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Sajan MP, Hansen BC, Acevedo‐Duncan M, Kindy MS, Cooper DR, Farese RV. Roles of hepatic atypical protein kinase C hyperactivity and hyperinsulinemia in insulin-resistant forms of obesity and type 2 diabetes mellitus. MedComm (Beijing) 2021; 2:3-16. [PMID: 34766133 PMCID: PMC8491214 DOI: 10.1002/mco2.54] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 12/21/2020] [Accepted: 12/28/2020] [Indexed: 11/10/2022] Open
Abstract
Diet-induced obesity, the metabolic syndrome, type 2 diabetes (DIO/MetS/T2DM), and their adverse sequelae have reached pandemic levels. In mice, DIO/MetS/T2DM initiation involves diet-dependent increases in lipids that activate hepatic atypical PKC (aPKC) and thereby increase lipogenic enzymes and proinflammatory cytokines. These or other hepatic aberrations, via adverse liver-to-muscle cross talk, rapidly impair postreceptor insulin signaling to glucose transport in muscle. The ensuing hyperinsulinemia further activates hepatic aPKC, which first blocks the ability of Akt to suppress gluconeogenic enzyme expression, and later impairs Akt activation, further increasing hepatic glucose production. Recent findings suggest that hepatic aPKC also increases a proteolytic enzyme that degrades insulin receptors. Fortunately, all hepatic aberrations and muscle impairments are prevented/reversed by inhibition or deficiency of hepatic aPKC. But, in the absence of treatment, hyperinsulinemia induces adverse events, some by using "spare receptors" to bypass receptor defects. Thus, in brain, hyperinsulinemia increases Aβ-plaque precursors and Alzheimer risk; in kidney, hyperinsulinemia activates the renin-angiotensin-adrenal axis, thus increasing vasoconstriction, sodium retention, and cardiovascular risk; and in liver, hyperinsulinemia increases lipogenesis, obesity, hepatosteatosis, hyperlipidemia, and cardiovascular risk. In summary, increases in hepatic aPKC are critically required for development of DIO/MetS/T2DM and its adverse sequelae, and therapeutic approaches that limit hepatic aPKC may be particularly effective.
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Affiliation(s)
- Mini P. Sajan
- Department of Internal MedicineUniversity of South Florida College of MedicineTampaFloridaUSA
- Research ServiceJames AHaley Veterans Administration Medical CenterTampaFloridaUSA
| | - Barbara C. Hansen
- Department of Internal MedicineUniversity of South Florida College of MedicineTampaFloridaUSA
| | - Mildred Acevedo‐Duncan
- Department of ChemistryCollege of Arts and SciencesUniversity of South FloridaTampaFloridaUSA
| | - Mark S. Kindy
- Research ServiceJames AHaley Veterans Administration Medical CenterTampaFloridaUSA
- Department of Pharmaceutical SciencesCollege of PharmacyUniversity of South FloridaTampaFloridaUSA
| | - Denise R. Cooper
- Research ServiceJames AHaley Veterans Administration Medical CenterTampaFloridaUSA
- Department of Molecular MedicineUniversity of South FloridaTampaFloridaUSA
| | - Robert V. Farese
- Department of Internal MedicineUniversity of South Florida College of MedicineTampaFloridaUSA
- Research ServiceJames AHaley Veterans Administration Medical CenterTampaFloridaUSA
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Velnati S, Centonze S, Girivetto F, Capello D, Biondi RM, Bertoni A, Cantello R, Ragnoli B, Malerba M, Graziani A, Baldanzi G. Identification of Key Phospholipids That Bind and Activate Atypical PKCs. Biomedicines 2021; 9:biomedicines9010045. [PMID: 33419210 PMCID: PMC7825596 DOI: 10.3390/biomedicines9010045] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 12/30/2020] [Accepted: 01/01/2021] [Indexed: 12/02/2022] Open
Abstract
PKCζ and PKCι/λ form the atypical protein kinase C subgroup, characterised by a lack of regulation by calcium and the neutral lipid diacylglycerol. To better understand the regulation of these kinases, we systematically explored their interactions with various purified phospholipids using the lipid overlay assays, followed by kinase activity assays to evaluate the lipid effects on their enzymatic activity. We observed that both PKCζ and PKCι interact with phosphatidic acid and phosphatidylserine. Conversely, PKCι is unique in binding also to phosphatidylinositol-monophosphates (e.g., phosphatidylinositol 3-phosphate, 4-phosphate, and 5-phosphate). Moreover, we observed that phosphatidylinositol 4-phosphate specifically activates PKCι, while both isoforms are responsive to phosphatidic acid and phosphatidylserine. Overall, our results suggest that atypical Protein kinase C (PKC) localisation and activity are regulated by membrane lipids distinct from those involved in conventional PKCs and unveil a specific regulation of PKCι by phosphatidylinositol-monophosphates.
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Affiliation(s)
- Suresh Velnati
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- Center for Translational Research on Allergic and Autoimmune Diseases (CAAD), University of Piemonte Orientale, 28100 Novara, Italy
- Correspondence:
| | - Sara Centonze
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- Center for Translational Research on Allergic and Autoimmune Diseases (CAAD), University of Piemonte Orientale, 28100 Novara, Italy
| | - Federico Girivetto
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- Center for Translational Research on Allergic and Autoimmune Diseases (CAAD), University of Piemonte Orientale, 28100 Novara, Italy
| | - Daniela Capello
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- UPO Biobank, University of Piemonte Orientale, 28100 Novara, Italy
| | - Ricardo M. Biondi
- Department of Internal Medicine 1, Goethe University Hospital Frankfurt, 60590 Frankfurt, Germany;
- Biomedicine Research Institute of Buenos Aires—CONICET—Partner Institute of the Max Planck Society, Buenos Aires C1425FQD, Argentina
| | - Alessandra Bertoni
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
| | - Roberto Cantello
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
| | | | - Mario Malerba
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- Respiratory Unit, Sant’Andrea Hospital, 13100 Vercelli, Italy;
| | - Andrea Graziani
- Molecular Biotechnology Center, Department of Molecular Biotechnology and Health Sciences, University of Torino, 10126 Turin, Italy;
- Division of Oncology, Università Vita-Salute San Raffaele, 20132 Milan, Italy
| | - Gianluca Baldanzi
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- Center for Translational Research on Allergic and Autoimmune Diseases (CAAD), University of Piemonte Orientale, 28100 Novara, Italy
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Bruntz RC, Lindsley CW, Brown HA. Phospholipase D signaling pathways and phosphatidic acid as therapeutic targets in cancer. Pharmacol Rev 2015; 66:1033-79. [PMID: 25244928 DOI: 10.1124/pr.114.009217] [Citation(s) in RCA: 165] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Phospholipase D is a ubiquitous class of enzymes that generates phosphatidic acid as an intracellular signaling species. The phospholipase D superfamily plays a central role in a variety of functions in prokaryotes, viruses, yeast, fungi, plants, and eukaryotic species. In mammalian cells, the pathways modulating catalytic activity involve a variety of cellular signaling components, including G protein-coupled receptors, receptor tyrosine kinases, polyphosphatidylinositol lipids, Ras/Rho/ADP-ribosylation factor GTPases, and conventional isoforms of protein kinase C, among others. Recent findings have shown that phosphatidic acid generated by phospholipase D plays roles in numerous essential cellular functions, such as vesicular trafficking, exocytosis, autophagy, regulation of cellular metabolism, and tumorigenesis. Many of these cellular events are modulated by the actions of phosphatidic acid, and identification of two targets (mammalian target of rapamycin and Akt kinase) has especially highlighted a role for phospholipase D in the regulation of cellular metabolism. Phospholipase D is a regulator of intercellular signaling and metabolic pathways, particularly in cells that are under stress conditions. This review provides a comprehensive overview of the regulation of phospholipase D activity and its modulation of cellular signaling pathways and functions.
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Affiliation(s)
- Ronald C Bruntz
- Department of Pharmacology (R.C.B., C.W.L., H.A.B.) and Vanderbilt Center for Neuroscience Drug Discovery (C.W.L.), Vanderbilt University Medical Center; Department of Chemistry, Vanderbilt Institute of Chemical Biology (C.W.L., H.A.B.); Vanderbilt Specialized Chemistry for Accelerated Probe Development (C.W.L.); and Department of Biochemistry, Vanderbilt-Ingram Cancer Center (H.A.B.), Vanderbilt University, Nashville, Tennessee
| | - Craig W Lindsley
- Department of Pharmacology (R.C.B., C.W.L., H.A.B.) and Vanderbilt Center for Neuroscience Drug Discovery (C.W.L.), Vanderbilt University Medical Center; Department of Chemistry, Vanderbilt Institute of Chemical Biology (C.W.L., H.A.B.); Vanderbilt Specialized Chemistry for Accelerated Probe Development (C.W.L.); and Department of Biochemistry, Vanderbilt-Ingram Cancer Center (H.A.B.), Vanderbilt University, Nashville, Tennessee
| | - H Alex Brown
- Department of Pharmacology (R.C.B., C.W.L., H.A.B.) and Vanderbilt Center for Neuroscience Drug Discovery (C.W.L.), Vanderbilt University Medical Center; Department of Chemistry, Vanderbilt Institute of Chemical Biology (C.W.L., H.A.B.); Vanderbilt Specialized Chemistry for Accelerated Probe Development (C.W.L.); and Department of Biochemistry, Vanderbilt-Ingram Cancer Center (H.A.B.), Vanderbilt University, Nashville, Tennessee
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Farlinger CM, Lui AJ, Harrison RC, LeBlanc PJ, Peters SJ, Roy BD. Extracellular hyperosmotic stress stimulates glucose uptake in incubated fast-twitch rat skeletal muscle. Appl Physiol Nutr Metab 2013; 38:605-12. [DOI: 10.1139/apnm-2012-0236] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The influence of hyperosmotic stress on glucose uptake, handling, and signaling processes remains unclear in mammalian skeletal muscle. Thus, the purpose of this study was to investigate alterations in glucose uptake and handling during extracellular hyperosmotic stress in isolated fast-twitch mammalian skeletal muscle. Using an established in vitro isolated whole-muscle model, extensor digitorum longus (EDL) muscles were dissected from male rats (4–6 weeks of age) and incubated (30–60 min) in an organ bath, containing Sigma Medium-199 with 8 mmol·L−1D-glucose, and mannitol was added to the targeted osmolalities (ISO, iso-osmotic, 290 mmol·kg−1; HYPER, hyperosmotic, 400 mmol·kg−1). Results demonstrate that relative water content decreased in HYPER. HYPER resulted in significant alterations in muscle metabolite concentrations (lower glycogen, elevated lactate, and glucose-6-phosphate), suggesting a decrease in energy charge. Glucose uptake was also found to be higher in HYPER, and AS160 (implicated in insulin- and contraction-mediated glucose uptake) was found to be significantly more phosphorylated in HYPER than in ISO after 30 min. In conclusion, glucose uptake and handling is altered with hyperosmotic extracellular stress in the fast-twitch EDL. The increases in glucose uptake might be facilitated through alterations in AS160 signaling after 30 to 60 min of osmotic stress.
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Affiliation(s)
- Chris M. Farlinger
- Faculty of Applied Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Adrian J. Lui
- Faculty of Applied Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Rose C. Harrison
- Faculty of Applied Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Paul J. LeBlanc
- Faculty of Applied Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada; Centre for Bone and Muscle Health, Brock University, St. Catharines, ON L2S 3A1, Canada; Department of Community Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Sandra J. Peters
- Faculty of Applied Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada; Centre for Bone and Muscle Health, Brock University, St. Catharines, ON L2S 3A1, Canada; Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Brian D. Roy
- Faculty of Applied Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada; Centre for Bone and Muscle Health, Brock University, St. Catharines, ON L2S 3A1, Canada; Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
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Prasad J, Maurya CK, Pandey J, Jaiswal N, Madhur G, Srivastava AK, Narender T, Tamrakar AK. Diastereomeric mixture of calophyllic acid and isocalophyllic acid stimulates glucose uptake in skeletal muscle cells: involvement of PI-3-kinase- and ERK1/2-dependent pathways. Mol Cell Endocrinol 2013; 370:11-9. [PMID: 23428406 DOI: 10.1016/j.mce.2013.02.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 01/23/2013] [Accepted: 02/13/2013] [Indexed: 12/19/2022]
Abstract
The diastereomeric mixture of calophyllic acid and isocalophyllic acid (F015) isolated from the leaves of Calophyllum inophyllum was investigated for the metabolic effect on glucose transport in skeletal muscle cells. In L6 myotubes, F015 dose-dependently stimulated glucose uptake by increasing translocation of glucose transporter4 (GLUT4) to plasma membrane without affecting their gene expression. The effects on glucose uptake were additive to insulin. Inhibitors analyses revealed that F015-induced glucose uptake was dependent on the activation of phosphatidylinositol-3-kinase (PI-3-K) and extracellular signal-regulated kinases 1 and 2 (ERK1/2), while independent to the activation of 5'AMP-activated kinase (AMPK). F015 significantly increased the phosphorylation of AKT, AS160 and ERK1/2, account for the augmented glucose transport capacity in L6 myotubes. Furthermore, F015 improved glucose tolerance and enhanced insulin sensitivity in skeletal muscle of dexamethasone-induced insulin resistant mice. Our findings demonstrate that F015 activates glucose uptake in skeletal muscle cells through PI-3-K- and EKR1/2-dependent mechanisms and can be a potential lead for the management of diabetes and obesity.
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Affiliation(s)
- Janki Prasad
- Division of Medicinal and Process Chemistry, CSIR - Central Drug Research Institute, Lucknow 226 001, India
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Nosarzewski M, Downie AB, Wu B, Archbold DD. The role of SORBITOL DEHYDROGENASE in Arabidopsis thaliana. FUNCTIONAL PLANT BIOLOGY : FPB 2012; 39:462-470. [PMID: 32480797 DOI: 10.1071/fp12008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 04/04/2012] [Indexed: 06/11/2023]
Abstract
SORBITOL DEHYDROGENASE (SDH, EC 1.1.1.14) catalyses the interconversion of polyols and ketoses (e.g. sorbitol ⟷ fructose). Using two independent Arabidopsis thaliana (L.) Heynh. sdh knockout mutants, we show that SDH (At5g51970) plays a primary role in sorbitol metabolism as well as an unexpected role in ribitol metabolism. Sorbitol content increased in both wild-type (WT) and mutant plant leaves during drought stress, but mutants showed a dramatically different phenotype, dying even if rewatered. The lack of functional SDH in mutant plants was accompanied by accumulation of foliar sorbitol and at least 10-fold more ribitol, neither of which decreased in mutant plants after rewatering. In addition, mutant plants were uniquely sensitive to ribitol in a concentration-dependent manner, which either prevented them from completing seed germination or inhibited seedling development, effects not observed with other polyols or with ribitol-treated WT plants. Ribitol catabolism may occur solely through SDH in A. thaliana, though at only 30% the rate of that for sorbitol. The results indicate a role for SDH in metabolism of sorbitol to fructose and in ribitol conversion to ribulose in A. thaliana during recovery from drought stress.
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Affiliation(s)
- Marta Nosarzewski
- University of Kentucky, Department of Horticulture, N318 Agricultural Science Center North, Lexington, KY 40546, USA
| | - A Bruce Downie
- University of Kentucky, Department of Horticulture, N318 Agricultural Science Center North, Lexington, KY 40546, USA
| | - Benhong Wu
- University of Kentucky, Department of Horticulture, N318 Agricultural Science Center North, Lexington, KY 40546, USA
| | - Douglas D Archbold
- University of Kentucky, Department of Horticulture, N318 Agricultural Science Center North, Lexington, KY 40546, USA
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7
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Phospholipase D1 mediates AMP-activated protein kinase signaling for glucose uptake. PLoS One 2010; 5:e9600. [PMID: 20231899 PMCID: PMC2834755 DOI: 10.1371/journal.pone.0009600] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Accepted: 02/16/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Glucose homeostasis is maintained by a balance between hepatic glucose production and peripheral glucose utilization. In skeletal muscle cells, glucose utilization is primarily regulated by glucose uptake. Deprivation of cellular energy induces the activation of regulatory proteins and thus glucose uptake. AMP-activated protein kinase (AMPK) is known to play a significant role in the regulation of energy balances. However, the mechanisms related to the AMPK-mediated control of glucose uptake have yet to be elucidated. METHODOLOGY/PRINCIPAL FINDINGS Here, we found that AMPK-induced phospholipase D1 (PLD1) activation is required for (14)C-glucose uptake in muscle cells under glucose deprivation conditions. PLD1 activity rather than PLD2 activity is significantly enhanced by glucose deprivation. AMPK-wild type (WT) stimulates PLD activity, while AMPK-dominant negative (DN) inhibits it. AMPK regulates PLD1 activity through phosphorylation of the Ser-505 and this phosphorylation is increased by the presence of AMP. Furthermore, PLD1-S505Q, a phosphorylation-deficient mutant, shows no changes in activity in response to glucose deprivation and does not show a significant increase in (14)C-glucose uptake when compared to PLD1-WT. Taken together, these results suggest that phosphorylation of PLD1 is important for the regulation of (14)C-glucose uptake. In addition, extracellular signal-regulated kinase (ERK) is stimulated by AMPK-induced PLD1 activation through the formation of phosphatidic acid (PA), which is a product of PLD. An ERK pharmacological inhibitor, PD98059, and the PLD inhibitor, 1-BtOH, both attenuate (14)C-glucose uptake in muscle cells. Finally, the extracellular stresses caused by glucose deprivation or aminoimidazole carboxamide ribonucleotide (AICAR; AMPK activator) regulate (14)C-glucose uptake and cell surface glucose transport (GLUT) 4 through ERK stimulation by AMPK-mediated PLD1 activation. CONCLUSIONS/SIGNIFICANCE These results suggest that AMPK-mediated PLD1 activation is required for (14)C-glucose uptake through ERK stimulation. We propose that the AMPK-mediated PLD1 pathway may provide crucial clues to understanding the mechanisms involved in glucose uptake.
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Sajan MP, Bandyopadhyay G, Miura A, Standaert ML, Nimal S, Longnus SL, Van Obberghen E, Hainault I, Foufelle F, Kahn R, Braun U, Leitges M, Farese RV. AICAR and metformin, but not exercise, increase muscle glucose transport through AMPK-, ERK-, and PDK1-dependent activation of atypical PKC. Am J Physiol Endocrinol Metab 2010; 298:E179-92. [PMID: 19887597 PMCID: PMC2822478 DOI: 10.1152/ajpendo.00392.2009] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Activators of 5'-AMP-activated protein kinase (AMPK) 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR), metformin, and exercise activate atypical protein kinase C (aPKC) and ERK and stimulate glucose transport in muscle by uncertain mechanisms. Here, in cultured L6 myotubes: AICAR- and metformin-induced activation of AMPK was required for activation of aPKC and ERK; aPKC activation involved and required phosphoinositide-dependent kinase 1 (PDK1) phosphorylation of Thr410-PKC-zeta; aPKC Thr410 phosphorylation and activation also required MEK1-dependent ERK; and glucose transport effects of AICAR and metformin were inhibited by expression of dominant-negative AMPK, kinase-inactive PDK1, MEK1 inhibitors, kinase-inactive PKC-zeta, and RNA interference (RNAi)-mediated knockdown of PKC-zeta. In mice, muscle-specific aPKC (PKC-lambda) depletion by conditional gene targeting impaired AICAR-stimulated glucose disposal and stimulatory effects of both AICAR and metformin on 2-deoxyglucose/glucose uptake in muscle in vivo and AICAR stimulation of 2-[(3)H]deoxyglucose uptake in isolated extensor digitorum longus muscle; however, AMPK activation was unimpaired. In marked contrast to AICAR and metformin, treadmill exercise-induced stimulation of 2-deoxyglucose/glucose uptake was not inhibited in aPKC-knockout mice. Finally, in intact rodents, AICAR and metformin activated aPKC in muscle, but not in liver, despite activating AMPK in both tissues. The findings demonstrate that in muscle AICAR and metformin activate aPKC via sequential activation of AMPK, ERK, and PDK1 and the AMPK/ERK/PDK1/aPKC pathway is required for metformin- and AICAR-stimulated increases in glucose transport. On the other hand, although aPKC is activated by treadmill exercise, this activation is not required for exercise-induced increases in glucose transport, and therefore may be a redundant mechanism.
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Affiliation(s)
- M. P. Sajan
- 1Research Service, James A. Haley Veterans Hospital and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, Florida;
| | - G. Bandyopadhyay
- 1Research Service, James A. Haley Veterans Hospital and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, Florida;
| | - A. Miura
- 1Research Service, James A. Haley Veterans Hospital and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, Florida;
| | - M. L. Standaert
- 1Research Service, James A. Haley Veterans Hospital and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, Florida;
| | - S. Nimal
- 6Roskamp Institute, Sarasota, Florida
| | - S. L. Longnus
- 2Institut National de la Santé et de la Recherche Médicale (INSERM) U145, Institut Federatif de Recherche 50, Faculte de Medicine, Nice and
| | - E. Van Obberghen
- 2Institut National de la Santé et de la Recherche Médicale (INSERM) U145, Institut Federatif de Recherche 50, Faculte de Medicine, Nice and
| | - I. Hainault
- 3INSERM U671, Centre de Recherches Biomedicales des Cordeliers, Universite Pierre et Marie Curie, Paris, France;
| | - F. Foufelle
- 3INSERM U671, Centre de Recherches Biomedicales des Cordeliers, Universite Pierre et Marie Curie, Paris, France;
| | - R. Kahn
- 4Joslin Center and Harvard Medical School, Boston, Massachusetts;
| | - U. Braun
- 5Biotechnology Centre of Oslo, Oslo, Norway; and
| | - M. Leitges
- 5Biotechnology Centre of Oslo, Oslo, Norway; and
| | - R. V. Farese
- 1Research Service, James A. Haley Veterans Hospital and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, Florida;
- 6Roskamp Institute, Sarasota, Florida
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Cheung R, Malik M, Ravyn V, Tomkowicz B, Ptasznik A, Collman RG. An arrestin-dependent multi-kinase signaling complex mediates MIP-1beta/CCL4 signaling and chemotaxis of primary human macrophages. J Leukoc Biol 2009; 86:833-45. [PMID: 19620252 DOI: 10.1189/jlb.0908551] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
MIP-1beta/CCL4 is a principal regulator of macrophage migration and signals through CCR5. Several protein kinases are linked to CCR5 in macrophages including the src kinase Lyn, PI3K, focal adhesion related kinase Pyk2, and members of the MAPK family, but whether and how these kinases regulate macrophage chemotaxis are not known. To define the role of these signaling molecules, we examined the functions and interactions of endogenous proteins in primary human macrophages. Using siRNA gene silencing and pharmacologic inhibition, we show that chemotaxis in response to CCR5 stimulation by MIP-1beta requires activation of Pyk2, PI3K p85, and Lyn, as well as MAPK ERK. MIP-1beta activation of CCR5 triggered translocation of Pyk2 and PI3K p85 from the cytoplasm to colocalize with Lyn at the plasma membrane with formation of a multimolecular complex. We show further that arrestins were recruited into the complex, and arrestin down-regulation impaired complex formation and macrophage chemotaxis toward MIP-1beta. Together, these results identify a novel mechanism of chemokine receptor regulation of chemotaxis and suggest that arrestins may serve as scaffolding proteins linking CCR5 to multiple downstream signaling molecules in a biologically important primary human cell type.
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Affiliation(s)
- Ricky Cheung
- Pulmonary, Allergy and Critical Care, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6061, USA
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10
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Girón MD, Sevillano N, Vargas AM, Domínguez J, Guinovart JJ, Salto R. The glucose-lowering agent sodium tungstate increases the levels and translocation of GLUT4 in L6 myotubes through a mechanism associated with ERK1/2 and MEF2D. Diabetologia 2008; 51:1285-95. [PMID: 18483800 DOI: 10.1007/s00125-008-1003-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Accepted: 03/16/2008] [Indexed: 12/17/2022]
Abstract
AIMS/HYPOTHESIS The aim of this study was to investigate the action of the glucose-lowering compound sodium tungstate on glucose transport in muscle myotubes and to unravel the molecular events underlying the effects observed. METHODS We studied the effects of tungstate on 2-deoxy-D: -glucose uptake, levels and translocation of the glucose transporters GLUT4 and GLUT1, and Glut4 (also known as Slc2a4) promoter activity. We also measured the modifications of individual components of the signalling pathways involved in the effects observed. RESULTS Tungstate increased 2-deoxy-D: -glucose uptake in differentiated L6 myotubes through an increase in the total amount and translocation of GLUT4 transporter. The effects on glucose uptake were additive to those of insulin. Tungstate activated transcription of the Glut4 promoter, as shown by an increase in Glut4 mRNA, and by a promoter reporter assay. The assay of deletions of the Glut4 promoter indicated that the effect of tungstate is mediated by the myocyte enhancer factor 2 (MEF2)-binding domain. Accordingly, MEF2 levels and DNA binding activities were increased in response to the treatment. Tungstate-induced glucose uptake and GLUT4 transcriptional activation were dependent on the activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), while no changes were observed in the phosphorylation state of the beta subunit of the insulin receptor, in the phosphatidylinositol 3-kinase pathway or in the activation of 5'AMP-activated protein kinase. CONCLUSIONS/INTERPRETATION Tungstate activates glucose uptake in myotubes through a novel ERK1/2-dependent mechanism. This effect is exerted by an increase in the content and translocation of the GLUT4 transporter. This is the first report of a glucose-lowering compound activating Glut4 transcription through an ERK1/2-dependent increase in MEF2 levels.
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Affiliation(s)
- M D Girón
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, University of Granada, Campus de Cartuja sn, 18071, Granada, Spain
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11
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Cheung R, Ravyn V, Wang L, Ptasznik A, Collman RG. Signaling mechanism of HIV-1 gp120 and virion-induced IL-1beta release in primary human macrophages. THE JOURNAL OF IMMUNOLOGY 2008; 180:6675-84. [PMID: 18453587 DOI: 10.4049/jimmunol.180.10.6675] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
HIV-1 envelope glycoprotein gp120 induces, independently of infection, the release of proinflammatory cytokines, including IL-1beta from macrophages, that are implicated in the pathogenesis of HIV-associated dementia. However, the signal transduction pathways involved have not been fully defined. Previously, our laboratory reported that soluble gp120 activates multiple protein kinases in primary human monocyte-derived macrophages, including the Src family kinase Lyn, PI3K, and the focal adhesion-related proline-rich tyrosine kinase Pyk2. In this study we showed that gp120 induces IL-1beta release from macrophages in a time- and concentration-dependent manner through binding to the chemokine receptor CCR5 and coupling to G(i)alpha protein. Using pharmacological inhibitors and small interfering RNA gene knockdown, we demonstrated that concomitant activation of Lyn, Pyk2, and class IA PI3K are required for gp120-induced IL-1beta production. By coimmunoprecipitation and immunofluorescence confocal microscopy, we showed that CCR5 activation by gp120 triggered the assembly of a signaling complex involving endogenous Lyn, PI3K, and Pyk2 and is associated with PI3K and Pyk2 translocation from the cytoplasm to the membrane where they colocalized with Lyn. Finally, we demonstrated that virion-associated gp120 induced similar response, as structurally intact whole virions also triggered IL-1beta release and re-localization of PI3K and Pyk2. This study identifies a novel signaling mechanism for HIV-1-induced IL-1beta production by primary human macrophages that may be involved in the neuropathogenesis of HIV-associated dementia.
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Affiliation(s)
- Ricky Cheung
- Pulmonary, Allergy, and Critical Care, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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12
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Heyward CA, Pettitt TR, Leney SE, Welsh GI, Tavaré JM, Wakelam MJO. An intracellular motif of GLUT4 regulates fusion of GLUT4-containing vesicles. BMC Cell Biol 2008; 9:25. [PMID: 18492238 PMCID: PMC2405794 DOI: 10.1186/1471-2121-9-25] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Accepted: 05/20/2008] [Indexed: 01/17/2023] Open
Abstract
Background Insulin stimulates glucose uptake by adipocytes through increasing translocation of the glucose transporter GLUT4 from an intracellular compartment to the plasma membrane. Fusion of GLUT4-containing vesicles at the cell surface is thought to involve phospholipase D activity, generating the signalling lipid phosphatidic acid, although the mechanism of action is not yet clear. Results Here we report the identification of a putative phosphatidic acid-binding motif in a GLUT4 intracellular loop. Mutation of this motif causes a decrease in the insulin-induced exposure of GLUT4 at the cell surface of 3T3-L1 adipocytes via an effect on vesicle fusion. Conclusion The potential phosphatidic acid-binding motif identified in this study is unique to GLUT4 among the sugar transporters, therefore this motif may provide a unique mechanism for regulating insulin-induced translocation by phospholipase D signalling.
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Affiliation(s)
- Catherine A Heyward
- CR-UK Institute for Cancer Studies, Birmingham University, Birmingham B15 2TT, UK.
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Williams D, Pessin JE. Mapping of R-SNARE function at distinct intracellular GLUT4 trafficking steps in adipocytes. ACTA ACUST UNITED AC 2008; 180:375-87. [PMID: 18227281 PMCID: PMC2213575 DOI: 10.1083/jcb.200709108] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The functional trafficking steps used by soluble NSF attachment protein receptor (SNARE) proteins have been difficult to establish because of substantial overlap in subcellular localization and because in vitro SNARE-dependent binding and fusion reactions can be promiscuous. Therefore, to functionally identify the site of action of the vesicle-associated membrane protein (VAMP) family of R-SNAREs, we have taken advantage of the temporal requirements of adipocyte biosynthetic sorting of a dual-tagged GLUT4 reporter (myc-GLUT4-GFP) coupled with small interfering RNA gene silencing. Using this approach, we confirm the requirement of VAMP2 and VAMP7 for insulin and osmotic shock trafficking from the vesicle storage sites, respectively, and fusion with the plasma membrane. Moreover, we identify a requirement for VAMP4 for the initial biosynthetic entry of GLUT4 from the Golgi apparatus into the insulin-responsive vesicle compartment, VAMP8, for plasma membrane endocytosis and VAMP2 for sorting to the specialized insulin-responsive compartment after plasma membrane endocytosis.
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Affiliation(s)
- Dumaine Williams
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
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Huang P, Jiang Z, Teng S, Wong YC, Frohman MA, Chung SK, Chung SSM. Synergism between phospholipase D2 and sorbitol accumulation in diabetic cataract formation through modulation of Na,K-ATPase activity and osmotic stress. Exp Eye Res 2006; 83:939-48. [PMID: 16797533 DOI: 10.1016/j.exer.2006.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2005] [Revised: 05/05/2006] [Accepted: 05/08/2006] [Indexed: 10/24/2022]
Abstract
Phospholipase D (PLD), a highly regulated enzyme that generates the second messenger phosphatidic acid, functions in signal transduction, membrane trafficking and cytoskeletal reorganization. PLD is thought to be involved in the pathogenesis of diabetic complications by activating PKC. Since PKC and PLD are present in the lens we sought to determine if PLD plays a role in diabetic cataract development. We developed transgenic mice that overexpress PLD2, one of the two mammalian isoforms of PLD. These mice developed congenital nuclear cataracts, but not diabetic cataracts. Histological analysis revealed vacuole formation in the fiber cells, mediated potentially by the substantially increased Na,K-ATPase activity. In the presence of the aldose reductase overexpressing transgene that increases lens osmotic pressure, these double transgenic mice developed more severe congenital cataract and became susceptible to develop diabetic cataract. Together, these data suggest that increased PLD2 activity in the lens under hyperglycemic condition might impair its osmoregulatory mechanism and reduce its ability to cope with the osmotic stress triggered by sorbitol accumulation.
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Affiliation(s)
- Ping Huang
- Institute of Molecular Biology, University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong, China
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15
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Brady SC, Allan LA, Clarke PR. Regulation of caspase 9 through phosphorylation by protein kinase C zeta in response to hyperosmotic stress. Mol Cell Biol 2005; 25:10543-55. [PMID: 16287866 PMCID: PMC1291226 DOI: 10.1128/mcb.25.23.10543-10555.2005] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Caspase 9 is a critical component of the mitochondrial or intrinsic apoptotic pathway and is activated by Apaf-1 following release of cytochrome c from mitochondria in response to a variety of stimuli. Caspase 9 cleaves and activates effector caspases, mainly caspase 3, leading to the demise of the cell. Survival signaling pathways can impinge on this pathway to restrain apoptosis. Here, we have identified Ser144 of human caspase 9as an inhibitory site that is phosphorylated in a cell-free system and in cells in response to the protein phosphatase inhibitor okadaic acid. Inhibitor sensitivity and interactions with caspase 9 indicate that the predominant kinase that targets Ser144 is the atypical protein kinase C isoform zeta (PKCzeta). Prevention of Ser144 phosphorylation by inhibition of PKCzeta or mutation of caspase 9 promotes caspase 3 activation. Phosphorylation of serine 144 in cells is also induced by hyperosmotic stress, which activates PKCzeta and regulates its interaction with caspase 9, but not by growth factors, phorbol ester, or other cellular stresses. These results indicate that phosphorylation and inhibition of caspase 9 by PKCzeta restrain the intrinsic apoptotic pathway during hyperosmotic stress. This work provides further evidence that caspase 9 acts as a focal point for multiple protein kinase signaling pathways that regulate apoptosis.
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Affiliation(s)
- Suzanne C Brady
- Biomedical Research Centre, Level 5, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
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Hodgkinson C, Mander A, Sale G. Identification of 80K-H as a protein involved in GLUT4 vesicle trafficking. Biochem J 2005; 388:785-93. [PMID: 15707389 PMCID: PMC1183457 DOI: 10.1042/bj20041845] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PKCzeta (protein kinase Czeta) is a serine/threonine protein kinase controlled by insulin, various growth factors and phosphoinositide 3-kinase. It has been implicated in controlling glucose transport in response to insulin by the translocation of GLUT4-(glucose transporter 4) containing vesicles to the plasma membrane in stimulated cells. How PKCzeta modulates GLUT4 vesicle trafficking remains unknown. A yeast two-hybrid screen using full-length human PKCzeta identified 80K-H protein as an interactor with PKCzeta. GST (glutathione S-transferase) pull-down assays with GST-tagged 80K-H constructs confirmed the interaction and showed that the N-terminal portion of 80K-H was not required for the interaction. Immunoprecipitates of endogenous PKCzeta from Cho cells, 3T3-L1 adipocytes or L6 myotubes contained endogenous 80K-H, demonstrating a physiological interaction. Insulin stimulation enhanced the association 3-5-fold. Immunoprecipitates of endogenous 80K-H contained endogenous munc18c and immunoprecipitates of endogenous munc18c contained endogenous PKCzeta, with insulin markedly increasing the amount of co-immunoprecipitated protein in each case. These results show that insulin triggers interactions in vivo between PKCzeta, 80K-H and munc18c. Overexpression of 80K-H constructs mimicked the action of insulin in stimulating both glucose uptake and translocation of Myc-tagged GLUT4 in Cho cells, with the level of effect proportional to the ability of the constructs to associate with munc18c. These results identify 80K-H as a new player involved in GLUT4 vesicle transport and identify a link between a kinase involved in the insulin signalling cascade, PKCzeta, and a known component of the GLUT4 vesicle trafficking pathway, munc18c. The results suggest a model whereby insulin triggers the formation of a PKCzeta-80K-H-munc18c complex that enhances GLUT4 translocation to the plasma membrane.
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Affiliation(s)
- Conrad P. Hodgkinson
- School of Biological Sciences, Biomedical Sciences Building, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, U.K
| | - Ann Mander
- School of Biological Sciences, Biomedical Sciences Building, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, U.K
| | - Graham J. Sale
- School of Biological Sciences, Biomedical Sciences Building, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, U.K
- To whom correspondence should be addressed (email )
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Rose AJ, Michell BJ, Kemp BE, Hargreaves M. Effect of exercise on protein kinase C activity and localization in human skeletal muscle. J Physiol 2004; 561:861-70. [PMID: 15604232 PMCID: PMC1665391 DOI: 10.1113/jphysiol.2004.075549] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
To investigate the effect of exercise on protein kinase C (PKC) activity and localization in human skeletal muscle, eight healthy men performed cycle ergometer exercise for 40 min at 76 +/- 1% the peak pulmonary O(2) uptake , with muscle samples obtained at rest and after 5 and 40 min of exercise. PKC expression, phosphorylation and activities were examined by immunoblotting and in vitro kinase assays of fractionated and whole tissue preparations. In response to exercise, total PKC activity was slightly higher at 40 min in an enriched membrane fraction, and using a pSer-PKC-substrate motif antibody it was revealed that exercise increased the serine phosphorylation of an approximately 50 kDa protein. There were no changes in conventional PKC (cPKC) or PKC activities; however, atypical PKC (aPKC) activity was approximately 70% higher at 5 and 40 min, and aPKC expression and Thr(410/403) phosphorylation were unaltered by exercise. There were no effects of exercise on the abundance of PKCalpha, PKCdelta, PKC and aPKC within cytosolic or enriched membrane fractions of skeletal muscle. These data indicate that aPKC, but not cPKC or PKC, are activated by exercise in contracting muscle suggesting a potential role for aPKC in the regulation of skeletal muscle function and metabolism during exercise in humans.
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Affiliation(s)
- Adam J Rose
- School of Exercise and Nutrition Sciences, Deakin University, Burwood, Victoria 3125, Australia
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Abstract
The roles of diphosphoinositol polyphosphates (DIPs) in mammalian cell biology have been difficult to determine because of the lack of tools known to regulate their levels. I have determined a series of protocols that regulate these DIPs, and these can be used to further our understanding of these molecules. Sorbitol and sucrose significantly raised levels of bis-diphosphoinositol tetrakisphosphate ([PP]2-InsP4) but slightly lowered levels of diphosphoinositol pentakisphosphate (PP-InsP5) in DDT1 MF-2 cells. These effects correlate with the ability of hyperosmotic stress to interfere with protein trafficking described previously and suggest that [PP]2-InsP4 specifically impedes protein trafficking. The effects on [PP]2-InsP4 were not regulated by extracellular signal-regulated kinase or phospholipase D, as exemplified by the lack of effect of U0126 and butan-1-ol. I have also found that genistein potently and rapidly lowers levels of [PP]2-InsP4, whereas a similar inhibitor, herbimycin, was without effect. Thapsigargin, a sarcoplasmic-endoplasmic reticulum Ca(2+)-ATPase pump inhibitor previously shown to selectively lower PP-InsP5 after short-term treatment, also selectively raises PP-InsP5 after a longer treatment. The calmodulin inhibitors N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) and chlorpromazine significantly lowered all higher inositol phosphates, as well as DIPs, whereas the calmodulin-dependent kinase inhibitors methyl 9-(S)-12-(R)-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-2,3,9,10,11,12-hexahydro-10-(R)hydroxy-9-methyl-1-oxo-10-carboxylate (K-252a) and 2-[N-(2-hydroxyethyl)-N-(4-methoxybenzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzylamine (KN-93) were without effect. W-7 and chlorpromazine also lowered levels of phosphatidylinositol 4,5-bisphosphate and ATP but greatly increased levels of phosphatidylinositol 4-phosphate. Trypan blue exclusion deemed that these doses were not cytotoxic. These results identify an increasing number of reagents that regulate DIP levels. Using these tools, and those described previously, we can further understand the roles of the DIPs in cell biology.
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Affiliation(s)
- S T Safrany
- Division of Cell Signaling, University of Dundee, Dundee, Scotland, United Kingdom.
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Abstract
Perturbations of cell hydration as provoked by changes in ambient osmolarity or under isoosmotic conditions by hormones, second messengers, intracellular substrate accumulation, or reactive oxygen intermediates critically contribute to the physiological regulation of cell function. In general an increase in cell hydration stimulates anabolic metabolism and proliferation and provides cytoprotection, whereas cellular dehydration leads to a catabolic situation and sensitizes cells to apoptotic stimuli. Insulin produces cell swelling by inducing a net K+ and Na+ accumulation inside the cell, which results from a concerted activation of Na+/H+ exchange, Na+/K+/2Cl- symport, and the Na+/K(+)-ATPase. In the liver, insulin-induced cell swelling is critical for stimulation of glycogen and protein synthesis as well as inhibition of autophagic proteolysis. These insulin effects can largely be mimicked by hypoosmotic cell swelling, pointing to a role of cell swelling as a trigger of signal transduction. This article discusses insulin-induced signal transduction upstream of swelling and introduces the hypothesis that cell swelling as a signal amplifyer represents an essential component in insulin signaling, which contributes to the full response to insulin at the level of signal transduction and function. Cellular dehydration impairs insulin signaling and may be a major cause of insulin resistance, which develops in systemic hyperosmolarity, nutrient deprivation, uremia, oxidative challenges, and unbalanced production of insulin-counteracting hormones. Hydration changes affect cell functions at multiple levels (such as transcriptom, proteom, phosphoproteom, and the metabolom) and a system biological approach may allow us to develop a more holistic view on the hydration dependence of insulin signaling in the future.
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Affiliation(s)
- Freimut Schliess
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University, Düsseldorf, Germany
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Gual P, Le Marchand-Brustel Y, Tanti J. Positive and negative regulation of glucose uptake by hyperosmotic stress. DIABETES & METABOLISM 2003; 29:566-75. [PMID: 14707885 DOI: 10.1016/s1262-3636(07)70071-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
This review will provide insight on the current understanding of the intracellular signaling mechanisms by which hyperosmolarity mimics insulin responses such as Glut 4 translocation and glucose transport but also antagonizes insulin effects. Glucose uptake induced by insulin is largely dependent on the PI 3-kinase/PKB pathway. In both adipocyte and muscle cells, hyperosmolarity promotes glucose uptake by multiple mechanisms which do not require PI 3-kinase/PKB pathway but are dependent on the cell type. In muscle, osmotic stress induces glucose uptake by stimulation of AMP-Kinase and/or inhibition of Glut 4 endocytosis. In adipocytes, activation of Gab1-dependent signaling pathway plays an important role in osmotic stress-mediated glucose uptake. Apart of its insulin-like effects, hyperosmolarity can lead to cellular insulin resistance mediated by both prevention of PKB activation and inhibition of the Insulin Receptor Substrate-1 (IRS1) function. Serine phosphorylation and degradation of IRS1 negatively regulate its functions. Understanding how osmotic stress induces glucose transport or mediates insulin resistance may provide novel targets for strategies to enhance glucose transport or to prevent insulin resistance.
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Affiliation(s)
- P Gual
- INSERM U 568 and IFR 50, Faculté de Médecine, Avenue de Valombrose, 06107 Nice Cedex 02, France.
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