1
|
Morrison LJ, Steketee PC, Tettey MD, Matthews KR. Pathogenicity and virulence of African trypanosomes: From laboratory models to clinically relevant hosts. Virulence 2023; 14:2150445. [PMID: 36419235 DOI: 10.1080/21505594.2022.2150445] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
African trypanosomes are vector-borne protozoa, which cause significant human and animal disease across sub-Saharan Africa, and animal disease across Asia and South America. In humans, infection is caused by variants of Trypanosoma brucei, and is characterized by varying rate of progression to neurological disease, caused by parasites exiting the vasculature and entering the brain. Animal disease is caused by multiple species of trypanosome, primarily T. congolense, T. vivax, and T. brucei. These trypanosomes also infect multiple species of mammalian host, and this complexity of trypanosome and host diversity is reflected in the spectrum of severity of disease in animal trypanosomiasis, ranging from hyperacute infections associated with mortality to long-term chronic infections, and is also a main reason why designing interventions for animal trypanosomiasis is so challenging. In this review, we will provide an overview of the current understanding of trypanosome determinants of infection progression and severity, covering laboratory models of disease, as well as human and livestock disease. We will also highlight gaps in knowledge and capabilities, which represent opportunities to both further our fundamental understanding of how trypanosomes cause disease, as well as facilitating the development of the novel interventions that are so badly needed to reduce the burden of disease caused by these important pathogens.
Collapse
Affiliation(s)
- Liam J Morrison
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK
| | - Pieter C Steketee
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK
| | - Mabel D Tettey
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Keith R Matthews
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| |
Collapse
|
2
|
Transfer of Proteins from Cultured Human Adipose to Blood Cells and Induction of Anabolic Phenotype Are Controlled by Serum, Insulin and Sulfonylurea Drugs. Int J Mol Sci 2023; 24:ijms24054825. [PMID: 36902257 PMCID: PMC10003403 DOI: 10.3390/ijms24054825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 02/10/2023] [Accepted: 02/27/2023] [Indexed: 03/06/2023] Open
Abstract
Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are anchored at the outer leaflet of eukaryotic plasma membranes (PMs) only by carboxy-terminal covalently coupled GPI. GPI-APs are known to be released from the surface of donor cells in response to insulin and antidiabetic sulfonylureas (SUs) by lipolytic cleavage of the GPI or upon metabolic derangement as full-length GPI-APs with the complete GPI attached. Full-length GPI-APs become removed from extracellular compartments by binding to serum proteins, such as GPI-specific phospholipase D (GPLD1), or insertion into the PMs of acceptor cells. Here, the interplay between the lipolytic release and intercellular transfer of GPI-APs and its potential functional impact was studied using transwell co-culture with human adipocytes as insulin-/SU-responsive donor cells and GPI-deficient erythroleukemia as acceptor cells (ELCs). Measurement of the transfer as the expression of full-length GPI-APs at the ELC PMs by their microfluidic chip-based sensing with GPI-binding α-toxin and GPI-APs antibodies and of the ELC anabolic state as glycogen synthesis upon incubation with insulin, SUs and serum yielded the following results: (i) Loss of GPI-APs from the PM upon termination of their transfer and decline of glycogen synthesis in ELCs, as well as prolongation of the PM expression of transferred GPI-APs upon inhibition of their endocytosis and upregulated glycogen synthesis follow similar time courses. (ii) Insulin and SUs inhibit both GPI-AP transfer and glycogen synthesis upregulation in a concentration-dependent fashion, with the efficacies of the SUs increasing with their blood glucose-lowering activity. (iii) Serum from rats eliminates insulin- and SU-inhibition of both GPI-APs' transfer and glycogen synthesis in a volume-dependent fashion, with the potency increasing with their metabolic derangement. (iv) In rat serum, full-length GPI-APs bind to proteins, among them (inhibited) GPLD1, with the efficacy increasing with the metabolic derangement. (v) GPI-APs are displaced from serum proteins by synthetic phosphoinositolglycans and then transferred to ELCs with accompanying stimulation of glycogen synthesis, each with efficacies increasing with their structural similarity to the GPI glycan core. Thus, both insulin and SUs either block or foster transfer when serum proteins are depleted of or loaded with full-length GPI-APs, respectively, i.e., in the normal or metabolically deranged state. The transfer of the anabolic state from somatic to blood cells over long distance and its "indirect" complex control by insulin, SUs and serum proteins support the (patho)physiological relevance of the intercellular transfer of GPI-APs.
Collapse
|
3
|
Biological Role of the Intercellular Transfer of Glycosylphosphatidylinositol-Anchored Proteins: Stimulation of Lipid and Glycogen Synthesis. Int J Mol Sci 2022; 23:ijms23137418. [PMID: 35806423 PMCID: PMC9267055 DOI: 10.3390/ijms23137418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/28/2022] [Accepted: 06/29/2022] [Indexed: 11/16/2022] Open
Abstract
Glycosylphosphatidylinositol-anchored proteins (GPI-APs), which are anchored at the outer leaflet of plasma membranes (PM) only by a carboxy-terminal GPI glycolipid, are known to fulfill multiple enzymic and receptor functions at the cell surface. Previous studies revealed that full-length GPI-APs with the complete GPI anchor attached can be released from and inserted into PMs in vitro. Moreover, full-length GPI-APs were recovered from serum, dependent on the age and metabolic state of rats and humans. Here, the possibility of intercellular control of metabolism by the intercellular transfer of GPI-APs was studied. Mutant K562 erythroleukemia (EL) cells, mannosamine-treated human adipocytes and methyl-ß-cyclodextrin-treated rat adipocytes as acceptor cells for GPI-APs, based on their impaired PM expression of GPI-APs, were incubated with full-length GPI-APs, prepared from rat adipocytes and embedded in micelle-like complexes, or with EL cells and human adipocytes with normal expression of GPI-APs as donor cells in transwell co-cultures. Increases in the amounts of full-length GPI-APs at the PM of acceptor cells as a measure of their transfer was assayed by chip-based sensing. Both experimental setups supported both the transfer and upregulation of glycogen (EL cells) and lipid (adipocytes) synthesis. These were all diminished by serum, serum GPI-specific phospholipase D, albumin, active bacterial PI-specific phospholipase C or depletion of total GPI-APs from the culture medium. Serum inhibition of both transfer and glycogen/lipid synthesis was counteracted by synthetic phosphoinositolglycans (PIGs), which closely resemble the structure of the GPI glycan core and caused dissociation of GPI-APs from serum proteins. Finally, large, heavily lipid-loaded donor and small, slightly lipid-loaded acceptor adipocytes were most effective in stimulating transfer and lipid synthesis. In conclusion, full-length GPI-APs can be transferred between adipocytes or between blood cells as well as between these cell types. Transfer and the resulting stimulation of lipid and glycogen synthesis, respectively, are downregulated by serum proteins and upregulated by PIGs. These findings argue for the (patho)physiological relevance of the intercellular transfer of GPI-APs in general and its role in the paracrine vs. endocrine (dys)regulation of metabolism, in particular. Moreover, they raise the possibility of the use of full-length GPI-APs as therapeutics for metabolic diseases.
Collapse
|
4
|
Müller GA. Insulin-like and mimetic molecules from non-mammalian organisms: potential relevance for drug discovery. Arch Physiol Biochem 2020; 126:420-429. [PMID: 30633571 DOI: 10.1080/13813455.2018.1551906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Insulin was first discovered in extracts of vertebrate pancreas during a focused search for a therapy for diabetes. Subsequent efforts to discover and isolate a similar active principle from yeast and plants driven by the hope to identify insulin-like/mimetic molecules with critical advantages in the pharmacokinetic profile and expenditure of production compared to authentic human insulin were not successful. As a consequence, it has generally been assumed that hormones evolved exclusively during course of the evolution of vertebrate endocrine organs, implying a rather recent origin. Concomitantly, the existence and physiological role of vertebrate hormones in lower multi- and unicellular eukaryotes have remained a rather controversial subject over decades, albeit there is some evidence that hormones and hormone-binding proteins resembling those of vertebrates are expressed in fungi and yeast. Past and recent findings on the existence of insulin-like and mimetic materials, such as the glucose tolerance factor, in lower eukaryotes, in particular Neurospora crassa and yeast, will be presented. These data provide further evidence for the provocative view that the evolutionary roots of the vertebrate endocrine system may be far more ancient than is generally believed and that the identification and characterisation of insulin-like/mimetic molecules from lower eukaryotes may be useful for future drug discovery efforts.
Collapse
Affiliation(s)
- Günter A Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center (HDC), Helmholtz Center München, Oberschleissheim, Germany
- Department Biology I, Genetics, Ludwig-Maximilians-University München, Planegg-Martinsried, Germany
| |
Collapse
|
5
|
Rendle P, Kassibawi F, Johnston K, Hart J, Cameron S, Falshaw A, Painter G, Loomes K. Synthesis and biological activities of d - chiro -inositol analogues with insulin-like actions. Eur J Med Chem 2016; 122:442-451. [DOI: 10.1016/j.ejmech.2016.06.047] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 06/23/2016] [Accepted: 06/25/2016] [Indexed: 10/21/2022]
|
6
|
Laganà AS, Rossetti P, Buscema M, La Vignera S, Condorelli RA, Gullo G, Granese R, Triolo O. Metabolism and Ovarian Function in PCOS Women: A Therapeutic Approach with Inositols. Int J Endocrinol 2016; 2016:6306410. [PMID: 27579037 PMCID: PMC4989075 DOI: 10.1155/2016/6306410] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 06/30/2016] [Indexed: 01/19/2023] Open
Abstract
Polycystic ovary syndrome (PCOS) is characterized by chronical anovulation and hyperandrogenism which may be present in a different degree of severity. Insulin-resistance and hyperinsulinemia are the main physiopathological basis of this syndrome and the failure of inositol-mediated signaling may concur to them. Myo (MI) and D-chiro-inositol (DCI), the most studied inositol isoforms, are classified as insulin sensitizers. In form of glycans, DCI-phosphoglycan and MI-phosphoglycan control key enzymes were involved in glucose and lipid metabolism. In form of phosphoinositides, they play an important role as second messengers in several cellular biological functions. Considering the key role played by insulin-resistance and androgen excess in PCOS patients, the insulin-sensitizing effects of both MI and DCI were tested in order to ameliorate symptoms and signs of this syndrome, including the possibility to restore patients' fertility. Accumulating evidence suggests that both isoforms of inositol are effective in improving ovarian function and metabolism in patients with PCOS, although MI showed the most marked effect on the metabolic profile, whereas DCI reduced hyperandrogenism better. The purpose of this review is to provide an update on inositol signaling and correlate data on biological functions of these multifaceted molecules, in view of a rational use for the therapy in women with PCOS.
Collapse
Affiliation(s)
- Antonio Simone Laganà
- Unit of Gynecology and Obstetrics, Department of Human Pathology in Adulthood and Childhood “G. Barresi”, University of Messina, 98125 Messina, Italy
- *Antonio Simone Laganà:
| | - Paola Rossetti
- Unit of Diabetology and Endocrino-Metabolic Diseases, Cannizzaro Hospital, 95126 Catania, Italy
| | - Massimo Buscema
- Unit of Diabetology and Endocrino-Metabolic Diseases, Cannizzaro Hospital, 95126 Catania, Italy
| | - Sandro La Vignera
- Department of Clinical and Experimental Medicine, Research Centre of Motor Activity and Metabolic Rehabilitation in Diabetes (CRAMD), University of Catania, 95124 Catania, Italy
| | - Rosita Angela Condorelli
- Department of Clinical and Experimental Medicine, Research Centre of Motor Activity and Metabolic Rehabilitation in Diabetes (CRAMD), University of Catania, 95124 Catania, Italy
| | - Giuseppe Gullo
- Unit of Gynecology and Obstetrics, Department of Human Pathology in Adulthood and Childhood “G. Barresi”, University of Messina, 98125 Messina, Italy
| | - Roberta Granese
- Unit of Gynecology and Obstetrics, Department of Human Pathology in Adulthood and Childhood “G. Barresi”, University of Messina, 98125 Messina, Italy
| | - Onofrio Triolo
- Unit of Gynecology and Obstetrics, Department of Human Pathology in Adulthood and Childhood “G. Barresi”, University of Messina, 98125 Messina, Italy
| |
Collapse
|
7
|
Tuvshintulga B, Batmagnai E, Bazarragchaa E, Dulam P, Sugar S, Battsetseg B. Detection and molecular characterization of rabies virus in Mongolia during 2008-2010. INTERNATIONAL JOURNAL OF ONE HEALTH 2015. [DOI: 10.14202/ijoh.2015.26-31] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
|
8
|
Suzuki S, Suzuki C, Hinokio Y, Ishigaki Y, Katagiri H, Kanzaki M, Azev VN, Chakraborty N, d'Alarcao M. Insulin-mimicking bioactivities of acylated inositol glycans in several mouse models of diabetes with or without obesity. PLoS One 2014; 9:e100466. [PMID: 24971987 PMCID: PMC4074071 DOI: 10.1371/journal.pone.0100466] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 05/27/2014] [Indexed: 12/13/2022] Open
Abstract
Insulin-mimetic species of low molecular weight are speculated to mediate some intracellular insulin actions. These inositol glycans, which are generated upon insulin stimulation from glycosylphosphatidylinositols, might control the activity of a multitude of insulin effector enzymes. Acylated inositol glycans (AIGs) are generated by cleavage of protein-free GPI precursors through the action of GPI-specific phospholipase C (GPI-PLC) and D (GPI-PLD). We synthesized AIGs (IG-1, IG-2, IG-13, IG-14, and IG-15) and then evaluated their insulin-mimicking bioactivities. IG-1 significantly stimulated glycogen synthesis and lipogenesis in 3T3-L1 adipocytes and rat isolated adipocytes dose-dependently. IG-2 significantly stimulated lipogenesis in rat isolated adipocytes dose-dependently. IG-15 also enhanced glycogen synthesis and lipogenesis in 3T3-L1 adipocytes. The administration of IG-1 decreased plasma glucose, increased glycogen content in liver and skeletal muscles and improved glucose tolerance in C57B6N mice with normal diets. The administration of IG-1 decreased plasma glucose in STZ-diabetic C57B6N mice. The treatment of IG-1 decreased plasma glucose, increased glycogen content in liver and skeletal muscles and improved glucose tolerance in C57B6N mice with high fat-diets and db/db mice. The long-term treatment of IG-1 decreased plasma glucose and reduced food intake and body weight in C57B6N mice with high fat-diets and ob/ob mice. Thus, IG-1 has insulin-mimicking bioactivities and improves glucose tolerance in mice models of diabetes with or without obesity.
Collapse
Affiliation(s)
- Susumu Suzuki
- Department of Diabetes and Metabolism, Tohoku University Hospital, Sendai, Japan
- Diabetes Center, Ohta Nishinouchi Hospital, Koriyama, Japan
- * E-mail:
| | - Chitose Suzuki
- Department of Diabetes and Metabolism, Tohoku University Hospital, Sendai, Japan
| | - Yoshinori Hinokio
- Department of Diabetes and Metabolism, Tohoku University Hospital, Sendai, Japan
| | - Yasushi Ishigaki
- Department of Diabetes and Metabolism, Tohoku University Hospital, Sendai, Japan
| | - Hideki Katagiri
- Department of Diabetes and Metabolism, Tohoku University Hospital, Sendai, Japan
| | - Makoto Kanzaki
- Graduate School of Biomedical Engineering, Tohoku University, Sendai, Japan
| | - Viatcheslav N. Azev
- Department of Chemistry, Tufts University, Medford, Massachusetts, United States of America
| | - Nilanjana Chakraborty
- Department of Chemistry, Tufts University, Medford, Massachusetts, United States of America
| | - Marc d'Alarcao
- Department of Chemistry, Tufts University, Medford, Massachusetts, United States of America
- Department of Chemistry, San Jose State University, San Jose, California, United States of America
| |
Collapse
|
9
|
Tsai YH, Liu X, Seeberger PH. Chemical biology of glycosylphosphatidylinositol anchors. Angew Chem Int Ed Engl 2012; 51:11438-56. [PMID: 23086912 DOI: 10.1002/anie.201203912] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Indexed: 01/21/2023]
Abstract
Glycosylphosphatidylinositols (GPIs) are complex glycolipids that are covalently linked to the C-terminus of proteins as a posttranslational modification. They anchor the attached protein to the cell membrane and are essential for normal functioning of eukaryotic cells. GPI-anchored proteins are structurally and functionally diverse. Many GPIs have been structurally characterized but comprehension of their biological functions, beyond the simple physical anchoring, remains largely speculative. Work on functional elucidation at a molecular level is still limited. This Review focuses on the roles of GPI unraveled by using synthetic molecules and summarizes the structural diversity of GPIs, as well as their biological and chemical syntheses.
Collapse
Affiliation(s)
- Yu-Hsuan Tsai
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14424 Potsdam, Germany
| | | | | |
Collapse
|
10
|
Tsai YH, Liu X, Seeberger PH. Chemische Biologie der Glycosylphosphatidylinosit-Anker. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201203912] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
11
|
Hecht ML, Tsai YH, Liu X, Wolfrum C, Seeberger PH. Synthetic inositol phosphoglycans related to GPI lack insulin-mimetic activity. ACS Chem Biol 2010; 5:1075-86. [PMID: 20825209 DOI: 10.1021/cb1002152] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Insulin signaling has been suggested, at least in part, to be affected by an insulin-mimetic species of low molecular weight. These inositol phosphoglycans (IPGs) are generated upon growth hormone/cytokine stimulation and control the activity of a multitude of insulin effector enzymes. The minimal structural requirements of IPGs for insulin-mimetic action have been debated. Two types of IPGs were suggested, and the IPG-A type resembles the core glycan of glycosylphosphatidylinositol (GPI)-anchors. In fact, purified GPI-anchors of lower eukaryotic origin have been shown to influence glucose homeostasis. To elucidate active IPGs, a collection of synthetic IPGs designed on the basis of previous reports of activity were tested for their insulin-mimetic activity. In vitro and ex vivo assays in rodent adipose tissue as well as in vivo analyses in mice were employed to test the synthetic IPGs. None of the IPGs we tested mimic insulin actions as determined by PKB/Akt phosphorylation and quantification of glucose transport and lipogenesis. Furthermore, none of the IPGs had any effect in in vivo insulin tolerance assays. In stark contrast to previous claims, we conclude that neither of the compounds tested is insulin-mimetic.
Collapse
Affiliation(s)
- Marie-Lyn Hecht
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
- Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
- Laboratory of Organic Chemistry, Swiss Federal Institute of Technology (ETH) Zurich, 8093 Zurich, Switzerland
- Competence Center for Systems Physiology and Metabolic Diseases, Zurich, 8093 Zurich, Switzerland
| | - Yu-Hsuan Tsai
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
- Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
| | - Xinyu Liu
- Laboratory of Organic Chemistry, Swiss Federal Institute of Technology (ETH) Zurich, 8093 Zurich, Switzerland
| | - Christian Wolfrum
- Competence Center for Systems Physiology and Metabolic Diseases, Zurich, 8093 Zurich, Switzerland
- Institute of Molecular Systems Biology, Swiss Federal Institute of Technology (ETH) Zurich, 8093 Zurich, Switzerland
| | - Peter H. Seeberger
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
- Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
- Laboratory of Organic Chemistry, Swiss Federal Institute of Technology (ETH) Zurich, 8093 Zurich, Switzerland
| |
Collapse
|
12
|
Raikwar NS, Bowen-Deeg RF, Du XS, Low MG, Deeg MA. Glycosylphosphatidylinositol-specific phospholipase D improves glucose tolerance. Metabolism 2010; 59:1413-20. [PMID: 20153004 DOI: 10.1016/j.metabol.2008.11.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Accepted: 11/18/2008] [Indexed: 01/02/2023]
Abstract
Insulin regulation of energy metabolism is complex and involves numerous signaling cascades. Insulin has been suggested to stimulate a phospholipase that cleaves glycosylphosphatidylinositols resulting in the generation of an inositol glycan that serves as an insulin mediator. To determine if glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) may play a role in glucose metabolism, we examined the effect of overexpressing GPI-PLD using adenovirus-mediated gene transfer in C57BL/6 mice. Overexpressing GPI-PLD was associated with a decrease in fasting glucose as well as an improvement in glucose tolerance as determined by an intraperitoneal glucose tolerance test. This effect to improve glucose tolerance does not result from an increase in insulin sensitivity, as overexpressing GPI-PLD does not alter the response to insulin. In contrast, the insulin response during the glucose tolerance test in GPI-PLD-overexpressing mice was increased. Overexpressing GPI-PLD in an insulinoma cell line enhanced glucose-stimulated insulin secretion, suggesting that enhanced insulin secretion in vivo may have contributed to the improved glucose tolerance.
Collapse
Affiliation(s)
- Nandita S Raikwar
- Department of Medicine and of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | | | | | | | | |
Collapse
|
13
|
Larner J, Brautigan DL, Thorner MO. D-chiro-inositol glycans in insulin signaling and insulin resistance. Mol Med 2010; 16:543-52. [PMID: 20811656 DOI: 10.2119/molmed.2010.00107] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 08/26/2010] [Indexed: 11/06/2022] Open
Abstract
Classical actions of insulin involve increased glucose uptake from the bloodstream and its metabolism in peripheral tissues, the most important and relevant effects for human health. However, nonoxidative and oxidative glucose disposal by activation of glycogen synthase (GS) and mitochondrial pyruvate dehydrogenase (PDH) remain incompletely explained by current models for insulin action. Since the discovery of insulin receptor Tyr kinase activity about 25 years ago, the dominant paradigm for intracellular signaling by insulin invokes protein phosphorylation downstream of the receptor and its primary Tyr phosphorylated substrates-the insulin receptor substrate family of proteins. This scheme accounts for most, but not all, intracellular actions of insulin. Essentially forgotten is the previous literature and continuing work on second messengers generated in cells in response to insulin. Treatment and even prevention of diabetes and metabolic syndrome will benefit from a more complete elucidation of cellular-signaling events activated by insulin, to include the actions of second messengers such as glycan molecules that contain D-chiro-inositol (DCI). The metabolism of DCI is associated with insulin sensitivity and resistance, supporting the concept that second messengers have a role in responses to and resistance to insulin.
Collapse
Affiliation(s)
- Joseph Larner
- Allomed Pharmaceuticals, Charlottesville, Virginia, United States of America.
| | | | | |
Collapse
|
14
|
Müller G, Schulz A, Dearey EA, Wetekam EM, Wied S, Frick W. Synthetic phosphoinositolglycans regulate lipid metabolism between rat adipocytes via release of GPI-protein-harbouring adiposomes. Arch Physiol Biochem 2010; 116:97-115. [PMID: 20515260 DOI: 10.3109/13813455.2010.485205] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
A novel molecular mechanism for the regulation of lipid metabolism by palmitate, H2O2 and the anti-diabetic sulfonylurea drug, glimepiride, in rat adipocytes was recently elucidated. It encompasses the translocation of the glycosylphosphatidylinositol-anchored (GPI-) and (c)AMP degrading enzymes Gce1 and CD73 from detergent-insoluble glycolipid-enriched microdomains of the plasma membrane (DIGs) to intracellular lipid droplets (LD), the incorporation of Gce1 and CD73 into vesicles (adiposomes) which are then released from donor adipocytes and finally the transfer of Gce1 and CD73 from the adiposomes to acceptor adipocytes, where they degrade (c)AMP at the LD surface. Here the stimulation of esterification and inhibition of lipolysis by synthetic phosphoinositolglycans (PIGs), such as PIG37, which represents the glycan component of the GPI anchor, are shown to be correlated to translocation from DIGs to LD and release into adiposomes of Gce1 and CD73. PIG37 actions were blocked upon disruption of DIGs, inactivation of PIG receptor and removal of adiposomes from the incubation medium as was true for those induced by palmitate, H2O2 or glimepiride. In contrast, only the latter actions were dependent on the GPI-specific phospholipase C (GPI-PLC), which may generate PIGs, or on exogenous PIG37 in case of inhibited GPI-PLC. At submaximal concentrations PIG37 and palmitate, H2O2 or glimepiride acted in synergistic fashion. These data suggest that PIGs provoke the transfer of GPI-proteins from DIGs via LD and adiposomes of donor adipocytes to acceptor adipocytes and thereby mediate the regulation of lipid metabolism by palmitate, H2O2 and glimepiride between adipocytes.
Collapse
Affiliation(s)
- Günter Müller
- Sanofi-Aventis Deutschland GmbH, Research & Development, 65926 Frankfurt am Main, Germany.
| | | | | | | | | | | |
Collapse
|
15
|
Goel M, Azev VN, d’Alarcao M. The biological activity of structurally defined inositol glycans. Future Med Chem 2009; 1:95-118. [PMID: 20390053 PMCID: PMC2853056 DOI: 10.4155/fmc.09.6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND: The inositol glycans (IGs) are glycolipid-derived carbohydrates produced by insulin-sensitive cells in response to insulin treatment. IGs exhibit an array of insulin-like activities including stimulation of lipogenesis, glucose transport and glycogen synthesis, suggesting that they may be involved in insulin signal transduction. However, because the natural IGs are structurally heterogeneous and difficult to purify to homogeneity, an understanding of the relationship between structure and biological activity has relied principally on synthetic IGs of defined structure. DISCUSSION: This article briefly describes what is known about the role of IGs in signal transduction and reviews the specific biological activities of the structurally defined IGs synthesized and tested to date. CONCLUSION: A pharmacophore for IG activity begins to emerge from the reviewed data and the structural elements necessary for activity are summarized.
Collapse
Affiliation(s)
- Meenakshi Goel
- Department of Chemistry, San José State University, One Washington Square, San José, CA 95192-90101, USA
| | - Viatcheslav N Azev
- AN Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova Str. 28, 119991, Moscow, Russia
| | - Marc d’Alarcao
- Department of Chemistry, San José State University, One Washington Square, San José, CA 95192-90101, USA
| |
Collapse
|
16
|
Chakraborty N, d'Alarcao M. An anionic inositol phosphate glycan pseudotetrasaccharide exhibits high insulin-mimetic activity in rat adipocytes. Bioorg Med Chem 2005; 13:6732-41. [PMID: 16115771 DOI: 10.1016/j.bmc.2005.07.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2005] [Revised: 07/20/2005] [Accepted: 07/20/2005] [Indexed: 10/25/2022]
Abstract
Inositol phosphate glycan pseudotetrasaccharides consisting of man-(alpha1-6)-man-(alpha1-4)-glcN-(alpha,beta1-6)-myo-inositol-1,2-cyclic phosphate possessing a sulfate group at either O-6 (compounds 3alpha,beta) or O-2 (compounds 4alpha,beta) of the terminal mannose have been prepared. Compound 4alpha was able to stimulate lipogenesis in native rat adipocytes to 78% of the maximal insulin response (MIR) with an EC50 of 1.1 microM. The other compounds exhibited lower maximal stimulations (47-63% MIR) and higher EC50 values (9.5-10.6 microM).
Collapse
Affiliation(s)
- Nilanjana Chakraborty
- Michael Chemistry Laboratory, Department of Chemistry, Tufts University, Medford, MA 02155, USA
| | | |
Collapse
|
17
|
Combs TP, Mukherjee S, de Almeida CJG, Jelicks LA, Schubert W, Lin Y, Jayabalan DS, Zhao D, Braunstein VL, Landskroner-Eiger S, Cordero A, Factor SM, Weiss LM, Lisanti MP, Tanowitz HB, Scherer PE. The adipocyte as an important target cell for Trypanosoma cruzi infection. J Biol Chem 2005; 280:24085-94. [PMID: 15843370 DOI: 10.1074/jbc.m412802200] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Adipose tissue plays an active role in normal metabolic homeostasis as well as in the development of human disease. Beyond its obvious role as a depot for triglycerides, adipose tissue controls energy expenditure through secretion of several factors. Little attention has been given to the role of adipocytes in the pathogenesis of Chagas disease and the associated metabolic alterations. Our previous studies have indicated that hyperglycemia significantly increases parasitemia and mortality in mice infected with Trypanosoma cruzi. We determined the consequences of adipocyte infection in vitro and in vivo. Cultured 3T3-L1 adipocytes can be infected with high efficiency. Electron micrographs of infected cells revealed a large number of intracellular parasites that cluster around lipid droplets. Furthermore, infected adipocytes exhibited changes in expression levels of a number of different adipocyte-specific or adipocyte-enriched proteins. The adipocyte is therefore an important target cell during acute Chagas disease. Infection of adipocytes by T. cruzi profoundly influences the pattern of adipokines. During chronic infection, adipocytes may represent an important long-term reservoir for parasites from which relapse of infection can occur. We have demonstrated that acute infection has a unique metabolic profile with a high degree of local inflammation in adipose tissue, hypoadiponectinemia, hypoglycemia, and hypoinsulinemia but with relatively normal glucose disposal during an oral glucose tolerance test.
Collapse
Affiliation(s)
- Terry P Combs
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
|
19
|
Abstract
Falciparum malaria is a complex disease with no simple explanation, affecting organs where the parasite is rare as well as those organs where it is more common. We continue to argue that it can best be understood in terms of excessive stimulation of normally useful pathways mediated by inflammatory cytokines, the prototype being tumor necrosis factor (TNF). These pathways involve downstream mediators, such as nitric oxide (NO) that the host normally uses to control parasites, but which, when uncontrolled, have bioenergetic failure of patient tissues as their predictable end point. Falciparum malaria is no different from many other infectious diseases that are clinically confused with it. The sequestration of parasitized red blood cells, prominent in some tissues but absent in others with equal functional loss, exacerbates, but does not change, these overriding principles. Recent opportunities to stain a wide range of tissues from African pediatric cases of falciparum malaria and sepsis for the inducible NO synthase (iNOS) and migration inhibitory factor (MIF) have strengthened these arguments considerably. The recent demonstration of bioenergetic failure in tissue removed from sepsis patients being able to predict a fatal outcome fulfils a prediction of these principles, and it is plausible that this will be demonstrable in severe falciparum malaria. Understanding the disease caused by falciparum malaria at a molecular level requires an appreciation of the universality of poly(ADP-ribose) polymerase-1 (PARP-1) and Na(+)/K(+)-ATPase and the protean effects of activation by inflammation of the former that include inactivation of the latter.
Collapse
Affiliation(s)
- Ian A Clark
- School of Biochemistry and Molecular Biology, Australian National University, ACT 0200, Canberra, Australia.
| | | |
Collapse
|
20
|
Müller G, Hanekop N, Kramer W, Bandlow W, Frick W. Interaction of phosphoinositolglycan(-peptides) with plasma membrane lipid rafts of rat adipocytes. Arch Biochem Biophys 2002; 408:17-32. [PMID: 12485599 DOI: 10.1016/s0003-9861(02)00451-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Insulin receptor-independent activation of the insulin signal transduction cascade in insulin-responsive target cells by phosphoinositolglycans (PIG) and PIG-peptides (PIG-P) is accompanied by redistribution of glycosylphosphatidylinositol (GPI)-anchored plasma membrane proteins (GPI proteins) and dually acylated nonreceptor tyrosine kinases from detergent/carbonate-resistant glycolipid-enriched plasma membrane raft domains of high-cholesterol content (hcDIGs) to rafts of lower cholesterol content (lcDIGs). Here we studied the nature and localization of the primary target of PIG(-P) in isolated rat adipocytes. Radiolabeled PIG-P (Tyr-Cys-Asn-NH-(CH(2))(2)-O-PO(OH)O-6Manalpha1(Manalpha1-2)-2Manalpha1-6Manalpha1-4GluN1-6Ino-1,2-(cyclic)-phosphate) prepared by chemical synthesis or a radiolabeled lipolytically cleaved GPI protein from Saccharomyces cerevisiae, which harbors the PIG-P moiety, bind to isolated hcDIGs but not to lcDIGs. Binding is saturable and abolished by pretreatment of intact adipocytes with trypsin followed by NaCl or with N-ethylmaleimide, indicating specific interaction of PIG-P with a cell surface protein. A 115-kDa polypeptide released from the cell surface by the trypsin/NaCl-treatment is labeled by [(14)C]N-ethylmaleimide. The labeling is diminished upon incubation of adipocytes with PIG-P which can be explained by direct binding of PIG-P to the 115-kDa protein and concomitant loss of its accessibility to N-ethylmaleimide. Binding of PIG-P to hcDIGs is considerably increased after pretreatment of adipocytes with (glycosyl)phosphatidylinositol-specific phospholipases compatible with lipolytic removal of endogenous ligands, such as GPI proteins/lipids. These data demonstrate that in rat adipocytes synthetic PIG(-P) as well as lipolytically cleaved GPI proteins interact specifically with hcDIGs. The interaction depends on the presence of a trypsin/NaCl/NEM-sensitive 115-kDa protein located at hcDIGs which thus represents a candidate for a binding protein for exogenous insulin-mimetic PIG(-P) and possibly endogenous GPI proteins/lipids.
Collapse
Affiliation(s)
- Günter Müller
- Aventis Pharma Germany, DG Metabolic Diseases, Industrial Park Höchst, Bldg. H825, 65926, Frankfurt am Main, Germany.
| | | | | | | | | |
Collapse
|
21
|
Clark IA. Successful model vaccine against malaria. Trends Parasitol 2002; 18:481. [PMID: 12473361 DOI: 10.1016/s1471-4922(02)02407-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
22
|
Kristiansen S, Richter EA. GLUT4-containing vesicles are released from membranes by phospholipase D cleavage of a GPI anchor. Am J Physiol Endocrinol Metab 2002; 283:E374-82. [PMID: 12110545 DOI: 10.1152/ajpendo.00441.2001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously developed a cell-free assay from rat skeletal muscle that displayed in vitro glucose transporter 4 (GLUT4) transfer from large to small membrane structures by the addition of a cytosolic protein fraction. By combining protein fractionation and the in vitro GLUT4 transfer assay, we have purified a glycosylphosphatidylinositol (GPI) phospholipase D (PLD) that induces transfer of GLUT4 from small to large membranes. The in vitro GLUT4 transfer was activated and inhibited by suramin and 1,10-phenanthroline (an activator and an inhibitor of GPI-PLD activity, respectively). Furthermore, upon purification of the GLUT4 transporter protein, the protein displayed an elution profile in which the molecular mass was related to the charge, suggesting the presence or absence of phosphate. Second, by photoaffinity labeling of the purified GLUT4 with 3-(trifluoromethyl)-3-(m-[(125)I]iodopenyl)diazirine, both labeled phosphatidylethanolamine and fatty acids (constituents of a GPI link) were recovered. Third, by using phase transition of Triton X-114, the purified GLUT4 was found to be partly detergent resistant, which is a known characteristic of GPI-linked proteins. Fourth, the purified GLUT4 protein was recognized by an antibody raised specifically against GPI links. In conclusion, GLUT4-containing vesicles may be released from a membrane compartment by action of a GPI-PLD.
Collapse
Affiliation(s)
- Søren Kristiansen
- Copenhagen Muscle Reseach Centre, Department of Human Physiology, Institute of Exercise and Sports Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | | |
Collapse
|
23
|
Lindberg J, Strålfors P, Konradsson P. Synthesis of inositol phosphoglycans containing thiol-terminated spacers for efficient coupling to maleimide functionalized solid phases or proteins. Tetrahedron 2002. [DOI: 10.1016/s0040-4020(02)00359-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
24
|
Lindberg J, Öhberg L, Garegg PJ, Konradsson P. Efficient routes to glucosamine-myo-inositol derivatives, key building blocks in the synthesis of glycosylphosphatidylinositol anchor substances. Tetrahedron 2002. [DOI: 10.1016/s0040-4020(01)01241-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
25
|
Elased KM, Gumaa KA, de Souza JB, Rahmoune H, Playfair JH, Rademacher TW. Reversal of type 2 diabetes in mice by products of malaria parasites. II. Role of inositol phosphoglycans (IPGs). Mol Genet Metab 2001; 73:248-58. [PMID: 11461192 DOI: 10.1006/mgme.2001.3186] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We have previously shown that infection with Plasmodium yoelii malaria or injection of extracts from malaria-parasitized red cells induces hypoglycemia in normal mice and normalizes the hyperglycemia in mice made moderately diabetic with streptozotocin. Inositol phosphoglycans (IPGs) are released outside cells by hydrolysis of membrane-bound glycosylphosphatidylinositols (GPIs), and act as second messengers mediating insulin action. The C57BL/Ks-db/db and C57BL/6J-ob/ob mice offer good models for studies on human obesity and Type 2 diabetes. In the present study, we show that a single iv injection of IPG-A or IPG-P extracted from P. yoelii significantly (P < 0.02) lowers the blood glucose in STZ-diabetic, db/db, and in ob/ob mice for at least 4--6 h. Using rat white adipocytes, IPG-P increased lipogenesis by 20--30% in the presence and absence of maximal concentrations of insulin (10(-8) M) (P < 0.01) and stimulated pyruvate dehydrogenase (PDH) phosphatase in a dose-related manner. Both IPG-A and IPG-P inhibited c-AMP-dependent protein kinase (PKA) in a dose-related manner. Compositional analysis of IPGs after 24 h hydrolysis revealed the presence of myo-inositol, phosphorus, galactosamine, glucosamine, and glucose in both IPG-A and IPG-P. However, hydrolysis of IPGs for 4 h highlighted differences between IPG-A and IPG-P. There are some functional similarities between P. yoelii IPGs and those previously described for mammalian liver. However, this is the first report of the hypoglycemic effect of IPGs in murine models of Type 2 diabetes. We suggest that IPGs isolated from P. yoelii, when fully characterized, may provide structural information for the synthesis of new drugs for the management of diabetes mellitus.
Collapse
Affiliation(s)
- K M Elased
- Rademacher Group Ltd, Arthur Stanley House, 6th Floor, 40-50 Tottenham Street, London W1P 9PG, United Kingdom.
| | | | | | | | | | | |
Collapse
|
26
|
Abstract
An efficient synthesis of tri-, tetra-, and pentasaccharide cyclic phosphates 1-5, structurally related to natural inositol phosphate glycans, is reported. The title compounds were assembled by PhSeOTf-promoted glycosylation of the known glucosamine precursor, t-butyldimethylsilyl 2-azido-3,6-di-O-benzyl-2-deoxy-beta-D-glucopyranoside (8) with protected 1-methylthio mono-, di-, and trimannosides 7a-c, and, after conversion into glycosyl fluorides, Cp2ZrCl2- AgOTf-promoted glycosylation of differentially protected optically pure 1D-myo-inositol 11. The syntheses were completed by installing the cyclic phosphate moieties with methylpyridinium dichlorophosphate and finally, removal of all protecting groups by dissolving-metal reduction.
Collapse
Affiliation(s)
- C H Jaworek
- Department of Chemistry, Tufts University, Medford, MA 02155, USA
| | | | | | | |
Collapse
|
27
|
Kajiyoshi M. Incorporation of ethanolamine into insulin-sensitive glycosylated phosphatidylinositol of chick embryo fibroblasts. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1488:255-67. [PMID: 11082535 DOI: 10.1016/s1388-1981(00)00129-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Insulin sensitive glycosylated phosphatidylinositol (GPI) from chick embryo fibroblasts was isolated and partially characterized. [(3)H]Ethanolamine was incorporated into lipids different from phosphatidylethanolamine, as shown by two sequential thin layer chromatographies (TLC) using an acidic solvent system followed by a basic solvent system. Other isotopes, myo-[(3)H]inositol, [(3)H]glucosamine, [(3)H]galactose, and [(3)H]palmitic acid were also incorporated into these lipids. These lipids were separated into two peaks on the second basic TLC, designated as peaks I and II from the origin. Insulin stimulation of cells caused a rapid breakdown of these two lipids. These two lipids were treated by nitrous acid and phosphatidylinositol-specific phospholipase C (PI-PLC). The radioactivity of peak I lipid was decreased by both treatments, and that of peak II lipid was also decreased by PI-PLC treatment but not significantly by nitrous acid treatment. Peak II lipid did not fulfill the criteria for GPI. Tritium released by the treatment of PI-PLC of peak I lipid was recovered in the aqueous phase. [(3)H]Ethanolamine-labeled peak I lipid was hydrolyzed by acid treatment and the hydrolysis products were analyzed by TLC and high performance liquid chromatography (HPLC). Tritium label was recovered as native label at the rate of 95%. [(3)H]Ethanolamine of peak I lipid was reductively methylated completely with formaldehyde and cyanoborohydride, as shown by HPLC analysis. The results indicate that peak I lipid contains primary ethanolamine as a glycan component and is insulin-sensitive free GPI.
Collapse
Affiliation(s)
- M Kajiyoshi
- Department of Pathological Biochemistry, Medical Research Institute, Medical and Dental University, Kandasurugadai, Chiyoda-ku, 2-3-10, Tokyo 101-0062, Japan.
| |
Collapse
|
28
|
Müller G, Grey S, Jung C, Bandlow W. Insulin-like signaling in yeast: modulation of protein phosphatase 2A, protein kinase A, cAMP-specific phosphodiesterase, and glycosyl-phosphatidylinositol-specific phospholipase C activities. Biochemistry 2000; 39:1475-88. [PMID: 10684630 DOI: 10.1021/bi9920432] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Previously, we have described significant effects of human insulin on glucose metabolism in the yeast Saccharomyces cerevisiae under conditions of growth limitation. These regulations apparently rely on a transmembrane receptor capable of binding human insulin and responding by tyrosine/serine phosphorylation of a specific set of polypeptides [Müller, G., Rouveyre, N., Crecelius, A., and Bandlow, W. (1998) Biochemistry 37, 8683-8695; Müller, G., Rouveyre, N., Upshon, C., Gross, E., and Bandlow, W. (1998) Biochemistry 37, 8696-8704; Müller, G., Rouveyre, N., Upshon, C., and Bandlow, W. (1998) Biochemistry 37, 8705-8713]. To characterize the molecular link between the initial steps in insulin-like signaling in yeast and the changes in the activities of glycogen synthase and glycogen phosphorylase, we examined here the effects of human insulin on a set of key regulatory enzymes of glycogen metabolism, protein phosphatase 2A (PP2A), cAMP-specific phosphodiesterase (cAMP-PDE), and protein kinase A (PKA). PP2A was activated about 2-fold by insulin in spheroplasts and in intact cells, whereas the fraction of active PKA was significantly reduced in a cAMP-independent manner as well as through a subsequent up to 3-fold increase in particulate cAMP-PDE activity accompanied by a 50% decrease in cytosolic cAMP levels. In addition, glycosyl-phosphatidylinositol-specific phospholipase C (GPI-PLC), which in isolated rat adipocytes is activated by insulin, was stimulated to up to 5-fold by glucose and 10-fold by glucose plus insulin in both yeast spheroplasts and intact cells leading to a concentration-dependent leftward shift of the glucose-response curve for activation of the GPI-PLC. GPI-PLC was most pronouncedly stimulated by authentic human insulin compared to various insulin analogues and insulin-like growth factor I. In addition to lipolytic cleavage by GPI-PLC, the GPI anchor of the cAMP-binding ectoprotein, Gce1p, was secondarily processed by a rapid proteolytic event. As the GPI-PLC reaction is rate limiting, the efficiency of the two-step anchor cleavage was significantly increased when insulin was present together with glucose as compared to glucose alone. The insulin concentrations effective in modulating PP2A, PKA, cAMP-PDE, and GPI-PLC activities correlate well with those required for half-saturation of the specific binding sites as well as for stimulation of protein phosphorylation and glycogen accumulation. The data suggest that mammalian insulin-sensitive cells and yeast share (part of) the key regulatory mechanism (consisting of PP2A, PKA, cAMP-PDE, and GPI-PLC) involved in the transduction of the insulin signal from the respective receptor systems to glycogen synthase and phosphorylase.
Collapse
Affiliation(s)
- G Müller
- Hoechst Marion Roussel Deutschland GmbH, DG Metabolic Diseases, Building H825, 65926 Frankfurt am Main, Germany.
| | | | | | | |
Collapse
|
29
|
Tachado SD, Mazhari-Tabrizi R, Schofield L. Specificity in signal transduction among glycosylphosphatidylinositols of Plasmodium falciparum, Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp. Parasite Immunol 1999; 21:609-17. [PMID: 10583863 DOI: 10.1046/j.1365-3024.1999.00268.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glycosylphosphatidylinositols (GPIs) and related glycoconjugates of parasite origin have been shown to regulate both the innate and acquired immune systems of the host. This is achieved through the activation of novel GPI-dependent signalling pathways in macrophages, lymphocytes and other cell types. Parasite GPIs impart at least two distinct signals to host cells through the structurally distinct inositolphosphoglycan (IPG) and fatty acid domains. Binding of IPG to as yet uncharacterized cell surface receptor(s) leads to activation of src-family protein tyrosine kinases: depending upon structure, GPI-derived fatty acids can either activate or antagonize protein kinase C, and may enter the sphingomyelinase pathway. The degree of fatty acid saturation may also contribute to signalling activity. Thus, variation in structure of parasite GPIs imparts different properties of signal transduction upon this class of glycolipid. The divergent activities of GPIs from various protozoal taxa reflect global aspects of the host/parasite relationship, suggesting that GPI signalling is a central determinant of disease in malaria, leishmaniasis and both American and African trypanosomiases.
Collapse
Affiliation(s)
- S D Tachado
- The Walter and Eliza Hall Institute of Medical Research, Post Office, Royal Melbourne Hospital, Parkville 3050 Victoria, Australia
| | | | | |
Collapse
|
30
|
Jones DR, Varela-Nieto I. Diabetes and the Role of Inositol-Containing Lipids in Insulin Signaling. Mol Med 1999. [DOI: 10.1007/bf03401978] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
|
31
|
Jaworek CH, Calias P, Iacobucci S, d'Alarcao M. Synthesis of an inositol-containing trisaccharide related to insulin signal transduction. Tetrahedron Lett 1999. [DOI: 10.1016/s0040-4039(98)02530-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
32
|
Convergence and Divergence of the Signaling Pathways for Insulin and Phosphoinositolglycans. Mol Med 1998. [DOI: 10.1007/bf03401738] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
|
33
|
Jones DR, Varela-Nieto I. The role of glycosyl-phosphatidylinositol in signal transduction. Int J Biochem Cell Biol 1998; 30:313-26. [PMID: 9611774 DOI: 10.1016/s1357-2725(97)00144-1] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Glycosyl-phosphatidylinositol (GPI) lipids have a structural role as protein anchors to the cell surface. In addition, they are implicated in hormone, growth factor and cytokine signal transduction. Their phosphodiesteric hydrolysis mediated by an activated phospholipase results in the generation of water soluble oligosaccharide species termed the inositol phosphoglycan (IPG). This product has been demonstrated to possess biological properties when added exogenously to cells mimicking the biological effects of a variety of extracellular ligands. This may be accomplished since IPG is generic for a family of closely related species which are released in a tissue-specific manner and additionally have cell-specific targets. Micro-organic synthesis has recently been able to shed new light on this topic by the introduction of defined oligosaccharide analogues of IPG for the assessment of their biological activity. These have complemented the findings observed with purified IPG from biological sources thus strengthening the belief that the GPI/IPG signalling system represents a truly novel aspect of transmembrane signalling.
Collapse
Affiliation(s)
- D R Jones
- Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
| | | |
Collapse
|
34
|
Vaena de Avalos S, Lima C, Martini C, de Lederkremer RM, Vila MC. ACTH-mediated glucocorticoid and mineralocorticoid production is inhibited by an inositolphosphoglycan and a glycosylphosphatidylinositol-phospholipase C is activated by the hormone in mammalian adrenocortical cells. Steroids 1998; 63:70-5. [PMID: 9516715 DOI: 10.1016/s0039-128x(97)00137-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In the present paper, we report that an inositolphosphoglycan (IPG), derived from a Trypanosoma cruzi glycoinositolphosphoceramide (LPPG), is able to inhibit ACTH-mediated accumulation of a glucocorticoid, cortisol, in calf adrenocortical cells. This IPG is also able to inhibit the stimulation by ACTH of the production of the main glucocorticoid, corticosterone and the main mineralocorticoid, aldosterone, in rat adrenocortical cells. Nitrous acid deamination confirmed that IPG is responsible for this inhibition. In order to study the involvement of glycosylphosphatidylinositol (GPI) in ACTH response in rat adrenal cortex, the activation of a phospholipase that hydrolyzes GPI (GPI-PLC) was evaluated. It was found that the release of alkaline phosphatase, a GPI-anchored enzyme, to the extracellular medium is increased in rat adrenocortical cells by ACTH treatment. In addition, ACTH stimulates the release of ceramide from the glycoinositolphosphoceramide purified from T. cruzi. These data suggest that ACTH activates a GPI-PLC in rat adrenal cortex, which is in agreement with our previous data in calf adrenocortical cells; thus, the hydrolysis of GPI provoked by ACTH takes place in different mammals and the IPG released could inhibit ACTH-mediated synthesis of aldosterone, corticosterone and cortisol.
Collapse
Affiliation(s)
- S Vaena de Avalos
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
| | | | | | | | | |
Collapse
|
35
|
Nosjean O, Briolay A, Roux B. Mammalian GPI proteins: sorting, membrane residence and functions. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1331:153-86. [PMID: 9325440 DOI: 10.1016/s0304-4157(97)00005-1] [Citation(s) in RCA: 156] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- O Nosjean
- Université Claude Bernard--Lyon 1, Laboratoire de Physico-chimie Biologique--UPRESA CNRS 5013, Villeurbanne, France.
| | | | | |
Collapse
|
36
|
Müller G, Wied S, Crecelius A, Kessler A, Eckel J. Phosphoinositolglycan-peptides from yeast potently induce metabolic insulin actions in isolated rat adipocytes, cardiomyocytes, and diaphragms. Endocrinology 1997; 138:3459-75. [PMID: 9231801 DOI: 10.1210/endo.138.8.5308] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Polar headgroups of free glycosyl-phosphatidylinositol (GPI) lipids or protein-bound GPI membrane anchors have been shown to exhibit insulin-mimetic activity in different cell types. However, elucidation of the molecular mode of action of these phospho-inositolglycan (PIG) molecules has been hampered by 1) lack of knowledge of their exact structure; 2) variable action profiles; and 3) rather modest effects. In the present study, these problems were circumvented by preparation of PIG-peptides (PIG-P) in sufficient quantity by sequential proteolytic (V8 protease) and lipolytic (phosphatidylinositol-specific phospholipase C) cleavage of the GPI-anchored plasma membrane protein, Gce1p, from the yeast Saccharomyces cerevisiae. The structure of the resulting PIG-P, NH2-Tyr-Cys-Asn-ethanolamine-PO4-6(Man1-2)Man1-2Man1-+ ++6Man1-4GlcNH(2)1-6myo-inositol-1,2-cyclicPO4, was revealed by amino acid analysis and Dionex exchange chromatography of fragments generated enzymatically or chemically from the neutral glycan core and is in accordance with the known consensus structures of yeast GPI anchors. PIG-P stimulated glucose transport and lipogenesis in normal, desensitized and receptor-depleted isolated rat adipocytes, increased glycerol-3-phosphate acyltransferase activity and translocation of the glucose transporter isoform 4, and inhibited isoproterenol-induced lipolysis and protein kinase A activation in adipocytes. Furthermore, PIG-P was found to stimulate glucose transport in isolated rat cardiomyocytes and glycogenesis and glycogen synthase in isolated rat diaphragms. The concentration-dependent effects of the PIG-P reached 70-90% of the maximal insulin activity with EC50-values of 0.5-5 microM. Chemical or enzymic cleavages within the glycan or peptide portion of the PIG-P led to decrease or loss of activity. The data demonstrate that PIG-P exhibits a potent insulin-mimetic activity which covers a broad spectrum of metabolic insulin actions on glucose transport and metabolism.
Collapse
Affiliation(s)
- G Müller
- Hoechst AG, Hoechst Marion Roussel, Frankfurt am Main, Germany
| | | | | | | | | |
Collapse
|
37
|
Abstract
The molecular pathways for insulin's signal transduction from its cell surface receptor to the cell's interior metabolic machinery remain in many ways uncharted. Lately two molecules have been proposed as second messengers transducing the insulin signal into the target cell. One is a phospho-oligosaccharide/inositolphosphoglycan and the other is diacylglycerol, both deriving from the same plasma membrane glycolipid, which is hydrolysed in response to insulin treatment. The phospho-oligosaccharide appears to mediate many metabolic effects of insulin through control of the phosphorylation state of key regulatory metabolic enzymes. Diacylglycerol may mediate insulin's stimulation of glucose transport over the plasma membrane. The glycolipid precursor of these putative second messengers, as well as the receptor for insulin, appear to be localized in caveolae microdomains of the plasma membrane, and glucose transporters accumulate in caveolae in response to insulin treatment, suggesting a focal role for caveolae in insulin signalling.
Collapse
Affiliation(s)
- P Strålfors
- Department of Cell Biology, Faculty of Health Sciences, University of Linköping, Sweden
| |
Collapse
|
38
|
Degerman E, Belfrage P, Manganiello VC. Structure, localization, and regulation of cGMP-inhibited phosphodiesterase (PDE3). J Biol Chem 1997; 272:6823-6. [PMID: 9102399 DOI: 10.1074/jbc.272.11.6823] [Citation(s) in RCA: 316] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Affiliation(s)
- E Degerman
- Department of Cell and Molecular Biology, Lund University, S-221 00 Lund, Sweden
| | | | | |
Collapse
|
39
|
Sanchez-Bueno A, Greenwood MR, Varela-Nieto I, Marrero I, Gil B, Mato JM, Cobbold PH. Inositol-phosphoglycan inhibits calcium oscillations in hepatocytes by reducing calcium entry. Cell Calcium 1997; 21:125-33. [PMID: 9132295 DOI: 10.1016/s0143-4160(97)90036-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Inositol-phosphoglycan (IPG) is a putative mediator of insulin action that has been shown to affect numerous biochemical processes. IPG, prepared from liver membranes, promptly inhibited phenylephrine- or vasopressin-induced [Ca2+]i oscillations when perfused over Fura-2-dextran injected rat hepatocytes. An antibody to IPG suppressed the inhibitory effect of insulin on the [Ca2+]i oscillations. Measurement of the rate of quench of cytoplasmic Fura-2 by extracellular Mn2+ showed that Ca2+ entry occurred continuously in the unstimulated cell and was not affected by phenylephrine or vasopressin. IPG, specifically, almost completely abolished the Mn2+ quench rate. Elevated extracellular [Ca2+] reversed the inhibitory effect of IPG on [Ca2+]i oscillations. We conclude that IPG inhibits the hepatocyte Ca2+ oscillatory by reducing the continuous Ca2+ influx that is required to sustain oscillations in [Ca2+]i.
Collapse
Affiliation(s)
- A Sanchez-Bueno
- Department of Human Anatomy and Cell Biology, University of Liverpool, UK.
| | | | | | | | | | | | | |
Collapse
|
40
|
Varela-Nieto I, León Y, Caro HN. Cell signalling by inositol phosphoglycans from different species. Comp Biochem Physiol B Biochem Mol Biol 1996; 115:223-41. [PMID: 8939003 DOI: 10.1016/0305-0491(96)00087-9] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The discovery of glycosyl-phosphatidylinositol (GPI) molecules and their products has given new insight into the field of signal transduction. In the last decade a novel mechanism of protein attachment to membranes has emerged, which involves a covalent linkage of the protein to the glycan moiety of a GPI. The discovery that GPI-anchored proteins are ubiquitous throughout the eukaryotes was followed by the observation that uncomplexed GPI molecules are implicated in signal transduction for a diversity of hormones and growth factors. The hydrolysis of free-GPI generates a novel second messenger: the inositol phosphoglycan (IPG). The aim of this article is to review the role of IPG and IPG-like molecules in signal transduction and to discuss future research directions.
Collapse
Affiliation(s)
- I Varela-Nieto
- Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
| | | | | |
Collapse
|
41
|
Saltiel AR. Diverse signaling pathways in the cellular actions of insulin. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 270:E375-85. [PMID: 8638681 DOI: 10.1152/ajpendo.1996.270.3.e375] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Insulin is one of the most important regulators of glucose and lipid homeostasis. Many of its cellular actions are mediated by changes in protein phosphorylation. The consequences of these phosphorylation events extend from a series of different short-term metabolic actions to longer-term effects of the hormone on cellular growth and differentiation. Although the insulin receptor itself is a tyrosine kinase that is activated upon hormone binding, the ensuing changes in phosphorylation occur predominantly on serine and threonine residues. Moreover, insulin can simultaneously stimulate the phosphorylation of some proteins and the dephosphorylation of others. These paradoxical effects of insulin suggest that separate signal transduction pathways may emanate from the receptor itself to produce the pleiotropic actions of the hormone.
Collapse
Affiliation(s)
- A R Saltiel
- Department of Signal Transduction, Parke-Davis Pharmaceutical Research, Warner-Lambert, Ann Arbor, Michigan 48105, USA
| |
Collapse
|
42
|
Manganiello VC, Degerman E, Taira M, Kono T, Belfrage P. Type III cyclic nucleotide phosphodiesterases and insulin action. CURRENT TOPICS IN CELLULAR REGULATION 1996; 34:63-100. [PMID: 8646851 DOI: 10.1016/s0070-2137(96)80003-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- V C Manganiello
- Laboratory of Cellular Metabolism, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | | | |
Collapse
|
43
|
Affiliation(s)
- A R Saltiel
- Department of Signal Transduction, Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Co., Ann Arbor, Michigan 48105, USA
| |
Collapse
|
44
|
Kovács P. Cell-surface GPI expression in Protozoa. The connection with the PI system. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 1996; 17:105-18. [PMID: 8822802 DOI: 10.1007/978-3-642-80106-8_6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- P Kovács
- Department of Biology, Semmelweis University of Medicine, Budapest, Hungary
| |
Collapse
|
45
|
Manganiello VC, Taira M, Degerman E, Belfrage P. Type III cGMP-inhibited cyclic nucleotide phosphodiesterases (PDE3 gene family). Cell Signal 1995; 7:445-55. [PMID: 8562305 DOI: 10.1016/0898-6568(95)00017-j] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Seven different but related cyclic nucleotide phosphodiesterase (PDE) gene families have been identified. Type III cGMP-inhibited (cGI) PDEs, the PDE3 gene family, are found in many tissues. cGI PDEs exhibit a high affinity for both cAMP and cGMP, and are selectively and relatively specifically inhibited by certain agents which augment myocardial contractility, promote smooth muscle relaxation and inhibit platelet aggregation. Adipocyte, platelet, and hepatocyte cGI PDE activities are regulated by cAMP-dependent phosphorylation. Insulin-induced phosphorylation/activation of adipocyte and hepatocyte cGI PDEs is thought to be important in acute regulation of triglyceride and glycogen metabolism by insulin. Two distinct cGI PDE subfamilies, products of distinct but related genes, have been identified. They exhibit the domain structure common to PDEs with a carboxyterminal region, conserved catalytic domain and divergent regulatory domain. In their catalytic domains cGI PDEs contain a 44 amino acid insertion not found in other PDE families. The expression of cGIP1 and cGIP2 mRNAs differs in different rat tissues, suggesting distinct functions for the two cGI PDE subfamilies, i.e., cGIP1 in adipose tissue, liver, testis and cGIP2 in myocardium, platelets and smooth muscle.
Collapse
Affiliation(s)
- V C Manganiello
- Pulmonary/Critical Care Medicine Branch, NHLBI, NIH, MD 20892, USA
| | | | | | | |
Collapse
|
46
|
Vila MC, Cozza EN, Lima C, Ramirez MI, De Lederkremer RM. An inositol phosphoglycan from Trypanosoma cruzi inhibits ACTH action in calf adrenocortical cells. Cell Signal 1995; 7:331-9. [PMID: 8527302 DOI: 10.1016/0898-6568(95)00008-d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We describe the effect of an inositol phosphoglycan (IPG) purified from Trypanosoma cruzi on the stimulation of aldosterone and cAMP production by ACTH in calf adrenocortical cells. T. cruzi IPG has two galactofuranose residues (Galf) which are not frequent in other IPGs. The effect of IPG with galactofuranose residues (IPG Galf) and IPG without these residues (IPG) was investigated. It was found that IPG Galf slightly decreased the stimulation of aldosterone and cAMP production by ACTH, whereas IPG significantly inhibited ACTH-mediated accumulation of both aldosterone and cAMP. The inhibition of aldosterone content in ACTH-treated cells by IPG was dose dependent. It was also found that the pretreatment of calf adrenocortical cells with IPG inhibited the accumulation of aldosterone provoked by ACTH and dibutyryladenosine-3',5'-cyclic monophosphate (db-cAMP). On the other hand, the activation of a GPI (glycosyl phosphatidylinositol)-phospholipase C by ACTH was evaluated. First it was found that the release of ceramide from a GPI-like molecule: a glycoinositol-phosphoceramide (LPPG) purified from T. cruzi is increased in ACTH-treated cells. Second, the release of alkaline phosphatase, a GPI-anchored enzyme, to the extracellular medium was increased in these cells by ACTH. These data suggest that ACTH activates a phospholipase C in calf adrenocortical cells, releasing IPG, which in turn may inhibit, or modulate ACTH action.
Collapse
Affiliation(s)
- M C Vila
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
| | | | | | | | | |
Collapse
|
47
|
Müller G, Wied S, Wetekam EM, Crecelius A, Unkelbach A, Pünter J. Stimulation of glucose utilization in 3T3 adipocytes and rat diaphragm in vitro by the sulphonylureas, glimepiride and glibenclamide, is correlated with modulations of the cAMP regulatory cascade. Biochem Pharmacol 1994; 48:985-96. [PMID: 8093111 DOI: 10.1016/0006-2952(94)90369-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The long-term hypoglycemic activity of sulphonylurea drugs has been attributed, in part at least, to the stimulation of glucose utilization in extra-pancreatic tissues. The novel sulphonylurea, glimepiride, gives rise to a longer lasting reduction in the blood sugar level in dogs and rabbits compared to glibenclamide (Geisen K, Drug Res 38: 1120-1130, 1988). This cannot be explained adequately by elevated plasma insulin levels. This study investigated whether this prolonged hypoglycemic phase was based on the drug's abilities to stimulate glucose utilization and affect the underlying regulatory mechanisms in insulin-sensitive cells in vitro. It was found that in the absence of added insulin, glimepiride and glibenclamide (1-50 microM) stimulated lipogenesis (3T3 adipocytes) and glycogenesis (isolated rat diaphragm) approximately 4.5- and 2.5-fold, respectively, and reduced the isoproterenol-stimulated lipolysis (rat adipocytes) up to 40-60%. The increased glucose utilization was correlated with a 3-4-fold higher 2-deoxyglucose transport rate and amount of GLUT4 at the plasma membrane, as well as with increased activities of key metabolic enzymes (glycerol-3-phosphate acyltransferase, glycogen synthase) within the same concentration range. Furthermore, the low Km cAMP-specific phosphodiesterase was activated 1.8-fold, whereas the cytosolic cAMP level and protein kinase A activity ratios were significantly lowered after incubation of isoproterenol-stimulated rat adipocytes with the sulphonylureas. In many of the aspects studied the novel sulphonylurea, glimepride, exhibited slightly lower ED50-values than glibenclamide. This study demonstrates correlations existing between drug-induced stimulation of glucose transport/metabolism and cAMP degradation/protein kinase A inhibition as well as between the relative efficiencies of glimepiride and glibenclamide in inducing these extra-pancreatic processes. Therefore, it is suggested that the stimulation of glucose utilization by sulphonylureas is mediated by a decrease of cAMP-dependent phosphorylation of GLUT4 and glucose metabolizing enzymes. The therapeutic relevance of extra-pancreatic effects of sulphonylureas, in general, and of the differences between glimepiride and glibenclamide as observed in vitro in this work, in particular, remain to be elucidated.
Collapse
Affiliation(s)
- G Müller
- Hoechst Aktiengesellschaft Frankfurt a.M., SBU Metabolic Diseases H825, Frankfurt am Main, Germany
| | | | | | | | | | | |
Collapse
|
48
|
Chiara JL, Martín-Lomas M. A stereoselective route to enantiomerically pure myo-inositol derivatives starting from D-mannitol. Tetrahedron Lett 1994. [DOI: 10.1016/s0040-4039(00)76674-3] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
49
|
Lingwood CA, Sakac D, Saltiel A. Developmentally regulated testicular galactolipid sulfotransferase inhibitor is a phosphoinositol glycerolipid and insulin-mimetic. Mol Reprod Dev 1994; 37:462-6. [PMID: 8011331 DOI: 10.1002/mrd.1080370414] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The synthesis of sulfogalactosylglycerolipid (SGG) is a differentiation marker in spermatogenesis restricted to the zygotene and early pachytene spermatocytes. The galactolipid sulfotransferase responsible for the synthesis of SGG is regulated by a phosphorylation mechanism. The activity of this enzyme is reduced in cells later in spermatogenesis by a low molecular weight inhibitor, which can be extracted in organic solvents and purified by reverse phase high pressure liquid chromatography (HPLC). This purified inhibitor is a potent postreceptor insulin-mimetic, which stimulates adipocyte lipogenesis more effectively than does insulin. Phosphoinositol (PI) glycolipids have been proposed as second messengers of the insulin phosphorylation cascade. These species contain a nonacetylated glucosamine, which renders them liable to cleavage by deamidation. The activity of the sulfotransferase inhibitor was lost following nitrous acid deamidation and was labile to PI specific phospholipase C digestion. Insulin and insulin-like growth factor I were found to inhibit germ cell synthesis of SGG in vitro to some degree but had no direct effect on the testicular galactolipid sulfotransferase assay. These results indicate that the sulfotransferase inhibitor is a glycosyl phosphoinositide similar to the lipid species, which mediate insulin signal transduction and suggest that germ cell SGG biosynthesis may be regulated by a receptor-mediated phosphorylation pathway.
Collapse
Affiliation(s)
- C A Lingwood
- Department of Microbiology, Hospital for Sick Children, Toronto, Ontario, Canada
| | | | | |
Collapse
|
50
|
Schofield L, Vivas L, Hackett F, Gerold P, Schwarz RT, Tachado S. Neutralizing monoclonal antibodies to glycosylphosphatidylinositol, the dominant TNF-alpha-inducing toxin of Plasmodium falciparum: prospects for the immunotherapy of severe malaria. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 1993; 87:617-26. [PMID: 8122925 DOI: 10.1080/00034983.1993.11812820] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Tumour necrosis factor-alpha (TNF-alpha) is an endogenous mediator of shock and inflammation. Many of the life-threatening and severe pathologies associated with complicated and cerebral malaria are thought to result from the overproduction of this cytokine in response to agents of parasite origin. The identification and characterization of these agents may therefore provide the molecular basis for a detailed understanding of the disease process. Recently it has been shown that glycosylphosphatidylinositols are a novel class of glycolipid toxin produced by the parasite, which substitute for the endogenous inositolglycan-based signal transduction pathways of the host. Glycosylphosphatidylinositol stimulates high levels of TNF-alpha and interleukin-1 production by macrophages and induces hypoglycaemia through an insulin-mimetic activity, and may therefore contribute to the cerebral syndrome and other malarial pathophysiology. That monoclonal antibodies to parasite-derived glycosylphosphatidylinositol can neutralize the toxic activities of whole parasite extracts is also demonstrated here. These findings suggest a central role for glycosylphosphatidylinositol of parasite origin in the aetiology of severe malaria and suggest novel approaches for the immunotherapy or immunoprophylaxis of disease.
Collapse
Affiliation(s)
- L Schofield
- National Institute for Medical Research, Mill Hill, London, U.K
| | | | | | | | | | | |
Collapse
|