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Guan BJ, Krokowski D, Majumder M, Schmotzer CL, Kimball SR, Merrick WC, Koromilas AE, Hatzoglou M. Translational control during endoplasmic reticulum stress beyond phosphorylation of the translation initiation factor eIF2α. J Biol Chem 2014; 289:12593-611. [PMID: 24648524 DOI: 10.1074/jbc.m113.543215] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The accumulation of unfolded/misfolded proteins in the endoplasmic reticulum (ER) causes stress to which an unfolded protein response is activated to render cell survival or apoptosis (chronic stress). Transcriptional and translational reprogramming is tightly regulated during the unfolded protein response to ensure specific gene expression. The master regulator of this response is the PERK/eIF2α/ATF4 signaling where eIF2α is phosphorylated (eIF2α-P) by the kinase PERK. This signal leads to global translational shutdown, but it also enables translation of the transcription factor ATF4 mRNA. We showed recently that ATF4 induces an anabolic program through the up-regulation of selected amino acid transporters and aminoacyl-tRNA synthetases. Paradoxically, this anabolic program led cells to apoptosis during chronic ER stress in a manner that involved recovery from stress-induced protein synthesis inhibition. By using eIF2α-P-deficient cells as an experimental system, we identified a communicating network of signaling pathways that contribute to the inhibition of protein synthesis during chronic ER stress. This eIF2α-P-independent network includes (i) inhibition of mammalian target of rapamycin kinase protein complex 1 (mTORC1)-targeted protein phosphorylation, (ii) inhibited translation of a selective group of 5'-terminal oligopyrimidine mRNAs (encoding proteins involved in the translation machinery and translationally controlled by mTORC1 signaling), and (iii) inhibited translation of non-5'-terminal oligopyrimidine ribosomal protein mRNAs and ribosomal RNA biogenesis. We propose that the PERK/eIF2α-P/ATF4 signaling acts as a brake in the decline of protein synthesis during chronic ER stress by positively regulating signaling downstream of the mTORC1 activity. These studies advance our knowledge on the complexity of the communicating signaling pathways in controlling protein synthesis rates during chronic stress.
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Ortiz V, Alemán G, Escamilla-Del-Arenal M, Recillas-Targa F, Torres N, Tovar AR. Promoter characterization and role of CRE in the basal transcription of the rat SNAT2 gene. Am J Physiol Endocrinol Metab 2011; 300:E1092-102. [PMID: 21386061 DOI: 10.1152/ajpendo.00459.2010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Small neutral amino acid transporter 2 (SNAT2) is the most abundant and ubiquitous transporter for zwitterionic short-chain amino acids. The activity of this amino acid transporter is stimulated in vivo or in vitro by glucagon or cAMP analogs. However, it is not known whether the increase in activity at the protein level is due to an increase in SNAT2 gene transcription. Thus, the aim of the present work was to study whether cAMP was able to stimulate SNAT2 gene expression and to localize and characterize the presence of cAMP response elements (CRE) in the promoter that controls the expression of the rat SNAT2 gene. We found that consumption of a high-protein diet that increased serum glucagon concentration or the administration of glucagon or incubation of hepatocytes with forskolin increased the SNAT2 mRNA level. We then isolated the 5' regulatory region of the SNAT2 gene and determined that the transcriptional start site was located 970 bp upstream of the translation start codon. We identified two potential CRE sites located at -354 and -48 bp. Our results, using deletion analysis of the 5' regulatory region of the SNAT2 gene, revealed that the CRE site located at -48 bp was fully responsible for SNAT2 regulation by cAMP. This evidence was strongly supported by mutation of the CRE site and EMSA and ChIP analysis. Alignment of rat, mouse, and human sequences revealed that this CRE site is highly conserved among species, indicating its essential role in the regulation of SNAT2 gene expression.
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Affiliation(s)
- Victor Ortiz
- Departamento de Fisiología de la Nutrición, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Vasco de Quiroga 15, Mexico
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Wasa M, Wang HS, Okada A. Characterization of L-glutamine transport by a human neuroblastoma cell line. Am J Physiol Cell Physiol 2002; 282:C1246-53. [PMID: 11997238 DOI: 10.1152/ajpcell.00324.2001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study characterized the Na+-dependent transport of L-glutamine by a human neuroblastoma cell line, SK-N-SH. The Na+-dependent component represented >95% of the total glutamine uptake. Kinetic studies showed a single saturable high-affinity carrier with a Michaelis constant (K(m)) of 163 +/- 23 microM and a maximum transport velocity (Vmax) of 13,713 +/- 803 pmol x mg protein(-1) x min(-1). Glutamine uptake was markedly inhibited in the presence of L-alanine, L-asparagine, and L-serine. Li+ did not substitute for Na+. These data show that L-glutamine is predominantly taken up through system ASC. Glutamine deprivation resulted in the decrease of glutamine transport by a mechanism that decreased Vmax without affecting K(m). The expression of the system ASC subtype ASCT2 decreased in the glutamine-deprived group, whereas glutamine deprivation did not induce changes in system ASC subtype ASCT1 mRNA expression. Adaptive increases in Na+-dependent glutamate, Na+-dependent 2-(methylamino)isobutyric acid, and Na+-independent leucine transport were observed under glutamine-deprived conditions, which were completely blocked by actinomycin D and cycloheximide. These mechanisms may allow cells to survive and even grow under nutrient-deprived conditions.
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Affiliation(s)
- Masafumi Wasa
- Department of Pediatric Surgery, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
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Wasa M, Wang HS, Tazuke Y, Okada A. Insulin-like growth factor-I stimulates amino acid transport in a glutamine-deprived human neuroblastoma cell line. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1525:118-24. [PMID: 11342260 DOI: 10.1016/s0304-4165(00)00178-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
It is still unknown how insulin-like growth factor-I (IGF-I) regulates cancer cell growth in the condition of the limited availability of key nutrients, such as glutamine. We investigated the effects of IGF-I on cell growth and amino acid transport in a glutamine-deprived human neuroblastoma cell line, SK-N-SH. Cell growth was measured, and 3H-labeled amino acid transport was assayed after treatment with or without IGF-I (50 ng/ml) in 2 mM (control) and 100 microM glutamine concentrations. Cell growth rates were dependent on glutamine concentrations. IGF-I stimulated cell growth in both 2 mM and 100 microM glutamine. IGF-I stimulated glutamine transport in 100 microM glutamine with the mechanism of increasing carrier Vmax, but had no effect in 2 mM glutamine. IGF-I also stimulated leucine, glutamate and 2-(methylamino)isobutyric acid transport in 100 microM glutamine. There were significant increases in [3H]thymidine and [3H]leucine incorporation in IGF-I-treated cells in both 2 mM and 100 microM glutamine. These data suggest that IGF-I stimulates cell growth by increasing amino acid transport in the condition of low glutamine levels in a human neuroblastoma cell line. This mechanism may allow to maintain cell growth even in nutrient-deprived tumor tissues.
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Affiliation(s)
- M Wasa
- Department of Pediatric Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, 565-0871, Osaka, Japan.
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Franchi-Gazzola R, Visigalli R, Bussolati O, Dall'Asta V, Gazzola GC. Adaptive increase of amino acid transport system A requires ERK1/2 activation. J Biol Chem 1999; 274:28922-8. [PMID: 10506137 DOI: 10.1074/jbc.274.41.28922] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Amino acid starvation markedly stimulates the activity of system A, a widely distributed transport route for neutral amino acids. The involvement of MAPK (mitogen-activated protein kinase) pathways in this adaptive increase of transport activity was studied in cultured human fibroblasts. In these cells, a 3-fold stimulation of system A transport activity required a 6-h amino acid-free incubation. However, a rapid tyrosine phosphorylation of ERK (extracellular regulated kinase) 1 and 2, and JNK (Jun N-terminal kinase) 1, but not of p38, was observed after the substitution of complete medium with amino acid-free saline solution. ERK1/2 activity was 4-fold enhanced after a 15-min amino acid-free incubation and maintained at stimulated values thereafter. A transient, less evident stimulation of JNK1 activity was also detected, while the activity of p38 was not affected by amino acid deprivation. PD98059, an inhibitor of ERK1/2 activation, completely suppressed the adaptive increase of system A transport activity that, conversely, was unaffected by inhibitors of other transduction pathways, such as rapamycin and wortmannin, as well as by chronic treatment with phorbol esters. In the presence of either L-proline or 2-(methylaminoisobutyric) acid, two substrates of system A, the transport increase was prevented and no sustained stimulation of ERK1/2 was observed. To identify the stimulus that maintains MAPK activation, cell volume was monitored during amino acid-free incubation. It was found that amino acid deprivation caused a progressive cell shrinkage (30% after a 6-h starvation). If proline was added to amino acid-starved, shrunken cells, normal values of cell volume were rapidly restored. However, proline-dependent volume rescue was hampered if cells were pretreated with PD98059. It is concluded that (a) the triggering of adaptive increase of system A activity requires a prolonged activation of ERK1 and 2 and that (b) cell volume changes, caused by the depletion of intracellular amino acid pool, may underlie the activation of MAPKs.
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Affiliation(s)
- R Franchi-Gazzola
- Istituto di Patologia Generale, Plesso Biotecnologico Integrato, Università degli Studi di Parma, via Volturno 39, 43100 Parma, Italy
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Handlogten ME, Dudenhausen EE, Yang W, Kilberg MS. Association of hepatic system A amino acid transporter with the membrane-cytoskeletal proteins ankyrin and fodrin. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1282:107-14. [PMID: 8679646 DOI: 10.1016/0005-2736(96)00046-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
System A activity is a highly regulated mechanism for the active transport of zwitterionic amino acids into mammalian cells. Monoclonal antibodies generated against a previously unidentified rat liver plasma membrane-associated protein were shown to immunoprecipitate solubilized System A transport activity. The immunoreactive protein was later determined by immunoblotting and peptide microsequencing to be rat liver alpha-fodrin (non-erythroid spectrin). Antibody against ankyrin, a protein that often serves as a bridge between integral membrane proteins and fodrin, also immunoprecipitated System A transport activity. Fractionation of solubilized plasma membrane proteins on sucrose gradients revealed that the System A transporter co-migrated as a complex with fodrin and ankyrin, even in the presence of detergent and urea. In contrast, the System N amino acid transporter does not co-migrate with ankyrin and fodrin, nor does the anti-fodrin antibody immunoprecipitate System N activity. The present data are the first to demonstrate an association between an organic solute transporter and the membranocytoskeletal proteins ankyrin and fodrin.
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Affiliation(s)
- M E Handlogten
- Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, JHMHC, Gainesville 32610, USA
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Laine RO, Hutson RG, Kilberg MS. Eukaryotic gene expression: metabolite control by amino acids. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1996; 53:219-48. [PMID: 8650304 DOI: 10.1016/s0079-6603(08)60146-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Our understanding of the metabolite control in mammalian cells lags far behind that in prokaryotes. This is particularly true for amino-acid-dependent gene expression. Few proteins have been identified for which synthesis is selectively regulated by amino-acid availability, and the mechanisms for control of transcription and translation in response to changes in amino-acid availability have not yet been elucidated. The intimate relationship between amino-acid supply and the fundamental cellular process of protein synthesis makes amino-acid-dependent control of gene expression particularly important. Future studies should provide important insight into amino-acid and other nutrient signaling pathways, and their impact on cellular growth and metabolism.
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Affiliation(s)
- R O Laine
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville 32610, USA
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Wasa M, Bode BP, Souba WW. Adaptive regulation of amino acid transport in nutrient-deprived human hepatomas. Am J Surg 1996; 171:163-9. [PMID: 8554134 DOI: 10.1016/s0002-9610(99)80093-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Malignant cells require increased amounts of amino acids, in particular glutamine and leucine, to support DNA and protein biosynthesis. Although plasma concentrations in the center of solid tumors can be much lower than normal circulating levels, it is still unknown how tumor cells can survive despite low amino acid levels. We examined the effects of glutamine or leucine deprivation on cell growth and amino acid transport activity in two human hepatoma cell lines, SK-Hep and HepG2. METHODS We studied the transport of glutamine, leucine, alanine, and arginine. The carrier-mediated uptake of 3H-amino acids was determined in cells cultured in normal and amino acid-deprived media. RESULTS The growth of both cell lines was dependent on the concentration of glutamine and leucine. In SK-Hep, there was a significant increase in initial rate glutamine transport activity in the glutamine-deprived group, attributable to an increase in transporter affinity (Km; 0.6 mmol/L [control], 385 +/- 43 mumol/L; 0.1 mmol/L, 221 +/- 11 mumol/L; P < 0.01). At low glutamine concentration, the saturable Na(+)-independent uptake of leucine and arginine as well as the Na(+)-dependent uptake of alanine increased significantly in both SK-Hep and HepG2. Similarly, in leucine-deprived SK-Hep cells, leucine uptake increased twofold, but the change was attributable to an enhanced transporter capacity (Vmax; 0.2 mmol/L [control], 38,900 +/- 700; 0.0 mmol/L, 75,900 +/- 4,900 pmol/mg protein per minute; P < 0.001). CONCLUSIONS Adaptive increases in initial rate amino acid transport activities were elicited by glutamine and leucine deprivation in these two human hepatoma cell lines. Decreased extracellular amino acid levels encountered by tumors in vivo may elicit similar adaptive responses that contribute to the maintenance of cytoplasmic levels of amino acids essential for growth.
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Affiliation(s)
- M Wasa
- Division of Surgical Oncology, Massachusetts General Hospital, Boston 02114, USA
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Lim SK, De Bandt JP, Aussel C, Pernet P, Giboudeau J, Cynober L. No evidence for a tumor necrosis factor alpha stimulated 2-methylaminoisobutyric acid uptake in hepatocyte monolayer. J Cell Physiol 1995; 162:422-6. [PMID: 7860649 DOI: 10.1002/jcp.1041620314] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
This study investigates the short-term effects of glucagon and human recombinant tumor necrosis factor alpha (TNF alpha) singly and in association on 2-methylaminoisobutyric acid (MeAIB) transport in hepatocyte monolayers. As expected, glucagon induced a time-dependent stimulation of MeAIB transport. In our experimental conditions, TNF alpha did not induce cytolysis. A 2 hour exposure to TNF alpha (0.05-500 ng/l) with or without glucagon (10(-9) to 10(-6) M) did not modify the basal or glucagon-stimulated MeAIB transport. Varying the duration of exposure to TNF alpha 5 ng/l up to 6 h was equally ineffective. The presence of hydrocortisone potentiated the glucagon-stimulated transport, but TNF alpha remained ineffective. Finally, the association of interferon (IFN gamma) with TNF alpha and/or glucagon was unable to modify the transport activity. These data demonstrate that TNF alpha does not exert a direct effect on MeAIB transport in hepatocytes, at least on a short-term basis.
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Affiliation(s)
- S K Lim
- Laboratoire de Biochimie A, Hôpital Saint-Antoine, Paris, France
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Mailliard ME, Stevens BR, Mann GE. Amino acid transport by small intestinal, hepatic, and pancreatic epithelia. Gastroenterology 1995; 108:888-910. [PMID: 7875494 DOI: 10.1016/0016-5085(95)90466-2] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- M E Mailliard
- Department of Medicine, College of Medicine, University of Florida, Gainesville
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Chapter 5 Biosynthesis 7. How Can N-Linked Glycosylation and Processing Inhibitors be Used to Study Carbohydrate Synthesis and Function. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s0167-7306(08)60599-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Mailliard ME, Cariappa R, Banks RK. Impairment of glucagon-induced hepatic system A activity by short-term ethanol administration in the rat. Gastroenterology 1994; 106:480-7. [PMID: 8299914 DOI: 10.1016/0016-5085(94)90608-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
BACKGROUND/AIMS System A is a membrane-bound, hormonally regulated carrier of amino acids that is induced by liver regeneration and impaired by ethanol. The mechanism of ethanol inhibition of system A is unknown; this study examines the effects of ethanol on the subcellular expression of system A activity following hormonal induction. METHODS Following hormonal treatment and short-term ethanol administration to rats, isolated liver Golgi and plasma membrane vesicles were examined for system A transport, and the kinetic parameters were determined. RESULTS Four hours after ethanol administration, the initial rate of system A activity was depressed 30% +/- 9% and 19% +/- 7% into Golgi and plasma membrane vesicles, respectively. The affinity constant of 2-(methylamino)-isobutyric acid uptake was unchanged between control and ethanol-treated vesicles, regardless of their subcellular origin. However, the maximal velocity of system A transport decreased from 1030 to 850 pmol.mg-1 protein.10 s-1 in Golgi vesicles and from 740 to 355 pmol.mg-1 protein.10 s-1 in plasma membrane vesicles. CONCLUSIONS Ethanol impairs hormonally induced system A activity in Golgi as well as in the plasma membrane vesicles. Ethanol potentially reduces glucagon induction of system A activity through an impairment of carrier biosynthesis or expression.
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Affiliation(s)
- M E Mailliard
- Department of Medicine, University of Florida, Gainesville
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Cariappa R, Kilberg MS. Plasma membrane domain localization and transcytosis of the glucagon-induced hepatic system A carrier. THE AMERICAN JOURNAL OF PHYSIOLOGY 1992; 263:E1021-8. [PMID: 1335691 DOI: 10.1152/ajpendo.2006.263.6.e1021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We have utilized canalicular (cLPM) and basolateral (blLPM) liver plasma membrane vesicles to investigate the domain localization of several Na(+)-dependent amino acid transporters. Neutral amino acid transport by systems N and ASC was measurable in both domains but was greater in blLPM vesicles. Sodium-dependent glutamate uptake (system X-) was preferentially localized to cLPM. The absolute activity and domain distribution of these three carriers remained unchanged after treatment of rats with a combination of glucagon and dexamethasone. A low level of basal system A activity was present in both the blLPM and cLPM. Glucagon-induced system A activity was first observed in blLPM vesicles approximately 60 min posthormone treatment and, in cLPM vesicles, approximately 30 min later. In situ perfusion of glucagon-treated rat liver with the membrane-impermeant protein modification reagent glutathione maleimide specifically inactivated blLPM system A activity and abolished the delayed arrival of hormone-induced activity to the cLPM. Transient perfusion of the liver with glutathione maleimide followed by a recovery period in vivo showed that the reagent did not irreversibly inactivate the transcytotic process and also provided an independent demonstration of the time delay between arrival of the carrier activity at the two membrane surfaces. These results support the concept of a transcytotic process in which the blLPM is the sorting site for the hormone-induced system A carrier proteins that eventually reach the cLPM.
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Affiliation(s)
- R Cariappa
- Department of Biochemistry and Molecular Biology, J. Hillis Miller Health Center, University of Florida, Gainesville 32610
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Tovar AR, Tews JK, Torres N, Harper AE. Neutral amino acid transport into rat skeletal muscle: competition, adaptive regulation, and effects of insulin. Metabolism 1991; 40:410-9. [PMID: 2011083 DOI: 10.1016/0026-0495(91)90153-n] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Amino acid (AA) transport systems A and L, which transfer preferentially small neutral AA (SNAA) and large neutral AA (LNAA), respectively, were studied in the isolated soleus muscle with the specific models, 2-(methylamino)isobutyrate (MeAIB) and 2-aminobicyclo[2,2,1]heptane-2-carboxylate (BCH). Affinity for MeAIB was greater than for BCH (Km = 3.2 +/- 0.2 and 8.7 +/- 0.2 mm, respectively). Rate of transport of MeAIB (Vmax = 104 +/- 3 pmol/microL/min) was slower than for BCH (970 +/- 12 pmol/microL/min), but accumulation was far more concentrative; transport of BCH, but not MeAIB, rapidly reached a steady-state level. MeAIB transport was reduced in the presence of SNAA; BCH transport was reduced to a lesser extent only by LNAA. Mixtures of AA at concentrations resembling those in plasmas of rats fed either a 6% or 50% casein diet reduced transport of MeAIB, whereas BCH transport was low only with the latter mixture. Only MeAIB transport was stimulated by insulin. Preincubation of muscles for 5 hours in a AA-free medium stimulated subsequent MeAIB uptake by about twofold to fourfold; this effect was suppressed by inhibitors of protein synthesis. Selective differences were thus observed in transport by skeletal muscle of model AA for the A and L systems: increased transport resulting from various stimuli was limited to the model for the A system, and transport of either model was depressed with mixtures containing physiological levels of AA. Changes in dietary protein or AA intake may thus alter transport of certain neutral AA into skeletal muscle via changes in plasma AA pools.
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Affiliation(s)
- A R Tovar
- Department of Nutritional Sciences, College of Agricultural and Life Sciences, University of Wisconsin-Madison
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Bertran J, Roca A, Pola E, Testar X, Zorzano A, Palacín M. Modification of system A amino acid carrier by diethyl pyrocarbonate. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(17)35243-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Cheeseman CI. Molecular mechanisms involved in the regulation of amino acid transport. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1991; 55:71-84. [PMID: 1871316 DOI: 10.1016/0079-6107(91)90001-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- C I Cheeseman
- Department of Physiology, University of Alberta, Edmonton, Canada
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Metcalfe HK, Cohen RD, Monson JP. Hormonal modulation of hepatic plasma membrane lactate transport in cultured rat hepatocytes. Biosci Rep 1990; 10:573-7. [PMID: 2085671 DOI: 10.1007/bf01116618] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Hormonal modulation of hepatic plasma membrane lactate transport was studied in primary cultures of isolated hepatocytes from fed rats to examine the mechanism for the known enhancement of lactate transport in starvation and diabetes. Total cellular lactate entry was increased by 14% in the presence of dexamethasone; this was accounted for by an approximately 40% increase in the carrier-mediated component of entry with no effect on diffusion. A trend of similar magnitude was evident with glucagon. The effects of dexamethasone and glucagon on lactate transport constitute an additional potential mechanism for enhancement of gluconeogenesis by these hormones.
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Affiliation(s)
- H K Metcalfe
- Cellular Mechanisms Group, London Hospital Medical College, U.K
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18
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Molecular cloning of an amino acid-regulated mRNA (amino acid starvation-induced) in rat hepatoma cells. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(18)38240-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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19
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Tarnuzzer R, Campa M, Qian N, Englesberg E, Kilberg M. Expression of the mammalian system A neutral amino acid transporter in Xenopus oocytes. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(18)77435-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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20
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Fong AD, Handlogten ME, Kilberg MS. Substrate-dependent adaptive regulation and trans-inhibition of System A-mediated amino acid transport. Studies using rat hepatoma plasma membrane vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1022:325-32. [PMID: 1690572 DOI: 10.1016/0005-2736(90)90281-r] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Substrate-dependent regulation of amino acid transport by System A occurs by both direct action at the carrier (trans-inhibition) and transcriptional control (adaptive regulation). While experiments with intact cells have led to working models that describe these regulatory phenomena, the use of subcellular approaches will serve to refine the present hypotheses. Adaptive induction of System A transport following amino acid starvation of cells was shown to be dependent on de novo RNA and protein synthesis, and the stimulated activity was shown to be retained in isolated plasma membrane vesicles. This stimulated transport activity was tightly associated with the plasma membrane, but could be solubilized by 4 M urea and 2.5% cholate, and recovered following reconstitution of the protein into artificial proteoliposomes. These data support the working hypothesis that adaptive induction of transport is the result of de novo synthesis and insertion into the plasma membrane of System A carrier protein. In contrast, the activity of System ASC in the vesicles from the amino acid starved cells was actually reduced by 2-5-fold when compared to amino acid-fed cells. A more rapid form of regulation of System A activity is trans-inhibition. The use of isolated plasma membrane vesicles demonstrated that trans-inhibition in whole cells did not survive membrane isolation. However, substrate loading of isolated membrane vesicles containing high levels of System A activity, produced trans-inhibition in a very specific manner in that System A substrates resulted in decreased transport activity, while those amino acids which are poor substrates for the System A carrier did not. Thus, trans-inhibition is not the result of a recycling process involving an intracellular pool of carriers, but rather can be accounted for by differences in the kinetics for amino acid binding and/or translocation on the two sides of the membrane.
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Affiliation(s)
- A D Fong
- Department of Biochemistry and Molecular Biology, J. Hillis Miller Health Center, University of Florida, College of Medicine, Gainesville 32610
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21
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Hormone-induced system A amino acid transport activity in rat liver plasma membrane and Golgi vesicles. Evidence for a differential sensitivity to inactivation by N-ethylmaleimide during carrier maturation. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)40040-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Handlogten ME, Kilberg MS. Growth-dependent regulation of system A in SV40-transformed fetal rat hepatocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1988; 255:C261-70. [PMID: 2844092 DOI: 10.1152/ajpcell.1988.255.3.c261] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Fetal RLA209-15 hepatocytes, transformed with a temperature-sensitive SV40 mutant, behave like fully differentiated cells at the growth-restrictive temperature of 40 degrees C. Conversely, incubation at the growth-permissive temperature of 33 degrees C results in a transformed phenotype characterized by rapid cell division and decreased production of liver-specific proteins. The results presented here demonstrate that the cells at 33 degrees C exhibited high rates of system A transport, but transfer to 40 degrees C reduced the activity greater than 50% within 24 h. This decline in transport was independent of cell density, although the basal rate of uptake was inversely proportional to cell density in rapidly dividing cells. Transfer of cells from 40 to 33 degrees C resulted in an enhancement of system A activity that was blocked by tunicamycin. Plasma membrane vesicles from cells maintained at either 33 or 40 degrees C retained uptake rates proportional to those in the intact cells; this difference in transport activity could also be demonstrated after detergent solubilization and reconstitution. Collectively, these data indicate that de novo synthesis of the system A carrier is regulated in conjunction with temperature-dependent cell growth in RLA209-15 hepatocytes.
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Affiliation(s)
- M E Handlogten
- Department of Biochemistry and Molecular Biology, University of Florida School of Medicine, Gainesville 32610
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23
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Saier MH, Daniels GA, Boerner P, Lin J. Neutral amino acid transport systems in animal cells: potential targets of oncogene action and regulators of cellular growth. J Membr Biol 1988; 104:1-20. [PMID: 3054116 DOI: 10.1007/bf01871898] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- M H Saier
- Department of Biology, University of California, San Diego, La Jolla 92093
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Evidence for inherent differences in the system A carrier from normal and transformed liver tissue. Differential inactivation and substrate protection in membrane vesicles and reconstituted proteoliposomes. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)45242-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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25
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Bracy DS, Schenerman MA, Kilberg MS. Solubilization and reconstitution of hepatic System A-mediated amino acid transport. Preparation of proteoliposomes containing glucagon-stimulated transport activity. BIOCHIMICA ET BIOPHYSICA ACTA 1987; 899:51-8. [PMID: 3567191 DOI: 10.1016/0005-2736(87)90238-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
System A-mediated amino acid transport activity from rat liver plasma membrane vesicles has been solubilized and reconstituted into proteoliposomes using a freeze-thaw-dilution technique. The presence of cholate, at a cholate to protein ratio of 1:1, during the freeze-thaw step resulted in an enhancement in recoverable transport activity. The carrier required both phosphatidylcholine and phosphatidylethanolamine for optimal activity, but the addition of cholesterol to the reconstitution procedure appeared to have no significant effect on the resulting activity. A lipid to protein ratio of 20:1 yielded maximal transport activity. Sonication of the proteoliposomes provided some improvement in the accuracy of replicate assays for a given proteoliposome preparation. Isolated liver plasma membrane vesicles prepared from rats treated in vivo with glucagon in combination with dexamethasone contained stimulated System A activity. This enhanced transport activity could be solubilized and recovered in proteoliposomes generated from these plasma membranes. The data support the proposal that hormone regulation of the hepatic System A gene results in the de novo synthesis and plasma membrane insertion of the carrier protein itself.
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Schenerman MA, Kilberg MS. Maintenance of glucagon-stimulated system A amino acid transport activity in rat liver plasma membrane vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 856:428-36. [PMID: 3964688 DOI: 10.1016/0005-2736(86)90133-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Plasma membrane vesicles prepared from intact rat liver or isolated hepatocytes retain transport activity by systems A, ASC, N, and Gly. Selective substrates for these systems showed a Na+-dependent overshoot indicative of energy-dependent transport, in this instance, driven by an artificially-imposed Na+ gradient. Greater than 85% of Na+-dependent 2-aminoisobutyric acid (AIB) uptake was blocked by an excess of 2-(methylamino)isobutyric acid (MeAIB) with an apparent Ki of 0.6 mM. Intact hepatocytes obtained from glucagon-treated rats exhibited a stimulation of system A activity and plasma membrane vesicles isolated from those same cells partially retained the elevated activity. Transport activity induced by substrate starvation of cultured hepatocytes was also evident in membrane vesicles prepared from those cells. The membrane-bound glucagon-stimulated system A activity decays rapidly during incubation of vesicles at 4 degrees C (t1/2 = 13 h), but not at -75 degrees C. Several different inhibitors of proteolysis were ineffective in blocking the decay of transport activity. Hepatic system N transport activity was also elevated in plasma membrane vesicles from glucagon-treated rats, whereas system ASC was essentially unchanged. The results indicate that both glucagon and adaptive regulation cause an induction of amino acid transport through a plasma membrane-associated protein.
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Bracy DS, Handlogten ME, Barber EF, Han HP, Kilberg MS. Cis-inhibition, trans-inhibition, and repression of hepatic amino acid transport mediated by System A. Substrate specificity and other properties. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)35969-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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29
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Handlogten ME, Barber EF, Bracy DS, Kilberg MS. Amino acid-dependent inactivation of glucagon-induced System A transport activity in cultured rat hepatocytes. Mol Cell Endocrinol 1985; 43:61-9. [PMID: 4065425 DOI: 10.1016/0303-7207(85)90042-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Hepatocytes isolated from glucagon-treated rats contain stimulated System A activity. If these cells are placed in primary culture, the enhanced transport decays rapidly provided the culture medium contains substrate amino acids. This amino acid-dependent inactivation can be composed of trans-inhibition (protein synthesis-independent), repression (protein synthesis-dependent), or both depending on the particular substrate tested. Repression was most prominently observed with a group of small neutral amino acids that are commonly found in proteins. A strong trans-inhibition response was induced by a variety of amino acid analogs. Amino acids showing no reactivity with System A produced neither trans-inhibition nor repression. Repression of System A activity in culture was blocked by inhibitors of both RNA and protein synthesis. In contrast to inhibitors of RNA biosynthesis such as actinomycin and alpha-amanitin, inhibitors of poly(A) polymerase (cordycepin and adenine-9-beta-D-arabinopyranoside) did not prevent the inactivation of the transport activity. These results demonstrate that both the stimulation of activity and the turnover of the hepatic System A activity are controlled at the transcriptional level.
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30
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Kilberg MS, Han HP, Barber EF, Chiles TC. Adaptive regulation of neutral amino acid transport System A in rat H4 hepatoma cells. J Cell Physiol 1985; 122:290-8. [PMID: 2578476 DOI: 10.1002/jcp.1041220219] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Substrate regulation of System A transport activity in rat H4 hepatoma cells is described. The uptake of several amino acids was tested in the presence of system-specific inhibitors. System A activity was increased in a RNA- and protein synthesis-dependent manner by amino acid deprivation of the cells (adaptive regulation), whereas transport by Systems ASC, N, y+, and L was unaffected. Unlike human fibroblasts, the H4 cells did not require serum to exhibit the depression of System A. At cell densities between 88 X 10(3) and 180 X 10(3) cells/cm2, the degree of adaptive regulation was inversely related to cell density. Both transport of AIB and adaptive regulation of System A were nearly abolished if either K+ or Li+ was substituted for Na+ in the medium. The presence of cycloheximide or tunicamycin blocked further increases in starvation-induced activity within 1 hr of addition, suggesting the involvement of a plasma membrane glycoprotein. In contrast, if the medium was supplemented with actinomycin after the stimulation of System A had begun, the activity continued to increase for an additional 2 hr before being slowed by the inhibitor. The contributions of trans-inhibition and repression to the amino acid-induced decay of System A activity were estimated for several representative amino acids. In general, the System A activity in normal rat hepatocytes was much less sensitive to trans-inhibition than the corresponding activity in H4 hepatoma cells. The half-life values for the amino acid-dependent decay of System A ranged from 0.5 to 2.0 hr.
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31
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Kilberg MS, Barber EF, Handlogten ME. Characteristics and hormonal regulation of amino acid transport system A in isolated rat hepatocytes. CURRENT TOPICS IN CELLULAR REGULATION 1985; 25:133-63. [PMID: 2410197 DOI: 10.1016/b978-0-12-152825-6.50009-6] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Lerner J. Effectors of amino acid transport processes in animal cell membranes. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1985; 81:713-39. [PMID: 2863064 DOI: 10.1016/0300-9629(85)90903-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Various effectors, which act upon ion gradients, protein synthesis, membrane components or cellular functional groups, have been employed to provide insights into the nature of amino acid-membrane transport processes in animal cells. Such effectors, for example, include ions, hormones, metabolites and various organic reagents and their judicious use has allowed the following list of conclusions. Sodium ion has been found to stimulate amino acid transport in a wide variety of cell systems, although depending on the tissue and/or substrate, this ion may have no effect on such transport, or even inhibit it. Amino acid transport can be stimulated in some cell systems by other ions such as K+, Li+, H+ or Cl-. Both H+ and K+ have been found to be inhibitory in other systems. Amino acid transport is dependent in many cell systems upon an inwardly directed Na+ gradient and is stimulated by a membrane potential (negative cell interior). In some cell systems an inwardly directed Cl- and H+ gradient or an outwardly directed K+ gradient can energize transport. Structurally dissimilar effectors such as ouabain, Clostridium enterotoxin, aspirin and amiloride inhibit amino acid transport presumably through dissipation of the Na+ gradient. Inhibition by certain sugars or metabolic intermediates of the tricarboxylic acid cycle may compete with the substrate for the energy of the Na+ gradient or interact with the substrate at the carrier level either allosterically or at a common site. Stimulation of transport by other sugars or intermediates may result from their catabolism to furnish energy for transport. Insulin and glucagon stimulate transport of amino acids in a variety of cell systems by a mechanism which involves protein synthesis. Microtubules may be involved in the regulation of transport by insulin or glucagon. Some reports also suggest that insulin has a direct effect on membranes. In addition, a number of growth hormones and factors have stimulatory effects on amino acid transport which are also mediated by protein synthesis. Steroid hormones have been noted to enhance or diminish transport of amino acids depending on the nature of the hormone. These agents appear to function at the level of protein synthesis. While stimulation may involve increased carrier synthesis, inhibition probably involves synthesis of a labile protein which either decreases the rate of synthesis or increases the rate of degradation of a component of the transport system.(ABSTRACT TRUNCATED AT 400 WORDS)
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Handlogten ME, Kilberg MS. Induction and decay of amino acid transport in the liver. Turnover of transport activity in isolated hepatocytes after stimulation by diabetes or glucagon. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)43125-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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