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Zhou Q, Tang S, Zhang X, Chen L. Targeting PRAS40: a novel therapeutic strategy for human diseases. J Drug Target 2021; 29:703-715. [PMID: 33504218 DOI: 10.1080/1061186x.2021.1882470] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Proline-rich Akt substrate of 40 kD (PRAS40) is not only the substrate of protein kinase B (PKB/Akt), but also the binding protein of 14-3-3 protein. PRAS40 is expressed in a variety of tissues in vivo and has multiple phosphorylation sites, which its activity is closely related to phosphorylation. Studies have shown that PRAS40 is involved in regulating cell growth, cell apoptosis, oxidative stress, autophagy and angiogenesis, as well as various of signalling pathways such as mammalian target of mammalian target rapamycin (mTOR), protein kinase B (PKB/Akt), nuclear factor kappa-B(NF-κB), proto-oncogene serine/threonine-protein kinase PIM-1(PIM1) and pyruvate kinase M2 (PKM2). The interactive roles between PRAS40 and these signal proteins were analysed by bioinformatics in this paper. Moreover, it is of great necessity for analyse the important roles of PRAS40 in some human diseases including cardiovascular disease, ischaemia-reperfusion injury, neurodegenerative disease, cancer, diabetes and other metabolic diseases. Finally, the effects of miRNA on the regulation of PRAS40 function and the occurrence and development of PRAS40-related diseases are also discussed. Overall, PRAS40 is expected to be a drug target and provide a new treatment strategy for human diseases.
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Affiliation(s)
- Qun Zhou
- Hunan Province Key Laboratory for Antibody- Based Drug and Intelligent Delivery System, School of Pharmaceutical Sciences, Hunan University of Medicine, Huaihua, China
| | - Shengsong Tang
- Hunan Province Key Laboratory for Antibody- Based Drug and Intelligent Delivery System, School of Pharmaceutical Sciences, Hunan University of Medicine, Huaihua, China
| | - Xianhui Zhang
- Orthopedics Department, Dongkou People's Hospital, Dongkou, China
| | - Linxi Chen
- Hunan Provincial Key Laboratory of Tumor Microenvironment Responsive Drug Research, Hunan Province Cooperative Innovation Center for Molecular Target, New Drug Study, Institute of Pharmacy and Pharmacology, University of South China, Hengyang, China
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2
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Zdżalik-Bielecka D, Poświata A, Kozik K, Jastrzębski K, Schink KO, Brewińska-Olchowik M, Piwocka K, Stenmark H, Miączyńska M. The GAS6-AXL signaling pathway triggers actin remodeling that drives membrane ruffling, macropinocytosis, and cancer-cell invasion. Proc Natl Acad Sci U S A 2021; 118:e2024596118. [PMID: 34244439 PMCID: PMC8285903 DOI: 10.1073/pnas.2024596118] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
AXL, a member of the TAM (TYRO3, AXL, MER) receptor tyrosine kinase family, and its ligand, GAS6, are implicated in oncogenesis and metastasis of many cancer types. However, the exact cellular processes activated by GAS6-AXL remain largely unexplored. Here, we identified an interactome of AXL and revealed its associations with proteins regulating actin dynamics. Consistently, GAS6-mediated AXL activation triggered actin remodeling manifested by peripheral membrane ruffling and circular dorsal ruffles (CDRs). This further promoted macropinocytosis that mediated the internalization of GAS6-AXL complexes and sustained survival of glioblastoma cells grown under glutamine-deprived conditions. GAS6-induced CDRs contributed to focal adhesion turnover, cell spreading, and elongation. Consequently, AXL activation by GAS6 drove invasion of cancer cells in a spheroid model. All these processes required the kinase activity of AXL, but not TYRO3, and downstream activation of PI3K and RAC1. We propose that GAS6-AXL signaling induces multiple actin-driven cytoskeletal rearrangements that contribute to cancer-cell invasion.
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Affiliation(s)
- Daria Zdżalik-Bielecka
- Laboratory of Cell Biology, International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland;
| | - Agata Poświata
- Laboratory of Cell Biology, International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
| | - Kamila Kozik
- Laboratory of Cell Biology, International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
| | - Kamil Jastrzębski
- Laboratory of Cell Biology, International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
| | - Kay Oliver Schink
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, 0379 Oslo, Norway
| | | | - Katarzyna Piwocka
- Laboratory of Cytometry, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland
| | - Harald Stenmark
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, 0379 Oslo, Norway
| | - Marta Miączyńska
- Laboratory of Cell Biology, International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland;
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3
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Benedetti F, Curreli S, Gallo RC, Zella D. Exogenous bacterial DnaK increases protein kinases activity in human cancer cell lines. J Transl Med 2021; 19:60. [PMID: 33563293 PMCID: PMC7871384 DOI: 10.1186/s12967-021-02734-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 02/01/2021] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Studies of molecular mechanisms underlying tumor cell signaling highlighted a critical role for kinases in carcinogenesis and cancer progression. To this regard, protein kinases regulates a number of critical cellular pathways by adding phosphate groups to specific substrates. For this reason, their involvement in the complex interactions between the human microbiota and cancer cells to determine therapy and tumor progression outcome is becoming increasingly relevant. Mycoplasmas are components of the normal human microbiota, and several species have also been associated to human diseases, including certain cancers. It is also important to note that Mycoplasmas and their proteins are a component of the common tumor microenvironment. In addition, several epidemiological, in vivo and in vitro studies indicate a close involvement of Mycoplasmas in cellular transformation and cancer progression. METHODS In this study, we investigate the effect of exogenous Mycoplasma DnaK on kinases activity by treating in vitro four different eukaryotic cancer cell lines, namely lung and prostate cancer, colon adenocarcinoma, and neuroblastoma. Phosphorylation of kinases and specific substrates was measured at 20 and 60 min. RESULTS Kinome analysis of our data indicates that Mycoplasma DnaK promotes the dysregulation of the activity of specific kinases and their substrates, with a known involvement in carcinogenesis and cancer progression. CONCLUSIONS Given the similarity in structure and amino acid composition of this protein with other bacterial DnaKs we provide a novel mechanism whereby components of the human microbiota and present in the tumor microenvironment are able to deregulate phosphorylation events occurring during carcinogenesis and cancer progression.
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Affiliation(s)
- Francesca Benedetti
- Institute of Human Virology and Global Virus Network Center, Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Sabrina Curreli
- Institute of Human Virology and Global Virus Network Center, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Robert C Gallo
- Institute of Human Virology and Global Virus Network Center, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Davide Zella
- Institute of Human Virology and Global Virus Network Center, Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA.
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4
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Lin J, Fang Y, Zhang M, Wang X, Li L, He M, Xue A, Zhu K, Shen Y, Li B. Phosphorylation of PRAS40 contributes to the activation of the PI3K/AKT/mTOR signaling pathway and the inhibition of autophagy following status epilepticus in rats. Exp Ther Med 2020; 20:3625-3632. [PMID: 32855714 PMCID: PMC7444373 DOI: 10.3892/etm.2020.9085] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Accepted: 06/02/2020] [Indexed: 12/30/2022] Open
Abstract
Status epilepticus (SE) is a neurological disorder associated with high morbidity and mortality rates, and is often difficult to treat. Moreover, the underlying mechanism of SE remains unknown. The lithium-pilocarpine model is a validated animal model that can reproduce the main clinical and neuropathological features of SE. In the present study, this SE model was utilized and SE was successfully established in rats, as determined by the corresponding epileptic electroencephalogram. Histology, immunohistochemistry, western blot analysis and co-immunoprecipitation were used to detect the phosphorylation (p-) of AKT substrate of 40 kDa (PRAS40), the combination of p-PRAS40 and 14-3-3 protein and the activation of the PI3K/mTOR signaling pathway in SE. In addition, the present study analyzed the dynamics of the expression of autophagy-associated factors in the hippocampus after SE induction, and the influence of suppressing the p- of PRAS40 on the autophagy process was detected in the pathogenesis of SE. The results indicated that increased p-PRAS40 expression could activate the mTOR pathway to decrease the level of autophagy. However, inhibition of the mTOR signaling pathway promoted autophagy flux. These results may provide further understanding of p-PRAS40 functions in SE.
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Affiliation(s)
- Junyi Lin
- School of Policing Studies, Shanghai University of Political Science and Law, Shanghai 201701, P.R. China.,Department of Forensic Medicine, School of Basic Medical Sciences, Fudan University, Shanghai 200032, P.R. China
| | - Youxin Fang
- General Family Medicine Clinic, Xuhui District Xietu Subdistrict Community Healthcare Center, Shanghai 200120, P.R. China
| | - Mingchang Zhang
- Department of Forensic Medicine, School of Basic Medical Sciences, Fudan University, Shanghai 200032, P.R. China
| | - Xiang Wang
- Institute of Forensic Science, Jiading Branch of Shanghai Public Security Bureau, Shanghai 201800, P.R. China
| | - Liliang Li
- Department of Forensic Medicine, School of Basic Medical Sciences, Fudan University, Shanghai 200032, P.R. China
| | - Meng He
- Department of Forensic Medicine, School of Basic Medical Sciences, Fudan University, Shanghai 200032, P.R. China
| | - Aimin Xue
- Department of Forensic Medicine, School of Basic Medical Sciences, Fudan University, Shanghai 200032, P.R. China
| | - Keming Zhu
- Department of Anatomy, Histology and Embryology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, P.R. China
| | - Yiwen Shen
- Department of Forensic Medicine, School of Basic Medical Sciences, Fudan University, Shanghai 200032, P.R. China
| | - Beixu Li
- School of Policing Studies, Shanghai University of Political Science and Law, Shanghai 201701, P.R. China.,Department of Forensic Medicine, School of Basic Medical Sciences, Fudan University, Shanghai 200032, P.R. China
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5
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Zhang L, Li X, Zhang N, Yang X, Hou T, Fu W, Yuan F, Wang L, Wen H, Tian Y, Zhang H, Lu X, Zhu WG. WDFY2 Potentiates Hepatic Insulin Sensitivity and Controls Endosomal Localization of the Insulin Receptor and IRS1/2. Diabetes 2020; 69:1887-1902. [PMID: 32641353 DOI: 10.2337/db19-0699] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 06/04/2020] [Indexed: 11/13/2022]
Abstract
Endosomes help activate the hepatic insulin-evoked Akt signaling pathway, but the underlying regulatory mechanisms are unclear. Previous studies have suggested that the endosome-located protein WD repeat and FYVE domain-containing 2 (WDFY2) might be involved in metabolic disorders, such as diabetes. Here, we generated Wdfy2 knockout (KO) mice and assessed the metabolic consequences. These KO mice exhibited systemic insulin resistance, with increased gluconeogenesis and suppressed glycogen accumulation in the liver. Mechanistically, we found that the insulin-stimulated activation of Akt2 and its substrates FoxO1 and GSK-3β is attenuated in the Wdfy2 KO liver and H2.35 hepatocytes, suggesting that WDFY2 acts as an important regulator of hepatic Akt2 signaling. We further found that WDFY2 interacts with the insulin receptor (INSR) via its WD1-4 domain and localizes the INSR to endosomes after insulin stimulation. This process ensures that the downstream insulin receptor substrates 1 and 2 (IRS1/2) can be recruited to the endosomal INSR. IRS1/2-INSR binding promotes IRS1/2 phosphorylation and subsequent activation, initiating downstream Akt2 signaling in the liver. Interestingly, adeno-associated viral WDFY2 delivery ameliorated metabolic defects in db/db mice. These findings demonstrate that WDFY2 activates insulin-evoked Akt2 signaling by controlling endosomal localization of the INSR and IRS1/2 in hepatocytes. This pathway might constitute a new potential target for diabetes prevention or treatment.
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Affiliation(s)
- Luyao Zhang
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Xue Li
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Nan Zhang
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Xin Yang
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Tianyun Hou
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
- Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, International Cancer Center, Shenzhen University School of Medicine, Shenzhen, China
| | - Wan Fu
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Fengjie Yuan
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Lina Wang
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - He Wen
- Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, International Cancer Center, Shenzhen University School of Medicine, Shenzhen, China
| | - Yuan Tian
- Shenzhen Bay Laboratory, Shenzhen, China
| | - Hongquan Zhang
- Department of Human Anatomy, Histology, and Embryology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Xifeng Lu
- Department of Physiology, Shenzhen University School of Medicine, Shenzhen, China
| | - Wei-Guo Zhu
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
- Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, International Cancer Center, Shenzhen University School of Medicine, Shenzhen, China
- Shenzhen Bay Laboratory, Shenzhen, China
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6
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Chew HY, De Lima PO, Gonzalez Cruz JL, Banushi B, Echejoh G, Hu L, Joseph SR, Lum B, Rae J, O’Donnell JS, Merida de Long L, Okano S, King B, Barry R, Moi D, Mazzieri R, Thomas R, Souza-Fonseca-Guimaraes F, Foote M, McCluskey A, Robinson PJ, Frazer IH, Saunders NA, Parton RG, Dolcetti R, Cuff K, Martin JH, Panizza B, Walpole E, Wells JW, Simpson F. Endocytosis Inhibition in Humans to Improve Responses to ADCC-Mediating Antibodies. Cell 2020; 180:895-914.e27. [DOI: 10.1016/j.cell.2020.02.019] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 01/19/2020] [Accepted: 02/07/2020] [Indexed: 12/31/2022]
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7
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Rozenberg K, Rosenzweig T. Sarcopoterium spinosum extract improved insulin sensitivity in mice models of glucose intolerance and diabetes. PLoS One 2018; 13:e0196736. [PMID: 29768504 PMCID: PMC5955592 DOI: 10.1371/journal.pone.0196736] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 04/18/2018] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The glucose lowering properties of Sarcopoterium spinosum, a traditional medicinal plant, were previously validated by us using KK-Ay mice as a genetic model for type 2 diabetes (T2D). OBJECTIVE To clarify the effects of Sarcopoterium spinosum extract (SSE) on diet-induced glucose intolerance and to investigate SSE effects on carbohydrate and lipid metabolism in target tissues of both high-fat-diet (HFD)-fed and KK-Ay mice. RESULTS Mice were given SSE (70 mg/day) for 6 weeks. SSE improved glucose tolerance and insulin sensitivity in HFD-fed mice as was demonstrated previously in KK-Ay mice. Higher insulin sensitivity was validated by lower serum insulin and activation of the insulin signaling cascade in skeletal muscle and liver of SSE-treated mice in both models. H&E staining of the livers demonstrated lower severity of steatosis in SSE-treated mice. Several model-specific effects of SSE were observed-mRNA expression of proinflammatory genes and CD36 was reduced in SSE-treated KK-Ay mice. Hepatic mRNA expression of PEPCK was also reduced in SSE-treated KK-Ay mice, while other genes involved in carbohydrates and lipid metabolism were not affected. HFD-fed mice treated by SSE had elevated hepatic glycogen stores. Gluconeogenic gene expression was not affected, while GCK expression was increased. HFD-induced hepatic steatosis was not affected by SSE. However, while genes involved in lipid metabolism were downregulated by HFD, this was not found in HFD-fed mice given SSE, demonstrating an expression profile which is similar to that of standard diet-fed mice. CONCLUSION Our study supports the insulin sensitizing activity of SSE and suggests that this extract might improve other manifestations of the metabolic syndrome.
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Affiliation(s)
- Konstantin Rozenberg
- Departments of Molecular Biology and Nutritional Studies, Ariel University, Ariel, Israel
| | - Tovit Rosenzweig
- Departments of Molecular Biology and Nutritional Studies, Ariel University, Ariel, Israel
- * E-mail:
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8
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Quiclet C, Dubouchaud H, Berthon P, Sanchez H, Vial G, Siti F, Fontaine E, Batandier C, Couturier K. Maternal exercise modifies body composition and energy substrates handling in male offspring fed a high-fat/high-sucrose diet. J Physiol 2017; 595:7049-7062. [PMID: 28971475 DOI: 10.1113/jp274739] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 09/21/2017] [Indexed: 01/23/2023] Open
Abstract
KEY POINTS Maternal training during gestation enhances offspring body composition and energy substrates handling in early adulthood. Offspring nutrition also plays a role as some beneficial effects of maternal training during gestation disappear after consumption of a high-fat diet. ABSTRACT Maternal exercise during gestation has been reported to modify offspring metabolism and health. Whether these effects are exacerbated when offspring are receiving a high-fat diet remains unclear. Our purpose was to evaluate the effect of maternal exercise before and during gestation on the offspring fed a high-fat/high-sucrose diet (HF) by assessing its body composition, pancreatic function and energy substrates handling by two major glucose-utilizing tissues: liver and muscle. Fifteen-week-old nulliparous female Wistar rats exercised 4 weeks before as well as during gestation at a constant submaximal intensity (TR) or remained sedentary (CT). At weaning, pups from each group were fed either a standard diet (TRCD or CTCD) or a high-fat/high-sucrose diet (TRHF or CTHF) for 10 weeks. Offspring from TR dams gained less weight compared to those from CT dams. Selected fat depots were larger with the HF diet compared to control diet (CD) but significantly smaller in TRHF compared to CTHF. Surprisingly, the insulin secretion index was higher in islets from HF offspring compared to CD. TR offspring showed a higher muscle insulin sensitivity estimated by the ratio of phosphorylated protein kinase B to total protein kinase B compared with CT offspring (+48%, P < 0.05). With CD, permeabilized isolated muscle fibres from TR rats displayed a lower apparent affinity constant (Km ) for pyruvate and palmitoyl coenzyme A as substrates compared to the CT group (-46% and -58%, respectively, P < 0.05). These results suggest that maternal exercise has positive effects on young adult offspring body composition and on muscle carbohydrate and lipid metabolism depending on the nutritional status.
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Affiliation(s)
- Charline Quiclet
- Université Grenoble Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA), Grenoble, France.,Inserm, U1055, Grenoble, France.,Université Grenoble Alpes, UFR Sciences et Techniques des Activités Physiques et Sportives (UFR STAPS), Structure Fédérative de Recherche Sport Exercice Motricité (SFR SEM), Grenoble, France
| | - Hervé Dubouchaud
- Université Grenoble Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA), Grenoble, France.,Inserm, U1055, Grenoble, France.,Université Grenoble Alpes, UFR Sciences et Techniques des Activités Physiques et Sportives (UFR STAPS), Structure Fédérative de Recherche Sport Exercice Motricité (SFR SEM), Grenoble, France
| | - Phanélie Berthon
- Laboratoire Interdisciplinaire de Biologie de la Motricité, Université Savoie Mont Blanc, Le Bourget du Lac, France
| | - Hervé Sanchez
- French Armed Biomedical Research Institute, Brétigny-sur-Orge, France
| | - Guillaume Vial
- Université Grenoble Alpes, UFR Sciences et Techniques des Activités Physiques et Sportives (UFR STAPS), Structure Fédérative de Recherche Sport Exercice Motricité (SFR SEM), Grenoble, France.,Inserm, U1042, Grenoble, France
| | - Farida Siti
- Université Grenoble Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA), Grenoble, France.,Inserm, U1055, Grenoble, France.,Faculty of Universitas Indonesia, Jakarta, Indonesia
| | - Eric Fontaine
- Université Grenoble Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA), Grenoble, France.,Inserm, U1055, Grenoble, France.,Grenoble University Hospital, Grenoble, France
| | - Cécile Batandier
- Université Grenoble Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA), Grenoble, France.,Inserm, U1055, Grenoble, France
| | - Karine Couturier
- Université Grenoble Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA), Grenoble, France.,Inserm, U1055, Grenoble, France.,Université Grenoble Alpes, UFR Sciences et Techniques des Activités Physiques et Sportives (UFR STAPS), Structure Fédérative de Recherche Sport Exercice Motricité (SFR SEM), Grenoble, France
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9
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Lv D, Guo L, Zhang T, Huang L. PRAS40 signaling in tumor. Oncotarget 2017; 8:69076-69085. [PMID: 28978182 PMCID: PMC5620322 DOI: 10.18632/oncotarget.17299] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 04/11/2017] [Indexed: 12/11/2022] Open
Abstract
The proline-rich Akt substrate of 40 kDa (PRAS40) is a substrate of Akt and a component of the mammalian target of rapamycin complex 1 (mTORC1). Locating at the crossroad of the PI3K/Akt pathway and the mTOR pathway, PRAS40 is phosphorylated by growth factors or other stimuli, and regulates the activation of these signaling pathways in turn. PRAS40 plays an important role in metabolic disorders and multiple cancers, and the phosphorylation of PRAS40 is often associated with the tumor progression of melanoma, prostate cancer, etc. PRAS40 promotes tumorigenesis by deregulating cellular proliferation, apoptosis, senescence, metastasis, etc. Herein, we provide an overview on current understandings of PRAS40 signaling in the tumor formation and progression, which suggests that PRAS40 or phospho-PRAS40 could become a novel biomarker and therapeutic target in tumor.
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Affiliation(s)
- Dan Lv
- Department of Pathophysiology, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
| | - Lianying Guo
- Department of Pathophysiology, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
| | - Ting Zhang
- Department of Pathophysiology, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
| | - Lin Huang
- Department of Pathophysiology, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
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10
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Velazquez R, Shaw DM, Caccamo A, Oddo S. Pim1 inhibition as a novel therapeutic strategy for Alzheimer's disease. Mol Neurodegener 2016; 11:52. [PMID: 27412291 PMCID: PMC4944476 DOI: 10.1186/s13024-016-0118-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 07/02/2016] [Indexed: 01/07/2023] Open
Abstract
Background Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder worldwide. Clinically, AD is characterized by impairments of memory and cognitive functions. Accumulation of amyloid-β (Aβ) and neurofibrillary tangles are the prominent neuropathologies in patients with AD. Strong evidence indicates that an imbalance between production and degradation of key proteins contributes to the pathogenesis of AD. The mammalian target of rapamycin (mTOR) plays a key role in maintaining protein homeostasis as it regulates both protein synthesis and degradation. A key regulator of mTOR activity is the proline-rich AKT substrate 40 kDa (PRAS40), which directly binds to mTOR and reduces its activity. Notably, AD patients have elevated levels of phosphorylated PRAS40, which correlate with Aβ and tau pathologies as well as cognitive deficits. Physiologically, PRAS40 phosphorylation is regulated by Pim1, a protein kinase of the protoconcogene family. Here, we tested the effects of a selective Pim1 inhibitor (Pim1i), on spatial reference and working memory and AD-like pathology in 3xTg-AD mice. Results We have identified a Pim1i that crosses the blood brain barrier and reduces PRAS40 phosphorylation. Pim1i-treated 3xTg-AD mice performed significantly better than their vehicle treated counterparts as well as non-transgenic mice. Additionally, 3xTg-AD Pim1i-treated mice showed a reduction in soluble and insoluble Aβ40 and Aβ42 levels, as well as a 45.2 % reduction in Aβ42 plaques within the hippocampus. Furthermore, phosphorylated tau immunoreactivity was reduced in the hippocampus of Pim1i–treated 3xTg-AD mice by 38 %. Mechanistically, these changes were linked to a significant increase in proteasome activity. Conclusion These results suggest that reductions in phosphorylated PRAS40 levels via Pim1 inhibition reduce Aβ and Tau pathology and rescue cognitive deficits by increasing proteasome function. Given that Pim1 inhibitors are already being tested in ongoing human clinical trials for cancer, the results presented here may open a new venue of drug discovery for AD by developing more Pim1 inhibitors.
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Affiliation(s)
- Ramon Velazquez
- Neurodegenerative Disease Research Center, Biodesign Institute, School of Life Sciences, Arizona State University, 727 E. Tyler Street, Tempe, AZ, 85287-5001, USA
| | - Darren M Shaw
- Neurodegenerative Disease Research Center, Biodesign Institute, School of Life Sciences, Arizona State University, 727 E. Tyler Street, Tempe, AZ, 85287-5001, USA.,School of Life Sciences, Arizona State University, Tempe, AZ, 85287, USA
| | - Antonella Caccamo
- Neurodegenerative Disease Research Center, Biodesign Institute, School of Life Sciences, Arizona State University, 727 E. Tyler Street, Tempe, AZ, 85287-5001, USA
| | - Salvatore Oddo
- Neurodegenerative Disease Research Center, Biodesign Institute, School of Life Sciences, Arizona State University, 727 E. Tyler Street, Tempe, AZ, 85287-5001, USA. .,School of Life Sciences, Arizona State University, Tempe, AZ, 85287, USA.
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11
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Phosphoprotein network analysis of white adipose tissues unveils deregulated pathways in response to high-fat diet. Sci Rep 2016; 6:25844. [PMID: 27180971 PMCID: PMC4867603 DOI: 10.1038/srep25844] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 04/22/2016] [Indexed: 12/27/2022] Open
Abstract
Despite efforts in the last decade, signaling aberrations associated with obesity remain poorly understood. To dissect molecular mechanisms that define this complex metabolic disorder, we carried out global phosphoproteomic analysis of white adipose tissue (WAT) from mice fed on low-fat diet (LFD) and high-fat diet (HFD). We quantified phosphorylation levels on 7696 peptides, and found significant differential phosphorylation levels in 282 phosphosites from 191 proteins, including various insulin-responsive proteins and metabolic enzymes involved in lipid homeostasis in response to high-fat feeding. Kinase-substrate prediction and integrated network analysis of the altered phosphoproteins revealed underlying signaling modulations during HFD-induced obesity, and suggested deregulation of lipogenic and lipolytic pathways. Mutation of the differentially-regulated novel phosphosite on cytoplasmic acetyl-coA forming enzyme ACSS2 (S263A) upon HFD-induced obesity led to accumulation of serum triglycerides and reduced insulin-responsive AKT phosphorylation as compared to wild type ACSS2, thus highlighting its role in obesity. Altogether, our study presents a comprehensive map of adipose tissue phosphoproteome in obesity and reveals many previously unknown candidate phosphorylation sites for future functional investigation.
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12
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Bertuzzi A, Conte F, Mingrone G, Papa F, Salinari S, Sinisgalli C. Insulin Signaling in Insulin Resistance States and Cancer: A Modeling Analysis. PLoS One 2016; 11:e0154415. [PMID: 27149630 PMCID: PMC4858213 DOI: 10.1371/journal.pone.0154415] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 04/12/2016] [Indexed: 01/21/2023] Open
Abstract
Insulin resistance is the common denominator of several diseases including type 2 diabetes and cancer, and investigating the mechanisms responsible for insulin signaling impairment is of primary importance. A mathematical model of the insulin signaling network (ISN) is proposed and used to investigate the dose-response curves of components of this network. Experimental data of C2C12 myoblasts with phosphatase and tensin homologue (PTEN) suppressed and data of L6 myotubes with induced insulin resistance have been analyzed by the model. We focused particularly on single and double Akt phosphorylation and pointed out insulin signaling changes related to insulin resistance. Moreover, a new characterization of the upstream signaling of the mammalian target of rapamycin complex 2 (mTORC2) is presented. As it is widely recognized that ISN proteins have a crucial role also in cell proliferation and death, the ISN model was linked to a cell population model and applied to data of a cell line of acute myeloid leukemia treated with a mammalian target of rapamycin inhibitor with antitumor activity. The analysis revealed simple relationships among the concentrations of ISN proteins and the parameters of the cell population model that characterize cell cycle progression and cell death.
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Affiliation(s)
- Alessandro Bertuzzi
- Institute of Systems Analysis and Computer Science “A. Ruberti”, CNR, 00185, Rome, Italy
| | - Federica Conte
- Institute of Systems Analysis and Computer Science “A. Ruberti”, CNR, 00185, Rome, Italy
- Department of Computer and System Science, Sapienza University of Rome, 00185, Rome, Italy
| | - Geltrude Mingrone
- Department of Internal Medicine, Catholic University School of Medicine, 00168, Rome, Italy
- * E-mail:
| | - Federico Papa
- Institute of Systems Analysis and Computer Science “A. Ruberti”, CNR, 00185, Rome, Italy
- SYSBIO - Centre of Systems Biology, Milan, Italy
| | - Serenella Salinari
- Department of Computer and System Science, Sapienza University of Rome, 00185, Rome, Italy
| | - Carmela Sinisgalli
- Institute of Systems Analysis and Computer Science “A. Ruberti”, CNR, 00185, Rome, Italy
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13
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Chong ZZ. Targeting PRAS40 for multiple diseases. Drug Discov Today 2016; 21:1222-31. [PMID: 27086010 DOI: 10.1016/j.drudis.2016.04.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/18/2016] [Accepted: 04/07/2016] [Indexed: 12/19/2022]
Abstract
Proline-rich Akt substrate 40kDa (PRAS40) bridges cell signaling between protein kinase B (Akt) and the mammalian target of rapamycin complex 1 (mTORC1). Both Akt and mTORC1 can phosphorylate PRAS40. As a negative regulator of mTORC1, PRAS40 prevents the binding of mTOR to its substrates. The phosphorylation of PRAS40 results in its dissociation from mTORC1 and enhanced mTOR activation. PRAS40 in conjunction with mTORC1 has been closely associated with programmed cell death and is implicated in diabetes mellitus (DM), cardiovascular diseases, cancer, and neurological diseases. Thus, targeting PRAS40 might hold great promise for innovative therapeutic strategies for these diseases.
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Affiliation(s)
- Zhao Zhong Chong
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL, USA; Institute of Materia Medica, Shandong Academy of Medical Sciences, Jinan, China.
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14
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Wang H, Arias EB, Cartee GD. Calorie restriction leads to greater Akt2 activity and glucose uptake by insulin-stimulated skeletal muscle from old rats. Am J Physiol Regul Integr Comp Physiol 2016; 310:R449-58. [PMID: 26739650 DOI: 10.1152/ajpregu.00449.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 12/30/2015] [Indexed: 11/22/2022]
Abstract
Skeletal muscle insulin resistance is associated with many common age-related diseases, but moderate calorie restriction (CR) can substantially elevate glucose uptake by insulin-stimulated skeletal muscle from both young and old rats. The current study evaluated the isolated epitrochlearis muscle from ∼24.5-mo-old rats that were either fed ad libitum (AL) or subjected to CR (consuming ∼65% of ad libitum, AL, intake beginning at ∼22.5 mo old). Some muscles were also incubated with MK-2206, a potent and selective Akt inhibitor. The most important results were that in isolated muscles, CR vs. AL resulted in 1) greater insulin-stimulated glucose uptake 2) that was accompanied by significantly increased insulin-mediated activation of Akt2, as indicated by greater phosphorylation on both Thr(309) and Ser(474) along with greater Akt2 activity, 3) concomitant with enhanced phosphorylation of several Akt substrates, including an Akt substrate of 160 kDa on Thr(642) and Ser(588), filamin C on Ser(2213) and proline-rich Akt substrate of 40 kDa on Thr(246), but not TBC1D1 on Thr(596); and 4) each of the CR effects was eliminated by MK-2206. These data provide compelling new evidence linking greater Akt2 activation to the CR-induced elevation of insulin-stimulated glucose uptake by muscle from old animals.
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Affiliation(s)
- Haiyan Wang
- Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan; College of Physical Education and Health, East China Normal University, Shanghai, China
| | - Edward B Arias
- Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Gregory D Cartee
- Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan; and Institute of Gerontology, University of Michigan, Ann Arbor, Michigan
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15
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Unacylated ghrelin restores insulin and autophagic signaling in skeletal muscle of diabetic mice. Pflugers Arch 2015; 467:2555-69. [PMID: 26228926 DOI: 10.1007/s00424-015-1721-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 06/21/2015] [Accepted: 07/13/2015] [Indexed: 01/04/2023]
Abstract
Impairment of insulin signaling in skeletal muscle detrimentally affects insulin-stimulated disposal of glucose. Restoration of insulin signaling in skeletal muscle is important as muscle is one of the major sites for disposal of blood glucose. Recently, unacylated ghrelin (UnAG) has received attention in diabetic research due to its favorable actions on improving glucose tolerance, glycemic control, and insulin sensitivity. The investigation of UnAG has entered phase Ib clinical trial in type 2 diabetes and phase II clinical trial in hyperphagia in Prader-Willi syndrome. Nonetheless, the precise mechanisms responsible for the anti-diabetic actions of UnAG remain incompletely understood. In this study, we examined the effects of UnAG on restoring the impaired insulin signaling in skeletal muscle of db/db diabetic mice. Our results demonstrated that UnAG effectively restored the impaired insulin signaling in diabetic muscle. UnAG decreased insulin receptor substrate (IRS) phosphorylation, increased protein kinase B (Akt) phosphorylation, and, hence, suppressed mTOR signaling. Consequently, UnAG enhanced Glut4 localization and increased PDH activity in the diabetic skeletal muscle. Intriguingly, our data indicated that UnAG normalized the suppressed autophagic signaling in diabetic muscle. In conclusion, our findings illustrated that UnAG restored the impaired insulin and autophagic signaling in skeletal muscle of diabetic mice, which are valuable to understand the underlying mechanisms of the anti-diabetic action of UnAG at peripheral skeletal muscle level.
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16
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Proline-rich AKT substrate of 40-kDa (PRAS40) in the pathophysiology of cancer. Biochem Biophys Res Commun 2015; 463:161-6. [PMID: 26003731 DOI: 10.1016/j.bbrc.2015.05.041] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 05/07/2015] [Indexed: 12/18/2022]
Abstract
Dysregulation of PI3K-AKT-mTOR pathway has been reported in various pathologies, such as cancer and insulin resistance. The proline-rich AKT substrate of 40-kDa (PRAS40), also known as AKT substrate 1 (AKT1S1), lies at the crossroads of these cascades and inhibits the activity of the mTOR complex 1 (mTORC1) kinase. This review discusses the role of PRAS40 and possible feedback mechanisms, and alterations in AKT/PRAS40/mTOR signaling that have been implicated in the pathogenesis of tumor progression. Additionally, we probed new datasets extracted from Oncomine, a cancer microarray database containing datasets derived from patient samples, to further understand the role of PRAS40 (AKT1S1). These data strongly supports the hypothesis that PRAS40 may serve as a potential therapeutic target for various cancers.
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17
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Malla R, Wang Y, Chan WK, Tiwari AK, Faridi JS. Genetic ablation of PRAS40 improves glucose homeostasis via linking the AKT and mTOR pathways. Biochem Pharmacol 2015; 96:65-75. [PMID: 25931147 DOI: 10.1016/j.bcp.2015.04.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 04/23/2015] [Indexed: 12/22/2022]
Abstract
Alterations in PI3K-AKT-mTOR signaling have been implicated in diabetes. This study assessed whether disruption of PRAS40, a substrate of AKT and component of mTORC1, would alter glucose homeostasis and prevent hyperglycemia in the streptozotocin (STZ)-induced diabetes mouse model. PRAS40 ablation resulted in a mild lowering of blood glucose levels and glycated hemoglobin (HbA1C), a lowered insulin requirement, and improved glucose tolerance in untreated PRAS40 gene knockout (PRAS40(-/-)) as compared to wild-type (PRAS40(+/+)) mice. Diabetes was then induced in these mice using STZ at 50mg/kg/day over five days. Following STZ-treatment, PRAS40(-/-) mice exhibited significantly lower blood glucose and HbA1C levels than PRAS40(+/+) mice. Liver tissue of PRAS40(-/-) mice and shPRAS40 Hep3B cells showed increased activation of AKT (p-AKT T308) and mTORC1 (p-p70S6K) signaling as well as decreased p-AKT (S473) and increased p-IRS1 (S612) protein levels. Altered tissue gene expression of several glucose transporters (GLUT) and increased hepatic GLUT4 protein levels were observed in PRAS40(-/-) as compared to PRAS40(+/+) mice. In summary, PRAS40 deletion significantly attenuates hyperglycemia in STZ-induced PRAS40(-/-) mice through increased hepatic AKT and mTORC1 signaling, a lowered serum insulin requirement, and altered hepatic GLUT4 levels.
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Affiliation(s)
- Ritu Malla
- Department of Physiology and Pharmacology, T. J. Long School of Pharmacy & Health Sciences, University of the Pacific, Stockton, CA, United States
| | - Yu Wang
- Department of Pharmaceutics and Medicinal Chemistry, T. J. Long School of Pharmacy & Health Sciences, University of the Pacific, Stockton, CA, United States
| | - William K Chan
- Department of Pharmaceutics and Medicinal Chemistry, T. J. Long School of Pharmacy & Health Sciences, University of the Pacific, Stockton, CA, United States
| | - Amit K Tiwari
- Department of Pharmacology and Experimental Therapeutics, College of Pharmacy & Pharmaceutical Sciences, University of Toledo, OH, United States
| | - Jesika S Faridi
- Department of Physiology and Pharmacology, T. J. Long School of Pharmacy & Health Sciences, University of the Pacific, Stockton, CA, United States.
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18
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Hao J, Li F, Liu W, Liu Q, Liu S, Li H, Duan H. Phosphorylation of PRAS40-Thr246 involved in renal lipid accumulation of diabetes. J Cell Physiol 2014; 229:1069-77. [PMID: 24347388 DOI: 10.1002/jcp.24533] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 12/05/2013] [Indexed: 12/16/2022]
Abstract
Lipid accumulation of kidney is a threat to renal physiological function of diabetes. The previous studies on diabetic nephropathy have demonstrated that activated Akt was involved in renal lipogenesis through enhancing transcription factor SREBP-1. PRAS40 is one of the downstream targets of activated Akt that was reported to involve in lipid metabolism in hepatic cells. However, it is still not clear whether PRAS40 is also involved in the renal lipogenesis of diabetes. Our study revealed that phosphorylation of PRAS40-Thr246 known as inactivated style increased in renal tubular cells of diabetic rats accompanied with over-expression of phospho-Akt, SREBP-1, and ADRP. In addition, in vitro experiment also found that high glucose enhanced expression of phospho-PRAS40-Thr246 followed by increased SREBP-1 and lipid droplets in HKC cells. After treated with LY294002, high glucose-induced HKC cells showed decreased phospho-PRAS40-Thr246, phospho-Akt-Ser473, and SREBP-1. Furthermore, wild type PRAS40 vector-caused increased phospho-PRAS40-Thr246 exaggerated lipid deposits in high glucose-treated HKC cells, which was effectively prevented in cells transfected with mutant PRAS40 vector (T246A). These above data suggested that phosphorylation of PRAS40-Thr246 mediated abnormal lipid metabolism in kidney of diabetes and might be the potential target for treating lipogenesis of diabetic nephropathy.
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Affiliation(s)
- Jun Hao
- Department of Pathology, Hebei Medical University, Shijiazhuang City, Hebei Province, China
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19
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Wiza C, Chadt A, Blumensatt M, Kanzleiter T, Herzfeld De Wiza D, Horrighs A, Mueller H, Nascimento EBM, Schürmann A, Al-Hasani H, Ouwens DM. Over-expression of PRAS40 enhances insulin sensitivity in skeletal muscle. Arch Physiol Biochem 2014; 120:64-72. [PMID: 24576065 DOI: 10.3109/13813455.2014.894076] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
CONTEXT Silencing proline-rich Akt substrate of 40-kDa (PRAS40) impairs insulin signalling in skeletal muscle. OBJECTIVE This study assessed the effects of over-expressing wild type or mutant AAA-PRAS40, in which the major phosphorylation sites and mTORC1-binding site were mutated, on insulin signalling in skeletal muscle. RESULTS Over-expression of WT-PRAS40, but not AAA-PRAS40, impaired the insulin-mediated activation of the mTORC1-pathway in human skeletal muscle cells (hSkMC). However, insulin-mediated Akt-phosphorylation was increased upon over-expression of WT-PRAS40 both in hSkMC and mouse skeletal muscle. Also over-expression of AAA-PRAS40 had an insulin-sensitizing effect, although to a lesser extent as WT-PRAS40. The insulin-sensitizing effect associated with increased IRS1 protein abundance and inhibition of proteasome activity. Finally, over-expression of WT-PRAS40 reversed hyperinsulinemia-induced insulin resistance. CONCLUSION This study identifies PRAS40 as a regulator of insulin sensitivity in hSkMC. In contrast to the mTORC1-pathway, the insulin-sensitizing action of PRAS40 occurs independent of binding of PRAS40 to the mTORC1-complex.
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Affiliation(s)
- Claudia Wiza
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Centre , Auf'mHennekamp 65, D-40225 Düsseldorf , Germany
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20
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Havel JJ, Li Z, Cheng D, Peng J, Fu H. Nuclear PRAS40 couples the Akt/mTORC1 signaling axis to the RPL11-HDM2-p53 nucleolar stress response pathway. Oncogene 2014; 34:1487-98. [PMID: 24704832 PMCID: PMC4216640 DOI: 10.1038/onc.2014.91] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2013] [Revised: 02/26/2014] [Accepted: 03/01/2014] [Indexed: 12/27/2022]
Abstract
The Ribosomal Protein (RP)-HDM2-p53 pathway has been shown to play key roles in oncogene-induced apoptosis and senescence, but the mechanism regulating this pathway remains elusive. The Proline-Rich Akt Substrate of 40 kDA (PRAS40) has recently been identified as a binding partner and inhibitor of the mechanistic Target of Rapamycin Complex 1 (mTORC1). Although other inhibitors of mTORC1 are known tumor suppressors, PRAS40 promotes cell survival and tumorigenesis. Here we demonstrate that Akt- and mTORC1-mediated phosphorylation of PRAS40 at T246 and S221, respectively, promotes nuclear-specific association of PRAS40 with Ribosomal Protein L11 (RPL11). Importantly, silencing of PRAS40 induces upregulation of p53 in a manner dependent upon RPL11. This effect is rescued by wild type PRAS40, but not by the RPL11 binding-null PRAS40 T246A mutant. We find that PRAS40 negatively regulates the RPL11-HDM2-p53 nucleolar stress response pathway and suppresses induction of p53-mediated cellular senescence. This work identifies nuclear PRAS40 as a dual-input signaling checkpoint that links cell growth and proliferation to inhibition of cellular senescence. These findings may help to explain the pro-tumorigenic effect of PRAS40 and identify the PRAS40-RPL11 complex as a promising target for p53-restorative anti-cancer drug discovery.
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Affiliation(s)
- J J Havel
- 1] Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, USA [2] Graduate Program in Molecular and Systems Pharmacology, Emory University, Atlanta, GA, USA
| | - Z Li
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, USA
| | - D Cheng
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
| | - J Peng
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
| | - H Fu
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, USA
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Pathological hypertrophy amelioration by PRAS40-mediated inhibition of mTORC1. Proc Natl Acad Sci U S A 2013; 110:12661-6. [PMID: 23842089 DOI: 10.1073/pnas.1301455110] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Mechanistic target of rapamycin complex 1 (mTORC1), necessary for cellular growth, is regulated by intracellular signaling mediating inhibition of mTORC1 activation. Among mTORC1 regulatory binding partners, the role of Proline Rich AKT Substrate of 40 kDa (PRAS40) in controlling mTORC1 activity and cellular growth in response to pathological and physiological stress in the heart has never been addressed. This report shows PRAS40 is regulated by AKT in cardiomyocytes and that AKT-driven phosphorylation relieves the inhibitory function of PRAS40. PRAS40 overexpression in vitro blocks mTORC1 in cardiomyocytes and decreases pathological growth. Cardiomyocyte-specific overexpression in vivo blunts pathological remodeling after pressure overload and preserves cardiac function. Inhibition of mTORC1 by PRAS40 preferentially promotes protective mTORC2 signaling in chronic diseased myocardium. In contrast, strong PRAS40 phosphorylation by AKT allows for physiological hypertrophy both in vitro and in vivo, whereas cardiomyocyte-specific overexpression of a PRAS40 mutant lacking capacity for AKT-phosphorylation inhibits physiological growth in vivo, demonstrating that AKT-mediated PRAS40 phosphorylation is necessary for induction of physiological hypertrophy. Therefore, PRAS40 phosphorylation acts as a molecular switch allowing mTORC1 activation during physiological growth, opening up unique possibilities for therapeutic regulation of the mTORC1 complex to mitigate pathologic myocardial hypertrophy by PRAS40.
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22
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Wiza C, Nascimento EBM, Linssen MML, Carlotti F, Herzfeld de Wiza D, van der Zon GCM, Maassen JA, Diamant M, Guigas B, Ouwens DM. Proline-rich Akt substrate of 40-kDa contains a nuclear export signal. Cell Signal 2013; 25:1762-8. [PMID: 23712034 DOI: 10.1016/j.cellsig.2013.05.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2013] [Revised: 05/07/2013] [Accepted: 05/12/2013] [Indexed: 01/01/2023]
Abstract
The proline-rich Akt substrate of 40-kDa (PRAS40) has been linked to the regulation of the activity of the mammalian target of rapamycin complex 1 as well as insulin action. Despite these cytosolic functions, PRAS40 was originally identified as nuclear phosphoprotein in Hela cells. This study aimed to detail mechanisms and consequences of the nucleocytosolic trafficking of PRAS40. Sequence analysis identified a potential leucine-rich nuclear export signal (NES) within PRAS40. Incubation of A14 fibroblasts overexpressing human PRAS40 (hPRAS40) resulted in nuclear accumulation of the protein. Furthermore, mutation of the NES mimicked the effects of leptomycin B, a specific inhibitor of nuclear export, on the subcellular localization of hPRAS40. Finally, A14 cells expressing the NES-mutant showed impaired activation of components of the Akt-pathway as well as of the mTORC1 substrate p70 S6 kinase after insulin stimulation. This impaired insulin signaling could be ascribed to reduced protein levels of insulin receptor substrate 1 in cells expressing mutant NES. In conclusion, PRAS40 contains a functional nuclear export signal. Furthermore, enforced nuclear accumulation of PRAS40 impairs insulin action, thereby substantiating the function of this protein in the regulation of insulin sensitivity.
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Affiliation(s)
- Claudia Wiza
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Duesseldorf, Germany
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23
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Wiza C, Herzfeld de Wiza D, Nascimento EBM, Lehr S, Al-Hasani H, Ouwens DM. Knockdown of PRAS40 inhibits insulin action via proteasome-mediated degradation of IRS1 in primary human skeletal muscle cells. Diabetologia 2013; 56:1118-28. [PMID: 23460019 DOI: 10.1007/s00125-013-2861-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2012] [Accepted: 01/23/2013] [Indexed: 10/27/2022]
Abstract
AIMS/HYPOTHESIS The proline-rich Akt substrate of 40 kDa (PRAS40) is a component of the mammalian target of rapamycin complex 1 (mTORC1) and among the most prominent Akt substrates in skeletal muscle. Yet the cellular functions of PRAS40 are incompletely defined. This study assessed the function of PRAS40 in insulin action in primary human skeletal muscle cells (hSkMC). METHODS Insulin action was examined in hSkMC following small interfering RNA-mediated silencing of PRAS40 (also known as AKT1S1) under normal conditions and following chemokine-induced insulin resistance. RESULTS PRAS40 knockdown (PRAS40-KD) in hSkMC decreased insulin-mediated phosphorylation of Akt by 50% (p < 0.05) as well as of the Akt substrates glycogen synthase kinase 3 (40%) and tuberous sclerosis complex 2 (32%) (both p < 0.05). Furthermore, insulin-stimulated glucose uptake was reduced by 20% in PRAS40-KD myotubes (p < 0.05). Exposing PRAS40-KD myotubes to chemokines caused no additional deterioration of insulin action. PRAS40-KD further reduced insulin-mediated phosphorylation of the mTORC1-regulated proteins p70S6 kinase (p70S6K) (47%), S6 (43%), and eukaryotic elongation 4E-binding protein 1 (100%), as well as protein levels of growth factor receptor bound protein 10 (35%) (all p < 0.05). The inhibition of insulin action in PRAS40-KD myotubes was associated with a reduction in IRS1 protein levels (60%) (p < 0.05), and was reversed by pharmacological proteasome inhibition. Accordingly, expression of the genes encoding E3-ligases F-box protein 32 (also known as atrogin-1) and muscle RING-finger protein-1 and activity of the proteasome was elevated in PRAS40-KD myotubes. CONCLUSIONS/INTERPRETATION Inhibition of insulin action in PRAS40-KD myotubes was found to associate with IRS1 degradation promoted by increased proteasome activity rather than hyperactivation of the p70S6K-negative-feedback loop. These findings identify PRAS40 as a modulator of insulin action.
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MESH Headings
- Adaptor Proteins, Signal Transducing/antagonists & inhibitors
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Cells, Cultured
- Chemokine CCL2/metabolism
- Chemokines/metabolism
- Down-Regulation/drug effects
- Female
- Gene Silencing
- Humans
- Hypoglycemic Agents/pharmacology
- Insulin Receptor Substrate Proteins/metabolism
- Insulin Resistance
- Insulin, Regular, Pork/pharmacology
- Intercellular Signaling Peptides and Proteins
- Male
- Muscle, Skeletal/cytology
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/immunology
- Muscle, Skeletal/metabolism
- Phosphorylation/drug effects
- Proteasome Endopeptidase Complex/drug effects
- Proteasome Endopeptidase Complex/metabolism
- Protein Processing, Post-Translational/drug effects
- Proteolysis/drug effects
- Proto-Oncogene Proteins c-akt/metabolism
- RNA, Small Interfering
- Recombinant Proteins/metabolism
- Up-Regulation/drug effects
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Affiliation(s)
- C Wiza
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Auf´m Hennekamp 65, 40225 Düsseldorf, Germany
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Jozefczuk J, Kashofer K, Ummanni R, Henjes F, Rehman S, Geenen S, Wruck W, Regenbrecht C, Daskalaki A, Wierling C, Turano P, Bertini I, Korf U, Zatloukal K, Westerhoff HV, Lehrach H, Adjaye J. A Systems Biology Approach to Deciphering the Etiology of Steatosis Employing Patient-Derived Dermal Fibroblasts and iPS Cells. Front Physiol 2012; 3:339. [PMID: 22969728 PMCID: PMC3432516 DOI: 10.3389/fphys.2012.00339] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 08/03/2012] [Indexed: 12/23/2022] Open
Abstract
Non-alcoholic fatty liver disease comprises a broad spectrum of disease states ranging from simple steatosis to non-alcoholic steatohepatitis. As a result of increases in the prevalences of obesity, insulin resistance, and hyperlipidemia, the number of people with hepatic steatosis continues to increase. Differences in susceptibility to steatohepatitis and its progression to cirrhosis have been attributed to a complex interplay of genetic and external factors all addressing the intracellular network. Increase in sugar or refined carbohydrate consumption results in an increase of insulin and insulin resistance that can lead to the accumulation of fat in the liver. Here we demonstrate how a multidisciplinary approach encompassing cellular reprogramming, transcriptomics, proteomics, metabolomics, modeling, network reconstruction, and data management can be employed to unveil the mechanisms underlying the progression of steatosis. Proteomics revealed reduced AKT/mTOR signaling in fibroblasts derived from steatosis patients and further establishes that the insulin-resistant phenotype is present not only in insulin-metabolizing central organs, e.g., the liver, but is also manifested in skin fibroblasts. Transcriptome data enabled the generation of a regulatory network based on the transcription factor SREBF1, linked to a metabolic network of glycerolipid, and fatty acid biosynthesis including the downstream transcriptional targets of SREBF1 which include LIPIN1 (LPIN) and low density lipoprotein receptor. Glutathione metabolism was among the pathways enriched in steatosis patients in comparison to healthy controls. By using a model of the glutathione pathway we predict a significant increase in the flux through glutathione synthesis as both gamma-glutamylcysteine synthetase and glutathione synthetase have an increased flux. We anticipate that a larger cohort of patients and matched controls will confirm our preliminary findings presented here.
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Affiliation(s)
- Justyna Jozefczuk
- Department of Vertebrate Genomics, Max Planck Institute for Molecular Genetics Berlin, Germany
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Wiza C, Nascimento EBM, Ouwens DM. Role of PRAS40 in Akt and mTOR signaling in health and disease. Am J Physiol Endocrinol Metab 2012; 302:E1453-60. [PMID: 22354785 DOI: 10.1152/ajpendo.00660.2011] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The proline-rich Akt substrate of 40 kDa (PRAS40) acts at the intersection of the Akt- and mammalian target of rapamycin (mTOR)-mediated signaling pathways. The protein kinase mTOR is the catalytic subunit of two distinct signaling complexes, mTOR complex 1 (mTORC1) and mTORC2, that link energy and nutrients to the regulation of cellular growth and energy metabolism. Activation of mTOR in response to nutrients and growth factors results in the phosphorylation of numerous substrates, including the phosphorylations of S6 kinase by mTORC1 and Akt by mTORC2. Alterations in Akt and mTOR activity have been linked to the progression of multiple diseases such as cancer and type 2 diabetes. Although PRAS40 was first reported as substrate for Akt, investigations toward mTOR-binding partners subsequently identified PRAS40 as both component and substrate of mTORC1. Phosphorylation of PRAS40 by Akt and by mTORC1 itself results in dissociation of PRAS40 from mTORC1 and may relieve an inhibitory constraint on mTORC1 activity. Adding to the complexity is that gene silencing studies indicate that PRAS40 is also necessary for the activity of the mTORC1 complex. This review summarizes the regulation and potential function(s) of PRAS40 in the complex Akt- and mTOR-signaling network in health and disease.
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Affiliation(s)
- Claudia Wiza
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Düsseldorf, Germany
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Pereira-Lancha LO, Campos-Ferraz PL, Lancha AH. Obesity: considerations about etiology, metabolism, and the use of experimental models. Diabetes Metab Syndr Obes 2012; 5:75-87. [PMID: 22570558 PMCID: PMC3346207 DOI: 10.2147/dmso.s25026] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Studies have been conducted in order to identify the main factors that contribute to the development of obesity. The role of genetics has also been extensively studied. However, the substantial augmentation of obesity prevalence in the last 20 years cannot be justified only by genetic alterations that, theoretically, would have occurred in such a short time. Thus, the difference in obesity prevalence in various population groups is also related to environmental factors, especially diet and the reduction of physical activity. These aspects, interacting or not with genetic factors, could explain the excess of body fat in large proportions worldwide. This article will focus on positive energy balance, high-fat diet, alteration in appetite control hormones, insulin resistance, amino acids metabolism, and the limitation of the experimental models to address this complex issue.
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Affiliation(s)
| | | | - Antonio H Lancha
- School of Physical Education and Sport, University of Sao Paulo, Sao Paulo, Brazil
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Wang H, Zhang Q, Wen Q, Zheng Y, Lazarovici P, Philip L, Jiang H, Lin J, Zheng W. Proline-rich Akt substrate of 40kDa (PRAS40): a novel downstream target of PI3k/Akt signaling pathway. Cell Signal 2011; 24:17-24. [PMID: 21906675 DOI: 10.1016/j.cellsig.2011.08.010] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 08/19/2011] [Accepted: 08/20/2011] [Indexed: 01/09/2023]
Abstract
Modifications in signaling of the proline-rich Akt substrate of 40-kDa (PRAS40) pathway is implicated in type 2 diabetes and melanoma. PRAS40 is known for its ability to regulate the mammalian target of rapamycin complex 1 (mTORC1) kinase activity, possessing a key regulatory role at the cross point of signal transduction pathways activated by growth factor receptors. Recently it has been found that PRAS40 is regulated by its upstream phosphatidylinositol 3-kinase/Akt (PI3K/Akt) which is activated by many tyrosine kinase receptors growth factors including insulin-like growth factor 1. Also, PRAS40 functions downstream of mTORC1 and upstream from its effectors ribosomal protein S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E binding protein 1 (4E-BP1). Phosphorylation of PRAS40 by Akt and mTORC1 disrupts the binding between mTORC1 and PRAS40, and relieves the inhibitory constraint of PRAS40 on mTORC1 activity. This review summarizes the signaling regulating PRAS40 phosphorylation, as well as the dual function of PRAS40 as substrate and inhibitor of mTORC1 upon growth factor stimulation and under pathophysiological conditions.
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Affiliation(s)
- Haitao Wang
- Neuropharmacology, School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, China
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Pereira-Lancha LO, Coelho DF, de Campos-Ferraz PL, Lancha AH. Body Fat Regulation: Is It a Result of a Simple Energy Balance or a High Fat Intake? J Am Coll Nutr 2010; 29:343-51. [DOI: 10.1080/07315724.2010.10719850] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Hong-Brown LQ, Brown CR, Kazi AA, Huber DS, Pruznak AM, Lang CH. Alcohol and PRAS40 knockdown decrease mTOR activity and protein synthesis via AMPK signaling and changes in mTORC1 interaction. J Cell Biochem 2010; 109:1172-84. [PMID: 20127721 DOI: 10.1002/jcb.22496] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The mTORC1 protein kinase complex consists of mTOR, raptor, mLST8/GbetaL and PRAS40. Previously, we reported that mTOR plays an important role in regulating protein synthesis in response to alcohol (EtOH). However, the mechanisms by which EtOH regulates mTORC1 activity have not been established. Here, we investigated the effect of EtOH on the phosphorylation and interaction of components of mTORC1 in C2C12 myocytes. We also examined the specific role that PRAS40 plays in this process. Incubation of myocytes with EtOH (100 mM, 24 h) increased raptor and PRAS40 phosphorylation. Likewise, there were increased levels of the PRAS40 upstream regulators Akt and IRS-1. EtOH also caused changes in mTORC1 protein-protein interactions. EtOH enhanced the binding of raptor and PRAS40 with mTOR. These alterations occurred in concert with increased binding of 14-3-3 to raptor, while the PRAS40 and 14-3-3 interaction was not affected. The shRNA knockdown (KD) of PRAS40 decreased protein synthesis similarly to EtOH. PRAS40 KD increased raptor phosphorylation and its association with 14-3-3, whereas decreased GbetaL-mTOR binding. The effects of EtOH and PRAS40 KD were mediated by AMPK. Both factors increased in vitro AMPK activity towards the substrate raptor. In addition, KD enhanced the activity of AMPK towards TSC2. Collectively, our results indicate that EtOH stabilizes the association of raptor, PRAS40, and GbetaL with mTOR, while likewise increasing the interaction of raptor with 14-3-3. These data suggest a possible mechanism for the inhibitory effects of EtOH on mTOR kinase activity and protein synthesis in myocytes.
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Affiliation(s)
- Ly Q Hong-Brown
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
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van den Berg SA, Guigas B, Bijland S, Ouwens M, Voshol PJ, Frants RR, Havekes LM, Romijn JA, van Dijk KW. High levels of dietary stearate promote adiposity and deteriorate hepatic insulin sensitivity. Nutr Metab (Lond) 2010; 7:24. [PMID: 20346174 PMCID: PMC2852377 DOI: 10.1186/1743-7075-7-24] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Accepted: 03/27/2010] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Relatively little is known about the role of specific saturated fatty acids in the development of high fat diet induced obesity and insulin resistance. Here, we have studied the effect of stearate in high fat diets (45% energy as fat) on whole body energy metabolism and tissue specific insulin sensitivity. METHODS C57Bl/6 mice were fed a low stearate diet based on palm oil or one of two stearate rich diets, one diet based on lard and one diet based on palm oil supplemented with tristearin (to the stearate level of the lard based diet), for a period of 5 weeks. Ad libitum fed Oxidative metabolism was assessed by indirect calorimetry at week 5. Changes in body mass and composition was assessed by DEXA scan analysis. Tissue specific insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp analysis and Western blot at the end of week 5. RESULTS Indirect calorimetry analysis revealed that high levels of dietary stearate resulted in lower caloric energy expenditure characterized by lower oxidation of fatty acids. In agreement with this metabolic phenotype, mice on the stearate rich diets gained more adipose tissue mass. Whole body and tissue specific insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp and analysis of insulin induced PKBser473 phosphorylation. Whole body insulin sensitivity was decreased by all high fat diets. However, while insulin-stimulated glucose uptake by peripheral tissues was impaired by all high fat diets, hepatic insulin sensitivity was affected only by the stearate rich diets. This tissue-specific pattern of reduced insulin sensitivity was confirmed by similar impairment in insulin-induced phosphorylation of PKBser473 in both liver and skeletal muscle. CONCLUSION In C57Bl/6 mice, 5 weeks of a high fat diet rich in stearate induces a metabolic state favoring low oxidative metabolism, increased adiposity and whole body insulin resistance characterized by severe hepatic insulin resistance. These results indicate that dietary fatty acid composition per sé rather than dietary fat content determines insulin sensitivity in liver of high fat fed C57Bl/6 mice.
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Affiliation(s)
- Sjoerd Aa van den Berg
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
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Nascimento EBM, Snel M, Guigas B, van der Zon GCM, Kriek J, Maassen JA, Jazet IM, Diamant M, Ouwens DM. Phosphorylation of PRAS40 on Thr246 by PKB/AKT facilitates efficient phosphorylation of Ser183 by mTORC1. Cell Signal 2010; 22:961-7. [PMID: 20138985 DOI: 10.1016/j.cellsig.2010.02.002] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2009] [Revised: 01/18/2010] [Accepted: 02/01/2010] [Indexed: 01/25/2023]
Abstract
Type 2 diabetes is associated with alterations in protein kinase B (PKB/Akt) and mammalian target of rapamycin complex 1 (mTORC1) signalling. The proline-rich Akt substrate of 40-kDa (PRAS40) is a component of mTORC1, which has a regulatory function at the intersection of the PKB/Akt and mTORC1 signalling pathway. Phosphorylation of PRAS40-Thr246 by PKB/Akt, and PRAS40-Ser183 and PRAS40-Ser221 by mTORC1 results in dissociation from mTORC1, and its binding to 14-3-3 proteins. Although all phosphorylation sites within PRAS40 have been implicated in 14-3-3 binding, substitution of Thr246 by Ala alone is sufficient to abolish 14-3-3 binding under conditions of intact mTORC1 signalling. This suggests that phosphorylation of PRAS40-Thr246 may facilitate efficient phosphorylation of PRAS40 on its mTORC1-dependent sites. In the present study, we investigated the mechanism of PRAS40-Ser183 phosphorylation in response to insulin. Insulin promoted PRAS40-Ser183 phosphorylation after a euglycaemic-hyperinsulinaemic clamp in human skeletal muscle. The insulin-induced PRAS40-Ser183 phosphorylation was further evidenced in vivo in rat skeletal and cardiac muscle, and in vitro in A14 fibroblasts, 3T3L1 adipocytes and L6 myotubes. Inhibition of mTORC1 by rapamycin or amino acid deprivation partially abrogated insulin-mediated PRAS40-Ser183 phosphorylation in cultured cell lines. However, lowering insulin-induced PRAS40-Thr246 phosphorylation using wortmannin or palmitate in cell lines, or by feeding rats a high-fat diet, completely abolished insulin-mediated PRAS40-Ser183 phosphorylation. In addition, replacement of Thr246 by Ala reduced insulin-mediated PRAS40-Ser183 phosphorylation. We conclude that PRAS40-Ser183 is a component of insulin action, and that efficient phosphorylation of PRAS40-Ser183 by mTORC1 requires the phosphorylation of PRAS40-Thr246 by PKB/Akt.
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Affiliation(s)
- Emmani B M Nascimento
- Department of Molecular Cell Biology, Leiden University Medical Centre, Leiden, The Netherlands
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Abstract
Alterations in signalling via protein kinase B (PKB/Akt) and the mammalian target of rapamycin (mTOR) frequently occur in type 2 diabetes and various human malignancies. Proline-rich Akt substrate of 40-kDa (PRAS40) has a regulatory function at the intersection of these pathways. The interaction of PRAS40 with the mTOR complex 1 (mTORC1) inhibits the activity of mTORC1. Phosphorylation of PRAS40 by PKB/Akt and mTORC1 disrupts the binding between mTORC1 and PRAS40, and relieves the inhibitory constraint of PRAS40 on mTORC1 activity. This review summarizes the signalling pathways regulating PRAS40 phosphorylation, as well as the dual function of PRAS40 as substrate and inhibitor of mTORC1 in the physiological situation, and under pathological conditions, such as insulin resistance and cancer.
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Affiliation(s)
- Emmani B M Nascimento
- Department of Molecular Cell Biology, Section Signal Transduction and Ageing, Leiden University Medical Centre, Leiden, The Netherlands
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Mullen KL, Pritchard J, Ritchie I, Snook LA, Chabowski A, Bonen A, Wright D, Dyck DJ. Adiponectin resistance precedes the accumulation of skeletal muscle lipids and insulin resistance in high-fat-fed rats. Am J Physiol Regul Integr Comp Physiol 2009; 296:R243-51. [DOI: 10.1152/ajpregu.90774.2008] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
High-fat (HF) diets can induce insulin resistance (IR) by altering skeletal muscle lipid metabolism. An imbalance between fatty acid (FA) uptake and oxidation results in intramuscular lipid accumulation, which can impair the insulin-signaling cascade. Adiponectin (Ad) is an insulin-sensitizing adipokine known to stimulate skeletal muscle FA oxidation and reduce lipid accumulation. Evidence of Ad resistance has been shown in obesity and following chronic HF feeding and may contribute to lipid accumulation observed in these conditions. Whether Ad resistance precedes and is associated with the development of IR is unknown. We conducted a time course HF feeding trial for 3 days, 2 wk, or 4 wk to determine the onset of Ad resistance and identify the ensuing changes in lipid metabolism and insulin signaling leading to IR in skeletal muscle. Ad stimulated FA oxidation (+28%, P ≤ 0.05) and acetyl-CoA carboxylase phosphorylation (+34%, P ≤ 0.05) in control animals but failed to do so in any HF-fed group (i.e., as early as 3 days). By 2 wk, plasma membrane FA transporters and intramuscular diacylglycerol (DAG) and ceramide were increased, and insulin-stimulated phosphorylation of both protein kinase B and protein kinase B substrate 160 was blunted compared with control animals. After 4 wk of HF feeding, maximal insulin-stimulated glucose transport was impaired compared with control. Taken together, our results demonstrate that an early loss of Ad's stimulatory effect on FA oxidation precedes an increase in plasmalemmal FA transporters and the accumulation of intramuscular DAG and ceramide, blunted insulin signaling, and ultimately impaired maximal insulin-stimulated glucose transport in skeletal muscle induced by HF diets.
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Tabbi-Anneni I, Buchanan J, Cooksey RC, Abel ED. Captopril normalizes insulin signaling and insulin-regulated substrate metabolism in obese (ob/ob) mouse hearts. Endocrinology 2008; 149:4043-50. [PMID: 18450963 PMCID: PMC2488224 DOI: 10.1210/en.2007-1646] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The goal of this study was to determine whether inhibiting the renin-angiotensin system would restore insulin signaling and normalize substrate use in hearts from obese ob/ob mice. Mice were treated for 4 wk with Captopril (4 mg/kg x d). Circulating levels of free fatty acids, triglycerides, and insulin were measured and glucose tolerance tests performed. Rates of palmitate oxidation and glycolysis, oxygen consumption, and cardiac power were determined in isolated working hearts in the presence and absence of insulin, along with levels of phosphorylation of Akt and AMP-activated protein kinase (AMPK). Captopril treatment did not correct the hyperinsulinemia or impaired glucose tolerance in ob/ob mice. Rates of fatty acid oxidation were increased and glycolysis decreased in ob/ob hearts, and insulin did not modulate substrate use in hearts of ob/ob mice and did not increase Akt phosphorylation. Captopril restored the ability of insulin to regulate fatty acid oxidation and glycolysis in hearts of ob/ob mice, possibly by increasing Akt phosphorylation. Moreover, AMPK phosphorylation, which was increased in hearts of ob/ob mice, was normalized by Captopril treatment, suggesting that in addition to restoring insulin sensitivity, Captopril treatment improved myocardial energetics. Thus, angiotensin-converting enzyme inhibitors restore the responsiveness of ob/ob mouse hearts to insulin and normalizes AMPK activity independently of effects on systemic metabolic homeostasis.
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Affiliation(s)
- Imene Tabbi-Anneni
- Division of Endocrinology, Metabolism, and Diabetes, University of Utah School of Medicine, Salt Lake City, Utah 84112, USA
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Wang L, Harris TE, Lawrence JC. Regulation of proline-rich Akt substrate of 40 kDa (PRAS40) function by mammalian target of rapamycin complex 1 (mTORC1)-mediated phosphorylation. J Biol Chem 2008; 283:15619-27. [PMID: 18372248 DOI: 10.1074/jbc.m800723200] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The rapamycin-sensitive mammalian target of rapamycin (mTOR) complex 1 (mTORC1) contains mTOR, raptor, mLST8, and PRAS40 (proline-rich Akt substrate of 40 kDa). PRAS40 functions as a negative regulator when bound to mTORC1, and it dissociates from mTORC1 in response to insulin. PRAS40 has been demonstrated to be a substrate of mTORC1, and one phosphorylation site, Ser-183, has been identified. In this study, we used two-dimensional phosphopeptide mapping in conjunction with mutational analysis to show that in addition to Ser-183, mTORC1 also phosphorylates Ser-212 and Ser-221 in PRAS40 when assayed in vitro. Mutation of all three residues to Ala markedly reduces mTORC1-mediated phosphorylation of PRAS40 in vitro. All three sites were confirmed to be phosphorylated in vivo by [(32)P]orthophosphate labeling and peptide mapping. Phosphorylation of Ser-221 and Ser-183 but not Ser-212 is sensitive to rapamycin treatment. Furthermore, we demonstrate that mutation of Ser-221 to Ala reduces the interaction with 14-3-3 to the same extent as mutation of Thr-246, the Akt/protein kinase B-phosphorylated site. We also find that mutation of Ser-221 to Ala increases the inhibitory activity of PRAS40 toward mTORC1. We propose that after mTORC1 kinase activation by upstream regulators, PRAS40 is phosphorylated directly by mTOR, thus contributing to the relief of PRAS40-mediated substrate competition.
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Affiliation(s)
- Lifu Wang
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908, USA.
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Jazet IM, Schaart G, Gastaldelli A, Ferrannini E, Hesselink MK, Schrauwen P, Romijn JA, Maassen JA, Pijl H, Ouwens DM, Meinders AE. Loss of 50% of excess weight using a very low energy diet improves insulin-stimulated glucose disposal and skeletal muscle insulin signalling in obese insulin-treated type 2 diabetic patients. Diabetologia 2008; 51:309-19. [PMID: 18080107 DOI: 10.1007/s00125-007-0862-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Accepted: 09/13/2007] [Indexed: 12/25/2022]
Abstract
AIMS/HYPOTHESIS Both energy restriction (ER) per se and weight loss improve glucose metabolism in obese insulin-treated type 2 diabetic patients. Short-term ER decreases basal endogenous glucose production (EGP) but not glucose disposal. In contrast the blood glucose-lowering mechanism of long-term ER with substantial weight loss has not been fully elucidated. The aim of this study was to investigate the effect of loss of 50% of excess weight [50% excess weight reduction (EWR)] on EGP, whole-body insulin sensitivity and the disturbed myocellular insulin-signalling pathway in ten obese insulin-treated type 2 diabetic patients. METHODS A euglycaemic-hyperinsulinaemic clamp with stable isotopes ([6,6-(2)H2]glucose and [2H5]glycerol) combined with skeletal muscle biopsies was performed during a very low energy diet (VLED; 1,883 kJ/day) on day 2 and again after 50% EWR. Oral blood glucose-lowering agents and insulin were discontinued 3 weeks prior to the VLED and at the start of the VLED, respectively. RESULTS Loss of 50% EWR (20.3+/-2.2 kg from day 2 to day of 50% EWR) normalised basal EGP and improved insulin sensitivity, especially insulin-stimulated glucose disposal (18.8+/-2.0 to 39.1+/-2.8 micromol kg fat-free mass(-1) min(-1), p=0.001). The latter was accompanied by improved insulin signalling at the level of the recently discovered protein kinase B/Akt substrates AS160 and PRAS40 along with a decrease in intramyocellular lipid (IMCL) content. CONCLUSIONS/INTERPRETATION Considerable weight loss in obese, insulin-treated type 2 diabetic patients normalises basal EGP and improves insulin sensitivity resulting from an improvement in insulin signal transduction in skeletal muscle. The decrease in IMCL might contribute to this effect.
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Affiliation(s)
- I M Jazet
- Department of General Internal Medicine, C4-r-73, Leiden University Medical Centre, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
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Fornoni A, Pileggi A, Molano RD, Sanabria NY, Tejada T, Gonzalez-Quintana J, Ichii H, Inverardi L, Ricordi C, Pastori RL. Inhibition of c-jun N terminal kinase (JNK) improves functional beta cell mass in human islets and leads to AKT and glycogen synthase kinase-3 (GSK-3) phosphorylation. Diabetologia 2008; 51:298-308. [PMID: 18066521 DOI: 10.1007/s00125-007-0889-4] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Accepted: 10/26/2007] [Indexed: 12/31/2022]
Abstract
AIMS/HYPOTHESIS Activation of c-jun N-terminal kinase (JNK) has been described in islet isolation and engraftment, making JNK a key target in islet transplantation. The objective of this study was to investigate if JNK inhibition with a cell-permeable TAT peptide inhibitor (L-JNKI) protects functional beta cell mass in human islets and affects AKT and its substrates in islet cells. METHODS The effect of L-JNKI (10 micromol/l) on islet count, mitochondrial membrane potential, glucose-stimulated insulin release and phosphorylation of both AKT and its substrates, as well as on reversal of diabetes in immunodeficient diabetic Nu/Nu mice was studied. RESULTS In vitro, L-JNKI reduced the islet loss in culture and protected from cell death caused by acute cytokine exposure. In vivo, treatment of freshly isolated human islets and diabetic Nu/Nu mice recipients of such islets resulted in improved functional beta cell mass. We showed that L-JNKI activates AKT and downregulates glycogen synthase kinase-3 beta (GSK-3B) in human islets exposed to cytokines, while other AKT substrates were unaffected, suggesting that a specific AKT/GSK-3B regulation by L-JNKI may represent one of its mechanisms of cytoprotection. CONCLUSIONS/INTERPRETATION In conclusion, we have demonstrated that targeting JNK in human pancreatic islets results in improved functional beta cell mass and in the regulation of AKT/GSK3B activity.
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Affiliation(s)
- A Fornoni
- Diabetes Research Institute, University of Miami Miller School of Medicine, 1450 NW 10th Avenue, Miami, FL 33136, USA.
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Yu F, Narasimhan P, Saito A, Liu J, Chan PH. Increased expression of a proline-rich Akt substrate (PRAS40) in human copper/zinc-superoxide dismutase transgenic rats protects motor neurons from death after spinal cord injury. J Cereb Blood Flow Metab 2008; 28:44-52. [PMID: 17457363 PMCID: PMC2167854 DOI: 10.1038/sj.jcbfm.9600501] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The serine-threonine kinase, Akt, plays an important role in the cell survival signaling pathway. A proline-rich Akt substrate, PRAS40, has been characterized, and an increase in phospho-PRAS40 (pPRAS40) is neuroprotective after transient focal cerebral ischemia. However, the involvement of PRAS40 in the cell death/survival pathway after spinal cord injury (SCI) is unclear. Liposome-mediated PRAS40 transfection was performed to study whether overexpression of pPRAS40 is neuroprotective. We further examined the expression of pPRAS40 after SCI by immunohistochemistry and Western blot using copper/zinc-superoxide dismutase (SOD1) transgenic (Tg) rats and wild-type (Wt) littermates. We then examined the relationship between PRAS40 and Akt by injection of LY294002, a phosphatidylinositol 3-kinase (PI3K) pathway inhibitor, or Akt inhibitor IV, a compound that inhibits Akt activation after SCI. Our data demonstrated that increased pPRAS40 resulted in survival of more motor neurons compared with control complementary DNA transfection. Phosphorylated PRAS40 increased in the Wt rats after SCI, whereas there was a greater and prolonged increase in the SOD1 Tg rats. Coimmunoprecipitation showed that binding of pPRAS40 with 14-3-3 increased 1 day after SCI in the Wt rats, whereas there was a significant increase in the Tg rats. The inhibitor studies showed that phospho-Akt and pPRAS40 were decreased after injection of LY294002 or Akt inhibitor IV. We conclude that an increase in pPRAS40 by transfection after SCI results in survival of motor neurons, and overexpression of SOD1 in the Tg rats results in an increase in endogenous pPRAS40 and a decrease in motor neuron death through the PI3K/Akt pathway.
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Affiliation(s)
- Fengshan Yu
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, California 94305-5487, USA
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Lauritzen HPM, Ploug T, Ai H, Donsmark M, Prats C, Galbo H. Denervation and high-fat diet reduce insulin signaling in T-tubules in skeletal muscle of living mice. Diabetes 2008; 57:13-23. [PMID: 17914033 DOI: 10.2337/db07-0516] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Insulin stimulates muscle glucose transport by translocation of GLUT4 to sarcolemma and T-tubules. Despite muscle glucose uptake playing a major role in insulin resistance and type 2 diabetes, the temporal and spatial changes in insulin signaling and GLUT4 translocation during these conditions are not well described. RESEARCH DESIGN AND METHODS We used time-lapse confocal imaging of green fluorescent protein (GFP) ADP-ribosylation factor nucleotide-binding site opener (ARNO) (evaluation of phosphatidylinositide 3-kinase activation) and GLUT4-GFP-transfected quadriceps muscle in living, anesthetized mice either muscle denervated or high-fat fed. T-tubules were visualized with sulforhodamine B dye. In incubated muscle, glucose transport was measured by 2-deoxy-D-[(3)H]-glucose uptake, and functional detubulation was carried out by osmotic shock. Muscle fibers were immunostained for insulin receptors. RESULTS Denervation and high-fat diet reduced insulin-mediated glucose transport. In denervated muscle, insulin-stimulated phosphatidylinositol 3,4,5 P(3) (PIP3) production was abolished in T-tubules, while PIP3 production at sarcolemma was increased 2.6-fold. Correspondingly, GLUT4-GFP translocation to T-tubules was abolished, while translocation to sarcolemma was increased 2.3-fold. In high fat-fed mice, a approximately 65% reduction in both insulin-induced T-tubular PIP3 production and GLUT4-GFP translocation was seen. Sarcolemma was less affected, with reductions of approximately 40% in PIP3 production and approximately 15% in GLUT4-GFP translocation. Access to T-tubules was not compromised, and insulin receptor distribution in sarcolemma and T-tubules was unaffected by denervation or high-fat feeding. Detubulation of normal muscle reduced basal and abolished insulin-induced glucose transport. CONCLUSIONS Our findings demonstrate, for the first time, that impaired insulin signaling and GLUT4 translocation is compartmentalized in muscle and primarily localized to T-tubules and not sarcolemma during insulin resistance.
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Affiliation(s)
- Hans P M Lauritzen
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA.
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Korsheninnikova E, Voshol PJ, Baan B, van der Zon GCM, Havekes LM, Romijn JA, Maassen JA, Ouwens DM. Dynamics of insulin signalling in liver during hyperinsulinemic euglycaemic clamp conditions in vivo and the effects of high-fat feeding in male mice. Arch Physiol Biochem 2007; 113:173-85. [PMID: 18158643 DOI: 10.1080/13813450701669084] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Insulin is an important regulator of hepatic carbohydrate, lipid, and protein metabolism, and the regulation of these processes by insulin is disturbed under conditions of insulin resistance and type 2 diabetes. Despite these alterations, the impact of insulin resistance on insulin signalling in the liver is not well defined. Variations in time and dose of insulin stimulation as well as plasma glucose levels may underlie this. The present study aimed at determining the dynamics of activation of hepatic insulin signalling in vivo at insulin concentrations resembling those achieved after a meal, and addressing the effects of high-fat feeding. An unexpected finding of this study was the biphasic activation pattern of the IRS-PI3K-PKB/Akt pathway. Our findings indicate that the first burst of activation contributes to regulation of glucose metabolism. The physiological function of the second peak is still unknown, but may involve regulation of protein synthesis. Finally, high-fat feeding caused hepatic insulin resistance, as illustrated by a reduced suppression of hepatic glucose production. A sustained increased phosphorylation of the serine/threonine kinases p70S6kinase and Jun N-terminal kinase in the absence of insulin may underlie the abrogated phosphorylation of the IRS proteins and their downstream targets.
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Affiliation(s)
- E Korsheninnikova
- Departments of Molecular Cell Biology, Leiden University Medical Centre, Leiden, The Netherlands
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41
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Ouwens DM, Diamant M, Fodor M, Habets DDJ, Pelsers MMAL, El Hasnaoui M, Dang ZC, van den Brom CE, Vlasblom R, Rietdijk A, Boer C, Coort SLM, Glatz JFC, Luiken JJFP. Cardiac contractile dysfunction in insulin-resistant rats fed a high-fat diet is associated with elevated CD36-mediated fatty acid uptake and esterification. Diabetologia 2007; 50:1938-1948. [PMID: 17639306 PMCID: PMC2039861 DOI: 10.1007/s00125-007-0735-8] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Accepted: 05/22/2007] [Indexed: 11/29/2022]
Abstract
AIMS/HYPOTHESIS Changes in cardiac substrate utilisation leading to altered energy metabolism may underlie the development of diabetic cardiomyopathy. We studied cardiomyocyte substrate uptake and utilisation and the role of the fatty acid translocase CD36 in relation to in vivo cardiac function in rats fed a high-fat diet (HFD). METHODS Rats were exposed to an HFD or a low-fat diet (LFD). In vivo cardiac function was monitored by echocardiography. Substrate uptake and utilisation were determined in isolated cardiomyocytes. RESULTS Feeding an HFD for 8 weeks induced left ventricular dilation in the systolic phase and decreased fractional shortening and the ejection fraction. Insulin-stimulated glucose uptake and proline-rich Akt substrate 40 phosphorylation were 41% (p < 0.001) and 45% (p < 0.05) lower, respectively, in cardiomyocytes from rats on the HFD. However, long-chain fatty acid (LCFA) uptake was 1.4-fold increased (p < 0.001) and LCFA esterification into triacylglycerols and phospholipids was increased 1.4- and 1.5-fold, respectively (both p < 0.05), in cardiomyocytes from HFD compared with LFD hearts. In the presence of the CD36 inhibitor sulfo-N-succinimidyloleate, LCFA uptake and esterification were similar in LFD and HFD cardiomyocytes. In HFD hearts CD36 was relocated to the sarcolemma, and basal phosphorylation of a mediator of CD36-trafficking, i.e. protein kinase B (PKB/Akt), was increased. CONCLUSIONS/INTERPRETATION Feeding rats an HFD induced cardiac contractile dysfunction, which was accompanied by the relocation of CD36 to the sarcolemma, and elevated basal levels of phosphorylated PKB/Akt. The permanent presence of CD36 at the sarcolemma resulted in enhanced rates of LCFA uptake and myocardial triacylglycerol accumulation, and may contribute to the development of insulin resistance and diabetic cardiomyopathy.
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Affiliation(s)
- D M Ouwens
- Department of Molecular Cell Biology, Section of Signal Transduction and Ageing, Leiden University Medical Centre, Postzone S1-P, P.O. Box 9600, NL-2300, RC Leiden, The Netherlands.
| | - M Diamant
- Department of Endocrinology, Diabetes Centre, VU University Medical Centre, Amsterdam, the Netherlands
| | - M Fodor
- Department of Anatomy and Embryology/Central Animal Facility, Leiden University Medical Centre, Leiden, the Netherlands
| | - D D J Habets
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - M M A L Pelsers
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - M El Hasnaoui
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - Z C Dang
- Department of Endocrinology, Diabetes Centre, VU University Medical Centre, Amsterdam, the Netherlands
- Laboratory for Physiology, VU University Medical Centre, Amsterdam, the Netherlands
| | - C E van den Brom
- Department of Molecular Cell Biology, Section of Signal Transduction and Ageing, Leiden University Medical Centre, Postzone S1-P, P.O. Box 9600, NL-2300, RC Leiden, The Netherlands
- Department of Endocrinology, Diabetes Centre, VU University Medical Centre, Amsterdam, the Netherlands
- Laboratory for Physiology, VU University Medical Centre, Amsterdam, the Netherlands
| | - R Vlasblom
- Department of Molecular Cell Biology, Section of Signal Transduction and Ageing, Leiden University Medical Centre, Postzone S1-P, P.O. Box 9600, NL-2300, RC Leiden, The Netherlands
- Department of Endocrinology, Diabetes Centre, VU University Medical Centre, Amsterdam, the Netherlands
- Laboratory for Physiology, VU University Medical Centre, Amsterdam, the Netherlands
| | - A Rietdijk
- Department of Molecular Cell Biology, Section of Signal Transduction and Ageing, Leiden University Medical Centre, Postzone S1-P, P.O. Box 9600, NL-2300, RC Leiden, The Netherlands
| | - C Boer
- Laboratory for Physiology, VU University Medical Centre, Amsterdam, the Netherlands
| | - S L M Coort
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - J F C Glatz
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - J J F P Luiken
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
- Department of Biochemical Physiology and Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
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Alkhateeb H, Chabowski A, Glatz JFC, Luiken JFP, Bonen A. Two phases of palmitate-induced insulin resistance in skeletal muscle: impaired GLUT4 translocation is followed by a reduced GLUT4 intrinsic activity. Am J Physiol Endocrinol Metab 2007; 293:E783-93. [PMID: 17550999 DOI: 10.1152/ajpendo.00685.2006] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examined, in soleus muscle, the effects of prolonged palmitate exposure (0, 6, 12, 18 h) on insulin-stimulated glucose transport, intramuscular lipid accumulation and oxidation, activation of selected insulin-signaling proteins, and the insulin-stimulated translocation of GLUT4. Insulin-stimulated glucose transport was progressively reduced after 6 h (-33%), 12 h (-66%), and 18 h (-89%) of palmitate exposure. These decrements were closely associated with concurrent reductions in palmitate oxidation at 6 h (-40%), 12 h (-60%), and 18 h (-67%). In contrast, intramuscular ceramide (+24%) and diacylglycerol (+32%) concentrations, insulin-stimulated AS160 (-36%) and PRAS40 (-33%) phosphorylations, and Akt (-40%), PKCtheta (-50%), and GLUT4 translocation (-40%) to the plasma membrane were all maximally altered within the first 6 h of palmitate treatment. No further changes were observed in any of these parameters after 12 and 18 h of palmitate exposure. Thus, the intrinsic activity of GLUT4 was markedly reduced after 12 and 18 h of palmitate treatment. During this reduced GLUT4 intrinsic activity phase at 12 and 18 h, the reduction in glucose transport was twofold greater compared with the early phase (< or =6 h), when only GLUT4 translocation was impaired. Our study indicates that palmitate-induced insulin resistance is provoked by two distinct mechanisms: 1) an early phase (< or =6 h), during which lipid-mediated impairments in insulin signaling and GLUT4 translocation reduce insulin-stimulated glucose transport, followed by 2) a later phase (12 and 18 h), during which the intrinsic activity of GLUT4 is markedly reduced independently of any further alterations in intramuscular lipid accumulation, insulin signaling and GLUT4 translocation.
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Affiliation(s)
- Hakam Alkhateeb
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
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Oshiro N, Takahashi R, Yoshino KI, Tanimura K, Nakashima A, Eguchi S, Miyamoto T, Hara K, Takehana K, Avruch J, Kikkawa U, Yonezawa K. The proline-rich Akt substrate of 40 kDa (PRAS40) is a physiological substrate of mammalian target of rapamycin complex 1. J Biol Chem 2007; 282:20329-39. [PMID: 17517883 PMCID: PMC3199301 DOI: 10.1074/jbc.m702636200] [Citation(s) in RCA: 256] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The proline-rich Akt substrate of 40 kilodaltons (PRAS40) was identified as a raptor-binding protein that is phosphorylated directly by mammalian target of rapamycin (mTOR) complex 1 (mTORC1) but not mTORC2 in vitro, predominantly at PRAS40 (Ser(183)). The binding of S6K1 and 4E-BP1 to raptor requires a TOR signaling (TOS) motif, which contains an essential Phe followed by four alternating acidic and small hydrophobic amino acids. PRAS40 binding to raptor was severely inhibited by mutation of PRAS40 (Phe(129) to Ala). Immediately carboxyl-terminal to Phe(129) are two small hydrophobic amino acid followed by two acidic residues. PRAS40 binding to raptor was also abolished by mutation of the major mTORC1 phosphorylation site, Ser(183), to Asp. PRAS40 (Ser(183)) was phosphorylated in intact cells; this phosphorylation was inhibited by rapamycin, by 2-deoxyglucose, and by overexpression of the tuberous sclerosis complex heterodimer. PRAS40 (Ser(183)) phosphorylation was also inhibited reversibly by withdrawal of all or of only the branched chain amino acids; this inhibition was reversed by overexpression of the Rheb GTPase. Overexpressed PRAS40 suppressed the phosphorylation of S6K1 and 4E-BP1 at their rapamycin-sensitive phosphorylation sites, and reciprocally, overexpression of S6K1 or 4E-BP1 suppressed phosphorylation of PRAS40 (Ser(183)) and its binding to raptor. RNA interference-induced depletion of PRAS40 enhanced the amino acid-stimulated phosphorylation of both S6K1 and 4E-BP1. These results establish PRAS40 as a physiological mTORC1 substrate that contains a variant TOS motif. Moreover, they indicate that the ability of raptor to bind endogenous substrates is limiting for the activity of mTORC1 in vivo and is therefore a potential locus of regulation.
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Affiliation(s)
- Noriko Oshiro
- Biosignal Research Center, Kobe University, Kobe 657-8501, Japan
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