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Crossay E, Jullian V, Trinel M, Sagnat D, Hamel D, Groppi E, Rolland C, Stigliani JL, Mejia K, Cabanillas BJ, Alric L, Buscail E, El Kalamouni C, Mavingui P, Deraison C, Racaud-Sultan C, Fabre N. Daphnanes diterpenes from the latex of Hura crepitans L. and their PKCζ-dependent anti-proliferative activity on colorectal cancer cells. Bioorg Med Chem 2023; 90:117366. [PMID: 37329676 DOI: 10.1016/j.bmc.2023.117366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 05/04/2023] [Accepted: 05/30/2023] [Indexed: 06/19/2023]
Abstract
Hura crepitans L. (Euphorbiaceae) is a thorn-covered tree widespread in South America, Africa and Asia which produces an irritating milky latex containing numerous secondary metabolites, notably daphnane-type diterpenes known as Protein Kinase C activators. Fractionation of a dichloromethane extract of the latex led to the isolation of five new daphnane diterpenes (1-5), along with two known analogs (6-7) including huratoxin. Huratoxin (6) and 4',5'-epoxyhuratoxin (4) were found to exhibit significant and selective cell growth inhibition against colorectal cancer cell line Caco-2 and primary colorectal cancer cells cultured as colonoids. The underlying mechanism of 4 and 6 was further investigated revealing the involvement of PKCζ in the cytostatic activity.
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Affiliation(s)
- Elise Crossay
- UMR 152 PharmaDev, Université de Toulouse, IRD, UPS, France
| | | | - Manon Trinel
- UMR 152 PharmaDev, Université de Toulouse, IRD, UPS, France
| | - David Sagnat
- IRSD, Université de Toulouse, INSERM, INRAE, ENVT, UPS, France; Toulouse Organoids Platform, Institut de Recherche en Santé Digestive, INSERM, Toulouse, France
| | - Dimitri Hamel
- IRSD, Université de Toulouse, INSERM, INRAE, ENVT, UPS, France; LAAS-CNRS, Université de Toulouse, CNRS, Toulouse, France
| | - Emie Groppi
- UMR 152 PharmaDev, Université de Toulouse, IRD, UPS, France
| | - Corinne Rolland
- IRSD, Université de Toulouse, INSERM, INRAE, ENVT, UPS, France
| | | | - Kember Mejia
- Instituto de Investigaciones de la Amazonia Peruana (IIAP), Iquitos, Peru
| | - Billy Joel Cabanillas
- Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima 15102, Peru
| | - Laurent Alric
- Pole Digestif, Centre Hospitalier Universitaire, Toulouse, France
| | - Etienne Buscail
- IRSD, Université de Toulouse, INSERM, INRAE, ENVT, UPS, France; Département de Chirurgie Digestive, Unité de Chirurgie Colorectale, Centre Hospitalier Universitaire, Toulouse, France
| | - Chaker El Kalamouni
- UMR PIMIT, Université de La Réunion, INSERM U1187, CNRS 9192, IRD 249, La Réunion, France
| | - Patrick Mavingui
- UMR PIMIT, Université de La Réunion, INSERM U1187, CNRS 9192, IRD 249, La Réunion, France
| | - Céline Deraison
- IRSD, Université de Toulouse, INSERM, INRAE, ENVT, UPS, France
| | | | - Nicolas Fabre
- UMR 152 PharmaDev, Université de Toulouse, IRD, UPS, France.
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2
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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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3
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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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Turnham DJ, Bullock N, Dass MS, Staffurth JN, Pearson HB. The PTEN Conundrum: How to Target PTEN-Deficient Prostate Cancer. Cells 2020; 9:E2342. [PMID: 33105713 PMCID: PMC7690430 DOI: 10.3390/cells9112342] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 10/17/2020] [Accepted: 10/20/2020] [Indexed: 12/17/2022] Open
Abstract
Loss of the tumor suppressor phosphatase and tensin homologue deleted on chromosome 10 (PTEN), which negatively regulates the PI3K-AKT-mTOR pathway, is strongly linked to advanced prostate cancer progression and poor clinical outcome. Accordingly, several therapeutic approaches are currently being explored to combat PTEN-deficient tumors. These include classical inhibition of the PI3K-AKT-mTOR signaling network, as well as new approaches that restore PTEN function, or target PTEN regulation of chromosome stability, DNA damage repair and the tumor microenvironment. While targeting PTEN-deficient prostate cancer remains a clinical challenge, new advances in the field of precision medicine indicate that PTEN loss provides a valuable biomarker to stratify prostate cancer patients for treatments, which may improve overall outcome. Here, we discuss the clinical implications of PTEN loss in the management of prostate cancer and review recent therapeutic advances in targeting PTEN-deficient prostate cancer. Deepening our understanding of how PTEN loss contributes to prostate cancer growth and therapeutic resistance will inform the design of future clinical studies and precision-medicine strategies that will ultimately improve patient care.
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Affiliation(s)
- Daniel J. Turnham
- The European Cancer Stem Cell Research Institute, School of Biosciences, Cardiff University, Hadyn Ellis Building, Cardiff CF24 4HQ, UK; (D.J.T.); (N.B.); (M.S.D.)
| | - Nicholas Bullock
- The European Cancer Stem Cell Research Institute, School of Biosciences, Cardiff University, Hadyn Ellis Building, Cardiff CF24 4HQ, UK; (D.J.T.); (N.B.); (M.S.D.)
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff CF14 4XN, UK;
| | - Manisha S. Dass
- The European Cancer Stem Cell Research Institute, School of Biosciences, Cardiff University, Hadyn Ellis Building, Cardiff CF24 4HQ, UK; (D.J.T.); (N.B.); (M.S.D.)
| | - John N. Staffurth
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff CF14 4XN, UK;
| | - Helen B. Pearson
- The European Cancer Stem Cell Research Institute, School of Biosciences, Cardiff University, Hadyn Ellis Building, Cardiff CF24 4HQ, UK; (D.J.T.); (N.B.); (M.S.D.)
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5
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Rogers TJ. Bidirectional Regulation of Opioid and Chemokine Function. Front Immunol 2020; 11:94. [PMID: 32076421 PMCID: PMC7006827 DOI: 10.3389/fimmu.2020.00094] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 01/14/2020] [Indexed: 12/15/2022] Open
Abstract
The opioid family of GPCRs consists of the classical opioid receptors, designated μ-, κ-, and δ-opioid receptors, and the orphanin-FQ receptor, and these proteins are expressed on both neuronal and hematopoietic cells. A number of laboratories have reported that an important degree of cross-talk can occur between the opioid receptors and the chemokine and chemokine receptor families. As a part of this, the opioid receptors are known to regulate the expression of certain chemokines and chemokine receptors, including those that possess strong pro-inflammatory activity. At the level of receptor function, it is clear that certain members of the chemokine family can mediate cross-desensitization of the opioid receptors. Conversely, the opioid receptors are all able to induce heterologous desensitization of some of the chemokine receptors. Consequently, activation of one or more of the opioid receptors can selectively cross-desensitize chemokine receptors and regulate chemokine function. These cross-talk processes have significant implications for the inflammatory response, since the regulation of both the recruitment of inflammatory cells, as well as the sensation of pain, can be controlled in this way.
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Affiliation(s)
- Thomas J Rogers
- Center for Inflammation, Translational and Clinical Lung Research, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States
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6
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Chau DDL, Yung KWY, Chan WWL, An Y, Hao Y, Chan HYE, Ngo JCK, Lau KF. Attenuation of amyloid-β generation by atypical protein kinase C-mediated phosphorylation of engulfment adaptor PTB domain containing 1 threonine 35. FASEB J 2019; 33:12019-12035. [PMID: 31373844 DOI: 10.1096/fj.201802825rr] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Amyloid-β (Aβ) is derived from the proteolytic processing of amyloid precursor protein (APP), and the deposition of extracellular Aβ to form amyloid plaques is a pathologic hallmark of Alzheimer's disease (AD). Although reducing Aβ generation and accumulation has been proposed as a means of treating the disease, adverse side effects and unsatisfactory efficacy have been reported in several clinical trials that sought to lower Aβ levels. Engulfment adaptor phosphotyrosine-binding (PTB) domain containing 1 (GULP1) is a molecular adaptor that has been shown to interact with APP to alter Aβ production. Therefore, the modulation of the GULP1-APP interaction may be an alternative approach to reducing Aβ. However, the mechanisms that regulate GULP1-APP binding remain elusive. As GULP1 is a phosphoprotein, and because phosphorylation is a common mechanism that regulates protein interaction, we anticipated that GULP1 phosphorylation would influence GULP1-APP interaction and thereby Aβ production. We show here that the phosphorylation of GULP1 threonine 35 (T35) reduces GULP1-APP interaction and suppresses the stimulatory effect of GULP1 on APP processing. The residue is phosphorylated by an isoform of atypical PKC (PKCζ). Overexpression of PKCζ reduces both GULP1-APP interaction and GULP1-mediated Aβ generation. Moreover, the activation of PKCζ via insulin suppresses APP processing. In contrast, GULP1-mediated APP processing is enhanced in PKCζ knockout cells. Similarly, PKC ι, another member of atypical PKC, also decreases GULP1-mediated APP processing. Intriguingly, our X-ray crystal structure of GULP1 PTB-APP intracellular domain (AICD) peptide reveals that GULP1 T35 is not located at the GULP1-AICD binding interface; rather, it immediately precedes the β1-α2 loop that forms a portion of the binding groove for the APP helix αC. Phosphorylating the residue may induce an allosteric effect on the conformation of the binding groove. Our results indicate that GULP1 T35 phosphorylation is a mechanism for the regulation of GULP1-APP interaction and thereby APP processing. Moreover, the activation of atypical PKC, such as by insulin, may confer a beneficial effect on AD by lowering GULP1-mediated Aβ production.-Chau, D. D.-L., Yung, K. W.-Y., Chan, W. W.-L., An, Y., Hao, Y., Chan, H.-Y. E., Ngo, J. C.-K., Lau, K.-F. Attenuation of amyloid-β generation by atypical protein kinase C-mediated phosphorylation of engulfment adaptor PTB domain containing 1 threonine 35.
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Affiliation(s)
- Dennis Dik-Long Chau
- Faculty of Science, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Kristen Wing-Yu Yung
- Faculty of Science, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - William Wai-Lun Chan
- Faculty of Science, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Ying An
- Faculty of Science, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Yan Hao
- Faculty of Science, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Ho-Yin Edwin Chan
- Faculty of Science, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Jacky Chi-Ki Ngo
- Faculty of Science, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Kwok-Fai Lau
- Faculty of Science, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China
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7
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Mehta N, Zhang D, Li R, Wang T, Gava A, Parthasarathy P, Gao B, Krepinsky JC. Caveolin-1 regulation of Sp1 controls production of the antifibrotic protein follistatin in kidney mesangial cells. Cell Commun Signal 2019; 17:37. [PMID: 30995923 PMCID: PMC6472091 DOI: 10.1186/s12964-019-0351-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 04/03/2019] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND We previously showed that caveolin-1 (cav-1), an integral membrane protein, is required for the synthesis of matrix proteins by glomerular mesangial cells (MC). In a previous study to understand how cav-1 is involved in regulating matrix production, we had identified significant upregulation of the antifibrotic protein follistatin in cav-1 knockout MC. Follistatin inhibits the profibrotic effects of several members of the transforming growth factor beta superfamily, in particular the activins. Here, we characterize the molecular mechanism through which cav-1 regulates the expression of follistatin. METHODS Kidneys from cav-1 wild type and knockout (KO) mice were analyzed and primary cultures of MC from cav-1 wild-type and KO mice were utilized. FST promoter deletion constructs were generated to determine the region of the promoter important for mediating FST upregulation in cav-1 KO MC. siRNA-mediated down-regulation and overexpression of Sp1 in conjunction with luciferase activity assays, immunoprecipitation, western blotting and ChiP was used to assess the role of Sp1 in transcriptionally regulating FST expression. Pharmacologic kinase inhibitors and specific siRNA were used to determine the post-translational mechanism through which cav-1 affects Sp1 activity. RESULTS Our results establish that follistatin upregulation occurs at the transcript level. We identified Sp1 as the critical transcription factor regulating activation of the FST promoter in cav-1 KO MC through binding to a region within 123 bp of the transcription start site. We further determined that the lack of cav-1 increases Sp1 nuclear levels and transcriptional activity. This occurred through increased phosphoinositide 3-kinase (PI3K) activity and downstream protein kinase C (PKC) zeta-mediated phosphorylation and activation of Sp1. CONCLUSIONS These findings shed light on the transcriptional mechanism by which cav-1 represses the expression of a major antifibrotic protein, and can inform the development of novel antifibrotic treatment strategies.
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Affiliation(s)
- Neel Mehta
- Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Canada
| | - Dan Zhang
- Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Canada
| | - Renzhong Li
- Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Canada
| | - Tony Wang
- Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Canada
| | - Agata Gava
- Physiological Sciences Graduate Program, Health Sciences Centre, Federal University of Espirito Santo, Vitoria, Brazil
| | | | - Bo Gao
- Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Canada
| | - Joan C Krepinsky
- Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Canada. .,St. Joseph's Hospital, 50 Charlton Ave East, Rm T3311, Hamilton, ON, L8N 4A6, Canada.
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8
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Deevi RK, Javadi A, McClements J, Vohhodina J, Savage K, Loughrey MB, Evergren E, Campbell FC. Protein kinase C zeta suppresses low- or high-grade colorectal cancer (CRC) phenotypes by interphase centrosome anchoring. J Pathol 2018; 244:445-459. [PMID: 29520890 PMCID: PMC5873423 DOI: 10.1002/path.5035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 12/20/2017] [Accepted: 01/01/2018] [Indexed: 01/05/2023]
Abstract
Histological grading provides prognostic stratification of colorectal cancer (CRC) by scoring heterogeneous phenotypes. Features of aggressiveness include aberrant mitotic spindle configurations, chromosomal breakage, and bizarre multicellular morphology, but pathobiology is poorly understood. Protein kinase C zeta (PKCz) controls mitotic spindle dynamics, chromosome segregation, and multicellular patterns, but its role in CRC phenotype evolution remains unclear. Here, we show that PKCz couples genome segregation to multicellular morphology through control of interphase centrosome anchoring. PKCz regulates interdependent processes that control centrosome positioning. Among these, interaction between the cytoskeletal linker protein ezrin and its binding partner NHERF1 promotes the formation of a localized cue for anchoring interphase centrosomes to the cell cortex. Perturbation of these phenomena induced different outcomes in cells with single or extra centrosomes. Defective anchoring of a single centrosome promoted bipolar spindle misorientation, multi-lumen formation, and aberrant epithelial stratification. Collectively, these disturbances induce cribriform multicellular morphology that is typical of some categories of low-grade CRC. By contrast, defective anchoring of extra centrosomes promoted multipolar spindle formation, chromosomal instability (CIN), disruption of glandular morphology, and cell outgrowth across the extracellular matrix interface characteristic of aggressive, high-grade CRC. Because PKCz enhances apical NHERF1 intensity in 3D epithelial cultures, we used an immunohistochemical (IHC) assay of apical NHERF1 intensity as an indirect readout of PKCz activity in translational studies. We show that apical NHERF1 IHC intensity is inversely associated with multipolar spindle frequency and high-grade morphology in formalin-fixed human CRC samples. To conclude, defective PKCz control of interphase centrosome anchoring may underlie distinct categories of mitotic slippage that shape the development of low- or high-grade CRC phenotypes. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.
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Affiliation(s)
- Ravi Kiran Deevi
- Centre for Cancer Research and Cell BiologyQueen's University of BelfastBelfastUK
| | - Arman Javadi
- Centre for Cancer Research and Cell BiologyQueen's University of BelfastBelfastUK
| | - Jane McClements
- Centre for Cancer Research and Cell BiologyQueen's University of BelfastBelfastUK
| | - Jekaterina Vohhodina
- Centre for Cancer Research and Cell BiologyQueen's University of BelfastBelfastUK
| | - Kienan Savage
- Centre for Cancer Research and Cell BiologyQueen's University of BelfastBelfastUK
| | - Maurice Bernard Loughrey
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell BiologyQueen's University Belfast and Belfast Health and Social Care TrustBelfastUK
| | - Emma Evergren
- Centre for Cancer Research and Cell BiologyQueen's University of BelfastBelfastUK
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9
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Zhao G, Wirth D, Schmitz I, Meyer-Hermann M. A mathematical model of the impact of insulin secretion dynamics on selective hepatic insulin resistance. Nat Commun 2017; 8:1362. [PMID: 29118381 PMCID: PMC5678123 DOI: 10.1038/s41467-017-01627-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 10/03/2017] [Indexed: 12/15/2022] Open
Abstract
Physiological insulin secretion exhibits various temporal patterns, the dysregulation of which is involved in diabetes development. We analyzed the impact of first-phase and pulsatile insulin release on glucose and lipid control with various hepatic insulin signaling networks. The mathematical model suggests that atypical protein kinase C (aPKC) undergoes a bistable switch-on and switch-off, under the control of insulin receptor substrate 2 (IRS2). The activation of IRS1 and IRS2 is temporally separated due to the inhibition of IRS1 by aPKC. The model further shows that the timing of aPKC switch-off is delayed by reduced first-phase insulin and reduced amplitude of insulin pulses. Based on these findings, we propose a sequential model of postprandial hepatic control of glucose and lipid by insulin, according to which delayed aPKC switch-off contributes to selective hepatic insulin resistance, which is a long-standing paradox in the field. Dysregulation of insulin secretion dynamics plays a role in diabetes development. Here, the authors build a mathematical model of hepatic insulin signaling and propose a sequential model of post-meal control of glucose and lipids, according to which delayed aPKC suppression would contribute to selective hepatic insulin resistance.
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Affiliation(s)
- Gang Zhao
- Department of Systems Immunology and Braunschweig Integrated Centre of Systems Biology, Helmholtz Centre for Infection Research, Rebenring 56, 38106, Braunschweig, Germany
| | - Dagmar Wirth
- Model Systems for Infection and Immunity, Helmholtz Centre for Infection Research, Inhoffenstraße 7, 38124, Braunschweig, Germany.,Institute of Experimental Hematology, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany
| | - Ingo Schmitz
- Systems-Oriented Immunology and Inflammation Research Group, Department of Immune Control, Helmholtz Centre for Infection Research, Inhoffenstraße 7, 38124, Braunschweig, Germany.,Institute for Molecular and Clinical Immunology, Otto-von-Guericke University, Leipziger Straße 44, 39120, Magdeburg, Germany
| | - Michael Meyer-Hermann
- Department of Systems Immunology and Braunschweig Integrated Centre of Systems Biology, Helmholtz Centre for Infection Research, Rebenring 56, 38106, Braunschweig, Germany. .,Institute of Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Spielmannstraße 7, 38106, Braunschweig, Germany.
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10
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PKCζ phosphorylates TRAF2 to protect against intestinal ischemia-reperfusion-induced injury. Cell Death Dis 2017; 8:e2935. [PMID: 28726782 PMCID: PMC5550857 DOI: 10.1038/cddis.2017.310] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 06/02/2017] [Accepted: 06/05/2017] [Indexed: 12/25/2022]
Abstract
Intestinal ischemia-reperfusion (I/R) is a common clinical problem that occurs during various clinical pathological processes. Excessive apoptosis has an indispensable role in intestinal I/R injury. Tumor necrosis factor receptor-associated factor 2 (TRAF2) and PKCζ have an essential role in apoptosis. Here, we aimed to investigate the effects of PKCζ and TRAF2 and to explore the correlation between PKCζ and TRAF2 in intestinal I/R injury. Mice were subjected to intestinal I/R injury in vivo. In vitro experiments were conducted by treating Caco-2 cells with hypoxia/reoxygenation (H/R) stimulation to simulate intestinal I/R. Intestinal tissue samples and Caco-2 cells were examined using various approaches. Intestinal I/R induced the membrane translocation and phosphorylation of PKCζ. Pretreatment with the PKCζ activator phosphatidylcholine remarkably attenuated gut injury by suppressing apoptosis. H/R induced PKCζ to combine with TRAF2, which was phosphorylated by PKCζ at Ser55, but not at Ser11, under intestinal I/R or H/R conditions. In addition, TRAF2 Ser55 phosphorylation increased cell survival by inhibiting cell apoptosis in the H/R model. Mechanistically, TRAF2 Ser55 phosphorylation promoted NF-κB activation but suppressed c-Jun activation in Caco-2 cells under H/R conditions. The results of this study demonstrate that the PKCζ/TRAF2 pathway represents a novel protective mechanism against intestinal I/R injury. Therefore, the PKCζ/TRAF2 pathway is a novel target for potential treatments of intestinal I/R injury-related diseases.
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11
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Baek HS, Park N, Kwon YJ, Ye DJ, Shin S, Chun YJ. Annexin A5 suppresses cyclooxygenase-2 expression by downregulating the protein kinase C-ζ-nuclear factor-κB signaling pathway in prostate cancer cells. Oncotarget 2017; 8:74263-74275. [PMID: 29088783 PMCID: PMC5650338 DOI: 10.18632/oncotarget.19392] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 06/17/2017] [Indexed: 12/17/2022] Open
Abstract
Annexin A5 (ANXA5) is a member of the annexin protein family. Previous studies have shown that ANXA5 is involved in anti-inflammation and cell death. However, the detailed mechanism of the role of ANXA5 in cancer cells is not well understood. In this study, we investigated the inhibitory effect of ANXA5 on cyclooxygenase-2 (COX-2) in prostate cancer cells. Expression of COX-2 induced by TNF-α was inhibited by overexpression of ANXA5 and inhibition of COX-2 expression by auranofin, which could induce ANXA5 expression, was restored by ANXA5 knockdown. In addition, ANXA5 knockdown induces phosphorylation of NF-κB p65 in prostate cancer cells, indicating that ANXA5 causes COX-2 downregulation through inhibition of p65 activation. We also found that protein kinase C (PKC)-ζ protein levels were upregulated by the inhibition of ANXA5, although the mRNA levels were unaffected. We have shown that upregulated COX-2 expression by inhibition of ANXA5 is attenuated by PKC-ζ siRNA. In summary, this study demonstrates that downregulation of PKC-ζ-NF-κB signaling by ANXA5 may inhibit COX-2 expression in prostate cancer.
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Affiliation(s)
- Hyoung-Seok Baek
- College of Pharmacy and Center for Metareceptome Research, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Nahee Park
- College of Pharmacy and Center for Metareceptome Research, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Yeo-Jung Kwon
- College of Pharmacy and Center for Metareceptome Research, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Dong-Jin Ye
- College of Pharmacy and Center for Metareceptome Research, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Sangyun Shin
- College of Pharmacy and Center for Metareceptome Research, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Young-Jin Chun
- College of Pharmacy and Center for Metareceptome Research, Chung-Ang University, Seoul 06974, Republic of Korea
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12
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Farese RV, Sajan MP, Standaert ML. Insulin-Sensitive Protein Kinases (Atypical Protein Kinase C and Protein Kinase B/Akt): Actions and Defects in Obesity and Type II Diabetes. Exp Biol Med (Maywood) 2016; 230:593-605. [PMID: 16179727 DOI: 10.1177/153537020523000901] [Citation(s) in RCA: 142] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Glucose transport into muscle is the initial process in glucose clearance and is uniformly defective in insulin-resistant conditions of obesity, metabolic syndrome, and Type II diabetes mellitus. Insulin regulates glucose transport by activating insulin receptor substrate-1 (IRS-1)-dependent phosphatidylinositol 3-kinase (PI3K) which, via increases in PI-3, 4, 5-triphosphate (PIP3), activates atypical protein kinase C (aPKC) and protein kinase B (PKB/Akt). Here, we review (i) the evidence that both aPKC and PKB are required for insulin-stimulated glucose transport, (ii) abnormalities in muscle aPKC/PKB activation seen in obesity and diabetes, and (iii) mechanisms for impaired aPKC activation in insulin-resistant conditions. In most cases, defective muscle aPKC/PKB activation reflects both impaired activation of IRS-1/PI3K, the upstream activator of aPKC and PKB in muscle and, in the case of aPKC, poor responsiveness to PIP3, the lipid product of PI3K. Interestingly, insulin-sensitizing agents (e.g., thiazolidinediones, metformin) improve aPKC activation by insulin in vivo and PIP3 in vitro, most likely by activating 5′-adenosine monophosphate-activated protein kinase, which favorably alters intracellular lipid metabolism. Differently from muscle, aPKC activation in the liver is dependent on IRS-2/PI3K rather than IRS-1/PI3K and, surprisingly, the activation of IRS-2/PI3K and aPKC is conserved in high-fat feeding, obesity, and diabetes. This conservation has important implications, as continued activation of hepatic aPKC in hyperinsulinemic states may increase the expression of sterol regulatory element binding protein-1c, which controls genes that increase hepatic lipid synthesis. On the other hand, the defective activation of IRS-1/PI3K and PKB, as seen in diabetic liver, undoubtedly and importantly contributes to increases in hepatic glucose output. Thus, the divergent activation of aPKC and PKB in the liver may explain why some hepatic actions of insulin (e.g., aPKC-dependent lipid synthesis) are increased while other actions (e.g., PKB-dependent glucose metabolism) are diminished. This may explain the paradox that the liver secretes excessive amounts of both very low density lipoprotein triglycerides and glucose in Type II diabetes. Previous reviews from our laboratory that have appeared in the Proceedings have provided essentials on phospholipid-signaling mechanisms used by insulin to activate several protein kinases that seem to be important in mediating the metabolic effects of insulin. During recent years, there have been many new advances in our understanding of how these lipid-dependent protein kinases function during insulin action and why they fail to function in states of insulin resistance. The present review will attempt to summarize what we believe are some of the more important advances.
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Affiliation(s)
- Robert V Farese
- James A. Haley Veterans Administration Hospital Research Service and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, FL 33612, USA.
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13
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Donovan EL, Buckels EJ, Hancock S, Smeitink D, Oliver MH, Bloomfield FH, Jaquiery AL. Twin Conception in Sheep Leads to Impaired Insulin Sensitivity and Sexually Dimorphic Adipose Tissue and Skeletal Muscle Phenotypes in Adulthood. Reprod Sci 2016; 24:865-881. [DOI: 10.1177/1933719116670516] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Elise L. Donovan
- Liggins Institute, University of Auckland, Auckland, New Zealand
- Gravida: National Centre for Growth and Development, Auckland, New Zealand
| | - Emma J. Buckels
- Liggins Institute, University of Auckland, Auckland, New Zealand
| | - Serina Hancock
- Liggins Institute, University of Auckland, Auckland, New Zealand
- School of Veterinary and Life Sciences, Murdoch University, Perth, WA, Australia
| | | | - Mark H. Oliver
- Liggins Institute, University of Auckland, Auckland, New Zealand
- Gravida: National Centre for Growth and Development, Auckland, New Zealand
| | - Frank H. Bloomfield
- Liggins Institute, University of Auckland, Auckland, New Zealand
- Gravida: National Centre for Growth and Development, Auckland, New Zealand
- Department of Paediatrics, Child and Youth Health, University of Auckland, Auckland, New Zealand
| | - Anne L. Jaquiery
- Liggins Institute, University of Auckland, Auckland, New Zealand
- Gravida: National Centre for Growth and Development, Auckland, New Zealand
- Department of Paediatrics, Child and Youth Health, University of Auckland, Auckland, New Zealand
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14
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Deevi RK, McClements J, McCloskey KD, Fatehullah A, Tkocz D, Javadi A, Higginson R, Durban VM, Jansen M, Clarke A, Loughrey MB, Campbell FC. Vitamin D3 suppresses morphological evolution of the cribriform cancerous phenotype. Oncotarget 2016; 7:49042-49064. [PMID: 27119498 PMCID: PMC5226489 DOI: 10.18632/oncotarget.8863] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 02/28/2016] [Indexed: 12/14/2022] Open
Abstract
Development of cribriform morphology (CM) heralds malignant change in human colon but lack of mechanistic understanding hampers preventive therapy. This study investigated CM pathobiology in three-dimensional (3D) Caco-2 culture models of colorectal glandular architecture, assessed translational relevance and tested effects of 1,25(OH)2D3,theactive form of vitamin D. CM evolution was driven by oncogenic perturbation of the apical polarity (AP) complex comprising PTEN, CDC42 and PRKCZ (phosphatase and tensin homolog, cell division cycle 42 and protein kinase C zeta). Suppression of AP genes initiated a spatiotemporal cascade of mitotic spindle misorientation, apical membrane misalignment and aberrant epithelial configuration. Collectively, these events promoted "Swiss cheese-like" cribriform morphology (CM) comprising multiple abnormal "back to back" lumens surrounded by atypical stratified epithelium, in 3D colorectal gland models. Intestinal cancer driven purely by PTEN-deficiency in transgenic mice developed CM and in human CRC, CM associated with PTEN and PRKCZ readouts. Treatment of PTEN-deficient 3D cultures with 1,25(OH)2D3 upregulated PTEN, rapidly activated CDC42 and PRKCZ, corrected mitotic spindle alignment and suppressed CM development. Conversely, mutationally-activated KRAS blocked1,25(OH)2D3 rescue of glandular architecture. We conclude that 1,25(OH)2D3 upregulates AP signalling to reverse CM in a KRAS wild type (wt), clinically predictive CRC model system. Vitamin D could be developed as therapy to suppress inception or progression of a subset of colorectal tumors.
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Affiliation(s)
- Ravi K. Deevi
- Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Belfast, UK
| | - Jane McClements
- Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Belfast, UK
| | - Karen D. McCloskey
- Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Belfast, UK
| | - Aliya Fatehullah
- Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Belfast, UK
| | - Dorota Tkocz
- Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Belfast, UK
| | - Arman Javadi
- Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Belfast, UK
| | - Robyn Higginson
- Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Belfast, UK
| | | | - Marnix Jansen
- Barts Cancer Institute, Queen Mary University of London, John Vane Science Centre, London, UK
| | - Alan Clarke
- European Cancer Stem Cell Research Institute, Cardiff University, Cardiff, UK
| | - Maurice B. Loughrey
- Northern Ireland Molecular Pathology Laboratory, Centre for Cancer Research and Cell Biology, Queens University Belfast and Belfast Health and Social Care Trust, Belfast, UK
| | - Frederick C. Campbell
- Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Belfast, UK
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15
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Tobias IS, Newton AC. Protein Scaffolds Control Localized Protein Kinase Cζ Activity. J Biol Chem 2016; 291:13809-22. [PMID: 27143478 DOI: 10.1074/jbc.m116.729483] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Indexed: 11/06/2022] Open
Abstract
Atypical protein kinase C (aPKC) isozymes modulate insulin signaling and cell polarity, but how their activity is controlled in cells is not well understood. These enzymes are constitutively phosphorylated, insensitive to second messengers, and have relatively low activity. Here we show that protein scaffolds not only localize but also differentially control the catalytic activity of the aPKC PKCζ, thus promoting activity toward localized substrates and restricting activity toward global substrates. Using cellular substrate readouts and scaffolded activity reporters in live cell imaging, we show that PKCζ has highly localized and differentially controlled activity on the scaffolds p62 and Par6. Both scaffolds tether aPKC in an active conformation as assessed through pharmacological inhibition of basal activity, monitored using a genetically encoded reporter for PKC activity. However, binding to Par6 is of higher affinity and is more effective in locking PKCζ in an active conformation. FRET-based translocation assays reveal that insulin promotes the association of both p62 and aPKC with the insulin-regulated scaffold IRS-1. Using the aPKC substrate MARK2 as another readout for activity, we show that overexpression of IRS-1 reduces the phosphorylation of MARK2 and enhances its plasma membrane localization, indicating sequestration of aPKC by IRS-1 away from MARK2. These results are consistent with scaffolds serving as allosteric activators of aPKCs, tethering them in an active conformation near specific substrates. Thus, signaling of these intrinsically low activity kinases is kept at a minimum in the absence of scaffolding interactions, which position the enzymes for stoichiometric phosphorylation of substrates co-localized on the same protein scaffold.
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Affiliation(s)
- Irene S Tobias
- From the Department of Pharmacology and Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, California 92093
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16
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Molecular Control of Atypical Protein Kinase C: Tipping the Balance between Self-Renewal and Differentiation. J Mol Biol 2016; 428:1455-64. [PMID: 26992354 DOI: 10.1016/j.jmb.2016.03.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 02/20/2016] [Accepted: 03/03/2016] [Indexed: 01/05/2023]
Abstract
Complex organisms are faced with the challenge of generating and maintaining diverse cell types, ranging from simple epithelia to neurons and motile immune cells [1-3]. To meet this challenge, a complex set of regulatory pathways controls nearly every aspect of cell growth and function, including genetic and epigenetic programming, cytoskeleton dynamics, and protein trafficking. The far reach of cell fate specification pathways makes it particularly catastrophic when they malfunction, both during development and for tissue homeostasis in adult organisms. Furthermore, the therapeutic promise of stem cells derives from their ability to deftly navigate the multitude of pathways that control cell fate [4]. How the molecular components making up these pathways function to specify cell fate is beginning to become clear. Work from diverse systems suggests that the atypical Protein Kinase C (aPKC) is a key regulator of cell fate decisions in metazoans [5-7]. Here, we examine some of the diverse physiological outcomes of aPKC's function in differentiation, along with the molecular pathways that control aPKC and those that are responsive to changes in its catalytic activity.
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17
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Protein kinase Cζ exhibits constitutive phosphorylation and phosphatidylinositol-3,4,5-triphosphate-independent regulation. Biochem J 2015; 473:509-23. [PMID: 26635352 DOI: 10.1042/bj20151013] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 12/03/2015] [Indexed: 12/21/2022]
Abstract
Atypical protein kinase C (aPKC) isoenzymes are key modulators of insulin signalling, and their dysfunction correlates with insulin-resistant states in both mice and humans. Despite the engaged interest in the importance of aPKCs to type 2 diabetes, much less is known about the molecular mechanisms that govern their cellular functions than for the conventional and novel PKC isoenzymes and the functionally-related protein kinase B (Akt) family of kinases. Here we show that aPKC is constitutively phosphorylated and, using a genetically-encoded reporter for PKC activity, basally active in cells. Specifically, we show that phosphorylation at two key regulatory sites, the activation loop and turn motif, of the aPKC PKCζ in multiple cultured cell types is constitutive and independently regulated by separate kinases: ribosome-associated mammalian target of rapamycin complex 2 (mTORC2) mediates co-translational phosphorylation of the turn motif, followed by phosphorylation at the activation loop by phosphoinositide-dependent kinase-1 (PDK1). Live cell imaging reveals that global aPKC activity is constitutive and insulin unresponsive, in marked contrast to the insulin-dependent activation of Akt monitored by an Akt-specific reporter. Nor does forced recruitment to phosphoinositides by fusing the pleckstrin homology (PH) domain of Akt to the kinase domain of PKCζ alter either the phosphorylation or activity of PKCζ. Thus, insulin stimulation does not activate PKCζ through the canonical phosphatidylinositol-3,4,5-triphosphate-mediated pathway that activates Akt, contrasting with previous literature on PKCζ activation. These studies support a model wherein an alternative mechanism regulates PKCζ-mediated insulin signalling that does not utilize conventional activation via agonist-evoked phosphorylation at the activation loop. Rather, we propose that scaffolding near substrates drives the function of PKCζ.
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18
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Fang XQ, Qiao H, Groveman BR, Feng S, Pflueger M, Xin WK, Ali MK, Lin SX, Xu J, Duclot F, Kabbaj M, Wang W, Ding XS, Santiago-Sim T, Jiang XH, Salter MW, Yu XM. Regulated internalization of NMDA receptors drives PKD1-mediated suppression of the activity of residual cell-surface NMDA receptors. Mol Brain 2015; 8:75. [PMID: 26584860 PMCID: PMC4653853 DOI: 10.1186/s13041-015-0167-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 11/13/2015] [Indexed: 12/13/2022] Open
Abstract
Background Constitutive and regulated internalization of cell surface proteins has been extensively investigated. The regulated internalization has been characterized as a principal mechanism for removing cell-surface receptors from the plasma membrane, and signaling to downstream targets of receptors. However, so far it is still not known whether the functional properties of remaining (non-internalized) receptor/channels may be regulated by internalization of the same class of receptor/channels. The N-methyl-D-aspartate receptor (NMDAR) is a principal subtype of glutamate-gated ion channel and plays key roles in neuronal plasticity and memory functions. NMDARs are well-known to undergo two types of regulated internalization – homologous and heterologous, which can be induced by high NMDA/glycine and DHPG, respectively. In the present work, we investigated effects of regulated NMDAR internalization on the activity of residual cell-surface NMDARs and neuronal functions. Results In electrophysiological experiments we discovered that the regulated internalization of NMDARs not only reduced the number of cell surface NMDARs but also caused an inhibition of the activity of remaining (non-internalized) surface NMDARs. In biochemical experiments we identified that this functional inhibition of remaining surface NMDARs was mediated by increased serine phosphorylation of surface NMDARs, resulting from the activation of protein kinase D1 (PKD1). Knockdown of PKD1 did not affect NMDAR internalization but prevented the phosphorylation and inhibition of remaining surface NMDARs and NMDAR-mediated synaptic functions. Conclusion These data demonstrate a novel concept that regulated internalization of cell surface NMDARs not only reduces the number of NMDARs on the cell surface but also causes an inhibition of the activity of remaining surface NMDARs through intracellular signaling pathway(s). Furthermore, modulating the activity of remaining surface receptors may be an effective approach for treating receptor internalization-induced changes in neuronal functions of the CNS. Electronic supplementary material The online version of this article (doi:10.1186/s13041-015-0167-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Xiao-Qian Fang
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, 32306, USA.
| | - Haifa Qiao
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, 32306, USA.
| | - Bradley R Groveman
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, 32306, USA.
| | - Shuang Feng
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, 32306, USA.
| | - Melissa Pflueger
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, 32306, USA.
| | - Wen-Kuan Xin
- Faculty of Dentistry, University of Toronto, Toronto, M5G 1G6, Canada.
| | - Mohammad K Ali
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, 32306, USA.
| | - Shuang-Xiu Lin
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, 32306, USA.
| | - Jindong Xu
- Faculty of Dentistry, University of Toronto, Toronto, M5G 1G6, Canada.
| | - Florian Duclot
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, 32306, USA.
| | - Mohamed Kabbaj
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, 32306, USA.
| | - Wei Wang
- Department of Neurology, 1st Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, PR China.
| | - Xin-Sheng Ding
- Department of Neurology, 1st Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, PR China. .,BenQ Neurological Institute, Nanjing Medical University, Nanjing, 210021, PR China.
| | - Teresa Santiago-Sim
- Department of Neurosurgery, The University of Texas Medical School at Houston Vivian L. Smith, Houston, TX, 77030, USA.
| | - Xing-Hong Jiang
- Department of Physiology and Neurobiology, Medical College of Soochow University, Suzhou, 215123, China.
| | - Michael W Salter
- Program in Neuroscience and Mental Health, Hospital for Sick Children, University of Toronto, Toronto, M5G 1X8, Canada.
| | - Xian-Min Yu
- Department of Biomedical Sciences, Florida State University, Tallahassee, FL, 32306, USA. .,Faculty of Dentistry, University of Toronto, Toronto, M5G 1G6, Canada. .,BenQ Neurological Institute, Nanjing Medical University, Nanjing, 210021, PR China. .,Department of Physiology and Neurobiology, Medical College of Soochow University, Suzhou, 215123, China.
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19
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Sajan MP, Ivey RA, Farese RV. BMI-related progression of atypical PKC-dependent aberrations in insulin signaling through IRS-1, Akt, FoxO1 and PGC-1α in livers of obese and type 2 diabetic humans. Metabolism 2015; 64:1454-65. [PMID: 26386696 PMCID: PMC4576742 DOI: 10.1016/j.metabol.2015.08.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 08/19/2015] [Accepted: 08/20/2015] [Indexed: 12/16/2022]
Abstract
Information on insulin resistance in human liver is limited. In mouse diet-induced obesity (DIO), hepatic insulin resistance initially involves: lipid+insulin-induced activation of atypical protein kinase C (aPKC); elevated Akt activity/activation but selective impairment of compartmentalized Akt-dependent FoxO1 phosphorylation; and increases in gluconeogenic and lipogenic enzymes. In advanced stages, e.g., in hepatocytes of type 2 diabetes (T2D) humans, insulin activation of insulin receptor substrate-1(IRS-1) and Akt fails, further increasing FoxO1-dependent gluconeogenic/lipogenic enzyme expression. Increases in hepatic PGC-1α also figure prominently, but uncertainly, in this scheme. Here, we examined signaling factors in liver samples harvested from human transplant donors with increasing BMI, 20→25→30→35→40→45. We found, relative to lean (BMI=20-25) humans, obese (BMI>30) humans had all abnormalities seen in early mouse DIO, but, surprisingly, at all elevated BMI levels, had decreased insulin receptor-1 (IRS-1) levels, decreased Akt activity, and increased expression/abundance of aPKC-ι and PGC-1α. Moreover, with increasing BMI, there were: progressive increases in aPKC activity and PKC-ι expression/abundance; progressive decreases in IRS-1 levels, Akt activity and FoxO1 phosphorylation; progressive increases in expression/abundance of PGC-1α; and progressive increases in gluconeogenic and lipogenic enzymes. Remarkably, all abnormalities reached T2D levels at higher BMI levels. Most importantly, both "early" and advanced abnormalities were largely reversed by 24-hour treatment of T2D hepatocytes with aPKC inhibitor. We conclude: hepatic insulin resistance in human obesity is: advanced; BMI-correlated; and sequentially involves increased aPKC-activating ceramide; increased aPKC levels and activity; decreases in IRS-1 levels, Akt activity, and FoxO1 phosphorylation; and increases in expression/abundance of PGC-1α and gluconeogenic and lipogenic genes.
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Affiliation(s)
- Mini P Sajan
- Research and Internal Medicine Services of the James A. Haley VA Medical Center, Tampa, FL; Department of Internal Medicine, University of South Florida College of Medicine, Tampa, FL
| | - Robert A Ivey
- Research and Internal Medicine Services of the James A. Haley VA Medical Center, Tampa, FL
| | - Robert V Farese
- Research and Internal Medicine Services of the James A. Haley VA Medical Center, Tampa, FL; Department of Internal Medicine, University of South Florida College of Medicine, Tampa, FL.
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20
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Bailey MJ, Prehoda KE. Establishment of Par-Polarized Cortical Domains via Phosphoregulated Membrane Motifs. Dev Cell 2015; 35:199-210. [PMID: 26481050 DOI: 10.1016/j.devcel.2015.09.016] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 09/03/2015] [Accepted: 09/23/2015] [Indexed: 01/06/2023]
Abstract
The Par polarity complex creates mutually exclusive cortical domains in diverse animal cells. Activity of the atypical protein kinase C (aPKC) is a key output of the Par complex as phosphorylation removes substrates from the Par domain. Here, we investigate how diverse, apparently unrelated Par substrates couple phosphorylation to cortical displacement. Each protein contains a basic and hydrophobic (BH) motif that interacts directly with phospholipids and also overlaps with aPKC phosphorylation sites. Phosphorylation alters the electrostatic character of the sequence, inhibiting interaction with phospholipids and the cell cortex. We searched for overlapping BH and aPKC phosphorylation site motifs (i.e., putative phosphoregulated BH motifs) in several animal proteomes. Candidate proteins with strong PRBH signals associated with the cell cortex but were displaced into the cytoplasm by aPKC. These findings demonstrate a potentially general mechanism for exclusion of proteins from the Par cortical domain in polarized cells.
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Affiliation(s)
- Matthew J Bailey
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Kenneth E Prehoda
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.
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21
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Halls ML, Bathgate RAD, Sutton SW, Dschietzig TB, Summers RJ. International Union of Basic and Clinical Pharmacology. XCV. Recent advances in the understanding of the pharmacology and biological roles of relaxin family peptide receptors 1-4, the receptors for relaxin family peptides. Pharmacol Rev 2015; 67:389-440. [PMID: 25761609 DOI: 10.1124/pr.114.009472] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Relaxin, insulin-like peptide 3 (INSL3), relaxin-3, and INSL5 are the cognate ligands for the relaxin family peptide (RXFP) receptors 1-4, respectively. RXFP1 activates pleiotropic signaling pathways including the signalosome protein complex that facilitates high-sensitivity signaling; coupling to Gα(s), Gα(i), and Gα(o) proteins; interaction with glucocorticoid receptors; and the formation of hetero-oligomers with distinctive pharmacological properties. In addition to relaxin-related ligands, RXFP1 is activated by Clq-tumor necrosis factor-related protein 8 and by small-molecular-weight agonists, such as ML290 [2-isopropoxy-N-(2-(3-(trifluoromethylsulfonyl)phenylcarbamoyl)phenyl)benzamide], that act allosterically. RXFP2 activates only the Gα(s)- and Gα(o)-coupled pathways. Relaxin-3 is primarily a neuropeptide, and its cognate receptor RXFP3 is a target for the treatment of depression, anxiety, and autism. A variety of peptide agonists, antagonists, biased agonists, and an allosteric modulator target RXFP3. Both RXFP3 and the related RXFP4 couple to Gα(i)/Gα(o) proteins. INSL5 has the properties of an incretin; it is secreted from the gut and is orexigenic. The expression of RXFP4 in gut, adipose tissue, and β-islets together with compromised glucose tolerance in INSL5 or RXFP4 knockout mice suggests a metabolic role. This review focuses on the many advances in our understanding of RXFP receptors in the last 5 years, their signal transduction mechanisms, the development of novel compounds that target RXFP1-4, the challenges facing the field, and current prospects for new therapeutics.
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Affiliation(s)
- Michelle L Halls
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Ross A D Bathgate
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Steve W Sutton
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Thomas B Dschietzig
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Roger J Summers
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
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22
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Jalil SJ, Sacktor TC, Shouval HZ. Atypical PKCs in memory maintenance: the roles of feedback and redundancy. ACTA ACUST UNITED AC 2015; 22:344-53. [PMID: 26077687 PMCID: PMC4478332 DOI: 10.1101/lm.038844.115] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 05/05/2015] [Indexed: 11/24/2022]
Abstract
Memories that last a lifetime are thought to be stored, at least in part, as persistent enhancement of the strength of particular synapses. The synaptic mechanism of these persistent changes, late long-term potentiation (L-LTP), depends on the state and number of specific synaptic proteins. Synaptic proteins, however, have limited dwell times due to molecular turnover and diffusion, leading to a fundamental question: how can this transient molecular machinery store memories lasting a lifetime? Because the persistent changes in efficacy are synapse-specific, the underlying molecular mechanisms must to a degree reside locally in synapses. Extensive experimental evidence points to atypical protein kinase C (aPKC) isoforms as key components involved in memory maintenance. Furthermore, it is evident that establishing long-term memory requires new protein synthesis. However, a comprehensive model has not been developed describing how these components work to preserve synaptic efficacies over time. We propose a molecular model that can account for key empirical properties of L-LTP, including its protein synthesis dependence, dependence on aPKCs, and synapse-specificity. Simulations and empirical data suggest that either of the two aPKC subtypes in hippocampal neurons, PKMζ and PKCι/λ, can maintain L-LTP, making the system more robust. Given genetic compensation at the level of synthesis of these PKC subtypes as in knockout mice, this system is able to maintain L-LTP and memory when one of the pathways is eliminated.
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Affiliation(s)
- Sajiya J Jalil
- Department of Neurobiology and Anatomy, The University of Texas Medical School at Houston, Houston, Texas 77030, USA
| | - Todd Charlton Sacktor
- Department of Physiology, Pharmacology, Anesthesiology, and Neurology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Harel Z Shouval
- Department of Neurobiology and Anatomy, The University of Texas Medical School at Houston, Houston, Texas 77030, USA
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23
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Siddiqi S, Mansbach CM. Dietary and biliary phosphatidylcholine activates PKCζ in rat intestine. J Lipid Res 2015; 56:859-70. [PMID: 25713101 DOI: 10.1194/jlr.m056051] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Chylomicron output by the intestine is proportional to intestinal phosphatidylcholine (PC) delivery. Using five different variations of PC delivery to the intestine, we found that lyso-phosphatidylcholine (lyso-PC), the absorbed form of PC, concentrations in the cytosol (0 to 0.45 nM) were proportional to the input rate. The activity of protein kinase C (PKC)ζ, which controls prechylomicron output rate by the endoplasmic reticulum (ER), correlated with the lyso-PC concentration suggesting that it may be a PKCζ activator. Using recombinant PKCζ, the Km for lyso-PC activation was 1.49 nM and the Vmax 1.12 nM, more than the maximal lyso-PC concentration in cytosol, 0.45 nM. Among the phospholipids and their lyso derivatives, lyso-PC was the most potent activator of PKCζ and the only one whose cytosolic concentration suggested that it could be a physiological activator because other phospholipid concentrations were negligible. PKCζ was on the surface of the dietary fatty acid transport vesicle, the caveolin-1-containing endocytic vesicle. Once activated, PKCζ, eluted off the vesicle. A conformational change in PKCζ on activation was suggested by limited proteolysis. We conclude that PKCζ on activation changes its conformation resulting in elution from its vesicle. The downstream effect of dietary PC is to activate PKCζ, resulting in greater chylomicron output by the ER.
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Affiliation(s)
- Shahzad Siddiqi
- Division of Gastroenterology, The University of Tennessee Health Science Center, Memphis, TN
| | - Charles M Mansbach
- Division of Gastroenterology, The University of Tennessee Health Science Center, Memphis, TN Veterans Affairs Medical Center, Memphis, TN
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24
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O’Neill C, Li Y, Jin X. Survival Signalling in the Preimplantation Embryo. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 843:129-49. [DOI: 10.1007/978-1-4939-2480-6_5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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25
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Ivey RA, Sajan MP, Farese RV. Requirements for pseudosubstrate arginine residues during autoinhibition and phosphatidylinositol 3,4,5-(PO₄)₃-dependent activation of atypical PKC. J Biol Chem 2014; 289:25021-30. [PMID: 25035426 PMCID: PMC4155669 DOI: 10.1074/jbc.m114.565671] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 07/03/2014] [Indexed: 12/21/2022] Open
Abstract
Atypical PKC (aPKC) isoforms are activated by the phosphatidylinositol 3-kinase product phosphatidylinositol 3,4,5-(PO4)3 (PIP3). How PIP3 activates aPKC is unknown. Although Akt activation involves PIP3 binding to basic residues in the Akt pleckstrin homology domain, aPKCs lack this domain. Here we examined the role of basic arginine residues common to aPKC pseudosubstrate sequences. Replacement of all five (or certain) arginine residues in the pseudosubstrate sequence of PKC-ι by site-directed mutagenesis led to constitutive activation and unresponsiveness to PIP3 in vitro or insulin in vivo. However, with the addition of the exogenous arginine-containing pseudosubstrate tridecapeptide to inhibit this constitutively active PKC-ι, PIP3-activating effects were restored. A similar restoration of responsiveness to PIP3 was seen when exogenous pseudosubstrate was used to inhibit mouse liver PKC-λ/ζ maximally activated by insulin or ceramide and a truncated, constitutively active PKC-ζ mutant lacking all regulatory domain elements and containing "activating" glutamate residues at loop and autophosphorylation sites (Δ1-247/T410E/T560E-PKC-ζ). NMR studies suggest that PIP3 binds directly to the pseudosubstrate. The ability of PIP3 to counteract the inhibitory effects of the exogenous pseudosubstrate suggests that basic residues in the pseudosubstrate sequence are required for maintaining aPKCs in an inactive state and are targeted by PIP3 for displacement from the substrate-binding site during kinase activation.
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Affiliation(s)
- Robert A Ivey
- From the Medical and Research Services, James A. Haley Veterans Medical Center, Tampa, Florida 33612 and
| | - Mini P Sajan
- From the Medical and Research Services, James A. Haley Veterans Medical Center, Tampa, Florida 33612 and the Division of Endocrinology and Metabolism, Department of Internal Medicine, University of South Florida College of Medicine, Tampa, Florida 33612
| | - Robert V Farese
- From the Medical and Research Services, James A. Haley Veterans Medical Center, Tampa, Florida 33612 and the Division of Endocrinology and Metabolism, Department of Internal Medicine, University of South Florida College of Medicine, Tampa, Florida 33612
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26
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PTEN phosphatase-independent maintenance of glandular morphology in a predictive colorectal cancer model system. Neoplasia 2014; 15:1218-30. [PMID: 24348097 DOI: 10.1593/neo.121516] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 10/08/2013] [Accepted: 10/11/2013] [Indexed: 02/06/2023] Open
Abstract
Organotypic models may provide mechanistic insight into colorectal cancer (CRC) morphology. Three-dimensional (3D) colorectal gland formation is regulated by phosphatase and tensin homologue deleted on chromosome 10 (PTEN) coupling of cell division cycle 42 (cdc42) to atypical protein kinase C (aPKC). This study investigated PTEN phosphatase-dependent and phosphatase-independent morphogenic functions in 3D models and assessed translational relevance in human studies. Isogenic PTEN-expressing or PTEN-deficient 3D colorectal cultures were used. In translational studies, apical aPKC activity readout was assessed against apical membrane (AM) orientation and gland morphology in 3D models and human CRC. We found that catalytically active or inactive PTEN constructs containing an intact C2 domain enhanced cdc42 activity, whereas mutants of the C2 domain calcium binding region 3 membrane-binding loop (M-CBR3) were ineffective. The isolated PTEN C2 domain (C2) accumulated in membrane fractions, but C2 M-CBR3 remained in cytosol. Transfection of C2 but not C2 M-CBR3 rescued defective AM orientation and 3D morphogenesis of PTEN-deficient Caco-2 cultures. The signal intensity of apical phospho-aPKC correlated with that of Na(+)/H(+) exchanger regulatory factor-1 (NHERF-1) in the 3D model. Apical NHERF-1 intensity thus provided readout of apical aPKC activity and associated with glandular morphology in the model system and human colon. Low apical NHERF-1 intensity in CRC associated with disruption of glandular architecture, high cancer grade, and metastatic dissemination. We conclude that the membrane-binding function of the catalytically inert PTEN C2 domain influences cdc42/aPKC-dependent AM dynamics and gland formation in a highly relevant 3D CRC morphogenesis model system.
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27
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Kusne Y, Carrera-Silva EA, Perry AS, Rushing EJ, Mandell EK, Dietrich JD, Errasti AE, Gibbs D, Berens ME, Loftus JC, Hulme C, Yang W, Lu Z, Aldape K, Sanai N, Rothlin CV, Ghosh S. Targeting aPKC disables oncogenic signaling by both the EGFR and the proinflammatory cytokine TNFα in glioblastoma. Sci Signal 2014; 7:ra75. [PMID: 25118327 PMCID: PMC4486020 DOI: 10.1126/scisignal.2005196] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Grade IV glioblastoma is characterized by increased kinase activity of epidermal growth factor receptor (EGFR); however, EGFR kinase inhibitors have failed to improve survival in individuals with this cancer because resistance to these drugs often develops. We showed that tumor necrosis factor-α (TNFα) produced in the glioblastoma microenvironment activated atypical protein kinase C (aPKC), thereby producing resistance to EGFR kinase inhibitors. Additionally, we identified that aPKC was required both for paracrine TNFα-dependent activation of the transcription factor nuclear factor κB (NF-κB) and for tumor cell-intrinsic receptor tyrosine kinase signaling. Targeting aPKC decreased tumor growth in mouse models of glioblastoma, including models of EGFR kinase inhibitor-resistant glioblastoma. Furthermore, aPKC abundance and activity were increased in human glioblastoma tumor cells, and high aPKC abundance correlated with poor prognosis. Thus, targeting aPKC might provide an improved molecular approach for glioblastoma therapy.
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Affiliation(s)
- Yael Kusne
- Neuroscience Graduate Program, Arizona State University, Phoenix, AZ 85287, USA
- Barrow Brain Tumor Research Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA
| | | | - Anthony S. Perry
- Department of Pathology, Banner MD Anderson Cancer Center, Gilbert, AZ 85234, USA
| | | | - Edward K. Mandell
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06511, USA
| | | | - Andrea E. Errasti
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Daniel Gibbs
- Department of Neurosciences, University of California, San Diego, San Diego, CA 92093, USA
| | - Michael E. Berens
- Translational Genomics Research Institute (TGen), Phoenix, AZ 85004, USA
| | | | | | - Weiwei Yang
- MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Zhimin Lu
- MD Anderson Cancer Center, Houston, TX 77030, USA
| | | | - Nader Sanai
- Neuroscience Graduate Program, Arizona State University, Phoenix, AZ 85287, USA
- Barrow Brain Tumor Research Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA
| | - Carla V. Rothlin
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Sourav Ghosh
- Neuroscience Graduate Program, Arizona State University, Phoenix, AZ 85287, USA
- Barrow Brain Tumor Research Center, Barrow Neurological Institute, Phoenix, AZ 85013, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06511, USA
- Translational Genomics Research Institute (TGen), Phoenix, AZ 85004, USA
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28
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Howell KK, Monk BR, Carmack SA, Mrowczynski OD, Clark RE, Anagnostaras SG. Inhibition of PKC disrupts addiction-related memory. Front Behav Neurosci 2014; 8:70. [PMID: 24639635 PMCID: PMC3945752 DOI: 10.3389/fnbeh.2014.00070] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 02/19/2014] [Indexed: 01/20/2023] Open
Abstract
The atypical PKC isoforms, PKMζ and PKCλ have been proposed as integral substrates of long-term memory (LTM). Inhibition of these isoforms has recently been demonstrated to be sufficient for impairing the expression and maintenance of long-term potentiation. Additionally, the pseudosubstrate inhibitor, zeta inhibitory peptide (ZIP), which effectively blocks PKMζ and PKCλ, has previously been shown to disrupt associative memory; very little is known about its effects on pathological nonassociative forms of memory related to addiction. The neural and molecular substrates of memory and addiction have recently been argued to overlap. Here, we used ZIP to disrupt PKMζ and PKCλ activity to examine their role in cocaine sensitization, a nonassociative, addiction-related memory argued to underlie the transition from casual to pathological drug use. We examined the effects of both continuous and acute administration of ZIP. Even a single application of ZIP blocked the development of sensitization; sustained inhibition using osmotic pumps produced an almost complete blockade of sensitization. Further, a single application of ZIP was shown to reduce membrane-bound AMPAR expression. These results demonstrate a novel, critical role for the atypical PKC isoforms in nonassociative memory and cocaine addiction.
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Affiliation(s)
- Kristin K Howell
- Molecular Cognition Laboratory, Department of Psychology, University of California San Diego, La Jolla, CA, USA
| | - Bradley R Monk
- Molecular Cognition Laboratory, Department of Psychology, University of California San Diego, La Jolla, CA, USA
| | - Stephanie A Carmack
- Molecular Cognition Laboratory, Department of Psychology, University of California San Diego, La Jolla, CA, USA
| | - Oliver D Mrowczynski
- Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | - Robert E Clark
- Veterans Affairs Medical Center San Diego, CA, USA ; Department of Psychiatry, University of California San Diego, La Jolla, CA, USA
| | - Stephan G Anagnostaras
- Molecular Cognition Laboratory, Department of Psychology, University of California San Diego, La Jolla, CA, USA ; Program in Neurosciences, University of California San Diego, La Jolla, CA, USA
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29
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Parker PJ, Justilien V, Riou P, Linch M, Fields AP. Atypical protein kinase Cι as a human oncogene and therapeutic target. Biochem Pharmacol 2014; 88:1-11. [PMID: 24231509 PMCID: PMC3944347 DOI: 10.1016/j.bcp.2013.10.023] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 10/30/2013] [Indexed: 11/16/2022]
Abstract
Protein kinase inhibitors represent a major class of targeted therapeutics that has made a positive impact on treatment of cancer and other disease indications. Among the promising kinase targets for further therapeutic development are members of the Protein Kinase C (PKC) family. The PKCs are central components of many signaling pathways that regulate diverse cellular functions including proliferation, cell cycle, differentiation, survival, cell migration, and polarity. Genetic manipulation of individual PKC isozymes has demonstrated that they often fulfill distinct, nonredundant cellular functions. Participation of PKC members in different intracellular signaling pathways reflects responses to varying extracellular stimuli, intracellular localization, tissue distribution, phosphorylation status, and intermolecular interactions. PKC activity, localization, phosphorylation, and/or expression are often altered in human tumors, and PKC isozymes have been implicated in various aspects of transformation, including uncontrolled proliferation, migration, invasion, metastasis, angiogenesis, and resistance to apoptosis. Despite the strong relationship between PKC isozymes and cancer, to date only atypical PKCiota has been shown to function as a bona fide oncogene, and as such is a particularly attractive therapeutic target for cancer treatment. In this review, we discuss the role of PKCiota in transformation and describe mechanism-based approaches to therapeutically target oncogenic PKCiota signaling in cancer.
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Affiliation(s)
- Peter J Parker
- London Research Institute, Lincoln's Inn Fields, London WC2A 3LY, UK; King's College London, Guy's Campus, London, UK
| | - Verline Justilien
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, 45400 San Pablo Road, Jacksonville, FL 32224, USA
| | - Philippe Riou
- London Research Institute, Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Mark Linch
- London Research Institute, Lincoln's Inn Fields, London WC2A 3LY, UK; Royal Marsden Hospital, Fulham Road, London, UK
| | - Alan P Fields
- Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, 45400 San Pablo Road, Jacksonville, FL 32224, USA.
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30
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Linch M, Sanz-Garcia M, Rosse C, Riou P, Peel N, Madsen CD, Sahai E, Downward J, Khwaja A, Dillon C, Roffey J, Cameron AJ, Parker PJ. Regulation of polarized morphogenesis by protein kinase C iota in oncogenic epithelial spheroids. Carcinogenesis 2014; 35:396-406. [PMID: 24072773 PMCID: PMC3908745 DOI: 10.1093/carcin/bgt313] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 08/07/2013] [Accepted: 08/24/2013] [Indexed: 12/20/2022] Open
Abstract
Protein kinase C iota (PKCι), a serine/threonine kinase required for cell polarity, proliferation and migration, is commonly up- or downregulated in cancer. PKCι is a human oncogene but whether this is related to its role in cell polarity and what repertoire of oncogenes acts in concert with PKCι is not known. We developed a panel of candidate oncogene expressing Madin-Darby canine kidney (MDCK) cells and demonstrated that H-Ras, ErbB2 and phosphatidylinositol 3-kinase transformation led to non-polar spheroid morphogenesis (dysplasia), whereas MDCK spheroids expressing c-Raf or v-Src were largely polarized. We show that small interfering RNA (siRNA)-targeting PKCι decreased the size of all spheroids tested and partially reversed the aberrant polarity phenotype in H-Ras and ErbB2 spheroids only. This indicates distinct requirements for PKCι and moreover that different thresholds of PKCι activity are required for these phenotypes. By manipulating PKCι function using mutant constructs, siRNA depletion or chemical inhibition, we have demonstrated that PKCι is required for polarization of parental MDCK epithelial cysts in a 3D matrix and that there is a threshold of PKCι activity above and below which, disorganized epithelial morphogenesis results. Furthermore, treatment with a novel PKCι inhibitor, CRT0066854, was able to restore polarized morphogenesis in the dysplastic H-Ras spheroids. These results show that tightly regulated PKCι is required for normal-polarized morphogenesis in mammalian cells and that H-Ras and ErbB2 cooperate with PKCι for loss of polarization and dysplasia. The identification of a PKCι inhibitor that can restore polarized morphogenesis has implications for the treatment of Ras and ErbB2 driven malignancies.
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Affiliation(s)
- Mark Linch
- Department of Protein Phosphorylation, Cancer Research UK London Research Institute, London WC2A 3LY, UK
- Sarcoma Unit, Royal Marsden Hospital, London SW3 6JJ, UK
| | - Marta Sanz-Garcia
- Department of Protein Phosphorylation, Cancer Research UK London Research Institute, London WC2A 3LY, UK
| | - Carine Rosse
- Department of Protein Phosphorylation, Cancer Research UK London Research Institute, London WC2A 3LY, UK
| | - Philippe Riou
- Department of Protein Phosphorylation, Cancer Research UK London Research Institute, London WC2A 3LY, UK
| | - Nick Peel
- Department of Protein Phosphorylation, Cancer Research UK London Research Institute, London WC2A 3LY, UK
| | | | | | - Julian Downward
- Department of Signal Transduction Laboratories, Cancer Research UK London Research Institute, London WC2A 3LY, UK
| | - Asim Khwaja
- Department of Haematology, UCL Cancer Institute, University College London, London WC1E 6BT, UK
| | - Christian Dillon
- Cancer Research Technology Discovery Laboratories, Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK and
| | - Jon Roffey
- Cancer Research Technology Discovery Laboratories, Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK and
| | - Angus J.M. Cameron
- Department of Protein Phosphorylation, Cancer Research UK London Research Institute, London WC2A 3LY, UK
| | - Peter J. Parker
- Department of Protein Phosphorylation, Cancer Research UK London Research Institute, London WC2A 3LY, UK
- Division of Cancer Studies, King’s College London, London SE1 1UL, UK
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31
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Li X, Gao T. mTORC2 phosphorylates protein kinase Cζ to regulate its stability and activity. EMBO Rep 2013; 15:191-8. [PMID: 24375676 DOI: 10.1002/embr.201338119] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Protein kinase Cζ (PKCζ) is phosphorylated at the activation loop and the turn motif (TM). However, the TM kinase and functional relevance of TM phosphorylation remain largely unknown. We demonstrate that PKCζ TM is phosphorylated directly by the mTORC2 complex, and this phosphorylation is required for maintaining PKCζ kinase activity and stability. Functionally, mTORC2 regulates the activity of Rho family of GTPases, and therefore the organization of the actin cytoskeleton, through the control of PKCζ activity. Taken together, our findings identify PKCζ as a novel substrate and downstream effector of mTORC2 signaling.
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Affiliation(s)
- Xin Li
- Markey Cancer Center, University of Kentucky, Lexington, KY, USA
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32
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Kwapis JL, Helmstetter FJ. Does PKM(zeta) maintain memory? Brain Res Bull 2013; 105:36-45. [PMID: 24076105 DOI: 10.1016/j.brainresbull.2013.09.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 09/16/2013] [Accepted: 09/19/2013] [Indexed: 11/30/2022]
Abstract
Work on the long-term stability of memory has identified a potentially critical role for protein kinase Mzeta (PKMζ) in maintaining established memory. PKMζ, an autonomously active isoform of PKC, is hypothesized to sustain those changes that occurred during memory formation in order to preserve the memory engram over time. Initial studies investigating the role of PKMζ were largely successful in demonstrating a role for the kinase in memory maintenance; disrupting PKMζ activity with ζ-inhibitory peptide (ZIP) was successful in disrupting a variety of established associations in a number of key brain regions. More recent work, however, has questioned both the role of PKMζ in memory maintenance and the effectiveness of ZIP as a specific inhibitor of PKMζ activity. Here, we outline the research both for and against the idea that PKMζ is a memory maintenance mechanism and discuss how these two lines of research can be reconciled. We conclude by proposing a number of studies that would help to clarify the role of PKMζ in memory and define other mechanisms the brain may use to maintain memory.
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Affiliation(s)
- Janine L Kwapis
- Department of Psychology, University of Wisconsin-Milwaukee, 2441 E. Hartford Ave., Milwaukee, WI 53211, USA
| | - Fred J Helmstetter
- Department of Psychology, University of Wisconsin-Milwaukee, 2441 E. Hartford Ave., Milwaukee, WI 53211, USA.
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33
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Nijhout HF, Callier V. A new mathematical approach for qualitative modeling of the insulin-TOR-MAPK network. Front Physiol 2013; 4:245. [PMID: 24062690 PMCID: PMC3771213 DOI: 10.3389/fphys.2013.00245] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 08/20/2013] [Indexed: 12/20/2022] Open
Abstract
In this paper we develop a novel mathematical model of the insulin-TOR-MAPK signaling network that controls growth. Most data on the properties of the insulin and MAPK signaling networks are static and the responses to experimental interventions, such as knockouts, overexpression, and hormonal input are typically reported as scaled quantities. The modeling paradigm we develop here uses scaled variables and is ideally suited to simulate systems in which much of the available data are scaled. Our mathematical representation of signaling networks provides a way to reconcile theory and experiments, thus leading to a better understanding of the properties and function of these signaling networks. We test the performance of the model against a broad diversity of experimental data. The model correctly reproduces experimental insulin dose-response relationships. We study the interaction between insulin and MAPK signaling in the control of protein synthesis, and the interactions between amino acids, insulin and TOR signaling. We study the effects of variation in FOXO expression on protein synthesis and glucose transport capacity, and show that a FOXO knockout can partially rescue protein synthesis capacity of an insulin receptor (INR) knockout. We conclude that the modeling paradigm we develop provides a simple tool to investigate the qualitative properties of signaling networks.
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Atypical protein kinase C and Par3 are required for proteoglycan-induced axon growth inhibition. J Neurosci 2013; 33:2541-54. [PMID: 23392682 DOI: 10.1523/jneurosci.3154-12.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
When the CNS is injured, damaged axons do not regenerate. This failure is due in part to the growth-inhibitory environment that forms at the injury site. Myelin-associated molecules, repulsive axon guidance molecules, and extracellular matrix molecules including chondroitin sulfate proteoglycans (CSPGs) found within the glial scar inhibit axon regeneration but the intracellular signaling mechanisms triggered by these diverse molecules remain largely unknown. Here we provide biochemical and functional evidence that atypical protein kinase C (PKCζ) and polarity (Par) complex proteins mediate axon growth inhibition. Treatment of postnatal rat neurons in vitro with the NG2 CSPG, a major component of the glial scar, activates PKCζ, and this activation is both necessary and sufficient to inhibit axonal growth. NG2 treatment also activates Cdc42, increases the association of Par6 with PKCζ, and leads to a Par3-dependent activation of Rac1. Transfection of neurons with kinase-dead forms of PKCζ, dominant-negative forms of Cdc42, or mutant forms of Par6 that do not bind to Cdc42 prevent NG2-induced growth inhibition. Similarly, transfection with either a phosphomutant Par3 (S824A) or dominant-negative Rac1 prevent inhibition, whereas expression of constitutively active Rac1 inhibits axon growth on control surfaces. These results suggest a model in which NG2 binding to neurons activates PKCζ and modifies Par complex function. They also identify the Par complex as a novel therapeutic target for promoting axon regeneration after CNS injury.
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PKCλ is critical in AMPA receptor phosphorylation and synaptic incorporation during LTP. EMBO J 2013; 32:1365-80. [PMID: 23511975 DOI: 10.1038/emboj.2013.60] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 02/13/2013] [Indexed: 01/26/2023] Open
Abstract
Direct phosphorylation of GluA1 by PKC controls α-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) receptor (AMPAR) incorporation into active synapses during long-term potentiation (LTP). Numerous signalling molecules that involved in AMPAR incorporation have been identified, but the specific PKC isoform(s) participating in GluA1 phosphorylation and the molecule triggering PKC activation remain largely unknown. Here, we report that the atypical isoform of PKC, PKCλ, is a critical molecule that acts downstream of phosphatidylinositol 3-kinase (PI3K) and is essential for LTP expression. PKCλ activation is required for both GluA1 phosphorylation and increased surface expression of AMPARs during LTP. Moreover, p62 interacts with both PKCλ and GluA1 during LTP and may serve as a scaffolding protein to place PKCλ in close proximity to facilitate GluA1 phosphorylation by PKCλ. Thus, we conclude that PKCλ is the critical signalling molecule responsible for GluA1-containing AMPAR phosphorylation and synaptic incorporation at activated synapses during LTP expression.
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36
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Bathgate RAD, Halls ML, van der Westhuizen ET, Callander GE, Kocan M, Summers RJ. Relaxin family peptides and their receptors. Physiol Rev 2013; 93:405-80. [PMID: 23303914 DOI: 10.1152/physrev.00001.2012] [Citation(s) in RCA: 353] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
There are seven relaxin family peptides that are all structurally related to insulin. Relaxin has many roles in female and male reproduction, as a neuropeptide in the central nervous system, as a vasodilator and cardiac stimulant in the cardiovascular system, and as an antifibrotic agent. Insulin-like peptide-3 (INSL3) has clearly defined specialist roles in male and female reproduction, relaxin-3 is primarily a neuropeptide involved in stress and metabolic control, and INSL5 is widely distributed particularly in the gastrointestinal tract. Although they are structurally related to insulin, the relaxin family peptides produce their physiological effects by activating a group of four G protein-coupled receptors (GPCRs), relaxin family peptide receptors 1-4 (RXFP1-4). Relaxin and INSL3 are the cognate ligands for RXFP1 and RXFP2, respectively, that are leucine-rich repeat containing GPCRs. RXFP1 activates a wide spectrum of signaling pathways to generate second messengers that include cAMP and nitric oxide, whereas RXFP2 activates a subset of these pathways. Relaxin-3 and INSL5 are the cognate ligands for RXFP3 and RXFP4 that are closely related to small peptide receptors that when activated inhibit cAMP production and activate MAP kinases. Although there are still many unanswered questions regarding the mode of action of relaxin family peptides, it is clear that they have important physiological roles that could be exploited for therapeutic benefit.
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Affiliation(s)
- R A D Bathgate
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences & Department of Pharmacology, Monash University, Victoria, Australia
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Tripp ML, Darland G, Konda VR, Pacioretty LM, Chang JL, Bland JS, Babish JG. Optimized mixture of hops rho iso-alpha acids-rich extract and acacia proanthocyanidins-rich extract reduces insulin resistance in 3T3-L1 adipocytes and improves glucose and insulin control in db/db mice. Nutr Res Pract 2012. [PMID: 23198019 PMCID: PMC3506871 DOI: 10.4162/nrp.2012.6.5.405] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Rho iso-alpha acids-rich extract (RIAA) from Humulus lupulus (hops) and proanthocyanidins-rich extracts (PAC) from Acacia nilotica exert anti-inflammatory and anti-diabetic activity in vitro and in vivo. We hypothesized that a combination of these two extracts would exert enhanced effects in vitro on inflammatory markers and insulin signaling, and on nonfasting glucose and insulin in db/db mice. Over 49 tested combinations, RIAA:PAC at 5:1 (6.25 µg/mL) exhibited the greatest reductions in TNFα-stimulated lipolysis and IL-6 release in 3T3-L1 adipocytes, comparable to 5 µg/mL troglitazone. Pretreatment of 3T3-L1 adipocytes with this combination (5 µg/mL) also led to a 3-fold increase in insulin-stimulated glucose uptake that was comparable to 5 µg/mL pioglitazone or 901 µg/mL aspirin. Finally, db/db mice fed with RIAA:PAC at 5:1 (100 mg/kg) for 7 days resulted in 22% decrease in nonfasting glucose and 19% decrease in insulin that was comparable to 0.5 mg/kg rosiglitazone and better than 100 mg/kg metformin. RIAA:PAC mixture may have the potential to be an alternative when conventional therapy is undesirable or ineffective, and future research exploring its long-term clinical application is warranted.
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Affiliation(s)
- Matthew L Tripp
- MetaProteomics LLC, 9770 44 Ave. NW, Ste 100, Gig Harbor, WA 98332, USA
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Beeson M, Sajan MP, Daspet JG, Luna V, Dizon M, Grebenev D, Powe JL, Lucidi S, Miura A, Kanoh Y, Bandyopadhyay G, Standaert ML, Yeko TR, Farese RV. Defective Activation of Protein Kinase C-z in Muscle by Insulin and Phosphatidylinositol-3,4,5,-(PO(4))(3) in Obesity and Polycystic Ovary Syndrome. Metab Syndr Relat Disord 2012; 2:49-56. [PMID: 18370676 DOI: 10.1089/met.2004.2.49] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Insulin resistance occurs frequently in metabolic syndrome components, obesity, and the polycystic ovary syndrome, and is partly due to impaired glucose transport into skeletal muscle, but underlying mechanisms are uncertain. Atypical protein kinase C and protein kinase B, operating downstream of phosphatidylinositol 3-kinase, mediate insulin effects on glucose transport, but their importance in these syndromes is poorly understood. Presently, we examined these signaling factors in muscle biopsies obtained during euglycemic/hyperinsulinemic clamp studies. In lean subjects, insulin provoked approximately twofold increases in muscle atypical protein kinase C activity. In obese subjects and obese subjects who had evidence of the polycystic ovary syndrome, insulin-stimulated glucose disposal and atypical protein kinase C activation were diminished, whereas activation of insulin receptor substrate-1-dependent phosphatidylinositol 3-kinase and protein kinase B trended lower, but not significantly. Interestingly, direct activation of atypical protein kinase C by phosphatidylinositol-3,4,5-(PO(4))(3), the lipid product of phosphatidylinositol 3-kinase, was readily apparent in immunoprecipitates prepared from muscles of lean subjects, but to a lesser degree or poorly if at all in subjects who were obese or had the obesity/polycystic ovary syndrome. Our findings suggest that activation of muscle atypical protein kinase C by insulin and phosphatidylinositol-3,4,5-(PO(4))(3) is defective and may contribute to skeletal muscle insulin resistance in women who are obese, or have obesity associated with the polycystic ovary syndrome.
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Affiliation(s)
- Mary Beeson
- Research Service, James A. Haley Veterans Hospital, and Division of Endocrinology and Metabolism, Department of Internal Medicine
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Abstract
Background: Previously, using gene-knockdown techniques together with genome expression array analysis, we showed the gene protein Kinase C (PKC)-zeta (PRKCZ) to mediate the malignant phenotype of human prostate cancer. However, according to NCBI, the gene has undergone several major iterations. Therefore, to understand the relationship between its structure and biological activities, we have analysed its expressed sequence in prostate cancer cell lines and tissues. Methods: Transcriptome-walking and targeted PCR were used to sequence the mRNA transcribed from PRKCZ. Hydropathy analysis was employed to analyse the hypothetical protein sequence subsequently translated and to identify an appropriate epitope to generate a specific monoclonal antibody. Results: A novel sequence was identified within the 3′-terminal domain of human PRKCZ that, in prostate cancer cell lines and tissues, is expressed during transcription and thereafter translated into protein (designated PKC-ζ-PrC) independent of conventional PKC-ζ-a. The monoclonal antibody detected expression of this 96 kD protein only within malignant prostatic epithelium. Interpretation: Transcription and translation of this gene sequence, including previous intronic sequences, generates a novel specific biomarker of human prostate cancer. The presence of catalytic domains characteristic of classic PKC-β and atypical PKC-ι within PKC-ζ-PrC provides a potential mechanism for this PRKCZ variant to modulate the malignant prostatic phenotype out-with normal cell-regulatory control.
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Abstract
Insulin acts throughout the body to reduce circulating energy and to increase energy storage. Within the brain, insulin produces a net catabolic effect by reducing food intake and increasing energy expenditure; this is evidenced by the hypophagia and increased brown adipose tissue sympathetic nerve activity induced by central insulin infusion. Reducing the activity of the brain insulin system via administration of insulin antibodies, receptor antisense treatment, or receptor knockdown results in hyperphagia and increased adiposity. However, despite decades of research into the role of central insulin in food intake, many questions remain to be answered, including the underlying mechanism of action.
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Affiliation(s)
- Denovan P Begg
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, OH 45237, USA
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41
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Rangel-Salazar R, Wickström-Lindholm M, Aguilar-Salinas CA, Alvarado-Caudillo Y, Døssing KBV, Esteller M, Labourier E, Lund G, Nielsen FC, Rodríguez-Ríos D, Solís-Martínez MO, Wrobel K, Wrobel K, Zaina S. Human native lipoprotein-induced de novo DNA methylation is associated with repression of inflammatory genes in THP-1 macrophages. BMC Genomics 2011; 12:582. [PMID: 22118513 PMCID: PMC3247910 DOI: 10.1186/1471-2164-12-582] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 11/25/2011] [Indexed: 01/31/2023] Open
Abstract
Background We previously showed that a VLDL- and LDL-rich mix of human native lipoproteins induces a set of repressive epigenetic marks, i.e. de novo DNA methylation, histone 4 hypoacetylation and histone 4 lysine 20 (H4K20) hypermethylation in THP-1 macrophages. Here, we: 1) ask what gene expression changes accompany these epigenetic responses; 2) test the involvement of candidate factors mediating the latter. We exploited genome expression arrays to identify target genes for lipoprotein-induced silencing, in addition to RNAi and expression studies to test the involvement of candidate mediating factors. The study was conducted in human THP-1 macrophages. Results Native lipoprotein-induced de novo DNA methylation was associated with a general repression of various critical genes for macrophage function, including pro-inflammatory genes. Lipoproteins showed differential effects on epigenetic marks, as de novo DNA methylation was induced by VLDL and to a lesser extent by LDL, but not by HDL, and VLDL induced H4K20 hypermethylation, while HDL caused H4 deacetylation. The analysis of candidate factors mediating VLDL-induced DNA hypermethylation revealed that this response was: 1) surprisingly, mediated exclusively by the canonical maintenance DNA methyltransferase DNMT1, and 2) independent of the Dicer/micro-RNA pathway. Conclusions Our work provides novel insights into epigenetic gene regulation by native lipoproteins. Furthermore, we provide an example of DNMT1 acting as a de novo DNA methyltransferase independently of canonical de novo enzymes, and show proof of principle that de novo DNA methylation can occur independently of a functional Dicer/micro-RNA pathway in mammals.
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Jiang X, Tian Q, Wang Y, Zhou XW, Xie JZ, Wang JZ, Zhu LQ. Acetyl-L-Carnitine ameliorates spatial memory deficits induced by inhibition of phosphoinositol-3 kinase and protein kinase C. J Neurochem 2011; 118:864-78. [DOI: 10.1111/j.1471-4159.2011.07355.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
The endocytic pathway is involved in activation and inhibition of cellular signaling. Thus, defining the regulatory mechanisms that link endocytosis and cellular signaling is of interest. An emerging link between these processes is a family of proteins called intersectins (ITSNs). These multidomain proteins serve as scaffolds in the assembly of endocytic vesicles and also regulate components of various signaling pathways, including kinases, guanosine triphosphatases, and ubiquitin ligases. This review summarizes research on the role of ITSNs in regulating both endocytic and signal transduction pathways, discusses the link between ITSNs and human disease, and highlights future directions in the study of ITSNs.
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Affiliation(s)
- John P O'Bryan
- Department of Pharmacology, University of Illinois at Chicago, Chicago, IL 60612, USA.
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Qin Y, Meisen WH, Hao Y, Macara IG. Tuba, a Cdc42 GEF, is required for polarized spindle orientation during epithelial cyst formation. ACTA ACUST UNITED AC 2010; 189:661-9. [PMID: 20479467 PMCID: PMC2872902 DOI: 10.1083/jcb.201002097] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
An RNAi screen picks Tuba out of the GTPase exchange factor (GEF) orchestra as a regulator of cell polarity in epithelial morphogenesis. (See also a companion paper from Rodriguez-Fraticelli et al., in this issue.) The Cdc42 guanosine triphosphatase is essential for cell polarization in several organisms and in vitro for the organization of polarized epithelial cysts. A long-standing question concerns the identity of the guanine nucleotide exchange factor (GEF) that controls this process. Using Madin–Darby canine kidney cells grown in Matrigel, we screened 70 GEFs by RNA interference. Of these, six positives were identified that caused a multilumen phenotype, including Tuba, a Cdc42-specific GEF localized below the apical cortex. Loss of Tuba abolishes Cdc42 enrichment at the apical cortex. Normal lumen formation is rescued by human Tuba or active Cdc42 but not by a GEF-negative Tuba mutant. Silencing Cdc42 causes a similar phenotype, including multilumen formation and reduced atypical protein kinase C (aPKC) activity. Lumen disorganization after depletion of Tuba or Cdc42 or inhibition of aPKC is caused by defective spindle orientation. Together, our findings implicate Tuba as a key activator of the Cdc42 GTPase during epithelial ductal morphogenesis, which in turn activates apical aPKC to ensure that spindles orient parallel to the lateral plane.
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Affiliation(s)
- Yi Qin
- Center for Cell Signaling, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
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Farese RV, Sajan MP. Metabolic functions of atypical protein kinase C: "good" and "bad" as defined by nutritional status. Am J Physiol Endocrinol Metab 2010; 298:E385-94. [PMID: 19996389 PMCID: PMC3774273 DOI: 10.1152/ajpendo.00608.2009] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Atypical protein kinase C (aPKC) isoforms mediate insulin effects on glucose transport in muscle and adipose tissues and lipid synthesis in liver and support other metabolic processes, expression of enzymes needed for islet insulin secretion and hepatic glucose production/release, CNS appetite suppression, and inflammatory responses. In muscle, selective aPKC deficiency impairs glucose uptake and produces insulin resistance and hyperinsulinemia, which, by activating hepatic aPKC, provokes inordinate increases in lipid synthesis and produces typical "metabolic syndrome" features. In contrast, hepatic aPKC deficiency diminishes lipid synthesis and protects against metabolic syndrome features. Unfortunately, aPKC is deficient in muscle but paradoxically conserved in liver in obesity and type 2 diabetes mellitus; this combination is particularly problematic because it promotes lipid and carbohydrate abnormalities. Accordingly, metabolic effects of aPKCs can be "good" or "bad," depending upon nutritional status; thus, muscle glucose uptake, islet insulin secretion, hepatic glucose and lipid production/release, and adipose fat synthesis/storage would be important for survival during periods of limited food availability and therefore be "good." However, during times of food surfeit, excessive activation of hepatic aPKC, whether caused by overnutrition or impairments in extrahepatic effects of insulin, would lead to inordinate increases in hepatic lipid synthesis and metabolic syndrome features and therefore be "bad." In keeping with these ideas, the inhibition of hepatic aPKC markedly ameliorates lipid and carbohydrate abnormalities in experimental models of obesity and type 2 diabetes. We postulate that a similar approach may be useful for treating humans.
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Affiliation(s)
- Robert V Farese
- James A. Haley Veteran's Administration Medical Center, Tampa, FL 33612, USA.
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46
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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: 75] [Impact Index Per Article: 5.4] [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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Abstract
Hyperglycemia is an important factor in the development of macrovascular and microvascular complications in all diabetic patients. Several hypotheses have been postulated to explain the adverse effect of hyperglycemia on the vasculature; and one of these hypotheses is the activation of specific isoforms of protein kinase C (PKC) by diabetes. In this review, we summarize the molecular mechanisms of PKC activation and its relationship to diabetic complications. PKC activity regulates vascular permeability, contractility, extracellular matrix synthesis, hormone receptor turnover and proliferation, cell growth, angiogenesis, cytokine activation and leukocyte adhesion. All of these properties are abnormal in diabetes and are correlated with increased diacylglycerol-PKC pathway and PKCα, β1/2 and δ isoforms activation in the retina, aorta, heart and renal glomeruli.
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Affiliation(s)
- George L King
- a Professor of Medicine, Harvard Medical School, Department of Vascular Cell Biology, Senior Vice President, Research Director, Joslin Diabetes Center, 1 Joslin Place, Boston, MA 02215, USA.
| | - Net Das-Evcimen
- b Biochemistry Department, Pharmacy Faculty, Ankara University, 06100, Tandogan, Ankara, Turkey.
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Frøsig C, Richter EA. Improved insulin sensitivity after exercise: focus on insulin signaling. Obesity (Silver Spring) 2009; 17 Suppl 3:S15-20. [PMID: 19927140 DOI: 10.1038/oby.2009.383] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
After a single bout of exercise, the ability of insulin to stimulate glucose uptake is markedly improved locally in the previously active muscles. This makes exercise a potent stimulus counteracting insulin resistance characterizing type 2 diabetes (T2D). It is believed that at least part of the mechanism relates to an improved ability of insulin to stimulate translocation of glucose transporters (GLUT4) to the muscle membrane after exercise. How this is accomplished is still unclear; however, an obvious possibility is that exercise interacts with the insulin signaling pathway to GLUT4 translocation allowing for a more potent insulin response. Parallel to unraveling of the insulin signaling cascade, this has been investigated within the past 25 years. Reviewing existing studies clearly indicates that improved insulin action can occur independent of interactions with proximal insulin signaling. In contrast, more recent observations indicate that interactions exist at the distal signaling level of AS160 and atypical protein kinase C (aPKC). Although the functional interpretation is lacking, these novel observations may present a breakthrough in understanding the beneficial interplay between exercise and insulin action.
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Affiliation(s)
- Christian Frøsig
- The Copenhagen Muscle Research Centre, Molecular Physiology Group, Section of Human Physiology, Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark.
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Alpha1-AMP-activated protein kinase regulates hypoxia-induced Na,K-ATPase endocytosis via direct phosphorylation of protein kinase C zeta. Mol Cell Biol 2009; 29:3455-64. [PMID: 19380482 DOI: 10.1128/mcb.00054-09] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Hypoxia promotes Na,K-ATPase endocytosis via protein kinase C zeta (PKC zeta)-mediated phosphorylation of the Na,K-ATPase alpha subunit. Here, we report that hypoxia leads to the phosphorylation of 5'-AMP-activated protein kinase (AMPK) at Thr172 in rat alveolar epithelial cells. The overexpression of a dominant-negative AMPK alpha subunit (AMPK-DN) construct prevented the hypoxia-induced endocytosis of Na,K-ATPase. The overexpression of the reactive oxygen species (ROS) scavenger catalase prevented hypoxia-induced AMPK activation. Moreover, hypoxia failed to activate AMPK in mitochondrion-deficient rho(0)-A549 cells, suggesting that mitochondrial ROS play an essential role in hypoxia-induced AMPK activation. Hypoxia-induced PKC zeta translocation to the plasma membrane and phosphorylation at Thr410 were prevented by the pharmacological inhibition of AMPK or by the overexpression of the AMPK-DN construct. We found that AMPK alpha phosphorylates PKC zeta on residue Thr410 within the PKC zeta activation loop. Importantly, the activation of AMPK alpha was necessary for hypoxia-induced AMPK-PKC zeta binding in alveolar epithelial cells. The overexpression of T410A mutant PKC zeta prevented hypoxia-induced Na,K-ATPase endocytosis, confirming that PKC zeta Thr410 phosphorylation is essential for this process. PKC zeta activation by AMPK is isoform specific, as small interfering RNA targeting the alpha1 but not the alpha2 catalytic subunit prevented PKC zeta activation. Accordingly, we provide the first evidence that hypoxia-generated mitochondrial ROS lead to the activation of the AMPK alpha1 isoform, which binds and directly phosphorylates PKC zeta at Thr410, thereby promoting Na,K-ATPase endocytosis.
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50
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Identification of potential pathway mediation targets in Toll-like receptor signaling. PLoS Comput Biol 2009; 5:e1000292. [PMID: 19229310 PMCID: PMC2634968 DOI: 10.1371/journal.pcbi.1000292] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Accepted: 01/07/2009] [Indexed: 01/01/2023] Open
Abstract
Recent advances in reconstruction and analytical methods for signaling networks have spurred the development of large-scale models that incorporate fully functional and biologically relevant features. An extended reconstruction of the human Toll-like receptor signaling network is presented herein. This reconstruction contains an extensive complement of kinases, phosphatases, and other associated proteins that mediate the signaling cascade along with a delineation of their associated chemical reactions. A computational framework based on the methods of large-scale convex analysis was developed and applied to this network to characterize input–output relationships. The input–output relationships enabled significant modularization of the network into ten pathways. The analysis identified potential candidates for inhibitory mediation of TLR signaling with respect to their specificity and potency. Subsequently, we were able to identify eight novel inhibition targets through constraint-based modeling methods. The results of this study are expected to yield meaningful avenues for further research in the task of mediating the Toll-like receptor signaling network and its effects. The human innate immune system, as the first line of defense against pathogens, is a vital component of our survival. One component of the innate immune system is the Toll-like receptor signaling network, which is responsible for transmitting activation signals from the outside of the cell to molecular machinery inside the cell. The innate immune system must be properly balanced, as excessive activation can lead to potentially lethal septic shock. Therefore, there is much interest in developing drugs that can mediate Toll-like receptor signaling so as to alleviate effects of excess activation. We present an in silico reconstruction of the Toll-like receptor signaling network and convert it into a mathematical framework that is suitable for constraint-based modeling and analysis. This approach leads to the identification of potential candidates for drug-based mediation. In addition to identifying targets for drug mediation of the Toll-like receptor network, we also supply a network model that may be continually updated and maintained.
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