2Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
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18
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Kusters YHAM, Barrett EJ. Muscle microvasculature's structural and functional specializations facilitate muscle metabolism. Am J Physiol Endocrinol Metab 2016; 310:E379-87. [PMID: 26714849 PMCID: PMC4888529 DOI: 10.1152/ajpendo.00443.2015] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 12/18/2015] [Indexed: 12/29/2022]
Abstract
We review the evolving findings from studies that examine the relationship between the structural and functional properties of skeletal muscle's vasculature and muscle metabolism. Unique aspects of the organization of the muscle microvasculature are highlighted. We discuss the role of vasomotion at the microscopic level and of flowmotion at the tissue level as modulators of perfusion distribution in muscle. We then consider in some detail how insulin and exercise each modulate muscle perfusion at both the microvascular and whole tissue level. The central role of the vascular endothelial cell in modulating both perfusion and transendothelial insulin and nutrient transport is also reviewed. The relationship between muscle metabolic insulin resistance and the vascular action of insulin in muscle continues to indicate an important role for the microvasculature as a target for insulin action and that impairing insulin's microvascular action significantly affects body glucose metabolism.
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Affiliation(s)
- Yvo H A M Kusters
- Department of Internal Medicine, Maastricht University Medical Center, Maastricht, The Netherlands; Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, The Netherlands; and
| | - Eugene J Barrett
- Department of Medicine, Pediatrics, and Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia
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19
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Imbalanced insulin action in chronic over nutrition: Clinical harm, molecular mechanisms, and a way forward. Atherosclerosis 2016; 247:225-82. [PMID: 26967715 DOI: 10.1016/j.atherosclerosis.2016.02.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 12/31/2015] [Accepted: 02/02/2016] [Indexed: 02/08/2023]
Abstract
The growing worldwide prevalence of overnutrition and underexertion threatens the gains that we have made against atherosclerotic cardiovascular disease and other maladies. Chronic overnutrition causes the atherometabolic syndrome, which is a cluster of seemingly unrelated health problems characterized by increased abdominal girth and body-mass index, high fasting and postprandial concentrations of cholesterol- and triglyceride-rich apoB-lipoproteins (C-TRLs), low plasma HDL levels, impaired regulation of plasma glucose concentrations, hypertension, and a significant risk of developing overt type 2 diabetes mellitus (T2DM). In addition, individuals with this syndrome exhibit fatty liver, hypercoagulability, sympathetic overactivity, a gradually rising set-point for body adiposity, a substantially increased risk of atherosclerotic cardiovascular morbidity and mortality, and--crucially--hyperinsulinemia. Many lines of evidence indicate that each component of the atherometabolic syndrome arises, or is worsened by, pathway-selective insulin resistance and responsiveness (SEIRR). Individuals with SEIRR require compensatory hyperinsulinemia to control plasma glucose levels. The result is overdrive of those pathways that remain insulin-responsive, particularly ERK activation and hepatic de-novo lipogenesis (DNL), while carbohydrate regulation deteriorates. The effects are easily summarized: if hyperinsulinemia does something bad in a tissue or organ, that effect remains responsive in the atherometabolic syndrome and T2DM; and if hyperinsulinemia might do something good, that effect becomes resistant. It is a deadly imbalance in insulin action. From the standpoint of human health, it is the worst possible combination of effects. In this review, we discuss the origins of the atherometabolic syndrome in our historically unprecedented environment that only recently has become full of poorly satiating calories and incessant enticements to sit. Data are examined that indicate the magnitude of daily caloric imbalance that causes obesity. We also cover key aspects of healthy, balanced insulin action in liver, endothelium, brain, and elsewhere. Recent insights into the molecular basis and pathophysiologic harm from SEIRR in these organs are discussed. Importantly, a newly discovered oxide transport chain functions as the master regulator of the balance amongst different limbs of the insulin signaling cascade. This oxide transport chain--abbreviated 'NSAPP' after its five major proteins--fails to function properly during chronic overnutrition, resulting in this harmful pattern of SEIRR. We also review the origins of widespread, chronic overnutrition. Despite its apparent complexity, one factor stands out. A sophisticated junk food industry, aided by subsidies from willing governments, has devoted years of careful effort to promote overeating through the creation of a new class of food and drink that is low- or no-cost to the consumer, convenient, savory, calorically dense, yet weakly satiating. It is past time for the rest of us to overcome these foes of good health and solve this man-made epidemic.
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20
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Ousmaal MEF, Martínez MC, Andriantsitohaina R, Chabane K, Gaceb A, Mameri S, Giaimis J, Baz A. Increased monocyte/neutrophil and pro-coagulant microparticle levels and overexpression of aortic endothelial caveolin-1β in dyslipidemic sand rat, Psammomys obesus. J Diabetes Complications 2016; 30:21-9. [PMID: 26597597 DOI: 10.1016/j.jdiacomp.2015.09.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 09/28/2015] [Accepted: 09/30/2015] [Indexed: 01/05/2023]
Abstract
AIMS To compare the effects of a high-energy diet (HED) with those of a low-energy diet (LED) on biochemical parameters, microparticle (MP) subpopulations and endothelial caveolin-1 (cav-1) protein expression in Psammomys obesus (P. obesus). METHODS After 12weeks of feeding with either the HED or LED, fasting plasma glucose and lipid parameters were measured using an enzymatic colorimetric kit while serum insulin concentration was determined with radioimmunoassay kits. MP subpopulations and cav-1 protein expression were quantified using flow cytometry and western blot analysis, respectively. RESULTS We observed that the HED caused a marked increase in lipid parameters, even in normoglycemic P. obesus. The total number of circulating MPs and the numbers of platelet-, leukocyte-, and erythrocyte-derived MPs were unaltered in the HED group. However, the HED induced increases in the numbers of monocytes/neutrophils and procoagulant MPs and a decrease in the endothelial MP levels. Cav-1β protein expression and reactive oxygen species production were increased in the vascular endothelium of HED-treated P. obesus. CONCLUSION From these findings, it is indicated that the HED exerts deleterious effects on the vascular system by increasing the monocyte/neutrophil and procoagulant MP levels, which may lead to cav-1β protein overexpression in dyslipidemic P. obesus.
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Affiliation(s)
- Mohamed El Fadel Ousmaal
- Laboratory of Biology and Organism Physiology, University of Sciences and Technology Houari Boumediene (USTHB), Algiers, Algeria; Laboratory of Biology and Animal Physiology, ENS Kouba, Algiers, Algeria.
| | - M Carmen Martínez
- INSERM U1063- Stress Oxydant et Pathologies Métaboliques, Université d'Angers, France.
| | | | - Kahina Chabane
- Laboratory of Biology and Animal Physiology, ENS Kouba, Algiers, Algeria.
| | - Abderahim Gaceb
- INSERM U1063- Stress Oxydant et Pathologies Métaboliques, Université d'Angers, France.
| | - Saâdia Mameri
- Laboratory of Anatomopathology, Mustapha Bacha Hospital, Algiers, Algeria.
| | - Jean Giaimis
- UMR Qualisud- Faculty of Pharmacy, University of Montpellier I, Montpellier, France.
| | - Ahsene Baz
- Laboratory of Biology and Animal Physiology, ENS Kouba, Algiers, Algeria.
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21
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Ariotti N, Rae J, Leneva N, Ferguson C, Loo D, Okano S, Hill MM, Walser P, Collins BM, Parton RG. Molecular Characterization of Caveolin-induced Membrane Curvature. J Biol Chem 2015; 290:24875-90. [PMID: 26304117 DOI: 10.1074/jbc.m115.644336] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Indexed: 01/07/2023] Open
Abstract
The generation of caveolae involves insertion of the cholesterol-binding integral membrane protein caveolin-1 (Cav1) into the membrane, however, the precise molecular mechanisms are as yet unknown. We have speculated that insertion of the caveolin scaffolding domain (CSD), a conserved amphipathic region implicated in interactions with signaling proteins, is crucial for caveola formation. We now define the core membrane-juxtaposed region of Cav1 and show that the oligomerization domain and CSD are protected by tight association with the membrane in both mature mammalian caveolae and a model prokaryotic system for caveola biogenesis. Cryoelectron tomography reveals the core membrane-juxtaposed domain to be sufficient to maintain oligomerization as defined by polyhedral distortion of the caveolar membrane. Through mutagenesis we demonstrate the importance of the membrane association of the oligomerization domain/CSD for defined caveola biogenesis and furthermore, highlight the functional significance of the intramembrane domain and the CSD for defined caveolin-induced membrane deformation. Finally, we define the core structural domain of Cav1, constituting only 66 amino acids and of great potential to nanoengineering applications, which is required for caveolin-induced vesicle formation in a bacterial system. These results have significant implications for understanding the role of Cav1 in caveola formation and in regulating cellular signaling events.
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Affiliation(s)
- Nicholas Ariotti
- From the University of Queensland, Institute for Molecular Bioscience, Queensland 4072, Australia
| | - James Rae
- From the University of Queensland, Institute for Molecular Bioscience, Queensland 4072, Australia
| | - Natalya Leneva
- From the University of Queensland, Institute for Molecular Bioscience, Queensland 4072, Australia
| | - Charles Ferguson
- From the University of Queensland, Institute for Molecular Bioscience, Queensland 4072, Australia
| | - Dorothy Loo
- The University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, Brisbane, Queensland,Australia, and
| | - Satomi Okano
- From the University of Queensland, Institute for Molecular Bioscience, Queensland 4072, Australia
| | - Michelle M Hill
- The University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, Brisbane, Queensland,Australia, and
| | - Piers Walser
- From the University of Queensland, Institute for Molecular Bioscience, Queensland 4072, Australia
| | - Brett M Collins
- From the University of Queensland, Institute for Molecular Bioscience, Queensland 4072, Australia
| | - Robert G Parton
- From the University of Queensland, Institute for Molecular Bioscience, Queensland 4072, Australia, the University of Queensland, Centre for Microscopy and Microanalysis, Brisbane, Queensland 4072, Australia
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22
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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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Endocytosis and Trafficking of Natriuretic Peptide Receptor-A: Potential Role of Short Sequence Motifs. MEMBRANES 2015; 5:253-87. [PMID: 26151885 PMCID: PMC4584282 DOI: 10.3390/membranes5030253] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Revised: 06/25/2015] [Accepted: 06/25/2015] [Indexed: 12/19/2022]
Abstract
The targeted endocytosis and redistribution of transmembrane receptors among membrane-bound subcellular organelles are vital for their correct signaling and physiological functions. Membrane receptors committed for internalization and trafficking pathways are sorted into coated vesicles. Cardiac hormones, atrial and brain natriuretic peptides (ANP and BNP) bind to guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) and elicit the generation of intracellular second messenger cyclic guanosine 3',5'-monophosphate (cGMP), which lowers blood pressure and incidence of heart failure. After ligand binding, the receptor is rapidly internalized, sequestrated, and redistributed into intracellular locations. Thus, NPRA is considered a dynamic cellular macromolecule that traverses different subcellular locations through its lifetime. The utilization of pharmacologic and molecular perturbants has helped in delineating the pathways of endocytosis, trafficking, down-regulation, and degradation of membrane receptors in intact cells. This review describes the investigation of the mechanisms of internalization, trafficking, and redistribution of NPRA compared with other cell surface receptors from the plasma membrane into the cell interior. The roles of different short-signal peptide sequence motifs in the internalization and trafficking of other membrane receptors have been briefly reviewed and their potential significance in the internalization and trafficking of NPRA is discussed.
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Regazzetti C, Dumas K, Lacas-Gervais S, Pastor F, Peraldi P, Bonnafous S, Dugail I, Le Lay S, Valet P, Le Marchand-Brustel Y, Tran A, Gual P, Tanti JF, Cormont M, Giorgetti-Peraldi S. Hypoxia inhibits Cavin-1 and Cavin-2 expression and down-regulates caveolae in adipocytes. Endocrinology 2015; 156:789-801. [PMID: 25521582 DOI: 10.1210/en.2014-1656] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
During obesity, a hypoxic state develops within the adipose tissue, resulting in insulin resistance. To understand the underlying mechanism, we analyzed the involvement of caveolae because they play a crucial role in the activation of insulin receptors. In the present study, we demonstrate that in 3T3-L1 adipocytes, hypoxia induces the disappearance of caveolae and inhibits the expression of Cavin-1 and Cavin-2, two proteins necessary for the formation of caveolae. In mice, hypoxia induced by the ligature of the spermatic artery results in the decrease of cavin-1 and cavin-2 expression in the epididymal adipose tissue. Down-regulation of the expression of cavins in response to hypoxia is dependent on hypoxia-inducible factor-1. Indeed, the inhibition of hypoxia-inducible factor-1 restores the expression of cavins and caveolae formation. Expression of cavins regulates insulin signaling because the silencing of cavin-1 and cavin-2 impairs insulin signaling pathway. In human, cavin-1 and cavin-2 are decreased in the sc adipose tissue of obese diabetic patients compared with lean subjects. Moreover, the expression of cavin-2 correlates negatively with the homeostatic model assessment index of insulin resistance and glycated hemoglobin level. In conclusion, we propose a new mechanism in which hypoxia inhibits cavin-1 and cavin-2 expression, resulting in the disappearance of caveolae. This leads to the inhibition of insulin signaling and the establishment of insulin resistance.
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Affiliation(s)
- Claire Regazzetti
- INSERM Unité 1065 (C.R., K.D., F.P., Y.L.M.-B., J.-F.T., M.C., S.G.-P.), C3M, Mediterranean Research Centre for Molecular Medicine, Team 7 (Cellular and Molecular Physiopathology of Obesity and Diabetes), Unité de Formation et de Recherche (UFR) Medicine (C.R., K.D., F.P., P.P., S.B., Y.L.M.-B., A.T., P.G., J.-F.T., M.C., S.G.-P.), and INSERM Unité 1065 (S.B., A.T., P.G.), C3M, Mediterranean Research Centre for Molecular Medicine, Team 8 (Hepatic Complications in Obesity),University of Nice, Sophia Antipolis F-06204 Nice, France; Centre Commun de Microscopie Appliquée (S.L.-G.), University of Nice, Sophia Antipolis, UFR Sciences, Parc Valrose, F-06108 Nice, France; Unité Mixte de Recherche Centre National de la Recherche Scientifique 7277 (P.P.), Unité Mixte de Recherche INSERM Unité 1091, UFR Medicine, F-06107 Nice, France; Centre Hospitalier Universitaire de Nice, Digestive Center (S.B., A.T.), Nice F-06202, Cedex 3, France; INSERM Unité Mixte de Recherche S872 (I.D.), Centre de Recherche des Cordeliers, Eq8, F-75006 Paris, France; INSERM Unité 1063 (S.L.L.), Stress Oxydant et Pathologies Métaboliques, Institut de Biologie en Santé, F-49933 Angers, France; and INSERM Unité Mixte de Recherche 1048 (P.V.), Institut des Maladies Métaboliques et Cardiovasculaires, Université Paul Sabatier, F-31432 Toulouse, France
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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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Palacios-Ortega S, Varela-Guruceaga M, Milagro FI, Martínez JA, de Miguel C. Expression of Caveolin 1 is enhanced by DNA demethylation during adipocyte differentiation. status of insulin signaling. PLoS One 2014; 9:e95100. [PMID: 24751908 PMCID: PMC3994010 DOI: 10.1371/journal.pone.0095100] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 03/23/2014] [Indexed: 12/14/2022] Open
Abstract
Caveolin 1 (Cav-1) is an essential constituent of adipocyte caveolae which binds the beta subunit of the insulin receptor (IR) and is implicated in the regulation of insulin signaling. We have found that, during adipocyte differentiation of 3T3-L1 cells the promoter, exon 1 and first intron of the Cav-1 gene undergo a demethylation process that is accompanied by a strong induction of Cav-1 expression, indicating that epigenetic mechanisms must have a pivotal role in this differentiation process. Furthermore, IR, PKB-Akt and Glut-4 expression are also increased during the differentiation process suggesting a coordinated regulation with Cav-1. Activation of Cav-1 protein by phosphorylation arises during the differentiation process, yet in fully mature adipocytes insulin is no longer able to significantly increase Cav-1 phosphorylation. However, these long-term differentiated cells are still able to respond adequately to insulin, increasing IR and PKB-Akt phosphorylation and glucose uptake. The activation of Cav-1 during the adipocyte differentiation process could facilitate the maintenance of insulin sensitivity by these fully mature adipocytes isolated from additional external stimuli. However, under the influence of physiological conditions associated to obesity, such as chronic inflammation and hypoxia, insulin sensitivity would finally be compromised.
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Affiliation(s)
| | | | - Fermín Ignacio Milagro
- Department of Nutrition Food Science and Physiology, University of Navarra, Pamplona, Spain
- Physiopathology of Obesity and Nutrition CIBERobn, Carlos III Health Research Institute, Madrid, Spain
| | - José Alfredo Martínez
- Department of Nutrition Food Science and Physiology, University of Navarra, Pamplona, Spain
- Physiopathology of Obesity and Nutrition CIBERobn, Carlos III Health Research Institute, Madrid, Spain
| | - Carlos de Miguel
- Department of Biochemistry and Genetics, University of Navarra, Pamplona, Spain
- Physiopathology of Obesity and Nutrition CIBERobn, Carlos III Health Research Institute, Madrid, Spain
- * E-mail:
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Genders AJ, Frison V, Abramson SR, Barrett EJ. Endothelial cells actively concentrate insulin during its transendothelial transport. Microcirculation 2014; 20:434-9. [PMID: 23350546 DOI: 10.1111/micc.12044] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 01/23/2013] [Indexed: 01/07/2023]
Abstract
OBJECTIVE We examined insulins uptake and transendothelial transport by endothelial cells in order to: (i) ascertain whether insulin accumulates within the cells to concentrations greater than in the media; (ii) compare trans endothelial insulin transport to that of inulin (using the latter as a tracer for passive transport or leaked); and; (iii) determine whether insulins transported depended on insulin action. METHODS Using 125I-insulin at physiologic concentrations we measured both the uptake and trans endothelial transport of insulin by bovine aortic endothelial cells and measured cell volume using tritiated 3-O-methylglucose. RESULTS Bovine aortic endothelial cells accumulate insulin to > five-fold above the media concentrations and the trans endothelial transport of insulin, but not inulin, is saturable and requires intact PI-3-kinase and MEK signaling. CONCLUSION The insulin receptor and downstream signaling from the receptor regulates endothelial insulin transport. Insulin is accumulated against a concentration gradient by the endothelial cell. We suggest that insulin uptake is rate limiting for insulin trans endothelial transport.
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Affiliation(s)
- Amanda J Genders
- Division of Endocrinology, Department of Medicine, University of Virginia, School of Medicine, Charlottesville, VA 22908, USA
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Amaya MJ, Oliveira AG, Guimarães ES, Casteluber MCF, Carvalho SM, Andrade LM, Pinto MCX, Mennone A, Oliveira CA, Resende RR, Menezes GB, Nathanson MH, Leite MF. The insulin receptor translocates to the nucleus to regulate cell proliferation in liver. Hepatology 2014; 59:274-83. [PMID: 23839970 PMCID: PMC3823683 DOI: 10.1002/hep.26609] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 06/24/2013] [Indexed: 12/25/2022]
Abstract
UNLABELLED Insulin's metabolic effects in the liver are widely appreciated, but insulin's ability to act as a hepatic mitogen is less well understood. Because the insulin receptor (IR) can traffic to the nucleus, and Ca(2+) signals within the nucleus regulate cell proliferation, we investigated whether insulin's mitogenic effects result from activation of Ca(2+)-signaling pathways by IRs within the nucleus. Insulin-induced increases in Ca(2+) and cell proliferation depended upon clathrin- and caveolin-dependent translocation of the IR to the nucleus, as well as upon formation of inositol 1,4,5,-trisphosphate (InsP3) in the nucleus, whereas insulin's metabolic effects did not depend on either of these events. Moreover, liver regeneration after partial hepatectomy also depended upon the formation of InsP3 in the nucleus, but not the cytosol, whereas hepatic glucose metabolism was not affected by buffering InsP3 in the nucleus. CONCLUSION These findings provide evidence that insulin's mitogenic effects are mediated by a subpopulation of IRs that traffic to the nucleus to locally activate InsP3 -dependent Ca(2+)-signaling pathways. The steps along this signaling pathway reveal a number of potential targets for therapeutic modulation of liver growth in health and disease.
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Affiliation(s)
- Maria J. Amaya
- Section of Digestive Diseases, Department of Internal Medicine, Yale University. 333 Cedar Street. PO Box 208019. New Haven-CT, 06520-8019, USA
| | - André G. Oliveira
- Department of Physiology and Biophysics, Federal University of Minas Gerais. Av. Antônio Carlos, 6627. Belo Horizonte-Minas Gerais. CEP: 31270-901, Brazil
| | - Erika S. Guimarães
- Department of Physiology and Biophysics, Federal University of Minas Gerais. Av. Antônio Carlos, 6627. Belo Horizonte-Minas Gerais. CEP: 31270-901, Brazil
| | - Marisa C. F. Casteluber
- Department of Physiology and Biophysics, Federal University of Minas Gerais. Av. Antônio Carlos, 6627. Belo Horizonte-Minas Gerais. CEP: 31270-901, Brazil
| | - Sandhra M. Carvalho
- School of Engineering, Federal University of Minas Gerais, Av. Antônio Carlos, 6627. Belo Horizonte-Minas Gerais. CEP: 31270-901, Brazil
| | - Lidia M. Andrade
- Department of Physiology and Biophysics, Federal University of Minas Gerais. Av. Antônio Carlos, 6627. Belo Horizonte-Minas Gerais. CEP: 31270-901, Brazil,René Rachou Research Center, Oswaldo Cruz Foundation. Av. Augusto de Lima, 1715. Belo Horizonte-Minas Gerais. CEP: 30190-002, Brazil
| | - Mauro C. X. Pinto
- Department of Physiology and Biophysics, Federal University of Minas Gerais. Av. Antônio Carlos, 6627. Belo Horizonte-Minas Gerais. CEP: 31270-901, Brazil
| | - Albert Mennone
- Section of Digestive Diseases, Department of Internal Medicine, Yale University. 333 Cedar Street. PO Box 208019. New Haven-CT, 06520-8019, USA
| | - Cleida A. Oliveira
- Department of Morphology, Federal University of Minas Gerais. Av. Antônio Carlos, 6627. Belo Horizonte-Minas Gerais. CEP: 31270-901, Brazil
| | - Rodrigo R. Resende
- Department of Biochemistry and Immunology, Federal University of Minas Gerais. Av. Antônio Carlos, 6627. Belo Horizonte-Minas Gerais. CEP: 31270-901, Brazil
| | - Gustavo B. Menezes
- Department of Morphology, Federal University of Minas Gerais. Av. Antônio Carlos, 6627. Belo Horizonte-Minas Gerais. CEP: 31270-901, Brazil
| | - Michael H. Nathanson
- Section of Digestive Diseases, Department of Internal Medicine, Yale University. 333 Cedar Street. PO Box 208019. New Haven-CT, 06520-8019, USA
| | - M. Fatima Leite
- Department of Physiology and Biophysics, Federal University of Minas Gerais. Av. Antônio Carlos, 6627. Belo Horizonte-Minas Gerais. CEP: 31270-901, Brazil,Howard Hughes Medical Institute
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Kapus A, Janmey P. Plasma membrane--cortical cytoskeleton interactions: a cell biology approach with biophysical considerations. Compr Physiol 2013; 3:1231-81. [PMID: 23897686 DOI: 10.1002/cphy.c120015] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
From a biophysical standpoint, the interface between the cell membrane and the cytoskeleton is an intriguing site where a "two-dimensional fluid" interacts with an exceedingly complex three-dimensional protein meshwork. The membrane is a key regulator of the cytoskeleton, which not only provides docking sites for cytoskeletal elements through transmembrane proteins, lipid binding-based, and electrostatic interactions, but also serves as the source of the signaling events and molecules that control cytoskeletal organization and remolding. Conversely, the cytoskeleton is a key determinant of the biophysical and biochemical properties of the membrane, including its shape, tension, movement, composition, as well as the mobility, partitioning, and recycling of its constituents. From a cell biological standpoint, the membrane-cytoskeleton interplay underlies--as a central executor and/or regulator--a multitude of complex processes including chemical and mechanical signal transduction, motility/migration, endo-/exo-/phagocytosis, and other forms of membrane traffic, cell-cell, and cell-matrix adhesion. The aim of this article is to provide an overview of the tight structural and functional coupling between the membrane and the cytoskeleton. As biophysical approaches, both theoretical and experimental, proved to be instrumental for our understanding of the membrane/cytoskeleton interplay, this review will "oscillate" between the cell biological phenomena and the corresponding biophysical principles and considerations. After describing the types of connections between the membrane and the cytoskeleton, we will focus on a few key physical parameters and processes (force generation, curvature, tension, and surface charge) and will discuss how these contribute to a variety of fundamental cell biological functions.
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Affiliation(s)
- András Kapus
- Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada.
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Hernandez VJ, Weng J, Ly P, Pompey S, Dong H, Mishra L, Schwarz M, Anderson RGW, Michaely P. Cavin-3 dictates the balance between ERK and Akt signaling. eLife 2013; 2:e00905. [PMID: 24069528 PMCID: PMC3780650 DOI: 10.7554/elife.00905] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2013] [Accepted: 08/14/2013] [Indexed: 12/22/2022] Open
Abstract
Cavin-3 is a tumor suppressor protein of unknown function. Using both in vivo and in vitro approaches, we show that cavin-3 dictates the balance between ERK and Akt signaling. Loss of cavin-3 increases Akt signaling at the expense of ERK, while gain of cavin-3 increases ERK signaling at the expense Akt. Cavin-3 facilitates signal transduction to ERK by anchoring caveolae to the membrane skeleton of the plasma membrane via myosin-1c. Caveolae are lipid raft specializations that contain an ERK activation module and loss of the cavin-3 linkage reduces the abundance of caveolae, thereby separating this ERK activation module from signaling receptors. Loss of cavin-3 promotes Akt signaling through suppression of EGR1 and PTEN. The in vitro consequences of the loss of cavin-3 include induction of Warburg metabolism (aerobic glycolysis), accelerated cell proliferation, and resistance to apoptosis. The in vivo consequences of cavin-3 knockout are increased lactate production and cachexia. DOI:http://dx.doi.org/10.7554/eLife.00905.001.
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Affiliation(s)
- Victor J Hernandez
- Department of Cell Biology , University of Texas Southwestern Medical Center , Dallas , United States
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Yang S, Liu X, Li X, Sun S, Sun F, Fan B, Zhao S. MicroRNA-124 reduces caveolar density by targeting caveolin-1 in porcine kidney epithelial PK15 cells. Mol Cell Biochem 2013; 384:213-9. [PMID: 24000013 DOI: 10.1007/s11010-013-1800-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Accepted: 08/23/2013] [Indexed: 01/29/2023]
Abstract
Caveolin-1 is the principal component of caveolae, and it is implicated in endocytosis, cholesterol homeostasis, signal transduction and tumorigenesis. MicroRNAs play key regulatory roles in many cellular processes. However, the molecular mechanism by which porcine caveolin-1 is regulated by microRNAs remains unclear. In the present study, we found that miR-124 could directly target caveolin-1 in porcine kidney epithelial cells (PK15). A luciferase reporter assay revealed that miR-124 directly bound to Cav1 mRNA. Ectopic expression of miR-124 decreased porcine Cav1 expression at both the mRNA and protein levels. Furthermore, we used transmission electron microscopy to count caveolae in the cytosolic space next to the membrane and we found that the overexpression of miR-124 in PK15 cells reduced the density of the caveolae. Our results suggested that miR-124 reduced caveolar density by targeting caveolin-1 in PK15 cells; therefore, miR-124 could play an important role in the caveolae-mediated endocytosis of pathogens and signal transduction.
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Affiliation(s)
- Songbai Yang
- Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education & College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China,
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Huang H, Bae C, Sachs F, Suchyna TM. Caveolae regulation of mechanosensitive channel function in myotubes. PLoS One 2013; 8:e72894. [PMID: 24023653 PMCID: PMC3758351 DOI: 10.1371/journal.pone.0072894] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 07/15/2013] [Indexed: 01/07/2023] Open
Abstract
Mutations that lead to muscular dystrophy often create deficiencies in cytoskeletal support of the muscle sarcolemma causing hyperactive mechanosensitive cation channel (MSC) activity and elevated intracellular Ca(2+). Caveolae are cholesterol-rich microdomains that form mechanically deformable invaginations of the sarcolemma. Mutations to caveolin-3, the main scaffolding protein of caveolae in muscle, cause Limbe-Girdle muscular dystrophy. Using genetic and acute chemical perturbations of developing myotubes we investigated whether caveolae are functionally linked to MSCs. MSC sensitivity was assayed using suction application to patches and probe-induced indentation during whole-cell recordings. Membrane mechanical stress in patches was monitored using patch capacitance/impedance. Cholesterol depletion disrupted caveolae and caused a large increase in MSC current. It also decreased the membrane mechanical relaxation time, likely reflecting cytoskeleton dissociation from the bilayer. Reduction of Cav3 expression with miRNA also increased MSC current and decreased patch relaxation time. In contrast Cav3 overexpression produced a small decrease in MSC currents. To acutely and specifically inhibit Cav3 interactions, we made a chimeric peptide containing the antennapedia membrane translocation domain and the Cav3 scaffolding domain (A-CSD3). A-CSD3 action was time dependent initially producing a mild Ca(2+) leak and increased MSC current, while longer exposures decreased MSC currents coinciding with increased patch stiffening. Images of GFP labeled Cav3 in patches showed that Cav3 doesn't enter the pipette, showing patch composition differed from the cell surface. However, disruption via cholesterol depletion caused Cav3 to become uniformly distributed over the sarcolemma and Cav3 appearance in the patch dome. The whole-cell indentation currents elicited under the different caveolae modifying conditions mirror the patch response supporting the role of caveolae in MSC function. These studies show that normal expression levels of Cav3 are mechanoprotective to the sarcolemma through multiple mechanisms, and Cav3 upregulation observed in some dystrophies may compensate for other mechanical deficiencies.
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Affiliation(s)
- Haixia Huang
- Capital Medical University, Department of Physiology, Beijing, China
| | - Chilman Bae
- SUNY at Buffalo, Department of Physiology and Biophysics, Buffalo, New York, United States of America
| | - Frederick Sachs
- SUNY at Buffalo, Department of Physiology and Biophysics, Buffalo, New York, United States of America
| | - Thomas M. Suchyna
- SUNY at Buffalo, Department of Physiology and Biophysics, Buffalo, New York, United States of America
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Ramalingam L, Oh E, Thurmond DC. Novel roles for insulin receptor (IR) in adipocytes and skeletal muscle cells via new and unexpected substrates. Cell Mol Life Sci 2013; 70:2815-34. [PMID: 23052216 PMCID: PMC3556358 DOI: 10.1007/s00018-012-1176-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 08/21/2012] [Accepted: 09/18/2012] [Indexed: 01/30/2023]
Abstract
The insulin signaling pathway regulates whole-body glucose homeostasis by transducing extracellular signals from the insulin receptor (IR) to downstream intracellular targets, thus coordinating a multitude of biological functions. Dysregulation of IR or its signal transduction is associated with insulin resistance, which may culminate in type 2 diabetes. Following initial stimulation of IR, insulin signaling diverges into different pathways, activating multiple substrates that have roles in various metabolic and cellular processes. The integration of multiple pathways arising from IR activation continues to expand as new IR substrates are identified and characterized. Accordingly, our review will focus on roles for IR substrates as they pertain to three primary areas: metabolism/glucose uptake, mitogenesis/growth, and aging/longevity. While IR functions in a seemingly pleiotropic manner in many cell types, through these three main roles in fat and skeletal muscle cells, IR multi-tasks to regulate whole-body glucose homeostasis to impact healthspan and lifespan.
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Affiliation(s)
- Latha Ramalingam
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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Wang H, Wang AX, Barrett EJ. Insulin-induced endothelial cell cortical actin filament remodeling: a requirement for trans-endothelial insulin transport. Mol Endocrinol 2012; 26:1327-38. [PMID: 22734037 DOI: 10.1210/me.2012-1003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Insulin's trans-endothelial transport (TET) is critical for its metabolic action on muscle and involves trafficking of insulin bound to its receptor (or at high insulin concentrations, the IGF-I receptor) via caveolae. However, whether caveolae-mediated insulin TET involves actin cytoskeleton organization is unknown. Here we address whether insulin regulates actin filament organization in bovine aortic endothelial cells (bAEC) and whether this affects insulin uptake and TET. We found that insulin induced extensive cortical actin filament remodeling within 5 min. This remodeling was inhibited not only by disruption of actin microfilament organization but also by inhibition of phosphatidylinositol 3-kinase (PI3K) or by disruption of lipid rafts using respective specific inhibitors. Knockdown of either caveolin-1 or Akt using specific small interfering RNA also eliminated the insulin-induced cortical actin filament remodeling. Blocking either actin microfilament organization or PI3K pathway signaling inhibited both insulin uptake and TET. Disruption of actin microfilament organization also reduced the caveolin-1, insulin receptor, and IGF-I receptor located at the plasma membrane. Exposing bAEC for 6 h to either TNFα or IL-6 blocked insulin-induced cortical actin remodeling. Extended exposure (24 h) also inhibited actin expression at both mRNA and protein levels. We conclude that insulin-induced cortical actin filament remodeling in bAEC is required for insulin's TET in a PI3K/Akt and plasma membrane lipid rafts/caveolae-dependent fashion, and proinflammatory cytokines TNFα and IL-6 block this process.
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Affiliation(s)
- Hong Wang
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Virginia Health System, Charlottesville, Virginia 22908, USA.
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Habegger KM, Hoffman NJ, Ridenour CM, Brozinick JT, Elmendorf JS. AMPK enhances insulin-stimulated GLUT4 regulation via lowering membrane cholesterol. Endocrinology 2012; 153:2130-41. [PMID: 22434076 PMCID: PMC3339638 DOI: 10.1210/en.2011-2099] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
AMP-activated protein kinase (AMPK) enhances glucose transporter GLUT4 regulation. AMPK also suppresses energy-consuming pathways such as cholesterol synthesis. Interestingly, recent in vitro and in vivo data suggest that excess membrane cholesterol impairs GLUT4 regulation. Therefore, this study tested whether a beneficial, GLUT4-regulatory aspect of AMPK stimulation involved cholesterol lowering. Using L6 myotubes stably expressing an exofacial myc-epitope-tagged-GLUT4, AMPK stimulation by 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside (AICAR; 45 min, 1 mm) or 2,4-dinitrophenol (DNP; 30 min, 200 μm) increased cell surface GLUT4myc labeling by approximately ≈ 25% (P < 0.05). Insulin (20 min, 100 nm) also increased GLUT4myc labeling by about 50% (P < 0.05), which was further enhanced (≈ 25%, P < 0.05) by AICAR or DNP. Consistent with AMPK-mediated suppression of cholesterol synthesis, AICAR and DNP decreased membrane cholesterol by 20-25% (P < 0.05). Whereas AMPK knockdown prevented the enhanced basal and insulin-stimulated GLUT4myc labeling by AICAR and DNP, cholesterol replenishment only blocked the AMPK-associated enhancement in insulin action. Cells cultured in a hyperinsulinemic milieu, resembling conditions in vivo that promote the progression/worsening of insulin resistance, displayed an increase in membrane cholesterol. This occurred concomitantly with a loss of cortical filamentous actin (F-actin) and defects in GLUT4 regulation by insulin. These derangements were prevented by AMPK stimulation. Examination of skeletal muscle from insulin-resistant Zucker rats revealed a similar elevation in membrane cholesterol and loss of F-actin. Lowering cholesterol to control levels restored F-actin structure and insulin sensitivity. In conclusion, these data suggest a novel aspect of GLUT4 regulation by AMPK involves membrane cholesterol lowering. Moreover, this AMPK-mediated process protected against hyperinsulinemia-induced insulin resistance.
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Affiliation(s)
- Kirk M Habegger
- Department of Cellular & Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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Stoeber M, Stoeck IK, Hänni C, Bleck CKE, Balistreri G, Helenius A. Oligomers of the ATPase EHD2 confine caveolae to the plasma membrane through association with actin. EMBO J 2012; 31:2350-64. [PMID: 22505029 PMCID: PMC3364743 DOI: 10.1038/emboj.2012.98] [Citation(s) in RCA: 122] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Accepted: 03/23/2012] [Indexed: 12/15/2022] Open
Abstract
Caveolae are plasma membrane microdomains that play important roles in signalling and endocytosis. The ATPase EHD2 shuttles on and off the static population of caveolae in an ATPase cycledependent manner and links caveolae to actin filaments confining them to the plasma membrane.
Caveolae are specialized domains present in the plasma membrane (PM) of most
mammalian cell types. They function in signalling, membrane regulation, and
endocytosis. We found that the Eps-15 homology domain-containing protein 2 (EHD2, an
ATPase) associated with the static population of PM caveolae. Recruitment to the PM
involved ATP binding, interaction with anionic lipids, and oligomerization into
large complexes (60–75S) via interaction of the EH domains with intrinsic
NPF/KPF motifs. Hydrolysis of ATP was essential for binding of EHD2 complexes to
caveolae. EHD2 was found to undergo dynamic exchange at caveolae, a process that
depended on a functional ATPase cycle. Depletion of EHD2 by siRNA or expression of a
dominant-negative mutant dramatically increased the fraction of mobile caveolar
vesicles coming from the PM. Overexpression of EHD2, in turn, caused confinement of
cholera toxin B in caveolae. The confining role of EHD2 relied on its capacity to
link caveolae to actin filaments. Thus, EHD2 likely plays a key role in adjusting
the balance between PM functions of stationary caveolae and the role of caveolae as
vesicular carriers.
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Affiliation(s)
- Miriam Stoeber
- Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
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Winter PW, Van Orden AK, Roess DA, Barisas BG. Actin-dependent clustering of insulin receptors in membrane microdomains. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:467-73. [DOI: 10.1016/j.bbamem.2011.10.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 10/05/2011] [Accepted: 10/06/2011] [Indexed: 10/16/2022]
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Wu X, Williams KJ. NOX4 pathway as a source of selective insulin resistance and responsiveness. Arterioscler Thromb Vasc Biol 2012; 32:1236-45. [PMID: 22328777 DOI: 10.1161/atvbaha.111.244525] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE Type 2 diabetes mellitus and related syndromes exhibit a deadly triad of dyslipoproteinemia, which leads to atherosclerosis; hyperglycemia, which causes microvascular disease; and hypertension. These features share a common, but unexplained, origin-namely, pathway-selective insulin resistance and responsiveness. Here, we undertook a comprehensive characterization of pathway-selective insulin resistance and responsiveness in liver and hepatocytes by examining 18 downstream targets of the insulin receptor, surveying the AKT, ERK, and NAD(P)H oxidase 4 pathways. METHODS AND RESULTS Injection of insulin into hyperphagic, obese type 2 diabetic db/db mice failed to inactivate hepatic protein tyrosine phosphatase gene family members, a crucial action of NAD(P)H oxidase 4 previously thought to be required for all signaling through AKT and ERK. Insulin-stimulated type 2 diabetic livers unexpectedly produced an unusual form of AKT that was phosphorylated at Thr308 (pT308), with only weak insulin-stimulated phosphorylation at Ser473. Remarkably, knockdown or inhibition of NAD(P)H oxidase 4 in cultured hepatocytes recapitulated the entire complicated pattern of pathway-selective insulin resistance and responsiveness seen in vivo-namely, monophosphorylated pT308-AKT, impaired insulin-stimulated pathways for lowering plasma lipids and glucose, but continued lipogenic pathways and robust ERK activation. CONCLUSIONS Functional disturbance of a single molecule, NAD(P)H oxidase 4, is sufficient to induce the key harmful features of deranged insulin signaling in type 2 diabetes mellitus, obesity, and other conditions associated with hyperinsulinemia and pathway-selective insulin resistance and responsiveness.
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Affiliation(s)
- Xiangdong Wu
- Section of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
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Habegger KM, Penque BA, Sealls W, Tackett L, Bell LN, Blue EK, Gallagher PJ, Sturek M, Alloosh MA, Steinberg HO, Considine RV, Elmendorf JS. Fat-induced membrane cholesterol accrual provokes cortical filamentous actin destabilisation and glucose transport dysfunction in skeletal muscle. Diabetologia 2012; 55:457-67. [PMID: 22002007 PMCID: PMC3245823 DOI: 10.1007/s00125-011-2334-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Accepted: 09/19/2011] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS Diminished cortical filamentous actin (F-actin) has been implicated in skeletal muscle insulin resistance, yet the mechanism(s) is unknown. Here we tested the hypothesis that changes in membrane cholesterol could be a causative factor, as organised F-actin structure emanates from cholesterol-enriched raft microdomains at the plasma membrane. METHODS Skeletal muscle samples from high-fat-fed animals and insulin-sensitive and insulin-resistant human participants were evaluated. The study also used L6 myotubes to directly determine the impact of fatty acids (FAs) on membrane/cytoskeletal variables and insulin action. RESULTS High-fat-fed insulin-resistant animals displayed elevated levels of membrane cholesterol and reduced F-actin structure compared with normal chow-fed animals. Moreover, human muscle biopsies revealed an inverse correlation between membrane cholesterol and whole-body glucose disposal. Palmitate-induced insulin-resistant myotubes displayed membrane cholesterol accrual and F-actin loss. Cholesterol lowering protected against the palmitate-induced defects, whereas characteristically measured defects in insulin signalling were not corrected. Conversely, cholesterol loading of L6 myotube membranes provoked a palmitate-like cytoskeletal/GLUT4 derangement. Mechanistically, we observed a palmitate-induced increase in O-linked glycosylation, an end-product of the hexosamine biosynthesis pathway (HBP). Consistent with HBP activity affecting the transcription of various genes, we observed an increase in Hmgcr, a gene that encodes 3-hydroxy-3-methyl-glutaryl coenzyme A reductase, the rate-limiting enzyme in cholesterol synthesis. In line with increased HBP activity transcriptionally provoking a membrane cholesterol-based insulin-resistant state, HBP inhibition attenuated Hmgcr expression and prevented membrane cholesterol accrual, F-actin loss and GLUT4/glucose transport dysfunction. CONCLUSIONS/INTERPRETATION Our results suggest a novel cholesterolgenic-based mechanism of FA-induced membrane/cytoskeletal disorder and insulin resistance.
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Affiliation(s)
- K. M. Habegger
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Membrane Biosciences, Indianapolis, IN USA
| | - B. A. Penque
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Membrane Biosciences, Indianapolis, IN USA
| | - W. Sealls
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Membrane Biosciences, Indianapolis, IN USA
- Indiana University School of Medicine Center for Vascular Biology and Medicine, Indianapolis, IN USA
| | - L. Tackett
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
| | - L. N. Bell
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Department of Medicine, Division of Endocrinology and Metabolism, Indiana University School of Medicine, Indianapolis, IN USA
| | - E. K. Blue
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
| | - P. J. Gallagher
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
| | - M. Sturek
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Vascular Biology and Medicine, Indianapolis, IN USA
| | - M. A. Alloosh
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Vascular Biology and Medicine, Indianapolis, IN USA
| | | | - R. V. Considine
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Department of Medicine, Division of Endocrinology and Metabolism, Indiana University School of Medicine, Indianapolis, IN USA
| | - J. S. Elmendorf
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, VanNuys Medical Science Building Rm 308A, 635 Barnhill Drive, Indianapolis, IN 46202-5120 USA
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN USA
- Indiana University School of Medicine Center for Diabetes Research, Indianapolis, IN USA
- Indiana University School of Medicine Center for Membrane Biosciences, Indianapolis, IN USA
- Indiana University School of Medicine Center for Vascular Biology and Medicine, Indianapolis, IN USA
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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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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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Molecular network pathways and functional analysis of tumor signatures associated with development of resistance to viral gene therapy. Cancer Gene Ther 2011; 19:38-48. [PMID: 22015641 DOI: 10.1038/cgt.2011.64] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Replication-competent attenuated herpes simplex viruses have proven effective in killing many cancer cell lines. However, determinants of resistance to oncolytic therapy are mostly unknown. We developed viral therapy-resistant cells and examined changes in gene-expression pattern compared with therapy-sensitive parental cells. Colon cancer cell line HT29 and hepatoma cell line PLC5 were exposed to increasing concentrations of virus G207. Therapy-resistant cells were isolated and grown in vitro. Tumorigenicity was confirmed by ability of cell lines to form tumors in mice. Human Genome U133A complementary DNA microarray chips were used to determine gene-expression patterns, which were analyzed in the context of molecular network interactions, pathways and gene ontology. In parental cell lines, 90-100% of cells were killed by day 7 at 1.0 multiplicity of infection. In resistant cell lines, cytotoxicity assay confirmed 200- to 400-fold resistance. Microarray analysis confirmed changes in gene expressions associated with resistance: cell surface proteins affecting viral attachment and entry, cellular proteins affecting nucleotide pools and proteins altering apoptotic pathways. These changes would decrease viral infection and replication. Our study identifies gene-expression signatures associated with resistance to oncolytic viral therapy. These data provide potential targets to overcome resistance, and suggest that molecular assays may be useful in selecting patients for trial with this novel treatment.
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Deblon N, Veyrat-Durebex C, Bourgoin L, Caillon A, Bussier AL, Petrosino S, Piscitelli F, Legros JJ, Geenen V, Foti M, Wahli W, Di Marzo V, Rohner-Jeanrenaud F. Mechanisms of the anti-obesity effects of oxytocin in diet-induced obese rats. PLoS One 2011; 6:e25565. [PMID: 21980491 PMCID: PMC3181274 DOI: 10.1371/journal.pone.0025565] [Citation(s) in RCA: 183] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Accepted: 09/06/2011] [Indexed: 12/18/2022] Open
Abstract
Apart from its role during labor and lactation, oxytocin is involved in several other functions. Interestingly, oxytocin- and oxytocin receptor-deficient mice develop late-onset obesity with normal food intake, suggesting that the hormone might exert a series of beneficial metabolic effects. This was recently confirmed by data showing that central oxytocin infusion causes weight loss in diet-induced obese mice. The aim of the present study was to unravel the mechanisms underlying such beneficial effects of oxytocin. Chronic central oxytocin infusion was carried out in high fat diet-induced obese rats. Its impact on body weight, lipid metabolism and insulin sensitivity was determined. We observed a dose-dependent decrease in body weight gain, increased adipose tissue lipolysis and fatty acid β-oxidation, as well as reduced glucose intolerance and insulin resistance. The additional observation that plasma oxytocin levels increased upon central infusion suggested that the hormone might affect adipose tissue metabolism by direct action. This was demonstrated using in vitro, ex vivo, as well as in vivo experiments. With regard to its mechanism of action in adipose tissue, oxytocin increased the expression of stearoyl-coenzyme A desaturase 1, as well as the tissue content of the phospholipid precursor, N-oleoyl-phosphatidylethanolamine, the biosynthetic precursor of the oleic acid-derived PPAR-alpha activator, oleoylethanolamide. Because PPAR-alpha regulates fatty acid β-oxidation, we hypothesized that this transcription factor might mediate the oxytocin effects. This was substantiated by the observation that, in contrast to its effects in wild-type mice, oxytocin infusion failed to induce weight loss and fat oxidation in PPAR-alpha-deficient animals. Altogether, these results suggest that oxytocin administration could represent a promising therapeutic approach for the treatment of human obesity and type 2 diabetes.
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Affiliation(s)
- Nicolas Deblon
- Division of Endocrinology, Diabetology and Nutrition, Department of Internal Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Christelle Veyrat-Durebex
- Division of Endocrinology, Diabetology and Nutrition, Department of Internal Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Lucie Bourgoin
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Aurélie Caillon
- Division of Endocrinology, Diabetology and Nutrition, Department of Internal Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Anne-Lise Bussier
- Division of Endocrinology, Diabetology and Nutrition, Department of Internal Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Stefania Petrosino
- Endocannabinoid Research Group, Institute of Biomolecular Chemistry, CNR, Naples, Italy
| | - Fabiana Piscitelli
- Endocannabinoid Research Group, Institute of Biomolecular Chemistry, CNR, Naples, Italy
| | - Jean-Jacques Legros
- Centre Hospitalier Régional de la Citadelle, University of Liege, Liege, Belgium
| | - Vincent Geenen
- Centre of Immunology, University of Liege, CHU B-23, Liege, Belgium
| | - Michelangelo Foti
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Walter Wahli
- Center for Integrative Genomics, National Research Center Frontiers in Genetics, University of Lausanne, Lausanne, Switzerland
| | - Vincenzo Di Marzo
- Endocannabinoid Research Group, Institute of Biomolecular Chemistry, CNR, Naples, Italy
| | - Françoise Rohner-Jeanrenaud
- Division of Endocrinology, Diabetology and Nutrition, Department of Internal Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- * E-mail:
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Barrett EJ, Wang H, Upchurch CT, Liu Z. Insulin regulates its own delivery to skeletal muscle by feed-forward actions on the vasculature. Am J Physiol Endocrinol Metab 2011; 301:E252-63. [PMID: 21610226 PMCID: PMC3154531 DOI: 10.1152/ajpendo.00186.2011] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Insulin, at physiological concentrations, regulates the volume of microvasculature perfused within skeletal and cardiac muscle. It can also, by relaxing the larger resistance vessels, increase total muscle blood flow. Both of these effects require endothelial cell nitric oxide generation and smooth muscle cell relaxation, and each could increase delivery of insulin and nutrients to muscle. The capillary microvasculature possesses the greatest endothelial surface area of the body. Yet, whether insulin acts on the capillary endothelial cell is not known. Here, we review insulin's actions at each of three levels of the arterial vasculature as well as recent data suggesting that insulin can regulate a vesicular transport system within the endothelial cell. This latter action, if it occurs at the capillary level, could enhance insulin delivery to muscle interstitium and thereby complement insulin's actions on arteriolar endothelium to increase insulin delivery. We also review work that suggests that this action of insulin on vesicle transport depends on endothelial cell nitric oxide generation and that insulin's ability to regulate this vesicular transport system is impaired by inflammatory cytokines that provoke insulin resistance.
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Affiliation(s)
- Eugene J Barrett
- Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA.
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Morcavallo A, Gaspari M, Pandini G, Palummo A, Cuda G, Larsen MR, Vigneri R, Belfiore A. Research resource: New and diverse substrates for the insulin receptor isoform A revealed by quantitative proteomics after stimulation with IGF-II or insulin. Mol Endocrinol 2011; 25:1456-68. [PMID: 21680660 DOI: 10.1210/me.2010-0484] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The isoform A of the insulin receptor (IR) (IR-A) is a bifunctional receptor, because it binds both insulin and IGF-II. IR-A activation by IGF-II plays a role in development, but its physiological role in adults is unknown. IGF-II signaling through IR-A is deregulated in cancer and favors tumor progression. We hypothesized that IGF-II binding to the IR-A elicits a unique signaling pathway. In order to obtain an unbiased evaluation of IR-A substrates differentially involved after IGF-II and insulin stimulation, we performed quantitative proteomics of IR-A substrates recruited to tyrosine-phosphorylated protein complexes using stable isotope labeling with amino acids in cell culture in combination with antiphosphotyrosine antibody pull down and mass spectrometry. Using cells expressing only the human IR-A and lacking the IGF-I receptor, we identified 38 IR-A substrates. Only 10 were known IR mediators, whereas 28 substrates were not previously related to IR signaling. Eleven substrates were recruited by stimulation with both ligands: two equally recruited by IGF-II and insulin, three more strongly recruited by IGF-II, and six more strongly recruited by insulin. Moreover, 14 substrates were recruited solely by IGF-II and 13 solely by insulin stimulation. Interestingly, discoidin domain receptors, involved in cell migration and tumor metastasis, and ephrin receptor B4, involved in bidirectional signaling upon cell-cell contact, were predominantly activated by IGF-II. These findings indicate that IR-A activation by IGF-II elicits a unique signaling pathway that may play a distinct role in physiology and in disease.
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Affiliation(s)
- Alaide Morcavallo
- Department of Clinical and Experimental Medicine, University Magna Graecia of Catanzaro, Catanzaro, Italy
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Hoffman NJ, Elmendorf JS. Signaling, cytoskeletal and membrane mechanisms regulating GLUT4 exocytosis. Trends Endocrinol Metab 2011; 22:110-6. [PMID: 21216617 PMCID: PMC3049829 DOI: 10.1016/j.tem.2010.12.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 12/03/2010] [Accepted: 12/06/2010] [Indexed: 10/25/2022]
Abstract
Solving how insulin regulates glucose transport into skeletal muscle and adipose tissue remains a fundamental challenge in biology and a significant issue in medicine. A central feature of this process is the coordinated accumulation of the glucose transporter GLUT4 into the plasma membrane. New signaling and cytoskeletal mechanisms of insulin-stimulated GLUT4 exocytosis are of emerging interest, particularly those at or just beneath the plasma membrane. This review examines signals that functionally engage GLUT4 exocytosis, considers cytoskeletal regulation of the stimulated GLUT4 itinerary, and appraises the involvement of plasma membrane parameters in GLUT4 control. We also explore how these newly-defined signaling, cytoskeletal and membrane mechanisms could be of therapeutic interest in the treatment and/or prevention of GLUT4 dysregulation in disease.
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Affiliation(s)
- Nolan J Hoffman
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Centers for Diabetes Research, Membrane Biosciences, and Vascular Biology and Medicine, VanNuys Medical Science Building Room 308A, Indianapolis, IN 46202, USA
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Pandey KN. Small peptide recognition sequence for intracellular sorting. Curr Opin Biotechnol 2011; 21:611-20. [PMID: 20817434 DOI: 10.1016/j.copbio.2010.08.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 08/10/2010] [Accepted: 08/11/2010] [Indexed: 02/05/2023]
Abstract
Increasing evidence indicate that complex arrays of short signals and recognition peptide sequence ensure accurate trafficking and distribution of transmembrane receptors and/or proteins and their ligands into intracellular compartments. Internalization and subsequent trafficking of cell-surface receptors into the cell interior is mediated by specific short-sequence peptide signals within the cytoplasmic domains of these receptor proteins. The short signals usually consist of small linear amino acid sequences, which are recognized by adaptor coat proteins along the endocytic and sorting pathways. In recent years, much has been learned about the function and mechanisms of endocytic pathways responsible for the trafficking and molecular sorting of membrane receptors and their ligands into intracellular compartments, however, the significance and scope of the short-sequence motifs in these cellular events is not well understood. Here a particular emphasis has been given to the functions of short-sequence signal motifs responsible for the itinerary and destination of membrane receptors and proteins moving into subcellular compartments.
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Affiliation(s)
- Kailash N Pandey
- Department of Physiology, Tulane University Health Sciences Center, School of Medicine, New Orleans, LA 70112, USA.
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Fiset A, Xu E, Bergeron S, Marette A, Pelletier G, Siminovitch KA, Olivier M, Beauchemin N, Faure RL. Compartmentalized CDK2 is connected with SHP-1 and β-catenin and regulates insulin internalization. Cell Signal 2011; 23:911-9. [PMID: 21262353 DOI: 10.1016/j.cellsig.2011.01.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 01/14/2011] [Indexed: 12/31/2022]
Abstract
The cyclin-dependant kinase Cdk2 is compartmentalized in endosomes but its role is poorly understood. Here we show that Cdk2 present in hepatic endosome fractions is strictly located in a Triton X-100-resistant environment. The endosomal Cdk2 was found to be associated with the protein tyrosine phosphatase SHP-1, a regulator of insulin clearance, and the actin anchor β-catenin, a known substrate for both Cdk2 and SHP-1. In the plasma membranes and endosome fractions, β-catenin is associated with CEACAM1, also known as regulator of insulin clearance. We show that β-catenin, not CEACAM1, is a substrate for Cdk2. Partial down-modulation of Cdk2 in HEK293 cells increased the rate of insulin internalization. These findings reveal that Cdk2 functions, at least in part, via a Cdk2/SHP-1/β-catenin/CEACAM1 axis, and show for the first time that Cdk2 has the capacity to regulate insulin internalization.
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Affiliation(s)
- Annie Fiset
- Department of Pediatrics, CHUL-CRCHUQ, Quebec, PQ, G1V 4G2, Canada
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Abstract
As insulin's movement from plasma to muscle interstitium is rate limiting for its metabolic action, defining the regulation of this movement is critical. Here, we address whether caveolin-1 is required for the first step of insulin's transendothelial transport, its uptake by vascular endothelial cells (ECs), and whether IL-6 and TNFα affect insulin uptake or caveolin-1 expression. Uptake of FITC-labeled insulin was measured using confocal microscopy in control bovine aortic ECs (bAECs), in bAECs in which caveolin-1 was either knocked down or overexpressed, in murine ECs from caveolin-1(-/-) mice and in bAECs exposed to inflammatory cytokines. Knockdown of caveolin-1 expression in bAECs using specific caveolin-1 siRNA reduced caveolin-1 mRNA and protein expression by ∼ 70%, and reduced FITC-insulin uptake by 67% (P < 0.05 for each). Over-expression of caveolin-1 increased insulin uptake (P < 0.05). Caveolin-1-null mouse aortic ECs did not take up insulin and re-expression of caveolin-1 by transfecting these cells with FLAG-tagged caveolin-1 DNA rescued FITC-insulin uptake. Knockdown of caveolin-1 significantly reduced both insulin receptor protein level and insulin-stimulated Akt1 phosphorylation. Knockdown of caveolin-1 also inhibited insulin-induced caveolin-1 and IGF-1 receptor translocation to the plasma membrane. Compared with controls, IL-6 or TNFα (20 ng/ml for 24 h) inhibited FITC-insulin uptake as well as the expression of caveolin-1 mRNA and protein (P < 0.05 for each). IL-6 or TNFα also significantly reduced plasma membrane-associated caveolin-1. Thus, we conclude that insulin uptake by ECs requires expression of caveolin-1 supporting a role for caveolae mediating insulin uptake. Proinflammatory cytokines may inhibit insulin uptake, at least in part, by inhibiting caveolin-1 expression.
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Affiliation(s)
- Hong Wang
- Division of Endocrinology and Metablism, Department of Internal Medicine, University of Virginia Health System, P.O. Box 801410, 450 Ray C. Hunt Dr., Charlottesville, VA 22908, USA.
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