1
|
Prasad R, Floyd JL, Dupont M, Harbour A, Adu-Agyeiwaah Y, Asare-Bediako B, Chakraborty D, Kichler K, Rohella A, Calzi SL, Lammendella R, Wright J, Boulton ME, Oudit GY, Raizada MK, Stevens BR, Li Q, Grant MB. Maintenance of Enteral ACE2 Prevents Diabetic Retinopathy in Type 1 Diabetes. Circ Res 2023; 132:e1-e21. [PMID: 36448480 PMCID: PMC9822874 DOI: 10.1161/circresaha.122.322003] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 11/16/2022] [Indexed: 12/02/2022]
Abstract
BACKGROUND We examined components of systemic and intestinal renin-angiotensin system on gut barrier permeability, glucose homeostasis, systemic inflammation, and progression of diabetic retinopathy (DR) in human subjects and mice with type 1 diabetes (T1D). METHODS T1D individual with (n=18) and without (n=20) DR and controls (n=34) were examined for changes in gut-regulated components of the immune system, gut leakage markers (FABP2 [fatty acid binding protein 2] and peptidoglycan), and Ang II (angiotensin II); Akita mice were orally administered a Lactobacillus paracasei (LP) probiotic expressing humanized ACE2 (angiotensin-converting enzyme 2) protein (LP-ACE2) as either a prevention or an intervention. Akita mice with genetic overexpression of humanAce2 by small intestine epithelial cells (Vil-Cre.hAce2KI-Akita) were similarly examined. After 9 months of T1D, circulatory, enteral, and ocular end points were assessed. RESULTS T1D subjects exhibit elevations in gut-derived circulating immune cells (ILC1 cells) and higher gut leakage markers, which were positively correlated with plasma Ang II and DR severity. The LP-ACE2 prevention cohort and genetic overexpression of intestinal ACE2 preserved barrier integrity, reduced inflammatory response, improved hyperglycemia, and delayed development of DR. Improvements in glucose homeostasis were due to intestinal MasR activation, resulting in a GSK-3β (glycogen synthase kinase-3 beta)/c-Myc (cellular myelocytomatosis oncogene)-mediated decrease in intestinal glucose transporter expression. In the LP-ACE2 intervention cohort, gut barrier integrity was improved and DR reversed, but no improvement in hyperglycemia was observed. These data support that the beneficial effects of LP-ACE2 on DR are due to the action of ACE2, not improved glucose homeostasis. CONCLUSIONS Dysregulated systemic and intestinal renin-angiotensin system was associated with worsening gut barrier permeability, gut-derived immune cell activation, systemic inflammation, and progression of DR in human subjects. In Akita mice, maintaining intestinal ACE2 expression prevented and reversed DR, emphasizing the multifaceted role of the intestinal renin-angiotensin system in diabetes and DR.
Collapse
Affiliation(s)
- Ram Prasad
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Jason L. Floyd
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Mariana Dupont
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Angela Harbour
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Yvonne Adu-Agyeiwaah
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Bright Asare-Bediako
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Dibyendu Chakraborty
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Kara Kichler
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Aayush Rohella
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Sergio Li Calzi
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | | | | | - Michael E. Boulton
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Gavin Y. Oudit
- Division of Cardiology, Department of Medicine, University of Alberta, Mazankowski Alberta Heart Institute, Edmonton, AB, T6G 2B7, Canada
| | - Mohan K. Raizada
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gainesville, FL, 32610, USA
| | - Bruce R. Stevens
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gainesville, FL, 32610, USA
| | - Qiuhong Li
- Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, FL, 32610, USA
| | - Maria B. Grant
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| |
Collapse
|
2
|
Transport of L-Arginine Related Cardiovascular Risk Markers. J Clin Med 2020; 9:jcm9123975. [PMID: 33302555 PMCID: PMC7764698 DOI: 10.3390/jcm9123975] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 11/30/2020] [Accepted: 12/01/2020] [Indexed: 12/15/2022] Open
Abstract
L-arginine and its derivatives, asymmetric and symmetric dimethylarginine (ADMA and SDMA) and L-homoarginine, have emerged as cardiovascular biomarkers linked to cardiovascular outcomes and various metabolic and functional pathways such as NO-mediated endothelial function. Cellular uptake and efflux of L-arginine and its derivatives are facilitated by transport proteins. In this respect the cationic amino acid transporters CAT1 and CAT2 (SLC7A1 and SLC7A2) and the system y+L amino acid transporters (SLC7A6 and SLC7A7) have been most extensively investigated, so far, but the number of transporters shown to mediate the transport of L-arginine and its derivatives is constantly increasing. In the present review we assess the growing body of evidence regarding the function, expression, and clinical relevance of these transporters and their possible relation to cardiovascular diseases.
Collapse
|
3
|
Ruffin M, Mercier J, Calmel C, Mésinèle J, Bigot J, Sutanto EN, Kicic A, Corvol H, Guillot L. Update on SLC6A14 in lung and gastrointestinal physiology and physiopathology: focus on cystic fibrosis. Cell Mol Life Sci 2020; 77:3311-3323. [PMID: 32166393 PMCID: PMC7426304 DOI: 10.1007/s00018-020-03487-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 01/24/2020] [Accepted: 02/17/2020] [Indexed: 12/17/2022]
Abstract
The solute carrier family 6 member 14 (SLC6A14) protein imports and concentrates all neutral amino acids as well as the two cationic acids lysine and arginine into the cytoplasm of different cell types. Primarily described as involved in several cancer and colonic diseases physiopathological mechanisms, the SLC6A14 gene has been more recently identified as a genetic modifier of cystic fibrosis (CF) disease severity. It was indeed shown to have a pleiotropic effect, modulating meconium ileus occurrence, lung disease severity, and precocity of P. aeruginosa airway infection. The biological mechanisms explaining the impact of SLC6A14 on intestinal and lung phenotypes of CF patients are starting to be elucidated. This review focuses on SLC6A14 in lung and gastrointestinal physiology and physiopathology, especially its involvement in the pathophysiology of CF disease.
Collapse
Affiliation(s)
- Manon Ruffin
- Sorbonne Université, INSERM UMR S 938, Centre de Recherche Saint‑Antoine (CRSA), Paris, France
| | - Julia Mercier
- Sorbonne Université, INSERM UMR S 938, Centre de Recherche Saint‑Antoine (CRSA), Paris, France
| | - Claire Calmel
- Sorbonne Université, INSERM UMR S 938, Centre de Recherche Saint‑Antoine (CRSA), Paris, France
| | - Julie Mésinèle
- Sorbonne Université, INSERM UMR S 938, Centre de Recherche Saint‑Antoine (CRSA), Paris, France
| | - Jeanne Bigot
- Sorbonne Université, INSERM UMR S 938, Centre de Recherche Saint‑Antoine (CRSA), Paris, France
| | - Erika N Sutanto
- Telethon Kids Institute, University of Western Australia, Nedlands, WA, Australia
- School of Public Health, Curtin University, Bentley, WA, Australia
| | - Anthony Kicic
- Telethon Kids Institute, University of Western Australia, Nedlands, WA, Australia
- School of Public Health, Curtin University, Bentley, WA, Australia
- Centre for Cell Therapy and Regenerative Medicine, Medical School, The University of Western Australia, Nedlands, WA, Australia
- Department of Respiratory and Sleep Medicine, Perth Children's Hospital, Nedlands, WA, Australia
| | - Harriet Corvol
- Sorbonne Université, INSERM UMR S 938, Centre de Recherche Saint‑Antoine (CRSA), Paris, France.
- Pneumologie Pédiatrique, APHP, Hôpital Trousseau, Paris, France.
| | - Loic Guillot
- Sorbonne Université, INSERM UMR S 938, Centre de Recherche Saint‑Antoine (CRSA), Paris, France
| |
Collapse
|
4
|
Scalise M, Pochini L, Console L, Losso MA, Indiveri C. The Human SLC1A5 (ASCT2) Amino Acid Transporter: From Function to Structure and Role in Cell Biology. Front Cell Dev Biol 2018; 6:96. [PMID: 30234109 PMCID: PMC6131531 DOI: 10.3389/fcell.2018.00096] [Citation(s) in RCA: 150] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 08/08/2018] [Indexed: 12/30/2022] Open
Abstract
SLC1A5, known as ASCT2, is a neutral amino acid transporter belonging to the SLC1 family and localized in the plasma membrane of several body districts. ASCT2 is an acronym standing for Alanine, Serine, Cysteine Transporter 2 even if the preferred substrate is the conditionally essential amino acid glutamine, with cysteine being a modulator and not a substrate. The studies around amino acid transport in cells and tissues began in the '60s by using radiolabeled compounds and competition assays. After identification of murine and human genes, the function of the coded protein has been studied in cell system and in proteoliposomes revealing that this transporter is a Na+ dependent antiporter of neutral amino acids, some of which are only inwardly transported and others are bi-directionally exchanged. The functional asymmetry merged with the kinetic asymmetry in line with the physiological role of amino acid pool harmonization. An intriguing function has been described for ASCT2 that is exploited as a receptor by a group of retroviruses to infect human cells. Interactions with scaffold proteins and post-translational modifications regulate ASCT2 stability, trafficking and transport activity. Two asparagine residues, namely N163 and N212, are the sites of glycosylation that is responsible for the definitive localization into the plasma membrane. ASCT2 expression increases in highly proliferative cells such as inflammatory and stem cells to fulfill the augmented glutamine demand. Interestingly, for the same reason, the expression of ASCT2 is greatly enhanced in many human cancers. This finding has generated interest in its candidacy as a pharmacological target for new anticancer drugs. The recently solved 3D structure of ASCT2 will aid in the rational design of such therapeutic compounds.
Collapse
Affiliation(s)
- Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Lorena Pochini
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Lara Console
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Maria A Losso
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze Della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Cosenza, Italy.,CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnology, Bari, Italy
| |
Collapse
|
5
|
Abstract
With the global population rising, the need for sustainable and resource-efficiently produced proteins with nutritional and health promoting qualities has become urgent. Proteins are important macronutrients and are involved in most, if not all, biological processes in the human body. This review discusses these absorption mechanisms in the small intestine. To study intestinal transport and predict bioavailability, cell lines are widely applied as screening models and often concern Caco-2, HT-29, HT-29/MTX and T84 cells. Here, we provide an overview of the presence and activities of peptide- and amino acid transporters in these cell models. Further, inter-laboratory differences are discussed as well as the culture micro-environment, both of which may influence cell culture phenotype and performance. Finally, the value of new developments in the field, including culturing cells in 3-dimensional systems under shear stress (i.e., gut-on-chips), is highlighted. In particular, their suitability in screening novel food proteins and prediction of the nutritional quality needed for inclusion in the human diet of the future is addressed.
Collapse
|
6
|
Beaudet AL. Brain carnitine deficiency causes nonsyndromic autism with an extreme male bias: A hypothesis. Bioessays 2017; 39. [PMID: 28703319 DOI: 10.1002/bies.201700012] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Could 10-20% of autism be prevented? We hypothesize that nonsyndromic or "essential" autism involves extreme male bias in infants who are genetically normal, but they develop deficiency of carnitine and perhaps other nutrients in the brain causing autism that may be amenable to early reversal and prevention. That brain carnitine deficiency might cause autism is suggested by reports of severe carnitine deficiency in autism and by evidence that TMLHE deficiency - a defect in carnitine biosynthesis - is a risk factor for autism. A gene on the X chromosome (SLC6A14) likely escapes random X-inactivation (a mixed epigenetic and genetic regulation) and could limit carnitine transport across the blood-brain barrier in boys compared to girls. A mixed, common gene variant-environment hypothesis is proposed with diet, minor illnesses, microbiome, and drugs as possible risk modifiers. The hypothesis can be tested using animal models and by a trial of carnitine supplementation in siblings of probands. Perhaps the lack of any Recommended Dietary Allowance for carnitine in infants should be reviewed. Also see the video abstract here: https://youtu.be/BuRH_jSjX5Y.
Collapse
Affiliation(s)
- Arthur L Beaudet
- Departments of Molecular and Human Genetics and Pediatrics, Baylor College of Medicine, Texas Children's Hospital, Houston, TX, USA
| |
Collapse
|
7
|
Yang C, Yang X, Lackeyram D, Rideout TC, Wang Z, Stoll B, Yin Y, Burrin DG, Fan MZ. Expression of apical Na(+)-L-glutamine co-transport activity, B(0)-system neutral amino acid co-transporter (B(0)AT1) and angiotensin-converting enzyme 2 along the jejunal crypt-villus axis in young pigs fed a liquid formula. Amino Acids 2016; 48:1491-508. [PMID: 26984322 DOI: 10.1007/s00726-016-2210-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 02/29/2016] [Indexed: 01/11/2023]
Abstract
Gut apical amino acid (AA) transport activity is high at birth and during suckling, thus being essential to maintain luminal nutrient-dependent mucosal growth through providing AA as essential metabolic fuel, substrates and nutrient stimuli for cellular growth. Because system-B(0) Na(+)-neutral AA co-transporter (B(0)AT1, encoded by the SLC6A19 gene) plays a dominant role for apical uptake of large neutral AA including L-Gln, we hypothesized that high apical Na(+)-Gln co-transport activity, and B(0)AT1 (SLC6A19) in co-expression with angiotensin-converting enzyme 2 (ACE2) were expressed along the entire small intestinal crypt-villus axis in young animals via unique control mechanisms. Kinetics of Na(+)-Gln co-transport activity in the apical membrane vesicles, prepared from epithelial cells sequentially isolated along the jejunal crypt-villus axis from liquid formula-fed young pigs, were measured with the membrane potential being clamped to zero using thiocyanate. Apical maximal Na(+)-Gln co-transport activity was much higher (p < 0.05) in the upper villus cells than in the middle villus (by 29 %) and the crypt (by 30 %) cells, whereas Na(+)-Gln co-transport affinity was lower (p < 0.05) in the upper villus cells than in the middle villus and the crypt cells. The B(0)AT1 (SLC6A19) mRNA abundance was lower (p < 0.05) in the crypt (by 40-47 %) than in the villus cells. There were no significant differences in B(0)AT1 and ACE2 protein abundances on the apical membrane among the upper villus, the middle villus and the crypt cells. Our study suggests that piglet fast growth is associated with very high intestinal apical Na(+)-neutral AA uptake activities via abundantly co-expressing B(0)AT1 and ACE2 proteins in the apical membrane and by transcribing the B(0)AT1 (SLC6A19) gene in the epithelia along the entire crypt-villus axis.
Collapse
Affiliation(s)
- Chengbo Yang
- Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada. .,Department of Animal Science, Faculty of Agricultural and Food Sciences, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada.
| | - Xiaojian Yang
- Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada.,Southern Research and Outreach Center, University of Minnesota, Waseca, MN, 56093, USA
| | - Dale Lackeyram
- Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Todd C Rideout
- Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada.,Department of Exercise and Nutrition Sciences, the State University of New York at Buffalo, New York, 14214, USA
| | - Zirong Wang
- College of Animal Science, Xinjiang Agricultural University, Urumqi, 830052, Xinjiang, China
| | - Barbara Stoll
- US Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Yulong Yin
- Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, 410125, Hunan, China
| | - Douglas G Burrin
- US Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Ming Z Fan
- Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada.
| |
Collapse
|
8
|
Pochini L, Scalise M, Galluccio M, Indiveri C. Membrane transporters for the special amino acid glutamine: structure/function relationships and relevance to human health. Front Chem 2014; 2:61. [PMID: 25157349 PMCID: PMC4127817 DOI: 10.3389/fchem.2014.00061] [Citation(s) in RCA: 175] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 07/16/2014] [Indexed: 12/26/2022] Open
Abstract
Glutamine together with glucose is essential for body's homeostasis. It is the most abundant amino acid and is involved in many biosynthetic, regulatory and energy production processes. Several membrane transporters which differ in transport modes, ensure glutamine homeostasis by coordinating its absorption, reabsorption and delivery to tissues. These transporters belong to different protein families, are redundant and ubiquitous. Their classification, originally based on functional properties, has recently been associated with the SLC nomenclature. Function of glutamine transporters is studied in cells over-expressing the transporters or, more recently in proteoliposomes harboring the proteins extracted from animal tissues or over-expressed in microorganisms. The role of the glutamine transporters is linked to their transport modes and coupling with Na+ and H+. Most transporters share specificity for other neutral or cationic amino acids. Na+-dependent co-transporters efficiently accumulate glutamine while antiporters regulate the pools of glutamine and other amino acids. The most acknowledged glutamine transporters belong to the SLC1, 6, 7, and 38 families. The members involved in the homeostasis are the co-transporters B0AT1 and the SNAT members 1, 2, 3, 5, and 7; the antiporters ASCT2, LAT1 and 2. The last two are associated to the ancillary CD98 protein. Some information on regulation of the glutamine transporters exist, which, however, need to be deepened. No information at all is available on structures, besides some homology models obtained using similar bacterial transporters as templates. Some models of rat and human glutamine transporters highlight very similar structures between the orthologs. Moreover the presence of glycosylation and/or phosphorylation sites located at the extracellular or intracellular faces has been predicted. ASCT2 and LAT1 are over-expressed in several cancers, thus representing potential targets for pharmacological intervention.
Collapse
Affiliation(s)
- Lorena Pochini
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
| | - Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
| | - Michele Galluccio
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
| |
Collapse
|
9
|
Hassanein M, Hoeksema MD, Shiota M, Qian J, Harris BK, Chen H, Clark JE, Alborn WE, Eisenberg R, Massion PP. SLC1A5 mediates glutamine transport required for lung cancer cell growth and survival. Clin Cancer Res 2012; 19:560-70. [PMID: 23213057 DOI: 10.1158/1078-0432.ccr-12-2334] [Citation(s) in RCA: 246] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
PURPOSE We have previously identified solute-linked carrier family A1 member 5 (SLC1A5) as an overexpressed protein in a shotgun proteomic analysis of stage I non-small cell lung cancer (NSCLC) when compared with matched controls. We hypothesized that overexpression of SLC1A5 occurs to meet the metabolic demand for lung cancer cell growth and survival. EXPERIMENTAL DESIGN To test our hypothesis, we first analyzed the protein expression of SLC1A5 in archival lung cancer tissues by immunohistochemistry and immunoblotting (N = 98) and in cell lines (N = 36). To examine SLC1A5 involvement in amino acid transportation, we conducted kinetic analysis of l-glutamine (Gln) uptake in lung cancer cell lines in the presence and absence of a pharmacologic inhibitor of SLC1A5, gamma-l-Glutamyl-p-Nitroanilide (GPNA). Finally, we examined the effect of Gln deprivation and uptake inhibition on cell growth, cell-cycle progression, and growth signaling pathways of five lung cancer cell lines. RESULTS Our results show that (i) SLC1A5 protein is expressed in 95% of squamous cell carcinomas (SCC), 74% of adenocarcinomas (ADC), and 50% of neuroendocrine tumors; (ii) SLC1A5 is located at the cytoplasmic membrane and is significantly associated with SCC histology and male gender; (iii) 68% of Gln is transported in a Na(+)-dependent manner, 50% of which is attributed to SLC1A5 activity; and (iv) pharmacologic and genetic targeting of SLC1A5 decreased cell growth and viability in lung cancer cells, an effect mediated in part by mTOR signaling. CONCLUSIONS These results suggest that SLC1A5 plays a key role in Gln transport controlling lung cancer cells' metabolism, growth, and survival.
Collapse
Affiliation(s)
- Mohamed Hassanein
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Jim Ayers Institute of Precancer Detection and Diagnosis, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
OCHIAI H, ONDA K, OGIHARA K, NAYA Y, SUGIYAMA H, MARUO T. cDNA Sequence and Tissue Distribution of Canine Na-Dependent Neutral Amino Acid Transporter 2 (ASCT 2). J Vet Med Sci 2012; 74:1505-10. [DOI: 10.1292/jvms.12-0171] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Hideharu OCHIAI
- Research Institute of Biosciences, Azabu University, 1–17–71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252–5201, Japan
| | - Ken ONDA
- Laboratory of Internal Medicine 3, Azabu University, 1–17–71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252–5201, Japan
| | - Kikumi OGIHARA
- Laboratory of Pathology, Azabu University, 1–17–71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252–5201, Japan
| | - Yuko NAYA
- Laboratory of Pathology, Azabu University, 1–17–71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252–5201, Japan
| | - Hiroki SUGIYAMA
- Veterinary Teaching Hospital, Azabu University, 1–17–71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252–5201, Japan
| | - Takuya MARUO
- Veterinary Teaching Hospital, Azabu University, 1–17–71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252–5201, Japan
| |
Collapse
|
11
|
Bröer S. Amino acid transport across mammalian intestinal and renal epithelia. Physiol Rev 2008; 88:249-86. [PMID: 18195088 DOI: 10.1152/physrev.00018.2006] [Citation(s) in RCA: 614] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The transport of amino acids in kidney and intestine is critical for the supply of amino acids to all tissues and the homeostasis of plasma amino acid levels. This is illustrated by a number of inherited disorders affecting amino acid transport in epithelial cells, such as cystinuria, lysinuric protein intolerance, Hartnup disorder, iminoglycinuria, dicarboxylic aminoaciduria, and some other less well-described disturbances of amino acid transport. The identification of most epithelial amino acid transporters over the past 15 years allows the definition of these disorders at the molecular level and provides a clear picture of the functional cooperation between transporters in the apical and basolateral membranes of mammalian epithelial cells. Transport of amino acids across the apical membrane not only makes use of sodium-dependent symporters, but also uses the proton-motive force and the gradient of other amino acids to efficiently absorb amino acids from the lumen. In the basolateral membrane, antiporters cooperate with facilitators to release amino acids without depleting cells of valuable nutrients. With very few exceptions, individual amino acids are transported by more than one transporter, providing backup capacity for absorption in the case of mutational inactivation of a transport system.
Collapse
Affiliation(s)
- Stefan Bröer
- School of Biochemistry and Molecular Biology, Australian National University, Canberra, Australian Capital Territory, Australia.
| |
Collapse
|
12
|
Pinho MJ, Pinto V, Serrão MP, Jose PA, Soares-da-Silva P. Underexpression of the Na+-dependent neutral amino acid transporter ASCT2 in the spontaneously hypertensive rat kidney. Am J Physiol Regul Integr Comp Physiol 2007; 293:R538-47. [PMID: 17475673 DOI: 10.1152/ajpregu.00906.2006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
This study examined the inward transport of l-[14C]alanine, an ASCT2 preferential substrate, in monolayers of immortalized renal proximal tubular epithelial (PTE) cells from Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. The expression of ASCT2 in WKY and SHR PTE cells and kidney cortices from WKY and SHR was also evaluated. l-[14C]alanine uptake was highly dependent on extracellular Na+. Replacement of NaCl by LiCl or choline chloride abolished transport activity in SHR and WKY PTE cells. In the presence of the system L inhibitor BCH, Na+-dependent l-alanine uptake in WKY and SHR PTE cells was inhibited by alanine, serine, and cysteine, which is consistent with amino acid transport through ASCT2. The saturable component of Na+-dependent l-alanine transport under Vmax conditions in SHR PTE cells was one-half of that in WKY PTE cells, with similar Km values. Differences in magnitude of Na+-dependent l-alanine uptake through ASCT2 between WKY and SHR PTE cells correlated positively with differences in ASCT2 protein expression, this being more abundant in WKY PTE cells. Abundance of ASCT2 transcript and protein in kidney cortices of SHR rats was also lower than that in normotensive WKY rats. In conclusion, immortalized SHR and WKY PTE cells take up l-alanine mainly through a high-affinity Na+-dependent amino acid transporter, with functional features of ASCT2 transport. The activity and expression of the ASCT2 transporter were considerably lower in the SHR cells.
Collapse
Affiliation(s)
- Maria João Pinho
- Institute of Pharmacology and Therapeutics, Faculty of Medicine, 4200 Porto, Portugal
| | | | | | | | | |
Collapse
|
13
|
Huang Q, Li N, Zhu W, Li Q, Li J. Glutamine transporter ASCT2 was down-regulated in ischemic injured human intestinal epithelial cells and reversed by epidermal growth factor. JPEN J Parenter Enteral Nutr 2007; 31:86-93. [PMID: 17308248 DOI: 10.1177/014860710703100286] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Clinically, nutrition support has been an important component of the care of the hypoperfusion traumatized patient who is unable to accept complete volitional nutrition. However, enterocyte transport function during states of intestinal hypoperfusion remains unclear. Glutamine is essential for the viability and growth of intestine epithelial cells, and the Na(+)-dependent neutral amino acid transporter ASCT2 is thought to mainly mediate glutamine transport. This study aims to quantify the change of glutamine transporter ASCT2 expression in ischemic injured Caco-2 cell lines and the regulatory action of epidermal growth factor (EGF) on glutamine transport and its transporter. METHODS Cells were cultured under ischemic conditions for 2 hours. After ischemia was performed, Caco-2 cells were incubated with or without EGF (100 microg/mL) for 0-8 hours. Then we studied the cell membrane l-glutamine transport, the expression of ASCT2 protein, and mRNA. RESULTS After ischemia was performed, Caco-2 cell membrane glutamine transport decreased significantly (p < .01), and the expression of ASCT2 proteins decreased significantly compared with control (p < .01). Under ischemic conditions, expression of ASCT2 mRNA was down-regulated by a real-time polymerase chain reaction (PCR) method. After EGF incubation for 1-2 hours, the proteins and mRNA of ASCT2 were reversed to normal levels (p > .05). CONCLUSIONS In ischemic injured Caco-2 cells, ASCT2 protein expression and mRNA transcription were involved in the down-regulation of Na(+)-dependent glutamine transport. The decrease of glutamine transport and its transporter under ischemic conditions could be reversed by EGF action. These findings may help in the choice of the nutrition support manner and clinical therapy of ischemia-damaged intestinal epithelial cells.
Collapse
Affiliation(s)
- Qian Huang
- Research Institute of General Surgery, Jinling Hospital, Nanjing, China
| | | | | | | | | |
Collapse
|
14
|
Sundaram U, Wisel S, Coon S. Neutral Na-amino acid cotransport is differentially regulated by glucocorticoids in the normal and chronically inflamed rabbit small intestine. Am J Physiol Gastrointest Liver Physiol 2007; 292:G467-74. [PMID: 17290012 DOI: 10.1152/ajpgi.00503.2005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Neutral Na-amino acid cotransport by system ATB(0) [e.g., Na-alanine cotransport (NAcT)] is an important means of assimilation of amino acids in the intestine. NAcT is inhibited during chronic intestinal inflammation by an alteration in the affinity for the amino acid. How glucocorticoids, a standard of treatment for diseases characterized by chronic intestinal inflammation, may affect NAcT during chronic enteritis is not known. Thus we first demonstrated that methylprednisolone (MP) stimulated NAcT in the normal intestine. The mechanism of stimulation was secondary to an increase in cotransporter numbers without an alteration in the affinity for the amino acid. Treatment with MP reversed the reduction in NAcT in villus cells from the chronically inflamed intestine. MP also alleviated the decrease in Na-K-ATPase activity in villus cells during chronic enteritis. However, MP treatment reversed the NAcT inhibition in villus cell brush border membrane vesicles from the inflamed intestine, which suggested an effect of MP at the level of the cotransporter itself. Kinetic studies demonstrated that the reversal of NAcT inhibition by MP was secondary to restoration in the affinity for the amino acid without a change in the V(max). Unaltered steady-state mRNA and immunoreactive protein levels of NAcT also indicated that the number of cotransporters was unchanged after MP treatment in the chronically inflamed intestine. These results indicated that MP reversed NAcT inhibition in the chronically inflamed intestine by restoring the affinity of the transporter for the amino acid while it stimulated NAcT in the normal intestine by increasing the cotransporter numbers. Therefore, MP differentially regulates NAcT in the normal and chronically inflamed intestine.
Collapse
Affiliation(s)
- Uma Sundaram
- Section of Digestive Diseases, Dept of Medicine, West Virginia Univ School of Medicine, Morgantown, WV 26506, USA.
| | | | | |
Collapse
|
15
|
Palacín M, Nunes V, Font-Llitjós M, Jiménez-Vidal M, Fort J, Gasol E, Pineda M, Feliubadaló L, Chillarón J, Zorzano A. The Genetics of Heteromeric Amino Acid Transporters. Physiology (Bethesda) 2005; 20:112-24. [PMID: 15772300 DOI: 10.1152/physiol.00051.2004] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Heteromeric amino acid transporters (HATs) are composed of a heavy ( SLC3 family) and a light ( SLC7 family) subunit. Mutations in system b0,+(rBAT-b0,+AT) and in system y+L (4F2hc-y+LAT1) cause the primary inherited aminoacidurias (PIAs) cystinuria and lysinuric protein intolerance, respectively. Recent developments [including the identification of the first Hartnup disorder gene (B0AT1; SLC6A19)] and knockout mouse models have begun to reveal the basis of renal and intestinal reabsorption of amino acids in mammals.
Collapse
Affiliation(s)
- Manuel Palacín
- Department of Biochemistry and Molecular Biology, Faculty of Biology and Institut de Recerca Biomedica de Barcelona, Barcelona Science Park, University of Barcelona, Spain.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Bungard CI, McGivan JD. Glutamine availability up-regulates expression of the amino acid transporter protein ASCT2 in HepG2 cells and stimulates the ASCT2 promoter. Biochem J 2005; 382:27-32. [PMID: 15175006 PMCID: PMC1133911 DOI: 10.1042/bj20040487] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2004] [Revised: 05/25/2004] [Accepted: 06/03/2004] [Indexed: 01/19/2023]
Abstract
Glutamine transport into the human hepatoma cell line HepG2 is catalysed primarily by an ASCT2-type transporter identical in sequence with that cloned previously from JAR cells. An antibody raised against the C-terminus of the ASCT2 protein was shown to recognize ASCT2 on Western blots. Using this antibody, it was found that variation in cell growth rate did not affect ASCT2 expression, but both growth rate and ASCT2 expression were significantly reduced by glutamine deprivation. Expression of a number of other proteins was shown to be unaffected under these conditions. The sequence of the 5'-flanking region of the ASCT2 gene was derived from the human genome database. A 907 bp fragment of this sequence was directionally ligated into a luciferase reporter vector and was shown to exhibit promoter activity when transfected into HepG2 cells. Promoter activity was greatly reduced when transfection was performed in glutamine-free medium and was restored when glutamine was added post-transfection. The absence of other essential amino acids did not affect promoter activity, and glutamine deprivation did not affect the MCT1 (monocarboxylate transporter 1) promoter. These results indicate that both ASCT2 promoter activity and ASCT2 protein expression in these cells are dependent on glutamine availability.
Collapse
Affiliation(s)
- Claire I Bungard
- Department of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK.
| | | |
Collapse
|
17
|
Fan MZ, Matthews JC, Etienne NMP, Stoll B, Lackeyram D, Burrin DG. Expression of apical membrane L-glutamate transporters in neonatal porcine epithelial cells along the small intestinal crypt-villus axis. Am J Physiol Gastrointest Liver Physiol 2004; 287:G385-98. [PMID: 15044176 DOI: 10.1152/ajpgi.00232.2003] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Enteral l-glutamate is extensively utilized as an oxidative fuel by the gut mucosa in the neonate. To identify major uptake pathways and to understand uptake regulation, we examined transport kinetics and molecular identities of apical membrane l-glutamate transporters in epithelial cells sequentially isolated along the small intestinal crypt-villus axis from milk protein-fed, 16-day-old pigs. The distended intestinal sac method was used to isolate 12 sequential cell fractions from the tip villus to the bottom crypt. Initial rates and kinetics of l-glutamate uptake were measured with l-[G-(3)H]glutamate by fast filtration in apical membrane vesicles prepared by Mg(2+) precipitation and differential centrifugation, with membrane potential clamped by SCN(-). Initial l-glutamate uptake results suggested the presence of B(o) and X(AG)(-) transport systems, but the X(AG)(-) system was predominant for uptake across the apical membrane. Kinetic data suggested that l-glutamate uptake through the X(AG)(-) system was associated with higher maximal transport activity but lower transporter affinity in crypt than in villus cells. Molecular identity of the X(AG)(-) glutamate transporter, based on immunoblot and RT-PCR analysis, was primarily the defined excitatory amino acid carrier (EAAC)-1. EAAC-1 expression was increased with cell differentiation and regulated at transcription and translation levels from crypt to upper villus cells. In conclusion, efficiency and capacity of luminal l-glutamate uptake across the apical membrane are regulated by changing expression of the X(AG)(-) system transporter gene EAAC-1 at transcription and translation levels as well as maximal uptake activity and transporter affinity along the intestinal crypt-villus axis in the neonate.
Collapse
Affiliation(s)
- Ming Z Fan
- USDA/ARS Children's Nutrition Research Center, Dept. of Pediatrics, Baylor College of Medicine, 1100 Bates St., Houston, TX 77030, USA
| | | | | | | | | | | |
Collapse
|
18
|
Chen Z, Fei YJ, Anderson CMH, Wake KA, Miyauchi S, Huang W, Thwaites DT, Ganapathy V. Structure, function and immunolocalization of a proton-coupled amino acid transporter (hPAT1) in the human intestinal cell line Caco-2. J Physiol 2003; 546:349-61. [PMID: 12527723 PMCID: PMC2342508 DOI: 10.1113/jphysiol.2002.026500] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The human orthologue of the H(+)-coupled amino acid transporter (hPAT1) was cloned from the human intestinal cell line Caco-2 and its functional characteristics evaluated in a mammalian cell heterologous expression system. The cloned hPAT1 consists of 476 amino acids and exhibits 85 % identity with rat PAT1. Among the various human tissues examined by Northern blot, PAT1 mRNA was expressed most predominantly in the intestinal tract. When expressed heterologously in mammalian cells, hPAT1 mediated the transport of alpha-(methylamino)isobutyric acid (MeAIB). The cDNA-induced transport was Na(+)-independent, but was energized by an inwardly directed H(+) gradient. hPAT1 interacted with glycine, L-alanine, L-proline, alpha-aminoisobutyrate (AIB) and gamma-aminobutyrate (GABA), as evidenced from direct transport measurements and from competition experiments with MeAIB as a transport substrate. hPAT1 also recognized the D-isomers of alanine and proline. With serine and cysteine, though the L-isomers did not interact with hPAT1 to any significant extent, the corresponding D-isomers were recognized as substrates. With proline and alanine, the affinity was similar for L- and D-isomers. However, with cysteine and serine, the D-isomers showed 6- to 8-fold higher affinity for hPAT1 than the corresponding L-isomers. These functional characteristics of hPAT1 closely resemble those that have been described previously for the H(+)-coupled amino acid transport system in Caco-2 cells. Furthermore, there was a high degree of correlation (r(2) = 0.93) between the relative potencies of various amino acids to inhibit the H(+)-coupled MeAIB transport measured with native Caco-2 cells and with hPAT1 in the heterologous expression system. Immunolocalization studies showed that PAT1 was expressed exclusively in the apical membrane of Caco-2 cells. These data suggest that hPAT1 is responsible for the H(+)-coupled amino acid transport expressed in the apical membrane of Caco-2 cells.
Collapse
Affiliation(s)
- Zhong Chen
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA
| | | | | | | | | | | | | | | |
Collapse
|
19
|
Kles KA, Tappenden KA. Hypoxia differentially regulates nutrient transport in rat jejunum regardless of luminal nutrient present. Am J Physiol Gastrointest Liver Physiol 2002; 283:G1336-42. [PMID: 12388198 DOI: 10.1152/ajpgi.00055.2002] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Aggressive enteral nutrition and poor intestinal perfusion are hypothesized to play an important pathogenic role in nonocclusive small bowel necrosis. This study tests the hypothesis that glucose and glutamine transport are differentially regulated during hypoxia regardless of the luminal nutrient present. Sprague-Dawley rats (247 +/- 3 g; n = 16) were randomized to receive 1 h of intestinal hypoxia or serve as normoxic controls. During this hour, jejunal loops were randomized to receive in situ perfusions of mannitol, glucose, or glutamine. When compared with normoxic groups, glucose but not glutamine transport was impaired (P < 0.001) during hypoxia. Messenger RNA abundance of the sodium glucose cotransporter sodium-dependent glucose cotransporter-1 (SGLT-1) and neutral basic amino acid transporter B(o) did not differ with hypoxia or nutrient perfused. Jejunal brush-border SGLT-1 abundance was decreased (P = 0.039) with hypoxia; however, total cellular SGLT-1 protein abundance did not differ among treatment groups. These data indicate that SGLT-1 activity is regulated during hypoxia at the posttranslational level. Additional information regarding the mechanisms regulating nutrient transport in the hypoperfused intestine is critical for optimizing the composition of enteral nutrient formulas.
Collapse
Affiliation(s)
- K A Kles
- Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | | |
Collapse
|
20
|
Pollard M, Meredith D, McGivan JD. Identification of a plasma membrane glutamine transporter from the rat hepatoma cell line H4-IIE-C3. Biochem J 2002; 368:371-5. [PMID: 12171599 PMCID: PMC1222977 DOI: 10.1042/bj20020982] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2002] [Revised: 07/29/2002] [Accepted: 08/12/2002] [Indexed: 11/17/2022]
Abstract
Glutamine is taken up into the rat hepatoma cell line H4-IIE-C3 by a Na+-dependent transport system which is specific for glutamine, alanine, serine, cysteine and asparagine and does not tolerate substitution of Na+ by Li+. Glutamine transport was relatively weakly inhibited by a 50-fold excess of leucine and was not inhibited by phenylalanine or N -methyl aminoisobutyrate. These general properties are characteristic of the recently identified ASCT/B0 family of transporters. Using a reverse transcriptase PCR-based homology cloning approach, we have characterized a cDNA for a novel member of this transporter family (H4-ASCT2) from H4-IIE-C3 cells. The cDNA encodes a 551-amino acid protein which exhibits similarities of between 75 and 85% with ASCT/B0 transporters previously cloned from other sources. When expressed in Xenopus oocytes, this transporter catalyses Na+-dependent glutamine uptake with characteristics very similar to those of glutamine uptake into the H4-IIE-C3 cells. This newly characterized transporter possesses a number of amino acid sequence differences from ASCT2 clones recently isolated from rat astroglial cells and from normal rat liver. In particular, the loop region between transmembrane helices 3 and 4 from H4-ASCT2 shares less than 60% sequence similarity with ASCT2 from rat liver; furthermore, there are some 25 single amino acid substitutions elsewhere in the H4-ASCT2 sequence compared with that from rat liver. Thus enhanced glutamine uptake in rat hepatoma cells is mediated by the expression of a novel ASCT/B0 transporter isoform rather than by increased expression of the ASCT2 mRNA found in normal rat liver.
Collapse
Affiliation(s)
- Matthew Pollard
- Department of Biochemistry, School of Medical Sciences, University Walk, Bristol BS8 1TD, U.K
| | | | | |
Collapse
|
21
|
Bode BP, Fuchs BC, Hurley BP, Conroy JL, Suetterlin JE, Tanabe KK, Rhoads DB, Abcouwer SF, Souba WW. Molecular and functional analysis of glutamine uptake in human hepatoma and liver-derived cells. Am J Physiol Gastrointest Liver Physiol 2002; 283:G1062-73. [PMID: 12381519 DOI: 10.1152/ajpgi.00031.2002] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Human hepatoma cells take up glutamine at rates severalfold faster than the system N-mediated transport rates observed in normal human hepatocytes. Amino acid inhibition, kinetic, Northern blotting, RT-PCR, and restriction enzyme analyses collectively identified the transporter responsible in six human hepatoma cell lines as amino acid transporter B(0) (ATB(0)), the human ortholog of rodent ASCT2. The majority of glutamine uptake in liver fibroblasts and an immortalized human liver epithelial cell line (THLE-5B) was also mediated by ATB(0). The 2.9-kb ATB(0) mRNA was equally expressed in all cell lines, whereas expression of the system A transporters ATA2 and ATA3 was variable. In contrast, the system N isoforms (SN1 and SN2) were expressed only in well-differentiated hepatomas. ATB(0) mRNA was also expressed in cirrhotic liver and adult and pediatric liver cancer biopsies but was not detectable in isolated human hepatocytes or fetal liver. Although the growth of all hepatomas was glutamine dependent, competitive inhibition of ATB(0)-mediated glutamine uptake blocked proliferation only in poorly differentiated cells lacking SN1 or SN2 expression and exhibiting low glutamine synthetase mRNA levels.
Collapse
Affiliation(s)
- Barrie P Bode
- Surgical Oncology Research Laboratories, Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
22
|
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.
Collapse
Affiliation(s)
- Masafumi Wasa
- Department of Pediatric Surgery, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
| | | | | |
Collapse
|
23
|
Avissar NE, Ryan CK, Ganapathy V, Sax HC. Na(+)-dependent neutral amino acid transporter ATB(0) is a rabbit epithelial cell brush-border protein. Am J Physiol Cell Physiol 2001; 281:C963-71. [PMID: 11502573 DOI: 10.1152/ajpcell.2001.281.3.c963] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
System B(0) activity accounts for the majority of intestinal and kidney luminal neutral amino acid absorption. An amino acid transport system, called ATB(0) (also known as ASCT2), with functional characteristics similar to those of system B(0), has been recently cloned. We generated polyclonal antibodies to human and rabbit ATB(0) COOH-terminal peptides and used Western blot analysis to detect ATB(0) protein in rabbit tissues, rabbit ileal brush-border membrane vesicles (BBMV), and HeLa cells transfected with plasmids containing ATB(0) cDNAs. Immunohistochemistry was used to localize ATB(0) in rabbit kidney and intestine. In Western blots of rabbit tissues, ATB(0) was a broad smear of 78- to 85-kDa proteins. In transfected HeLa cells, ATB(0) appeared as a smear consisting of 57- to 65-kDa proteins. The highest expression was found in the kidney. ATB(0) was enriched in rabbit ileal BBMV and in HeLa cells transfected with ATB(0) cDNAs. In the kidney and in the intestine, ATB(0) was confined to the brush-border membrane (BBM) of the proximal tubular cell and of the enterocyte, respectively. Tissue and intracellular distribution of ATB(0) protein parallels that of system B(0) activity. ATB(0) protein could be the transporter responsible for system B(0) in the BBM of epithelial cells.
Collapse
Affiliation(s)
- N E Avissar
- Department of Surgery, University of Rochester Medical Center, Rochester, New York 14642, USA.
| | | | | | | |
Collapse
|
24
|
Riemann B, Kopka K, Stögbauer F, Halfter H, Ketteler S, Phan TQ, Franzius C, Weckesser M, Ringelstein EB, Schober O. Kinetic parameters of 3-[(123)I]iodo-L-alpha-methyl tyrosine ([(123)I]IMT) transport in human GOS3 glioma cells. Nucl Med Biol 2001; 28:293-7. [PMID: 11323240 DOI: 10.1016/s0969-8051(01)00191-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The radiolabelled amino acid 3-[(123)I]iodo-L-alpha-methyl tyrosine ([(123)I]IMT) is a promising tool for the diagnosis and monitoring of brain tumors using single-photon emission tomography (SPECT). However, little is known about the precise kinetics of [(123)I]IMT uptake in human glioma cells. The kinetic analysis of [(123)I]IMT transport in human GOS3 glioma cells yielded a high-affinity apparent Michaelis constant (K(m) = 20.1 +/- 1.5 microM). The maximum transport velocity (V(max)) amounted to 34.8 +/- 1.9 nmol/mg protein/10 min. Competitive inhibition experiments revealed that [(123)I]IMT transport is mediated principally by the sodium-independent system L.
Collapse
Affiliation(s)
- B Riemann
- Department of Nuclear MedicineWestfälische Wilhelms-Universität, Münster, Germany.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Increased translation efficiency and antizyme-dependent stabilization of ornithine decarboxylase in amino acid-supplemented human colon adenocarcinoma cells, Caco-2. Biochem J 2000. [PMID: 10816435 DOI: 10.1042/bj3480401] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The mechanisms of the response of ornithine decarboxylase(ODC), the rate-limiting enzyme in polyamine biosynthesis, to amino acid supplementation were studied in the human colon adenocarcinoma cell line, Caco-2. Supplementation of serum-deprived, subconfluent Caco-2 cells with any one of a series of amino acids (10 mM) resultedin increased ODC activity, reaching a maximum of approx. 12.5-fold after approx. 4 h, over control cells either not supplemented or supplemented with iso-osmolar D-mannitol. Glycine, L-asparagine and L-serine, as well as their D-enantiomers, were the strongest effectors and acted in a concentration-dependent manner; millimolar concentrations of most of these amino acids being sufficient to significantly increase ODC activity. In contrast, supplementation with D-methionine, L-lysine, L-aspartate or L-glutamate had little or no effect on ODC activity, whereas supplemental L-methionine, L-arginine, L-ornithine or L-cysteine was inhibitory. Polyamine assays showed that the putrescine content of cells varied in accordance with the changes in ODC activity. Western-blot and Northern-blot analyses revealed specifically increased levels of ODC protein but not mRNA,respectively, in response to supplementation with an ODC-inducing amino acid. Suppression of the increase in cycloheximide-treated cellsconfirmed a requirement for protein synthesis. Pulse-labelling of cellswith [(35)S]methionine showed a 3-fold increase in thesynthesis of ODC protein after 4 h of supplementation with glycineor L-serine. Supplemental glycine also augmented, reversibly, the half-life of ODC by almost 4-fold and simultaneously decreased the activity of putrescine-induced free antizyme. These results suggest that translational, but not transcriptional, regulation of ODC takes part in ODC induction by amino acids in Caco-2 cells. However, it also appears to occur in concert with decreased enzyme in activation and/or degradation.
Collapse
|
26
|
Díez-Sampedro A, Lostao MP, Barber A. Cytoskeleton involvement on intestinal absorption processes. J Physiol Biochem 2000; 56:25-32. [PMID: 10879678 DOI: 10.1007/bf03179773] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
It has been recently demonstrated in the laboratory that the cytoskeletal inhibitor cytochalasin E has an indirect inhibitory effect on the function of the intestinal Na+-sugar cotransporter (SGLT1). The present work confirms that cytochalasin E inhibits SGLT1 activity through cytoskeleton disruption, showing that in anaerobic conditions (N2 bubbling), which implies low cytosolic ATP levels, the inhibition is not observed. As it occurs in sugar transport, the Na+-dependent intestinal transport of phenylalanine decreases if cytochalasin E is present in the incubation medium. However, the activity of the brush border enzymes sucrase, amino peptidase N and gamma-glutamyl transferase is not affected by the inhibitor. These enzymes only have one transmembrane domain and the active center is projected to the intestinal lumen. Therefore, cytoskeleton changes that could modify the transmembrane enzyme segment do not alter the activity of these enzymes. Examination of the intestine morphology after 30 min incubation with cytochalasin E shows only light modifications which do not seem to explain the inhibitory effects of the toxin on Na+-sugar or Na+-phenylalanine cotransporters function. On the whole, these results indicate that the inhibition of cytochalasin E on galactose and phenylalanine intestinal transport is secondary to its action on cytoskeleton through protein structure modifications.
Collapse
Affiliation(s)
- A Díez-Sampedro
- Dpto Fisiología y Nutrición, Universidad de Navarra, Pamplona, Spain
| | | | | |
Collapse
|
27
|
Rasko JE, Battini JL, Gottschalk RJ, Mazo I, Miller AD. The RD114/simian type D retrovirus receptor is a neutral amino acid transporter. Proc Natl Acad Sci U S A 1999; 96:2129-34. [PMID: 10051606 PMCID: PMC26748 DOI: 10.1073/pnas.96.5.2129] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The RD114/simian type D retroviruses, which include the feline endogenous retrovirus RD114, all strains of simian immunosuppressive type D retroviruses, the avian reticuloendotheliosis group including spleen necrosis virus, and baboon endogenous virus, use a common cell-surface receptor for cell entry. We have used a retroviral cDNA library approach, involving transfer and expression of cDNAs from highly infectable HeLa cells to nonpermissive NIH 3T3 mouse cells, to clone and identify this receptor. The cloned cDNA, denoted RDR, is an allele of the previously cloned neutral amino acid transporter ATB0 (SLC1A5). Both RDR and ATB0 serve as retrovirus receptors and both show specific transport of neutral amino acids. We have localized the receptor by radiation hybrid mapping to a region of about 500-kb pairs on the long arm of human chromosome 19 at q13.3. Infection of cells with RD114/type D retroviruses results in impaired amino acid transport, suggesting a mechanism for virus toxicity and immunosuppression. The identification and functional characterization of this retrovirus receptor provide insight into the retrovirus life cycle and pathogenesis and will be an important tool for optimization of gene therapy using vectors derived from RD114/type D retroviruses.
Collapse
Affiliation(s)
- J E Rasko
- Division of Molecular Medicine, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA
| | | | | | | | | |
Collapse
|
28
|
Fan MZ, Adeola O, McBurney MI, Cheeseman CI. Kinetic analysis of L-glutamine transport into porcine jejunal enterocyte brush-border membrane vesicles. Comp Biochem Physiol A Mol Integr Physiol 1998; 121:411-22. [PMID: 10048191 DOI: 10.1016/s1095-6433(98)10152-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
L-Glutamine transport into porcine jejunal enterocyte brush border membrane vesicles was studied. Uptake was mediated by a Na(+)-dependent and a Na(+)-independent pathway as well as by diffusion. The initial rates of glutamine uptake over a range of concentrations is both Na(+)-gradient and Na(+)-free conditions were analyzed and kinetic parameters were obtained. Na(+)-dependent glutamine transport had a K(m) of 0.77 +/- 0.16 mM and a Jmax of 70.7 +/- 5.8 pmol mg protein-1 s-1; Na(+)-independent glutamine transport had a K(m) of 3.55 +/- 0.78 mM and a Jmax of 55.1 +/- 6.6 pmol mg protein-1 s-1. The non-saturable component measured with HgCl2-poisoned brush border membrane vesicles in the Na(+)-free condition contained passive diffusion and non-specific membrane binding and was defined to be apparent glutamine diffusion and the glutamine permeability coefficient (Kdiff) was estimated to be Kdiff = 3.78 +/- 0.06 pmol 1 mg protein-1 mmol-1 s-1. Results of inhibition experiments showed that Na(+)-dependent glutamine uptake occurred primarily through the brush border system-B degree transporters, whereas Na(+)-independent glutamine uptake occurred via the system-L transporters. Furthermore, the kinetics of L-leucine and L-cysteine inhibition of L-glutamine uptake demonstrated that neutral amino acids sharing the same brush border transporters can effectively inhibit each other in their transport.
Collapse
Affiliation(s)
- M Z Fan
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA
| | | | | | | |
Collapse
|