1
|
Yue T, Guo Y, Qi X, Zheng W, Zhang H, Wang B, Liu K, Zhou B, Zeng X, Ouzhuluobu, He Y, Su B. Sex-biased regulatory changes in the placenta of native highlanders contribute to adaptive fetal development. eLife 2024; 12:RP89004. [PMID: 38869160 PMCID: PMC11175615 DOI: 10.7554/elife.89004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2024] Open
Abstract
Compared with lowlander migrants, native Tibetans have a higher reproductive success at high altitude though the underlying mechanism remains unclear. Here, we compared the transcriptome and histology of full-term placentas between native Tibetans and Han migrants. We found that the placental trophoblast shows the largest expression divergence between Tibetans and Han, and Tibetans show decreased immune response and endoplasmic reticulum stress. Remarkably, we detected a sex-biased expression divergence, where the male-infant placentas show a greater between-population difference than the female-infant placentas. The umbilical cord plays a key role in the sex-biased expression divergence, which is associated with the higher birth weight of the male newborns of Tibetans. We also identified adaptive histological changes in the male-infant placentas of Tibetans, including larger umbilical artery wall and umbilical artery intima and media, and fewer syncytial knots. These findings provide valuable insights into the sex-biased adaptation of human populations, with significant implications for medical and genetic studies of human reproduction.
Collapse
Affiliation(s)
- Tian Yue
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of SciencesKunmingChina
- Kunming College of Life Science, University of Chinese Academy of SciencesBeijingChina
| | - Yongbo Guo
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of SciencesKunmingChina
- Kunming College of Life Science, University of Chinese Academy of SciencesBeijingChina
| | - Xuebin Qi
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of SciencesKunmingChina
- Fukang Obstetrics, Gynecology and Children Branch Hospital, Tibetan Fukang HospitalKunmingChina
- State Key Laboratory of Primate Biomedical Research, Institute of Primate Translational Medicine, Kunming University of Science and TechnologyKunmingChina
| | - Wangshan Zheng
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of SciencesKunmingChina
| | - Hui Zhang
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of SciencesKunmingChina
- State Key Laboratory of Primate Biomedical Research, Institute of Primate Translational Medicine, Kunming University of Science and TechnologyKunmingChina
| | - Bin Wang
- Fukang Obstetrics, Gynecology and Children Branch Hospital, Tibetan Fukang HospitalKunmingChina
| | - Kai Liu
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of SciencesKunmingChina
| | - Bin Zhou
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of SciencesKunmingChina
- Kunming College of Life Science, University of Chinese Academy of SciencesBeijingChina
| | - Xuerui Zeng
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of SciencesKunmingChina
- Kunming College of Life Science, University of Chinese Academy of SciencesBeijingChina
| | - Ouzhuluobu
- Fukang Obstetrics, Gynecology and Children Branch Hospital, Tibetan Fukang HospitalKunmingChina
| | - Yaoxi He
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of SciencesKunmingChina
| | - Bing Su
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of SciencesKunmingChina
- Center for Excellence in Animal Evolution and Genetics, Chinese Academy of SciencesKunmingChina
| |
Collapse
|
2
|
Stefani I, Iwaszkiewicz J, Fasshauer D. Exploring the conformational changes of the Munc18-1/syntaxin 1a complex. Protein Sci 2023; 33:e4870. [PMID: 38109275 PMCID: PMC10895456 DOI: 10.1002/pro.4870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 11/30/2023] [Accepted: 12/07/2023] [Indexed: 12/20/2023]
Abstract
Neurotransmitters are released from synaptic vesicles, the membrane of which fuses with the plasma membrane upon calcium influx. This membrane fusion reaction is driven by the formation of a tight complex comprising the plasma membrane N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins syntaxin-1a and SNAP-25 with the vesicle SNARE protein synaptobrevin. The neuronal protein Munc18-1 forms a stable complex with syntaxin-1a. Biochemically, syntaxin-1a cannot escape the tight grip of Munc18-1, so formation of the SNARE complex is inhibited. However, Munc18-1 is essential for the release of neurotransmitters in vivo. It has therefore been assumed that Munc18-1 makes the bound syntaxin-1a available for SNARE complex formation. Exactly how this occurs is still unclear, but it is assumed that structural rearrangements occur. Here, we used a series of mutations to specifically weaken the complex at different positions in order to induce these rearrangements biochemically. Our approach was guided through sequence and structural analysis and supported by molecular dynamics simulations. Subsequently, we created a homology model showing the complex in an altered conformation. This conformation presumably represents a more open arrangement of syntaxin-1a that permits the formation of a SNARE complex to be initiated while still bound to Munc18-1. In the future, research should investigate how this central reaction for neuronal communication is controlled by other proteins.
Collapse
Affiliation(s)
- Ioanna Stefani
- Department of Computational BiologyUniversity of LausanneLausanneSwitzerland
| | | | - Dirk Fasshauer
- Department of Computational BiologyUniversity of LausanneLausanneSwitzerland
| |
Collapse
|
3
|
Boeglin M, Leyva-Díaz E, Hobert O. Expression and function of Caenorhabditis elegans UNCP-18, a paralog of the SM protein UNC-18. Genetics 2023; 225:iyad180. [PMID: 37793339 PMCID: PMC10697816 DOI: 10.1093/genetics/iyad180] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/01/2023] [Accepted: 09/26/2023] [Indexed: 10/06/2023] Open
Abstract
Sec1/Munc18 (SM) proteins are important regulators of SNARE complex assembly during exocytosis throughout all major animal tissue types. However, expression of a founding member of the SM family, UNC-18, is mostly restricted to the nervous system of the nematode Caenorhabditis elegans, where it is important for synaptic transmission. Moreover, unc-18 null mutants do not display the lethality phenotype associated with (a) loss of all Drosophila and mouse orthologs of unc-18 and (b) with complete elimination of synaptic transmission in C. elegans. We investigated whether a previously uncharacterized unc-18 paralog, which we named uncp-18, may be able to explain the restricted expression and limited phenotypes of unc-18 null mutants. A reporter allele shows ubiquitous expression of uncp-18. Analysis of uncp-18 null mutants, unc-18 and uncp-18 double null mutants, as well as overexpression of uncp-18 in an unc-18 null mutant background, shows that these 2 genes can functionally compensate for one another and are redundantly required for embryonic viability. Our results indicate that the synaptic transmission defects of unc-18 null mutants cannot necessarily be interpreted as constituting a null phenotype for SM protein function at the synapse.
Collapse
Affiliation(s)
- Marion Boeglin
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, NewYork, NY 10027, USA
- Department of Development and Stem Cells, IGBMC, CNRS UMR 7104/INSERM U1258, Université de Strasbourg, Strasbourg 67081, France
| | - Eduardo Leyva-Díaz
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, NewYork, NY 10027, USA
| | - Oliver Hobert
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, NewYork, NY 10027, USA
| |
Collapse
|
4
|
Hwang J, Thurmond DC. Exocytosis Proteins: Typical and Atypical Mechanisms of Action in Skeletal Muscle. Front Endocrinol (Lausanne) 2022; 13:915509. [PMID: 35774142 PMCID: PMC9238359 DOI: 10.3389/fendo.2022.915509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 05/11/2022] [Indexed: 11/18/2022] Open
Abstract
Insulin-stimulated glucose uptake in skeletal muscle is of fundamental importance to prevent postprandial hyperglycemia, and long-term deficits in insulin-stimulated glucose uptake underlie insulin resistance and type 2 diabetes. Skeletal muscle is responsible for ~80% of the peripheral glucose uptake from circulation via the insulin-responsive glucose transporter GLUT4. GLUT4 is mainly sequestered in intracellular GLUT4 storage vesicles in the basal state. In response to insulin, the GLUT4 storage vesicles rapidly translocate to the plasma membrane, where they undergo vesicle docking, priming, and fusion via the high-affinity interactions among the soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) exocytosis proteins and their regulators. Numerous studies have elucidated that GLUT4 translocation is defective in insulin resistance and type 2 diabetes. Emerging evidence also links defects in several SNAREs and SNARE regulatory proteins to insulin resistance and type 2 diabetes in rodents and humans. Therefore, we highlight the latest research on the role of SNAREs and their regulatory proteins in insulin-stimulated GLUT4 translocation in skeletal muscle. Subsequently, we discuss the novel emerging role of SNARE proteins as interaction partners in pathways not typically thought to involve SNAREs and how these atypical functions reveal novel therapeutic targets for combating peripheral insulin resistance and diabetes.
Collapse
Affiliation(s)
| | - Debbie C. Thurmond
- Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes and Metabolism Research Institute, Beckman Research Institute at City of Hope, Duarte, CA, United States
| |
Collapse
|
5
|
Fazakerley DJ, Koumanov F, Holman GD. GLUT4 On the move. Biochem J 2022; 479:445-462. [PMID: 35147164 PMCID: PMC8883492 DOI: 10.1042/bcj20210073] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 01/11/2022] [Accepted: 01/14/2022] [Indexed: 12/16/2022]
Abstract
Insulin rapidly stimulates GLUT4 translocation and glucose transport in fat and muscle cells. Signals from the occupied insulin receptor are translated into downstream signalling changes in serine/threonine kinases within timescales of seconds, and this is followed by delivery and accumulation of the glucose transporter GLUT4 at the plasma membrane. Kinetic studies have led to realisation that there are distinct phases of this stimulation by insulin. There is a rapid initial burst of GLUT4 delivered to the cell surface from a subcellular reservoir compartment and this is followed by a steady-state level of continuing stimulation in which GLUT4 recycles through a large itinerary of subcellular locations. Here, we provide an overview of the phases of insulin stimulation of GLUT4 translocation and the molecules that are currently considered to activate these trafficking steps. Furthermore, we suggest how use of new experimental approaches together with phospho-proteomic data may help to further identify mechanisms for activation of these trafficking processes.
Collapse
Affiliation(s)
- Daniel J Fazakerley
- Metabolic Research Laboratories, Wellcome-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, U.K
| | - Francoise Koumanov
- Department for Health, Centre for Nutrition, Exercise, and Metabolism, University of Bath, Bath, Somerset BA2 7AY, U.K
| | - Geoffrey D Holman
- Department of Biology and Biochemistry, University of Bath, Bath, Somerset BA2 7AY, U.K
| |
Collapse
|
6
|
Black HL, Livingstone R, Mastick CC, Al Tobi M, Taylor H, Geiser A, Stirrat L, Kioumourtzoglou D, Petrie JR, Boyle JG, Bryant NJ, Gould GW. Knockout of Syntaxin-4 in 3T3-L1 adipocytes reveals new insight into GLUT4 trafficking and adiponectin secretion. J Cell Sci 2021; 135:273617. [PMID: 34859814 PMCID: PMC8767277 DOI: 10.1242/jcs.258375] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 11/18/2021] [Indexed: 11/20/2022] Open
Abstract
Adipocytes are key to metabolic regulation, exhibiting insulin-stimulated glucose transport that is underpinned by the insulin-stimulated delivery of glucose transporter type 4 (SLC2A4, also known and hereafter referred to as GLUT4)-containing vesicles to the plasma membrane where they dock and fuse, and increase cell surface GLUT4 levels. Adipocytokines, such as adiponectin, are secreted via a similar mechanism. We used genome editing to knock out syntaxin-4, a protein reported to mediate fusion between GLUT4-containing vesicles and the plasma membrane in 3T3-L1 adipocytes. Syntaxin-4 knockout reduced insulin-stimulated glucose transport and adiponectin secretion by ∼50% and reduced GLUT4 levels. Ectopic expression of haemagglutinin (HA)-tagged GLUT4 conjugated to GFP showed that syntaxin-4-knockout cells retain significant GLUT4 translocation capacity, demonstrating that syntaxin-4 is dispensable for insulin-stimulated GLUT4 translocation. Analysis of recycling kinetics revealed only a modest reduction in the exocytic rate of GLUT4 in knockout cells, and little effect on endocytosis. These analyses demonstrate that syntaxin-4 is not always rate limiting for GLUT4 delivery to the cell surface. In sum, we show that syntaxin-4 knockout results in reduced insulin-stimulated glucose transport, depletion of cellular GLUT4 levels and inhibition of adiponectin secretion but has only modest effects on the translocation capacity of the cells. This article has an associated First Person interview with Hannah L. Black and Rachel Livingstone, joint first authors of the paper. Summary: Syntaxin-4 knockout reduces insulin-stimulated glucose transport, depletes levels of cellular GLUT4 and inhibits secretion of adiponectin but only modestly affects the translocation capacity of the cells.
Collapse
Affiliation(s)
- Hannah L Black
- Department of Biology and York Biomedical Research Institute, University of York. Heslington, York, YO10 5DD, UK
| | - Rachel Livingstone
- Henry Welcome Laboratory for Cell Biology, Institute for Molecular, Cellular and Systems Biology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | - Cynthia C Mastick
- Henry Welcome Laboratory for Cell Biology, Institute for Molecular, Cellular and Systems Biology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.,Department of Biology, University of Nevada Reno, 1664 N. Virginia Street, Reno, NV 89557, USA
| | - Mohammed Al Tobi
- Henry Welcome Laboratory for Cell Biology, Institute for Molecular, Cellular and Systems Biology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | - Holly Taylor
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
| | - Angéline Geiser
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
| | - Laura Stirrat
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
| | - Dimitrios Kioumourtzoglou
- Department of Biology and York Biomedical Research Institute, University of York. Heslington, York, YO10 5DD, UK
| | - John R Petrie
- Institute of Cardiovascular and Medical Sciences, University of Glasgow. Glasgow G12 8QQ, UK
| | - James G Boyle
- Institute of Cardiovascular and Medical Sciences, University of Glasgow. Glasgow G12 8QQ, UK.,School of Medicine, Dentistry and Nursing, University of Glasgow. Glasgow G12 8QQ, UK
| | - Nia J Bryant
- Department of Biology and York Biomedical Research Institute, University of York. Heslington, York, YO10 5DD, UK
| | - Gwyn W Gould
- Strathclyde Institute for Pharmacy and Biomedical Sciences, 161 Cathedral Street, University of Strathclyde, Glasgow G4 0RE, UK
| |
Collapse
|
7
|
Sauvola CW, Littleton JT. SNARE Regulatory Proteins in Synaptic Vesicle Fusion and Recycling. Front Mol Neurosci 2021; 14:733138. [PMID: 34421538 PMCID: PMC8377282 DOI: 10.3389/fnmol.2021.733138] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 07/20/2021] [Indexed: 01/01/2023] Open
Abstract
Membrane fusion is a universal feature of eukaryotic protein trafficking and is mediated by the soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) family. SNARE proteins embedded in opposing membranes spontaneously assemble to drive membrane fusion and cargo exchange in vitro. Evolution has generated a diverse complement of SNARE regulatory proteins (SRPs) that ensure membrane fusion occurs at the right time and place in vivo. While a core set of SNAREs and SRPs are common to all eukaryotic cells, a specialized set of SRPs within neurons confer additional regulation to synaptic vesicle (SV) fusion. Neuronal communication is characterized by precise spatial and temporal control of SNARE dynamics within presynaptic subdomains specialized for neurotransmitter release. Action potential-elicited Ca2+ influx at these release sites triggers zippering of SNAREs embedded in the SV and plasma membrane to drive bilayer fusion and release of neurotransmitters that activate downstream targets. Here we discuss current models for how SRPs regulate SNARE dynamics and presynaptic output, emphasizing invertebrate genetic findings that advanced our understanding of SRP regulation of SV cycling.
Collapse
Affiliation(s)
- Chad W Sauvola
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
| |
Collapse
|
8
|
Cardenas EI, Gonzalez R, Breaux K, Da Q, Gutierrez BA, Ramos MA, Cardenas RA, Burns AR, Rumbaut RE, Adachi R. Munc18-2, but not Munc18-1 or Munc18-3, regulates platelet exocytosis, hemostasis, and thrombosis. J Biol Chem 2019; 294:4784-4792. [PMID: 30696774 DOI: 10.1074/jbc.ra118.006922] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/24/2019] [Indexed: 12/17/2022] Open
Abstract
Platelet degranulation, a form of regulated exocytosis, is crucial for hemostasis and thrombosis. Exocytosis in platelets is mediated by SNARE proteins, and in most mammalian cells this process is controlled by Munc18 (mammalian homolog of Caenorhabditis elegans uncoordinated gene 18) proteins. Platelets express all Munc18 paralogs (Munc18-1, -2, and -3), but their roles in platelet secretion and function have not been fully characterized. Using Munc18-1, -2, and -3 conditional knockout mice, here we deleted expression of these proteins in platelets and assessed granule exocytosis. We measured products secreted by each type of platelet granule and analyzed EM platelet profiles by design-based stereology. We observed that the removal of Munc18-2 ablates the release of alpha, dense, and lysosomal granules from platelets, but we found no exocytic role for Munc18-1 or -3 in platelets. In vitro, Munc18-2-deficient platelets exhibited defective aggregation at low doses of collagen and impaired thrombus formation under shear stress. In vivo, megakaryocyte-specific Munc18-2 conditional knockout mice had a severe hemostatic defect and prolonged arterial and venous bleeding times. They were also protected against arterial thrombosis in a chemically induced model of arterial injury. Taken together, our results indicate that Munc18-2, but not Munc18-1 or Munc18-3, is essential for regulated exocytosis in platelets and platelet participation in thrombosis and hemostasis.
Collapse
Affiliation(s)
- Eduardo I Cardenas
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.,the Escuela de Ingenieria y Ciencias, Instituto Tecnologico de Monterrey, Monterrey, Nuevo Leon 64849, Mexico
| | - Ricardo Gonzalez
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.,the Escuela de Ingenieria y Ciencias, Instituto Tecnologico de Monterrey, Monterrey, Nuevo Leon 64849, Mexico
| | - Keegan Breaux
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Qi Da
- the Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas 77030.,the Department of Medicine, Baylor College of Medicine, Houston, Texas 77030
| | - Berenice A Gutierrez
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.,the Escuela de Ingenieria y Ciencias, Instituto Tecnologico de Monterrey, Monterrey, Nuevo Leon 64849, Mexico
| | - Marco A Ramos
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Rodolfo A Cardenas
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.,the Escuela de Medicina y Ciencias de la Salud, Instituto Tecnologico de Monterrey, Monterrey, Nuevo León 64710, México, and
| | - Alan R Burns
- the College of Optometry, University of Houston, Houston, Texas 77204
| | - Rolando E Rumbaut
- the Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas 77030.,the Department of Medicine, Baylor College of Medicine, Houston, Texas 77030
| | - Roberto Adachi
- From the Department of Pulmonary Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030,
| |
Collapse
|
9
|
Yang H, Ralle M, Wolfgang MJ, Dhawan N, Burkhead JL, Rodriguez S, Kaplan JH, Wong GW, Haughey N, Lutsenko S. Copper-dependent amino oxidase 3 governs selection of metabolic fuels in adipocytes. PLoS Biol 2018; 16:e2006519. [PMID: 30199530 PMCID: PMC6130853 DOI: 10.1371/journal.pbio.2006519] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 08/14/2018] [Indexed: 12/23/2022] Open
Abstract
Copper (Cu) has emerged as an important modifier of body lipid metabolism. However, how Cu contributes to the physiology of fat cells remains largely unknown. We found that adipocytes require Cu to establish a balance between main metabolic fuels. Differentiating adipocytes increase their Cu uptake along with the ATP7A-dependent transport of Cu into the secretory pathway to activate a highly up-regulated amino-oxidase copper-containing 3 (AOC3)/semicarbazide-sensitive amine oxidase (SSAO); in vivo, the activity of SSAO depends on the organism's Cu status. Activated SSAO oppositely regulates uptake of glucose and long-chain fatty acids and remodels the cellular proteome to coordinate changes in fuel availability and related downstream processes, such as glycolysis, de novo lipogenesis, and sphingomyelin/ceramide synthesis. The loss of SSAO-dependent regulation due to Cu deficiency, limited Cu transport to the secretory pathway, or SSAO inactivation shifts metabolism towards lipid-dependent pathways and results in adipocyte hypertrophy and fat accumulation. The results establish a role for Cu homeostasis in adipocyte metabolism and identify SSAO as a regulator of energy utilization processes in adipocytes.
Collapse
Affiliation(s)
- Haojun Yang
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Martina Ralle
- Department of Genetics, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Michael J. Wolfgang
- Center for Metabolism and Obesity Research, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Biological Chemistry, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Neha Dhawan
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jason L. Burkhead
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, Alaska, United States of America
| | - Susana Rodriguez
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland, United States of America
- Center for Metabolism and Obesity Research, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jack H. Kaplan
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - G. William Wong
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland, United States of America
- Center for Metabolism and Obesity Research, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Norman Haughey
- Department of Neurology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Svetlana Lutsenko
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland, United States of America
| |
Collapse
|
10
|
Gutierrez BA, Chavez MA, Rodarte AI, Ramos MA, Dominguez A, Petrova Y, Davalos AJ, Costa RM, Elizondo R, Tuvim MJ, Dickey BF, Burns AR, Heidelberger R, Adachi R. Munc18-2, but not Munc18-1 or Munc18-3, controls compound and single-vesicle-regulated exocytosis in mast cells. J Biol Chem 2018; 293:7148-7159. [PMID: 29599294 DOI: 10.1074/jbc.ra118.002455] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 03/20/2018] [Indexed: 11/06/2022] Open
Abstract
Mast cells (MCs) play pivotal roles in many inflammatory conditions including infections, anaphylaxis, and asthma. MCs store immunoregulatory compounds in their large cytoplasmic granules and, upon stimulation, secrete them via regulated exocytosis. Exocytosis in many cells requires the participation of Munc18 proteins (also known as syntaxin-binding proteins), and we found that mature MCs express all three mammalian isoforms: Munc18-1, -2, and -3. To study their functions in MC effector responses and test the role of MC degranulation in anaphylaxis, we used conditional knockout (cKO) mice in which each Munc18 protein was deleted exclusively in MCs. Using recordings of plasma membrane capacitance for high-resolution analysis of exocytosis in individual MCs, we observed an almost complete absence of exocytosis in Munc18-2-deficient MCs but intact exocytosis in MCs lacking Munc18-1 or Munc18-3. Stereological analysis of EM images of stimulated MCs revealed that the deletion of Munc18-2 also abolishes the homotypic membrane fusion required for compound exocytosis. We confirmed the severe defect in regulated exocytosis in the absence of Munc18-2 by measuring the secretion of mediators stored in MC granules. Munc18-2 cKO mice had normal morphology, development, and distribution of their MCs, indicating that Munc18-2 is not essential for the migration, retention, and maturation of MC-committed progenitors. Despite that, we found that Munc18-2 cKO mice were significantly protected from anaphylaxis. In conclusion, MC-regulated exocytosis is required for the anaphylactic response, and Munc18-2 is the sole Munc18 isoform that mediates membrane fusion during MC degranulation.
Collapse
Affiliation(s)
- Berenice A Gutierrez
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030; Escuela de Ingeniería y Ciencias, Tecnologico de Monterrey, Monterrey NL 64849 México
| | - Miguel A Chavez
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030; Escuela de Medicina y Ciencias de la Salud, Tecnologico de Monterrey, Monterrey NL 64710 México
| | - Alejandro I Rodarte
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030; Escuela de Medicina y Ciencias de la Salud, Tecnologico de Monterrey, Monterrey NL 64710 México
| | - Marco A Ramos
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Andrea Dominguez
- Escuela de Medicina y Ciencias de la Salud, Tecnologico de Monterrey, Monterrey NL 64710 México
| | - Youlia Petrova
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Alfredo J Davalos
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Renan M Costa
- Graduate School of Biomedical Sciences, Houston, Texas 77030
| | - Ramon Elizondo
- Escuela de Medicina y Ciencias de la Salud, Tecnologico de Monterrey, Monterrey NL 64710 México
| | - Michael J Tuvim
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Burton F Dickey
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Alan R Burns
- College of Optometry, University of Houston, Houston, Texas 77204
| | - Ruth Heidelberger
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas Health Science Center, Houston, Texas 77030
| | - Roberto Adachi
- Department of Pulmonary Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.
| |
Collapse
|
11
|
Dolai S, Liang T, Orabi AI, Xie L, Holmyard D, Javed TA, Fernandez NA, Xie H, Cattral MS, Thurmond DC, Thorn P, Gaisano HY. Depletion of the membrane-fusion regulator Munc18c attenuates caerulein hyperstimulation-induced pancreatitis. J Biol Chem 2017; 293:2510-2522. [PMID: 29284677 DOI: 10.1074/jbc.ra117.000792] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 12/21/2017] [Indexed: 12/26/2022] Open
Abstract
Epithelial pancreatic acinar cells perform crucial functions in food digestion, and acinar cell homeostasis required for secretion of digestive enzymes relies on SNARE-mediated exocytosis. The ubiquitously expressed Sec1/Munc18 protein mammalian uncoordinated-18c (Munc18c) regulates membrane fusion by activating syntaxin-4 (STX-4) to bind cognate SNARE proteins to form a SNARE complex that mediates exocytosis in many cell types. However, in the acinar cell, Munc18c's functions in exocytosis and homeostasis remain inconclusive. Here, we found that pancreatic acini from Munc18c-depleted mice (Munc18c+/-) and human pancreas (lenti-Munc18c-shRNA-treated) exhibit normal apical exocytosis of zymogen granules (ZGs) in response to physiologic stimulation with the intestinal hormone cholecystokinin (CCK-8). However, when stimulated with supraphysiologic CCK-8 levels to mimic pancreatitis, Munc18c-depleted (Munc18c+/-) mouse acini exhibited a reduction in pathological basolateral exocytosis of ZGs resulting from a decrease in fusogenic STX-4 SNARE complexes. This reduced basolateral exocytosis in part explained the less severe pancreatitis observed in Munc18c+/- mice after hyperstimulation with the CCK-8 analog caerulein. Likely as a result of this secretory blockade, Munc18c-depleted acini unexpectedly activated a component of the endoplasmic reticulum (ER) stress response that contributed to autophagy induction, resulting in downstream accumulation of autophagic vacuoles and autolysosomes. We conclude that Munc18c's role in mediating ectopic basolateral membrane fusion of ZGs contributes to the initiation of CCK-induced pancreatic injury, and that blockade of this secretory process could increase autophagy induction.
Collapse
Affiliation(s)
- Subhankar Dolai
- From the Departments of Medicine and .,Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Tao Liang
- From the Departments of Medicine and.,Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Abrahim I Orabi
- Division of Pediatric Gastroenterology, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania 15224
| | - Li Xie
- From the Departments of Medicine and.,Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Douglas Holmyard
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada
| | - Tanveer A Javed
- Division of Pediatric Gastroenterology, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania 15224
| | | | | | - Mark S Cattral
- Toronto General Hospital Research Institute, University Health Network, University of Toronto, Toronto, Ontario M5G 2N2, Canada
| | - Debbie C Thurmond
- Beckman Research Institute of the City of Hope, Duarte, California 91010, and
| | - Peter Thorn
- School of Biomedical Sciences,University of Sydney, Sydney, New South Wales 2050, Australia
| | - Herbert Y Gaisano
- From the Departments of Medicine and .,Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| |
Collapse
|
12
|
Hamada N, Iwamoto I, Tabata H, Nagata KI. MUNC18-1 gene abnormalities are involved in neurodevelopmental disorders through defective cortical architecture during brain development. Acta Neuropathol Commun 2017; 5:92. [PMID: 29191246 PMCID: PMC5709915 DOI: 10.1186/s40478-017-0498-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 11/19/2017] [Indexed: 12/03/2022] Open
Abstract
While Munc18–1 interacts with Syntaxin1 and controls the formation of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) complex to regulate presynaptic vesicle fusion in developed neurons, this molecule is likely to be involved in brain development since its gene abnormalities cause early infantile epileptic encephalopathy with suppression-burst (Ohtahara syndrome), neonatal epileptic encephalopathy and other neurodevelopmental disorders. We thus analyzed physiological significance of Munc18–1 during cortical development. Munc18–1-knockdown impaired cortical neuron positioning during mouse corticogenesis. Time-lapse imaging revealed that the mispositioning was attributable to defects in radial migration in the intermediate zone and cortical plate. Notably, Syntaxin1A was critical for radial migration downstream of Munc18–1. As for the underlying mechanism, Munc18–1-knockdown in cortical neurons hampered post-Golgi vesicle trafficking and subsequent vesicle fusion at the plasma membrane in vivo and in vitro, respectively. Notably, Syntaxin1A-silencing did not affect the post-Golgi vesicle trafficking. Taken together, Munc18–1 was suggested to regulate radial migration by modulating not only vesicle fusion at the plasma membrane to distribute various proteins on the cell surface for interaction with radial fibers, but also preceding vesicle transport from Golgi to the plasma membrane. Although knockdown experiments suggested that Syntaxin1A does not participate in the vesicle trafficking, it was supposed to regulate subsequent vesicle fusion under the control of Munc18–1. These observations may shed light on the mechanism governing radial migration of cortical neurons. Disruption of Munc18–1 function may result in the abnormal corticogenesis, leading to neurodevelopmental disorders with MUNC18–1 gene abnormalities.
Collapse
|
13
|
SNARE phosphorylation: a control mechanism for insulin-stimulated glucose transport and other regulated exocytic events. Biochem Soc Trans 2017; 45:1271-1277. [PMID: 29101310 DOI: 10.1042/bst20170202] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 10/03/2017] [Accepted: 10/04/2017] [Indexed: 11/17/2022]
Abstract
Trafficking within eukaryotic cells is a complex and highly regulated process; events such as recycling of plasma membrane receptors, formation of multivesicular bodies, regulated release of hormones and delivery of proteins to membranes all require directionality and specificity. The underpinning processes, including cargo selection, membrane fusion, trafficking flow and timing, are controlled by a variety of molecular mechanisms and engage multiple families of lipids and proteins. Here, we will focus on control of trafficking processes via the action of the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) family of proteins, in particular their regulation by phosphorylation. We will describe how these proteins are controlled in a range of regulated trafficking events, with particular emphasis on the insulin-stimulated delivery of glucose transporters to the surface of adipose and muscle cells. Here, we focus on a few examples of SNARE phosphorylation which exemplify distinct ways in which SNARE machinery phosphorylation may regulate membrane fusion.
Collapse
|
14
|
Christie MP, Hu SH, Whitten AE, Rehman A, Jarrott RJ, King GJ, Collins BM, Martin JL. Revisiting interaction specificity reveals neuronal and adipocyte Munc18 membrane fusion regulatory proteins differ in their binding interactions with partner SNARE Syntaxins. PLoS One 2017; 12:e0187302. [PMID: 29088285 PMCID: PMC5663490 DOI: 10.1371/journal.pone.0187302] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 10/17/2017] [Indexed: 01/01/2023] Open
Abstract
The efficient delivery of cellular cargo relies on the fusion of cargo-carrying vesicles with the correct membrane at the correct time. These spatiotemporal fusion events occur when SNARE proteins on the vesicle interact with cognate SNARE proteins on the target membrane. Regulatory Munc18 proteins are thought to contribute to SNARE interaction specificity through interaction with the SNARE protein Syntaxin. Neuronal Munc18a interacts with Syntaxin1 but not Syntaxin4, and adipocyte Munc18c interacts with Syntaxin4 but not Syntaxin1. Here we show that this accepted view of specificity needs revision. We find that Munc18c interacts with both Syntaxin4 and Syntaxin1, and appears to bind “non-cognate” Syntaxin1 a little more tightly than Syntaxin4. Munc18a binds Syntaxin1 and Syntaxin4, though it interacts with its cognate Syntaxin1 much more tightly. We also observed that when bound to non-cognate Munc18c, Syntaxin1 captures its neuronal SNARE partners SNAP25 and VAMP2, and Munc18c can bind to pre-formed neuronal SNARE ternary complex. These findings reveal that Munc18a and Munc18c bind Syntaxins differently. Munc18c relies principally on the Syntaxin N-peptide interaction for binding Syntaxin4 or Syntaxin1, whereas Munc18a can bind Syntaxin1 tightly whether or not the Syntaxin1 N-peptide is present. We conclude that Munc18a and Munc18c differ in their binding interactions with Syntaxins: Munc18a has two tight binding modes/sites for Syntaxins as defined previously but Munc18c has just one that requires the N-peptide. These results indicate that the interactions between Munc18 and Syntaxin proteins, and the consequences for in vivo function, are more complex than can be accounted for by binding specificity alone.
Collapse
Affiliation(s)
- Michelle P. Christie
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia
- * E-mail: (MPC); (JLM)
| | - Shu-Hong Hu
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia
| | - Andrew E. Whitten
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia
| | - Asma Rehman
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia
| | - Russell J. Jarrott
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia
| | - Gordon J. King
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia
| | - Brett M. Collins
- Division of Cell Biology and Molecular Medicine, Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia
| | - Jennifer L. Martin
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland, Australia
- Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia
- * E-mail: (MPC); (JLM)
| |
Collapse
|
15
|
Morey C, Kienle CN, Klöpper TH, Burkhardt P, Fasshauer D. Evidence for a conserved inhibitory binding mode between the membrane fusion assembly factors Munc18 and syntaxin in animals. J Biol Chem 2017; 292:20449-20460. [PMID: 29046354 DOI: 10.1074/jbc.m117.811182] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 10/10/2017] [Indexed: 12/30/2022] Open
Abstract
The membrane fusion necessary for vesicle trafficking is driven by the assembly of heterologous SNARE proteins orchestrated by the binding of Sec1/Munc18 (SM) proteins to specific syntaxin SNARE proteins. However, the precise mode of interaction between SM proteins and SNAREs is debated, as contrasting binding modes have been found for different members of the SM protein family, including the three vertebrate Munc18 isoforms. While different binding modes could be necessary, given their roles in different secretory processes in different tissues, the structural similarity of the three isoforms makes this divergence perplexing. Although the neuronal isoform Munc18a is well-established to bind tightly to both the closed conformation and the N-peptide of syntaxin 1a, thereby inhibiting SNARE complex formation, Munc18b and -c, which have a more widespread distribution, are reported to mainly interact with the N-peptide of their partnering syntaxins and are thought to instead promote SNARE complex formation. We have reinvestigated the interaction between Munc18c and syntaxin 4 (Syx4). Using isothermal titration calorimetry, we found that Munc18c, like Munc18a, binds to both the closed conformation and the N-peptide of Syx4. Furthermore, using a novel kinetic approach, we found that Munc18c, like Munc18a, slows down SNARE complex formation through high-affinity binding to syntaxin. This strongly suggests that secretory Munc18s in general control the accessibility of the bound syntaxin, probably preparing it for SNARE complex assembly.
Collapse
Affiliation(s)
- Czuee Morey
- From the Département des neurosciences fondamentales, Université de Lausanne, Rue du Bugnon 9, CH-1005 Lausanne, Switzerland
| | - C Nickias Kienle
- From the Département des neurosciences fondamentales, Université de Lausanne, Rue du Bugnon 9, CH-1005 Lausanne, Switzerland
| | - Tobias H Klöpper
- Whitehat Life Sciences Ltd., 20 Wenlock Road, N1 7GU London, United Kingdom, and
| | - Pawel Burkhardt
- the Marine Biological Association, Citadel Hill Marine Laboratory, Plymouth PL1 2PB, United Kingdom
| | - Dirk Fasshauer
- From the Département des neurosciences fondamentales, Université de Lausanne, Rue du Bugnon 9, CH-1005 Lausanne, Switzerland,
| |
Collapse
|
16
|
Kim SP, Li Z, Zoch ML, Frey JL, Bowman CE, Kushwaha P, Ryan KA, Goh BC, Scafidi S, Pickett JE, Faugere MC, Kershaw EE, Thorek DLJ, Clemens TL, Wolfgang MJ, Riddle RC. Fatty acid oxidation by the osteoblast is required for normal bone acquisition in a sex- and diet-dependent manner. JCI Insight 2017; 2:92704. [PMID: 28814665 DOI: 10.1172/jci.insight.92704] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 07/19/2017] [Indexed: 12/20/2022] Open
Abstract
Postnatal bone formation is influenced by nutritional status and compromised by disturbances in metabolism. The oxidation of dietary lipids represents a critical source of ATP for many cells but has been poorly studied in the skeleton, where the prevailing view is that glucose is the primary energy source. Here, we examined fatty acid uptake by bone and probed the requirement for fatty acid catabolism during bone formation by specifically disrupting the expression of carnitine palmitoyltransferase 2 (Cpt2), an obligate enzyme in fatty acid oxidation, in osteoblasts and osteocytes. Radiotracer studies demonstrated that the skeleton accumulates a significant fraction of postprandial fatty acids, which was equal to or in excess of that acquired by skeletal muscle or adipose tissue. Female, but not male, Cpt2 mutant mice exhibited significant impairments in postnatal bone acquisition, potentially due to an inability of osteoblasts to modify fuel selection. Intriguingly, suppression of fatty acid utilization by osteoblasts and osteocytes also resulted in the development of dyslipidemia and diet-dependent modifications in body composition. Taken together, these studies demonstrate a requirement for fatty acid oxidation during bone accrual and suggest a role for the skeleton in lipid homeostasis.
Collapse
Affiliation(s)
| | - Zhu Li
- Department of Orthopaedic Surgery
| | | | | | | | | | | | | | - Susanna Scafidi
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Julie E Pickett
- Division of Nuclear Medicine and Molecular Imaging, Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | | | - Erin E Kershaw
- Division of Endocrinology, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Daniel L J Thorek
- Division of Nuclear Medicine and Molecular Imaging, Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Cancer Molecular and Functional Imaging Program, Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Thomas L Clemens
- Department of Orthopaedic Surgery.,Baltimore Veterans Administration Medical Center, Baltimore, Maryland, USA
| | | | - Ryan C Riddle
- Department of Orthopaedic Surgery.,Baltimore Veterans Administration Medical Center, Baltimore, Maryland, USA
| |
Collapse
|
17
|
Dahlman I, Belarbi Y, Laurencikiene J, Pettersson AM, Arner P, Kulyté A. Comprehensive functional screening of miRNAs involved in fat cell insulin sensitivity among women. Am J Physiol Endocrinol Metab 2017; 312:E482-E494. [PMID: 28270439 DOI: 10.1152/ajpendo.00251.2016] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 01/18/2017] [Accepted: 02/22/2017] [Indexed: 01/12/2023]
Abstract
The key pathological link between obesity and type 2 diabetes is insulin resistance, but the molecular mechanisms are not entirely identified. micro-RNAs (miRNA) are dysregulated in obesity and may contribute to insulin resistance. Our objective was to detect and functionally investigate miRNAs linked to insulin sensitivity in human subcutaneous white adipose tissue (scWAT). Subjects were selected based on the insulin-stimulated lipogenesis response of subcutaneous adipocytes. Global miRNA profiling was performed in abdominal scWAT of 18 obese insulin-resistance (OIR), 21 obese insulin-sensitive (OIS), and 9 lean women. miRNAs demonstrating differential expression between OIR and OIS women were overexpressed in human in vitro-differentiated adipocytes followed by assessment of lipogenesis and identification of miRNA targets by measuring mRNA/protein expression and 3'-untranslated region analysis. Eleven miRNAs displayed differential expression between OIR and OIS states. Overexpression of miR-143-3p and miR-652-3p increased insulin-stimulated lipogenesis in human in vitro differentiated adipocytes and directly or indirectly affected several genes/proteins involved in insulin signaling at transcriptional or posttranscriptional levels. Adipose expression of miR-143-3p and miR-652-3p was positively associated with insulin-stimulated lipogenesis in scWAT independent of body mass index. In conclusion, miR-143-3p and miR-652-3p are linked to scWAT insulin resistance independent of obesity and influence insulin-stimulated lipogenesis by interacting at different steps with insulin-signaling pathways.
Collapse
Affiliation(s)
- Ingrid Dahlman
- Lipid Laboratory, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Yasmina Belarbi
- Lipid Laboratory, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Jurga Laurencikiene
- Lipid Laboratory, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Annie M Pettersson
- Lipid Laboratory, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Peter Arner
- Lipid Laboratory, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Agné Kulyté
- Lipid Laboratory, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
| |
Collapse
|
18
|
Zhou X, Shentu P, Xu Y. Spatiotemporal Regulators for Insulin-Stimulated GLUT4 Vesicle Exocytosis. J Diabetes Res 2017; 2017:1683678. [PMID: 28529958 PMCID: PMC5424486 DOI: 10.1155/2017/1683678] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 03/21/2017] [Accepted: 04/03/2017] [Indexed: 11/30/2022] Open
Abstract
Insulin increases glucose uptake and storage in muscle and adipose cells, which is accomplished through the mobilization of intracellular GLUT4 storage vesicles (GSVs) to the cell surface upon stimulation. Importantly, the dysfunction of insulin-regulated GLUT4 trafficking is strongly linked with peripheral insulin resistance and type 2 diabetes in human. The insulin signaling pathway, key signaling molecules involved, and precise trafficking itinerary of GSVs are largely identified. Understanding the interaction between insulin signaling molecules and key regulatory proteins that are involved in spatiotemporal regulation of GLUT4 vesicle exocytosis is of great importance to explain the pathogenesis of diabetes and may provide new potential therapeutic targets.
Collapse
Affiliation(s)
- Xiaoxu Zhou
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou 310027, China
| | - Ping Shentu
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou 310027, China
| | - Yingke Xu
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou 310027, China
- *Yingke Xu:
| |
Collapse
|
19
|
Li Z, Frey JL, Wong GW, Faugere MC, Wolfgang MJ, Kim JK, Riddle RC, Clemens TL. Glucose Transporter-4 Facilitates Insulin-Stimulated Glucose Uptake in Osteoblasts. Endocrinology 2016; 157:4094-4103. [PMID: 27689415 PMCID: PMC5086531 DOI: 10.1210/en.2016-1583] [Citation(s) in RCA: 59] [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: 12/11/2022]
Abstract
Recent studies have identified the osteoblast as an insulin responsive cell that participates in global energy homeostasis. Here, we show that glucose transporter-4 (Glut4) is required for insulin-dependent uptake and oxidation of glucose in mature osteoblasts. In primary cultures of mouse osteoblasts, insulin increased uptake and oxidation of 14C-glucose in a dose-dependent fashion but did not significantly affect uptake or oxidation of 14C-oleate. In vitro, undifferentiated osteoblasts expressed 3 high-affinity Gluts: Glut1, Glut4, and Glut3. However, although levels of Glut1 and Glut3 remained constant during the course of osteoblast differentiation, Glut4 expression increased by 5-fold in association with enhanced insulin-stimulated glucose uptake. Glut4 ablation in osteoblasts in vitro eliminated insulin-stimulated glucose uptake, reduced proliferation and diminished measures of osteoblast maturation. In vivo, Glut4 expression was observed in osteoblasts, osteocytes, and chondrocytes at a level approaching that observed in adjacent skeletal muscle. To determine the importance of Glut4 in bone in vivo, we generated mice lacking Glut4 in osteoblasts and osteocytes (ΔGlut4). ΔGlut4 mice exhibited normal bone architecture but exhibited an increase in peripheral fat in association with hyperinsulinemia, β-cell islet hypertrophy, and reduced insulin sensitivity. Surprisingly, the expression of insulin target genes in liver, muscle, and adipose from ΔGlut4 mice were unchanged or increased, indicating that alterations in glucose homeostasis were the result of reduced clearance by bone. These findings suggest that Glut4 mediates insulin-stimulated glucose uptake by mature osteoblasts/osteocytes and that the magnitude of glucose use by bone cells is sufficient to impact global glucose disposal in the mouse.
Collapse
Affiliation(s)
- Zhu Li
- Department of Orthopaedic Surgery (Z.L., J.L.F., R.C.R., T.L.C.), Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Physiology (G.W.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Medicine (M.-C.F.), Division of Nephology, University of Kentucky, Lexington, Kentucky 40356; Department of Biological Chemistry (M.J.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Program in Molecular Medicine (J.K.K.), University of Massachusetts Medical School, Wooster, Massachusetts 01605; and Baltimore Veterans Administration Medical Center (R.C.R., T.L.C.), Baltimore, Maryland 21201
| | - Julie L Frey
- Department of Orthopaedic Surgery (Z.L., J.L.F., R.C.R., T.L.C.), Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Physiology (G.W.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Medicine (M.-C.F.), Division of Nephology, University of Kentucky, Lexington, Kentucky 40356; Department of Biological Chemistry (M.J.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Program in Molecular Medicine (J.K.K.), University of Massachusetts Medical School, Wooster, Massachusetts 01605; and Baltimore Veterans Administration Medical Center (R.C.R., T.L.C.), Baltimore, Maryland 21201
| | - G William Wong
- Department of Orthopaedic Surgery (Z.L., J.L.F., R.C.R., T.L.C.), Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Physiology (G.W.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Medicine (M.-C.F.), Division of Nephology, University of Kentucky, Lexington, Kentucky 40356; Department of Biological Chemistry (M.J.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Program in Molecular Medicine (J.K.K.), University of Massachusetts Medical School, Wooster, Massachusetts 01605; and Baltimore Veterans Administration Medical Center (R.C.R., T.L.C.), Baltimore, Maryland 21201
| | - Marie-Claude Faugere
- Department of Orthopaedic Surgery (Z.L., J.L.F., R.C.R., T.L.C.), Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Physiology (G.W.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Medicine (M.-C.F.), Division of Nephology, University of Kentucky, Lexington, Kentucky 40356; Department of Biological Chemistry (M.J.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Program in Molecular Medicine (J.K.K.), University of Massachusetts Medical School, Wooster, Massachusetts 01605; and Baltimore Veterans Administration Medical Center (R.C.R., T.L.C.), Baltimore, Maryland 21201
| | - Michael J Wolfgang
- Department of Orthopaedic Surgery (Z.L., J.L.F., R.C.R., T.L.C.), Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Physiology (G.W.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Medicine (M.-C.F.), Division of Nephology, University of Kentucky, Lexington, Kentucky 40356; Department of Biological Chemistry (M.J.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Program in Molecular Medicine (J.K.K.), University of Massachusetts Medical School, Wooster, Massachusetts 01605; and Baltimore Veterans Administration Medical Center (R.C.R., T.L.C.), Baltimore, Maryland 21201
| | - Jason K Kim
- Department of Orthopaedic Surgery (Z.L., J.L.F., R.C.R., T.L.C.), Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Physiology (G.W.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Medicine (M.-C.F.), Division of Nephology, University of Kentucky, Lexington, Kentucky 40356; Department of Biological Chemistry (M.J.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Program in Molecular Medicine (J.K.K.), University of Massachusetts Medical School, Wooster, Massachusetts 01605; and Baltimore Veterans Administration Medical Center (R.C.R., T.L.C.), Baltimore, Maryland 21201
| | - Ryan C Riddle
- Department of Orthopaedic Surgery (Z.L., J.L.F., R.C.R., T.L.C.), Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Physiology (G.W.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Medicine (M.-C.F.), Division of Nephology, University of Kentucky, Lexington, Kentucky 40356; Department of Biological Chemistry (M.J.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Program in Molecular Medicine (J.K.K.), University of Massachusetts Medical School, Wooster, Massachusetts 01605; and Baltimore Veterans Administration Medical Center (R.C.R., T.L.C.), Baltimore, Maryland 21201
| | - Thomas L Clemens
- Department of Orthopaedic Surgery (Z.L., J.L.F., R.C.R., T.L.C.), Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Physiology (G.W.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Medicine (M.-C.F.), Division of Nephology, University of Kentucky, Lexington, Kentucky 40356; Department of Biological Chemistry (M.J.W.), Center for Metabolism and Obesity Research, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Program in Molecular Medicine (J.K.K.), University of Massachusetts Medical School, Wooster, Massachusetts 01605; and Baltimore Veterans Administration Medical Center (R.C.R., T.L.C.), Baltimore, Maryland 21201
| |
Collapse
|
20
|
Xu S, Kim JH, Hwang KH, Das R, Quan X, Nguyen TT, Kim SJ, Cha SK, Park KS. Autocrine insulin increases plasma membrane KATP channel via PI3K-VAMP2 pathway in MIN6 cells. Biochem Biophys Res Commun 2015; 468:752-7. [DOI: 10.1016/j.bbrc.2015.11.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 11/04/2015] [Indexed: 11/24/2022]
|
21
|
Xu H, Arnold MG, Kumar SV. Differential Effects of Munc18s on Multiple Degranulation-Relevant Trans-SNARE Complexes. PLoS One 2015; 10:e0138683. [PMID: 26384026 PMCID: PMC4575180 DOI: 10.1371/journal.pone.0138683] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 09/02/2015] [Indexed: 11/24/2022] Open
Abstract
Mast cell exocytosis, which includes compound degranulation and vesicle-associated piecemeal degranulation, requires multiple Q- and R- SNAREs. It is not clear how these SNAREs pair to form functional trans-SNARE complexes and how these trans-SNARE complexes are selectively regulated for fusion. Here we undertake a comprehensive examination of the capacity of two Q-SNARE subcomplexes (syntaxin3/SNAP-23 and syntaxin4/SNAP-23) to form fusogenic trans-SNARE complexes with each of the four granule-borne R-SNAREs (VAMP2, 3, 7, 8). We report the identification of at least six distinct trans-SNARE complexes under enhanced tethering conditions: i) VAMP2/syntaxin3/SNAP-23, ii) VAMP2/syntaxin4/SNAP-23, iii) VAMP3/syntaxin3/SNAP-23, iv) VAMP3/syntaxin4/SNAP-23, v) VAMP8/syntaxin3/SNAP-23, and vi) VAMP8/syntaxin4/SNAP-23. We show for the first time that Munc18a operates synergistically with SNAP-23-based non-neuronal SNARE complexes (i to iv) in lipid mixing, in contrast to Munc18b and c, which exhibit no positive effect on any SNARE combination tested. Pre-incubation with Munc18a renders the SNARE-dependent fusion reactions insensitive to the otherwise inhibitory R-SNARE cytoplasmic domains, suggesting a protective role of Munc18a for its cognate SNAREs. Our findings substantiate the recently discovered but unexpected requirement for Munc18a in mast cell exocytosis, and implicate post-translational modifications in Munc18b/c activation.
Collapse
Affiliation(s)
- Hao Xu
- Department of Biological Sciences, University of Southern Mississippi, Hattiesburg, Mississippi, United States of America
- * E-mail:
| | - Matthew Grant Arnold
- Department of Biological Sciences, University of Southern Mississippi, Hattiesburg, Mississippi, United States of America
| | - Sushmitha Vijay Kumar
- Department of Biological Sciences, University of Southern Mississippi, Hattiesburg, Mississippi, United States of America
| |
Collapse
|
22
|
Lorenzo DN, Healy JA, Hostettler J, Davis J, Yang J, Wang C, Hohmeier HE, Zhang M, Bennett V. Ankyrin-B metabolic syndrome combines age-dependent adiposity with pancreatic β cell insufficiency. J Clin Invest 2015; 125:3087-102. [PMID: 26168218 DOI: 10.1172/jci81317] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 05/27/2015] [Indexed: 12/22/2022] Open
Abstract
Rare functional variants of ankyrin-B have been implicated in human disease, including hereditary cardiac arrhythmia and type 2 diabetes (T2D). Here, we developed murine models to evaluate the metabolic consequences of these alterations in vivo. Specifically, we generated knockin mice that express either the human ankyrin-B variant R1788W, which is present in 0.3% of North Americans of mixed European descent and is associated with T2D, or L1622I, which is present in 7.5% of African Americans. Young AnkbR1788W/R1788W mice displayed primary pancreatic β cell insufficiency that was characterized by reduced insulin secretion in response to muscarinic agonists, combined with increased peripheral glucose uptake and concomitantly increased plasma membrane localization of glucose transporter 4 (GLUT4) in skeletal muscle and adipocytes. In contrast, older AnkbR1788W/R1788W and AnkbL1622I/L1622I mice developed increased adiposity, a phenotype that was reproduced in cultured adipocytes, and insulin resistance. GLUT4 trafficking was altered in animals expressing mutant forms of ankyrin-B, and we propose that increased cell surface expression of GLUT4 in skeletal muscle and fatty tissue of AnkbR1788W/R1788W mice leads to the observed age-dependent adiposity. Together, our data suggest that ankyrin-B deficiency results in a metabolic syndrome that combines primary pancreatic β cell insufficiency with peripheral insulin resistance and is directly relevant to the nearly one million North Americans bearing the R1788W ankyrin-B variant.
Collapse
|
23
|
Coon SD, Rajendran VM, Schwartz JH, Singh SK. Glucose-dependent insulinotropic polypeptide-mediated signaling pathways enhance apical PepT1 expression in intestinal epithelial cells. Am J Physiol Gastrointest Liver Physiol 2015; 308:G56-62. [PMID: 25377315 PMCID: PMC4281688 DOI: 10.1152/ajpgi.00168.2014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have shown recently that glucose-dependent insulinotropic polypeptide (GIP), but not glucagon-like peptide 1 (GLP-1) augments H(+) peptide cotransporter (PepT1)-mediated peptide absorption in murine jejunum. While we observed that inhibiting cAMP production decreased this augmentation of PepT1 activity by GIP, it was unclear whether PKA and/or other regulators of cAMP signaling pathway(s) were involved. This study utilized tritiated glycyl-sarcosine [(3)H-glycyl-sarcosine (Gly-Sar), a relatively nonhydrolyzable dipeptide] uptake to measure PepT1 activity in CDX2-transfected IEC-6 (IEC-6/CDX2) cells, an absorptive intestinal epithelial cell model. Similar to our earlier observations with mouse jejunum, GIP but not GLP-1 augmented Gly-Sar uptake (control vs. +GIP: 154 ± 22 vs. 454 ± 39 pmol/mg protein; P < 0.001) in IEC-6/CDX2 cells. Rp-cAMP (a PKA inhibitor) and wortmannin [phosophoinositide-3-kinase (PI3K) inhibitor] pretreatment completely blocked, whereas neither calphostin C (a potent PKC inhibitor) nor BAPTA (an intracellular Ca(2+) chelator) pretreatment affected the GIP-augmented Gly-Sar uptake in IEC-6/CDX2 cells. The downstream metabolites Epac (control vs. Epac agonist: 287 ± 22 vs. 711 ± 80 pmol/mg protein) and AKT (control vs. AKT inhibitor: 720 ± 50 vs. 75 ± 19 pmol/mg protein) were shown to be involved in GIP-augmented PepT1 activity as well. Western blot analyses revealed that both GIP and Epac agonist pretreatment enhance the PepT1 expression on the apical membranes, which is completely blocked by wortmannin in IEC-6/CDX2 cells. These observations demonstrate that both cAMP and PI3K signaling pathways augment GIP-induced peptide uptake through Epac and AKT-mediated pathways in intestinal epithelial cells, respectively. In addition, these observations also indicate that both Epac and AKT-mediated signaling pathways increase apical membrane expression of PepT1 in intestinal absorptive epithelial cells.
Collapse
Affiliation(s)
- Steven D. Coon
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Department of Medicine, Boston Veterans Affairs Healthcare System, Boston, Massachusetts; ,3Department of Medicine, Boston University Clinical & Translational Science Institute, Boston, Massachusetts; and
| | - Vazhaikkurichi M. Rajendran
- 4Department of Biochemistry and Molecular Biology, West Virginia University School of Medicine, Morgantown, West Virginia
| | - John H. Schwartz
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts;
| | - Satish K. Singh
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Department of Medicine, Boston Veterans Affairs Healthcare System, Boston, Massachusetts;
| |
Collapse
|
24
|
Govers R. Molecular mechanisms of GLUT4 regulation in adipocytes. DIABETES & METABOLISM 2014; 40:400-10. [DOI: 10.1016/j.diabet.2014.01.005] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 01/24/2014] [Accepted: 01/26/2014] [Indexed: 01/28/2023]
|
25
|
Ramalingam L, Yoder SM, Oh E, Thurmond DC. Munc18c: a controversial regulator of peripheral insulin action. Trends Endocrinol Metab 2014; 25:601-8. [PMID: 25028245 PMCID: PMC4253632 DOI: 10.1016/j.tem.2014.06.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 06/12/2014] [Accepted: 06/20/2014] [Indexed: 12/19/2022]
Abstract
Insulin resistance, a hallmark of impaired glucose tolerance and type 2 diabetes (T2D), arises from dysfunction of insulin action and subsequent glucose uptake by peripheral tissues, predominantly skeletal muscle and fat. Exocytosis of glucose transporter (GLUT4)-containing vesicles facilitated by soluble NSF (N-ethylmaleimide-sensitive factor) attachment receptor (SNARE) protein isoforms, and Munc18c (mammalian homolog of Unc-18c) mediates this glucose uptake. Emerging evidences, including recent human clinical studies, point to pivotal roles for Munc18c in peripheral insulin action in adipose and skeletal muscle. Intriguing new advances are also initiating debates regarding the molecular mechanism(s) controlling Munc18c action. The objective of this review is therefore to present a balanced perspective of new continuities and controversies surrounding the regulation and requirement for Munc18c in the regulation of peripheral insulin action.
Collapse
Affiliation(s)
- Latha Ramalingam
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Stephanie M Yoder
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Eunjin Oh
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Debbie C Thurmond
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
| |
Collapse
|
26
|
Abstract
GLUT4 is regulated by its intracellular localization. In the absence of insulin, GLUT4 is efficiently retained intracellularly within storage compartments in muscle and fat cells. Upon insulin stimulation (and contraction in muscle), GLUT4 translocates from these compartments to the cell surface where it transports glucose from the extracellular milieu into the cell. Its implication in insulin-regulated glucose uptake makes GLUT4 not only a key player in normal glucose homeostasis but also an important element in insulin resistance and type 2 diabetes. Nevertheless, how GLUT4 is retained intracellularly and how insulin acts on this retention mechanism is largely unclear. In this review, the current knowledge regarding the various molecular processes that govern GLUT4 physiology is discussed as well as the questions that remain.
Collapse
|
27
|
Brochetta C, Suzuki R, Vita F, Soranzo MR, Claver J, Madjene LC, Attout T, Vitte J, Varin-Blank N, Zabucchi G, Rivera J, Blank U. Munc18-2 and syntaxin 3 control distinct essential steps in mast cell degranulation. THE JOURNAL OF IMMUNOLOGY 2013; 192:41-51. [PMID: 24323579 DOI: 10.4049/jimmunol.1301277] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Mast cell degranulation requires N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) and mammalian uncoordinated18 (Munc18) fusion accessory proteins for membrane fusion. However, it is still unknown how their interaction supports fusion. In this study, we found that small interfering RNA-mediated silencing of the isoform Munc18-2 in mast cells inhibits cytoplasmic secretory granule (SG) release but not CCL2 chemokine secretion. Silencing of its SNARE-binding partner syntaxin 3 (STX3) also markedly inhibited degranulation, whereas combined knockdown produced an additive inhibitory effect. Strikingly, while Munc18-2 silencing impaired SG translocation, silencing of STX3 inhibited fusion, demonstrating unique roles of each protein. Immunogold studies showed that both Munc18-2 and STX3 are located on the granule surface, but also within the granule matrix and in small nocodazole-sensitive clusters of the cytoskeletal meshwork surrounding SG. After stimulation, clusters containing both effectors were detected at fusion sites. In resting cells, Munc18-2, but not STX3, interacted with tubulin. This interaction was sensitive to nocodazole treatment and decreased after stimulation. Our results indicate that Munc18-2 dynamically couples the membrane fusion machinery to the microtubule cytoskeleton and demonstrate that Munc18-2 and STX3 perform distinct, but complementary, functions to support, respectively, SG translocation and membrane fusion in mast cells.
Collapse
Affiliation(s)
- Cristiana Brochetta
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
| | - Ryo Suzuki
- Laboratory of Molecular Immunogenetics, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, 20892
| | - Francesca Vita
- Department of Life Sciences Department of Physiology and Pathology, University of Trieste, Italy
| | - Maria Rosa Soranzo
- Department of Life Sciences Department of Physiology and Pathology, University of Trieste, Italy
| | - Julien Claver
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
| | - Lydia Celia Madjene
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
| | - Tarik Attout
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
| | - Joana Vitte
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
| | - Nadine Varin-Blank
- Inserm U978, 93000 Bobigny, France.,Laboratoire d'excellence "Inflamex," Unité de Formation et de Recherche Santé-Médecine-Biologie Humaine, 93000 Bobigny, France
| | - Giuliano Zabucchi
- Department of Life Sciences Department of Physiology and Pathology, University of Trieste, Italy
| | - Juan Rivera
- Laboratory of Molecular Immunogenetics, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, 20892
| | - Ulrich Blank
- Inserm UMRS-699, 75018 Paris, France.,Université Paris Diderot, Sorbonne Paris Cite, Laboratoire d'excellence INFLAMEX, 75018 Paris, France
| |
Collapse
|
28
|
Beh JE, Khoo LT, Latip J, Abdullah MP, Alitheen NBM, Adam Z, Ismail A, Hamid M. SDF7, a group of Scoparia dulcis Linn. derived flavonoid compounds, stimulates glucose uptake and regulates adipocytokines in 3T3-F442a adipocytes. JOURNAL OF ETHNOPHARMACOLOGY 2013; 150:339-352. [PMID: 24029250 DOI: 10.1016/j.jep.2013.09.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 08/07/2013] [Accepted: 09/03/2013] [Indexed: 06/02/2023]
Abstract
ETHNOPHARMACOLOGY RELEVANCE Adipocytes are major tissues involved in glucose uptake second to skeletal muscle and act as the main adipocytokines mediator that regulates glucose uptake mechanism and cellular differentiation. The objective of this study were to examine the effect of the SDF7, which is a fraction consists of four flavonoid compounds (quercetin: p-coumaric acid: luteolin: apigenin=8: 26: 1: 3) from Scoparia dulcis Linn., on stimulating the downstream components of insulin signalling and the adipocytokines expression on different cellular fractions of 3T3-F442a adipocytes. MATERIAL AND METHODS Morphology and lipid accumulation of differentiated 3T3-F442a adipocytes by 100 nM insulin treated with different concentrations of SDF7 and rosiglitazone were examined followed by the evaluation of glucose uptake activity expressions of insulin signalling downstream components (IRS-1, PI3-kinase, PKB, PKC, TC10 and GLUT4) from four cellular fractions (plasma membrane, cytosol, high density microsome and low density microsome). Next, the expression level of adipocytokines (TNF-α, adiponectin and leptin) and immunoblotting of treated 3T3-F442 adipocytes was determined at 30 min and 480 min. Glucose transporter 4 (GLUT4) translocation of 3T3-F442a adipocytes membrane was also determined. Lastly, mRNA expression of adiponectin and PPAR-γ of 3T3-F442a adipocytes were induced and compared with basal concentration. RESULTS It was found that SDF7 was able to induce adipocytes differentiation with great extends of morphological changes, lipid synthesis and lipid stimulation in vitro. SDF7 stimulation of glucose transport on 3T3-F442a adipocytes are found to be dose independent, time-dependent and plasma membrane GLUT4 expression-dependent. Moreover, SDF7 are observed to be able to suppress TNF-α and leptin expressions that were mediated by 3T3-F442a adipocytes, while stimulated adiponectin secretion on the cells. There was a significant expression (p<0.01) of protein kinase C and small G protein TC10 on 3T3-F442a adipocytes upon treatment with SDF7 as compared to the control. SDF7 was also found to be effective in stimulating adiponectin and PPAR-γ mRNA upregulation at 50 µg/ml. CONCLUSION SDF7 exhibited good lipogenesis, adiponectinesis and glucose uptake stimulatory properties on 3T3-F442a adipocytes.
Collapse
Affiliation(s)
- Joo Ee Beh
- Department of Microbiology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | | | | | | | | | | | | | | |
Collapse
|
29
|
Bakke J, Bettaieb A, Nagata N, Matsuo K, Haj FG. Regulation of the SNARE-interacting protein Munc18c tyrosine phosphorylation in adipocytes by protein-tyrosine phosphatase 1B. Cell Commun Signal 2013; 11:57. [PMID: 23937695 PMCID: PMC3751566 DOI: 10.1186/1478-811x-11-57] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 08/06/2013] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Protein-tyrosine phosphatase 1B (PTP1B) is a physiological regulator of insulin signaling and adiposity and is a drug target for the treatment of obesity and diabetes. The molecular mechanisms underlying PTP1B metabolic actions require additional investigation. RESULTS Herein, we identify Munc18c as a novel PTP1B substrate in adipocytes and in vivo. We demonstrate nutritional regulation of Munc18c in adipose tissue revealing decreased expression upon high fat feeding. In addition, PTP1B deficiency leads to elevated Munc18c tyrosine phosphorylation and dissociation from syntaxin4. At the molecular level, we identify Munc18c Tyr218/219 and Tyr521 as key residues that mediate Munc18c interaction with PTP1B. Further, we uncover an essential role of Munc18c total tyrosine phosphorylation in general, and Tyr218/219 and Tyr521 in particular, in regulating its interactions and glucose uptake in adipocytes. CONCLUSION In conclusion, our findings identify PTP1B as the first known tyrosine phosphatase for Munc18c and a regulator of its phosphorylation and function in adipocytes.
Collapse
Affiliation(s)
- Jesse Bakke
- Nutrition Department, University of California Davis, One Shields Ave, 3135 Meyer Hall, Davis, CA 95616, USA
| | | | | | | | | |
Collapse
|
30
|
Sadacca LA, Bruno J, Wen J, Xiong W, McGraw TE. Specialized sorting of GLUT4 and its recruitment to the cell surface are independently regulated by distinct Rabs. Mol Biol Cell 2013; 24:2544-57. [PMID: 23804653 PMCID: PMC3744946 DOI: 10.1091/mbc.e13-02-0103] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
RAB10 and RAB14 function at sequential steps of insulin-stimulated GLUT4 translocation to the plasma membrane. RAB14 functions upstream of RAB10 in GLUT4 sorting to the specialized transport vesicles, and RAB10 and its GAP protein comprise the main signaling module that regulates the accumulation of GLUT4 transport vesicles at the plasma membrane. Adipocyte glucose uptake in response to insulin is essential for physiological glucose homeostasis: stimulation of adipocytes with insulin results in insertion of the glucose transporter GLUT4 into the plasma membrane and subsequent glucose uptake. Here we establish that RAB10 and RAB14 are key regulators of GLUT4 trafficking that function at independent, sequential steps of GLUT4 translocation. RAB14 functions upstream of RAB10 in the sorting of GLUT4 to the specialized transport vesicles that ferry GLUT4 to the plasma membrane. RAB10 and its GTPase-activating protein (GAP) AS160 comprise the principal signaling module downstream of insulin receptor activation that regulates the accumulation of GLUT4 transport vesicles at the plasma membrane. Although both RAB10 and RAB14 are regulated by the GAP activity of AS160 in vitro, only RAB10 is under the control of AS160 in vivo. Insulin regulation of the pool of RAB10 required for GLUT4 translocation occurs through regulation of AS160, since activation of RAB10 by DENND4C, its GTP exchange factor, does not require insulin stimulation.
Collapse
Affiliation(s)
- L Amanda Sadacca
- Department of Biochemistry, Weill Cornell Medical College, Cornell University, New York, NY 10065, USA
| | | | | | | | | |
Collapse
|
31
|
Catimel B, Kapp E, Yin MX, Gregory M, Wong LSM, Condron M, Church N, Kershaw N, Holmes AB, Burgess AW. The PI(3)P interactome from a colon cancer cell. J Proteomics 2013; 82:35-51. [DOI: 10.1016/j.jprot.2013.01.031] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 12/21/2012] [Accepted: 01/24/2013] [Indexed: 02/07/2023]
|
32
|
Munc18b is an essential gene in mice whose expression is limiting for secretion by airway epithelial and mast cells. Biochem J 2012; 446:383-94. [PMID: 22694344 PMCID: PMC3430001 DOI: 10.1042/bj20120057] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Airway mucin secretion and MC (mast cell) degranulation must be tightly controlled for homoeostasis of the lungs and immune system respectively. We found the exocytic protein Munc18b to be highly expressed in mouse airway epithelial cells and MCs, and localized to the apical pole of airway secretory cells. To address its functions, we created a mouse with a severely hypomorphic Munc18b allele such that protein expression in heterozygotes was reduced by ~50%. Homozygous mutant mice were not viable, but heterozygotes showed a ~50% reduction in stimulated release of mucin from epithelial cells and granule contents from MCs. The defect in MCs affected only regulated secretion and not constitutive or transporter-mediated secretion. The severity of passive cutaneous anaphylaxis was also reduced by ~50%, showing that reduction of Munc18b expression results in an attenuation of physiological responses dependent on MC degranulation. The Munc18b promoter is controlled by INR (initiator), Sp1 (specificity protein 1), Ets, CRE (cAMP-response element), GRE (glucocorticoid-response element), GATA and E-box elements in airway epithelial cells; however, protein levels did not change during mucous metaplasia induced by allergic inflammation. Taken together, the results of the present study identify Munc18b as an essential gene that is a limiting component of the exocytic machinery of epithelial cells and MCs.
Collapse
|
33
|
Abstract
GLUT4 is an insulin-regulated glucose transporter that is responsible for insulin-regulated glucose uptake into fat and muscle cells. In the absence of insulin, GLUT4 is mainly found in intracellular vesicles referred to as GLUT4 storage vesicles (GSVs). Here, we summarise evidence for the existence of these specific vesicles, how they are sequestered inside the cell and how they undergo exocytosis in the presence of insulin. In response to insulin stimulation, GSVs fuse with the plasma membrane in a rapid burst and in the continued presence of insulin GLUT4 molecules are internalised and recycled back to the plasma membrane in vesicles that are distinct from GSVs and probably of endosomal origin. In this Commentary we discuss evidence that this delivery process is tightly regulated and involves numerous molecules. Key components include the actin cytoskeleton, myosin motors, several Rab GTPases, the exocyst, SNARE proteins and SNARE regulators. Each step in this process is carefully orchestrated in a sequential and coupled manner and we are beginning to dissect key nodes within this network that determine vesicle-membrane fusion in response to insulin. This regulatory process clearly involves the Ser/Thr kinase AKT and the exquisite manner in which this single metabolic process is regulated makes it a likely target for lesions that might contribute to metabolic disease.
Collapse
Affiliation(s)
- Jacqueline Stöckli
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, New South Wales 2010, Australia
| | | | | |
Collapse
|
34
|
Abstract
Class II isoforms of PI3K (phosphoinositide 3-kinase) are still the least investigated and characterized of all PI3Ks. In the last few years, an increased interest in these enzymes has improved our understanding of their cellular functions. However, several questions still remain unanswered on their mechanisms of activation, their specific downstream effectors and their contribution to physiological processes and pathological conditions. Emerging evidence suggests that distinct PI3Ks activate different signalling pathways, indicating that their functional roles are probably not redundant. In the present review, we discuss the recent advances in our understanding of mammalian class II PI3Ks and the evidence suggesting their involvement in human diseases.
Collapse
|
35
|
Lorentz A, Baumann A, Vitte J, Blank U. The SNARE Machinery in Mast Cell Secretion. Front Immunol 2012; 3:143. [PMID: 22679448 PMCID: PMC3367400 DOI: 10.3389/fimmu.2012.00143] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 05/17/2012] [Indexed: 11/13/2022] Open
Abstract
Mast cells are known as inflammatory cells which exert their functions in allergic and anaphylactic reactions by secretion of numerous inflammatory mediators. During an allergic response, the high-affinity IgE receptor, FcεRI, becomes cross-linked by receptor-bound IgE and antigen resulting in immediate release of pre-synthesized mediators – stored in granules – as well as in de novo synthesis of various mediators like cytokines and chemokines. Soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptors (SNARE) proteins were found to play a central role in regulating membrane fusion events during exocytosis. In addition, several accessory regulators like Munc13, Munc18, Rab GTPases, secretory carrier membrane proteins, complexins, or synaptotagmins were found to be involved in membrane fusion. In this review we summarize our current knowledge about the SNARE machinery and its mechanism of action in mast cell secretion.
Collapse
Affiliation(s)
- Axel Lorentz
- Department of Nutritional Medicine, University of Hohenheim Stuttgart, Germany
| | | | | | | |
Collapse
|
36
|
Abstract
Despite daily fasting and feeding, plasma glucose levels are normally maintained within a narrow range owing to the hormones insulin and glucagon. Insulin increases glucose uptake into fat and muscle cells through the regulated trafficking of vesicles that contain glucose transporter type 4 (GLUT4). New insights into insulin signalling reveal that phosphorylation events initiated by the insulin receptor regulate key GLUT4 trafficking proteins, including small GTPases, tethering complexes and the vesicle fusion machinery. These proteins, in turn, control GLUT4 movement through the endosomal system, formation and retention of specialized GLUT4 storage vesicles and targeted exocytosis of these vesicles. Understanding these processes may help to explain the development of insulin resistance in type 2 diabetes and provide new potential therapeutic targets.
Collapse
|
37
|
Rivero R, Garin CA, Ormazabal P, Silva A, Carvajal R, Gabler F, Romero C, Vega M. Protein expression of PKCZ (Protein Kinase C Zeta), Munc18c, and Syntaxin-4 in the insulin pathway in endometria of patients with polycystic ovary syndrome (PCOS). Reprod Biol Endocrinol 2012; 10:17. [PMID: 22390153 PMCID: PMC3317829 DOI: 10.1186/1477-7827-10-17] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 03/05/2012] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND Polycystic Ovary Syndrome (PCOS) is an endocrine-metabolic disorder commonly associated with insulin resistance (IR). Previous studies indicate about the expression of molecules involved in the insulin pathway in endometria of women with PCOS-IR. Therefore, the aim of the present study was to evaluate the effect of insulin and testosterone in the expression of these proteins in the endometria and immortal endometrial stromal cell line (T-HESCs). METHODS We examined the protein levels of Munc18c, PKC zeta, phospho-PKC Zeta, and Syntaxin-4. Protein levels were assessed by Western Blot and/or immunohistochemistry in proliferative endometria (NPE = 6) and in PCOS endometria with insulin resistance (PCOSE-IR = 6). We also evaluated whether high concentrations of insulin (100 nM) and/or testosterone (100 nM), during a 24 h stimulatory period, affected the expression of these proteins in an immortal endometrial stromal cell line (T-HESCs). Once stimulated, proteins were extracted from cells and were assessed by Western Blot analysis. Immunocytochemistry was performed to detect AR in T-HESC cells. RESULTS Western Blot data showed decreased expression (p < 0,05) of Munc18c and phospho-PKC Zeta in PCOS-IR endometria (PCOSE-IR) with respect to the control (NPE). In the in vitro study, Western Blot analysis showed decreased levels of Munc18c, PKC Zeta and phospho-PKC Zeta with the different hormonal treatments when compared to the control condition (no hormonal stimulation) (p < 0,05). The AR was present in the endometrial stromal cell line (T-HESC). CONCLUSION The conditions of hyperinsulinism and hyperandrogenism present in PCOS-IR patients modulate the expression and/or phosphorylation of the proteins involved in the insulin pathway at the endometrial level. These data extend to the T-HESCs cells results, where insulin and testosterone exert an effect on both the expression and phosphorylation of proteins present in the pathway.
Collapse
Affiliation(s)
- Rodrigo Rivero
- Endocrinology and Reproductive Biology Laboratory, Clinical Hospital University of Chile (HCUCH), Santiago, Chile
| | - Claire-Alix Garin
- Endocrinology and Reproductive Biology Laboratory, Clinical Hospital University of Chile (HCUCH), Santiago, Chile
| | - Paulina Ormazabal
- Endocrinology and Reproductive Biology Laboratory, Clinical Hospital University of Chile (HCUCH), Santiago, Chile
| | - Andrea Silva
- Endocrinology and Reproductive Biology Laboratory, Clinical Hospital University of Chile (HCUCH), Santiago, Chile
| | - Rodrigo Carvajal
- Endocrinology and Reproductive Biology Laboratory, Clinical Hospital University of Chile (HCUCH), Santiago, Chile
- Department of Obstetrics and Gynaecology, School of Medicine, University of Chile, Santiago, Chile
| | - Fernando Gabler
- Department of Pathology, School of Medicine, University of Chile, Santiago, Chile
| | - Carmen Romero
- Endocrinology and Reproductive Biology Laboratory, Clinical Hospital University of Chile (HCUCH), Santiago, Chile
- Department of Obstetrics and Gynaecology, School of Medicine, University of Chile, Santiago, Chile
| | - Margarita Vega
- Endocrinology and Reproductive Biology Laboratory, Clinical Hospital University of Chile (HCUCH), Santiago, Chile
- Department of Obstetrics and Gynaecology, School of Medicine, University of Chile, Santiago, Chile
| |
Collapse
|
38
|
Wei Z, Peterson JM, Lei X, Cebotaru L, Wolfgang MJ, Baldeviano GC, Wong GW. C1q/TNF-related protein-12 (CTRP12), a novel adipokine that improves insulin sensitivity and glycemic control in mouse models of obesity and diabetes. J Biol Chem 2012; 287:10301-10315. [PMID: 22275362 DOI: 10.1074/jbc.m111.303651] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Despite the prevalence of insulin resistance and type 2 diabetes mellitus, their underlying mechanisms remain incompletely understood. Many secreted endocrine factors and the intertissue cross-talk they mediate are known to be dysregulated in type 2 diabetes mellitus. Here, we describe CTRP12, a novel adipokine with anti-diabetic actions. The mRNA and circulating levels of CTRP12 were decreased in a mouse model of obesity, but its expression in adipocytes was increased by the anti-diabetic drug rosiglitazone. A modest rise in circulating levels of CTRP12 by recombinant protein administration was sufficient to lower blood glucose in wild-type, leptin-deficient ob/ob, and diet-induced obese mice. A short term elevation of serum CTRP12 by adenovirus-mediated expression improved glucose tolerance and insulin sensitivity, normalized hyperglycemia and hyperinsulinemia, and lowered postprandial insulin resistance in obese and diabetic mice. CTRP12 improves insulin sensitivity in part by enhancing insulin signaling in the liver and adipose tissue. Further, CTRP12 also acts in an insulin-independent manner; in cultured hepatocytes and adipocytes, CTRP12 directly activated the PI3K-Akt signaling pathway to suppress gluconeogenesis and promote glucose uptake, respectively. Collectively, these data establish CTRP12 as a novel metabolic regulator linking adipose tissue to whole body glucose homeostasis through insulin-dependent and independent mechanisms.
Collapse
Affiliation(s)
- Zhikui Wei
- Departments of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Center for Metabolism and Obesity Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Jonathan M Peterson
- Departments of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Center for Metabolism and Obesity Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Xia Lei
- Departments of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Center for Metabolism and Obesity Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Liudmila Cebotaru
- Departments of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Departments of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Michael J Wolfgang
- Center for Metabolism and Obesity Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Departments of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - G Christian Baldeviano
- Departments of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - G William Wong
- Departments of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Center for Metabolism and Obesity Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
| |
Collapse
|
39
|
Abstract
Phosphoinositides (PIs) are minor components of cellular membranes that play critical regulatory roles in several intracellular functions. This chapter describes the main enzymes regulating the turnover of each of the seven PIs in mammalian cells and introduces to some of their intracellular functions and to some evidences of their involvement in human diseases. Due to the complex interrelation between the distinct PIs and the plethora of functions that they can regulate inside a cell, this chapter is not meant to be a comprehensive coverage of all aspects of PI signalling but rather an introduction to this complex signalling field. For more details of their regulation/functions and extensive description of their intracellular roles, more detailed reviews are suggested on each single topic.
Collapse
|
40
|
Ju X, Cui Q, Zhang M, Wang W, Jiang J, Chang Y, Wang K, Yang T, Zhou H. Human cholesteryl ester transfer protein enhances insulin-mediated glucose uptake in adipocytes. Life Sci 2011; 89:479-84. [PMID: 21816162 DOI: 10.1016/j.lfs.2011.07.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Revised: 07/08/2011] [Accepted: 07/16/2011] [Indexed: 10/17/2022]
Abstract
AIMS Adipose tissue plays an important role in the pathogenesis of insulin resistance, obesity, and Type-2 diabetes. Human adipocytes express abundant cholesteryl ester transfer protein (CETP). However, the function and role of CETP in regulating lipoprotein metabolism are mostly unknown. In this study, we examined whether CETP affected the insulin-mediated responses in adipocytes. MAIN METHODS Because mouse 3T3-L1 preadipocytes do not express CETP, we established a stable cell line expressing human CETP by transfecting the cells with pcDNA3.1/human CETP. We used a standard approach to differentiate the cells into mature adipocytes, and we examined the cholesterol balance and insulin responses. KEY FINDINGS The human CETP stable cell line expressed stable levels of CETP without affecting the expression of either peroxisome proliferator-activated receptor-gamma (PPARγ) or glucose transporter-4 (GLUT4) throughout cell differentiation. CETP expression significantly increased the level of both total and free cholesterol in the mature adipocytes. Upon insulin stimulation, CETP expressing cells had significantly higher protein kinase B (Akt) phosphorylation and 2-(3)H-deoxyglucose uptake, as compared with 3T3-L1 cells and cells transfected with control vector. SIGNIFICANCE Human CETP expression increased cellular cholesterol levels and enhanced insulin-stimulated Akt phosphorylation and glucose uptake in adipocytes. Thus, CETP may modulate glucose metabolism and insulin action in addition to its effects on lipoprotein metabolism.
Collapse
Affiliation(s)
- Xianxia Ju
- Department of Endocrinology, The First Affiliated Hospital, Nanjing Medical University, Nanjing, PR China
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Aran V, Bryant NJ, Gould GW. Tyrosine phosphorylation of Munc18c on residue 521 abrogates binding to Syntaxin 4. BMC BIOCHEMISTRY 2011; 12:19. [PMID: 21548926 PMCID: PMC3103433 DOI: 10.1186/1471-2091-12-19] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Accepted: 05/06/2011] [Indexed: 11/10/2022]
Abstract
Background Insulin stimulates exocytosis of GLUT4 from an intracellular store to the cell surface of fat and muscle cells. Fusion of GLUT4-containing vesicles with the plasma membrane requires the SNARE proteins Syntaxin 4, VAMP2 and the regulatory Sec1/Munc18 protein, Munc18c. Syntaxin 4 and Munc18c form a complex that is disrupted upon insulin treatment of adipocytes. Munc18c is tyrosine phosphorylated in response to insulin in these cells. Here, we directly test the hypothesis that tyrosine phosphorylation of Munc18c is responsible for the observed insulin-dependent abrogation of binding between Munc18c and Syntaxin 4. Results We show that Munc18c is directly phosphorylated by recombinant insulin receptor tyrosine kinase in vitro. Using pull-down assays, we show that phosphorylation abrogates binding of Munc18c to both Syntaxin 4 and the v-SNARE VAMP2, as does the introduction of a phosphomimetic mutation into Munc18c (Y521E). Conclusion Our data indicate that insulin-stimulated tyrosine phosphorylation of Munc18c impairs the ability of Munc18c to bind its cognate SNARE proteins, and may therefore represent a regulatory step in GLUT4 traffic.
Collapse
Affiliation(s)
- Veronica Aran
- Henry Wellcome Laboratory of Cell Biology, Davidson Building, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 9QQ, UK
| | | | | |
Collapse
|
42
|
Mazza S, Maffucci T. Class II phosphoinositide 3-kinase C2alpha: what we learned so far. INTERNATIONAL JOURNAL OF BIOCHEMISTRY AND MOLECULAR BIOLOGY 2011; 2:168-182. [PMID: 21968800 PMCID: PMC3180093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Accepted: 04/20/2011] [Indexed: 05/31/2023]
Abstract
More than fifteen years after the first identification of a class II isoform of phosphoinositide 3-kinase (PI3K) in Drosophila melanoǵaster this subfamily remains the most enigmatic among all PI3Ks. What are the functions of these enzymes? What are their mechanisms of activation? Which downstream effectors are specifically regulated by these isoforms? Are class I and class II PI3Ks redundant or do they control different intracellular processes? And, more important, do class II PI3Ks have a role in human diseases? The recent increased interest on class II PI3Ks has started providing some answers to these questions but still a lot needs to be done to completely uncover the contribution of these enzymes to physiological processes and possibly to pathological conditions. Here we will summarise the recent findings on the alpha isoform of mammalian class II PI3Ks (PI3K-C2α ) and we will discuss the potential involvement of this enzyme in human diseases.
Collapse
Affiliation(s)
- Simona Mazza
- Queen Mary University of London, Barts and The London School of Medicine and Dentistry, Blizard Institute of Cell and Molecular Science, Centre for Diabetes Inositide Signalling Group, London El 2AT UK
| | | |
Collapse
|
43
|
Huang G, Ge G, Wang D, Gopalakrishnan B, Butz DH, Colman RJ, Nagy A, Greenspan DS. α3(V) collagen is critical for glucose homeostasis in mice due to effects in pancreatic islets and peripheral tissues. J Clin Invest 2011; 121:769-83. [PMID: 21293061 DOI: 10.1172/jci45096] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Accepted: 11/10/2010] [Indexed: 01/14/2023] Open
Abstract
Collagen V, broadly expressed as α1(V)2 α2(V) heterotrimers that regulate collagen fibril geometry and strength, also occurs in some tissues, such as white adipose tissue (WAT), pancreatic islets, and skeletal muscle, as the poorly characterized α1(V) α2(V) α3(V) heterotrimer. Here, we investigate the role of α3(V) collagen chains by generating mice with a null allele of the α3(V) gene Col5a3 (Col5a3–/– mice). Female Col5a3–/– mice had reduced dermal fat and were resistant to high-fat diet–induced weight gain. Male and female mutant mice were glucose intolerant, insulin-resistant, and hyperglycemic, and these metabolic defects worsened with age. Col5a3–/– mice demonstrated decreased numbers of pancreatic islets, which were more susceptible to streptozotocin-induced apoptosis, and islets isolated from mutant mice displayed blunted glucose-stimulated insulin secretion. Moreover, Col5a3–/– WAT and skeletal muscle were defective in glucose uptake and mobilization of intracellular GLUT4 glucose transporter to the plasma membrane in response to insulin. Our results underscore the emerging view of the importance of ECM to the microenvironments that inform proper development/functioning of specialized cells, such as adipocytes, β cells, and skeletal muscle.
Collapse
Affiliation(s)
- Guorui Huang
- Department of Cell and Regenerative Biology, University of Wisconsin, Madison, Wisconsin 53706, USA
| | | | | | | | | | | | | | | |
Collapse
|
44
|
Abstract
Delivery of the glucose transporter type 4 (GLUT4) from an intracellular location to the cell surface in response to insulin represents a specialized form of membrane traffic, known to be impaired in the disease states of insulin resistance and type 2 diabetes. Like all membrane trafficking events, this translocation of GLUT4 requires members of the SNARE family of proteins. Here, we discuss two SNARE complexes that have been implicated in insulin-regulated GLUT4 traffic: one regulating the final delivery of GLUT4 to the cell surface in response to insulin and the other controlling GLUT4's intracellular trafficking.
Collapse
Affiliation(s)
- Nia J Bryant
- Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell and Systems Biology, Davidson Building, College of Medicine, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | | |
Collapse
|
45
|
Torres J, Funk HM, Zegers MMP, ter Beest MBA. The syntaxin 4 N terminus regulates its basolateral targeting by munc18c-dependent and -independent mechanisms. J Biol Chem 2011; 286:10834-46. [PMID: 21278252 DOI: 10.1074/jbc.m110.186668] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
To generate and maintain epithelial cell polarity, specific sorting of proteins into vesicles destined for the apical and basolateral domain is required. Syntaxin 3 and 4 are apical and basolateral SNARE proteins important for the specificity of vesicle fusion at the apical and basolateral plasma membrane domains, respectively, but how these proteins are specifically targeted to these domains themselves is unclear. Munc18/SM proteins are potential regulators of this process. Like syntaxins, they are crucial for exocytosis and vesicle fusion. However, how munc18c and syntaxin 4 regulate the function of each other is unclear. Here, we investigated the requirement of syntaxin 4 in the delivery of basolateral membrane and secretory proteins, the basolateral targeting of syntaxin 4, and the role of munc18c in this targeting. Depletion of syntaxin 4 resulted in significant reduction of basolateral targeting, suggesting no compensation by other syntaxin forms. Mutational analysis identified amino acids Leu-25 and to a lesser extent Val-26 as essential for correct localization of syntaxin 4. Recently, it was shown that the N-terminal peptide of syntaxin 4 is involved in binding to munc18c. A mutation in this region that affects munc18c binding shows that munc18c binding is required for stabilization of syntaxin 4 at the plasma membrane but not for its correct targeting. We conclude that the N terminus serves two functions in membrane targeting. First, it harbors the sorting motif, which targets syntaxin 4 basolaterally in a munc18c-independent manner and second, it allows for munc18c binding, which stabilizes the protein in a munc18c-dependent manner.
Collapse
Affiliation(s)
- Jacqueline Torres
- Department of Surgery, The University of Chicago, Chicago, Illinois 60637, USA
| | | | | | | |
Collapse
|
46
|
Blank U. The mechanisms of exocytosis in mast cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 716:107-22. [PMID: 21713654 DOI: 10.1007/978-1-4419-9533-9_7] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Upon activation through high affinity IgE receptors (FcεRI), mast cells (MCs) can release up to 100% of their content of preformed mediators stored in cytoplasmic secretory granules by compound exocytosis. This causes Type I immediate hypersensitivity reactions and, in the case of inappropriate activation by allergens, the symptoms of allergy. Recent work has uncovered a central role of SNARE (Soluble N-ethylmaleimide-Sensitive Factor (NSF) Attachment Protein (SNAP) Receptors) proteins in regulating the numerous membrane fusion events during exocytosis. This has defined a series of new molecular actors in MC exocytosis that participate in the regulation of membrane fusion and the connection of the fusion machinery with early signaling events. The purpose of this chapter is to describe these proteins and provide a brief overview on their mechanism of action.
Collapse
|
47
|
Brandt N, De Bock K, Richter EA, Hespel P. Cafeteria diet-induced insulin resistance is not associated with decreased insulin signaling or AMPK activity and is alleviated by physical training in rats. Am J Physiol Endocrinol Metab 2010; 299:E215-24. [PMID: 20484011 DOI: 10.1152/ajpendo.00098.2010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Excess energy intake via a palatable low-fat diet (cafeteria diet) is known to induce obesity and glucose intolerance in rats. However, the molecular mechanisms behind this adaptation are not known, and it is also not known whether exercise training can reverse it. Male Wistar rats were assigned to 12-wk intervention groups: chow-fed controls (CON), cafeteria diet (CAF), and cafeteria diet plus swimming exercise during the last 4 wk (CAF(TR)). CAF feeding led to increased body weight (16%, P < 0.01) and increased plasma glucose (P < 0.05) and insulin levels (P < 0.01) during an IVGTT, which was counteracted by training. In the perfused hindlimb, insulin-stimulated glucose transport in red gastrocnemius muscle was completely abolished in CAF and rescued by exercise training. Apart from a tendency toward an approximately 20% reduction in both basal and insulin-stimulated Akt Ser(473) phosphorylation (P = 0.051) in the CAF group, there were no differences in insulin signaling (IR Tyr(1150/1151), PI 3-kinase activity, Akt Thr(308), TBC1D4 Thr(642), GSK3-alpha/beta Ser(21/9)) or changes in AMPKalpha1 or -alpha2, GLUT4, Munc18c, or syntaxin 4 protein expression or in phosphorylation of AMPK Thr(172) among the groups. In conclusion, surplus energy intake of a palatable but low-fat cafeteria diet resulted in obesity and insulin resistance that was rescued by exercise training. Interestingly, insulin resistance was not accompanied by major defects in the insulin-signaling cascade or in altered AMPK expression or phosphorylation. Thus, compared with previous studies of high-fat feeding, where insulin signaling is significantly impaired, the mechanism by which CAF diet induces insulin resistance seems different.
Collapse
Affiliation(s)
- Nina Brandt
- Molecular Physiology Group, Department of Exercise and Sport Sciences, Copenhagen Muscle Research Centre, University of Copenhagen, 13 Universitetsparken, Copenhagen, Denmark
| | | | | | | |
Collapse
|
48
|
Boström P, Andersson L, Vind B, Håversen L, Rutberg M, Wickström Y, Larsson E, Jansson PA, Svensson MK, Brånemark R, Ling C, Beck-Nielsen H, Borén J, Højlund K, Olofsson SO. The SNARE protein SNAP23 and the SNARE-interacting protein Munc18c in human skeletal muscle are implicated in insulin resistance/type 2 diabetes. Diabetes 2010; 59:1870-8. [PMID: 20460426 PMCID: PMC2911056 DOI: 10.2337/db09-1503] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Accepted: 04/30/2010] [Indexed: 12/18/2022]
Abstract
OBJECTIVE Our previous studies suggest that the SNARE protein synaptosomal-associated protein of 23 kDa (SNAP23) is involved in the link between increased lipid levels and insulin resistance in cardiomyocytes. The objective was to determine whether SNAP23 may also be involved in the known association between lipid accumulation in skeletal muscle and insulin resistance/type 2 diabetes in humans, as well as to identify a potential regulator of SNAP23. RESEARCH DESIGN AND METHODS We analyzed skeletal muscle biopsies from patients with type 2 diabetes and healthy, insulin-sensitive control subjects for expression (mRNA and protein) and intracellular localization (subcellular fractionation and immunohistochemistry) of SNAP23, and for expression of proteins known to interact with SNARE proteins. Insulin resistance was determined by a euglycemic hyperinsulinemic clamp. Potential mechanisms for regulation of SNAP23 were also investigated in the skeletal muscle cell line L6. RESULTS We showed increased SNAP23 levels in skeletal muscle from patients with type 2 diabetes compared with that from lean control subjects. Moreover, SNAP23 was redistributed from the plasma membrane to the microsomal/cytosolic compartment in the patients with the type 2 diabetes. Expression of the SNARE-interacting protein Munc18c was higher in skeletal muscle from patients with type 2 diabetes. Studies in L6 cells showed that Munc18c promoted the expression of SNAP23. CONCLUSIONS We have translated our previous in vitro results into humans by showing that there is a change in the distribution of SNAP23 to the interior of the cell in skeletal muscle from patients with type 2 diabetes. We also showed that Munc18c is a potential regulator of SNAP23.
Collapse
Affiliation(s)
- Pontus Boström
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Linda Andersson
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Birgitte Vind
- Diabetes Research Centre, Department of Endocrinology, Odense University Hospital, Odense, Denmark
| | - Liliana Håversen
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Mikael Rutberg
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Ylva Wickström
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Erik Larsson
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Per-Anders Jansson
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Maria K. Svensson
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Richard Brånemark
- Department of Orthopedic Surgery, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Charlotte Ling
- Department of Clinical Sciences CRC, University Hospital of Malmö, Lund University, Sweden
| | - Henning Beck-Nielsen
- Diabetes Research Centre, Department of Endocrinology, Odense University Hospital, Odense, Denmark
| | - Jan Borén
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Kurt Højlund
- Diabetes Research Centre, Department of Endocrinology, Odense University Hospital, Odense, Denmark
| | - Sven-Olof Olofsson
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Sahlgrenska University Hospital, Göteborg, Sweden
| |
Collapse
|
49
|
Jewell JL, Oh E, Thurmond DC. Exocytosis mechanisms underlying insulin release and glucose uptake: conserved roles for Munc18c and syntaxin 4. Am J Physiol Regul Integr Comp Physiol 2010; 298:R517-31. [PMID: 20053958 DOI: 10.1152/ajpregu.00597.2009] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Type 2 diabetes has been coined "a two-hit disease," as it involves specific defects of glucose-stimulated insulin secretion from the pancreatic beta cells in addition to defects in peripheral tissue insulin action required for glucose uptake. Both of these processes, insulin secretion and glucose uptake, are mediated by SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein core complexes composed of syntaxin, SNAP-23/25, and VAMP proteins. The SNARE core complex is regulated by the Sec1/Munc18 (SM) family of proteins, which selectively bind to their cognate syntaxin isoforms with high affinity. The process of insulin secretion uses multiple Munc18-syntaxin isoform pairs, whereas insulin action in the peripheral tissues appears to use only the Munc18c-syntaxin 4 pair. Importantly, recent reports have linked obesity and Type 2 diabetes in humans with changes in protein levels and single nucleotide polymorphisms (SNPs) of Munc18 and syntaxin isoforms relevant to these exocytotic processes, although the molecular mechanisms underlying the observed phenotypes remain incomplete (5, 104, 144). Given the conservation of these proteins in two seemingly disparate processes and the need to design and implement novel and more effective clinical interventions, it will be vitally important to delineate the mechanisms governing these conserved SNARE-mediated exocytosis events. Thus, we provide here an up-to-date historical review of advancements in defining the roles and molecular mechanisms of Munc18-syntaxin complexes in the pathophysiology of Type 2 diabetes.
Collapse
Affiliation(s)
- Jenna L Jewell
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
| | | | | |
Collapse
|
50
|
Kawaguchi T, Tamori Y, Kanda H, Yoshikawa M, Tateya S, Nishino N, Kasuga M. The t-SNAREs syntaxin4 and SNAP23 but not v-SNARE VAMP2 are indispensable to tether GLUT4 vesicles at the plasma membrane in adipocyte. Biochem Biophys Res Commun 2010; 391:1336-41. [DOI: 10.1016/j.bbrc.2009.12.045] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Accepted: 12/10/2009] [Indexed: 12/31/2022]
|