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Ten Broeke T, Honing H, Brandsma AM, Jacobino S, Bakema JE, Kanters D, van der Linden JAM, Bracke M, Koenderman L, Leusen JHW. FcαRI Dynamics Are Regulated by GSK-3 and PKCζ During Cytokine Mediated Inside-Out Signaling. Front Immunol 2019; 9:3191. [PMID: 30766540 PMCID: PMC6365424 DOI: 10.3389/fimmu.2018.03191] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 12/31/2018] [Indexed: 12/03/2022] Open
Abstract
IgA binding to FcαRI (CD89) is rapidly enhanced by cytokine induced inside-out signaling. Dephosphorylation of serine 263 in the intracellular tail of FcαRI by PP2A and PI3K activation are instrumental in this process. To further investigate these signaling pathways, we targeted downstream kinases of PI3K. Our experiments revealed that PI3K activates PKCζ, which subsequently inhibits GSK-3, a constitutively active kinase in resting cells and found here to be associated with FcαRI. We propose that GSK-3 maintains FcαRI in an inactive state at homeostatic conditions. Upon cytokine stimulation, GSK-3 is inactivated through a PI3K-PKCζ pathway, preventing the maintenance of phosphorylated inactive FcαRI. The concomitantly activated PP2A is then able to dephosphorylate and activate FcαRI. Moreover, FRAP and FLIP studies showed that FcαRI activation coincides with an increased mobile fraction of the receptor. This can enhance FcαRI valency and contribute to stronger avidity for IgA immune complexes. This tightly regulated inside-out signaling pathway allows leukocytes to respond rapidly and efficiently to their environment and could be exploited to enhance the efficacy of future IgA therapeutics.
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Affiliation(s)
- Toine Ten Broeke
- Laboratory of Translational Immunology, University Medical Center, Utrecht, Netherlands
| | - Henk Honing
- Department of Respiratory Medicine, University Medical Center, Utrecht, Netherlands
| | - Arianne M Brandsma
- Laboratory of Translational Immunology, University Medical Center, Utrecht, Netherlands
| | - Shamir Jacobino
- Laboratory of Translational Immunology, University Medical Center, Utrecht, Netherlands
| | - Jantine E Bakema
- Laboratory of Translational Immunology, University Medical Center, Utrecht, Netherlands.,Tumor Biology Section, Department of Otolaryngology, Head-Neck Surgery, VU University Medical Center, Amsterdam, Netherlands
| | - Deon Kanters
- Laboratory of Translational Immunology, University Medical Center, Utrecht, Netherlands.,Department of Respiratory Medicine, University Medical Center, Utrecht, Netherlands
| | - Jan A M van der Linden
- Laboratory of Translational Immunology, University Medical Center, Utrecht, Netherlands.,Department of Respiratory Medicine, University Medical Center, Utrecht, Netherlands
| | - Madelon Bracke
- Department of Pharmacoepidemiology and Pharmacotherapy, University Medical Center, Utrecht, Netherlands
| | - Leo Koenderman
- Laboratory of Translational Immunology, University Medical Center, Utrecht, Netherlands.,Department of Respiratory Medicine, University Medical Center, Utrecht, Netherlands
| | - Jeanette H W Leusen
- Laboratory of Translational Immunology, University Medical Center, Utrecht, Netherlands
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Cimmino I, Lorenzo V, Fiory F, Doti N, Ricci S, Cabaro S, Liotti A, Vitagliano L, Longo M, Miele C, Formisano P, Beguinot F, Ruvo M, Oriente F. A peptide antagonist of Prep1-p160 interaction improves ceramide-induced insulin resistance in skeletal muscle cells. Oncotarget 2017; 8:71845-71858. [PMID: 29069751 PMCID: PMC5641094 DOI: 10.18632/oncotarget.18286] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 05/03/2017] [Indexed: 12/11/2022] Open
Abstract
Prep1 is a homeodomain transcription factor belonging to the TALE protein family. Its overexpression affects glucose metabolism in several tissues. In particular, in skeletal muscle tissue the interaction of Prep1 with its cofactor p160 impairs GLUT4 expression and glucose uptake. In this study, we show that ceramides (C2cer), a class of lipids antagonizing insulin signalling, increase the levels of Prep1 and p160 in a dose and time-dependent fashion in L6 cells and induce their association by 80%. We find that C2cer exposure inhibits insulin receptor, IRS1 and Akt phosphorylation and reduces insulin-stimulated glycogen content and glucose uptake by 1.3- and 2.1-fold, respectively. The synthetic Prep1(54-72) peptide, mimicking the Prep1 region involved in the interaction with p160, reduces in vitro Prep1-p160 binding in a dose-dependent way (IC50 = 0.20μM). In C2cer-treated L6 cells, 10μM Prep1(54-72) restores insulin signalling impaired by ceramide treatment. Prep1 overexpressing L6 cells display similar metabolic alterations observed in ceramide-treated L6 cells and the presence of Prep1(54-72) mitigates these events. All these findings suggest that disruption of the Prep1/p160 molecular interaction enhances insulin sensitivity impaired by ceramides in skeletal muscle cells and indicate this complex as an important target for type 2 diabetes.
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Affiliation(s)
- Ilaria Cimmino
- Department of Translational Medicine, Federico II University of Naples and URT "Genomic of Diabetes" of Institute of Experimental Endocrinology and Oncology, National Council of Research (CNR), Naples, Italy
| | - Virginia Lorenzo
- Institute of Biostructure and Bioimaging, National Research Council and Interuniversity Research Centre on Bioactive Peptides, Naples, Italy
| | - Francesca Fiory
- Department of Translational Medicine, Federico II University of Naples and URT "Genomic of Diabetes" of Institute of Experimental Endocrinology and Oncology, National Council of Research (CNR), Naples, Italy
| | - Nunzianna Doti
- Institute of Biostructure and Bioimaging, National Research Council and Interuniversity Research Centre on Bioactive Peptides, Naples, Italy
| | - Serena Ricci
- Department of Translational Medicine, Federico II University of Naples and URT "Genomic of Diabetes" of Institute of Experimental Endocrinology and Oncology, National Council of Research (CNR), Naples, Italy
| | - Serena Cabaro
- Department of Translational Medicine, Federico II University of Naples and URT "Genomic of Diabetes" of Institute of Experimental Endocrinology and Oncology, National Council of Research (CNR), Naples, Italy
| | - Antonietta Liotti
- Department of Translational Medicine, Federico II University of Naples and URT "Genomic of Diabetes" of Institute of Experimental Endocrinology and Oncology, National Council of Research (CNR), Naples, Italy
| | - Luigi Vitagliano
- Institute of Biostructure and Bioimaging, National Research Council and Interuniversity Research Centre on Bioactive Peptides, Naples, Italy
| | - Michele Longo
- Department of Translational Medicine, Federico II University of Naples and URT "Genomic of Diabetes" of Institute of Experimental Endocrinology and Oncology, National Council of Research (CNR), Naples, Italy
| | - Claudia Miele
- Department of Translational Medicine, Federico II University of Naples and URT "Genomic of Diabetes" of Institute of Experimental Endocrinology and Oncology, National Council of Research (CNR), Naples, Italy
| | - Pietro Formisano
- Department of Translational Medicine, Federico II University of Naples and URT "Genomic of Diabetes" of Institute of Experimental Endocrinology and Oncology, National Council of Research (CNR), Naples, Italy
| | - Francesco Beguinot
- Department of Translational Medicine, Federico II University of Naples and URT "Genomic of Diabetes" of Institute of Experimental Endocrinology and Oncology, National Council of Research (CNR), Naples, Italy
| | - Menotti Ruvo
- Institute of Biostructure and Bioimaging, National Research Council and Interuniversity Research Centre on Bioactive Peptides, Naples, Italy
| | - Francesco Oriente
- Department of Translational Medicine, Federico II University of Naples and URT "Genomic of Diabetes" of Institute of Experimental Endocrinology and Oncology, National Council of Research (CNR), Naples, Italy
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3
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Neukamm SS, Ott J, Dammeier S, Lehmann R, Häring HU, Schleicher E, Weigert C. Phosphorylation of serine 1137/1138 of mouse insulin receptor substrate (IRS) 2 regulates cAMP-dependent binding to 14-3-3 proteins and IRS2 protein degradation. J Biol Chem 2013; 288:16403-16415. [PMID: 23615913 DOI: 10.1074/jbc.m113.474593] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Insulin receptor substrate (IRS) 2 as intermediate docking platform transduces the insulin/IGF-1 (insulin like growth factor 1) signal to intracellular effector molecules that regulate glucose homeostasis, β-cell growth, and survival. Previously, IRS2 has been identified as a 14-3-3 interaction protein. 14-3-3 proteins can bind their target proteins via phosphorylated serine/threonine residues located within distinct motifs. In this study the binding of 14-3-3 to IRS2 upon stimulation with forskolin or the cAMP analog 8-(4-chlorophenylthio)-cAMP was demonstrated in HEK293 cells. Binding was reduced with PKA inhibitors H89 or Rp-8-Br-cAMPS. Phosphorylation of IRS2 on PKA consensus motifs was induced by forskolin and the PKA activator N(6)-Phe-cAMP and prevented by both PKA inhibitors. The amino acid region after position 952 on IRS2 was identified as the 14-3-3 binding region by GST-14-3-3 pulldown assays. Mass spectrometric analysis revealed serine 1137 and serine 1138 as cAMP-dependent, potential PKA phosphorylation sites. Mutation of serine 1137/1138 to alanine strongly reduced the cAMP-dependent 14-3-3 binding. Application of cycloheximide revealed that forskolin enhanced IRS2 protein stability in HEK293 cells stably expressing IRS2 as well as in primary hepatocytes. Stimulation with forskolin did not increase protein stability either in the presence of a 14-3-3 antagonist or in the double 1137/1138 alanine mutant. Thus the reduced IRS2 protein degradation was dependent on the interaction with 14-3-3 proteins and the presence of serine 1137/1138. We present serine 1137/1138 as novel cAMP-dependent phosphorylation sites on IRS2 and show their importance in 14-3-3 binding and IRS2 protein stability.
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Affiliation(s)
- Sabine S Neukamm
- Division of Clinical Chemistry and Pathobiochemistry, Tuebingen 72076, Germany; Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tuebingen (Paul Langerhans Institute Tuebingen), Tuebingen, Germany; German Center for Diabetes Research (DZD), Tuebingen 72076, Germany
| | - Jennifer Ott
- Medical Proteome Center, Institute for Ophtalmic Research, University Hospital Tuebingen, Tuebingen 72076, Germany
| | - Sascha Dammeier
- Medical Proteome Center, Institute for Ophtalmic Research, University Hospital Tuebingen, Tuebingen 72076, Germany
| | - Rainer Lehmann
- Division of Clinical Chemistry and Pathobiochemistry, Tuebingen 72076, Germany; Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tuebingen (Paul Langerhans Institute Tuebingen), Tuebingen, Germany; German Center for Diabetes Research (DZD), Tuebingen 72076, Germany
| | - Hans-Ulrich Häring
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tuebingen (Paul Langerhans Institute Tuebingen), Tuebingen, Germany; German Center for Diabetes Research (DZD), Tuebingen 72076, Germany; Division of Endocrinology, Diabetology, Vascular Medicine, Nephrology and Clinical Chemistry, Department of Internal Medicine IV, Tuebingen 72076, Germany
| | - Erwin Schleicher
- Division of Clinical Chemistry and Pathobiochemistry, Tuebingen 72076, Germany; Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tuebingen (Paul Langerhans Institute Tuebingen), Tuebingen, Germany; German Center for Diabetes Research (DZD), Tuebingen 72076, Germany
| | - Cora Weigert
- Division of Clinical Chemistry and Pathobiochemistry, Tuebingen 72076, Germany; Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tuebingen (Paul Langerhans Institute Tuebingen), Tuebingen, Germany; German Center for Diabetes Research (DZD), Tuebingen 72076, Germany.
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4
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Parrales A, López E, López-Colomé A. Thrombin activation of PI3K/PDK1/Akt signaling promotes cyclin D1 upregulation and RPE cell proliferation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:1758-66. [DOI: 10.1016/j.bbamcr.2011.06.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 05/31/2011] [Accepted: 06/16/2011] [Indexed: 10/18/2022]
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5
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Velazquez-Garcia S, Valle S, Rosa TC, Takane KK, Demirci C, Alvarez-Perez JC, Mellado-Gil JM, Ernst S, Scott DK, Vasavada RC, Alonso LC, Garcia-Ocaña A. Activation of protein kinase C-ζ in pancreatic β-cells in vivo improves glucose tolerance and induces β-cell expansion via mTOR activation. Diabetes 2011; 60:2546-59. [PMID: 21911744 PMCID: PMC3178296 DOI: 10.2337/db10-1783] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
OBJECTIVE PKC-ζ activation is a key signaling event for growth factor-induced β-cell replication in vitro. However, the effect of direct PKC-ζ activation in the β-cell in vivo is unknown. In this study, we examined the effects of PKC-ζ activation in β-cell expansion and function in vivo in mice and the mechanisms associated with these effects. RESEARCH DESIGN AND METHODS We characterized glucose homeostasis and β-cell phenotype of transgenic (TG) mice with constitutive activation of PKC-ζ in the β-cell. We also analyzed the expression and regulation of signaling pathways, G1/S cell cycle molecules, and β-cell functional markers in TG and wild-type mouse islets. RESULTS TG mice displayed increased plasma insulin, improved glucose tolerance, and enhanced insulin secretion with concomitant upregulation of islet insulin and glucokinase expression. In addition, TG mice displayed increased β-cell proliferation, size, and mass compared with wild-type littermates. The increase in β-cell proliferation was associated with upregulation of cyclins D1, D2, D3, and A and downregulation of p21. Phosphorylation of D-cyclins, known to initiate their rapid degradation, was reduced in TG mouse islets. Phosphorylation/inactivation of GSK-3β and phosphorylation/activation of mTOR, critical regulators of D-cyclin expression and β-cell proliferation, were enhanced in TG mouse islets, without changes in Akt phosphorylation status. Rapamycin treatment in vivo eliminated the increases in β-cell proliferation, size, and mass; the upregulation of cyclins Ds and A in TG mice; and the improvement in glucose tolerance-identifying mTOR as a novel downstream mediator of PKC-ζ-induced β-cell replication and expansion in vivo. CONCLUSIONS PKC:-ζ, through mTOR activation, modifies the expression pattern of β-cell cycle molecules leading to increased β-cell replication and mass with a concomitant enhancement in β-cell function. Approaches to enhance PKC-ζ activity may be of value as a therapeutic strategy for the treatment of diabetes.
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Affiliation(s)
- Silvia Velazquez-Garcia
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shelley Valle
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Taylor C. Rosa
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Karen K. Takane
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Cem Demirci
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Juan C. Alvarez-Perez
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Jose M. Mellado-Gil
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Sara Ernst
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Donald K. Scott
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Rupangi C. Vasavada
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Laura C. Alonso
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Adolfo Garcia-Ocaña
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
- Corresponding author: Adolfo Garcia-Ocaña,
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6
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Jiang X, Tian Q, Wang Y, Zhou XW, Xie JZ, Wang JZ, Zhu LQ. Acetyl-L-Carnitine ameliorates spatial memory deficits induced by inhibition of phosphoinositol-3 kinase and protein kinase C. J Neurochem 2011; 118:864-78. [DOI: 10.1111/j.1471-4159.2011.07355.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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7
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Krook A, Zierath JR. Specificity of insulin signalling in human skeletal muscle as revealed by small interfering RNA. Diabetologia 2009; 52:1231-9. [PMID: 19333572 DOI: 10.1007/s00125-009-1330-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Accepted: 02/23/2009] [Indexed: 12/13/2022]
Abstract
Insulin action on metabolically active tissues is a complex process involving positive and negative feedback regulation to control whole body glucose homeostasis. At the cellular level, glucose and lipid metabolism, as well as protein synthesis, are controlled through canonical insulin signalling cascades. The discovery of small interfering RNA (siRNA) allows for the molecular dissection of critical components of the regulation of metabolic and gene regulatory events in insulin-sensitive tissues. The application of siRNA to tissues of human origin allows for the molecular dissection of the mechanism(s) regulating glucose and lipid metabolism. Penetration of the pathways controlling insulin action in human tissue may aid in discovery efforts to develop diabetes prevention and treatment strategies. This review will focus on the use of siRNA to validate critical regulators controlling insulin action in human skeletal muscle, a key organ important for the control of whole body insulin-mediated glucose uptake and metabolism.
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Affiliation(s)
- A Krook
- Department of Molecular Medicine and Surgery, Section of Integrative Physiology, Karolinska Institutet, von Eulers väg 4, Stockholm, Sweden
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8
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Gutiérrez S, De Paul AL, Petiti JP, del Valle Sosa L, Palmeri CM, Soaje M, Orgnero EM, Torres AI. Estradiol interacts with insulin through membrane receptors to induce an antimitogenic effect on lactotroph cells. Steroids 2008; 73:515-27. [DOI: 10.1016/j.steroids.2008.01.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Revised: 11/16/2007] [Accepted: 01/03/2008] [Indexed: 01/22/2023]
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9
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Wu J, Tseng YD, Xu CF, Neubert TA, White MF, Hubbard SR. Structural and biochemical characterization of the KRLB region in insulin receptor substrate-2. Nat Struct Mol Biol 2008; 15:251-8. [DOI: 10.1038/nsmb.1388] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2007] [Accepted: 01/10/2008] [Indexed: 11/09/2022]
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10
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Brunelli S, Relaix F, Baesso S, Buckingham M, Cossu G. Beta catenin-independent activation of MyoD in presomitic mesoderm requires PKC and depends on Pax3 transcriptional activity. Dev Biol 2007; 304:604-14. [PMID: 17275805 DOI: 10.1016/j.ydbio.2007.01.006] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 11/09/2006] [Accepted: 01/04/2007] [Indexed: 01/15/2023]
Abstract
Early activation of myogenesis in the somite depends on signals from surrounding tissues. Canonical beta-catenin dependent Wnt signalling preferentially activates Myf5. We now show, in explant experiments with presomitic mesoderm, that the expression of another myogenic determination factor, MyoD, depends on non-canonical Wnt signalling, probably emanating from the dorsal ectoderm. Inhibitors of PKC block MyoD expression, indicating that the intracellular Wnt pathway depends on this kinase. In the absence of Myf5 and Mrf4, this activation is only minorily affected and we identify Pax3 as the transcriptional mediator responsible for MyoD expression. When embryos expressing a constitutively active form of Pax3, PAX3-FKHR, are used for these studies in the presence of PKC inhibitors, MyoD expression is not affected, suggesting that Wnt signalling acts on the transcriptional activity of Pax3.
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Affiliation(s)
- Silvia Brunelli
- Stem Cell Research Institute, H. San Raffaele Scientific Institute, Via Olgettina 58, 20132, Milan, Italy
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11
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D'Alessandris C, Lauro R, Presta I, Sesti G. C-reactive protein induces phosphorylation of insulin receptor substrate-1 on Ser307 and Ser 612 in L6 myocytes, thereby impairing the insulin signalling pathway that promotes glucose transport. Diabetologia 2007; 50:840-9. [PMID: 17279354 DOI: 10.1007/s00125-006-0522-y] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Accepted: 10/06/2006] [Indexed: 10/23/2022]
Abstract
AIMS/HYPOTHESIS C-reactive protein (CRP) is associated with insulin resistance and predicts development of type 2 diabetes. However, it is unknown whether CRP directly affects insulin signalling action. To this aim, we determined the effects of human recombinant CRP (hrCRP) on insulin signalling involved in glucose transport in L6 myotubes. MATERIALS AND METHODS L6 myotubes were exposed to endotoxin-free hrCRP and insulin-stimulated activation of signal molecules, glucose uptake and glycogen synthesis were assessed. RESULTS We found that hrCRP stimulates both c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK)1/2 activity. These effects were paralleled by a concomitant increase in IRS-1 phosphorylation at Ser(307) and Ser(612), respectively. The stimulatory effects of hrCRP on IRS-1 phosphorylation at Ser(307) and Ser(612) were partially reversed by treatment with specific JNK and ERK1/2 inhibitors, respectively. Exposure of L6 myotubes to hrCRP reduced insulin-stimulated phosphorylation of IRS-1 at Tyr(632), a site essential for engaging p85 subunit of phosphatidylinositol-3 kinase (PI-3K), protein kinase B (Akt) activation and glycogen synthase kinase-3 (GSK-3) phosphorylation. These events were accompanied by a decrease in insulin-stimulated glucose transporter (GLUT) 4 translocation to the plasma membrane, glucose uptake and glucose incorporation into glycogen. The inhibitory effects of hrCRP on insulin signalling and insulin-stimulated GLUT4 translocation were reversed by treatment with JNK inhibitor I and the mitogen-activated protein kinase inhibitor, PD98059. CONCLUSIONS/INTERPRETATION Our data suggest that hrCRP may cause insulin resistance by increasing IRS-1 phosphorylation at Ser(307) and Ser(612) via JNK and ERK1/2, respectively, leading to impaired insulin-stimulated glucose uptake, GLUT4 translocation, and glycogen synthesis mediated by the IRS-1/PI-3K/Akt/GSK-3 pathway.
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Affiliation(s)
- C D'Alessandris
- Department of Internal Medicine, University of Rome-Tor Vergata, Rome, Italy
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Furlong F, Crean J, Thornton L, O'Leary R, Murphy M, Martin F. Dysregulated intracellular signaling impairs CTGF-stimulated responses in human mesangial cells exposed to high extracellular glucose. Am J Physiol Renal Physiol 2007; 292:F1691-700. [PMID: 17327498 DOI: 10.1152/ajprenal.00342.2006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
High ambient glucose activates intracellular signaling pathways to induce the expression of extracellular matrix and cytokines such as connective tissue growth factor (CTGF). Cell responses to CTGF in already glucose-stressed cells may act to transform the mesangial cell phenotype leading to the development of glomerulosclerosis. We analyzed cell signaling downstream of CTGF in high glucose-stressed mesangial cells to model signaling in the diabetic milieu. The addition of CTGF to primary human mesangial cells activates cell migration which is associated with a PKC-zeta-GSK3beta signaling axis. In high ambient glucose basal PKC-zeta and GSK3beta phosphorylation levels are selectively increased and CTGF-stimulated PKC-zeta and GSK3beta phosphorylation was impaired. These effects were not induced by osmotic changes. CTGF-driven profibrotic cell signaling as determined by p42/44 MAPK and Akt phosphorylation was unaffected by high glucose. Nonresponsiveness of the PKC-zeta-GSK3beta signaling axis suppressed effective remodeling of the microtubule network necessary to support cell migration. However, interestingly the cells remain plastic: modulation of glucose-induced PKC-beta activity in human mesangial cells reversed some of the pathological effects of glucose damage in these cells. We show that inhibition of PKC-beta with LY379196 and PKC-beta siRNA reduced basal PKC-zeta and GSK3beta phosphorylation in human mesangial cells exposed to high glucose. CTGF stimulation under these conditions again resulted in PKC-zeta phosphorylation and human mesangial cell migration. Regulation of PKC-zeta by PKC-beta in this instance may establish PKC-zeta as a target for constraining the progression of mesangial cell dysfunction in the pathogenesis of diabetic nephropathy.
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Affiliation(s)
- Fiona Furlong
- UCD School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Belfield, Dublin, Ireland
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13
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Umar S, Wang Y, Morris AP, Sellin JH. Dual alterations in casein kinase I-epsilon and GSK-3beta modulate beta-catenin stability in hyperproliferating colonic epithelia. Am J Physiol Gastrointest Liver Physiol 2007; 292:G599-607. [PMID: 17053159 DOI: 10.1152/ajpgi.00343.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Casein kinase I (CKI)-epsilon and GSK-3beta phosphorylate beta-catenin at Ser(45) (beta-cat(45)) and Thr(41)/Ser(37,33) (beta-cat(33,37,41)) residues, thereby facilitating its ubiquitination and proteasomal degradation. We used a Citrobacter rodentium-induced transmissible murine colonic hyperplasia (TMCH) model to determine Ser/Thr phosphorylation and biological function of beta-catenin during crypt hyperproliferation. TMCH was associated with 3-fold and 3.3-fold increases in CKI-epsilon cellular abundance and 2-fold and 1.8-fold increase in its activity at 6 and 12 days after infection, respectively. beta-Catenin coimmunoprecipitated with both cellular and nuclear CKI-epsilon and cellular axin at these time points. Cellular beta-catenin was constitutively phosphorylated at Ser(45) and underwent subcellular redistribution to cytoskeletal and nuclear fractions at days 6 and 12 of TMCH, respectively. beta-cat(33,37,41), however, exhibited only subtle changes in either phosphorylation status or subcellular distribution even after blocking proteasomal degradation in vivo. Interestingly, GSK-3beta underwent increased phosphorylation at Ser(9), leading to 40% and 70% decreases in its activity at these time points, respectively. Coimmunoprecipitation studies exhibited strong association of GSK-3beta with PKC-zeta at either time point. Cellular beta-cat(45) stabilized and, along with unphosphorylated beta-catenin, underwent nuclear translocation, associated with nuclear accumulated Tcf-4 and cAMP response element binding protein binding protein, and was significantly acetylated, leading to increases in DNA binding. Priming of beta-catenin at Ser(45) exists in vivo. However, beta-cat(45) does not necessarily enter the degradation pathway. Impairment in linking beta-cat(45) to subsequent GSK-3beta-mediated phosphorylation and degradation may account for increased steady-state levels of both unphosphorylated as well as Ser(45)-phosphorylated beta-catenin, which may be causally linked to increases in cell census during TMCH.
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Affiliation(s)
- Shahid Umar
- Div of Gastroenterology, Univ of Texas Medical Branch, Galveston, TX 77555-0632, USA.
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14
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Perfetti A, Oriente F, Iovino S, Alberobello AT, Barbagallo APM, Esposito I, Fiory F, Teperino R, Ungaro P, Miele C, Formisano P, Beguinot F. Phorbol esters induce intracellular accumulation of the anti-apoptotic protein PED/PEA-15 by preventing ubiquitinylation and proteasomal degradation. J Biol Chem 2007; 282:8648-57. [PMID: 17227770 DOI: 10.1074/jbc.m608359200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes (PED/PEA)-15 is an anti-apoptotic protein whose expression is increased in several cancer cells and following experimental skin carcinogenesis. Exposure of untransfected C5N keratinocytes and transfected HEK293 cells to phorbol esters (12-O-tetradecanoylphorbol-13-acetate (TPA)) increased PED/PEA-15 cellular content and enhanced its phosphorylation at serine 116 in a time-dependent fashion. Ser-116 --> Gly (PED(S116G)) but not Ser-104 --> Gly (PED(S104G)) substitution almost completely abolished TPA regulation of PED/PEA-15 expression. TPA effect was also prevented by antisense inhibition of protein kinase C (PKC)-zeta and by the expression of a dominant-negative PKC-zeta mutant cDNA in HEK293 cells. Similar to long term TPA treatment, overexpression of wild-type PKC-zeta increased cellular content and phosphorylation of WT-PED/PEA-15 and PED(S104G) but not of PED(S116G). These events were accompanied by the activation of Ca2+-calmodulin kinase (CaMK) II and prevented by the CaMK blocker, KN-93. At variance, the proteasome inhibitor lactacystin mimicked TPA action on PED/PEA-15 intracellular accumulation and reverted the effects of PKC-zeta and CaMK inhibition. Moreover, we show that PED/PEA-15 bound ubiquitin in intact cells. PED/PEA-15 ubiquitinylation was reduced by TPA and PKC-zeta overexpression and increased by KN-93 and PKC-zeta block. Furthermore, in HEK293 cells expressing PED(S116G), TPA failed to prevent ubiquitin-dependent degradation of the protein. Accordingly, in the same cells, TPA-mediated protection from apoptosis was blunted. Taken together, our results indicate that TPA increases PED/PEA-15 expression at the post-translational level by inducing phosphorylation at serine 116 and preventing ubiquitinylation and proteosomal degradation.
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Affiliation(s)
- Anna Perfetti
- Dipartimento di Biologia e Patologia cellulare e Molecolare (DBPCM), Federico II University of Naples, Via Pansini 5, 80131 Naples, Italy
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15
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Giacco F, Perruolo G, D'Agostino E, Fratellanza G, Perna E, Misso S, Saldalamacchia G, Oriente F, Fiory F, Miele C, Formisano S, Beguinot F, Formisano P. Thrombin‐activated platelets induce proliferation of human skin fibroblasts by stimulating autocrine production of insulin‐like growth factor‐1. FASEB J 2006; 20:2402-4. [PMID: 17015410 DOI: 10.1096/fj.06-6104fje] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Platelet components have found successful clinical utilization to initiate or to accelerate tissue-repair mechanisms. However, the molecular pathways by which platelet factors contribute to tissue regeneration have not been fully elucidated. We have studied the effect of thrombin-activated platelets (TAPs) on cell growth in vivo and in cultured cell systems. Application of TAPs to ulcerative skin lesions of diabetic patients induced local activation of ERK1/2 and Akt/PKB. Moreover, when applied to cultured human skin fibroblasts, TAPs promoted cell growth and DNA synthesis and activated platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF)-1 receptor tyrosine kinases. PDGF was released by TAPs and rapidly achieved a plateau. At variance, the release of IGF-1 was mainly provided by the TAPs-stimulated fibroblasts and progressively increased up to 48 h. The PDGF-R blocker Ag1296 reduced the activation of Akt/PKB and, at a lesser extent, of ERK1/2. Conversely, inhibition of IGF-1 signaling by Ag1024 and expression of a dominant-negative IGF-1R mutant selectively reduced the stimulation of ERK1/2 by TAPs and fibroblast-released factors, with minor changes of Akt/PKB activity. Thus, platelet factors promote fibroblast growth by acutely activating Akt/PKB and ERK1/2. Sustained activation of ERK1/2, however, requires autocrine production of IGF-1 by TAPs-stimulated fibroblasts.
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Affiliation(s)
- Ferdinando Giacco
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università di Napoli Federico II, Via Pansini 5, 80131 Napoli, Italy
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16
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Sale EM, Hodgkinson CP, Jones NP, Sale GJ. A new strategy for studying protein kinase B and its three isoforms. Role of protein kinase B in phosphorylating glycogen synthase kinase-3, tuberin, WNK1, and ATP citrate lyase. Biochemistry 2006; 45:213-23. [PMID: 16388597 DOI: 10.1021/bi050287i] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein kinase B appears to play a key role in insulin signaling and in the control of apoptosis, although the precise targets of PKB are incompletely understood. PKB exists as three isoforms (alpha, beta, and gamma) that may have unique as well as common functions within the cell. To facilitate understanding the precise roles of PKB and its isoforms, novel tools of widespread applicability are described. These tools are antisense oligonucleotide probes that enable the specific and potent knock down of endogenous PKB alpha, beta, or gamma isoforms, individually or in various combinations, including concurrent removal of all three isoforms. The probes were applied to dissect the role of PKB in phosphorylating glycogen synthase kinase-3 (GSK-3), a critical mediator in multiple responses, and other potentially key targets. Triple antisense knock down of PKB alpha, beta, and gamma so that total PKB was <6% blocked insulin-stimulated phosphorylation of endogenous GSK-3alpha and GSK-3beta isoforms by 67% and 45%, respectively, showing that GSK-3alpha and GSK-3beta are controlled by endogenous PKB. Each PKB isoform contributed to GSK-3alpha and GSK-3beta phosphorylation, with PKBbeta having the predominant role. Knock down of total PKB incompletely blocked insulin-stimulated phosphorylation of GSK-3alpha and GSK-3beta, and a pathway involving atypical PKCs, zeta/lambda, was shown to contribute to the signal. Triple antisense knock down of PKB alpha, beta, and gamma abrogated the insulin-stimulated phosphorylation of WNK1, ATP citrate lyase, and tuberin. However, antisense-mediated knock down of PKB alpha, beta, and gamma had no effect on insulin-stimulated DNA synthesis in 3T3-L1 adipocytes, indicating that pathways other than PKB mediate this response in these cells. Finally, our PKB antisense strategy provides a method of general usefulness for further dissecting the precise targets and roles of PKB and its isoforms.
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Affiliation(s)
- Elizabeth M Sale
- School of Biological Sciences, University of Southampton, Southampton SO16 7PX, United Kingdom
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17
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Pongracz JE, Stockley RA. Wnt signalling in lung development and diseases. Respir Res 2006; 7:15. [PMID: 16438732 PMCID: PMC1397816 DOI: 10.1186/1465-9921-7-15] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2005] [Accepted: 01/26/2006] [Indexed: 12/12/2022] Open
Abstract
There are several signalling pathways involved in lung organogenesis including Notch, TGFbeta/BMP, Sonic hedgehog (Shh), FGF, EGF, and Wnt. Despite the widely acknowledged significance of Wnt signalling in embryonic lung development, the role of different Wnt pathways in lung pathologies has been slow to emerge. In this review, we will present a synopsis of current Wnt research with particular attention paid to the role of Wnt signals in lung development and in pulmonary diseases.
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Affiliation(s)
- Judit E Pongracz
- Department of Immunology and Biotechnology, University of Pécs, Pécs, Hungary
- Institute for Biomedical Research, University of Birmingham, Birmingham, UK
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18
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Glatt CM, Ouyang M, Welsh W, Green JW, Connor JO, Frame SR, Everds NE, Poindexter G, Snajdr S, Delker DA. Molecular characterization of thyroid toxicity: anchoring gene expression profiles to biochemical and pathologic end points. ENVIRONMENTAL HEALTH PERSPECTIVES 2005; 113:1354-61. [PMID: 16203246 PMCID: PMC1281279 DOI: 10.1289/ehp.7690] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Organic iodides have been shown to induce thyroid hypertrophy and increase alterations in colloid in rats, although the mechanism involved in this toxicity is unclear. To evaluate the effect that free iodide has on thyroid toxicity, we exposed rats for 2 weeks by daily gavage to sodium iodide (NaI). To compare the effects of compounds with alternative mechanisms (increased thyroid hormone metabolism and decreased thyroid hormone synthesis, respectively), we also examined phenobarbital (PB) and propylthiouracil (PTU) as model thyroid toxicants. Follicular cell hypertrophy and pale-staining colloid were present in thyroid glands from PB-treated rats, and more severe hypertrophy/colloid changes along with diffuse hyperplasia were present in thyroid glands from PTU-treated rats. In PB- and PTU-treated rats, thyroid-stimulating hormone (TSH) levels were significantly elevated, and both thyroxine and triiodothyronine hormone levels were significantly decreased. PB induced hepatic uridine diphosphate-glucuronyltransferase (UDPGT) activity almost 2-fold, whereas PTU reduced hepatic 5 -deiodinase I (5 -DI) activity to < 10% of control in support of previous reports regarding the mechanism of action of each chemical. NaI also significantly altered liver weights and UDPGT activity but did not affect thyroid hormone levels or thyroid pathology. Thyroid gene expression analyses using Affymetrix U34A GeneChips, a regularized t-test, and Gene Map Annotator and Pathway Profiler demonstrated significant changes in rhodopsin-like G-protein-coupled receptor transcripts from all chemicals tested. NaI demonstrated dose-dependent changes in multiple oxidative stress-related genes, as also determined by principal component and linear regression analyses. Differential transcript profiles, possibly relevant to rodent follicular cell tumor outcomes, were observed in rats exposed to PB and PTU, including genes involved in Wnt signaling and ribosomal protein expression.
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19
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Boissan M, Beurel E, Wendum D, Rey C, Lécluse Y, Housset C, Lacombe ML, Desbois-Mouthon C. Overexpression of insulin receptor substrate-2 in human and murine hepatocellular carcinoma. THE AMERICAN JOURNAL OF PATHOLOGY 2005; 167:869-77. [PMID: 16127164 PMCID: PMC1698721 DOI: 10.1016/s0002-9440(10)62058-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/24/2005] [Indexed: 12/16/2022]
Abstract
De-regulations in insulin and insulin-like growth factor (IGF) pathways may contribute to hepatocellular carcinoma. Although intracellular insulin receptor substrate-2 (IRS-2) is the main effector of insulin signaling in the liver, its role in hepatocarcinogenesis is unknown. Here, we show that IRS-2 was overexpressed in two murine models of hepatocarcinogenesis: administration of diethylnitrosamine and hepatic overexpression of SV40 large T antigen. In both models, IRS-2 overexpression was detected in preneoplastic lesions and at higher levels in tumoral nodules. IRS-2 overexpression associated with IGF-2 and IRS-1 overexpression and with GSK-3beta inhibition. Increased expression of IRS-2 was also detected in human hepatocellular carcinoma specimens and hepatoma cell lines. In murine and human hepatoma cells, IRS-2 protein induction associated with increased IRS-2 mRNA levels. The functionality of IRS-2 was demonstrated in Hep 3 B cells, in which IRS-2 tyrosine phosphorylation and its association with phosphatidylinositol-3 kinase were induced by IGF-2. Moreover, down-regulation of IRS-2 expression increased apoptosis in these cells. In conclusion, we demonstrate that IRS-2 is overexpressed in human and murine hepatocellular carcinoma. The emergence of IRS-2 overexpression at preneoplastic stages during experimental hepatocarcinogenesis and its protective effect against apoptosis suggest that IRS-2 contributes to liver tumor progression.
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Affiliation(s)
- Mathieu Boissan
- INSERM U.680, Universitié Pierre et Marie Curie, Paris, France
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20
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Abstract
The neuron is a prime example of a highly polarized cell. It is becoming clear that conserved protein complexes, which have been shown to regulate polarity in such diverse systems as the C. elegans zygote and mammalian epithelia, are also required for neuronal polarization. This review considers the role of these polarity proteins in axon specification and synaptogenesis.
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Affiliation(s)
- Giselle R Wiggin
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
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21
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Huang C, Thirone ACP, Huang X, Klip A. Differential contribution of insulin receptor substrates 1 versus 2 to insulin signaling and glucose uptake in l6 myotubes. J Biol Chem 2005; 280:19426-35. [PMID: 15764603 DOI: 10.1074/jbc.m412317200] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Insulin receptor substrates-1 and 2 (IRS-1 and IRS-2) are pivotal in relaying insulin signaling in insulin-responsive tissues such as muscle. However, the precise contribution of IRS-1 vis-a-vis IRS-2 in insulin-mediated metabolic and mitogenic responses has not been compared directly in differentiated muscle cells. This study aimed to determine the relative contribution of IRS-1 versus IRS-2 in these responses, using small interfering RNA (siRNA)-mediated specific gene silencing. In L6 myotubes, transfection of siRNA targeted specifically against IRS-1 (siIRS-1) or IRS-2 (siIRS-2) reduced the cognate protein expression by 70-75%. Insulin-induced ERK phosphorylation was much more sensitive to IRS-2 than IRS-1 ablation, whereas p38MAPK phosphorylation was reduced by 43 or 62% in myotubes treated with siIRS-1 or siIRS-2, respectively. Insulin-induced Akt1 and Akt2 phosphorylation was reduced in myotubes treated with siIRS-1, but only Akt2 phosphorylation was reduced in myotubes treated with siIRS-2. In contrast, siIRS-1 treatment caused a marked reduction in insulin-induced actin remodeling, glucose uptake, and GLUT4 translocation, and siIRS-2 was without effect on these responses. Notably, combined siIRS-1 and siIRS-2, although reducing each IRS by around 75%, caused no further drop in glucose uptake than that achieved with siIRS-1 alone, but abolished p38MAPK phosphorylation. We conclude that insulin-stimulated Akt1 phosphorylation, actin remodeling, GLUT4 translocation, and glucose uptake are regulated mainly by IRS-1, whereas IRS-2 contributes selectively to ERK signaling, and Akt2 and p38MAPK lie downstream of both IRS in muscle cells.
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Affiliation(s)
- Carol Huang
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
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22
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Kanzaki M, Mora S, Hwang JB, Saltiel AR, Pessin JE. Atypical protein kinase C (PKCzeta/lambda) is a convergent downstream target of the insulin-stimulated phosphatidylinositol 3-kinase and TC10 signaling pathways. ACTA ACUST UNITED AC 2004; 164:279-90. [PMID: 14734537 PMCID: PMC2172328 DOI: 10.1083/jcb.200306152] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Insulin stimulation of adipocytes resulted in the recruitment of atypical PKC (PKCzeta/lambda) to plasma membrane lipid raft microdomains. This redistribution of PKCzeta/lambda was prevented by Clostridium difficile toxin B and by cholesterol depletion, but was unaffected by inhibition of phosphatidylinositol (PI) 3-kinase activity. Expression of the constitutively active GTP-bound form of TC10 (TC10Q/75L), but not the inactive GDP-bound mutant (TC10/T31N), targeted PKCzeta/lambda to the plasma membrane through an indirect association with the Par6-Par3 protein complex. In parallel, insulin stimulation as well as TC10/Q75L resulted in the activation loop phosphorylation of PKCzeta. Although PI 3-kinase activation also resulted in PKCzeta/lambda phosphorylation, it was not recruited to the plasma membrane. Furthermore, insulin-induced GSK-3beta phosphorylation was mediated by both PI 3-kinase-PKB and the TC10-Par6-atypical PKC signaling pathways. Together, these data demonstrate that PKCzeta/lambda can serve as a convergent downstream target for both the PI 3-kinase and TC10 signaling pathways, but only the TC10 pathway induces a spatially restricted targeting to the plasma membrane.
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Affiliation(s)
- Makoto Kanzaki
- Dept. of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794-8651, USA
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23
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Moeschel K, Beck A, Weigert C, Lammers R, Kalbacher H, Voelter W, Schleicher ED, Häring HU, Lehmann R. Protein Kinase C-ζ-induced Phosphorylation of Ser318 in Insulin Receptor Substrate-1 (IRS-1) Attenuates the Interaction with the Insulin Receptor and the Tyrosine Phosphorylation of IRS-1. J Biol Chem 2004; 279:25157-63. [PMID: 15069075 DOI: 10.1074/jbc.m402477200] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin receptor substrate-1 (IRS-1) was recently identified as a novel upstream substrate for the insulin-activated protein kinase C (PKC)-zeta. This interaction down-regulates insulin signal transduction under hyper-insulinemic conditions. To clarify the molecular mechanism of this feedback loop, we sought to identify the PKC-zeta phosphorylation sites of IRS-1 and to investigate their biological significance. Upon incubation of recombinant IRS-1 fragments with PKC-zeta, we identified Ser(318) of rat IRS-1 (Ser(323) in human IRS-1) as the major in vitro phosphorylation site (confirmed by mutation of Ser(318) to alanine). To monitor phosphorylation of Ser(318) in cellular extracts, we prepared a polyclonal phosphosite-specific antibody. The biological significance was studied in baby hamster kidney cells stably expressing the insulin receptor (BHK(IR)). Using the phospho-Ser(318)-specific antibody we observed that insulin stimulates phosphorylation of Ser(318) in IRS-1, which is mediated, at least partially, by PKC-zeta. Moreover, we found that the previously described insulin-stimulated, PKC-zeta-mediated inhibition of the interaction of IRS-1 with the insulin receptor and the reduced tyrosine phosphorylation of IRS-1 was abrogated by mutation of IRS-1 Ser(318) to alanine. These results, generated in BHK(IR) cells, suggest that phosphorylation of Ser(318) by PKC-zeta might contribute to the inhibitory effect of prolonged hyperinsulinemia on IRS-1 function.
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Affiliation(s)
- Klaus Moeschel
- Department of Internal Medicine IV, Endocrinology, Metabolism, Pathobiochemistry and Clinical Chemistry, University Hospital Tübingen, D-72076 Tübingen, Germany
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24
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Fiory F, Oriente F, Miele C, Romano C, Trencia A, Alberobello AT, Esposito I, Valentino R, Beguinot F, Formisano P. Protein Kinase C-ζ and Protein Kinase B Regulate Distinct Steps of Insulin Endocytosis and Intracellular Sorting. J Biol Chem 2004; 279:11137-45. [PMID: 14711831 DOI: 10.1074/jbc.m308751200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have investigated the molecular mechanisms regulating insulin internalization and intracellular sorting. Insulin internalization was decreased by 50% upon incubation of the cells with the phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin and LY294002. PI3K inhibition also reduced insulin degradation and intact insulin release by 50 and 75%, respectively. Insulin internalization was reduced by antisense inhibition of protein kinase C-zeta (PKCzeta) expression and by overexpression of a dominant negative PKCzeta mutant (DN-PKCzeta). Conversely, overexpression of PKCzeta increased insulin internalization as a function of the PKCzeta levels achieved in the cells. Expression of wild-type protein kinase B (PKB)-alpha or of a constitutively active form (myr-PKB) did not significantly alter insulin internalization and degradation but produced a 100% increase of intact insulin release. Inhibition of PKB by a dominant negative mutant (DN-PKB) or by the pharmacological inhibitor ML-9 reduced intact insulin release by 75% with no effect on internalization and degradation. In addition, overexpression of Rab5 completely rescued the effect of PKCzeta inhibition on insulin internalization but not that of PKB inhibition on intact insulin recycling. Indeed, PKCzeta bound to and activated Rab5. Thus, PI3K controls different steps within the insulin endocytic itinerary. PKCzeta appears to mediate the PI3K effect on insulin internalization in a Rab5-dependent manner, whereas PKB directs intracellular sorting toward intact insulin release.
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Affiliation(s)
- Francesca Fiory
- Dipartimento di Biologia e Patologia Cellulare e Molecolare L. Califano and Istituto di Endocrinologia ed Oncologia Sperimentale del C.N.R., Università degli Studi di Napoli Federico II, Via S. Pansini, 5, 80131 Naples, Italy
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25
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Sarkissian M, Mendez R, Richter JD. Progesterone and insulin stimulation of CPEB-dependent polyadenylation is regulated by Aurora A and glycogen synthase kinase-3. Genes Dev 2004; 18:48-61. [PMID: 14724178 PMCID: PMC314275 DOI: 10.1101/gad.1136004] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Progesterone stimulation of Xenopus oocyte maturation requires the cytoplasmic polyadenylation-induced translation of mos and cyclin B mRNAs. One cis element that drives polyadenylation is the CPE, which is bound by the protein CPEB. Polyadenylation is stimulated by Aurora A (Eg2)-catalyzed CPEB serine 174 phosphorylation, which occurs soon after oocytes are exposed to progesterone. Here, we show that insulin also stimulates Aurora A-catalyzed CPEB S174 phosphorylation, cytoplasmic polyadenylation, translation, and oocyte maturation. However, these insulin-induced events are uniquely controlled by PI3 kinase and PKC-zeta, which act upstream of Aurora A. The intersection of the progesterone and insulin signaling pathways occurs at glycogen synthase kinase 3 (GSK-3), which regulates the activity of Aurora A. GSK-3 and Aurora A interact in vivo, and overexpressed GSK-3 inhibits Aurora A-catalyzed CPEB phosphorylation. In vitro, GSK-3 phosphorylates Aurora A on S290/291, the result of which is an autophosphorylation of serine 349. GSK-3 phosphorylated Aurora A, or Aurora A proteins with S290/291D or S349D mutations, have reduced or no capacity to phosphorylate CPEB. Conversely, Aurora A proteins with S290/291A or S349A mutations are constitutively active. These results suggest that the progesterone and insulin stimulate maturation by inhibiting GSK-3, which allows Aurora A activation and CPEB-mediated translation.
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Affiliation(s)
- Madathia Sarkissian
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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27
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Ossipova O, Bardeesy N, DePinho RA, Green JBA. LKB1 (XEEK1) regulates Wnt signalling in vertebrate development. Nat Cell Biol 2003; 5:889-94. [PMID: 12973359 DOI: 10.1038/ncb1048] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2003] [Accepted: 08/22/2003] [Indexed: 01/08/2023]
Abstract
Germline LKB1/STK11 mutations are associated with the cancer-prone Peutz-Jeghers syndrome (PJS) in humans, and nullizygosity provokes a poorly understood constellation of developmental perturbations in the mid-gestational mouse. To gain a better understanding of the processes regulated by LKB1, we have exploited the experimental merits of the developing Xenopus embryo. Here, specific inhibition of XEEK1, the Xenopus orthologue of LKB1, engendered developmental anomalies - shortened body axis and defective dorsoanterior patterning - associated previously with aberrant Wnt signalling. In line with this, LKB1/XEEK1 cooperates with the Wnt-beta-catenin signalling in axis induction and modulates the expression of Wnt-responsive genes in both Xenopus embryos and mammalian cells. We establish that LKB1/XEEK1 acts upstream of beta-catenin in the Wnt-beta-catenin pathway in vivo. LKB1/XEEK1 regulates glycogen synthase kinase (GSK)3beta phosphorylation and it is physically associated in vivo with GSK3beta and protein kinase C (PKC)-zeta, a known GSK3 kinase. These studies show that LKB1/XEEK1 is required for Wnt-beta-catenin signalling in frogs and mammals and provides novel insights into its role in vertebrate developmental patterning and carcinogenesis.
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Affiliation(s)
- Olga Ossipova
- Department of Cancer Biology, Dana Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA
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28
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Valverde AM, Burks DJ, Fabregat I, Fisher TL, Carretero J, White MF, Benito M. Molecular mechanisms of insulin resistance in IRS-2-deficient hepatocytes. Diabetes 2003; 52:2239-48. [PMID: 12941762 DOI: 10.2337/diabetes.52.9.2239] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
To assess the role of insulin receptor (IR) substrate (IRS)-2 in insulin action and resistance in the liver, immortalized neonatal hepatocyte cell lines have been generated from IRS-2(-/-), IRS-2(+/-), and wild-type mice. These cells maintained the expression of the differentiated liver markers albumin and carbamoyl phosphate synthetase, as well as bear a high number of IRs. The lack of IRS-2 did not result in enhanced IRS-1 tyrosine phosphorylation or IRS-1-associated phosphatidylinositol (PI) 3-kinase activity on insulin stimulation. Total insulin-induced PI 3-kinase activity was decreased by 50% in IRS-2(-/-) hepatocytes, but the translocation of PI-3,4,5-trisphosphate to the plasma membrane in these cells was almost completely abolished. Downstream PI 3-kinase, activation of Akt, glycogen synthase kinase (GSK)-3 (alpha and beta isoforms), Foxo1, and atypical protein kinase C were blunted in insulin-stimulated IRS-2(-/-) cells. Reconstitution of IRS-2(-/-) hepatocytes with adenoviral IRS-2 restored activation of these pathways, demonstrating that IRS-2 is essential for functional insulin signaling in hepatocytes. Insulin induced a marked glycogen synthase activity in wild-type and heterozygous primary hepatocytes; interestingly, this response was absent in IRS-2(-/-) cells but was rescued by infection with adenoviral IRS-2. Regarding gluconeogenesis, the induction of phosphoenolpyruvate carboxykinase and glucose 6-phosphatase by dibutyryl cAMP and dexamethasone was observed in primary hepatocytes of all genotypes. However, insulin was not able to suppress gluconeogenic gene expression in primary hepatocytes lacking IRS-2, but when IRS-2 signaling was reconstituted, these cells recovered this response to insulin. Suppression of gluconeogenic gene expression in IRS-2-deficient primary hepatocytes was also restored by infection with dominant negative Delta 256Foxo1.
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Affiliation(s)
- Angela M Valverde
- Instituto de Bioquímica/Departamento de Bioquímica y Biología Molecular II, Centro Mixto CSIC/UCM, Facultad de Farmacia, Universidad Complutense, Madrid, Spain.
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29
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Kim YB, Kotani K, Ciaraldi TP, Henry RR, Kahn BB. Insulin-stimulated protein kinase C lambda/zeta activity is reduced in skeletal muscle of humans with obesity and type 2 diabetes: reversal with weight reduction. Diabetes 2003; 52:1935-42. [PMID: 12882908 DOI: 10.2337/diabetes.52.8.1935] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In humans with obesity or type 2 diabetes, insulin target tissues are resistant to many actions of insulin. The atypical protein kinase C (PKC) isoforms lambda and zeta are downstream of phosphatidylinositol-3 kinase (PI3K) and are required for maximal insulin stimulation of glucose uptake. Phosphoinositide-dependent protein kinase-1 (PDK-1), also downstream of PI3K, mediates activation of atypical PKC isoforms and Akt. To determine whether impaired PKClambda/zeta or PDK-1 activation plays a role in the pathogenesis of insulin resistance, we measured the activities of PKClambda/zeta and PDK-1 in vastus lateralis muscle of lean, obese, and obese/type 2 diabetic humans. Biopsies were taken after an overnight fast and after a 3-h hyperinsulinemic-euglycemic clamp. Obese subjects were also studied after weight loss on a very-low-calorie diet. Insulin-stimulated glucose disposal rate is reduced 26% in obese subjects and 62% in diabetic subjects (both comparisons P < 0.001). Insulin-stimulated insulin receptor substrate (IRS)-1 tyrosine phosphorylation and PI3K activity are impaired 40-50% in diabetic subjects compared with lean or obese subjects. Insulin stimulates PKClambda/zeta activity approximately 2.3-fold in lean subjects; the increment above basal is reduced 57% in obese and 65% in diabetic subjects. PKClambda/zeta protein amount is decreased 46% in diabetic subjects but is normal in obese nondiabetic subjects, indicating impaired insulin action on PKClambda/zeta. Importantly, weight loss in obese subjects normalizes PKClambda/zeta activation and increases IRS-1 phosphorylation and PI3K activity. Insulin also stimulates PDK-1 activity approximately twofold with no impairment in obese or diabetic subjects. In contrast to our previous data on Akt, reduced insulin-stimulated PKClambda/zeta activity could play a role in the pathogenesis of insulin resistance in muscle of obese and type 2 diabetic subjects.
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Affiliation(s)
- Young-Bum Kim
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
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Andreozzi F, Melillo RM, Carlomagno F, Oriente F, Miele C, Fiory F, Santopietro S, Castellone MD, Beguinot F, Santoro M, Formisano P. Protein kinase Calpha activation by RET: evidence for a negative feedback mechanism controlling RET tyrosine kinase. Oncogene 2003; 22:2942-9. [PMID: 12771945 DOI: 10.1038/sj.onc.1206475] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have studied the role of protein kinase C (PKC) in signaling of the RET tyrosine kinase receptor. By using a chimeric receptor (E/R) in which RET kinase can be tightly controlled by the addition of epidermal growth factor (EGF), we have found that RET triggering induces a strong increase of PKCalpha, PKCdelta and PKCzeta activity and that PKCalpha, not PKCdelta and PKCzeta, forms a ligand-dependent protein complex with E/R. We have identified tyrosine 1062 in the RET carboxyl-terminal tail as the docking site for PKCalpha. Block of PKC activity by bisindolylmaleimide or chronic phorbol esters treatment decreased EGF-induced serine/threonine phosphorylation of E/R, while it caused a similarly sized increase of EGF-induced E/R tyrosine kinase activity and mitogenic signaling. Conversely, acute phorbol esters treatment, which promotes PKC activity, increased the levels of E/R serine/threonine phosphorylation and significantly decreased its phosphotyrosine content. A threefold reduction of tyrosine phosphorylation levels of the constitutively active RET/MEN2A oncoprotein was observed upon coexpression with PKCalpha. We conclude that RET binds to and activates PKCalpha. PKCalpha, in turn, causes RET phosphorylation and downregulates RET tyrosine kinase and downstream signaling, thus functioning as a negative feedback loop to modulate RET activity.
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Affiliation(s)
- Francesco Andreozzi
- Dipartimento di Biologia e Patologia Cellulare e Molecolare 'L Califano', Università degli Studi di Napoli 'Federico II', via S Pansini 5, 80131 Napoli, Italy
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31
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Kim JW, Lee JE, Kim MJ, Cho EG, Cho SG, Choi EJ. Glycogen synthase kinase 3 beta is a natural activator of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 1 (MEKK1). J Biol Chem 2003; 278:13995-4001. [PMID: 12584189 DOI: 10.1074/jbc.m300253200] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glycogen synthase kinase 3beta (GSK3 beta) is implicated in many biological events, including embryonic development, cell differentiation, apoptosis, and insulin response. GSK3 beta has now been shown to induce activation of the mitogen-activated protein kinase kinase kinase MEKK1 and thereby to promote signaling by the stress-activated protein kinase pathway. GSK3 beta-binding protein blocked the activation of MEKK1 by GSK3 beta in human embryonic kidney 293 (HEK293) cells. Furthermore, co-immunoprecipitation analysis revealed a physical association between endogenous GSK3 beta and MEKK1 in HEK293 cells. Overexpression of axin1, a GSK3 beta-regulated scaffolding protein, did not affect the physical interaction between GSK3 beta and MEKK1 in transfected HEK293 cells. Exposure of cells to insulin inhibited the activation of MEKK1 by GSK3 beta, and this inhibitory effect of insulin was abolished by the phosphatidylinositol 3-kinase inhibitor wortmannin. Furthermore, MEKK1 activity under either basal or UV- or tumor necrosis factor alpha-stimulated conditions was reduced in embryonic fibroblasts derived from GSK3 beta knockout mice compared with that in such cells from wild-type mice. Ectopic expression of GSK3 beta increased both basal and tumor necrosis factor alpha-stimulated activities of MEKK1 in GSK3 beta(-/-) cells. Together, these observations suggest that GSK3 beta functions as a natural activator of MEKK1.
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Affiliation(s)
- Jin Woo Kim
- National Creative Research Initiative Center for Cell Death, Graduate School of Life Science and Biotechnology, Korea University, Seoul 136-701, Korea
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Etienne-Manneville S, Hall A. Cdc42 regulates GSK-3beta and adenomatous polyposis coli to control cell polarity. Nature 2003; 421:753-6. [PMID: 12610628 DOI: 10.1038/nature01423] [Citation(s) in RCA: 671] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2002] [Accepted: 01/14/2003] [Indexed: 12/31/2022]
Abstract
Cell polarity is a fundamental property of all cells. In higher eukaryotes, the small GTPase Cdc42, acting through a Par6-atypical protein kinase C (aPKC) complex, is required to establish cellular asymmetry during epithelial morphogenesis, asymmetric cell division and directed cell migration. However, little is known about what lies downstream of this complex. Here we show, through the use of primary rat astrocytes in a cell migration assay, that Par6-PKCzeta interacts directly with and regulates glycogen synthase kinase-3beta (GSK-3beta) to promote polarization of the centrosome and to control the direction of cell protrusion. Cdc42-dependent phosphorylation of GSK-3beta occurs specifically at the leading edge of migrating cells, and induces the interaction of adenomatous polyposis coli (Apc) protein with the plus ends of microtubules. The association of Apc with microtubules is essential for cell polarization. We conclude that Cdc42 regulates cell polarity through the spatial regulation of GSK-3beta and Apc. This role for Apc may contribute to its tumour-suppressor activity.
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Affiliation(s)
- Sandrine Etienne-Manneville
- MRC Laboratory for Molecular Cell Biology and Cell Biology Unit, Cancer Research UK Oncogene and Signal Transduction Group, and Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK
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Arribas M, Valverde AM, Burks D, Klein J, Farese RV, White MF, Benito M. Essential role of protein kinase C zeta in the impairment of insulin-induced glucose transport in IRS-2-deficient brown adipocytes. FEBS Lett 2003; 536:161-6. [PMID: 12586357 DOI: 10.1016/s0014-5793(03)00049-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Insulin receptor substrate-2-deficient (IRS-2(-/-)) mice develop type 2 diabetes. We have investigated the molecular mechanisms by which IRS-2(-/-) immortalized brown adipocytes showed an impaired response to insulin in inducing GLUT4 translocation and glucose uptake. IRS-2-associated phosphatidylinositol 3-kinase (PI 3-kinase) activity was blunted in IRS-2(-/-) cells, total PI 3-kinase activity being reduced by 30%. Downstream, activation of protein kinase C (PKC) zeta was abolished in IRS-2(-/-) cells. Reconstitution with retroviral IRS-2 restores IRS-2/PI 3-kinase/PKC zeta signalling, as well as glucose uptake. Wild-type cells expressing a kinase-inactive mutant of PKC zeta lack GLUT4 translocation and glucose uptake. Our results support the essential role played by PKC zeta in the insulin resistance and impaired glucose uptake observed in IRS-2-deficient brown adipocytes.
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Affiliation(s)
- Mónica Arribas
- Departamento de Bioquímica y Biología Molecular/Instituto de Bioquímica, Centro Mixto CSIC/UCM, Facultad de Farmacia, Universidad Complutense, 28040 Madrid, Spain
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Kim YB, Shulman GI, Kahn BB. Fatty acid infusion selectively impairs insulin action on Akt1 and protein kinase C lambda /zeta but not on glycogen synthase kinase-3. J Biol Chem 2002; 277:32915-22. [PMID: 12095990 DOI: 10.1074/jbc.m204710200] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To determine the mechanism(s) for insulin resistance induced by fatty acids, we measured the ability of insulin to activate phosphoinositide 3-kinase (PI3K) and multiple distal pathways in rats. Following a 5-h infusion of lipid or glycerol (control), rats underwent a euglycemic hyperinsulinemic clamp. Insulin stimulated IRS-1-associated PI3K activity in muscle of glycerol-infused rats 2.4-fold but had no effect in lipid-infused rats. IRS-2- and phosphotyrosine-associated PI3K activity were increased 3.5- and 4.8-fold, respectively, by insulin in glycerol-infused rats but only 1.6- and 2.3-fold in lipid-infused rats. Insulin increased Akt1 activity 3.9-fold in glycerol-infused rats, and this was impaired 41% in lipid-infused rats. Insulin action on Akt2 and p70S6K were not impaired, whereas activation of protein kinase C lambda/zeta activity was reduced 47%. Insulin inhibited glycogen synthase kinase 3alpha (GSK-3alpha) activity by 30% and GSK-3beta activity by approximately 65% and increased protein phosphatase-1 activity by 40-47% in both glycerol- and lipid-infused rats. Insulin stimulated glycogen synthase activity 2.0-fold in glycerol-infused rats but only 1.4-fold in lipid-infused rats. Thus, 1) elevation of fatty acids differentially affects insulin action on pathways distal to PI3K, impairing activation of Akt1 and protein kinase C lambda/zeta and 2) insulin action on glycogen synthase can be regulated independent of effects on GSK-3 and protein phosphatase-1 activity in vivo.
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Affiliation(s)
- Young-Bum Kim
- Diabetes Unit, Division of Endocrinology and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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Hodgkinson CP, Sale EM, Sale GJ. Characterization of PDK2 activity against protein kinase B gamma. Biochemistry 2002; 41:10351-9. [PMID: 12162751 DOI: 10.1021/bi026065r] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein kinase B (PKB), also known as Akt, is a serine/threonine protein kinase controlled by insulin, various growth factors, and phosphatidylinositol 3-kinase. Full activation of the PKB enzyme requires phosphorylation of a threonine in the activation loop and a serine in the C-terminal tail. PDK1 has clearly been shown to phosphorylate the threonine, but the mechanism leading to phosphorylation of the serine, the PDK2 site, is unclear. A yeast two-hybrid screen using full-length human PKBgamma identified protein kinase C (PKC) zeta, an atypical PKC, as an interactor with PKBgamma, an association requiring the pleckstrin homology domain of PKBgamma. Endogenous PKBgamma was shown to associate with endogenous PKCzeta both in cos-1 cells and in 3T3-L1 adipocytes, demonstrating a physiological interaction. Immunoprecipitates of PKCzeta, whether endogenous PKCzeta from insulin-stimulated 3T3-L1 adipocytes or overexpressed PKCzeta from cos-1 cells, phosphorylated S472 (the C-terminal serine phosphorylation site) of PKBgamma, in vitro. In vivo, overexpression of PKCzeta stimulated the phosphorylation of approximately 50% of the PKBgamma molecules, suggesting a physiologically meaningful effect. However, pure PKCzeta protein was incapable of phosphorylating S472 of PKBgamma. Antisense knockout studies and use of a PDK1 inhibitor showed that neither PKB autophosphorylation nor phosphorylation by PDK1 accounted for the S472 phosphorylation in PKCzeta immunoprecipitates. Staurosporine inhibited the PKCzeta activity but not the PDK2 activity in PKCzeta immunoprecipitates. Together these results indicate that an independent PDK2 activity exists that physically associates with PKCzeta and that PKCzeta, by binding PKBgamma, functions to deliver the PDK2 to a required location. PKCzeta thus functions as an adaptor, associating with a staurosporine-insensitive PDK2 enzyme that catalyzes the phosphorylation of S472 of PKBgamma. Because both PKCzeta and PKB have been proposed to be required for mediating a number of crucial insulin responses, formation of an active signaling complex containing PKCzeta, PKB, and PDK2 is an attractive mechanism for ensuring that all the critical sites on targets such as glycogen synthase kinase-3 are phosphorylated.
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Affiliation(s)
- Conrad P Hodgkinson
- Division of Biochemistry and Molecular Biology, School of Biological Sciences, University of Southampton, Southampton SO16 7PX, United Kingdom
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Matsumoto M, Ogawa W, Teshigawara K, Inoue H, Miyake K, Sakaue H, Kasuga M. Role of the insulin receptor substrate 1 and phosphatidylinositol 3-kinase signaling pathway in insulin-induced expression of sterol regulatory element binding protein 1c and glucokinase genes in rat hepatocytes. Diabetes 2002; 51:1672-80. [PMID: 12031952 DOI: 10.2337/diabetes.51.6.1672] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The mechanism by which insulin induces the expression of the sterol regulatory element binding protein 1c (SREBP-1c) and glucokinase genes was investigated in cultured rat hepatocytes. Overexpression of an NH(2)-terminal fragment of IRS-1 that contains the pleckstrin homology and phosphotyrosine binding domains (insulin receptor substrate-1 NH(2)-terminal fragment [IRS-1N]) inhibited insulin-induced tyrosine phosphorylation of IRS-1 as well as the association of IRS-1 with phosphatidylinositol (PI) 3-kinase activity, whereas the tyrosine phosphorylation of IRS-2 and its association with PI 3-kinase activity were slightly enhanced. The equivalent fragment of IRS-2 (IRS-2N) prevented insulin-induced tyrosine phosphorylation of both IRS-1 and IRS-2, although that of IRS-1 was inhibited more efficiently. The insulin-induced increases in the abundance of SREBP-1c and glucokinase mRNAs, both of which were sensitive to a dominant-negative mutant of PI 3-kinase, were blocked in cells in which the insulin-induced tyrosine phosphorylation of IRS-1 was inhibited by IRS-1N or IRS-2N. A dominant-negative mutant of Akt enhanced insulin-induced tyrosine phosphorylation of IRS-1 (but not that of IRS-2) and its association with PI 3-kinase activity, suggesting that Akt contributes to negative feedback regulation of IRS-1. The Akt mutant also promoted the effects of insulin on the accumulation of SREBP-1c and glucokinase mRNAs. These results suggest that the IRS-1-PI 3-kinase pathway is essential for insulin-induced expression of SREBP-1c and glucokinase genes.
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Affiliation(s)
- Michihiro Matsumoto
- Department of Clinical Molecular Medicine, Division of Diabetes, Digestive, and Kidney Diseases, Kobe University Graduate School of Medicine, Kobe, Japan
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Vollenweider P, Ménard B, Nicod P. Insulin resistance, defective insulin receptor substrate 2-associated phosphatidylinositol-3' kinase activation, and impaired atypical protein kinase C (zeta/lambda) activation in myotubes from obese patients with impaired glucose tolerance. Diabetes 2002; 51:1052-9. [PMID: 11916925 DOI: 10.2337/diabetes.51.4.1052] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Impaired glucose tolerance (IGT) is characterized by insulin resistance. Recently, defects in the insulin-signaling cascade have been implicated in the pathogenesis of insulin resistance. To study insulin signaling in IGT, we used human skeletal muscle cells in primary culture from patients with IGT and control subjects. In these cultured myotubes, we assessed insulin-induced 2-deoxyglucose uptake and early steps of the metabolic insulin-signaling cascade. Myotubes in culture from patients with IGT had insulin-induced glucose uptake that was roughly 30-50% less than that from control subjects. This insulin resistance was associated with impaired insulin receptor substrate (IRS)-2-associated phosphatidylinositol 3' (PI3) kinase activation and IRS-2 tyrosine phosphorylation as well as significantly decreased protein kinase C (PKC)-zeta/lambda activation in response to insulin. IRS-1- associated PI3 kinase activation and insulin receptor autophosphorylation were comparable in the two groups. Protein expression levels for the insulin receptor, IRS-1, IRS-2, the p85 regulatory subunit of PI3 kinase, Akt, PKC-zeta/lambda, GLUT1, and GLUT4 were also similar in the two groups. In conclusion, myotubes from patients with IGT have impaired insulin-induced glucose uptake. This is associated with impaired IRS-2-associated PI3 kinase activation and PKC-zeta/lambda activation. Our results suggest that these defects may contribute to insulin resistance in IGT patients.
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Affiliation(s)
- Peter Vollenweider
- Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
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