51
|
Nafz J, De-Castro Arce J, Fleig V, Patzelt A, Mazurek S, Rösl F. Interference with energy metabolism by 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside induces HPV suppression in cervical carcinoma cells and apoptosis in the absence of LKB1. Biochem J 2007; 403:501-10. [PMID: 17212587 PMCID: PMC1876364 DOI: 10.1042/bj20061053] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Carcinogenesis is a dynamic and stepwise process, which is accompanied by a variety of somatic and epigenetic alterations in response to a changing microenvironment. Hypoxic conditions will select for cells that have adjusted their metabolic profile and can maintain proliferation by successfully competing for scarce nutritional and oxygen resources. In the present study we have investigated the effects of energy depletion in the context of HPV (human papillomavirus)-induced pathogenesis. We show that cervical carcinoma cell lines are susceptible to undergoing either growth arrest or cell death under conditions of metabolic stress induced by AICAR (5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside), a known activator of the AMPK (AMP-activated protein kinase). Our results reveal that AICAR treatment leads to a reduced binding affinity of the transcription factor AP-1 (activator protein-1) and in turn to a selective suppression of HPV transcription. Moreover, the outcome of AICAR on proliferation and survival was dependent on p53 activation and the presence of LKB1, the major upstream kinase of AMPK. Using non-malignant LKB1-expressing somatic cell hybrids, which lose expression after tumorigenic segregation, as well as small interfering RNA LKB1 knockdown approaches, we could further demonstrate that expression of LKB1 protects cells from cytotoxicity induced by agents which modulate the ATP/AMP ratio. Since simulation of low energy status can selectively eradicate LKB1-negative cervical carcinoma cells, AICAR may represent a novel drug in the treatment of cervical cancer.
Collapse
Affiliation(s)
- Julia Nafz
- *Angewandte Tumorvirologie, Abteilung Virale Transformationsmechanismen, Deutsches Krebsforschungszentrum, Heidelberg 69120, Germany
| | - Johanna De-Castro Arce
- *Angewandte Tumorvirologie, Abteilung Virale Transformationsmechanismen, Deutsches Krebsforschungszentrum, Heidelberg 69120, Germany
| | - Verena Fleig
- *Angewandte Tumorvirologie, Abteilung Virale Transformationsmechanismen, Deutsches Krebsforschungszentrum, Heidelberg 69120, Germany
| | - Andrea Patzelt
- *Angewandte Tumorvirologie, Abteilung Virale Transformationsmechanismen, Deutsches Krebsforschungszentrum, Heidelberg 69120, Germany
| | - Sybille Mazurek
- †Institut für Biochemie und Endokrinologie, Fachbereich Veterinärmedizin, Universität Giessen, Giessen 35392, Germany
| | - Frank Rösl
- *Angewandte Tumorvirologie, Abteilung Virale Transformationsmechanismen, Deutsches Krebsforschungszentrum, Heidelberg 69120, Germany
- To whom correspondence should be addressed (email )
| |
Collapse
|
52
|
Ben Mosbah I, Massip-Salcedo M, Fernández-Monteiro I, Xaus C, Bartrons R, Boillot O, Roselló-Catafau J, Peralta C. Addition of adenosine monophosphate-activated protein kinase activators to University of Wisconsin solution: a way of protecting rat steatotic livers. Liver Transpl 2007; 13:410-25. [PMID: 17326058 DOI: 10.1002/lt.21059] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This study investigates how the addition of trimetazidine (TMZ) and aminoimidazole-4-carboxamide ribonucleoside (AICAR) to University of Wisconsin (UW) solution protects steatotic livers. Steatotic and nonsteatotic livers were preserved for 24 hours at 4 degrees C in UW and UW with TMZ and AICAR (separately or in combination) and then perfused ex vivo for 2 hours at 37 degrees C. Adenosine monophosphate-activated protein kinase (AMPK) or nitric oxide (NO) synthesis inhibition in livers preserved in UW with TMZ was also investigated. Hepatic injury and function (transaminases, bile production, and sulfobromophthalein clearance) and factors potentially involved in the susceptibility of steatotic livers to ischemia-reperfusion (I/R), including vascular resistance, mitochondrial damage, adenosine triphosphate depletion, and oxidative stress were evaluated. AMPK, NO synthase (NOS), nitrate, and nitrite levels were also determined. The addition of TMZ and AICAR (separately or in combination) to UW reduced hepatic injury, improved functionality, and protected against the mechanisms responsible for the vulnerability of steatotic livers to I/R. Like AICAR, TMZ increased AMPK, constitutive NOS, and nitrates and nitrites, and conversely, AMPK or NO synthesis inhibition abolished the benefits of TMZ. In conclusion, TMZ, by means of AMPK, increased NO, thus protecting steatotic livers against their vulnerability to I/R injury. TMZ and AICAR may constitute new additives to UW solution in steatotic liver preservation, whereas a combination of both seems unnecessary.
Collapse
Affiliation(s)
- Ismail Ben Mosbah
- Experimental Hepatic Ischemia-Reperfusion Unit, Instituto de Investigaciones Biomédicas de Barcelona, Instituto de Investigaciones Biomédicas de Barcelona-Consejo Superior de Investigaciones Cientificas, Spain
| | | | | | | | | | | | | | | |
Collapse
|
53
|
Jacobs RL, Lingrell S, Dyck JRB, Vance DE. Inhibition of hepatic phosphatidylcholine synthesis by 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside is independent of AMP-activated protein kinase activation. J Biol Chem 2006; 282:4516-4523. [PMID: 17179149 DOI: 10.1074/jbc.m605702200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
5-Aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAr), a commonly used indirect activator of AMP-activated protein kinase (AMPK), inhibits phosphatidylcholine (PC) biosynthesis in freshly isolated hepatocytes. In all nucleated mammalian cells, PC is synthesized from choline via the Kennedy (CDP-choline) pathway. The purpose of our study was to provide direct evidence that AMPK regulates phospholipid biosynthesis and to elucidate the mechanism(s) by which AMPK inhibits hepatic PC synthesis. Incubations of hepatocytes with AICAr resulted in a dose-dependent activation of AMPK and inhibition of PC biosynthesis. Surprisingly, adenoviral delivery of constitutively active AMPK did not alter PC biosynthesis. In addition, expression of dominant negative mutants of AMPK was unable to block the AICAr-dependent inhibition of PC biosynthesis, indicating that AICAr was acting independently of AMPK activation. Determination of aqueous intermediates of the CDP-choline pathway indicated that choline kinase, the first enzyme in the pathway, was inhibited by AICAr administration. Flux through the CDP-choline pathway was directly correlated to the level of intracellular ATP concentrations. Therefore, it is possible that inhibition of PC biosynthesis is another process by which the cell can reduce ATP consumption in times of energetic stress. However, unlike cholesterol and triacylglycerol biosynthesis, PC production is not regulated by AMPK.
Collapse
Affiliation(s)
- René L Jacobs
- Canadian Institutes of Health Research Group on the Molecular and Cell Biology of Lipids and Department of Biochemistry and the University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Susanne Lingrell
- Canadian Institutes of Health Research Group on the Molecular and Cell Biology of Lipids and Department of Biochemistry and the University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Jason R B Dyck
- Cardiovascular Research Group, Departments of Pediatrics and Pharmacology, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
| | - Dennis E Vance
- Canadian Institutes of Health Research Group on the Molecular and Cell Biology of Lipids and Department of Biochemistry and the University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
| |
Collapse
|
54
|
Beckers A, Organe S, Timmermans L, Vanderhoydonc F, Deboel L, Derua R, Waelkens E, Brusselmans K, Verhoeven G, Swinnen JV. Methotrexate enhances the antianabolic and antiproliferative effects of 5-aminoimidazole-4-carboxamide riboside. Mol Cancer Ther 2006; 5:2211-7. [PMID: 16985054 DOI: 10.1158/1535-7163.mct-06-0001] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Because of its ability to mimic a low energy status of the cell, the cell-permeable nucleoside 5-aminoimidazole-4-carboxamide (AICA) riboside was proposed as an antineoplastic agent switching off major energy-consuming processes associated with the malignant phenotype (lipid production, DNA synthesis, cell proliferation, cell migration, etc.). Key to the antineoplastic action of AICA riboside is its conversion to ZMP, an AMP mimetic that at high concentrations activates the AMP-activated protein kinase (AMPK). Here, in an attempt to increase the efficacy of AICA riboside, we pretreated cancer cells with methotrexate, an antimetabolite blocking the metabolism of ZMP. Methotrexate enhanced the AICA riboside-induced accumulation of ZMP and led to a decrease in the levels of ATP, which functions as an intrasteric inhibitor of AMPK. Consequently, methotrexate markedly sensitized AMPK for activation by AICA riboside and potentiated the inhibitory effects of AICA riboside on tumor-associated processes. As cotreatment elicited antiproliferative effects already at concentrations of compounds that were only marginally effective when used alone, our findings on the cooperation between methotrexate and AICA riboside provide new opportunities both for the application of classic antimetabolic chemotherapeutics, such as methotrexate, and for the exploitation of the energy-sensing machinery as a target for cancer intervention.
Collapse
Affiliation(s)
- Annelies Beckers
- Laboratory for Experimental Medicine and Endocrinology, Katholieke Universiteit Leuven, Gasthuisberg, O&N, Herestraat 49 bus 902, B-3000, Leuven, Belgium
| | | | | | | | | | | | | | | | | | | |
Collapse
|
55
|
Rencurel F, Foretz M, Kaufmann MR, Stroka D, Looser R, Leclerc I, da Silva Xavier G, Rutter GA, Viollet B, Meyer UA. Stimulation of AMP-activated protein kinase is essential for the induction of drug metabolizing enzymes by phenobarbital in human and mouse liver. Mol Pharmacol 2006; 70:1925-34. [PMID: 16988011 DOI: 10.1124/mol.106.029421] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Our previous studies have suggested a role for AMP-activated protein kinase (AMPK) in the induction of CYP2B6 by phenobarbital (PB) in hepatoma-derived cells (Rencurel et al., 2005). In this study, we showed in primary human hepatocytes that: 1) 5'-phosphoribosyl-5-aminoimidazol-4-carboxamide 1-beta-d-ribofuranoside and the biguanide metformin, known activators of AMPK, dose-dependently increase the expression of CYP2B6 and CYP3A4 to an extent similar to that of PB. 2) PB, but not the human nuclear receptor constitutive active/androstane receptor (CAR) ligand 6-(4-chlorophenyl)imidazol[2,1-6][1,3]thiazole-5-carbaldehyde, dose-dependently increase AMPK activity. 3) Pharmacological inhibition of AMPK activity with compound C or dominant-negative forms of AMPK blunt the inductive response to phenobarbital. Furthermore, in transgenic mice with a liver-specific deletion of both the alpha1 and alpha2 AMPK catalytic subunits, basal levels of Cyp2b10 and Cyp3a11 mRNA were increased but not in primary culture of mouse hepatocytes. However, phenobarbital or 1,4 bis[2-(3,5-dichloropyridyloxy)]benzene, a mouse CAR ligand, failed to induce the expression of these genes in the liver or cultured hepatocytes from mice lacking hepatic expression of the alpha1 and alpha2 subunits of AMPK. The distribution of CAR between the nucleus and cytosol was not altered in hepatocytes from mice lacking both AMPK catalytic subunits. These data highlight the essential role of AMPK in the CAR-mediated signal transduction pathway.
Collapse
Affiliation(s)
- Franck Rencurel
- Division of Pharmacology-Neurobiology of the Biozentrum, University of Basel, Basel, Switzerland.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
56
|
Chung KS, Sun NK, Lee SH, Lee HJ, Choi SJ, Kim SK, Song JH, Jang YJ, Song KB, Yoo HS, Simon J, Won M. Cerulenin-mediated apoptosis is involved in adenine metabolic pathway. Biochem Biophys Res Commun 2006; 349:1025-31. [PMID: 16962997 DOI: 10.1016/j.bbrc.2006.08.130] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Accepted: 08/22/2006] [Indexed: 11/27/2022]
Abstract
Cerulenin, a fatty acid synthase (FAS) inhibitor, induces apoptosis of variety of tumor cells. To elucidate mode of action by cerulenin, we employed the proteomics approach using Schizosaccharomyces pombe. The differential protein expression profile of S. pombe revealed that cerulenin modulated the expressions of proteins involved in stresses and metabolism, including both ade10 and adk1 proteins. The nutrient supplementation assay demonstrated that cerulenin affected enzymatic steps transferring a phosphoribosyl group. This result suggests that cerulenin accumulates AMP and p-ribosyl-s-amino-imidazole carboxamide (AICAR) and reduces other necessary nucleotides, which induces feedback inhibition of enzymes and the transcriptional regulation of related genes in de novo and salvage adenine metabolic pathway. Furthermore, the deregulation of adenine nucleotide synthesis may interfere ribonucleotide reductase and cause defects in cell cycle progression and chromosome segregation. In conclusion, cerulenin induces apoptosis through deregulation of adenine nucleotide biosynthesis resulting in nuclear division defects in S. pombe.
Collapse
Affiliation(s)
- Kyung-Sook Chung
- Biopharmaceutical Division, KRIBB, 52 Oun-dong, Yusong-gu, Daejeon 305-806, Republic of Korea
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
57
|
Gaskin FS, Kamada K, Yusof M, Korthuis RJ. 5'-AMP-activated protein kinase activation prevents postischemic leukocyte-endothelial cell adhesive interactions. Am J Physiol Heart Circ Physiol 2006; 292:H326-32. [PMID: 16935999 DOI: 10.1152/ajpheart.00744.2006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Preconditioning (PC) with nitric oxide (NO) donors or agents that increase endothelial NO synthase (eNOS) activity 24 h before ischemia-reperfusion (I/R) prevents postischemic leukocyte rolling (LR) and stationary leukocyte adhesion (LA). Since 5'-AMP-activated protein kinase (AMPK) phosphorylates eNOS at Ser1177, resulting in activation, we postulated that AMPK activation may trigger the development of a preconditioned anti-inflammatory phenotype similar to that induced by NO donors. Wild-type (WT) C57BL/6J and eNOS(-/-) mice were treated with the AMPK agonist 5-aminoimidazole-4-carboxamide 1-beta-d-furanoside (AICAR) 30 min (early AICAR PC) or 24 h (late AICAR PC) before I/R; LR and LA were quantified in single postcapillary venules in the jejunum using intravital microscopy. I/R induced comparable marked increases in LR and LA in WT and eNOS(-/-) mice relative to sham-operated (no ischemia) animals. Late AICAR PC prevented postischemic LR and LA, whereas early AICAR PC prevented LA in WT mice. Late AICAR PC was ineffective in preventing I/R-induced LR but not LA in the eNOS(-/-) mice, and the same pattern was seen in WT animals treated with the NOS inhibitor N(omega)-nitro-l-arginine. Early AICAR PC remained effective in preventing LA in eNOS(-/-) mice. Our results indicate that both early and late PC with an AMPK agonist produces an anti-inflammatory phenotype in postcapillary venules. Since the protection afforded by late AICAR PC on postischemic LR was prevented by NOS inhibition in WT mice and absent in eNOS-deficient mice, it appears that eNOS triggers this protective effect. In stark contrast, antecedent AMPK activation prevented I/R-induced LA by an eNOS-independent mechanism.
Collapse
Affiliation(s)
- F Spencer Gaskin
- Dept. of Medical Pharmacology and Physiology, Univ. of Missouri-Columbia, 1 Hospital Dr., Columbia, MO 65212, USA.
| | | | | | | |
Collapse
|
58
|
Reiter AK, Bolster DR, Crozier SJ, Kimball SR, Jefferson LS. Repression of protein synthesis and mTOR signaling in rat liver mediated by the AMPK activator aminoimidazole carboxamide ribonucleoside. Am J Physiol Endocrinol Metab 2005; 288:E980-8. [PMID: 15613684 DOI: 10.1152/ajpendo.00333.2004] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The studies described herein were designed to investigate the effects of 5-aminoimidazole-4-carboxamide-1-beta-D-ribonucleoside (AICAR), an activator of the AMP-activated protein kinase (AMPK), on the translational control of protein synthesis and signaling through the mammalian target of rapamycin (mTOR) in rat liver. Effects of AICAR observed in vivo were compared with those obtained in an in situ perfused liver preparation to investigate activation of AMPK in the absence of accompanying changes in hormones and nutrients. AMPK became hyperphosphorylated, as assessed by a gel-shift analysis, in response to AICAR both in vivo and in situ; however, increased relative phosphorylation at the Thr172 site on the kinase was observed only in perfused liver. Phosphorylation of AMPK either in vivo or in situ was associated with a repression of protein synthesis as well as decreased phosphorylation of a number of targets of mTOR signaling including ribosomal protein S6 kinase 1, eukaryotic initiation factor (eIF)4G, and eIF4E-binding protein (4E-BP)1. The phosphorylation changes in eIF4G and 4E-BP1 were accompanied by a reduction in the amount of eIF4E present in the active eIF4E.eIF4G complex and an increase in the amount present in the inactive eIF4E.4E-BP1 complex. Reduced insulin signaling as well as differences in nutrient availability may have contributed to the effects observed in vivo as AICAR caused a fall in the serum insulin concentration. Overall, however, the results from both experimental models support a scenario in which AICAR directly represses protein synthesis and mTOR signaling in the liver through an AMPK-dependent mechanism.
Collapse
Affiliation(s)
- Ali K Reiter
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, P.O. Box 850, Hershey, PA 17033, USA
| | | | | | | | | |
Collapse
|
59
|
Camacho RC, Pencek RR, Lacy DB, James FD, Donahue EP, Wasserman DH. Portal venous 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside infusion overcomes hyperinsulinemic suppression of endogenous glucose output. Diabetes 2005; 54:373-82. [PMID: 15677495 DOI: 10.2337/diabetes.54.2.373] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AMP-activated protein kinase (AMPK) plays a key role in regulating metabolism, serving as a metabolic master switch. The aim of this study was to assess whether increased concentrations of the AMP analog, 5-aminoimidazole-4-carboxamide-1-beta-D-ribosyl-5-monophosphate, in the liver would create a metabolic response consistent with an increase in whole-body metabolic need. Dogs had sampling (artery, portal vein, hepatic vein) and infusion (vena cava, portal vein) catheters and flow probes (hepatic artery, portal vein) implanted >16 days before a study. Protocols consisted of equilibration (-130 to -30 min), basal (-30 to 0 min), and hyperinsulinemic-euglycemic or -hypoglycemic clamp periods (0-150 min). At t = 0 min, somatostatin was infused and glucagon was replaced in the portal vein at basal rates. An intraportal hyperinsulinemic (2 mU . kg(-1) . min(-1)) infusion was also initiated at this time. Glucose was clamped at hypoglycemic or euglycemic levels in the presence (H-AIC, n = 6; E-AIC, n = 6) or absence (H-SAL, n = 6; E-SAL, n = 6) of a portal venous 5-aminoimidazole-4-carboxamide-ribofuranoside (AICAR) infusion (1 mg . kg(-1) . min(-1)) initiated at t = 60 min. In the presence of intraportal saline, glucose was infused into the vena cava to match glucose levels seen with intraportal AICAR. Glucagon remained fixed at basal levels, whereas insulin rose similarly in all groups. Glucose fell to 50 +/- 2 mg/dl by t = 60 min in hypoglycemic groups and remained at 105 +/- 3 mg/dl in euglycemic groups. Endogenous glucose production (R(a)) was similarly suppressed among groups in the presence of euglycemia or hypoglycemia before t = 60 min and remained suppressed in the H-SAL and E-SAL groups. However, intraportal AICAR infusion stimulated R(a) to increase by 2.5 +/- 1.0 and 3.4 +/- 0.4 mg . kg(-1) . min(-1) in the E-AIC and H-AIC groups, respectively. Arteriovenous measurement of net hepatic glucose output showed similar results. AICAR stimulated hepatic glycogen to decrease by 5 +/- 3 and 19 +/- 5 mg/g tissue (P < 0.05) in the presence of euglycemia and hypoglycemia, respectively. AICAR significantly increased net hepatic lactate output in the presence of hypoglycemia. Thus, intraportal AICAR infusion caused marked stimulation of both hepatic glucose output and net hepatic glycogenolysis, even in the presence of high levels of physiological insulin. This stimulation of glucose output by AICAR was equally marked in the presence of both euglycemia and hypoglycemia. However, hypoglycemia amplified the net hepatic glycogenolytic response to AICAR by approximately fourfold.
Collapse
Affiliation(s)
- Raul C Camacho
- Department of Molecular Physiology and Biophysics, Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA.
| | | | | | | | | | | |
Collapse
|
60
|
Rencurel F, Stenhouse A, Hawley SA, Friedberg T, Hardie DG, Sutherland C, Wolf CR. AMP-activated Protein Kinase Mediates Phenobarbital Induction of CYP2B Gene Expression in Hepatocytes and a Newly Derived Human Hepatoma Cell Line. J Biol Chem 2005; 280:4367-73. [PMID: 15572372 DOI: 10.1074/jbc.m412711200] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phenobarbital (PB) administration is known to trigger pleiotropic responses, including liver hypertrophy, tumor promotion, and induction of genes encoding drug-metabolizing enzymes. The induction of human CYP2B6 and the rat (CYP2B1) and mouse (Cyp2b10) homologues by PB is mediated by the nuclear receptor constitutive androstane receptor (CAR). The study of CYP2B gene regulation and CAR activity by PB has been difficult due to the lack of a cellular model. In this study, we describe a novel differentiated human hepatoma cell line (WGA), derived from HepG2, which expresses CYP2B6 and CAR. WGA cells represent a powerful system to study the regulation of CYP2B6 gene expression by PB. There is evidence that CAR activity is regulated by phosphorylation and that regulation of some CYP genes depends on the nutritional status of cells. The AMP-activated protein kinase (AMPK) functions as an energy sensor and is activated when cells experience energy-depleting stresses. In this report, we show that addition of 5-amino-imidazole carboxamide riboside, an AMPK activator, to WGA and human hepatocytes induces CYP2B6 gene expression. Expression of a constitutively active form of AMPK mimics the PB induction of CYP2B6 and CYP2B1 gene expression. Conversely, the expression of a dominant negative form of AMPK inhibits the induction of these genes by PB. Finally, we demonstrate, for the first time, that AMPK activity increases in cells cultured with PB. Our data strongly support a role for AMPK in the PB induction of CYP2B gene expression and provide new insights into the regulation of gene expression by barbiturate drugs.
Collapse
MESH Headings
- AMP-Activated Protein Kinases
- Adenosine Triphosphate/chemistry
- Adenoviridae
- Aminoimidazole Carboxamide/analogs & derivatives
- Aminoimidazole Carboxamide/pharmacology
- Animals
- Aryl Hydrocarbon Hydroxylases/biosynthesis
- Aryl Hydrocarbon Hydroxylases/chemistry
- Barbiturates/pharmacology
- Blotting, Western
- Cell Line, Tumor
- Cells, Cultured
- Constitutive Androstane Receptor
- Culture Media
- Cytochrome P-450 CYP2B1/biosynthesis
- Cytochrome P-450 CYP2B6
- Gene Expression Regulation
- Gene Expression Regulation, Neoplastic
- Genes, Dominant
- Genes, Reporter
- Hepatocytes/metabolism
- Humans
- Male
- Mice
- Multienzyme Complexes/physiology
- Oxidoreductases, N-Demethylating/biosynthesis
- Oxidoreductases, N-Demethylating/chemistry
- Phenobarbital/metabolism
- Phenobarbital/pharmacology
- Phosphorylation
- Plasmids/metabolism
- Promoter Regions, Genetic
- Protein Serine-Threonine Kinases/physiology
- Protein Structure, Tertiary
- RNA/metabolism
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Cytoplasmic and Nuclear/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Ribonucleosides/pharmacology
- Transcription Factors/metabolism
- Transcription, Genetic
- beta-Galactosidase/metabolism
Collapse
Affiliation(s)
- Franck Rencurel
- Biomedical Research Centre and Cancer Research UK Molecular Pharmacology Unit, Level 5, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
61
|
Menze MA, Clavenna MJ, Hand SC. Depression of cell metabolism and proliferation by membrane-permeable and -impermeable modulators: role for AMP-to-ATP ratio. Am J Physiol Regul Integr Comp Physiol 2004; 288:R501-10. [PMID: 15458972 DOI: 10.1152/ajpregu.00490.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The metabolic and developmental depression commonly observed during natural states of dormancy, such as diapause and quiescence, is typically accompanied by an increase in the intracellular ratio of AMP to ATP. We investigated the impact of artificially increasing the AMP-to-ATP ratio in mouse macrophages. Evidence is presented here that the P2X7 receptor channel can be used as an effective means to load cells with membrane-impermeable compounds. Intracellular loading of adenosine-5'-O-thiomonophosphate (AMPS), a nonhydrolyzable analog of 5'-AMP and potent activator of AMP-activated protein kinase, significantly depresses metabolism and proliferation of macrophages. The intracellular effective AMP-to-ATP ratio obtained (the sum of AMPS plus endogenous 5'-AMP) was 0.073, well above that reported to activate AMP-activated protein kinase in vitro. Optimizing both the conditions under which the P2X7 receptor channel is opened and the duration of opening facilitates high analog uptake and approximately 98% survivorship. An advantage to AMPS is its minimal impact on other components of the nucleotide pool, most notably the unchanged concentration of ADP. An alternative way to shift the effective AMP-to-ATP ratio is by incubation with the membrane-permeable compound 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR), which is phosphorylated intracellularly to form the 5'-AMP analog ZMP. Despite a rapid intracellular accumulation of AICAR, conversion to ZMP was slow and inefficient. Furthermore, AICAR incubation increased cellular ADP, and, although cell proliferation was depressed, the overall cellular energy flow was unchanged. The rapid action of AMPS avoids upregulation of compensatory metabolic pathways and may provide a viable approach for promoting cell stasis.
Collapse
Affiliation(s)
- Michael A Menze
- Division of Cellular, Developmental and Integrative Biology, Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | | | | |
Collapse
|
62
|
Kim EK, Miller I, Aja S, Landree LE, Pinn M, McFadden J, Kuhajda FP, Moran TH, Ronnett GV. C75, a fatty acid synthase inhibitor, reduces food intake via hypothalamic AMP-activated protein kinase. J Biol Chem 2004; 279:19970-6. [PMID: 15028725 DOI: 10.1074/jbc.m402165200] [Citation(s) in RCA: 227] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Energy homeostasis and feeding are regulated by the central nervous system. C75, a fatty acid synthase (FAS) inhibitor, causes weight loss and anorexia, implying a novel central nervous system pathway(s) for sensing energy balance. AMP-activated protein kinase (AMPK), a sensor of peripheral energy balance, is phosphorylated and activated when energy sources are low. Here, we identify a role for hypothalamic AMPK in the regulation of feeding behavior and in mediating the anorexic effects of C75. 5-Aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR), an activator of AMPK, increased food intake, whereas compound C, an inhibitor of AMPK, decreased food intake. C75 rapidly reduced the level of the phosphorylated AMPK alpha subunit (pAMPKalpha) in the hypothalamus, even in fasted mice that had elevated hypothalamic pAMPKalpha levels. Furthermore, AICAR reversed both the C75-induced anorexia and the decrease in hypothalamic pAMPKalpha levels. C75 elevated hypothalamic neuronal ATP levels, which may contribute to the mechanism by which C75 decreased AMPK activity. C75 reduced the levels of pAMPKalpha and phosphorylated cAMP response element-binding protein (pCREB) in the arcuate nucleus neurons of the hypothalamus, suggesting a mechanism for the reduction in NPY expression seen with C75 treatment. These data indicate that modulation of FAS activity in the hypothalamus can alter energy perception via AMPK, which functions as a physiological energy sensor in the hypothalamus.
Collapse
Affiliation(s)
- Eun-Kyoung Kim
- Department of Neuroscience, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
63
|
Shang J, Lehrman MA. Activation of glycogen phosphorylase with 5-aminoimidazole-4-carboxamide riboside (AICAR). Assessment of glycogen as a precursor of mannosyl residues in glycoconjugates. J Biol Chem 2004; 279:12076-80. [PMID: 14729664 DOI: 10.1074/jbc.m400431200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The experimental evaluation of the contribution of glycogen phosphorylase (GP) to biochemical pathways is limited to methods that raise cAMP, activating the cAMP-dependent protein kinase/phosphorylase kinase/GP cascade. Such methods convert the unphosphorylated form, "GPb," which catalyzes glycogenolysis only in the presence of appropriate allosteric activators such as AMP, to the phosphorylated, constitutively activated form, "GPa." However, activation of GP in this way is indirect, requires a functional cAMP kinase cascade, and is complicated by other actions of cAMP. Here, we demonstrate a strategy for the experimental manipulation of GP in intact dermal fibroblasts, involving activation by the membrane-permeable adenosine analog 5-aminoimidazole-4-carboxamide riboside (AICAR) and inhibition by caffeine and Pfizer compound CP-91149, which bind to GP at distinct sites. Potential complications because of activation of AMP-activated protein kinase by AICAR were assessed with metformin, which activates this kinase but does not activate GP. Using this strategy, we show that glycogen can be a significant and regulatable precursor of mannosyl units in lipid-linked oligosaccharides and glycoproteins.
Collapse
Affiliation(s)
- Jie Shang
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9041, USA
| | | |
Collapse
|
64
|
Campàs C, Lopez JM, Santidrián AF, Barragán M, Bellosillo B, Colomer D, Gil J. Acadesine activates AMPK and induces apoptosis in B-cell chronic lymphocytic leukemia cells but not in T lymphocytes. Blood 2003; 101:3674-80. [PMID: 12522004 DOI: 10.1182/blood-2002-07-2339] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acadesine, 5-aminoimidazole-4-carboxamide (AICA) riboside, induced apoptosis in B-cell chronic lymphocytic leukemia (B-CLL) cells in all samples tested (n = 70). The half-maximal effective concentration (EC(50)) for B-CLL cells was 380 +/- 60 microM (n = 5). The caspase inhibitor Z-VAD.fmk completely blocked acadesine-induced apoptosis, which involved the activation of caspase-3, -8, and -9 and cytochrome c release. Incubation of B-CLL cells with acadesine induced the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK), indicating that it is activated by acadesine. Nitrobenzylthioinosine (NBTI), a nucleoside transport inhibitor, 5-iodotubercidin, an inhibitor of adenosine kinase, and adenosine completely inhibited acadesine-induced apoptosis and AMPK phosphorylation, demonstrating that incorporation of acadesine into the cell and its subsequent phosphorylation to AICA ribotide (ZMP) are necessary to induce apoptosis. Inhibitors of protein kinase A and mitogen-activated protein kinases did not protect from acadesine-induced apoptosis in B-CLL cells. Moreover, acadesine had no effect on p53 levels or phosphorylation, suggesting a p53-independent mechanism in apoptosis triggering. Normal B lymphocytes were as sensitive as B-CLL cells to acadesine-induced apoptosis. However, T cells from patients with B-CLL were only slightly affected by acadesine at doses up to 4 mM. AMPK phosphorylation did not occur in T cells treated with acadesine. Intracellular levels of ZMP were higher in B-CLL cells than in T cells when both were treated with 0.5 mM acadesine, suggesting that ZMP accumulation is necessary to activate AMPK and induce apoptosis. These results suggest a new pathway involving AMPK in the control of apoptosis in B-CLL cells and raise the possibility of using acadesine in B-CLL treatment.
Collapse
MESH Headings
- AMP-Activated Protein Kinases
- Adenosine/pharmacology
- Amino Acid Chloromethyl Ketones/pharmacology
- Aminoimidazole Carboxamide/analogs & derivatives
- Aminoimidazole Carboxamide/antagonists & inhibitors
- Aminoimidazole Carboxamide/metabolism
- Aminoimidazole Carboxamide/pharmacology
- Antimetabolites, Antineoplastic/pharmacology
- Apoptosis/drug effects
- B-Lymphocytes/drug effects
- B-Lymphocytes/enzymology
- B-Lymphocytes/pathology
- Caspases/metabolism
- Cyclic AMP-Dependent Protein Kinases/antagonists & inhibitors
- Cysteine Proteinase Inhibitors/pharmacology
- Enzyme Activation/drug effects
- Enzyme Inhibitors/pharmacology
- Humans
- Leukemia, Lymphocytic, Chronic, B-Cell/enzymology
- Leukemia, Lymphocytic, Chronic, B-Cell/pathology
- MAP Kinase Signaling System/drug effects
- Mitochondria/drug effects
- Mitogen-Activated Protein Kinases/antagonists & inhibitors
- Multienzyme Complexes/metabolism
- Neoplasm Proteins/metabolism
- Neoplastic Stem Cells/drug effects
- Neoplastic Stem Cells/enzymology
- Neoplastic Stem Cells/pathology
- Phosphorylation/drug effects
- Protein Processing, Post-Translational/drug effects
- Protein Serine-Threonine Kinases/metabolism
- Ribonucleosides/antagonists & inhibitors
- Ribonucleosides/pharmacology
- Ribonucleotides/metabolism
- T-Lymphocytes/drug effects
- T-Lymphocytes/enzymology
- Tubercidin/analogs & derivatives
- Tubercidin/pharmacology
- Tumor Cells, Cultured/drug effects
- Tumor Cells, Cultured/enzymology
- Tumor Cells, Cultured/pathology
Collapse
Affiliation(s)
- Clara Campàs
- Unitat de Bioquimica, Departament de Ciències Fisiològiques II, Universitat de Barcelona, Campus de Bellvitge, E-08907 L'Hospitalet de Llobregat, Spain
| | | | | | | | | | | | | |
Collapse
|
65
|
Meisse D, Van de Casteele M, Beauloye C, Hainault I, Kefas BA, Rider MH, Foufelle F, Hue L. Sustained activation of AMP-activated protein kinase induces c-Jun N-terminal kinase activation and apoptosis in liver cells. FEBS Lett 2002; 526:38-42. [PMID: 12208500 DOI: 10.1016/s0014-5793(02)03110-1] [Citation(s) in RCA: 168] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The aim of this work was to study the effect of a sustained activation of AMP-activated protein kinase (AMPK) on liver cell survival. AMPK activation was achieved by incubating FTO2B cells with AICA-riboside, which is transformed into ZMP, an AMP analogue, or by adenoviral transfection of hepatocytes with a constitutively active form of AMPK. Prolonged AMPK activation triggered apoptosis and activated c-Jun N-terminal kinase (JNK) and caspase-3. Experiments with iodotubercidin, dicoumarol and z-VAD-fmk, which inhibited AMPK, JNK and caspase activation, respectively, supported the notion that prolonged AMPK activation in liver cells induces apoptosis through an activation pathway that involves JNK and caspase-3.
Collapse
Affiliation(s)
- Delphine Meisse
- Hormone and Metabolic Research Unit, University of Louvain Medical School and Christian de Duve International Institute of Molecular and Cellular Pathology, Brussels, Belgium.
| | | | | | | | | | | | | | | |
Collapse
|
66
|
Holmes WB, Appling DR. Cloning and characterization of methenyltetrahydrofolate synthetase from Saccharomyces cerevisiae. J Biol Chem 2002; 277:20205-13. [PMID: 11923304 DOI: 10.1074/jbc.m201242200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The folate derivative 5-formyltetrahydrofolate (folinic acid; 5-CHO-THF) was discovered over 40 years ago, but its role in metabolism remains poorly understood. Only one enzyme is known that utilizes 5-CHO-THF as a substrate: 5,10-methenyltetrahydrofolate synthetase (MTHFS). A BLAST search of the yeast genome using the human MTHFS sequence revealed a 211-amino acid open reading frame (YER183c) with significant homology. The yeast enzyme was expressed in Escherichia coli, and the purified recombinant enzyme exhibited kinetics similar to previously purified MTHFS. No new phenotype was observed in strains disrupted at MTHFS or in strains additionally disrupted at the genes encoding one or both serine hydroxymethyltransferases (SHMT) or at the genes encoding one or both methylenetetrahydrofolate reductases. However, when the MTHFS gene was disrupted in a strain lacking the de novo folate biosynthesis pathway, folinic acid (5-CHO-THF) could no longer support the folate requirement. We have thus named the yeast gene encoding methenyltetrahydrofolate synthetase FAU1 (folinic acid utilization). Disruption of the FAU1 gene in a strain lacking both 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) transformylase isozymes (ADE16 and ADE17) resulted in a growth deficiency that was alleviated by methionine. Genetic analysis suggested that intracellular accumulation of the purine intermediate AICAR interferes with a step in methionine biosynthesis. Intracellular levels of 5-CHO-THF were determined in yeast disrupted at FAU1 and other genes encoding folate-dependent enzymes. In fau1 disruptants, 5-CHO-THF was elevated 4-fold over wild-type yeast. In yeast lacking MTHFS along with both AICAR transformylases, 5-CHO-THF was elevated 12-fold over wild type. 5-CHO-THF was undetectable in strains lacking SHMT activity, confirming SHMT as the in vivo source of 5-CHO-THF. Taken together, these results indicate that S. cerevisiae harbors a single, nonessential, MTHFS activity. Growth phenotypes of multiply disrupted strains are consistent with a regulatory role for 5-CHO-THF in one-carbon metabolism and additionally suggest a metabolic interaction between the purine and methionine pathways.
Collapse
Affiliation(s)
- William B Holmes
- Department of Chemistry and Biochemistry, the Institute for Cellular and Molecular Biology, and the Biochemical Institute, University of Texas, Austin 78712, USA
| | | |
Collapse
|
67
|
Downs SM, Hudson ER, Hardie DG. A potential role for AMP-activated protein kinase in meiotic induction in mouse oocytes. Dev Biol 2002; 245:200-12. [PMID: 11969266 DOI: 10.1006/dbio.2002.0613] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cyclic adenosine monophosphate (cAMP) has been implicated as an important regulator of meiotic maturation in mammalian oocytes. A decrease in cAMP, brought about by the action of cAMP phosphodiesterase (PDE), is thought to initiate germinal vesicle breakdown (GVB) by the inactivation of cAMP-dependent protein kinase. However, the product of PDE activity, 5'-AMP, is a potent activator of an important regulatory enzyme, AMP-activated protein kinase (AMPK). The aim of this study was to evaluate a possible role for AMPK in meiotic induction, using oocytes obtained from eCG-primed, immature mice. Alpha-1 and -2 isoforms of the catalytic subunit of AMPK were detected in both oocytes and cumulus cells. When 5-aminoimidazole-4-carboxamide 1-beta-d-ribofuranoside (AICA riboside), an activator of AMPK, was tested on denuded oocytes (DO) and cumulus cell-enclosed oocytes (CEO) maintained in meiotic arrest by dbcAMP or hypoxanthine, GVB was dose-dependently induced. Meiotic induction by AICA riboside in dbcAMP-supplemented medium was initiated within 3 h in DO and 4 h in CEO and was accompanied by increased AMPK activity in the oocyte. AICA riboside also triggered GVB when meiotic arrest was maintained with hypoxanthine, 8-AHA-cAMP, guanosine, or milrinone, but was ineffective in olomoucine- or roscovitine-arrested oocytes, indicating that it acts upstream of maturation-promoting factor. Adenosine monophosphate dose-dependently stimulated GVB in DO when meiotic arrest was maintained with dbcAMP or hypoxanthine. This effect was not mimicked by other monophosphate or adenosine nucleotides and was not affected by inhibitors of ectophosphatases. Combined treatment with adenosine and deoxycoformycin, an adenosine deaminase inhibitor, stimulated GVB in dbcAMP-arrested CEO, suggesting AMPK activation due to AMP accumulation. It is concluded that phosphodiesterase-generated AMP may serve as a transducer of the meiotic induction process through activation of AMPK.
Collapse
Affiliation(s)
- Stephen M Downs
- Biology Department, Marquette University, 530 N. 15 Street, Milwaukee, WI 53233, USA.
| | | | | |
Collapse
|
68
|
Aschenbach WG, Hirshman MF, Fujii N, Sakamoto K, Howlett KF, Goodyear LJ. Effect of AICAR treatment on glycogen metabolism in skeletal muscle. Diabetes 2002; 51:567-73. [PMID: 11872652 DOI: 10.2337/diabetes.51.3.567] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AMP-activated protein kinase (AMPK) is proposed to stimulate fat and carbohydrate catabolism to maintain cellular energy status. Recent studies demonstrate that pharmacologic activation of AMPK and mutations in the enzyme are associated with elevated muscle glycogen content in vivo. Our purpose was to determine the mechanism for increased muscle glycogen associated with AMPK activity in vivo. AMPK activity and glycogen metabolism were studied in red and white gastrocnemius muscles from rats treated with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) in vivo, and also in muscles incubated with AICAR in vitro. In vivo AICAR treatment reduced blood glucose and increased blood lactate compared with basal values. AICAR increased muscle alpha2 AMPK activity, glycogen, and glucose-6-phosphate concentrations. Glycogen synthase activity was increased in the red gastrocnemius but was decreased in the white gastrocnemius. Glycogen phosphorylase activity increased in both muscles, with an inhibition initially observed in the red gastrocnemius. In vitro incubation with AICAR activated alpha2 AMPK but had no effect on either glycogen synthase or glycogen phosphorylase. These results suggest that AICAR treatment does not promote glycogen accumulation in skeletal muscle in vivo by altering glycogen synthase and glycogen phosphorylase. Rather, the increased glycogen is due to the well-known effects of AICAR to increase glucose uptake.
Collapse
Affiliation(s)
- William G Aschenbach
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts 02215, USA
| | | | | | | | | | | |
Collapse
|
69
|
Imamura K, Ogura T, Kishimoto A, Kaminishi M, Esumi H. Cell cycle regulation via p53 phosphorylation by a 5'-AMP activated protein kinase activator, 5-aminoimidazole- 4-carboxamide-1-beta-D-ribofuranoside, in a human hepatocellular carcinoma cell line. Biochem Biophys Res Commun 2001; 287:562-7. [PMID: 11554766 DOI: 10.1006/bbrc.2001.5627] [Citation(s) in RCA: 282] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
5-Aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) is an activator of AMP activated protein kinase (AMPK) and a regulator of de novo purine synthesis. There are several earlier reports indicating that AICAR treatment suppresses cell growth via regulation of AMPK or de novo purine synthesis. We found cell growth to be suppressed by AICAR treatment in HepG2 because of p53 accumulation, which was associated with p53-Ser15 phosphorylation. Moreover, a motif very similar to the consensus motif of AMPK phosphorylation was found around p53-Ser15, and Ser15 phosphorylation was detected in AICAR treated HepG2 as was in vitro phosphorylation by AMPK. Our results suggest that AICAR may regulate cell growth via p53 phosphorylation, and also indicate the possibility of p53 phosphorylation.
Collapse
Affiliation(s)
- K Imamura
- Investigative Treatment Division, National Cancer Center Research Institute East, 6-5-1, Kashiwanoha, Kashiwa, Chiba, 277-8577, Japan
| | | | | | | | | |
Collapse
|
70
|
Winder WW. Energy-sensing and signaling by AMP-activated protein kinase in skeletal muscle. J Appl Physiol (1985) 2001; 91:1017-28. [PMID: 11509493 DOI: 10.1152/jappl.2001.91.3.1017] [Citation(s) in RCA: 258] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
AMP-activated protein kinase (AMPK) is emerging as an important energy-sensing/signaling system in skeletal muscle. This kinase is activated allosterically by 5'-AMP and inhibited allosterically by creatine phosphate. Phosphorylation of AMPK by an upstream kinase, AMPK kinase (also activated allosterically by 5'-AMP), results in activation. It is activated in both rat and human muscle in response to muscle contraction, the extent of activation depending on work rate and muscle glycogen concentration. AMPK can also be activated chemically in resting muscle with 5-aminoimidazole-4-carboxamide-riboside, which enters the muscle and is phosphorylated to form ZMP, a nucleotide that mimics the effect of 5'-AMP. Once activated, AMPK is hypothesized to phosphorylate proteins involved in triggering fatty acid oxidation and glucose uptake. Evidence is also accumulating for a role of AMPK in inducing some of the adaptations to endurance training, including the increase in muscle GLUT-4, hexokinase, uncoupling protein 3, and some of the mitochondrial oxidative enzymes. It thus appears that AMPK has the capability of monitoring intramuscular energy charge and then acutely stimulating fat oxidation and glucose uptake to counteract the increased rates of ATP utilization during muscle contraction. In addition, this system may have the capability of enhancing capacity for ATP production when the muscle is exposed to endurance training.
Collapse
Affiliation(s)
- W W Winder
- Department of Zoology, Brigham Young University, Provo, Utah 84602, USA.
| |
Collapse
|
71
|
Camoni L, Visconti S, Marra M, Aducci P. Adenosine 5'-monophosphate inhibits the association of 14-3-3 proteins with the plant plasma membrane H(+)-ATPase. J Biol Chem 2001; 276:31709-12. [PMID: 11423544 DOI: 10.1074/jbc.m104194200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although a well ascertained evidence proves that the activity of the plant plasma membrane H(+)-ATPase is regulated by 14-3-3 proteins, information about physiological factors modulating the phosphorylation-dependent association between 14-3-3 proteins and the proton pump is largely incomplete. In this paper we show that the 5'-AMP-mimetic, 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), inhibits the fusicoccin-promoted proton extrusion in maize roots. We also demonstrate that 5'-AMP inhibits the association of 14-3-3 proteins with the C-terminal domain of the H(+)-ATPase in an overlay assay as well as the 14-3-3-dependent stimulation of the Arabidopsis thaliana H(+)-ATPase AHA1 isoform expressed in yeast membranes. Finally, by means of affinity chromatography with immobilized 5'-AMP and trinitrophenyl-AMP fluorescence analysis, we demonstrate that the 14-3-3 isoform GF14-6 from maize is able to bind 5'-AMP. The possible role of 5'-AMP as a general regulator of 14-3-3 functions in the plant cell is discussed.
Collapse
Affiliation(s)
- L Camoni
- Department of Biology, University of Rome Tor Vergata, via della Ricerca Scientifica, I-00133, Rome, Italy
| | | | | | | |
Collapse
|
72
|
Kim J, Yoon MY, Choi SL, Kang I, Kim SS, Kim YS, Choi YK, Ha J. Effects of stimulation of AMP-activated protein kinase on insulin-like growth factor 1- and epidermal growth factor-dependent extracellular signal-regulated kinase pathway. J Biol Chem 2001; 276:19102-10. [PMID: 11262401 DOI: 10.1074/jbc.m011579200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
AMP-activated protein kinase (AMPK) is tightly regulated by the cellular AMP:ATP ratio and plays a central role in the regulation of energy homeostasis. Previously, AMPK was reported to phosphorylate serine 621 of Raf-1 in vitro. In the present study, we investigated a possible role of AMPK in extracellular signal-regulated kinase (Erk) cascades, using 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR), a cell-permeable activator of AMPK and antisense RNA experiments. Activation of AMPK by AICAR in NIH-3T3 cells resulted in drastic inhibitions of Ras, Raf-1, and Erk activation induced by insulin-like growth factor 1 (IGF-1). Expression of an antisense RNA for the AMPK catalytic subunit decreased the AMPK activity and significantly diminished the AICAR effect on IGF-1-induced Ras activation and the subsequent Erk activation, indicating that its effect is indeed mediated by AMPK. Phosphorylation of Raf-1 serine 621, however, was not involved in AMPK-mediated inhibition of Erk cascades. In contrast to IGF-1, AICAR did not block epidermal growth factor (EGF)-dependent Raf-1 and Erk activation, but our results demonstrated that multiple Raf-1 upstream pathways induced by EGF were differentially affected by AICAR: inhibition of Ras activation and simultaneous induction of Ras-independent Raf activation. The activities of IGF-1 and EGF receptor were not affected by AICAR. Taken together, our results suggest that AMPK differentially regulate Erk cascades by inhibiting Ras activation or stimulating the Ras-independent pathway in response to the varying energy status of the cell.
Collapse
Affiliation(s)
- J Kim
- Department of Chemistry, Hanyang University, Seoul 133-791, Korea
| | | | | | | | | | | | | | | |
Collapse
|
73
|
Zhou M, Lin BZ, Coughlin S, Vallega G, Pilch PF. UCP-3 expression in skeletal muscle: effects of exercise, hypoxia, and AMP-activated protein kinase. Am J Physiol Endocrinol Metab 2000; 279:E622-9. [PMID: 10950831 DOI: 10.1152/ajpendo.2000.279.3.e622] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Uncoupling protein 3 (UCP-3), a member of the mitochondrial transporter superfamily, is expressed primarily in skeletal muscle where it may play a role in altering metabolic function under conditions of fuel depletion caused, for example, by fasting and exercise. Here, we show that treadmill running by rats rapidly (30 min) induces skeletal muscle UCP-3 mRNA expression (sevenfold after 200 min), as do hypoxia and swimming in a comparably rapid and substantial fashion. The expression of the mitochondrial transporters, carnitine palmitoyltransferase 1 and the tricarboxylate carrier, is unaffected under these conditions. Hypoxia and exercise-mediated induction of UCP-3 mRNA result in a corresponding four- to sixfold increase in rat UCP-3 protein. We treated extensor digitorum longus (EDL) muscle with 5'-amino-4-imidazolecarboxamide ribonucleoside (AICAR), a compound that activates AMP-activated protein kinase (AMPK), an enzyme known to be stimulated during exercise and hypoxia. Incubation of rat EDL muscle in vitro for 30 min with 2 mM AICAR causes a threefold increase in UCP-3 mRNA and a 1.5-fold increase of UCP-3 protein compared with untreated muscle. These data are consistent with the notion that activation of AMPK, presumably as a result of fuel depletion, rapidly regulates UCP-3 gene expression.
Collapse
MESH Headings
- AMP-Activated Protein Kinases
- Animals
- Blotting, Northern
- Carrier Proteins/biosynthesis
- DNA Probes/metabolism
- Electrophoresis, Polyacrylamide Gel
- Fatty Acids, Nonesterified/metabolism
- Hypoxia/enzymology
- Hypoxia/metabolism
- In Vitro Techniques
- Ion Channels
- Male
- Mitochondria, Muscle/enzymology
- Mitochondria, Muscle/metabolism
- Mitochondrial Proteins
- Multienzyme Complexes/metabolism
- Muscle Proteins/metabolism
- Muscle, Skeletal/enzymology
- Muscle, Skeletal/metabolism
- Physical Exertion/physiology
- Protein Serine-Threonine Kinases/metabolism
- RNA, Messenger/biosynthesis
- RNA, Messenger/isolation & purification
- Rats
- Rats, Sprague-Dawley
- Running/physiology
- Swimming/physiology
- Uncoupling Protein 3
Collapse
Affiliation(s)
- M Zhou
- Department of Biochemistry, Boston University School of Medicine, Massachusetts 02118, USA
| | | | | | | | | |
Collapse
|
74
|
Woods A, Azzout-Marniche D, Foretz M, Stein SC, Lemarchand P, Ferré P, Foufelle F, Carling D. Characterization of the role of AMP-activated protein kinase in the regulation of glucose-activated gene expression using constitutively active and dominant negative forms of the kinase. Mol Cell Biol 2000; 20:6704-11. [PMID: 10958668 PMCID: PMC86183 DOI: 10.1128/mcb.20.18.6704-6711.2000] [Citation(s) in RCA: 320] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In the liver, glucose induces the expression of a number of genes involved in glucose and lipid metabolism, e.g., those encoding L-type pyruvate kinase and fatty acid synthase. Recent evidence has indicated a role for the AMP-activated protein kinase (AMPK) in the inhibition of glucose-activated gene expression in hepatocytes. It remains unclear, however, whether AMPK is involved in the glucose induction of these genes. In order to study further the role of AMPK in regulating gene expression, we have generated two mutant forms of AMPK. One of these (alpha1(312)) acts as a constitutively active kinase, while the other (alpha1DN) acts as a dominant negative inhibitor of endogenous AMPK. We have used adenovirus-mediated gene transfer to express these mutants in primary rat hepatocytes in culture in order to determine their effect on AMPK activity and the transcription of glucose-activated genes. Expression of alpha1(312) increased AMPK activity in hepatocytes and blocked completely the induction of a number of glucose-activated genes in response to 25 mM glucose. This effect is similar to that observed following activation of AMPK by 5-amino-imidazolecarboxamide riboside. Expression of alpha1DN markedly inhibited both basal and stimulated activity of endogenous AMPK but had no effect on the transcription of glucose-activated genes. Our results suggest that AMPK is involved in the inhibition of glucose-activated gene expression but not in the induction pathway. This study demonstrates that the two mutants we have described will provide valuable tools for studying the wider physiological role of AMPK.
Collapse
Affiliation(s)
- A Woods
- Cellular Stress Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital, London, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
75
|
Pesi R, Micheli V, Jacomelli G, Peruzzi L, Camici M, Garcia-Gil M, Allegrini S, Tozzi MG. Cytosolic 5'-nucleotidase hyperactivity in erythrocytes of Lesch-Nyhan syndrome patients. Neuroreport 2000; 11:1827-31. [PMID: 10884027 DOI: 10.1097/00001756-200006260-00006] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Lesch-Nyhan syndrome is a metabolic-neurological syndrome caused by the X-linked deficiency of the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT). Metabolic consequences of HGPRT deficiency have been clarified, but the connection with the neurological manifestations is still unknown. Much effort has been directed to finding other alterations in purine nucleotides in different cells of Lesch-Nyhan patients. A peculiar finding was the measure of appreciable amount of Z-nucleotides in red cells. We found significantly higher IMP-GMP-specific 5'-nucleotidase activity in the erythrocytes of seven patients with Lesch-Nyhan syndrome than in healthy controls. The same alteration was found in one individual with partial HGPRT deficiency displaying a severe neurological syndrome, and in two slightly hyperuricemic patients with a psychomotor delay. Since ZMP was a good substrate of 5'-nucleotidase producing Z-riboside, we incubated murine and human cultured neuronal cells with this nucleoside and found that it is toxic for our models, promoting apoptosis. This finding suggests an involvement of the toxicity of the Z-riboside in the pathogenesis of neurological disorders in Lesch-Nyhan syndrome and possibly in other pediatric neurological syndromes of uncertain origin.
Collapse
Affiliation(s)
- R Pesi
- Dipartimento di Fisiologia e Biochimica, Università di Pisa, Italy
| | | | | | | | | | | | | | | |
Collapse
|
76
|
Winder WW, Hardie DG. AMP-activated protein kinase, a metabolic master switch: possible roles in type 2 diabetes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:E1-10. [PMID: 10409121 DOI: 10.1152/ajpendo.1999.277.1.e1] [Citation(s) in RCA: 446] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adenosine 5'-monophosphate-activated protein kinase (AMPK) now appears to be a metabolic master switch, phosphorylating key target proteins that control flux through metabolic pathways of hepatic ketogenesis, cholesterol synthesis, lipogenesis, and triglyceride synthesis, adipocyte lipolysis, and skeletal muscle fatty acid oxidation. Recent evidence also implicates AMPK as being responsible for mediating the stimulation of glucose uptake induced by muscle contraction. In addition, the secretion of insulin by insulin secreting (INS-1) cells in culture is modulated by AMPK activation. The net effect of AMPK activation is stimulation of hepatic fatty acid oxidation and ketogenesis, inhibition of cholesterol synthesis, lipogenesis, and triglyceride synthesis, inhibition of adipocyte lipolysis and lipogenesis, stimulation of skeletal muscle fatty acid oxidation and muscle glucose uptake, and modulation of insulin secretion by pancreatic beta-cells. In skeletal muscle, AMPK is activated by contraction. Type 2 diabetes mellitus is likely to be a disease of numerous etiologies. However, defects or disuse (due to a sedentary lifestyle) of the AMPK signaling system would be predicted to result in many of the metabolic perturbations observed in Type 2 diabetes mellitus. Increased recruitment of the AMPK signaling system, either by exercise or pharmaceutical activators, may be effective in correcting insulin resistance in patients with forms of impaired glucose tolerance and Type 2 diabetes resulting from defects in the insulin signaling cascade.
Collapse
Affiliation(s)
- W W Winder
- Department of Zoology, Brigham Young University, Provo, Utah 84602, USA.
| | | |
Collapse
|
77
|
McCully JD, Levitsky S. Alternatives for myocardial protection: adenosine-enhanced ischemic preconditioning. Ann N Y Acad Sci 1999; 874:295-305. [PMID: 10415541 DOI: 10.1111/j.1749-6632.1999.tb09245.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Intrinsic to the development of new myoprotective protocols for use in cardiac surgery are the requirements of new protocols to be equal to or better than conventional cardioplegia in providing for enhanced post-ischemic functional recovery and decreased myocardial infarct size. Our data suggest that adenosine-enhanced ischemic preconditioning, in which a bolus injection of adenosine to the myocardium is used coincident with ischemic preconditioning, meets these requirements, providing equal cardioprotection as that of cold blood cardioplegia, significantly decreasing myocardial infarct size and significantly enhancing post-ischemic myocardial functional recovery in both the isolated perfused rabbit heart and in the in situ blood-perfused sheep heart. These results further suggest that adenosine-enhanced ischemic preconditioning may provide an effective, alternative myocardial protective protocol to reduce the morbidity and mortality in cardiac surgery.
Collapse
Affiliation(s)
- J D McCully
- Division of Cardiothoracic Surgery, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
| | | |
Collapse
|
78
|
Samari HR, Seglen PO. Inhibition of hepatocytic autophagy by adenosine, aminoimidazole-4-carboxamide riboside, and N6-mercaptopurine riboside. Evidence for involvement of amp-activated protein kinase. J Biol Chem 1998; 273:23758-63. [PMID: 9726984 DOI: 10.1074/jbc.273.37.23758] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To examine the role of AMP-activated protein kinase (AMPK; EC 2.7.1. 109) in the regulation of autophagy, rat hepatocytes were incubated with the AMPK proactivators, adenosine, 5-amino-4-imidazole carboxamide riboside (AICAR), or N6-mercaptopurine riboside. Autophagic activity was inhibited by all three nucleosides, AICAR and N6-mercaptopurine riboside being more potent (IC50 = 0.3 mM) than adenosine (IC50 = 1 mM). 2'-Deoxycoformycin, an adenosine deaminase (EC 3.5.4.4) inhibitor, increased the potency of adenosine 5-fold, suggesting that the effectiveness of adenosine as an autophagy inhibitor was curtailed by its intracellular deamination. 5-Iodotubercidin, an adenosine kinase (EC 2.7.1.20) inhibitor, abolished the effects of all three nucleosides, indicating that they needed to be phosphorylated to inhibit autophagy. A 5-iodotubercidin-suppressible phosphorylation of AICAR to 5-aminoimidazole-4-carboxamide riboside monophosphate was confirmed by chromatographic analysis. AICAR, up to 0.4 mM, had no significant effect on intracellular ATP concentrations. Because activated AMPK phosphorylates and inactivates 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase (EC 1.1.1.88), the rate-limiting enzyme in cholesterol synthesis, the strong inhibition of hepatocytic cholesterol synthesis by all three nucleosides confirmed their ability to activate AMPK under the conditions used. Lovastatin and simvastatin, inhibitors of HMG-CoA reductase, strongly suppressed cholesterol synthesis while having no effect on autophagic activity, suggesting that AMPK inhibits autophagy independently of its effects on HMG-CoA reductase and cholesterol metabolism.
Collapse
Affiliation(s)
- H R Samari
- Department of Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, N-0310 Oslo, Norway
| | | |
Collapse
|
79
|
Stefanelli C, Stanic I, Bonavita F, Flamigni F, Pignatti C, Guarnieri C, Caldarera CM. Inhibition of glucocorticoid-induced apoptosis with 5-aminoimidazole-4-carboxamide ribonucleoside, a cell-permeable activator of AMP-activated protein kinase. Biochem Biophys Res Commun 1998; 243:821-6. [PMID: 9500985 DOI: 10.1006/bbrc.1998.8154] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The AMP-activated protein kinase (AMPK) is related to a growing family of protein kinases that are believed to protect cells against environmental and nutritional stress. In the present study the hypothesis of a protective role for AMPK against thymocyte apoptosis has been tested. It is shown that AMPK is expressed in rat thymocytes that contain the transcript for the a1 isoform of the AMPK catalytic subunit and can be activated by treatment with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), a well-established activator of AMPK. AICAR is not toxic and prevents glucocorticoid-induced apoptosis in the same concentration range used to activate AMPK. At concentrations higher than 1 mM, AICAR fully restores cell viability and inhibits DNA laddering in dexamethasone-treated thymocytes. Furthermore, AICAR blocks the dexamethasone-induced activation of caspase 3-like enzymes, which are believed to play a pivotal role in apoptotic cell death. Activation of AMPK by oligomycin, which depletes thymocytes of ATP, is also correlated to inhibition of caspase 3-like activity in dexamethasone-treated cells. However, AICAR and oligomycin do not exert any protective action when apoptosis is induced by staurosporine. These results indicate that AICAR is a powerful inhibitor of glucocorticoid-induced apoptosis and suggest that AMPK activation may interfere with a step in the apoptotic cascade triggered by dexamethasone.
Collapse
Affiliation(s)
- C Stefanelli
- Department of Biochemistry G. Moruzzi, University of Bologna, Italy.
| | | | | | | | | | | | | |
Collapse
|
80
|
Van den Berghe G, Vincent MF, Jaeken J. Inborn errors of the purine nucleotide cycle: adenylosuccinase deficiency. J Inherit Metab Dis 1997; 20:193-202. [PMID: 9211192 DOI: 10.1023/a:1005304722259] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Adenylosuccinase catalyses two reactions in purine metabolism: the conversion of succinylaminoimidazole carboxamide ribotide (SAICAR) into aminoimidazole carboxamide ribotide (AICAR) along the de novo synthesis of purine nucleotides, and the conversion of adenylosuccinate (S-AMP) into AMP in the conversion of IMP into AMP. The hallmarks of adenylosuccinase deficiency are the presence of succinylaminoimidazole carboxamide riboside (SAICAriboside) and succinyladenosine (S-Ado) in body fluids. These normally undetectable succinylpurines are the products of the dephosphorylation, by cytosolic 5'-nucleotidase, of the two substrates of adenylosuccinase. The clinical picture of the enzyme deficiency is markedly heterogeneous with, as a rule, a profound, but nevertheless variable degree of psychomotor delay, often convulsions and/or autistic features, sometimes growth retardation and muscular dystrophy. The diagnostic tests that can be used for diagnosis, the enzyme and gene defects that have been identified, and the hypotheses that have been put forward to explain the pathophysiology of the disorder are reviewed.
Collapse
Affiliation(s)
- G Van den Berghe
- Laboratory of Physiological Chemistry, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
| | | | | |
Collapse
|
81
|
Hardie DG, Carling D. The AMP-activated protein kinase--fuel gauge of the mammalian cell? EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 246:259-73. [PMID: 9208914 DOI: 10.1111/j.1432-1033.1997.00259.x] [Citation(s) in RCA: 999] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A single entity, the AMP-activated protein kinase (AMPK), phosphorylates and regulates in vivo hydroxymethylglutaryl-CoA reductase and acetyl-CoA carboxylase (key regulatory enzymes of sterol synthesis and fatty acid synthesis, respectively), and probably many additional targets. The kinase is activated by high AMP and low ATP via a complex mechanism, which involves allosteric regulation, promotion of phosphorylation by an upstream protein kinase (AMPK kinase), and inhibition of dephosphorylation. This protein-kinase cascade represents a sensitive system, which is activated by cellular stresses that deplete ATP, and thus acts like a cellular fuel gauge. Our central hypothesis is that, when it detects a 'low-fuel' situation, it protects the cell by switching off ATP-consuming pathways (e.g. fatty acid synthesis and sterol synthesis) and switching on alternative pathways for ATP generation (e.g. fatty acid oxidation). Native AMP-activated protein kinase is a heterotrimer consisting of a catalytic alpha subunit, and beta and gamma subunits, which are also essential for activity. All three subunits have homologues in budding yeast, which are components of the SNF1 protein-kinase complex. SNF1 is activated by glucose starvation (which in yeast leads to ATP depletion) and genetic studies have shown that it is involved in derepression of glucose-repressed genes. This raises the intriguing possibility that AMPK may regulate gene expression in mammals. AMPK/SNF1 homologues are found in higher plants, and this protein-kinase cascade appears to be an ancient system which evolved to protect cells against the effects of nutritional or environmental stress.
Collapse
Affiliation(s)
- D G Hardie
- Biochemistry Department, The University, Dundee, UK.
| | | |
Collapse
|
82
|
Downs SM. Involvement of purine nucleotide synthetic pathways in gonadotropin-induced meiotic maturation in mouse cumulus cell-enclosed oocytes. Mol Reprod Dev 1997; 46:155-67. [PMID: 9021747 DOI: 10.1002/(sici)1098-2795(199702)46:2<155::aid-mrd6>3.0.co;2-p] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This study was carried out to test the hypothesis that purine nucleotide-generating pathways are required for ligand-stimulated oocyte maturation in meiotically arrested cumulus cell-enclosed oocytes. Oocytes from hormonally primed, immature mice were cultured overnight in Eagle's minimum essential medium containing dibutyryl cyclic AMP (dbcAMP) (to maintain meiotic arrest), plus either mycophenolic acid or alanosine (inhibitors of guanyl and adenyl nucleotide production, respectively). Follicle-stimulating hormone (FSH) was added either at the outset of culture or after a 3-hr preincubation period. Under either of these conditions, the inhibitors suppressed FSH induction of germinal vesicle breakdown (GVB). In addition, the potency of FSH as an inducer of GVB was reduced following the 3-hr preincubation period, but this could be prevented if nucleotide precursors such as hypoxanthine, guanosine, or adenosine were included during the first 3 hr. Furthermore, preincubation had little effect on FSH induction of GVB when hypoxanthine was used to maintain meiotic arrest for the entire culture period. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, could not mimic this protective effect of hypoxanthine. Azaserine and aminopterin, inhibitors of purine de novo synthesis, blocked hormone-triggered maturation in dbcAMP-arrested oocytes, but had little effect on hypoxanthine-arrested oocytes. The effect of azaserine on dbcAMP-treated oocytes could be reversed by the inclusion of AICA riboside, a compound that can be taken up by cells and phosphorylated to form AICAR, which can enter the purine de novo pathway at a point distal to the sites of azaserine inhibition. FSH was stimulatory to purine de novo synthesis, while azaserine, aminopterin, hypoxanthine, and AICA riboside all suppressed de novo synthesis in the presence or absence of FSH, with dbcAMP having no effect. HPLC analysis of 14C-hypoxanthine metabolism in oocyte-cumulus cell complexes revealed that changes in the pattern of purine metabolism did not mediate the meiosis-inducing effect of FSH. These data support the conclusion that purine nucleotide-generating pathways are vital participants in the mechanism(s) regulating hormone-induced meiotic maturation, and that either the de novo or salvage pathway can fulfill this nucleotide requirement.
Collapse
Affiliation(s)
- S M Downs
- Department of Biology, Marquette University, Milwaukee, Wisconsin 53201-1881, USA
| |
Collapse
|
83
|
Vincent MF, Bontemps F, Van den Berghe G. Substrate cycling between 5-amino-4-imidazolecarboxamide riboside and its monophosphate in isolated rat hepatocytes. Biochem Pharmacol 1996; 52:999-1006. [PMID: 8831718 DOI: 10.1016/0006-2952(96)00413-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
AICA (5-amino-4-imidazolecarboxamide)-riboside is taken up by isolated rat hepatocytes and converted by adenosine kinase (ATP:adenosine 5'-phosphotransferase, EC 2.7.1.20) into AICAR (ZMP), an intermediate of the de novo synthesis of purine nucleotides. We investigated if, in these cells, a cycle analogous to the adenosine-AMP substrate cycle operates between AICAriboside and ZMP. When 50 microM ITu, an inhibitor of adenosine kinase, was added to hepatocytes that had metabolized AICAriboside for 30 min, the concentration of ZMP decreased immediately. This was mirrored by a reincrease of AICAriboside. Rates of the ITu-induced decrease of ZMP and the increase of AICAriboside, calculated at different concentrations of ZMP, were first order, up to the highest concentration of ZMP (approx. 5 mumol/g of cells). Dephosphorylation of ZMP added to crude cytosolic extracts of rat liver displayed hyperbolic kinetics, with a Vmax of 0.65 mumol/min per g protein and an apparent Km of 5 mM, and was markedly inhibited by Pi, an inhibitor of IMP-GMP 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5). We conclude that hepatocyte ZMP is continuously dephosphorylated, most likely by IMP-GMP 5'-nucleotidase, into AICAriboside, which is rephosphorylated into ZMP by adenosine kinase. Substrate cycling was also shown to occur between other nucleoside analogs and their phosphorylated counterparts.
Collapse
Affiliation(s)
- M F Vincent
- Laboratory of Physiological Chemistry, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
| | | | | |
Collapse
|
84
|
Abstract
We have previously demonstrated that in isolated hepatocytes from fasted rats, AICAriboside (5-amino 4-imidazolecarboxamide riboside), after its conversion into AICAribotide (AICAR or ZMP), exerts a dose-dependent inhibition on fructose-1,6-bisphosphatase and hence on gluconeogenesis. To assess the effect of AICAriboside in vivo, we measured plasma glucose and liver metabolites after intraperitoneal administration of AICAriboside in mice. In fasted animals, in which gluconeogenesis is activated, AICAriboside (250 mg/kg body weight) induced a 50% decrease of plasma glucose within 15 min, which lasted about 3 h. In fed mice, glucose decreased by 8% at 30 min, and normalized at 1 h. Under both conditions, ZMP accumulated to approximately 2 mumol/g of liver at 1 h. It decreased progressively thereafter, although much more slowly in the fasted state. Inhibition of fructose-1,6-bisphosphatase was evidenced by time-wise linear accumulations of fructose-1,6-bisphosphate, from 0.006 to 3.9 mumol/g of liver at 3 h in fasted mice, and from 0.010 to 0.114 mumol/g of liver at 1 h in fed animals. AICAriboside did not significantly influence plasma insulin or glucose utilization by muscle. We conclude that in vivo as in isolated hepatocytes, AICAriboside, owing to its conversion into ZMP, inhibits fructose-1,6-bisphosphatase and consequently gluconeogenesis.
Collapse
Affiliation(s)
- M F Vincent
- Laboratory of Physiological Chemistry, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
| | | | | | | |
Collapse
|
85
|
Amplification of Endogenous Adenosine by “Adenosine Regulating Agents” as a Therapeutic Approach to the Treatment of Cardiac Ischemic Syndromes. ACTA ACUST UNITED AC 1996. [DOI: 10.1007/978-1-4613-0455-5_15] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
86
|
Corton JM, Gillespie JG, Hawley SA, Hardie DG. 5-aminoimidazole-4-carboxamide ribonucleoside. A specific method for activating AMP-activated protein kinase in intact cells? EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 229:558-65. [PMID: 7744080 DOI: 10.1111/j.1432-1033.1995.tb20498.x] [Citation(s) in RCA: 934] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The AMP-activated protein kinase (AMPK) is believed to protect cells against environmental stress (e.g. heat shock) by switching off biosynthetic pathways, the key signal being elevation of AMP. Identification of novel targets for the kinase cascade would be facilitated by development of a specific agent for activating the kinase in intact cells. Incubation of rat hepatocytes with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) results in accumulation of the monophosphorylated derivative (5-aminoimidazole-4-carboxamide ribonucleoside; ZMP) within the cell. ZMP mimics both activating effects of AMP on AMPK, i.e. direct allosteric activation and promotion of phosphorylation by AMPK kinase. Unlike existing methods for activating AMPK in intact cells (e.g. fructose, heat shock), AICAR does not perturb the cellular contents of ATP, ADP or AMP. Incubation of hepatocytes with AICAR activates AMPK due to increased phosphorylation, causes phosphorylation and inactivation of a known target for AMPK (3-hydroxy-3-methylglutaryl-CoA reductase), and almost total cessation of two of the known target pathways, i.e. fatty acid and sterol synthesis. Incubation of isolated adipocytes with AICAR antagonizes isoprenaline-induced lipolysis. This provides direct evidence that the inhibition by AMPK of activation of hormone-sensitive lipase by cyclic-AMP-dependent protein kinase, previously demonstrated in cell-free assays, also operates in intact cells. AICAR should be a useful tool for identifying new target pathways and processes regulated by the protein kinase cascade.
Collapse
Affiliation(s)
- J M Corton
- Department of Biochemistry, University, Dundee, Scotland
| | | | | | | |
Collapse
|
87
|
Alkhulaifi AM, Pugsley WB. Role of acadesine in clinical myocardial protection. BRITISH HEART JOURNAL 1995; 73:304-5. [PMID: 7756061 PMCID: PMC483821 DOI: 10.1136/hrt.73.4.304] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
|
88
|
Sullivan JE, Brocklehurst KJ, Marley AE, Carey F, Carling D, Beri RK. Inhibition of lipolysis and lipogenesis in isolated rat adipocytes with AICAR, a cell-permeable activator of AMP-activated protein kinase. FEBS Lett 1994; 353:33-6. [PMID: 7926017 DOI: 10.1016/0014-5793(94)01006-4] [Citation(s) in RCA: 378] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In vivo, hormone-sensitive lipase (HSL) is known to be phosphorylated on two sites termed the regulatory and basal sites. However, the intracellular role of the basal site or the identity of the protein kinase phosphorylating this site has not been established. We show that 5-amino-4-imidazolecarboxamide ribonucleoside (AICAR) markedly activates cellular AMP-activated protein kinase (AMPK) in a time- and dose-dependent manner. As expected for an agent that activates AMPK intracellularly, AICAR had no effect on the basal activity of HSL. However, preincubation of adipocytes with AICAR led to a reduced response of these cells to the lipolytic agent isoprenaline. AICAR was also shown to profoundly inhibit lipogenesis through increased phosphorylation of acetyl-CoA carboxylase (ACC). Thus it appears that in addition to regulating lipogenesis, AMPK also plays an important antilipolytic role by regulating HSL in rat adipocytes.
Collapse
Affiliation(s)
- J E Sullivan
- Cardiovascular and Metabolism Research Department, ZENECA Pharmaceuticals, Alderley Park, Cheshire, UK
| | | | | | | | | | | |
Collapse
|
89
|
Stet EH, De Abreu RA, Bökkerink JP, Vogels-Mentink TM, Lambooy LH, Trijbels FJ, Trueworthy RC. Reversal of 6-mercaptopurine and 6-methylmercaptopurine ribonucleoside cytotoxicity by amidoimidazole carboxamide ribonucleoside in Molt F4 human malignant T-lymphoblasts. Biochem Pharmacol 1993; 46:547-50. [PMID: 8347177 DOI: 10.1016/0006-2952(93)90534-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Cytotoxicity of 6-mercaptopurine (6MP) and 6-methylmercaptopurine ribonucleoside (Me-MPR) was studied in Molt F4 human malignant lymphoblasts. Both drugs are converted into methylthioIMP (Me-tIMP), which inhibits purine de novo synthesis. Addition of amidoimidazole carboxamide ribonucleoside (AICAR) circumvented inhibition of purine de novo synthesis, and thus partly prevented 6MP and Me-MPR cytotoxicity. Purine nucleotides, and especially adenine nucleotides, were recovered by addition of AICAR. Under these conditions, Me-tIMP formation decreased. The results of this study indicate that formation of Me-tIMP may be important for 6MP cytotoxicity in Molt F4 cells. These data suggest that depletion of adenine nucleotides is the main cause for Me-tIMP cytotoxicity.
Collapse
Affiliation(s)
- E H Stet
- Department of Pediatrics, St. Radboud University Hospital of Nijmegen, The Netherlands
| | | | | | | | | | | | | |
Collapse
|
90
|
Van den Berghe G, Bontemps F, Vincent MF, Van den Bergh F. The purine nucleotide cycle and its molecular defects. Prog Neurobiol 1992; 39:547-61. [PMID: 1529104 DOI: 10.1016/0301-0082(92)90006-z] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Three enzymes of purine metabolism, adenylosuccinate synthetase, adenylosuccinate lyase and AMP deaminase, have been proposed to form a functional unit, termed the purine nucleotide cycle. This cycle converts AMP into IMP and reconverts IMP into AMP via adenylosuccinate, thereby producing NH3 and forming fumarate from aspartate. In muscle, the purine nucleotide cycle has been shown to function during intense exercise; the metabolic flux through the cycle has been proposed to play a role in the regeneration of ATP by pulling the adenylate kinase reaction in the direction of formation of ATP, and by providing Krebs cycle intermediates. In kidney, the purine nucleotide cycle was shown to account for the release of NH3 under the normal acid-base status, but not under acidotic conditions. In brain, the purine nucleotide cycle might function under conditions that induce a loss of ATP, and thereby contribute to its recovery. There is no evidence that the purine nucleotide cycle operates in liver. Deficiency of muscle AMP deaminase is an apparently frequent disorder, which might affect approximately 2% of the general population. The observation that it can be found in clinically asymptomatic individuals suggests, paradoxically, that the ATP-regenerating function which has been attributed to the purine nucleotide cycle is not essential for muscle function. Further work should be aimed at identifying the conditions under which AMP deaminase deficiency becomes symptomatic. Adenylosuccinate lyase deficiency provokes psychomotor retardation, often accompanied by autistic features. Its clinical heterogeneity justifies systematic screening in patients with unexplained mental deficiency. Additional studies are required to determine the mechanisms whereby this enzyme defect results in psychomotor retardation.
Collapse
Affiliation(s)
- G Van den Berghe
- Laboratory of Physiological Chemistry, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
| | | | | | | |
Collapse
|
91
|
Barton JW, Hart IM, Patterson D. Mapping of a locus correcting lack of phosphoribosylaminoimidazole carboxylase activity in Chinese hamster ovary cell Ade-D mutants to human chromosome 4. Genomics 1991; 9:314-21. [PMID: 2004782 DOI: 10.1016/0888-7543(91)90259-h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The human phosphoribosylaminoimidazole (AIR) carboxylase locus has been until this report one of the genes encoding purine biosynthetic enzymes that had not been assigned to an individual human chromosome. Characterization of Chinese hamster ovary (CHO) cell mutant Ade-D showed that the cell line was unable to produce IMP and accumulated AIR. CHO Ade-D cells were fused with normal human lymphocytes utilizing inactivated Sendai virus and the resulting hybrid cell lines were selected for purine prototrophy. Cytogenetic analysis showed a 100% concordance value for chromosome 4. Two of the isolated subclones contained only the long arm of chromosome 4 translocated onto a CHO chromosome, providing evidence for a regional assignment of the Ade-D gene to the long arm of chromosome 4. Two of the subclones containing chromosome 4 were subjected to the BrdU visible light segregation. All of the isolated purine auxotrophic cell lines showed a loss of the q arm of chromosome 4. The localization of the Ade-D locus to the long arm of chromosome 4 may reveal further clustering of the mammalian purine genes since the Ade-A locus has previously been regionally assigned to 4pter-q21.
Collapse
Affiliation(s)
- J W Barton
- Eleanor Rossevelt Institute for Cancer Research, Denver, Colorado 80206
| | | | | |
Collapse
|
92
|
Barankiewicz J, Jimenez R, Uyesaka J, Gruber HE. Regulation of adenosine concentrations by acadesine (AICA-riboside) in human B-lymphoblasts. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1991; 309A:275-8. [PMID: 1789225 DOI: 10.1007/978-1-4899-2638-8_62] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
|
93
|
Gruber HE, Jimenez R, Barankiewicz J. Z-nucleotides formation in human and rat cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1991; 309B:363-6. [PMID: 1781398 DOI: 10.1007/978-1-4615-7703-4_82] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- H E Gruber
- Gensia Pharmaceuticals, Inc., San Diego, CA 92121
| | | | | |
Collapse
|
94
|
Vincent MF, Marangos P, Gruber HE, Van den Berghe G. AICAriboside inhibits gluconeogenesis in isolated rat hepatocytes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1991; 309B:359-62. [PMID: 1664185 DOI: 10.1007/978-1-4615-7703-4_81] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- M F Vincent
- International Institute of Cellular and Molecular Pathology, Brussels, Belgium
| | | | | | | |
Collapse
|
95
|
Rohlman CE, Matthews RG. Role of purine biosynthetic intermediates in response to folate stress in Escherichia coli. J Bacteriol 1990; 172:7200-10. [PMID: 2254281 PMCID: PMC210845 DOI: 10.1128/jb.172.12.7200-7210.1990] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Folic acid plays a central role in anabolic metabolism by supplying single-carbon units at varied levels of oxidation for both nucleotide and amino acid biosyntheses. It has been proposed that 5-amino-4-imidazole carboxamide riboside 5'-triphosphate (ZTP), an intermediate in de novo purine biosynthesis, serves as a signal of cellular folate stress and mediates a physiologically beneficial response to folate stress in Salmonella typhimurium (B. R. Bochner, and B. N. Ames, Cell 29:929-937, 1982). We examined the physiological response of Escherichia coli to folate stress induced by the drugs psicofuranine, trimethoprim, and sodium sulfathiazole or by p-aminobenzoic acid (pABA) starvation. Analysis of nucleotide pools showed that psicofuranine or trimethoprim treatment of a prototrophic strain or growth of a pABA auxotroph on limiting pABA induced the production of the nucleotide ZTP, as previously observed in S. typhimurium by Bochner and Ames. Accumulation of ZTP and its precursor 5-amino-4-imidazole carboxamide riboside 5'-monophosphate (ZMP) did not correlate well with folate stress in E. coli, as measured by determination of the folate/protein ratios of extracts of treated cells. Treatment of cells with psicofuranine caused a marked accumulation of 5-amino-4-imidazole carboxamide ribonucleotides (Z-ribonucleotides) but a statistically insignificant drop in the folate/protein ratio of cell extracts. Sodium sulfathiazole treatment at a drug concentration that led to a threefold drop in the growth rate and in the folate/protein ratio of treated cells led to little accumulation of Z-ribonucleotides in E. coli A purF his+ strain which produces ZTP and ZMP when treated with trimethoprim was constructed. In this strain, histidine represses the synthesis of both ZMP and ZTP. Treatment of cells of this strain with trimethoprim resulted in a decrease in the folate/protein ratio of cell extracts, but a blockade of Z-ribonucleotide accumulation did not affect the extent of folate depletion seen in treated cells and had only a small effect on the resistance of this strain to growth inhibition by trimethoprim. The patterns of protein expression induced by treatment of this strain with trimethoprim or psicofuranine were examined by two-dimensional electrophoretic resolution of the total cellular proteins. No differences in protein expression were seen when the treatment were performed in media containing or lacking histidine. These studies failed to provide evidence in E. coli for a folate stress regulon controlled by ZTP.
Collapse
Affiliation(s)
- C E Rohlman
- Department of Biological Chemistry, University of Michigan, Ann Arbor 48109
| | | |
Collapse
|
96
|
Barankiewicz J, Jimenez R, Ronlov G, Magill M, Gruber HE. Alteration of purine metabolism by AICA-riboside in human B lymphoblasts. Arch Biochem Biophys 1990; 282:377-85. [PMID: 1700665 DOI: 10.1016/0003-9861(90)90132-i] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The effect of 5-amino-4-imidazole-carboximide (AI-CA)-riboside on different pathways of purine metabolism (biosynthesis de novo, salvage pathways, adenosine metabolism, ATP catabolism) was studied in human B lymphoblasts (WI-L2). AICA-Riboside markedly decreased intracellular levels of 5-phosphoribosyl-1-pyrophosphate and in consequence affected purine biosynthesis de novo and purine salvage pathways. AICA-riboside inhibited incorporation of glycine into purine nucleotides, but when formate was used as the precursor of purine biosynthesis de novo, a biphasic effect was observed. The incorporation of formate into purine nucleotides was increased by AICA-riboside at concentrations up to 2 mM but decreased at higher concentrations. Salvage of the purine bases adenine, hypoxanthine, and guanine was markedly inhibited and utilization of extracellular adenosine in B lymphoblasts was reduced by AICA-riboside. AICA-riboside increased ribose 1-phosphate concentrations and increased degradation of prelabeled ATP. No effect on the intracellular levels of orthophosphate was found. Proliferation of WI-L2 lymphoblasts was only slightly affected at concentrations of AICA-riboside below 500 microM but markedly inhibited by higher concentrations.
Collapse
Affiliation(s)
- J Barankiewicz
- Gensia Pharmaceuticals, Inc., Research Department, San Diego, California 92121
| | | | | | | | | |
Collapse
|
97
|
Foley JM, Adams GR, Meyer RA. Utility of AICAr for metabolic studies is diminished by systemic effects in situ. THE AMERICAN JOURNAL OF PHYSIOLOGY 1989; 257:C488-94. [PMID: 2782392 DOI: 10.1152/ajpcell.1989.257.3.c488] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
It has been reported that intraperitoneal infusion of 5-amino-4-imidazolecarboxamide riboside (AICAr) inhibits the purine nucleotide cycle, resulting in rapid fatigue of isometric twitch force during stimulation of rat muscle. In this study, peak isometric twitch force was recorded from gastrocnemius muscles of pentobarbital-anesthetized rats stimulated in situ at 0.75 Hz after intraperitoneal infusion of 9ml/100 g body wt of 250 mM AICAr or isotonic saline. Excluding the two AICAr-infused rats that died during infusion or stimulation, there was no difference in twitch force between groups, although mean arterial pressure in the AICAr group declined to values 20 Torr below those of the control group during drug infusion. High-resolution 1H nuclear magnetic resonance (NMR) spectroscopy of extracts verified the presence of AICAr and AICA ribotide (AICAR) in muscles of experimental animals. In a second study in which rats were mounted head down in an NMR spectrometer, AICAr infusion resulted in decreased mean arterial pressure and impairment of phosphocreatine recovery after stimulation but no significant difference in twitch force during stimulation. These results demonstrate that AICAr infusion has systemic effects and that the previously reported decline in muscle force with AICAr infusion may not be attributable to purine nucleotide cycle inhibition.
Collapse
Affiliation(s)
- J M Foley
- Department of Physiology, Michigan State University, East Lansing 48824
| | | | | |
Collapse
|
98
|
Nissim I, Yudkoff M, Nissim I, States B. Effect of 5-amino-4-imidazolecarboxamide riboside (AICA-riboside) on the purine nucleotide synthesis and growth of rat kidney cells in culture: study with [15N]aspartate. J Cell Physiol 1989; 138:536-40. [PMID: 2925797 DOI: 10.1002/jcp.1041380313] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The present investigation evaluates the effect of AICA-Riboside on the synthesis of purine nucleotides and the growth of normal rat kidney cells in culture. Experiments in the presence and absence of various concentrations of AICA-Riboside were conducted with Dulbecco's Modified Eagle's Medium supplemented with either 1 mM [15N]aspartate or [14N]aspartate. Addition of 50 microM AICA-Riboside to the incubation medium significantly stimulated intracellular adenine nucleotide concentrations following incubation for 48 hours. This stimulation was associated with augmented cell growth and DNA concentration. In contrast, with concentrations above 100 microM of AICA-Riboside in the incubation medium, there was a remarkable inhibition of cell growth and a significant depletion of intracellular pools of adenine nucleotides and DNA. Experiments with [15N]aspartate showed that the initial rate (0-24 hours) of [6-15NH2]adenine nucleotide formation from 1 mM [15N]aspartate was 38.8 +/- 9.6, 67.9 +/- 12.5, and 20.1 +/- 3.8 pmol h-1/10(6) cells in the presence of 0 (control), 50 microM and 500 microM AICA-Riboside, respectively. These observations indicate that the main effect of AICA-Riboside is on the formation of AMP from aspartate and IMP via the sequential action of adenylosuccinate synthetase and adenylosuccinate lyase. The current studies suggest that AICA-Riboside could be used as a factor mediating renal cell mitosis in culture. AICA-Riboside has a biphasic effect on the growth of renal epithelial cells in culture and on their intracellular purine nucleotides and DNA concentration.
Collapse
Affiliation(s)
- I Nissim
- Division of Biochemical Development and Molecular Diseases, Children's Hospital, Philadelphia, Pennsylvania
| | | | | | | |
Collapse
|
99
|
Hards RG, Patterson D. Resolution of the intermediates of de novo purine biosynthesis by ion-pair reversed-phase high-performance liquid chromatography. J Chromatogr A 1988; 455:217-24. [PMID: 3235612 DOI: 10.1016/s0021-9673(01)82120-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
An ion-pair reversed-phase high-performance liquid chromotographic procedure capable of resolving twelve of the fourteen intermediates of de novo purine biosynthesis is presented. The method utilizes isocratic elution and detection by ultraviolet light absorption. Separation of all twelve intermediates can be achieved in 90 min.
Collapse
Affiliation(s)
- R G Hards
- Eleanor Roosevelt Institute for Cancer Research, Denver, CO 80206
| | | |
Collapse
|
100
|
|