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Pyruvate dehydrogenase kinase 4 (PDK4) could be involved in a regulatory role in apoptosis and a link between apoptosis and insulin resistance. Exp Mol Pathol 2015; 98:574-84. [DOI: 10.1016/j.yexmp.2015.03.022] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 03/16/2015] [Indexed: 12/14/2022]
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Jones ML, Liao GY, Malecki R, Li M, Salazar NM, Leonard JP. PI 3-kinase and PKCζ mediate insulin-induced potentiation of NMDA receptor currents in Xenopus oocytes. Brain Res 2011; 1432:7-14. [PMID: 22137655 DOI: 10.1016/j.brainres.2011.11.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 11/04/2011] [Accepted: 11/05/2011] [Indexed: 10/15/2022]
Abstract
Insulin modulates N-methyl-d-aspartate (NMDA) receptors in the CNS and potentiates recombinant NMDA receptor currents in Xenopus oocytes. We have previously found that insulin's potentiation of NMDA receptor currents in oocytes occurs in a subunit specific manner and via phosphorylation of specific C-terminal sites by protein tyrosine kinases (PTKs) and C-type protein kinases (PKCs). Insulin-mediated current potentiation of receptors containing the NR2A subunit occurs solely through the activation of PKCs. Activation of phosphoinositide 3-kinase (PI 3-kinase) is known to trigger many insulin-stimulated signaling pathways, and we show here that it lies at a critical step in the insulin-mediated potentiation of NMDA receptor currents. Incubation with the PI 3-kinase inhibitor wortmannin eliminates insulin potentiation of NMDA receptor currents in the oocytes. Atypical isoforms of PKC are known to be activated downstream in the insulin signaling pathway via activation of PI 3-kinase. We demonstrate that the atypical isoform PKC zeta (PKCζ) has a role in insulin-stimulated current potentiation of NR2A-containing NMDA receptors using an isoform-specific pseudosubstrate inhibitor of PKCζ.
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Affiliation(s)
- Michelle L Jones
- University of Illinois at Chicago, Department of Biological Sciences and Laboratory for Integrative Neuroscience, Chicago, IL 60607, USA
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Bezy O, Tran TT, Pihlajamäki J, Suzuki R, Emanuelli B, Winnay J, Mori MA, Haas J, Biddinger SB, Leitges M, Goldfine AB, Patti ME, King GL, Kahn CR. PKCδ regulates hepatic insulin sensitivity and hepatosteatosis in mice and humans. J Clin Invest 2011; 121:2504-17. [PMID: 21576825 DOI: 10.1172/jci46045] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Accepted: 03/30/2011] [Indexed: 12/27/2022] Open
Abstract
C57BL/6J and 129S6/Sv (B6 and 129) mice differ dramatically in their susceptibility to developing diabetes in response to diet- or genetically induced insulin resistance. A major locus contributing to this difference has been mapped to a region on mouse chromosome 14 that contains the gene encoding PKCδ. Here, we found that PKCδ expression in liver was 2-fold higher in B6 versus 129 mice from birth and was further increased in B6 but not 129 mice in response to a high-fat diet. PRKCD gene expression was also elevated in obese humans and was positively correlated with fasting glucose and circulating triglycerides. Mice with global or liver-specific inactivation of the Prkcd gene displayed increased hepatic insulin signaling and reduced expression of gluconeogenic and lipogenic enzymes. This resulted in increased insulin-induced suppression of hepatic gluconeogenesis, improved glucose tolerance, and reduced hepatosteatosis with aging. Conversely, mice with liver-specific overexpression of PKCδ developed hepatic insulin resistance characterized by decreased insulin signaling, enhanced lipogenic gene expression, and hepatosteatosis. Therefore, changes in the expression and regulation of PKCδ between strains of mice and in obese humans play an important role in the genetic risk of hepatic insulin resistance, glucose intolerance, and hepatosteatosis; and thus PKCδ may be a potential target in the treatment of metabolic syndrome.
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Affiliation(s)
- Olivier Bezy
- Joslin Diabetes Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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Chappell DS, Patel NA, Jiang K, Li P, Watson JE, Byers DM, Cooper DR. Functional involvement of protein kinase C-betaII and its substrate, myristoylated alanine-rich C-kinase substrate (MARCKS), in insulin-stimulated glucose transport in L6 rat skeletal muscle cells. Diabetologia 2009; 52:901-11. [PMID: 19252893 PMCID: PMC2677811 DOI: 10.1007/s00125-009-1298-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Accepted: 01/19/2009] [Indexed: 12/17/2022]
Abstract
AIMS/HYPOTHESIS Insulin stimulates phosphorylation cascades, including phosphatidylinositol-3-kinase (PI3K), phosphatidylinositol-dependent kinase (PDK1), Akt, and protein kinase C (PKC). Myristoylated alanine-rich C-kinase substrate (MARCKS), a PKCbetaII substrate, could link the effects of insulin to insulin-stimulated glucose transport (ISGT) via phosphorylation of its effector domain since MARCKS has a role in cytoskeletal rearrangements. METHODS We examined phosphoPKCbetaII after insulin treatment of L6 myocytes, and cytosolic and membrane phosphoMARCKS, MARCKS and phospholipase D1 in cells pretreated with LY294002 (PI3K inhibitor), CG53353 (PKCbetaII inhibitor) or W13 (calmodulin inhibitor), PI3K, PKCbetaII and calmodulin inhibitors, respectively, before insulin treatment, using western blots. ISGT was examined after cells had been treated with inhibitors, small inhibitory RNA (siRNA) for MARCKS, or transfection with MARCKS mutated at a PKC site. MARCKS, PKCbetaII, GLUT4 and insulin receptor were immunoblotted in subcellular fractions with F-actin antibody immunoprecipitates to demonstrate changes following insulin treatment. GLUT4 membrane insertion was followed after insulin with or without CG53353. RESULTS Insulin increased phosphoPKCbetaII(Ser660 and Thr641); LY294002 blocked this, indicating its activation by PI3K. Insulin treatment increased cytosolic phosphoMARCKS, decreased membrane MARCKS and increased membrane phospholipase D1 (PLD1), a protein regulating glucose transporter vesicle fusion resulted. PhosphoMARCKS was attenuated by CG53353 or MARCKS siRNA. MARCKS siRNA blocked ISGT. Association of PKCbetaII and GLUT4 with membrane F-actin was enhanced by insulin, as was that of cytosolic and membrane MARCKS. ISGT was attenuated in myocytes transfected with mutated MARCKS (Ser152Ala), whereas overproduction of wild-type MARCKS enhanced ISGT. CG53353 blocked insertion of GLUT4 into membranes of insulin treated cells. CONCLUSIONS/INTERPRETATION The results suggest that PKCbetaII is involved in mediating downstream steps of ISGT through MARCKS phosphorylation and cytoskeletal remodelling.
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Affiliation(s)
- D. S. Chappell
- Department of Molecular Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, Tampa, FL 33612, USA
| | - N. A. Patel
- Department of Molecular Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, Tampa, FL 33612, USA
- The Research Service, James A. Haley Veterans Hospital, Tampa, FL, USA
| | - K. Jiang
- Department of Molecular Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, Tampa, FL 33612, USA
| | - P. Li
- Department of Molecular Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, Tampa, FL 33612, USA
| | - J. E. Watson
- The Research Service, James A. Haley Veterans Hospital, Tampa, FL, USA
| | - D. M. Byers
- Atlantic Research Centre, Departments of Pediatrics and Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, Canada
| | - D. R. Cooper
- Department of Molecular Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, Tampa, FL 33612, USA, e-mail:
- The Research Service, James A. Haley Veterans Hospital, Tampa, FL, USA
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Cassese A, Esposito I, Fiory F, Barbagallo APM, Paturzo F, Mirra P, Ulianich L, Giacco F, Iadicicco C, Lombardi A, Oriente F, Van Obberghen E, Beguinot F, Formisano P, Miele C. In skeletal muscle advanced glycation end products (AGEs) inhibit insulin action and induce the formation of multimolecular complexes including the receptor for AGEs. J Biol Chem 2008; 283:36088-99. [PMID: 18955497 DOI: 10.1074/jbc.m801698200] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Chronic hyperglycemia promotes insulin resistance at least in part by increasing the formation of advanced glycation end products (AGEs). We have previously shown that in L6 myotubes human glycated albumin (HGA) induces insulin resistance by activating protein kinase Calpha (PKCalpha). Here we show that HGA-induced PKCalpha activation is mediated by Src. Coprecipitation experiments showed that Src interacts with both the receptor for AGE (RAGE) and PKCalpha in HGA-treated L6 cells. A direct interaction of PKCalpha with Src and insulin receptor substrate-1 (IRS-1) has also been detected. In addition, silencing of IRS-1 expression abolished HGA-induced RAGE-PKCalpha co-precipitation. AGEs were able to induce insulin resistance also in vivo, as insulin tolerance tests revealed a significant impairment of insulin sensitivity in C57/BL6 mice fed a high AGEs diet (HAD). In tibialis muscle of HAD-fed mice, insulin-induced glucose uptake and protein kinase B phosphorylation were reduced. This was paralleled by a 2.5-fold increase in PKCalpha activity. Similarly to in vitro observations, Src phosphorylation was increased in tibialis muscle of HAD-fed mice, and co-precipitation experiments showed that Src interacts with both RAGE and PKCalpha. These results indicate that AGEs impairment of insulin action in the muscle might be mediated by the formation of a multimolecular complex including RAGE/IRS-1/Src and PKCalpha.
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Affiliation(s)
- Angela Cassese
- Dipartimento di Biologia e Patologia Cellulare e Molecolare and Istituto di Endocrinologia ed Oncologia Sperimentale del Consiglio Nazionale delle Ricerche, Università degli Studi di Napoli Federico II, Naples 80131, Italy
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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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Kunt T, Forst T, Kazda C, Harzer O, Engelbach M, Löbig M, Beyer J, Pfützner A. The beta-specific protein kinase C inhibitor ruboxistaurin (LY333531) suppresses glucose-induced adhesion of human monocytes to endothelial cells in vitro. J Diabetes Sci Technol 2007; 1:929-35. [PMID: 19885168 PMCID: PMC2769672 DOI: 10.1177/193229680700100620] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
AIMS Strong evidence shows that late diabetic complications in diabetes mellitus are substantially related to an increased synthesis of diacylglycerol with a subsequent activation of protein kinase C (PKC) beta. Several studies have shown that specific inhibition of the PKC isoform beta by ruboxistaurin is able to attenuate the development of microvascular complications under diabetic conditions. The aim of this in vitro study was to investigate the effect of ruboxistaurin on glucose-induced adhesion of monocytes to endothelial cells, representing one of the first pivotal steps in the course of atherogenesis. METHODS Human umbilical venous endothelial cells were isolated and cultured to confluence in microtiter plates. After coincubation with monocytes in the presence of 0, 10, or 400 ng ruboxistaurin to achieve PKC beta-specific and -unspecific PKC inhibition, cells were fixed and monocyte adhesion was determined by means of a standardized chemiluminescence assay. Expression of adhesion molecules (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin) was also measured by chemiluminescence methods. RESULTS Adhesion of monocytes to endothelial cells cultured under hyperglycemic conditions (27.7 mM glucose) was increased by 30.9 +/- 5.1% (p < 0.001) versus endothelial cells cultured under normoglycemic (NG) conditions (5.5 mM). Pretreatment of endothelial cells with 10 nM (PKC beta-specific concentration) and 400 nM (PKC beta-unspecific concentration) led to a significant reduction of glucose-induced adhesion of monocytes to endothelial cells that was statistically not different from endothelial adhesion under NG conditions (-7.2 +/- 3.1 and -8.1 +/- 2.6%, respectively; not significant vs NG). A nonsignificant tendency to lower the expression of adhesion molecules was seen with 10 ng of ruboxistaurin. CONCLUSIONS We conclude that monocyte adhesion to endothelial cells under hyperglycemic conditions is at least mediated by PKC beta activation. Ruboxistaurin is able to suppress this monocyte adhesion even in a PKC beta-specific concentration. Further studies should evaluate these potential effects of ruboxistaurin in vivo.
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Affiliation(s)
| | - Thomas Forst
- Institute for Clinical Research and Development (ikfe), Mainz, Germany
| | | | | | | | - Mirjam Löbig
- Institute for Clinical Research and Development (ikfe), Mainz, Germany
| | - Jürgen Beyer
- University Hospital, Department of Endocrinology and Metabolism, Mainz, Germany (retired)
| | - Andreas Pfützner
- Institute for Clinical Research and Development (ikfe), Mainz, Germany
- University of Applied Sciences, Rheinbach, Germany
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Rypka M, Červenková K, Uherková L, Poczatková H, Bogdanová K, Veselý J. CHANGES IN mRNA LEVELS OF INTRACELLULAR FATTY ACID METABOLISM REGULATORS IN HUMAN HEPATOMA HepG2 CELLS FOLLOWING THEIR TREATMENT WITH NON-ESTERIFIED FATTY ACIDS AND DEHYDROEPIANDROSTERONE. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub 2005. [DOI: 10.5507/bp.2005.034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Oriente F, Andreozzi F, Romano C, Perruolo G, Perfetti A, Fiory F, Miele C, Beguinot F, Formisano P. Protein kinase C-alpha regulates insulin action and degradation by interacting with insulin receptor substrate-1 and 14-3-3 epsilon. J Biol Chem 2005; 280:40642-9. [PMID: 16216880 DOI: 10.1074/jbc.m508570200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Protein kinase C (PKC)-alpha exerts a regulatory function on insulin action. We showed by overlay blot that PKCalpha directly binds a 180-kDa protein, corresponding to IRS-1, and a 30-kDa molecular species, identified as 14-3-3epsilon. In intact NIH-3T3 cells overexpressing insulin receptors (3T3-hIR), insulin selectively increased PKCalpha co-precipitation with IRS-1, but not with IRS-2, and with 14-3-3epsilon, but not with other 14-3-3 isoforms. Overexpression of 14-3-3epsilon in 3T3-hIR cells significantly reduced IRS-1-bound PKCalpha activity, without altering IRS-1/PKCalpha co-precipitation. 14-3-3epsilon overexpression also increased insulin-stimulated insulin receptor and IRS-1 tyrosine phosphorylation, followed by increased activation of Raf1, ERK1/2, and Akt/protein kinase B. Insulin-induced glycogen synthase activity and thymidine incorporation were also augmented. Consistently, selective depletion of 14-3-3epsilon by antisense oligonucleotides caused a 3-fold increase of IRS-1-bound PKCalpha activity and a similarly sized reduction of insulin receptor and IRS-1 tyrosine phosphorylation and signaling. In turn, selective inhibition of PKCalpha expression by antisense oligonucleotides reverted the negative effect of 14-3-3epsilon depletion on insulin signaling. Moreover, PKCalpha inhibition was accompanied by a >2-fold decrease of insulin degradation. Similar results were also obtained by overexpressing 14-3-3epsilon. Thus, in NIH-3T3 cells, insulin induces the formation of multimolecular complexes, including IRS-1, PKCalpha, and 14-3-3epsilon. The presence of 14-3-3epsilon in the complex is not necessary for IRS-1/PKCalpha interaction but modulates PKCalpha activity, thereby regulating insulin signaling and degradation.
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Affiliation(s)
- Francesco Oriente
- Dipartimento di Biologia e Patologia Cellulare e Molecolare and Istituto di Endocrinologia ed Oncologia Sperimentale del CNR, Federico II University of Naples, Italy
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Pillay TS, Xiao S, Keranen L, Olefsky JM. Regulation of the insulin receptor by protein kinase C isoenzymes: preferential interaction with beta isoenzymes and interaction with the catalytic domain of betaII. Cell Signal 2004; 16:97-104. [PMID: 14607280 DOI: 10.1016/s0898-6568(03)00090-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We analysed the effects of high glucose in rat1 cells overexpressing insulin receptor. High (25 mM) glucose inhibited insulin-stimulated tyrosine kinase activity completely at insulin concentrations of 1 and 5 ng/ml. Decapeptides modelled on insulin receptor sequences surrounding serines 1035 and 1270 were found to inhibit protein kinase C activity in vitro and after microinjection into cells blocked the inhibition of mitogenesis induced by glucose. Purification of receptor from 3T3L1 adipocytes revealed that only the isoenzymes beta1, betaII and delta were detected. The site of the interaction was mapped to the catalytic domain of betaII. These results demonstrate that the inhibition of insulin receptor tyrosine kinase activity can be ameliorated using insulin receptor peptide sequences and there is constitutive and differential interaction of individual PKC isoenzymes with the insulin receptor, and in the case of betaII, this interaction maps to the catalytic domain rather than the regulatory domain.
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Affiliation(s)
- Tahir S Pillay
- Division of Endocrinology and Metabolism, Department of Medicine, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0673, USA.
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Bernier M, He HJ, Kwon YK, Jang HJ. The roles of phospholipase C-gamma 1 and actin-binding protein filamin A in signal transduction of the insulin receptor. VITAMINS AND HORMONES 2004; 69:221-47. [PMID: 15196884 DOI: 10.1016/s0083-6729(04)69008-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Michel Bernier
- Diabetes Section, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224, USA
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Probst I, Beuers U, Drabent B, Unthan-Fechner K, Bütikofer P. The diacylglycerol and protein kinase C pathways are not involved in insulin signalling in primary rat hepatocytes. ACTA ACUST UNITED AC 2004; 270:4635-46. [PMID: 14622250 DOI: 10.1046/j.1432-1033.2003.03853.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Diacylglycerol (DAG) and protein kinase C (PKC) isoforms have been implicated in insulin signalling in muscle and fat cells. We evaluated the involvement of DAG and PKC in the action of insulin in adult rat hepatocytes cultured with dexamethasone, but in the absence of serum, for 48 h. Our results show that although insulin stimulated glycolysis and glycogen synthesis, it had no effect on DAG mass or molecular species composition. Epidermal growth factor showed the expected insulin-mimetic effect on glycolysis, whereas ATP and exogenous phospholipase C acted as antagonists and abolished the insulin signal. Similarly to insulin, epidermal growth factor had no effect on DAG mass or molecular species composition. In contrast, both ATP and phospholipase C induced a prominent increase in several DAG molecular species, including 18:0/20:4, 18:0/20:5, 18:0/22:5 and a decrease in 18:1/18:1. These changes were paralleled by an increase in phospholipase D activity, which was absent in insulin-treated cells. By immunoblotting or by measuring PKC activity, we found that neither insulin nor ATP translocated the PKCalpha, -delta, -epsilon or -zeta isoforms from the cytosol to the membrane in cells cultured for six or 48 h. Similarly, insulin had no effect on immunoprecipitable PKCzeta. Suppression of the glycogenic insulin signal by phorbol 12-myristate 13-acetate, but not by ATP, could be completely alleviated by bisindolylmaleimide. Finally, insulin showed no effect on DAG mass or translocation of PKC isoforms in the perfused liver, although it reduced the glucagon-stimulated glucose output by 75%. Together these results indicate that phospholipases C and D or multiple PKC isoforms are not involved in the hepatic insulin signal chain.
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Affiliation(s)
- Irmelin Probst
- Institut für Biochemie und Molekulare Zellbiologie, Georg-August - Universität Göttingen, Germany.
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Shigematsu S, Watson RT, Khan AH, Pessin JE. The adipocyte plasma membrane caveolin functional/structural organization is necessary for the efficient endocytosis of GLUT4. J Biol Chem 2003; 278:10683-90. [PMID: 12496259 DOI: 10.1074/jbc.m208563200] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It is well established that insulin stimulation of glucose uptake requires the translocation of intracellular localized GLUT4 protein to the cell surface membrane. This plasma membrane-redistributed GLUT4 protein was partially co-localized with caveolin as determined by confocal fluorescent microscopy but was fully excluded from lipid rafts based upon Triton X-100 extractability. Cholesterol depletion with methyl-beta-cyclodextrin, filipin, or cholesterol oxidase resulted in an insulin-independent increase in the amount of plasma membrane-localized GLUT4 that was fully reversible by cholesterol replenishment. This basal accumulation of cell surface GLUT4 occurred due to an inhibition of GLUT4 endocytosis. However, this effect was not specific since cholesterol extraction also resulted in a dramatic inhibition of clathrin-mediated endocytosis as assessed by transferrin receptor internalization. To functionally distinguish between caveolin- and clathrin-dependent endocytic processes, we took advantage of a dominant-interfering caveolin 1 mutant (Cav1/S80E) that specifically disrupts caveolae organization. Expression of Cav1/S80E, but not the wild type (Cav1/WT) or Cav1/S80A mutant, inhibited cholera toxin B internalization without any significant effect on transferrin receptor endocytosis. In parallel, Cav1/S80E expression increased the amount of plasma membrane-localized GLUT4 protein in an insulin-independent manner. Although Cav1/S80E also decreased GLUT4 endocytosis, the extent of GLUT4 internalization was only partially reduced ( approximately 40%). In addition, expression of Cav1/WT and Cav1/S80A enhanced GLUT4 endocytosis by approximately 20%. Together, these data indicate that the endocytosis of GLUT4 requires clathrin-mediated endocytosis but that the higher order structural organization of plasma membrane caveolin has a significant influence on this process.
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Affiliation(s)
- Satoshi Shigematsu
- Department of Physiology and Biophysics, The University of Iowa, Iowa City 52242, USA
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Kayali AG, Austin DA, Webster NJG. Rottlerin inhibits insulin-stimulated glucose transport in 3T3-L1 adipocytes by uncoupling mitochondrial oxidative phosphorylation. Endocrinology 2002; 143:3884-96. [PMID: 12239100 DOI: 10.1210/en.2002-220259] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
There is increasing evidence that protein kinase C (PKC) isoforms modulate insulin-signaling pathways in both positive and negative ways. Recent reports have indicated that the novel PKCdelta mediates some of insulin's actions in muscle and liver cells. Many studies use the specific inhibitor rottlerin to demonstrate the involvement of PKCdelta. In this study, we investigated whether PKCdelta might play a role in 3T3-L1 adipocytes. We found that PKCdelta is highly expressed in mouse adipose tissue and increased on 3T3-L1 adipocyte differentiation, and insulin-stimulated glucose transport is blocked by rottlerin. The phosphorylation state and activity of PKCdelta are not altered by insulin, but the protein translocates to membranes following insulin treatment. In contrast to the results with rottlerin, inhibition of PKCdelta activity or expression has no effect on glucose transport in adipocytes, unlike muscle cells. Lastly, we found that rottlerin lowers adenosine triphosphate levels in 3T3-L1 cells by acting as a mitochondrial uncoupler, and this is responsible for the observed inhibition of glucose transport.
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Affiliation(s)
- Ayse G Kayali
- Medical Research Service, San Diego Veterans Affairs Healthcare System, California 92161, USA
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Caruso M, Maitan MA, Bifulco G, Miele C, Vigliotta G, Oriente F, Formisano P, Beguinot F. Activation and mitochondrial translocation of protein kinase Cdelta are necessary for insulin stimulation of pyruvate dehydrogenase complex activity in muscle and liver cells. J Biol Chem 2001; 276:45088-97. [PMID: 11577086 DOI: 10.1074/jbc.m105451200] [Citation(s) in RCA: 74] [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
In L6 skeletal muscle cells and immortalized hepatocytes, insulin induced a 2-fold increase in the activity of the pyruvate dehydrogenase (PDH) complex. This effect was almost completely blocked by the protein kinase C (PKC) delta inhibitor Rottlerin and by PKCdelta antisense oligonucleotides. At variance, overexpression of wild-type PKCdelta or of an active PKCdelta mutant induced PDH complex activity in both L6 and liver cells. Insulin stimulation of the activity of the PDH complex was accompanied by a 2.5-fold increase in PDH phosphatases 1 and 2 (PDP1/2) activity with no change in the activity of PDH kinase. PKCdelta antisense blocked insulin activation of PDP1/2, the same as with PDH. In insulin-exposed cells, PDP1/2 activation was paralleled by activation and mitochondrial translocation of PKCdelta, as revealed by cell subfractionation and confocal microscopy studies. The mitochondrial translocation of PKCdelta, like its activation, was prevented by Rottlerin. In extracts from insulin-stimulated cells, PKCdelta co-precipitated with PDP1/2. PKCdelta also bound to PDP1/2 in overlay blots, suggesting that direct PKCdelta-PDP interaction may occur in vivo as well. In intact cells, insulin exposure determined PDP1/2 phosphorylation, which was specifically prevented by PKCdelta antisense. PKCdelta also phosphorylated PDP in vitro, followed by PDP1/2 activation. Thus, in muscle and liver cells, insulin causes activation and mitochondrial translocation of PKCdelta, accompanied by PDP phosphorylation and activation. These events are necessary for insulin activation of the PDH complex in these cells.
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Affiliation(s)
- M Caruso
- Dipartimento di Biologia e Patologia Cellulare e Molecolare and Centro di Endocrinologia ed Oncologia Sperimentale del CNR, Federico II University of Naples, 80131 Naples, Italy
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