1
|
Effects of PKB/Akt inhibitors on insulin-stimulated lipogenesis and phosphorylation state of lipogenic enzymes in white adipose tissue. Biochem J 2020; 477:1373-1389. [PMID: 32215608 DOI: 10.1042/bcj20190788] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 03/24/2020] [Accepted: 03/26/2020] [Indexed: 11/17/2022]
Abstract
We investigated acute effects of two allosteric protein kinase B (PKB) inhibitors, MK-2206 and Akti-1/2, on insulin-stimulated lipogenesis in rat epididymal adipocytes incubated with fructose as carbohydrate substrate. In parallel, the phosphorylation state of lipogenic enzymes in adipocytes and incubated epididymal fat pads was monitored by immunoblotting. Preincubation of rat epididymal adipocytes with PKB inhibitors dose-dependently inhibited the following: insulin-stimulated lipogenesis, increased PKB Ser473 phosphorylation, increased PKB activity and decreased acetyl-CoA carboxylase (ACC) Ser79 phosphorylation. In contrast, the effect of insulin to decrease the phosphorylation of pyruvate dehydrogenase (PDH) at Ser293 and Ser300 was not abolished by PKB inhibition. Insulin treatment also induced ATP-citrate lyase (ACL) Ser454 phosphorylation, but this effect was less sensitive to PKB inhibitors than ACC dephosphorylation by insulin. In incubated rat epididymal fat pads, Akti-1/2 treatment reversed insulin-induced ACC dephosphorylation, while ACL phosphorylation by insulin was maintained. ACL and ACC purified from white adipose tissue were poor substrates for PKBα in vitro. However, effects of wortmannin and torin, along with Akti-1/2 and MK-2206, on recognized PKB target phosphorylation by insulin were similar to their effects on insulin-induced ACL phosphorylation, suggesting that PKB could be the physiological kinase for ACL phosphorylation by insulin. In incubated epididymal fat pads from wild-type versus ACC1/2 S79A/S212A knockin mice, effects of insulin to increase lipogenesis from radioactive fructose or from radioactive acetate were reduced but not abolished. Together, the results support a key role for PKB in mediating insulin-stimulated lipogenesis by decreasing ACC phosphorylation, but not by decreasing PDH phosphorylation.
Collapse
|
2
|
Barbosa AM, Martel F. Targeting Glucose Transporters for Breast Cancer Therapy: The Effect of Natural and Synthetic Compounds. Cancers (Basel) 2020; 12:cancers12010154. [PMID: 31936350 PMCID: PMC7016663 DOI: 10.3390/cancers12010154] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 01/06/2020] [Accepted: 01/07/2020] [Indexed: 02/07/2023] Open
Abstract
Reprogramming of cellular energy metabolism is widely accepted to be a cancer hallmark. The deviant energetic metabolism of cancer cells-known as the Warburg effect-consists in much higher rates of glucose uptake and glycolytic oxidation coupled with the production of lactic acid, even in the presence of oxygen. Consequently, cancer cells have higher glucose needs and thus display a higher sensitivity to glucose deprivation-induced death than normal cells. So, inhibitors of glucose uptake are potential therapeutic targets in cancer. Breast cancer is the most commonly diagnosed cancer and a leading cause of cancer death in women worldwide. Overexpression of facilitative glucose transporters (GLUT), mainly GLUT1, in breast cancer cells is firmly established, and the consequences of GLUT inhibition and/or knockout are under investigation. Herein we review the compounds, both of natural and synthetic origin, found to interfere with uptake of glucose by breast cancer cells, and the consequences of interference with that mechanism on breast cancer cell biology. We will also present data where the interaction with GLUT is exploited in order to increase the efficiency or selectivity of anticancer agents, in breast cancer cells.
Collapse
Affiliation(s)
- Ana M. Barbosa
- Instituto de Ciências Biomédicas Abel Salazar, University of Porto, 4169-007 Porto, Portugal;
| | - Fátima Martel
- Unit of Biochemistry, Department of Biomedicine, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal
- Instituto de Investigação e Inovação em Saúde, University of Porto, 4200-135 Porto, Portugal
- Correspondence: ; Tel.: +351-22-042-6654
| |
Collapse
|
3
|
Krycer JR, Elkington SD, Diaz-Vegas A, Cooke KC, Burchfield JG, Fisher-Wellman KH, Cooney GJ, Fazakerley DJ, James DE. Mitochondrial oxidants, but not respiration, are sensitive to glucose in adipocytes. J Biol Chem 2020; 295:99-110. [PMID: 31744882 PMCID: PMC6952605 DOI: 10.1074/jbc.ra119.011695] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Indexed: 11/06/2022] Open
Abstract
Insulin action in adipose tissue is crucial for whole-body glucose homeostasis, with insulin resistance being a major risk factor for metabolic diseases such as type 2 diabetes. Recent studies have proposed mitochondrial oxidants as a unifying driver of adipose insulin resistance, serving as a signal of nutrient excess. However, neither the substrates for nor sites of oxidant production are known. Because insulin stimulates glucose utilization, we hypothesized that glucose oxidation would fuel respiration, in turn generating mitochondrial oxidants. This would impair insulin action, limiting further glucose uptake in a negative feedback loop of "glucose-dependent" insulin resistance. Using primary rat adipocytes and cultured 3T3-L1 adipocytes, we observed that insulin increased respiration, but notably this occurred independently of glucose supply. In contrast, glucose was required for insulin to increase mitochondrial oxidants. Despite rising to similar levels as when treated with other agents that cause insulin resistance, glucose-dependent mitochondrial oxidants failed to cause insulin resistance. Subsequent studies revealed a temporal relationship whereby mitochondrial oxidants needed to increase before the insulin stimulus to induce insulin resistance. Together, these data reveal that (a) adipocyte respiration is principally fueled from nonglucose sources; (b) there is a disconnect between respiration and oxidative stress, whereby mitochondrial oxidant levels do not rise with increased respiration unless glucose is present; and (c) mitochondrial oxidative stress must precede the insulin stimulus to cause insulin resistance, explaining why short-term, insulin-dependent glucose utilization does not promote insulin resistance. These data provide additional clues to mechanistically link nutrient excess to adipose insulin resistance.
Collapse
Affiliation(s)
- James R Krycer
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Sarah D Elkington
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Alexis Diaz-Vegas
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Kristen C Cooke
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - James G Burchfield
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Kelsey H Fisher-Wellman
- East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27834
| | - Gregory J Cooney
- Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia; Sydney Medical School, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Daniel J Fazakerley
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia; Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, United Kingdom.
| | - David E James
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia; Charles Perkins Centre, The University of Sydney, Sydney, New South Wales 2006, Australia; Sydney Medical School, The University of Sydney, Sydney, New South Wales 2006, Australia.
| |
Collapse
|
4
|
Huy H, Song HY, Kim MJ, Kim WS, Kim DO, Byun JE, Lee J, Park YJ, Kim TD, Yoon SR, Choi EJ, Lee CH, Noh JY, Jung H, Choi I. TXNIP regulates AKT-mediated cellular senescence by direct interaction under glucose-mediated metabolic stress. Aging Cell 2018; 17:e12836. [PMID: 30168649 PMCID: PMC6260918 DOI: 10.1111/acel.12836] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Revised: 07/16/2018] [Accepted: 08/02/2018] [Indexed: 12/11/2022] Open
Abstract
Aging is associated with an inevitable and universal loss of cell homeostasis and restricts an organism's lifespan by an increased susceptibility to diseases and tissue degeneration. The glucose uptake associated with producing energy for cell survival is one of the major causes of ROS production under physiological conditions. However, the overall mechanisms by which glucose uptake results in cellular senescence remain mysterious. In this study, we found that TXNIP deficiency accelerated the senescent phenotypes of MEF cells under high glucose condition. TXNIP‐/‐ MEF cells showed greater induced glucose uptake and ROS levels than wild‐type cells, and N‐acetylcysteine (NAC) treatment rescued the cellular senescence of TXNIP‐/‐ MEF cells. Interestingly, TXNIP‐/‐ MEF cells showed continuous activation of AKT during long‐term subculture, and AKT signaling inhibition completely blocked the cellular senescence of TXNIP‐/‐ MEF cells. In addition, we found that TXNIP interacted with AKT via the PH domain of AKT, and their interaction was increased by high glucose or H2O2 treatment. The inhibition of AKT activity by TXNIP was confirmed using western blotting and an in vitro kinase assay. TXNIP deficiency in type 1 diabetes mice (Akita) efficiently decreased the blood glucose levels and finally increased mouse survival. However, in normal mice, TXNIP deficiency induced metabolic aging of mice and cellular senescence of kidney cells by inducing AKT activity and aging‐associated gene expression. Altogether, these results suggest that TXNIP regulates cellular senescence by inhibiting AKT pathways via a direct interaction under conditions of glucose‐derived metabolic stress.
Collapse
Affiliation(s)
- Hangsak Huy
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
- Department of Functional Genomics; University of Science and Technology (UST); Daejeon Korea
| | - Hae Young Song
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
| | - Mi Jeong Kim
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
| | - Won Sam Kim
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
| | - Dong Oh Kim
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
| | - Jae-Eun Byun
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
- Department of Biochemistry, School of Life Sciences; Chungbuk National University; Cheongju Korea
| | - Jungwoon Lee
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
| | - Young-Jun Park
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
- Department of Functional Genomics; University of Science and Technology (UST); Daejeon Korea
| | - Tae-Don Kim
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
- Department of Functional Genomics; University of Science and Technology (UST); Daejeon Korea
| | - Suk Ran Yoon
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
- Department of Functional Genomics; University of Science and Technology (UST); Daejeon Korea
| | - Eun-Ji Choi
- Department of Hematology, Asan Medical Center; University of Ulsan College of Medicine; Seoul Korea
| | - Chul-Ho Lee
- Laboratory Animal Resource Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
| | - Ji-Yoon Noh
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
| | - Haiyoung Jung
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
- Department of Functional Genomics; University of Science and Technology (UST); Daejeon Korea
| | - Inpyo Choi
- Immunotherapy Convergence Research Center; Korea Research Institute of Bioscience and Biotechnology (KRIBB); Daejeon Korea
- Department of Functional Genomics; University of Science and Technology (UST); Daejeon Korea
| |
Collapse
|
5
|
Kunjithapatham R, Ganapathy-Kanniappan S. GAPDH with NAD +-binding site mutation competitively inhibits the wild-type and affects glucose metabolism in cancer. Biochim Biophys Acta Gen Subj 2018; 1862:2555-2563. [PMID: 30077773 DOI: 10.1016/j.bbagen.2018.08.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 07/26/2018] [Accepted: 08/01/2018] [Indexed: 12/12/2022]
Abstract
BACKGROUND Rapid utilization of glucose is a metabolic signature of majority of cancers, hence enzymes of the glycolytic pathway remain attractive therapeutic targets. Recent reports have shown that targeting the glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), an abundant, ubiquitous multifunctional protein frequently upregulated in cancer, affects cancer progression. Here, we report that a catalytically-deficient mutant-GAPDH competitively inhibits the wild-type, and disrupts glucose metabolism in cancer cells. METHODS Using site-directed mutagenesis, the human GAPDH clone was mutated at one of the NAD+-binding sites, (i.e.) arginine (R13) and isoleucine (I14) to glutamine (Q13) and phenylalanine (F14), respectively. The inhibitory role of the mutant-GAPDH, and its effect on energy metabolism and cancer phenotype was determined using in vitro and in vivo models of cancer. RESULTS The enzymatically-dysfunctional mutant-GAPDH competitively inhibited the wild-type GAPDH in a cell-free system. In cancer cells, ectopic expression of the mutant-GAPDH, but not the wild-type, inhibited the glycolytic capacity of cellular-GAPDH, and led to the induction of metabolic stress accompanied by a sharp decline in glucose-uptake. Furthermore, expression of mutant-GAPDH affected cancer growth in vitro and in vivo. Mechanistically, structural analysis by bioinformatics revealed that the mutations at the NAD+-binding site altered the solvent-accessibility that perhaps affected the functionality of mutant-GAPDH. CONCLUSION Mutant-GAPDH affects the enzymatic function of cellular-GAPDH and disrupts energy metabolism. GENERAL SIGNIFICANCE Our findings demonstrate that a minimal mutation at the NAD+-binding site is sufficient to generate a competitive but dysfunctional GAPDH, and its ectopic expression inhibits the wild-type to disrupt glycolysis.
Collapse
Affiliation(s)
- Rani Kunjithapatham
- The Division of Interventional Radiology, Russell H. Morgan Department of Radiology & Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Shanmugasundaram Ganapathy-Kanniappan
- The Division of Interventional Radiology, Russell H. Morgan Department of Radiology & Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| |
Collapse
|
6
|
Gajendiran P, Vega LI, Itoh K, Sesaki H, Vakili MR, Lavasanifar A, Hong K, Mezey E, Ganapathy-Kanniappan S. Elevated mitochondrial activity distinguishes fibrogenic hepatic stellate cells and sensitizes for selective inhibition by mitotropic doxorubicin. J Cell Mol Med 2018; 22:2210-2219. [PMID: 29397578 PMCID: PMC5867155 DOI: 10.1111/jcmm.13501] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 11/18/2017] [Indexed: 12/17/2022] Open
Abstract
Activation of hepatic stellate cells (HSCs) is an integral component of the wound‐healing process in liver injury/inflammation. However, uncontrolled activation of HSCs leads to constant secretion of collagen‐rich extracellular matrix (ECM) proteins, resulting in liver fibrosis. The enhanced ECM synthesis/secretion demands an uninterrupted supply of intracellular energy; however, there is a paucity of data on the bioenergetics, particularly the mitochondrial (mito) metabolism of fibrogenic HSCs. Here, using human and rat HSCs in vitro, we show that the mito‐respiration, mito‐membrane potential (Δψm) and cellular ‘bioenergetic signature’ distinguish fibrogenic HSCs from normal, less‐active HSCs. Ex vivo, HSCs from mouse and rat models of liver fibrosis further confirmed the altered ‘bioenergetic signature’ of fibrogenic HSCs. Importantly, the distinctive elevation in mito‐Δψm sensitized fibrogenic HSCs for selective inhibition by mitotropic doxorubicin while normal, less‐active HSCs and healthy human primary hepatocytes remained minimally affected if not, unaffected. Thus, the increased mito‐Δψm may provide an opportunity to selectively target fibrogenic HSCs in liver fibrosis.
Collapse
Affiliation(s)
- Priya Gajendiran
- Division of Interventional Radiology, Russell H. Morgan Department of Radiology & Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Leonel Iglesias Vega
- Division of Interventional Radiology, Russell H. Morgan Department of Radiology & Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Kie Itoh
- Department of Cell Biology, School of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Hiromi Sesaki
- Department of Cell Biology, School of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Mohammad Reza Vakili
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada
| | - Afsaneh Lavasanifar
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada
| | - Kelvin Hong
- Division of Interventional Radiology, Russell H. Morgan Department of Radiology & Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Esteban Mezey
- Division of Gastroenterology and Hepatology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Shanmugasundaram Ganapathy-Kanniappan
- Division of Interventional Radiology, Russell H. Morgan Department of Radiology & Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| |
Collapse
|
7
|
A maternal high-fat, high-sucrose diet alters insulin sensitivity and expression of insulin signalling and lipid metabolism genes and proteins in male rat offspring: effect of folic acid supplementation. Br J Nutr 2017; 118:580-588. [PMID: 29056104 DOI: 10.1017/s0007114517002501] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A maternal high-fat, high-sucrose (HFS) diet alters offspring glucose and lipid homoeostasis through unknown mechanisms and may be modulated by folic acid. We investigated the effect of a maternal HFS diet on glucose homoeostasis, expression of genes and proteins associated with insulin signalling and lipid metabolism and the effect of prenatal folic acid supplementation (HFS/F) in male rat offspring. Pregnant Sprague-Dawley rats were randomly fed control (CON), HFS or HFS/F diets. Offspring were weaned on CON; at postnatal day 70, fasting plasma insulin and glucose and liver and skeletal muscle gene and protein expression were measured. Treatment effects were assessed by one-way ANOVA. Maternal HFS diet induced higher fasting glucose in offspring v. HFS/F (P=0·027) and down-regulation (P<0·05) of genes coding for v-Akt murine thymoma viral oncogene homolog 2, resistin and v-Raf-1 murine leukaemia viral oncogene homolog 1 (Raf1) in offspring skeletal muscle and acetyl-CoA carboxylase (Acaca), fatty acid synthase and phosphatidylinositol-4,5-biphosphate 3-kinase, catalytic subunit β in offspring liver. Skeletal muscle neuropeptide Y and hepatic Kruppel-like factor 10 were up-regulated in HFS v. CON offspring (P<0·05). Compared with CON, Acaca and Raf1 protein expression levels were significantly lower in HFS offspring. Maternal HFS induced higher homoeostasis model of assessment index of insulin resistance v. CON (P=0·030) and HFS/F was associated with higher insulin (P=0·016) and lower glucose (P=0·025). Maternal HFS diet alters offspring insulin sensitivity and de novo hepatic lipogenesis via altered gene and protein expression, which appears to be potentiated by folate supplementation.
Collapse
|
8
|
Protein kinase B: emerging mechanisms of isoform-specific regulation of cellular signaling in cancer. Anticancer Drugs 2017; 28:569-580. [PMID: 28379898 DOI: 10.1097/cad.0000000000000496] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The serine/threonine protein kinase B (PKB), also known as Akt, is one of the multifaceted kinases in the human kinome, existing in three isoforms. PKB plays a vital role in phosphoinositide 3-kinase (PI3K)-mediated oncogenesis in various malignancies and is one of the attractive targets for cancer drug discovery. Recent studies have shown that the functional significance of an individual isoform of PKB is not redundant in cancer. It has been found that PKB isoforms play distinct roles in the regulation of cellular invasion and migration during tumorigenesis. PKB activation plays a central role during epithelial-mesenchymal transition, a cellular program required for the cancer cell invasion and migration. However, the differential behavior of each PKB isoform has been shown in the regulation of epithelial-mesenchymal transition. Recent studies have suggested that PKBα (Akt1) plays a conflicting role in tumorigenesis by acting either as a pro-oncogenic factor by suppressing the apoptotic machinery or by restricting tumor invasion. PKBβ (Akt2) promotes cell migration and invasion and similarly PKBγ (Akt3) has been reported to promote tumor migration. As PKB is known for its pro-oncogenic properties, it needs to be unraveled how three isoforms of PKB compensate during tumor progression. In this review, we attempted to sum up how different isoforms of PKB play a role in cancer progression, metastasis, and drug resistance.
Collapse
|
9
|
Navrátilová J, Karasová M, Kohutková Lánová M, Jiráková L, Budková Z, Pacherník J, Šmarda J, Beneš P. Selective elimination of neuroblastoma cells by synergistic effect of Akt kinase inhibitor and tetrathiomolybdate. J Cell Mol Med 2017; 21:1859-1869. [PMID: 28244639 PMCID: PMC5571524 DOI: 10.1111/jcmm.13106] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 12/25/2016] [Indexed: 12/14/2022] Open
Abstract
Neuroblastoma is the most common extracranial solid tumour of infancy. Pathological activation of glucose consumption, glycolysis and glycolysis‐activating Akt kinase occur frequently in neuroblastoma cells, and these changes correlate with poor prognosis of patients. Therefore, several inhibitors of glucose utilization and the Akt kinase activity are in preclinical trials as potential anti‐cancer drugs. However, metabolic plasticity of cancer cells might undermine efficacy of this approach. In this work, we identified oxidative phosphorylation as compensatory mechanism preserving viability of neuroblastoma cells with inhibited glucose uptake/Akt kinase. It was oxidative phosphorylation that maintained intracellular level of ATP and proliferative capacity of these cells. The oxidative phosphorylation inhibitors (rotenone, tetrathiomolybdate) synergized with inhibitor of the Akt kinase/glucose uptake in down‐regulation of both viability of neuroblastoma cells and clonogenic potential of cells forming neuroblastoma spheroids. Interestingly, tetrathiomolybdate acted as highly specific inhibitor of oxygen consumption and activator of lactate production in neuroblastoma cells, but not in normal fibroblasts and neuronal cells. Moreover, the reducing effect of tetrathiomolybdate on cell viability and the level of ATP in the cells with inhibited Akt kinase/glucose uptake was also selective for neuroblastoma cells. Therefore, efficient elimination of neuroblastoma cells requires inhibition of both glucose uptake/Akt kinase and oxidative phosphorylation activities. The use of tetrathiomolybdate as a mitochondrial inhibitor contributes to selectivity of this combined treatment, preferentially targeting neuroblastoma cells.
Collapse
Affiliation(s)
- Jarmila Navrátilová
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic.,Center for Biological and Cellular Engineering, International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic
| | - Martina Karasová
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Martina Kohutková Lánová
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Ludmila Jiráková
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Zuzana Budková
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Jiří Pacherník
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Jan Šmarda
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Petr Beneš
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic.,Center for Biological and Cellular Engineering, International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic
| |
Collapse
|
10
|
Lin Y, Sun X, Hou X, Qu B, Gao X, Li Q. Effects of glucose on lactose synthesis in mammary epithelial cells from dairy cow. BMC Vet Res 2016; 12:81. [PMID: 27229304 PMCID: PMC4880877 DOI: 10.1186/s12917-016-0704-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 05/17/2016] [Indexed: 11/10/2022] Open
Abstract
Background Lactose, as the primary osmotic component in milk, is the major determinant of milk volume. Glucose is the primary precursor of lactose. However, the effect of glucose on lactose synthesis in dairy cow mammary glands and the mechanism governing this process are poorly understood. Results Here we showed that glucose has the ability to induce lactose synthesis in dairy cow mammary epithelial cells, as well as increase cell viability and proliferation. A concentration of 12 mM glucose was the optimum concentration to induce cell growth and lactose synthesis in cultured dairy cow mammary epithelial cells. In vitro, 12 mM glucose enhanced lactose content, along with the expression of genes involved in glucose transportation and the lactose biosynthesis pathway, including GLUT1, SLC35A2, SLC35B1, HK2, β4GalT-I, and AKT1. In addition, we found that AKT1 knockdown inhibited cell growth and lactose synthesis as well as expression of GLUT1, SLC35A2, SLC35B1, HK2, and β4GalT-I. Conclusions Glucose induces cell growth and lactose synthesis in dairy cow mammary epithelial cells. Protein kinase B alpha acts as a regulator of metabolism in dairy cow mammary gland to mediate the effects of glucose on lactose synthesis. Electronic supplementary material The online version of this article (doi:10.1186/s12917-016-0704-x) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Ye Lin
- Key Laboratory of Dairy Science of Education Ministry, Northeast Agricultural University, Harbin, 150030, China
| | - Xiaoxu Sun
- Key Laboratory of Dairy Science of Education Ministry, Northeast Agricultural University, Harbin, 150030, China
| | - Xiaoming Hou
- Key Laboratory of Dairy Science of Education Ministry, Northeast Agricultural University, Harbin, 150030, China
| | - Bo Qu
- Key Laboratory of Dairy Science of Education Ministry, Northeast Agricultural University, Harbin, 150030, China
| | - Xuejun Gao
- Key Laboratory of Dairy Science of Education Ministry, Northeast Agricultural University, Harbin, 150030, China
| | - Qingzhang Li
- Key Laboratory of Dairy Science of Education Ministry, Northeast Agricultural University, Harbin, 150030, China.
| |
Collapse
|
11
|
Trefely S, Khoo PS, Krycer JR, Chaudhuri R, Fazakerley DJ, Parker BL, Sultani G, Lee J, Stephan JP, Torres E, Jung K, Kuijl C, James DE, Junutula JR, Stöckli J. Kinome Screen Identifies PFKFB3 and Glucose Metabolism as Important Regulators of the Insulin/Insulin-like Growth Factor (IGF)-1 Signaling Pathway. J Biol Chem 2015; 290:25834-46. [PMID: 26342081 DOI: 10.1074/jbc.m115.658815] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Indexed: 01/02/2023] Open
Abstract
The insulin/insulin-like growth factor (IGF)-1 signaling pathway (ISP) plays a fundamental role in long term health in a range of organisms. Protein kinases including Akt and ERK are intimately involved in the ISP. To identify other kinases that may participate in this pathway or intersect with it in a regulatory manner, we performed a whole kinome (779 kinases) siRNA screen for positive or negative regulators of the ISP, using GLUT4 translocation to the cell surface as an output for pathway activity. We identified PFKFB3, a positive regulator of glycolysis that is highly expressed in cancer cells and adipocytes, as a positive ISP regulator. Pharmacological inhibition of PFKFB3 suppressed insulin-stimulated glucose uptake, GLUT4 translocation, and Akt signaling in 3T3-L1 adipocytes. In contrast, overexpression of PFKFB3 in HEK293 cells potentiated insulin-dependent phosphorylation of Akt and Akt substrates. Furthermore, pharmacological modulation of glycolysis in 3T3-L1 adipocytes affected Akt phosphorylation. These data add to an emerging body of evidence that metabolism plays a central role in regulating numerous biological processes including the ISP. Our findings have important implications for diseases such as type 2 diabetes and cancer that are characterized by marked disruption of both metabolism and growth factor signaling.
Collapse
Affiliation(s)
- Sophie Trefely
- From the Garvan Institute of Medical Research, Sydney 2010 NSW, Australia
| | - Poh-Sim Khoo
- From the Garvan Institute of Medical Research, Sydney 2010 NSW, Australia, Genentech Inc., South San Francisco, California 94080
| | - James R Krycer
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and
| | - Rima Chaudhuri
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and
| | - Daniel J Fazakerley
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and
| | - Benjamin L Parker
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and
| | - Ghazal Sultani
- From the Garvan Institute of Medical Research, Sydney 2010 NSW, Australia
| | - James Lee
- Genentech Inc., South San Francisco, California 94080
| | | | - Eric Torres
- Genentech Inc., South San Francisco, California 94080
| | - Kenneth Jung
- Genentech Inc., South San Francisco, California 94080
| | | | - David E James
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and the Sydney Medical School, University of Sydney, Sydney 2006 NSW, Australia
| | | | - Jacqueline Stöckli
- the Charles Perkins Centre, School of Molecular Bioscience, University of Sydney, Sydney 2006 NSW, Australia, and
| |
Collapse
|
12
|
Development of a new model system to dissect isoform specific Akt signalling in adipocytes. Biochem J 2015; 468:425-34. [PMID: 25856301 PMCID: PMC4604748 DOI: 10.1042/bj20150191] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 04/09/2015] [Indexed: 12/17/2022]
Abstract
Our study describes the development and validation of a new model system that allows for acute control of signalling by specific Akt isoforms. This model system revealed new insights into the role of Akt kinases in glucose transport and adipogenesis. Protein kinase B (Akt) kinases are critical signal transducers mediating insulin action. Genetic studies revealed that Akt1 and Akt2 signalling differentially contribute to sustain lipid and glucose homoeostasis; however Akt isoform-specific effectors remain elusive due to the lack of a suitable model system to mechanistically interrogate Akt isoform-specific signalling. To overcome those technical limitations we developed a novel model system that provides acute and specific control of signalling by Akt isoforms. We generated mutants of Akt1 and Akt2 resistant to the allosteric Akt inhibitor MK-2206. We then developed adipocyte cell lines, in which endogenous Akt1 or Akt2 has been replaced by their corresponding drug-resistant Akt mutant. Treatment of those cells with MK-2206 allowed for acute and specific control of either Akt1 or Akt2 function. Our data showed that Akt1W80A and Akt2W80A mutants are resistant to MK-2206, dynamically regulated by insulin and able to signal to Akt downstream effectors. Analyses of insulin action in this cellular system showed that Akt1 and Akt2 are both able to mediate insulin regulation of the transcription factor forkhead box O1 (FoxO1) and the glucose transporter 4 (GLUT4), revealing a redundant role for these Akt kinases in the control of glucose transport into fat cells. In contrast, Akt1 signalling is uniquely required for adipogenesis, by controlling the mitotic clonal expansion (MCE) of pre-adipocytes that precedes white adipose cell differentiation. Our data provide new insights into the role of Akt kinases in glucose transport and adipogenesis and support our model system as a valuable tool for the biochemical characterization of signalling by specific Akt isoforms.
Collapse
|
13
|
Mokbel N, Hoffman NJ, Girgis CM, Small L, Turner N, Daly RJ, Cooney GJ, Holt LJ. Grb10 deletion enhances muscle cell proliferation, differentiation and GLUT4 plasma membrane translocation. J Cell Physiol 2014; 229:1753-64. [PMID: 24664951 DOI: 10.1002/jcp.24628] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Accepted: 03/21/2014] [Indexed: 12/25/2022]
Abstract
Grb10 is an intracellular adaptor protein which binds directly to several growth factor receptors, including those for insulin and insulin-like growth factor receptor-1 (IGF-1), and negatively regulates their actions. Grb10-ablated (Grb10(-/-) ) mice exhibit improved whole body glucose homeostasis and an increase in muscle mass associated specifically with an increase in myofiber number. This suggests that Grb10 may act as a negative regulator of myogenesis. In this study, we investigated in vitro, the molecular mechanisms underlying the increase in muscle mass and the improved glucose metabolism. Primary muscle cells isolated from Grb10(-/-) mice exhibited increased rates of proliferation and differentiation compared to primary cells isolated from wild-type mice. The improved proliferation capacity was associated with an enhanced phosphorylation of Akt and ERK in the basal state and changes in the expression of key cell cycle progression markers involved in regulating transition of cells from the G1 to S phase (e.g., retinoblastoma (Rb) and p21). The absence of Grb10 also promoted a faster transition to a myogenin positive, differentiated state. Glucose uptake was higher in Grb10(-/-) primary myotubes in the basal state and was associated with enhanced insulin signaling and an increase in GLUT4 translocation to the plasma membrane. These data demonstrate an important role for Grb10 as a link between muscle growth and metabolism with therapeutic implications for diseases, such as muscle wasting and type 2 diabetes.
Collapse
Affiliation(s)
- Nancy Mokbel
- Diabetes and Obesity Research Program, The Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Cavalcanti DMLP, Castro LM, Rosa Neto JC, Seelaender M, Neves RX, Oliveira V, Forti FL, Iwai LK, Gozzo FC, Todiras M, Schadock I, Barros CC, Bader M, Ferro ES. Neurolysin knockout mice generation and initial phenotype characterization. J Biol Chem 2014; 289:15426-40. [PMID: 24719317 DOI: 10.1074/jbc.m113.539148] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The oligopeptidase neurolysin (EC 3.4.24.16; Nln) was first identified in rat brain synaptic membranes and shown to ubiquitously participate in the catabolism of bioactive peptides such as neurotensin and bradykinin. Recently, it was suggested that Nln reduction could improve insulin sensitivity. Here, we have shown that Nln KO mice have increased glucose tolerance, insulin sensitivity, and gluconeogenesis. KO mice have increased liver mRNA for several genes related to gluconeogenesis. Isotopic label semiquantitative peptidomic analysis suggests an increase in specific intracellular peptides in gastrocnemius and epididymal adipose tissue, which likely is involved with the increased glucose tolerance and insulin sensitivity in the KO mice. These results suggest the exciting new possibility that Nln is a key enzyme for energy metabolism and could be a novel therapeutic target to improve glucose uptake and insulin sensitivity.
Collapse
Affiliation(s)
| | - Leandro M Castro
- Pharmacology, Support Center for Research in Proteolysis and Cell Signaling, Biomedical Sciences Institute, University of São Paulo, São Paulo, SP 05508-900, Brazil, the Department of Biophysics, Federal University of São Paulo, São Paulo, SP 04039-032, Brazil
| | | | | | | | - Vitor Oliveira
- the Department of Biophysics, Federal University of São Paulo, São Paulo, SP 04039-032, Brazil
| | - Fábio L Forti
- the Department of Biochemistry, Support Center for Research in Proteolysis and Cell Signaling, Institute of Chemistry, University of São Paulo, São Paulo, SP 05508-000, Brazil
| | - Leo K Iwai
- the Special Laboratory of Applied Toxinology, Center of Toxins, Immune Response and Cell Signaling, Butantan Institute, São Paulo, SP 05503-000, Brazil
| | - Fabio C Gozzo
- the Institute of Chemistry, State University of Campinas, Campinas, SP 13083-862, Brazil
| | - Mihail Todiras
- the Max-Delbrück-Center for Molecular Medicine, D-13125, Berlin, Germany, and
| | - Ines Schadock
- the Max-Delbrück-Center for Molecular Medicine, D-13125, Berlin, Germany, and
| | - Carlos C Barros
- the Max-Delbrück-Center for Molecular Medicine, D-13125, Berlin, Germany, and the Department of Nutrition, Federal University of Pelotas, Pelotas, RS 96010-610, Brazil
| | - Michael Bader
- the Max-Delbrück-Center for Molecular Medicine, D-13125, Berlin, Germany, and
| | - Emer S Ferro
- Pharmacology, Support Center for Research in Proteolysis and Cell Signaling, Biomedical Sciences Institute, University of São Paulo, São Paulo, SP 05508-900, Brazil,
| |
Collapse
|
15
|
Lin J, Sampath D, Nannini MA, Lee BB, Degtyarev M, Oeh J, Savage H, Guan Z, Hong R, Kassees R, Lee LB, Risom T, Gross S, Liederer BM, Koeppen H, Skelton NJ, Wallin JJ, Belvin M, Punnoose E, Friedman LS, Lin K. Targeting activated Akt with GDC-0068, a novel selective Akt inhibitor that is efficacious in multiple tumor models. Clin Cancer Res 2013; 19:1760-72. [PMID: 23287563 DOI: 10.1158/1078-0432.ccr-12-3072] [Citation(s) in RCA: 217] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE We describe the preclinical pharmacology and antitumor activity of GDC-0068, a novel highly selective ATP-competitive pan-Akt inhibitor currently in clinical trials for the treatment of human cancers. EXPERIMENTAL DESIGN The effect of GDC-0068 on Akt signaling was characterized using specific biomarkers of the Akt pathway, and response to GDC-0068 was evaluated in human cancer cell lines and xenograft models with various genetic backgrounds, either as a single agent or in combination with chemotherapeutic agents. RESULTS GDC-0068 blocked Akt signaling both in cultured human cancer cell lines and in tumor xenograft models as evidenced by dose-dependent decrease in phosphorylation of downstream targets. Inhibition of Akt activity by GDC-0068 resulted in blockade of cell-cycle progression and reduced viability of cancer cell lines. Markers of Akt activation, including high-basal phospho-Akt levels, PTEN loss, and PIK3CA kinase domain mutations, correlate with sensitivity to GDC-0068. Isogenic PTEN knockout also sensitized MCF10A cells to GDC-0068. In multiple tumor xenograft models, oral administration of GDC-0068 resulted in antitumor activity ranging from tumor growth delay to regression. Consistent with the role of Akt in a survival pathway, GDC-0068 also enhanced antitumor activity of classic chemotherapeutic agents. CONCLUSIONS GDC-0068 is a highly selective, orally bioavailable Akt kinase inhibitor that shows pharmacodynamic inhibition of Akt signaling and robust antitumor activity in human cancer cells in vitro and in vivo. Our preclinical data provide a strong mechanistic rationale to evaluate GDC-0068 in cancers with activated Akt signaling.
Collapse
Affiliation(s)
- Jie Lin
- Genentech, South San Francisco, CA 94080, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
A novel PKB/Akt inhibitor, MK-2206, effectively inhibits insulin-stimulated glucose metabolism and protein synthesis in isolated rat skeletal muscle. Biochem J 2012; 447:137-47. [PMID: 22793019 DOI: 10.1042/bj20120772] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
PKB (protein kinase B), also known as Akt, is a key component of insulin signalling. Defects in PKB activation lead to insulin resistance and metabolic disorders, whereas PKB overactivation has been linked to tumour growth. Small-molecule PKB inhibitors have thus been developed for cancer treatment, but also represent useful tools to probe the roles of PKB in insulin action. In the present study, we examined the acute effects of two allosteric PKB inhibitors, MK-2206 and Akti 1/2 (Akti) on PKB signalling in incubated rat soleus muscles. We also assessed the effects of the compounds on insulin-stimulated glucose uptake, glycogen and protein synthesis. MK-2206 dose-dependently inhibited insulin-stimulated PKB phosphorylation, PKBβ activity and phosphorylation of PKB downstream targets (including glycogen synthase kinase-3α/β, proline-rich Akt substrate of 40 kDa and Akt substrate of 160 kDa). Insulin-stimulated glucose uptake, glycogen synthesis and glycogen synthase activity were also decreased by MK-2206 in a dose-dependent manner. Incubation with high doses of MK-2206 (10 μM) inhibited insulin-induced p70 ribosomal protein S6 kinase and 4E-BP1 (eukaryotic initiation factor 4E-binding protein-1) phosphorylation associated with increased eEF2 (eukaryotic elongation factor 2) phosphorylation. In contrast, Akti only modestly inhibited insulin-induced PKB and mTOR (mammalian target of rapamycin) signalling, with little or no effect on glucose uptake and protein synthesis. MK-2206, rather than Akti, would thus be the tool of choice for studying the role of PKB in insulin action in skeletal muscle. The results point to a key role for PKB in mediating insulin-stimulated glucose uptake, glycogen synthesis and protein synthesis in skeletal muscle.
Collapse
|
17
|
Foster R, Griffin S, Grooby S, Feltell R, Christopherson C, Chang M, Sninsky J, Kwok S, Torrance C. Multiple metabolic alterations exist in mutant PI3K cancers, but only glucose is essential as a nutrient source. PLoS One 2012; 7:e45061. [PMID: 23028762 PMCID: PMC3441563 DOI: 10.1371/journal.pone.0045061] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 08/14/2012] [Indexed: 01/02/2023] Open
Abstract
Targeting tumour metabolism is becoming a major new area of pharmaceutical endeavour. Consequently, a systematic search to define whether there are specific energy source dependencies in tumours, and how these might be dictated by upstream driving genetic mutations, is required. The PI3K-AKT-mTOR signalling pathway has a seminal role in regulating diverse cellular processes including cell proliferation and survival, but has also been associated with metabolic dysregulation. In this study, we sought to define how mutations within PI3KCA may affect the metabolic dependency of a cancer cell, using precisely engineered isogenic cell lines. Studies revealed gene expression signatures in PIK3CA mutant cells indicative of a consistent up-regulation of glycolysis. Interestingly, the genes up- and down-regulated varied between isogenic models suggesting that the primary node of regulation is not the same between models. Additional gene expression changes were also observed, suggesting that metabolic pathways other than glycolysis, such as glutaminolysis, were also affected. Nutrient dependency studies revealed that growth of PIK3CA mutant cells is highly dependent on glucose, whereas glutamine dependency is independent of PIK3CA status. In addition, the glucose dependency exhibited by PIK3CA mutant cells could not be overridden by supplementation with other nutrients. This specific dependence on glucose for growth was further illustrated by studies evaluating the effects of targeted disruption of the glycolytic pathway using siRNA and was also found to be present across a wider panel of cancer cell lines harbouring endogenous PIK3CA mutations. In conclusion, we have found that PIK3CA mutations lead to a shift towards a highly glycolytic phenotype, and that despite suggestions that cancer cells are adept at utilising alternative nutrient sources, PIK3CA mutant cells are not able to compensate for glucose withdrawal. Understanding the metabolic dependencies of PIK3CA mutant cancers will provide critical information for the design of effective therapies and tumour visualisation strategies.
Collapse
Affiliation(s)
- Rebecca Foster
- Horizon Discovery Ltd, Cambridge, Cambridgeshire, United Kingdom.
| | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Tan SX, Ng Y, Meoli CC, Kumar A, Khoo PS, Fazakerley DJ, Junutula JR, Vali S, James DE, Stöckli J. Amplification and demultiplexing in insulin-regulated Akt protein kinase pathway in adipocytes. J Biol Chem 2011; 287:6128-38. [PMID: 22207758 PMCID: PMC3307283 DOI: 10.1074/jbc.m111.318238] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Akt plays a major role in insulin regulation of metabolism in muscle, fat, and liver. Here, we show that in 3T3-L1 adipocytes, Akt operates optimally over a limited dynamic range. This indicates that Akt is a highly sensitive amplification step in the pathway. With robust insulin stimulation, substantial changes in Akt phosphorylation using either pharmacologic or genetic manipulations had relatively little effect on Akt activity. By integrating these data we observed that half-maximal Akt activity was achieved at a threshold level of Akt phosphorylation corresponding to 5–22% of its full dynamic range. This behavior was also associated with lack of concordance or demultiplexing in the behavior of downstream components. Most notably, FoxO1 phosphorylation was more sensitive to insulin and did not exhibit a change in its rate of phosphorylation between 1 and 100 nm insulin compared with other substrates (AS160, TSC2, GSK3). Similar differences were observed between various insulin-regulated pathways such as GLUT4 translocation and protein synthesis. These data indicate that Akt itself is a major amplification switch in the insulin signaling pathway and that features of the pathway enable the insulin signal to be split or demultiplexed into discrete outputs. This has important implications for the role of this pathway in disease.
Collapse
Affiliation(s)
- Shi-Xiong Tan
- Diabetes and Obesity Research Program, The Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, Sydney, New South Wales 2010, Australia
| | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Abstract
The factors that influence preadipocyte determination remain poorly understood. In the present paper, we report that CREBL2 [CREB (cAMP-response-element-binding protein)-like 2], a novel bZIP_1 protein, is up-regulated during MDI-induced preadipocyte differentiation. During both overexpression and under physiological conditions, CREBL2 interacted and was entirely co-localized with CREB. Overexpression of CREBL2 was sufficient to promote adipogenesis via up-regulating the expression of PPARγ (peroxisome-proliferator-activated receptor γ) and C/EBPα (CCAAT/enhancer-binding protein α) and accelerate lipogenesis accompanied with increased GLUT (glucose transporter) 1 and GLUT4. CREBL2 knockdown restrained adipogenic conversion and lipogenesis. Additionally, depletion of CREB could completely block the effects of overexpressed CREBL2, whereas an increase in CREB could not drive adipogenesis in the absence of CREBL2, indicating that the roles for CREBL2 on adipogenesis were CREB-dependent. Furthermore, siCREBL2 [siRNA (short interfering RNA) against CREBL2] could down-regulate CREB transcriptional activity and suppress CREB phosphorylation. CREB knockdown decreased the CREBL2 protein levels and vice versa. Collectively, the results of the present study indicate that CREBL2 plays a critical role in adipogenesis and lipogenesis via interaction with CREB.
Collapse
|
20
|
Inhibiting PI3K reduces mammary tumor growth and induces hyperglycemia in a mouse model of insulin resistance and hyperinsulinemia. Oncogene 2011; 31:3213-22. [PMID: 22037215 PMCID: PMC3275680 DOI: 10.1038/onc.2011.495] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Women with type 2 diabetes (T2DM) are at greater risk of developing and dying from breast cancer than women without T2DM. Insulin resistance and hyperinsulinemia underlie the pathogenesis of T2DM. In the MKR mouse model of insulin resistance, we have previously shown increased activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR pathway in association with accelerated mammary tumor growth. In this study, we demonstrate that inhibiting PI3K with the oral pan-class I PI3K inhibitor, NVP-BKM120 reduced the growth of Met-1 and MCNeuA mammary tumor orthografts in the MKR mouse. NVP-BKM120 treatment decreased phosphorylation of Akt and S6 ribosomal protein (S6rp); no change in Erk1/2 phosphorylation was seen. Hyperglycemia, hypertriglyceridemia and greater hyperinsulinemia developed in the MKR mice treated with NVP-BKM120. We previously reported reduced tumor growth using intraperitoneal rapamycin in the MKR mouse, with the development of hyperglycemia and hypertriglyceridemia. Therefore, we examined whether the oral PI3K/mTOR inhibitor NVP-BEZ235 augmented the tumor suppressing effects of PI3K inhibition. We also investigated the effect of targeted PI3K/mTOR inhibition on PI3K/Akt/mTOR and Erk1/2 signaling, and the potential effects on glycemia. NVP-BEZ235 suppressed the growth of Met-1 and MCNeuA tumor orthografts, and decreased Akt and S6rp phosphorylation, despite increased Erk1/2 phosphorylation in Met-1 orthografts of MKR mice. Less marked hyperglycemia and hyperinsulinemia developed with NVP-BEZ235 than NVP-BKM120. Overall, the results of this study demonstrated that inhibiting PI3K/Akt/mTOR signaling with the oral agents NVP-BKM120 and NVP-BEZ235 decreased mammary tumor growth in the hyperinsulinemic MKR mouse. Inhibiting PI3K alone led to more severe metabolic derangement than inhibiting both PI3K and mTOR. Therefore, PI3K may be an important target for the treatment of breast cancer in women with insulin resistance. Monitoring for hyperglycemia and dyslipidemia should be considered when using these agents in humans, given the metabolic changes detected in this study.
Collapse
|
21
|
Hers I, Vincent EE, Tavaré JM. Akt signalling in health and disease. Cell Signal 2011; 23:1515-27. [PMID: 21620960 DOI: 10.1016/j.cellsig.2011.05.004] [Citation(s) in RCA: 1078] [Impact Index Per Article: 82.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 05/09/2011] [Indexed: 11/25/2022]
Abstract
Akt (also known as protein kinase B or PKB) comprises three closely related isoforms Akt1, Akt2 and Akt3 (or PKBα/β/γ respectively). We have a very good understanding of the mechanisms by which Akt isoforms are activated by growth factors and other extracellular stimuli as well as by oncogenic mutations in key upstream regulatory proteins including Ras, PI3-kinase subunits and PTEN. There are also an ever increasing number of Akt substrates being identified that play a role in the regulation of the diverse array of biological effects of activated Akt; this includes the regulation of cell proliferation, survival and metabolism. Dysregulation of Akt leads to diseases of major unmet medical need such as cancer, diabetes, cardiovascular and neurological diseases. As a result there has been substantial investment in the development of small molecular Akt inhibitors that act competitively with ATP or phospholipid binding, or allosterically. In this review we will briefly discuss our current understanding of how Akt isoforms are regulated, the substrate proteins they phosphorylate and how this integrates with the role of Akt in disease. We will furthermore discuss the types of Akt inhibitors that have been developed and are in clinical trials for human cancer, as well as speculate on potential on-target toxicities, such as disturbances of heart and vascular function, metabolism, memory and mood, which should be monitored very carefully during clinical trial.
Collapse
Affiliation(s)
- Ingeborg Hers
- School of Physiology and Pharmacology, University of Bristol, UK
| | | | | |
Collapse
|
22
|
Next-generation Akt inhibitors provide greater specificity: effects on glucose metabolism in adipocytes. Biochem J 2011; 435:539-44. [DOI: 10.1042/bj20110040] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Many human tumours exhibit activation of the PI3K (phosphoinositide 3-kinase)/Akt pathway, and inhibition of this pathway slows tumour growth. This led to the development of specific Akt inhibitors for in vivo use. However, activation of Akt is also necessary for processes including glucose metabolism. Therefore a potential complication of such anticancer drugs is insulin resistance and/or diabetes. In the process of characterizing the metabolic effects of early-phase Akt inhibitors, we discovered an off-target inhibitory effect on mammalian facilitative glucose transporters. In view of the crucial role of glucose transport for all mammalian cells, such an off-target effect would have major implications for further development of this family of compounds. In the present study, we have characterized a next-generation Akt inhibitor, MK-2206. MK-2206 is an orally active allosteric Akt inhibitor under development for treating solid tumours. We report that MK-2206 potently inhibits Thr308Akt and Ser473Akt phosphorylation in 3T3-L1 adipocytes (IC50 0.11 and 0.18 μM respectively) as well as downstream effects of insulin on GLUT4 (glucose transporter 4) translocation (IC50 0.47 μM) and glucose transport (IC50 0.14 μM). Notably, the potency of MK-2206 is approximately 1 log higher than previous inhibitors and its specificity is significantly improved with modest inhibitory effects on glucose transport in GLUT4-expressing adipocytes and GLUT1-rich human erythrocytes, independently of Akt. Nevertheless, MK-2206 clearly has potent effects on Akt2, the principal isoform involved in peripheral insulin action, in which case insulin resistance will probably be a major complication following in vivo administration. We conclude that MK-2206 provides an optimal tool for studying the effects of Akt in vitro.
Collapse
|