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Langleben D, Orfanos S. Vasodilator responsiveness in idiopathic pulmonary arterial hypertension: identifying a distinct phenotype with distinct physiology and distinct prognosis. Pulm Circ 2017; 7:588-597. [PMID: 28632001 PMCID: PMC5841907 DOI: 10.1177/2045893217714231] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2017] [Accepted: 05/17/2017] [Indexed: 01/03/2023] Open
Abstract
Within the cohort of patients suffering from idiopathic pulmonary arterial hypertension (IPAH) is a group that responds dramatically (VR-PAH) to an acute vasodilator challenge and that has excellent long-term hemodynamic improvement and prognosis on high dose calcium channel blockers compared with vasodilator non-responders (VN-PAH). For the purposes of diagnosing VR-PAH, there is to date no test to replace the acute vasodilator challenge. However, recent studies have identified markers that may aid in the identification of VR-PAH, including peripheral blood lymphocyte RNA expression levels of desmogelin-2 and Ras homolog gene family member Q, and plasma levels of provirus integration site for Moloney murine leukemia virus. Genome wide-array studies of peripheral blood DNA have demonstrated differences in disease specific genetic variants between VR-PAH and NR-PAH, with particular convergence on cytoskeletal function pathways and Wnt signaling pathways. These studies offer hope for future non-invasive identification of VR-PAH, and insights into pathogenesis that may lead to novel therapies. Examination of the degree of pulmonary microvascular perfusion in PAH has offered additional insights. During the acute vasodilator challenge, VR-PAH patients demonstrate true vasodilation with recruitment and increased perfusion of the capillary bed, while VN-PAH patients are unable to recruit vasculature. In the very few reports of lung histology, VR-PAH has more medial thickening in the precapillary arterioles, while VN-PAH has the classic histology of PAH, including intimal thickening. VR-PAH is a disorder with a phenotype distinct from VN-PAH and other types of PAH, and should be considered separately in the classification of PAH.
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Affiliation(s)
- David Langleben
- Center for Pulmonary Vascular Disease, Division of Cardiology, Jewish General Hospital, McGill University, Montreal, Quebec Canada
| | - Stylianos Orfanos
- Pulmonary Hypertension Clinic, Department of Critical Care, Attikon Hospital, National and Kapodistirian University of Athens, Athens, Greece
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Zhou X, Shentu P, Xu Y. Spatiotemporal Regulators for Insulin-Stimulated GLUT4 Vesicle Exocytosis. J Diabetes Res 2017; 2017:1683678. [PMID: 28529958 PMCID: PMC5424486 DOI: 10.1155/2017/1683678] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 03/21/2017] [Accepted: 04/03/2017] [Indexed: 11/30/2022] Open
Abstract
Insulin increases glucose uptake and storage in muscle and adipose cells, which is accomplished through the mobilization of intracellular GLUT4 storage vesicles (GSVs) to the cell surface upon stimulation. Importantly, the dysfunction of insulin-regulated GLUT4 trafficking is strongly linked with peripheral insulin resistance and type 2 diabetes in human. The insulin signaling pathway, key signaling molecules involved, and precise trafficking itinerary of GSVs are largely identified. Understanding the interaction between insulin signaling molecules and key regulatory proteins that are involved in spatiotemporal regulation of GLUT4 vesicle exocytosis is of great importance to explain the pathogenesis of diabetes and may provide new potential therapeutic targets.
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Affiliation(s)
- Xiaoxu Zhou
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou 310027, China
| | - Ping Shentu
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou 310027, China
| | - Yingke Xu
- Department of Biomedical Engineering, Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou 310027, China
- *Yingke Xu:
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3
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Ackermann KL, Florke RR, Reyes SS, Tader BR, Hamann MJ. TCL/RhoJ Plasma Membrane Localization and Nucleotide Exchange Is Coordinately Regulated by Amino Acids within the N Terminus and a Distal Loop Region. J Biol Chem 2016; 291:23604-23617. [PMID: 27660391 DOI: 10.1074/jbc.m116.750026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Indexed: 01/16/2023] Open
Abstract
TCL/RhoJ is a Cdc42-related Rho GTPase with reported activities in endothelial cell biology and angiogenesis, metastatic melanoma, and corneal epithelial cells; however, less is known about how it is inherently regulated in comparison to its closest homologues TC10 and Cdc42. TCL has an N-terminal extension of 18 amino acids in comparison to Cdc42, but the function of this amino acid sequence has not been elucidated. A truncation mutant lacking the N terminus (ΔN) was found to alter TCL plasma membrane localization and nucleotide binding, and additional truncation and point mutants mapped the alterations of TCL biochemistry to amino acids 17-20. Interestingly, whereas the TCL ΔN mutant clearly influenced nucleotide exchange, deletion of the N terminus from its closest homologue, TC10, did not have a similar effect. Chimeras of TCL and TC10 revealed amino acids 121-129 of TCL contributed to the differences in nucleotide loading. Together, these results identify amino acids within the N terminus and a loop region distal to the nucleotide binding pocket of TCL capable of allosterically regulating nucleotide exchange and thus influence membrane association of the protein.
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Affiliation(s)
- Karly L Ackermann
- From the Biology Department, Bemidji State University, Bemidji, Minnesota 56601
| | - Rebecca R Florke
- From the Biology Department, Bemidji State University, Bemidji, Minnesota 56601
| | - Shannon S Reyes
- From the Biology Department, Bemidji State University, Bemidji, Minnesota 56601
| | - Brooke R Tader
- From the Biology Department, Bemidji State University, Bemidji, Minnesota 56601
| | - Michael J Hamann
- From the Biology Department, Bemidji State University, Bemidji, Minnesota 56601
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4
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Carnagarin R, Dharmarajan AM, Dass CR. Molecular aspects of glucose homeostasis in skeletal muscle--A focus on the molecular mechanisms of insulin resistance. Mol Cell Endocrinol 2015; 417:52-62. [PMID: 26362689 DOI: 10.1016/j.mce.2015.09.004] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2015] [Accepted: 09/02/2015] [Indexed: 01/14/2023]
Abstract
Among all the varied actions of insulin, regulation of glucose homeostasis is the most critical and intensively studied. With the availability of glucose from nutrient metabolism, insulin action in muscle results in increased glucose disposal via uptake from the circulation and storage of excess, thereby maintaining euglycemia. This major action of insulin is executed by redistribution of the glucose transporter protein, GLUT4 from intracellular storage sites to the plasma membrane and storage of glucose in the form of glycogen which also involves modulation of actin dynamics that govern trafficking of all the signal proteins of insulin signal transduction. The cellular mechanisms responsible for these trafficking events and the defects associated with insulin resistance are largely enigmatic, and this review provides a consolidated overview of the various molecular mechanisms involved in insulin-dependent glucose homeostasis in skeletal muscle, as insulin resistance at this major peripheral site impacts whole body glucose homeostasis.
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Affiliation(s)
- Revathy Carnagarin
- Curtin Biosciences Research Precinct, Bentley 6102, Australia; School of Pharmacy, Curtin University, Bentley 6102, Australia
| | - Arun M Dharmarajan
- Curtin Biosciences Research Precinct, Bentley 6102, Australia; School of Biomedical Science, Curtin University, Bentley 6102, Australia
| | - Crispin R Dass
- Curtin Biosciences Research Precinct, Bentley 6102, Australia; School of Pharmacy, Curtin University, Bentley 6102, Australia.
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5
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Hemnes AR, Trammell AW, Archer SL, Rich S, Yu C, Nian H, Penner N, Funke M, Wheeler L, Robbins IM, Austin ED, Newman JH, West J. Peripheral blood signature of vasodilator-responsive pulmonary arterial hypertension. Circulation 2014; 131:401-9; discussion 409. [PMID: 25361553 DOI: 10.1161/circulationaha.114.013317] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Heterogeneity in response to treatment of pulmonary arterial hypertension (PAH) is a major challenge to improving outcome in this disease. Although vasodilator-responsive PAH (VR-PAH) accounts for a minority of cases, VR-PAH has a pronounced response to calcium channel blockers and better survival than vasodilator-nonresponsive PAH (VN-PAH). We hypothesized that VR-PAH has a different molecular cause from VN-PAH that can be detected in the peripheral blood. METHODS AND RESULTS Microarrays of cultured lymphocytes from VR-PAH and VN-PAH patients followed at Vanderbilt University were performed with quantitative polymerase chain reaction performed on peripheral blood for the 25 most different genes. We developed a decision tree to identify VR-PAH patients on the basis of the results with validation in a second VR-PAH cohort from the University of Chicago. We found broad differences in gene expression patterns on microarray analysis including cell-cell adhesion factors and cytoskeletal and rho-GTPase genes. Thirteen of 25 genes tested in whole blood were significantly different: EPDR1, DSG2, SCD5, P2RY5, MGAT5, RHOQ, UCHL1, ZNF652, RALGPS2, TPD52, MKNL1, RAPGEF2, and PIAS1. Seven decision trees were built with the use of expression levels of 2 genes as the primary genes: DSG2, a desmosomal cadherin involved in Wnt/β-catenin signaling, and RHOQ, which encodes a cytoskeletal protein involved in insulin-mediated signaling. These trees correctly identified 5 of 5 VR-PAH patients in the validation cohort. CONCLUSIONS VR-PAH and VN-PAH can be differentiated with the use of RNA expression patterns in peripheral blood. These differences may reflect different molecular causes of the 2 PAH phenotypes. This biomarker methodology may identify PAH patients who have a favorable treatment response.
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Affiliation(s)
- Anna R Hemnes
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.).
| | - Aaron W Trammell
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
| | - Stephen L Archer
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
| | - Stuart Rich
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
| | - Chang Yu
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
| | - Hui Nian
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
| | - Niki Penner
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
| | - Mitchell Funke
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
| | - Lisa Wheeler
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
| | - Ivan M Robbins
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
| | - Eric D Austin
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
| | - John H Newman
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
| | - James West
- From the Division of Allergy, Pulmonary, and Critical Care Medicine (A.R.H., A.W.T., N.P., M.F., L.W., I.M.R., J.H.N., J.W.) and Department of Biostatistics (C.Y., H.N.), Vanderbilt University School of Medicine, Nashville, TN; Department of Medicine, Queen's University, Kingston, Ontario, Canada (S.L.A.); Division of Cardiology, University of Chicago, Chicago, IL (S.R.); and Division of Allergy, Immunology, and Pulmonary Medicine, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN (E.D.A.)
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Okada S, Yamada E, Saito T, Ohshima K, Hashimoto K, Yamada M, Uehara Y, Tsuchiya T, Shimizu H, Tatei K, Izumi T, Yamauchi K, Hisanaga SI, Pessin JE, Mori M. CDK5-dependent phosphorylation of the Rho family GTPase TC10(alpha) regulates insulin-stimulated GLUT4 translocation. J Biol Chem 2008; 283:35455-63. [PMID: 18948252 DOI: 10.1074/jbc.m806531200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Insulin stimulation results in the activation of cyclin-dependent kinase-5 (CDK5) in lipid raft domains via a Fyn-dependent phosphorylation on tyrosine residue 15. In turn, activated CDK5 phosphorylates the Rho family GTP-binding protein TC10alpha on threonine 197 that is sensitive to the CDK5 inhibitor olomoucine and blocked by small interfering RNA-mediated knockdown of CDK5. The phosphorylation deficient mutant T197A-TC10alpha was not phosphorylated and excluded from the lipid raft domain, whereas the phosphorylation mimetic mutant (T197D-TC10alpha) was lipid raft localized. Insulin resulted in the GTP loading of T197D-TC10alpha but not T197A-TC10alpha and in parallel, T197D-TC10alpha but not T197A-TC10alpha depolymerized cortical actin and inhibited insulin-stimulated GLUT4 translocation. These data demonstrate that CDK5-dependent phosphorylation maintains TC10alpha in lipid raft compartments thereby disrupting cortical actin, whereas subsequent dephosphorylation of TC10alpha through inactivation of CDK5 allows for the re-assembly of F-actin. Because cortical actin reorganization is required for insulin-stimulated GLUT4 translocation, these data are consistent with a CDK5-dependent TC10alpha cycling between lipid raft and non-lipid raft compartments.
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Affiliation(s)
- Shuichi Okada
- Department of Medicine, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma 371-0034, Japan.
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7
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Randhawa VK, Ishikura S, Talior-Volodarsky I, Cheng AWP, Patel N, Hartwig JH, Klip A. GLUT4 vesicle recruitment and fusion are differentially regulated by Rac, AS160, and Rab8A in muscle cells. J Biol Chem 2008; 283:27208-19. [PMID: 18650435 DOI: 10.1074/jbc.m804282200] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Insulin increases glucose uptake into muscle by enhancing the surface recycling of GLUT4 transporters. In myoblasts, insulin signals bifurcate downstream of phosphatidylinositol 3-kinase into separate Akt and Rac/actin arms. Akt-mediated Rab-GAP AS160 phosphorylation and Rac/actin are required for net insulin gain of GLUT4, but the specific steps (vesicle recruitment, docking or fusion) regulated by Rac, actin dynamics, and AS160 target Rab8A are unknown. In L6 myoblasts expressing GLUT4myc, blocking vesicle fusion by tetanus toxin cleavage of VAMP2 impeded GLUT4myc membrane insertion without diminishing its build-up at the cell periphery. Conversely, actin disruption by dominant negative Rac or Latrunculin B abolished insulin-induced surface and submembrane GLUT4myc accumulation. Expression of non-phosphorylatable AS160 (AS160-4P) abrogated membrane insertion of GLUT4myc and partially reduced its cortical build-up, an effect magnified by selective Rab8A knockdown. We propose that insulin-induced actin dynamics participates in GLUT4myc vesicle retention beneath the membrane, whereas AS160 phosphorylation is essential for GLUT4myc vesicle-membrane docking/fusion and also contributes to GLUT4myc cortical availability through Rab8A.
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Affiliation(s)
- Varinder K Randhawa
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
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8
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Talior-Volodarsky I, Randhawa VK, Zaid H, Klip A. Alpha-actinin-4 is selectively required for insulin-induced GLUT4 translocation. J Biol Chem 2008; 283:25115-25123. [PMID: 18617516 DOI: 10.1074/jbc.m801750200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Insulin induces GLUT4 translocation to the muscle cell surface. Using differential amino acid labeling and mass spectrometry, we observed insulin-dependent co-precipitation of actinin-4 (ACTN4) with GLUT4 (Foster, L. J., Rudich, A., Talior, I., Patel, N., Huang, X., Furtado, L. M., Bilan, P. J., Mann, M., and Klip, A. (2006) J. Proteome Res. 5, 64-75). ACTN4 links F-actin to membrane proteins, and actin dynamics are essential for GLUT4 translocation. We hypothesized that ACTN4 may contribute to insulin-regulated GLUT4 traffic. In L6 muscle cells insulin, but not platelet-derived growth factor, increased co-precipitation of ACTN4 with GLUT4. Small interfering RNA-mediated ACTN4 knockdown abolished the gain in surface-exposed GLUT4 elicited by insulin but not by platelet-derived growth factor, membrane depolarization, or mitochondrial uncoupling. In contrast, knockdown of alpha-actinin-1 (ACTN1) did not prevent GLUT4 translocation by insulin. GLUT4 colocalized with ACTN4 along the insulin-induced cortical actin mesh and ACTN4 knockdown prevented GLUT4-actin colocalization without impeding actin remodeling or Akt phosphorylation, maintaining GLUT4 in a tight perinuclear location. We propose that ACTN4 contributes to GLUT4 traffic, likely by tethering GLUT4 vesicles to the cortical actin cytoskeleton.
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Affiliation(s)
| | - Varinder K Randhawa
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8; Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Hilal Zaid
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8
| | - Amira Klip
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8; Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
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9
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Insulin action on glucose transporters through molecular switches, tracks and tethers. Biochem J 2008; 413:201-15. [DOI: 10.1042/bj20080723] [Citation(s) in RCA: 214] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Glucose entry into muscle cells is precisely regulated by insulin, through recruitment of GLUT4 (glucose transporter-4) to the membrane of muscle and fat cells. Work done over more than two decades has contributed to mapping the insulin signalling and GLUT4 vesicle trafficking events underpinning this response. In spite of this intensive scientific research, there are outstanding questions that continue to challenge us today. The present review summarizes the knowledge in the field, with emphasis on the latest breakthroughs in insulin signalling at the level of AS160 (Akt substrate of 160 kDa), TBC1D1 (tre-2/USP6, BUB2, cdc16 domain family member 1) and their target Rab proteins; in vesicle trafficking at the level of vesicle mobilization, tethering, docking and fusion with the membrane; and in the participation of the cytoskeleton to achieve optimal temporal and spatial location of insulin-derived signals and GLUT4 vesicles.
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10
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Abstract
The dissection of mechanisms that regulate glucose transport by insulin has revealed an intricate network of signaling molecules scattered from the insulin receptor to the intracellular glucose transporter GLUT4. It is also appreciated that some insulin receptor signals jaunt in different directions to regulate events essential for the efficient redistribution of GLUT4 to the plasma membrane. Moreover key assists in the process appear to be arranged by membrane lipids and cytoskeletal proteins. Following current considerations of insulin signals regulating GLUT4, this review will focus on in vitro and in vivo evidence that supports an essential role for phosphoinositides and actin filaments in the control of glucose transport. The discussion will visit recent cell culture, whole animal, and human data highlighting membrane and cytoskeletal aspects of insulin resistance.
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Affiliation(s)
- Joseph T Brozinick
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN 46285, USA.
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11
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Abstract
Previous studies have suggested that activation of the Rho family member GTPase TC10 is necessary but not sufficient for the stimulation of glucose transport by insulin. We show here that endogenous TC10alpha is rapidly activated in response to insulin in 3T3L1 adipocytes in a phosphatidylinositol 3-kinase-independent manner, whereas platelet-derived growth factor was without effect. Knockdown of TC10alpha but not TC10beta by RNA interference inhibited insulin-stimulated glucose uptake as well as the translocation of the insulin-sensitive glucose transporter GLUT4 from intracellular sites to the plasma membrane. In contrast, loss of TC10alpha had no effect on the stimulation of Akt by insulin. Additionally, knockdown of TC10alpha inhibited insulin-stimulated translocation of its effector CIP4. These data indicate that TC10alpha is specifically required for insulin-stimulated glucose uptake in adipocytes.
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Affiliation(s)
- Louise Chang
- Life Sciences Institute, University of Michigan Medical Center, Ann Arbor, Michigan 48109-2216, USA
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12
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Cortón M, Botella-Carretero JI, Benguría A, Villuendas G, Zaballos A, San Millán JL, Escobar-Morreale HF, Peral B. Differential gene expression profile in omental adipose tissue in women with polycystic ovary syndrome. J Clin Endocrinol Metab 2007; 92:328-37. [PMID: 17062763 DOI: 10.1210/jc.2006-1665] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
CONTEXT The polycystic ovary syndrome (PCOS) is frequently associated with visceral obesity, suggesting that omental adipose tissue might play an important role in the pathogenesis of the syndrome. OBJECTIVE The objective was to study the expression profiles of omental fat biopsy samples obtained from morbidly obese women with or without PCOS at the time of bariatric surgery. DESIGN This was a case-control study. SETTINGS We conducted the study in an academic hospital. PATIENTS Eight PCOS patients and seven nonhyperandrogenic women submitted to bariatric surgery because of morbid obesity. INTERVENTIONS Biopsy samples of omental fat were obtained during bariatric surgery. MAIN OUTCOME MEASURE The main outcome measure was high-density oligonucleotide arrays. RESULTS After statistical analysis, we identified changes in the expression patterns of 63 genes between PCOS and control samples. Gene classification was assessed through data mining of Gene Ontology annotations and cluster analysis of dysregulated genes between both groups. These methods highlighted abnormal expression of genes encoding certain components of several biological pathways related to insulin signaling and Wnt signaling, oxidative stress, inflammation, immune function, and lipid metabolism, as well as other genes previously related to PCOS or to the metabolic syndrome. CONCLUSION The differences in the gene expression profiles in visceral adipose tissue of PCOS patients compared with nonhyperandrogenic women involve multiple genes related to several biological pathways, suggesting that the involvement of abdominal obesity in the pathogenesis of PCOS is more ample than previously thought and is not restricted to the induction of insulin resistance.
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Affiliation(s)
- Marta Cortón
- Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, E-28029 Madrid, Spain
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Hou JC, Suzuki N, Pessin JE, Watson RT. A Specific Dileucine Motif Is Required for the GGA-dependent Entry of Newly Synthesized Insulin-responsive Aminopeptidase into the Insulin-responsive Compartment. J Biol Chem 2006; 281:33457-66. [PMID: 16945927 DOI: 10.1074/jbc.m601583200] [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: 11/06/2022] Open
Abstract
In muscle and adipose cells, the insulin-responsive aminopeptidase (IRAP) is localized to intracellular storage sites and undergoes insulin-dependent redistribution to the cell surface. Following expression, the newly synthesized IRAP protein traffics to the perinuclear insulin-sensitive compartment and acquires insulin sensitivity 6-9 h following biosynthesis. Knockdown of GGA1 by RNA interference prevented IRAP from entering, but not exiting, the insulin-responsive compartment. Mutation of the dileucine motif at positions 76 and 77 (EGFP-IRAP/AA(76,77)), but not the dileucine motif at positions 53 and 54, resulted in the rapid default of the reporter to the cell surface beginning at 3 h following biosynthesis. Alanine substitution of 9 residues amino- or carboxyl-terminal to LL(76,77) did not perturb basal intracellular sequestration or abrogate insulin-stimulated IRAP translocation. Moreover, a dominant interfering GGA mutant (VHS-GAT) potently inhibited insulin-stimulated translocation of EGFP-IRAP/WT but did not block the constitutive exocytotic trafficking of EGFP-IRAP/AA(76,77). In addition, the EGFP-IRAP/WT and EGFP-IRAP/AA(76,77) constructs occupied morphologically distinct tubulovesicular compartments in the perinuclear region. Taken together, these data indicate that LL(76,77) functions during the GGA-dependent sorting of newly made IRAP into the insulin-responsive storage compartment.
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Affiliation(s)
- June Chunqiu Hou
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York 11794-8651, USA
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14
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Hou JC, Shigematsu S, Crawford HC, Anastasiadis PZ, Pessin JE. Dual Regulation of Rho and Rac by p120 Catenin Controls Adipocyte Plasma Membrane Trafficking. J Biol Chem 2006; 281:23307-12. [PMID: 16754687 DOI: 10.1074/jbc.m603127200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
During 3T3L1 adipogenesis there is a marked reduction in beta-catenin and N-cadherin expression with a relatively small decrease in p120 catenin protein levels. Cell fractionation demonstrated a predominant decrease in the particulate (membrane-bound) pool of p120 catenin with little effect on the soluble pool, resulting in a large redistribution from the plasma membrane to the cytosol. Reexpression of p120 catenin inhibited constitutive (transferrin receptor) and regulated mannose 6-phosphate receptor and GLUT4 trafficking to the plasma membrane. The inhibition of membrane trafficking was specific for p120 catenin function as this could be rescued by co-expression of N-cadherin. Moreover, overexpression of a p120 catenin deletion mutant (p120delta622-628) or splice variant (p120-4A), neither of which could regulate Rho or Rac activity, showed no significant effect. The inhibition of GLUT4 translocation was also observed upon the simultaneous expression of a constitutively active Rac mutant (Rac1/Val12) in combination with a dominant-interfering Rho mutant (RhoA/Asn19). This was recapitulated by expression of the Rho ADP-ribosylation factor (C3ADP) in combination with constitutively active Rac1/Val12. Moreover, siRNA-mediated knockdown of p120 catenin resulted in increased basal state accumulation of GLUT4 at the plasma membrane. Together, these data demonstrate that p120 catenin plays an important role in maintaining the basal tone of membrane protein trafficking in adipocytes through the dual regulation of Rho and Rac function and accounts for reports implicating Rho or Rac in the control of GLUT4 translocation.
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Affiliation(s)
- June C Hou
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York 11794-8651, USA
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15
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Inoue M, Chiang SH, Chang L, Chen XW, Saltiel AR. Compartmentalization of the exocyst complex in lipid rafts controls Glut4 vesicle tethering. Mol Biol Cell 2006; 17:2303-11. [PMID: 16525015 PMCID: PMC1446102 DOI: 10.1091/mbc.e06-01-0030] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Lipid raft microdomains act as organizing centers for signal transduction. We report here that the exocyst complex, consisting of Exo70, Sec6, and Sec8, regulates the compartmentalization of Glut4-containing vesicles at lipid raft domains in adipocytes. Exo70 is recruited by the G protein TC10 after activation by insulin and brings with it Sec6 and Sec8. Knockdowns of these proteins block insulin-stimulated glucose uptake. Moreover, their targeting to lipid rafts is required for glucose uptake and Glut4 docking at the plasma membrane. The assembly of this complex also requires the PDZ domain protein SAP97, a member of the MAGUKs family, which binds to Sec8 upon its translocation to the lipid raft. Exocyst assembly at lipid rafts sets up targeting sites for Glut4 vesicles, which transiently associate with these microdomains upon stimulation of cells with insulin. These results suggest that the TC10/exocyst complex/SAP97 axis plays an important role in the tethering of Glut4 vesicles to the plasma membrane in adipocytes.
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Affiliation(s)
- Mayumi Inoue
- Life Sciences Institute, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA
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16
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Thong FSL, Dugani CB, Klip A. Turning signals on and off: GLUT4 traffic in the insulin-signaling highway. Physiology (Bethesda) 2005; 20:271-84. [PMID: 16024515 DOI: 10.1152/physiol.00017.2005] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Insulin stimulation of glucose uptake into skeletal muscle and adipose tissues is achieved by accelerating glucose transporter GLUT4 exocytosis from intracellular compartments to the plasma membrane and minimally reducing its endocytosis. The round trip of GLUT4 is intricately regulated by diverse signaling molecules impinging on specific compartments. Here we highlight the key molecular signals that are turned on and off by insulin to accomplish this task.
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Affiliation(s)
- Farah S L Thong
- Programme in Cell Biology, The Hospital for Sick Children, Ontario, Canada
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17
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Koumanov F, Jin B, Yang J, Holman GD. Insulin signaling meets vesicle traffic of GLUT4 at a plasma-membrane-activated fusion step. Cell Metab 2005; 2:179-89. [PMID: 16154100 DOI: 10.1016/j.cmet.2005.08.007] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Revised: 06/14/2005] [Accepted: 08/16/2005] [Indexed: 11/21/2022]
Abstract
A hypothesis that accounts for most of the available literature on insulin-stimulated GLUT4 translocation is that insulin action controls the access of GLUT4 vesicles to a constitutively active plasma-membrane fusion process. However, using an in vitro fusion assay, we show here that fusion is not constitutively active. Instead, the rate of fusion activity is stimulated 8-fold by insulin. Both the magnitude and time course of stimulated in vitro fusion recapitulate the cellular insulin response. Fusion is cell cytoplasm and SNARE dependent but does not require cell cytoskeleton. Furthermore, insulin activation of the plasma-membrane fraction of the fusion reaction is the essential step in regulation. Akt from the cytoplasm fraction is required for fusion. However, the participation of Akt in the stimulation of in vitro fusion is dependent on its in vitro recruitment onto the insulin-activated plasma membrane.
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18
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Takata K, Tajika Y, Matsuzaki T, Aoki T, Suzuki T, Abduxukur A, Hagiwara H. Molecular mechanisms and drug development in aquaporin water channel diseases: water channel aquaporin-2 of kidney collecting duct cells. J Pharmacol Sci 2005; 96:255-9. [PMID: 15557733 DOI: 10.1254/jphs.fmj04004x3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Aquaporin-2 (AQP2) is one of the membrane water channel proteins expressed in principal cells of the kidney collecting ducts. In the basal state, AQP2 resides in the storage vesicles localized in the subapical cytoplasm. Upon stimulation with vasopressin, AQP2 is translocated to the apical plasma membrane by the exocytic fusion of the storage vesicles with the apical membrane. This translocation enables the transepithelial reabsorption of water from the lumen to the interstitium via AQP2 at the apical membrane and AQP3/AQP4 at the basolateral membrane. AQP2-storage vesicles are distinct from the endoplasmic reticulum, Golgi apparatus, trans-Golgi network, and lysosomes. The early endosomal marker EEA1 is colocalized with some of AQP2 vesicles. Further analyses in Madin-Darby canine kidney (MDCK) cells transfected with AQP2 revealed that subapical Rab11-positive/EEA1-negative smaller vesicles constitute part of the AQP2 storage vesicles for the translocation to the apical membrane. Termination of stimulation results in the retrieval of AQP2 to the larger EEA1-positive early endosomal compartment. AQP2 is then transferred to the subapical storage compartment in a PI3-kinase-dependent manner. GLUT4 is an isoform of glucose transporters whose localization is also regulated by vesicular trafficking induced by insulin stimulation. Comparison of the intracellular localization of AQP2 with GLUT4 suggests distinct regulation of AQP2 trafficking.
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Affiliation(s)
- Kuniaki Takata
- Department of Anatomy and Cell Biology, Gunma University Graduate School of Medicine, Maebashi, Japan.
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19
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Cheng J, Wang H, Guggino WB. Regulation of Cystic Fibrosis Transmembrane Regulator Trafficking and Protein Expression by a Rho Family Small GTPase TC10. J Biol Chem 2005; 280:3731-9. [PMID: 15546864 DOI: 10.1074/jbc.m410026200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR)-interacting protein, CFTR-associated ligand (CAL) down-regulates total and cell surface CFTR by targeting CFTR for degradation in the lysosome. Here, we report that a Rho family small GTPase TC10 interacts with CAL. This interaction specifically up-regulates CFTR protein expression. Co-expression of the constitutively active form, TC10Q75L, increases total and cell surface CFTR in a dose-dependent fashion. Moreover, co-expression of the dominant-negative mutant TC10T31N causes a dose-dependent reduction in mature CFTR. The effect of TC10 is independent of the level of CFTR expression, because a similar effect was observed in a stable cell line that expresses one-tenth of CFTR. Co-expression of TC10Q75L did not have a similar effect on the expression of plasma membrane proteins such as Frizzled-3 and Pr-cadherin or cytosolic proteins such as tubulin and green fluorescent protein. TC10Q75L also did not have a similar effect on the vesicular stomatitis virus glycoprotein. Co-expression of constitutively active and dominant-negative forms of Cdc42 or RhoA did not affect CFTR expression in a manner similar to TC10, indicating that the effect of TC10 is unique within the Rho family. Metabolic pulse-chase experiments show that TC10 did not affect CFTR maturation, suggesting that it exerts its effects on the mature CFTR. Importantly, TC10Q75L reverses CAL-mediated CFTR degradation, suggesting that TC10Q75L inhibits CAL-mediated degradation of CFTR. TC10Q75L does not operate by reducing CAL protein expression or its ability to form dimers or interact with CFTR. Interestingly, the expression of TC10Q75L causes a dramatic redistribution of CAL from the juxtanuclear region to the plasma membrane where the two molecules overlap. These data suggest that TC10 regulates both total and plasma membrane CFTR expression by interacting with CAL. The GTP-bound form of TC10 directs the trafficking of CFTR from the juxtanuclear region to the secretory pathway toward the plasma membrane, away from CAL-mediated degradation of CFTR in the lysosome.
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Affiliation(s)
- Jie Cheng
- Department of Physiology, The Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205, USA
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20
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Yang J, Holman GD. Insulin and Contraction Stimulate Exocytosis, but Increased AMP-activated Protein Kinase Activity Resulting from Oxidative Metabolism Stress Slows Endocytosis of GLUT4 in Cardiomyocytes. J Biol Chem 2005; 280:4070-8. [PMID: 15557332 DOI: 10.1074/jbc.m410213200] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Stimulations of glucose transport produced by insulin action, contraction, or through a change in cell energy status are mediated by separate signaling pathways. These are the wortmannin-sensitive phosphatidylinositol 3-kinase pathway leading to the intermediate Akt and the wortmannin-insensitive AMP-activated protein kinase (AMPK) pathway. Electrical stimulation of cardiomyocytes produced a rapid, insulin-like, wortmannin-sensitive stimulation of glucose transport activity, but this occurred without extensive activation of Akt. Although AMPK phosphorylation was increased by contraction, this response was not wortmannin-inhibitable and consequently did not correlate with the wortmannin sensitivity of the transport stimulation. Oxidative metabolism stress due to hypoxia or treatment with oligomycin led to increased AMPK activity with a corresponding increase in glucose transport activity. We show here that these separate signaling pathways converge on GLUT4 trafficking at separate steps. The rate of exocytosis of GLUT4 was rapidly stimulated by insulin, but insulin treatment did not alter the endocytosis rate. Like insulin stimulation, electrical stimulation of contraction led to a stimulation of GLUT4 exocytosis without any marked change in endocytosis. By contrast, after oxidative metabolism stress, no stimulation of GLUT4 exocytosis occurred; instead, this treatment led to a reduction in GLUT4 endocytosis.
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Affiliation(s)
- Jing Yang
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom
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21
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Shiue H, Musch MW, Wang Y, Chang EB, Turner JR. Akt2 phosphorylates ezrin to trigger NHE3 translocation and activation. J Biol Chem 2004; 280:1688-95. [PMID: 15531580 PMCID: PMC1237052 DOI: 10.1074/jbc.m409471200] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Initiation of Na(+)-glucose cotransport in intestinal absorptive epithelia causes NHE3 to be translocated to the apical plasma membrane, leading to cytoplasmic alkalinization. We reported recently that this NHE3 translocation requires ezrin phosphorylation. However, the kinase that phosphorylates ezrin in this process has not been identified. Because Akt has also been implicated in NHE3 translocation, we investigated the hypothesis that Akt phosphorylates ezrin. After initiation of Na(+)-glucose cotransport, Akt is activated with kinetics that parallel those of ezrin phosphorylation. Inhibition of p38 MAP kinase, which blocks ezrin phosphorylation, also prevents Akt activation. Purified Akt directly phosphorylates recombinant ezrin at threonine 567 in vitro in an ATP-dependent manner. This in vitro phosphorylation can be prevented by Akt inhibitors. In intact cells, inhibition of either phosphoinositide 3-kinase, an upstream regulator of Akt, or inhibition of Akt itself using inhibitors validated in vitro prevents ezrin phosphorylation after initiation of Na(+)-glucose cotransport. Specific small interfering RNA knockdown of Akt2 prevented ezrin phosphorylation in intact cells. Pharmacological Akt inhibition or Akt2 knockdown also prevented NHE3 translocation and activation after initiation of Na(+)-glucose cotransport, confirming the functional role of Akt2. These studies therefore identify Akt2 as a critical kinase that regulates ezrin phosphorylation and activation. This Akt2-dependent ezrin phosphorylation leads to NHE3 translocation and activation.
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Affiliation(s)
| | - Mark W. Musch
- Medicine, The University of Chicago, Chicago, Illinois 60637
| | | | - Eugene B. Chang
- Medicine, The University of Chicago, Chicago, Illinois 60637
| | - Jerrold R. Turner
- From the Departments of Pathology and
- || To whom correspondence should be addressed: 5841 S. Maryland Ave., MC 1089, Chicago, IL 60637. Tel.: 773-702-2433; Fax: 773-834-5251; E-mail:
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22
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Chen G, Raman P, Bhonagiri P, Strawbridge AB, Pattar GR, Elmendorf JS. Protective effect of phosphatidylinositol 4,5-bisphosphate against cortical filamentous actin loss and insulin resistance induced by sustained exposure of 3T3-L1 adipocytes to insulin. J Biol Chem 2004; 279:39705-9. [PMID: 15277534 PMCID: PMC2413414 DOI: 10.1074/jbc.c400171200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Muscle and fat cells develop insulin resistance when cultured under hyperinsulinemic conditions for sustained periods. Recent data indicate that early insulin signaling defects do not fully account for the loss of insulin action. Given that cortical filamentous actin (F-actin) represents an essential aspect of insulin regulated glucose transport, we tested to see whether cortical F-actin structure was compromised during chronic insulin treatment. The acute effect of insulin on GLUT4 translocation and glucose uptake was diminished in 3T3-L1 adipocytes exposed to a physiological level of insulin (5 nm) for 12 h. This insulin-induced loss of insulin responsiveness was apparent under both low (5.5 mm) and high (25 mm) glucose concentrations. Microscopic and biochemical analyses revealed that the hyperinsulinemic state caused a marked loss of cortical F-actin. Since recent data link phosphatidylinositol 4,5-bisphosphate (PIP(2)) to actin cytoskeletal mechanics, we tested to see whether the insulin-resistant condition affected PIP(2) and found a noticeable loss of this lipid from the plasma membrane. Using a PIP(2) delivery system, we replenished plasma membrane PIP(2) in cells following the sustained insulin treatment and observed a restoration in cortical F-actin and insulin responsiveness. These data reveal a novel molecular aspect of insulin-induced insulin resistance involving defects in PIP(2)/actin regulation.
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Affiliation(s)
- Guoli Chen
- Departments of Cellular & Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana 46202
| | - Priya Raman
- Departments of Cellular & Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana 46202
| | - Padma Bhonagiri
- Departments of Cellular & Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana 46202
| | - Andrew B. Strawbridge
- Departments of Cellular & Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana 46202
| | - Guruprasad R. Pattar
- Departments of Cellular & Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana 46202
| | - Jeffrey S. Elmendorf
- Departments of Cellular & Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana 46202
- Biochemistry & Molecular Biology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana 46202
- ** To whom correspondence should be addressed: Dept. of Cellular & Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, IN 46202. Tel.: 317-274-7852; Fax: 317-274-3318; E-mail:
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23
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Brozinick JT, Hawkins ED, Strawbridge AB, Elmendorf JS. Disruption of cortical actin in skeletal muscle demonstrates an essential role of the cytoskeleton in glucose transporter 4 translocation in insulin-sensitive tissues. J Biol Chem 2004; 279:40699-706. [PMID: 15247264 PMCID: PMC2409066 DOI: 10.1074/jbc.m402697200] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Cell culture work suggests that signaling to polymerize cortical filamentous actin (F-actin) represents a required pathway for the optimal redistribution of the insulin-responsive glucose transporter, GLUT4, to the plasma membrane. Recent in vitro study further suggests that the actin-regulatory neural Wiskott-Aldrich syndrome protein (N-WASP) mediates the effect of insulin on the actin filament network. Here we tested whether similar cytoskeletal mechanics are essential for insulin-regulated glucose transport in isolated rat epitrochlearis skeletal muscle. Microscopic analysis revealed that cortical F-actin is markedly diminished in muscle exposed to latrunculin B. Depolymerization of cortical F-actin with latrunculin B caused a time- and concentration-dependent decline in 2-deoxyglucose transport. The loss of cortical F-actin and glucose transport was paralleled by a decline in insulin-stimulated GLUT4 translocation, as assessed by photolabeling of cell surface GLUT4 with Bio-LC-ATB-BMPA. Although latrunculin B impaired insulin-stimulated GLUT4 translocation and glucose transport, activation of phosphatidylinositol 3-kinase and Akt by insulin was not rendered ineffective. In contrast, the ability of insulin to elicit the cortical F-actin localization of N-WASP was abrogated. These data provide the first evidence that actin cytoskeletal mechanics are an essential feature of the glucose transport process in intact skeletal muscle. Furthermore, these findings support a distal actin-based role for N-WASP in insulin action in vivo.
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24
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Sweeney G, Garg RR, Ceddia RB, Li D, Ishiki M, Somwar R, Foster LJ, Neilsen PO, Prestwich GD, Rudich A, Klip A. Intracellular delivery of phosphatidylinositol (3,4,5)-trisphosphate causes incorporation of glucose transporter 4 into the plasma membrane of muscle and fat cells without increasing glucose uptake. J Biol Chem 2004; 279:32233-42. [PMID: 15166230 DOI: 10.1074/jbc.m402897200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Insulin stimulates glucose uptake into muscle and fat cells by translocating glucose transporter 4 (GLUT4) to the cell surface, with input from phosphatidylinositol (PI) 3-kinase and its downstream effector Akt/protein kinase B. Whether PI 3,4,5-trisphosphate (PI(3,4,5)P(3)) suffices to produce GLUT4 translocation is unknown. We used two strategies to deliver PI(3,4,5)P(3) intracellularly and two insulin-sensitive cell lines to examine Akt activation and GLUT4 translocation. In 3T3-L1 adipocytes, the acetoxymethyl ester of PI(3,4,5)P(3) caused GLUT4 migration to the cell periphery and increased the amount of plasma membrane-associated phospho-Akt and GLUT4. Intracellular delivery of PI(3,4,5)P(3) using polyamine carriers also induced translocation of myc-tagged GLUT4 to the surface of intact L6 myoblasts, demonstrating membrane insertion of the transporter. GLUT4 translocation caused by carrier-delivered PI(3,4,5)P(3) was not reproduced by carrier-PI 4,5-bisphosphate or carrier alone. Like insulin, carrier-mediated delivery of PI(3,4,5)P(3) elicited redistribution of perinuclear GLUT4 and Akt phosphorylation at the cell periphery. In contrast to its effect on GLUT4 mobilization, delivered PI(3,4,5)P(3) did not increase 2-deoxyglucose uptake in either L6GLUT4myc myoblasts or 3T3-L1 adipocytes. The ability of exogenously delivered PI(3,4,5)P(3) to augment plasma membrane GLUT4 content without increasing glucose uptake suggests that input at the level of PI 3-kinase suffices for GLUT4 translocation but is insufficient to stimulate glucose transport.
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Affiliation(s)
- Gary Sweeney
- Programme in Cell Biology, Hospital for Sick Children, and Department of Biology, York University, Toronto, Ontario, Canada
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25
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JeBailey L, Rudich A, Huang X, Di Ciano-Oliveira C, Kapus A, Klip A. Skeletal muscle cells and adipocytes differ in their reliance on TC10 and Rac for insulin-induced actin remodeling. Mol Endocrinol 2003; 18:359-72. [PMID: 14615606 DOI: 10.1210/me.2003-0294] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Insulin causes distinct cortical actin remodeling in muscle and fat cells, and interfering with actin dynamics halts glucose transporter 4 (GLUT4) translocation to the membrane. Phosphatidylinositol 3-kinase (PI3-K) and the small G protein Rac govern myocyte actin remodeling, whereas TC10 alpha contributes to adipocyte actin dynamics downstream of Cbl-associated protein (CAP) and Cbl, independently of PI3-K. Given the importance of insulin action in both cell types, it is paramount to determine whether signaling pathways and actin manifestations are cell type specific. We found CAP expression and insulin-mediated Cbl phosphorylation in differentiated myotubes but not in myoblasts. Unlike adipocytes, Cbl is phosphorylated on Y774 and Y731 in myotubes. TC10 alpha and beta-transcripts are amplified by RT-PCR in muscle cells, but the endogenous proteins are barely detectable using two unrelated antibodies. TC10 alpha transfected into myoblasts is activated by insulin despite the lack of CAP expression and Cbl phosphorylation. Moreover, dominant-negative TC10 alpha mutants do not prevent insulin-induced actin remodeling in either myoblasts or myotubes and do not interfere with insulin-mediated recruitment of c-myc epitope-tagged GLUT4 to the cell surface. In contrast to TC10 alpha, endogenous Rac is readily detectable in both muscle cells and adipocytes and binds GTP after insulin in a PI3-K-dependent manner. These data suggest that whereas individual components of the CAP to TC10 pathway are regulated by insulin, a functional TC10-dependent signaling pathway leading to actin remodeling and GLUT4 translocation may not operate in myocytes, as it does in adipocytes.
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Affiliation(s)
- Lellean JeBailey
- Programme in Cell Biology, Hospital for Sick Children, 555 University Ave, Toronto, Ontario, Canada M5G 1X8.
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