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Mora S, Adegoke OAJ. Maintenance of the branched-chain amino acid transporter LAT1 counteracts myotube atrophy following chemotherapy. Am J Physiol Cell Physiol 2024; 326:C866-C879. [PMID: 38284122 DOI: 10.1152/ajpcell.00537.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 01/14/2024] [Accepted: 01/18/2024] [Indexed: 01/30/2024]
Abstract
Prevention/management of cachexia remains a critical issue in muscle wasting conditions. The branched-chain amino acids (BCAA) have anabolic properties in skeletal muscle, but their use in treating cachexia has minimal benefits. This may be related to altered BCAA metabolism consequent to the use of chemotherapy, a main cancer treatment. Since this topic is minimally studied, we investigated the effect of chemotherapy on BCAA concentrations, transporter expression, and their metabolism. L6 myotubes were treated with vehicle (1.4 μL/mL DMSO) or a chemotherapy drug cocktail, FOLFIRI [CPT-11 (20 μg/mL), leucovorin (10 μg/mL), and 5-fluorouracil (50 μg/mL)] for 24-48 h. Chemotherapy reduced myotube diameter (-43%), myofibrillar protein content (-50%), and phosphorylation of the mechanistic target of rapamycin complex 1 (mTORC1) substrate S6K1thr389 (-80%). Drug-treated myotubes exhibited decreased BCAA concentrations (-52%) and expression of their transporter, L-type amino acid transporter 1 (LAT1; -67%). BCAA transaminase BCAT2 level was increased, but there was a reduction in PP2CM (-54%), along with increased inhibitory phosphorylation of BCKD-E1αser293 (+98%), corresponding with decreased BCKD enzyme activity (-23%) in chemotherapy-treated myotubes. Decreases in BCAA concentrations were a later response, preceded by decreases in LAT1 and BCKD activity. Although supplementation with the BCAA restored myotube BCAA levels, it had minimal effects on preventing the loss of myofibrillar proteins. However, RNAi-mediated depletion of neural precursor cell-expressed developmentally downregulated gene 4 (NEdd4), the protein ligase responsible for ubiquitin-dependent degradation of LAT1, attenuated the effects of chemotherapy on BCAA concentrations, anabolic signaling, protein synthesis, and myofibrillar protein abundance. Thus, if our findings are validated in preclinical models, interventions regulating muscle amino acid transporters might represent a promising strategy to treat cachexia.NEW & NOTEWORTHY This is the first study to attenuate chemotherapy-induced myotube atrophy by manipulating a BCAA transporter. Our findings suggest that positive regulation of amino acid transporters may be a promising strategy to treat cachexia.
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Affiliation(s)
- Stephen Mora
- School of Kinesiology and Health Science and Muscle Health Research Centre, York University, Toronto, Ontario, Canada
| | - Olasunkanmi A J Adegoke
- School of Kinesiology and Health Science and Muscle Health Research Centre, York University, Toronto, Ontario, Canada
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Barroso E, Díaz M, Reguera AC, Peyman M, Balsinde J, Jurado-Aguilar J, Zhang M, Rostami A, Palomer X, Ibáñez L, Vázquez-Carrera M. CHOP upregulation and dysregulation of the mature form of the SNAT2 amino acid transporter in the placentas from small for gestational age newborns. Cell Commun Signal 2023; 21:326. [PMID: 37957724 PMCID: PMC10644500 DOI: 10.1186/s12964-023-01352-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 10/10/2023] [Indexed: 11/15/2023] Open
Abstract
BACKGROUND The placentas from newborns that are small for gestational age (SGA; birth weight < -2 SD for gestational age) may display multiple pathological characteristics. A key determinant of fetal growth and, therefore, birth weight is placental amino acid transport, which is under the control of the serine/threonine kinase mechanistic target of rapamycin (mTOR). The effects of endoplasmic reticulum (ER) stress on the mTOR pathway and the levels of amino acid transporters are not well established. METHODS Placentas from SGA and appropriate for gestational age (AGA) newborns and the human placental BeWo cell line exposed to the ER stressor tunicamycin were used. RESULTS We detected a significant increase in the levels of C/EBP homologous protein (CHOP) in the placentas from SGA newborns compared with those from AGA newborns, while the levels of other ER stress markers were barely affected. In addition, placental mTOR Complex 1 (mTORC1) activity and the levels of the mature form of the amino acid transporter sodium-coupled neutral amino acid transporter 2 (SNAT2) were also reduced in the SGA group. Interestingly, CHOP has been reported to upregulate growth arrest and DNA damage-inducible protein 34 (GADD34), which in turn suppresses mTORC1 activity. The GADD34 inhibitor guanabenz attenuated the increase in CHOP protein levels and the reduction in mTORC1 activity caused by the ER stressor tunicamycin in the human placental cell line BeWo, but it did not recover mature SNAT2 protein levels, which might be reduced as a result of defective glycosylation. CONCLUSIONS Collectively, these data reveal that GADD34A activity and glycosylation are key factors controlling mTORC1 signaling and mature SNAT2 levels in trophoblasts, respectively, and might contribute to the SGA condition. Video Abstract.
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Affiliation(s)
- Emma Barroso
- Unitat de Farmacologia, Facultat de Farmàcia I Ciències de L'Alimentació, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Av. Joan XXIII 27-31, 08028, Barcelona, Spain
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain
- Pediatric Research Institute-Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain
| | - Marta Díaz
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain
- Pediatric Research Institute-Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain
- Endocrinology, Pediatric Research Institute, Sant Joan de Déu Children's Hospital, Barcelona, Esplugues, Spain
| | - Ana Cristina Reguera
- Unitat de Farmacologia, Facultat de Farmàcia I Ciències de L'Alimentació, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Av. Joan XXIII 27-31, 08028, Barcelona, Spain
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain
- Pediatric Research Institute-Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain
| | - Mona Peyman
- Unitat de Farmacologia, Facultat de Farmàcia I Ciències de L'Alimentació, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Av. Joan XXIII 27-31, 08028, Barcelona, Spain
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain
- Pediatric Research Institute-Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain
| | - Jesús Balsinde
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Valladolid, Spain
| | - Javier Jurado-Aguilar
- Unitat de Farmacologia, Facultat de Farmàcia I Ciències de L'Alimentació, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Av. Joan XXIII 27-31, 08028, Barcelona, Spain
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain
- Pediatric Research Institute-Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain
| | - Meijian Zhang
- Unitat de Farmacologia, Facultat de Farmàcia I Ciències de L'Alimentació, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Av. Joan XXIII 27-31, 08028, Barcelona, Spain
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain
- Pediatric Research Institute-Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain
| | - Adel Rostami
- Unitat de Farmacologia, Facultat de Farmàcia I Ciències de L'Alimentació, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Av. Joan XXIII 27-31, 08028, Barcelona, Spain
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain
- Pediatric Research Institute-Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain
| | - Xavier Palomer
- Unitat de Farmacologia, Facultat de Farmàcia I Ciències de L'Alimentació, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Av. Joan XXIII 27-31, 08028, Barcelona, Spain
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain
- Pediatric Research Institute-Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain
| | - Lourdes Ibáñez
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain
- Pediatric Research Institute-Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain
- Endocrinology, Pediatric Research Institute, Sant Joan de Déu Children's Hospital, Barcelona, Esplugues, Spain
| | - Manuel Vázquez-Carrera
- Unitat de Farmacologia, Facultat de Farmàcia I Ciències de L'Alimentació, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Av. Joan XXIII 27-31, 08028, Barcelona, Spain.
- Spanish Biomedical Research Center in Diabetes and Associated Metabolic Diseases (CIBERDEM)-Instituto de Salud Carlos III, Madrid, Spain.
- Pediatric Research Institute-Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain.
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Liang Z, Jin C, Bai H, Liang G, Su X, Wang D, Yao J. Low rumen degradable starch promotes the growth performance of goats by increasing protein synthesis in skeletal muscle via the AMPK-mTOR pathway. Anim Nutr 2023; 13:1-8. [PMID: 36873600 PMCID: PMC9981809 DOI: 10.1016/j.aninu.2022.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 09/22/2022] [Accepted: 10/04/2022] [Indexed: 11/18/2022]
Abstract
Since starch digestion in the small intestine provides more energy than digestion in the rumen of ruminants, reducing dietary rumen degradable starch (RDS) content is beneficial for improving energy utilization of starch in ruminants. The present study tested whether the reduction of rumen degradable starch by restricting dietary corn processing for growing goats could improve growth performance, and further investigated the possible underlying mechanism. In this study, twenty-four 12-wk-old goats were selected and randomly allocated to receive either a high RDS diet (HRDS, crushed corn-based concentrate, the mean of particle sizes of corn grain = 1.64 mm, n = 12) or a low RDS diet (LRDS, non-processed corn-based concentrate, the mean of particle sizes of corn grain >8 mm, n = 12). Growth performance, carcass traits, plasma biochemical indices, gene expression of glucose and amino acid transporters, and protein expression of the AMPK-mTOR pathway were measured. Compared to the HRDS, LRDS tended to increase the average daily gain (ADG, P = 0.054) and decreased the feed-to-gain ratio (F/G, P < 0.05). Furthermore, LRDS increased the net lean tissue rate (P < 0.01), protein content (P < 0.05) and total free amino acids (P < 0.05) in the biceps femoris (BF) muscle of goats. LRDS increased the glucose concentration (P < 0.01), but reduced total amino acid concentration (P < 0.05) and tended to reduce blood urea nitrogen (BUN) concentration (P = 0.062) in plasma of goats. The mRNA expression of insulin receptors (INSR), glucose transporter 4 (GLUT4), L-type amino acid transporter 1 (LAT1) and 4F2 heavy chain (4F2hc) in BF muscle, and sodium-glucose cotransporters 1 (SGLT1) and glucose transporter 2 (GLUT2) in the small intestine were significantly increased (P < 0.05) in LRDS goats. LRDS also led to marked activation of p70-S6 kinase (S6K) (P < 0.05), but lower activation of AMP-activated protein kinase (AMPK) (P < 0.05) and eukaryotic initiation factor 2α (P < 0.01). Our findings suggested that reducing the content of dietary RDS enhanced postruminal starch digestion and increased plasma glucose, thereby improving amino acid utilization and promoting protein synthesis in the skeletal muscle of goats via the AMPK-mTOR pathway. These changes may contribute to improvement in growth performance and carcass traits in LRDS goats.
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Affiliation(s)
- Ziqi Liang
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Chunjia Jin
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Hanxun Bai
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Gaofeng Liang
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Xiaodong Su
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Dangdang Wang
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Junhu Yao
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China
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Shao Y, Luo J, Ye L, Ran HY, Shi HM, Zhang C, Wu QC. Construction and Integrated Analysis of Competitive Endogenous Long Non-Coding RNA Network in Thoracic Aortic Dissection. Int J Gen Med 2021; 14:6863-6873. [PMID: 34703291 PMCID: PMC8528547 DOI: 10.2147/ijgm.s335082] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 09/29/2021] [Indexed: 12/12/2022] Open
Abstract
Background Long non-coding RNAs (lncRNAs) can act as a competitive endogenous RNA (ceRNA) to regulate gene expression by sequestering the microRNA (miRNA). However, the lncRNA-miRNA-mRNA ceRNA network in thoracic aortic dissection (TAD) has been rarely documented. Methods Three Gene Expression Omnibus (GEO) datasets were used to detect differentially expressed mRNAs, miRNAs, and lncRNAs in TAD. Gene ontology and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were conducted for the differentially expressed mRNAs. A protein–protein interaction network for differentially expressed mRNAs was also constructed, and hub genes were identified. We established a ceRNA network of TAD based on the differentially expressed miRNAs, mRNAs and lncRNAs, and verified our results using an independent dataset and quantitative real-time PCR (qRT-PCR). Results In TAD, 267 lncRNAs, 81 miRNAs, and 346 mRNAs were identified as differentially expressed. The established ceRNA network consisted of seven lncRNA nodes, three mRNA nodes, and three miRNA nodes, and the expression of miRNAs in TAD was opposite to that of lncRNAs and mRNAs. Subsequently, an independent GEO dataset and qRT-PCR were used to validate the expression of three mRNAs. In addition, the expression differences in SLC7A5, associated miRNA and lncRNA were verified. According to gene set enrichment analysis of SLC7A5, the most significant KEGG pathway was considerably enriched in spliceosome and pentose phosphate pathway. Conclusion We established a novel ceRNA regulatory network in TAD, which provides valuable information for further research in the molecular mechanisms of TAD.
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Affiliation(s)
- Yue Shao
- Department of Cardiothoracic Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, People's Republic of China
| | - Jun Luo
- Department of Cardiothoracic Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, People's Republic of China
| | - Liu Ye
- The First Branch, The First Affiliated Hospital of Chongqing Medical University, Chongqing, People's Republic of China
| | - Hao-Yu Ran
- Department of Cardiothoracic Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, People's Republic of China
| | - Hao-Ming Shi
- Department of Cardiothoracic Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, People's Republic of China
| | - Cheng Zhang
- Department of Cardiothoracic Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, People's Republic of China
| | - Qing-Chen Wu
- Department of Cardiothoracic Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, People's Republic of China
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Laufenberg LJ, Crowell KT, Lang CH. Alcohol Acutely Antagonizes Refeeding-Induced Alterations in the Rag GTPase-Ragulator Complex in Skeletal Muscle. Nutrients 2021; 13:1236. [PMID: 33918604 PMCID: PMC8070399 DOI: 10.3390/nu13041236] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 03/17/2021] [Accepted: 04/02/2021] [Indexed: 02/07/2023] Open
Abstract
The Ragulator protein complex is critical for directing the Rag GTPase proteins and mTORC1 to the lysosome membrane mediating amino acid-stimulated protein synthesis. As there is a lack of evidence on alcohol's effect on the Rag-Ragulator complex as a possible mechanism for the development of alcoholic skeletal muscle wasting, the aim of our study was to examine alterations in various protein-protein complexes in the Rag-Ragulator pathway produced acutely by feeding and how these are altered by alcohol under in vivo conditions. Mice (C57Bl/6; adult males) were fasted, and then provided rodent chow for 30 min ("refed") or remained food-deprived ("fasted"). Mice subsequently received ethanol (3 g/kg ethanol) or saline intraperitoneally, and hindlimb muscles were collected 1 h thereafter for analysis. Refeeding-induced increases in myofibrillar and sarcoplasmic protein synthesis, and mTOR and S6K1 phosphorylation, were prevented by alcohol. This inhibition was not associated with a differential rise in the intracellular leucine concentration or plasma leucine or insulin levels. Alcohol increased the amount of the Sestrin1•GATOR2 complex in the fasted state and prevented the refeeding-induced decrease in Sestrin1•GATOR2 seen in control mice. Alcohol antagonized the increase in the RagA/C•Raptor complex formation seen in the refed state. Alcohol antagonized the increase in Raptor with immunoprecipitated LAMPTOR1 (part of the Ragulator complex) after refeeding and decreased the association of RagC with LAMPTOR1. Finally, alcohol increased the association of the V1 domain of v-ATPase with LAMPTOR1 and prevented the refeeding-induced decrease in v-ATPase V1 with LAMPTOR1. Overall, these data demonstrate that acute alcohol intake disrupts multiple protein-protein complexes within the Rag-Ragulator complex, which are associated with and consistent with the concomitant decline in nutrient-stimulated muscle protein synthesis under in vivo conditions.
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Affiliation(s)
- Lacee J. Laufenberg
- Department of Surgery, Penn State College of Medicine, Hershey, PA 17033, USA; (L.J.L.); (K.T.C.)
| | - Kristen T. Crowell
- Department of Surgery, Penn State College of Medicine, Hershey, PA 17033, USA; (L.J.L.); (K.T.C.)
- Beth Israel Deaconess Medical Center, Department of Surgery, Boston, MA 02215, USA
| | - Charles H. Lang
- Department of Surgery, Penn State College of Medicine, Hershey, PA 17033, USA; (L.J.L.); (K.T.C.)
- Department of Cellular & Molecular Physiology, Penn State College of Medicine, Hershey, PA 17033, USA
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Okano N, Naruge D, Kawai K, Kobayashi T, Nagashima F, Endou H, Furuse J. First-in-human phase I study of JPH203, an L-type amino acid transporter 1 inhibitor, in patients with advanced solid tumors. Invest New Drugs 2020; 38:1495-1506. [PMID: 32198649 DOI: 10.1007/s10637-020-00924-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 03/11/2020] [Indexed: 11/28/2022]
Abstract
This open-label first-in-human study evaluated JPH203, which is a novel selective L-type amino acid transporter 1 inhibitor. We also evaluated the association between the N-acetyltransferase 2 phenotype and outcomes. Japanese patients with advanced solid tumors received daily intravenous JPH203 treatment for 7 days, followed by a 21-day rest period, at escalating doses of 12-85 mg/m2. Dose-limiting toxicities were evaluated during the first cycle using a 3 + 3 design. The study enrolled 17 patients, although grade 3 liver dysfunction was detected in one of six patients receiving 60 mg/m2 and in the first patient to receive 85 mg/m2. Further enrollment was terminated and the maximum tolerated dose was defined as 60 mg/m2. The AUC∞ increased between 12 mg/m2 and 25 mg/m2, although no differences were observed at 25-40 mg/m2. Partial response was observed for one patient with biliary tract cancer (BTC) at the 12 mg/m2 dose, and disease control was achieved by 3 of 6 patients at the 12 mg/m2 and 25 mg/m2 dose levels. Based on these results, we recommend a phase II dose of 25 mg/m2. The disease control rate for BTC was 60%. Two patients with grade 3 liver dysfunction had the rapid N-acetyltransferase 2 phenotype, and disease control was more common for the non-rapid phenotype (50% vs. 12.5%). It appears that JPH203 was well-tolerated and provided promising activity against BTC. The N-acetyltransferase 2 phenotype might help predict the safety and efficacy of JPH203. Clinical trial registration: UMIN000016546.
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Affiliation(s)
- Naohiro Okano
- Department of Medical Oncology, Kyorin University Faculty of Medicine, 6-20-2, Shinkawa, Mitaka-shi, Tokyo, 181-8611, Japan.
| | - Daisuke Naruge
- Department of Medical Oncology, Kyorin University Faculty of Medicine, 6-20-2, Shinkawa, Mitaka-shi, Tokyo, 181-8611, Japan
| | - Kirio Kawai
- Department of Medical Oncology, Kyorin University Faculty of Medicine, 6-20-2, Shinkawa, Mitaka-shi, Tokyo, 181-8611, Japan
| | - Takaaki Kobayashi
- Department of Medical Oncology, Kyorin University Faculty of Medicine, 6-20-2, Shinkawa, Mitaka-shi, Tokyo, 181-8611, Japan
| | - Fumio Nagashima
- Department of Medical Oncology, Kyorin University Faculty of Medicine, 6-20-2, Shinkawa, Mitaka-shi, Tokyo, 181-8611, Japan
| | | | - Junji Furuse
- Department of Medical Oncology, Kyorin University Faculty of Medicine, 6-20-2, Shinkawa, Mitaka-shi, Tokyo, 181-8611, Japan
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Abstract
Amino acids are not only the building blocks of proteins, an indispensable component of cells, but also play versatile roles in regulating cell metabolism, proliferation, differentiation and growth by themselves or through their derivatives. At the whole body level, the bioavailability and metabolism of amino acids, interacting with other macronutrients, is critical for the physiological processes of reproduction including gametogenesis, fertilization, implantation, placentation, fetal growth and development. In fertilization and early pregnancy, histotroph in oviductal and uterine secretions provides nutrients and microenvironment for conceptus (embryo and extraembryonic membranes) development. These nutrients include select amino acids in histotroph (arginine, leucine and glutamine of particular interest) that stimulate conceptus growth and development, as well as interactions between maternal uterus and the conceptus, thus impacting maintenance of pregnancy, placental growth, development and functions, fetal growth and development, and consequential pregnancy outcomes. Gestational protein undernutrition causes fetal growth restriction and predisposes cardiovascular, metabolic diseases and others in offspring via multiple mechanisms, whereas the supplementation of glycine, leucine and taurine during pregnancy partially rescues growth restriction and beneficially modulates fetal programming. Thus, amino acids are essential for the fertility of humans and all animals.
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Affiliation(s)
- Haijun Gao
- Department of Obstetrics & Gynecology, Howard University College of Medicine, Washington, DC, USA.
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El Ansari R, Craze ML, Miligy I, Diez-Rodriguez M, Nolan CC, Ellis IO, Rakha EA, Green AR. The amino acid transporter SLC7A5 confers a poor prognosis in the highly proliferative breast cancer subtypes and is a key therapeutic target in luminal B tumours. Breast Cancer Res 2018; 20:21. [PMID: 29566741 PMCID: PMC5863851 DOI: 10.1186/s13058-018-0946-6] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 02/26/2018] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Breast cancer (BC) is a heterogeneous disease characterised by variant biology and patient outcome. The amino acid transporter, SLC7A5, plays a role in BC although its impact on patient outcome in different BC subtypes remains to be validated. This study aimed to determine whether the clinicopathological and prognostic value of SLC7A5 is different within the molecular classes of BC. METHODS SLC7A5 was assessed at the genomic level, using Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) data (n = 1980), and proteomic level, using immunohistochemical analysis and tissue microarray (TMA) (n = 2664; 1110 training and 1554 validation sets) in well-characterised primary BC cohorts. SLC7A5 expression correlated with clinicopathological and biological parameters, molecular subtypes and patient outcome. RESULTS SLC7A5 mRNA and protein expression were strongly correlated with larger tumour size and higher grade. High expression was observed in triple negative (TN), human epidermal growth factor receptor 2 (HER2)+, and luminal B subtypes. SLC7A5 mRNA and protein expression was significantly associated with the expression of the key regulator of tumour cell metabolism, c-MYC, specifically in luminal B tumours only (p = 0.001). High expression of SLC7A5 mRNA and protein was associated with poor patient outcome (p < 0.001) but only in the highly proliferative oestrogen receptor (ER)+/ luminal B (p = 0.007) and HER2+ classes of BC (p = 0.03). In multivariate analysis, SLC7A5 protein was an independent risk factor for shorter breast-cancer-specific survival only in ER+ high-proliferation tumours (p = 0.02). CONCLUSIONS SLC7A5 appears to play a role in the aggressive highly proliferative ER+ subtype driven by MYC and could act as a potential therapeutic target. Functional assessment is necessary to reveal the specific role played by this transporter in the ER+ highly proliferative subclass and HER2+ subclass of BC.
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Affiliation(s)
- Rokaya El Ansari
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB UK
| | - Madeleine L. Craze
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB UK
| | - Islam Miligy
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB UK
| | - Maria Diez-Rodriguez
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB UK
| | - Christopher C. Nolan
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB UK
| | - Ian O. Ellis
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB UK
- Breast Institute, Nottingham University Hospitals NHS Trust, Hucknall Road, Nottingham, NG5 1PB UK
| | - Emad A. Rakha
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB UK
- Breast Institute, Nottingham University Hospitals NHS Trust, Hucknall Road, Nottingham, NG5 1PB UK
| | - Andrew R. Green
- Academic Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB UK
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Hodson N, Brown T, Joanisse S, Aguirre N, West DWD, Moore DR, Baar K, Breen L, Philp A. Characterisation of L-Type Amino Acid Transporter 1 (LAT1) Expression in Human Skeletal Muscle by Immunofluorescent Microscopy. Nutrients 2017; 10:E23. [PMID: 29278358 DOI: 10.3390/nu10010023] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 11/16/2017] [Accepted: 12/13/2017] [Indexed: 12/21/2022] Open
Abstract
The branch chain amino acid leucine is a potent stimulator of protein synthesis in skeletal muscle. Leucine rapidly enters the cell via the L-Type Amino Acid Transporter 1 (LAT1); however, little is known regarding the localisation and distribution of this transporter in human skeletal muscle. Therefore, we applied immunofluorescence staining approaches to visualise LAT1 in wild type (WT) and LAT1 muscle-specific knockout (mKO) mice, in addition to basal human skeletal muscle samples. LAT1 positive staining was visually greater in WT muscles compared to mKO muscle. In human skeletal muscle, positive LAT1 staining was noted close to the sarcolemmal membrane (dystrophin positive staining), with a greater staining intensity for LAT1 observed in the sarcoplasmic regions of type II fibres (those not stained positively for myosin heavy-chain 1, Type II—25.07 ± 5.93, Type I—13.71 ± 1.98, p < 0.01), suggesting a greater abundance of this protein in these fibres. Finally, we observed association with LAT1 and endothelial nitric oxide synthase (eNOS), suggesting LAT1 association close to the microvasculature. This is the first study to visualise the distribution and localisation of LAT1 in human skeletal muscle. As such, this approach provides a validated experimental platform to study the role and regulation of LAT1 in human skeletal muscle in response to various physiological and pathophysiological models.
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Lin Y, Duan X, Lv H, Yang Y, Liu Y, Gao X, Hou X. The effects of L-type amino acid transporter 1 on milk protein synthesis in mammary glands of dairy cows. J Dairy Sci 2017; 101:1687-1696. [PMID: 29224866 DOI: 10.3168/jds.2017-13201] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 10/12/2017] [Indexed: 01/23/2023]
Abstract
The mammary gland requires the uptake of AA for milk protein synthesis during lactation. The L-type amino acid transporter 1 (LAT1, encoded by SLC7A5), found in many different types of mammalian cells, is indispensable as a transporter of essential AA to maintain cell growth and protein synthesis. However, the function of LAT1 in regulating milk protein synthesis in the mammary gland of the dairy cow remains largely unknown. For the current study, we characterized the relationship between LAT1 expression and milk protein synthesis in lactating dairy cows and investigated whether the mammalian target of rapamycin complex 1 (mTORC1) signaling controls the expression of LAT1 in their mammary glands. We found that LAT1 and the heavy chain of its chaperone, 4F2, were expressed in mammary tissues of lactating cows, with the expression levels of LAT1 and the 4F2 heavy chain being significantly greater in lactating mammary tissues with high-milk protein content (milk yield, 33.8 ± 2.1 kg/d; milk protein concentration >3%, wt/vol,; n = 3) than in tissues from cows with low-milk protein content (milk yield, 33.7 ± 0.5 kg/d; milk protein concentration <3%, wt/vol; n = 3). Immunofluorescence staining of sectioned mammary tissues from cows with high and low milk protein content showed that LAT1 was located on the whole plasma membrane of alveolar epithelial cells, suggesting that LAT1 provides essential AA to the mammary gland. In cultured mammary epithelial cells from the dairy cows with high-milk protein content, knockdown of LAT1 expression decreased cell viability and β-casein expression; in contrast, overexpression of LAT1 had the opposite effect. Inhibition of mTORC1 by rapamycin attenuated the phosphorylation of molecules related to mTORC1 signaling and caused a marked decrease in LAT1 expression in the cultured cells; expression of β-casein also decreased significantly. These results suggest that LAT1 is involved in milk protein synthesis in the mammary glands of lactating dairy cows and that the mTORC1 signaling pathway might be a control point for regulation of LAT1 expression, which could ultimately be used to alter milk protein synthesis.
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Affiliation(s)
- Ye Lin
- College of Life Science, Northeast Agricultural University, Harbin 150030, China; Key Laboratory of Dairy Science of Education Ministry, and Northeast Agricultural University, Harbin 150030, China
| | - Xiaoyu Duan
- College of Life Science, Northeast Agricultural University, Harbin 150030, China
| | - He Lv
- College of Life Science, Northeast Agricultural University, Harbin 150030, China
| | - Yang Yang
- College of Life Science, Northeast Agricultural University, Harbin 150030, China
| | - Ying Liu
- College of Life Science, Northeast Agricultural University, Harbin 150030, China
| | - Xuejun Gao
- College of Life Science, Northeast Agricultural University, Harbin 150030, China; Key Laboratory of Dairy Science of Education Ministry, and Northeast Agricultural University, Harbin 150030, China
| | - Xiaoming Hou
- College of Life Science, Northeast Agricultural University, Harbin 150030, China; Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, Northeast Agricultural University, Harbin 150030, China.
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11
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Duan X, Lin Y, Lv H, Yang Y, Jiao H, Hou X. Methionine Induces LAT1 Expression in Dairy Cow Mammary Gland by Activating the mTORC1 Signaling Pathway. DNA Cell Biol 2017; 36:1126-1133. [DOI: 10.1089/dna.2017.3792] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
- Xiaoyu Duan
- College of Life Science, Northeast Agricultural University, Harbin, China
| | - Ye Lin
- College of Life Science, Northeast Agricultural University, Harbin, China
- Key Laboratory of Dairy Science of Education Ministry, Northeast Agricultural University, Harbin, China
| | - He Lv
- College of Life Science, Northeast Agricultural University, Harbin, China
| | - Yang Yang
- College of Life Science, Northeast Agricultural University, Harbin, China
| | - Hongtao Jiao
- College of Life Science, Northeast Agricultural University, Harbin, China
| | - Xiaoming Hou
- College of Life Science, Northeast Agricultural University, Harbin, China
- Key Laboratory of Animal Cellular and Genetics Engineering of Heilongjiang Province, Northeast Agricultural University, Harbin, China
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12
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Nakai N, Kawano F, Murakami T, Nakata K, Higashida K. Leucine supplementation after mechanical stimulation activates protein synthesis via L-type amino acid transporter 1 in vitro. J Cell Biochem 2017; 119:2094-2101. [PMID: 28856713 DOI: 10.1002/jcb.26371] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 08/23/2017] [Indexed: 11/11/2022]
Abstract
Branched-chain amino acid supplements consumed following exercise are widely used to increase muscle mass. Although both exercise (ie, mechanical stimulation) and branched-chain amino acid leucine supplementation have been reported to stimulate muscle protein synthesis by activating the mammalian target of rapamycin (mTOR) signaling pathway independently, the mechanisms underlying their synergistic effects are largely unknown. Utilizing cultured differentiated C2C12 myotubes, we established a combination treatment model in which the cells were subjected to cyclic uniaxial mechanical stretching (4 h, 15%, 1 Hz) followed by stimulation with 2 mM leucine for 45 min. Phosphorylation of p70 S6 kinase (p70S6K), an mTOR-regulated marker of protein translation initiation, was significantly increased following mechanical stretching alone but returned to the baseline after 4 h. Leucine supplementation further increased p70S6K phosphorylation, with a greater increase observed in the stretched cells than in the non-stretched cells. Notably, the expression of L-type amino acid transporter 1 (LAT1), a stimulator of the mTOR pathway, was also increased by mechanical stretching, and siRNA-mediated knockdown partially attenuated leucine-induced p70S6K phosphorylation. These results suggest that mechanical stretching promotes LAT1 expression and, consequently, amino acid uptake, leading to enhanced leucine-induced activation of protein synthesis. LAT1 has been demonstrated to be a point of crosstalk between exercise- and nutrition-induced skeletal muscle growth.
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Affiliation(s)
- Naoya Nakai
- Department of Nutrition, University of Shiga Prefecture, Hikone, Shiga, Japan
| | - Fuminori Kawano
- Graduate School of Health Sciences, Matsumoto University, Matsumoto, Nagano, Japan
| | - Taro Murakami
- Department of Nutrition, Shigakkan University, Ohbu, Aichi, Japan
| | - Ken Nakata
- Medicine for Sports and Performing Arts, Graduate School of Medicine, Osaka University, Toyonaka, Osaka, Japan
| | - Kazuhiko Higashida
- Department of Nutrition, University of Shiga Prefecture, Hikone, Shiga, Japan
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13
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Duan Y, Zeng L, Li F, Wang W, Li Y, Guo Q, Ji Y, Tan B, Yin Y. Effect of branched-chain amino acid ratio on the proliferation, differentiation, and expression levels of key regulators involved in protein metabolism of myocytes. Nutrition 2016; 36:8-16. [PMID: 28336113 DOI: 10.1016/j.nut.2016.10.016] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 10/11/2016] [Accepted: 10/30/2016] [Indexed: 02/06/2023]
Abstract
OBJECTIVES Branched-chain amino acids (BCAAs), including leucine (Leu), isoleucine (Ile), and valine (Val), are key regulators of protein synthesis in muscle. The aim of this study was to investigate the effect of different BCAA ratios (Leu:Ile:Val) on the proliferation, differentiation, and expression levels of the regulators related to protein metabolism of C2 C12 myocytes. METHODS Studies were conducted in C2C12 myocytes exposed to different BCAA ratios (Leu: Ile: Val = 0, 1:0.25:0.25, 1:1:1). RESULTS The ratio of 1:0.25:0.25 increased cell viability and promoted cell cycle progression from G0/G1 phase to S phase, which was an indicator of proliferation enhancement (P < 0.05). Moreover, this optimal ratio (1:0.25:0.25) promoted the differentiation of myocytes into myotubes by upregulating myogenin and interleukin-15 gene expression, and differently regulated the expression of L-type amino acid transporter 1 and 4 and system ASC amino acid transporters 2. Furthermore, the ratio stimulated mTOR expression at the mRNA and phosphorylated protein levels, as well as ribosomal protein S6 kinase and regulatory-associated protein of mTOR (raptor). In contrast, the optimal ratio decreased the amount of ubiquitin ligase muscle-specific RING finger 1 and muscle atrophy F-box during proliferation and differentiation (P < 0.05). No change was observed in the expression of key genes related to energy metabolism except for uncoupling protein 3 (P > 0.05). CONCLUSIONS The results suggested that appropriate BCAA ratios could enhance proliferation and differentiation of the C2 C12 myocytes, also mediate the key regulators related to protein metabolism including the mTORC1 pathway. A proper utilization of balanced BCAA ratio in food would be beneficial to human and animal nutrition.
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Affiliation(s)
- Yehui Duan
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production; Hunan Provincial Engineering Research Center for Healthy Livestock and Poultry Production, Changsha, China; Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Changsha, China; University of Chinese Academy of Sciences, Beijing, China
| | - Liming Zeng
- Science College of Jiangxi Agricultural University, Nanchang, Jiangxi, China
| | - Fengna Li
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production; Hunan Provincial Engineering Research Center for Healthy Livestock and Poultry Production, Changsha, China; Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Changsha, China; Hunan Collaborative Innovation Center for Utilization of Botanical Functional Ingredients, Changsha, China; Hunan Co-Innovation Center of Animal Production Safety, Changsha, China.
| | - Wenlong Wang
- School of Biology, Hunan Normal University, Changsha, China
| | - Yinghui Li
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production; Hunan Provincial Engineering Research Center for Healthy Livestock and Poultry Production, Changsha, China; Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Changsha, China; University of Chinese Academy of Sciences, Beijing, China
| | - Qiuping Guo
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production; Hunan Provincial Engineering Research Center for Healthy Livestock and Poultry Production, Changsha, China; Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Changsha, China; University of Chinese Academy of Sciences, Beijing, China
| | - Yujiao Ji
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production; Hunan Provincial Engineering Research Center for Healthy Livestock and Poultry Production, Changsha, China
| | - Bi'e Tan
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production; Hunan Provincial Engineering Research Center for Healthy Livestock and Poultry Production, Changsha, China; Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Changsha, China; Hunan Collaborative Innovation Center for Utilization of Botanical Functional Ingredients, Changsha, China; Hunan Co-Innovation Center of Animal Production Safety, Changsha, China
| | - Yulong Yin
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production; Hunan Provincial Engineering Research Center for Healthy Livestock and Poultry Production, Changsha, China; Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Changsha, China; School of Biology, Hunan Normal University, Changsha, China
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14
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Wu P, Li Y, Cheng J, Chen L, Zeng M, Wu Y, Wang J, Zhang J, Chu W. Transcriptome Analysis and Postprandial Expression of Amino Acid Transporter Genes in the Fast Muscles and Gut of Chinese Perch (Siniperca chuatsi). PLoS One 2016; 11:e0159533. [PMID: 27463683 PMCID: PMC4963124 DOI: 10.1371/journal.pone.0159533] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 07/04/2016] [Indexed: 01/09/2023] Open
Abstract
The characterization of the expression and regulation of growth-related genes in the muscles of Chinese perch is of great interest to aquaculturists because of the commercial value of the species. The transcriptome annotation of the skeletal muscles is a crucial step in muscle growth-related gene analysis. In this study, we generated 52 504 230 reads of mRNA sequence data from the fast muscles of the Chinese perch by using Solexa/Illumina RNA-seq. Twenty-one amino acid transporter genes were annotated by searching protein and gene ontology databases, and postprandial changes in their transcript abundance were assayed after administering a single satiating meal to Chinese perch juveniles (body mass, approximately 100 g), following fasting for 1 week. The gut content of the Chinese perch increased significantly after 1 h and remained high for 6 h following the meal and emptied within 48-96 h. Expression of eight amino acid transporter genes was assayed in the fast muscles through quantitative real-time polymerase chain reaction at 0, 1, 3, 6, 12, 24, 48, and 96 h. Among the genes, five transporter transcripts were markedly up-regulated within 1 h of refeeding, indicating that they may be potential candidate genes involved in the rapid-response signaling system regulating fish myotomal muscle growth. These genes display coordinated regulation favoring the resumption of myogenesis responding to feeding.
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Affiliation(s)
- Ping Wu
- Department of Bioengneering and Environmental Science, Changsha University, Changsha, 410003, China
- Collaborative Innovation Center for Efficient and Health Production of Fisheries in Hunan Province, Changde, 415000, China
| | - Yulong Li
- Department of Bioengneering and Environmental Science, Changsha University, Changsha, 410003, China
| | - Jia Cheng
- Department of Bioengneering and Environmental Science, Changsha University, Changsha, 410003, China
| | - Lin Chen
- Department of Bioengneering and Environmental Science, Changsha University, Changsha, 410003, China
| | - Ming Zeng
- Institute of Hunan Aquaculture and Fishes, Changsha, 410005, China
| | - Yuanan Wu
- Institute of Hunan Aquaculture and Fishes, Changsha, 410005, China
| | - Jianhua Wang
- Department of Bioengneering and Environmental Science, Changsha University, Changsha, 410003, China
| | - Jianshe Zhang
- Department of Bioengneering and Environmental Science, Changsha University, Changsha, 410003, China
- Collaborative Innovation Center for Efficient and Health Production of Fisheries in Hunan Province, Changde, 415000, China
- * E-mail: (JSZ); (WYC)
| | - Wuying Chu
- Department of Bioengneering and Environmental Science, Changsha University, Changsha, 410003, China
- Collaborative Innovation Center for Efficient and Health Production of Fisheries in Hunan Province, Changde, 415000, China
- * E-mail: (JSZ); (WYC)
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15
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Abstract
The branched-chain amino acids (BCAA) leucine, isoleucine and valine, are essential amino acids that play a critical role in cellular signalling and metabolism. They acutely stimulate insulin secretion and activate the regulatory serine/threonine kinase mammalian target of rapamycin complex 1 (mTORC1), a kinase that promotes increased β-cell mass and function. The effects of BCAA on cellular function are dependent on their active transport into the mammalian cells via amino acid transporters and thus the expression and activity of these transporters likely influence β-cell signalling and function. In this report, we show that the System-L transporters are required for BCAA uptake into clonal β-cell lines and pancreatic islets, and that these are essential for signalling to mTORC1. Further investigation revealed that the System-L amino acid transporter 1 (LAT1) is abundantly expressed in the islets, and that knockdown of LAT1 using siRNA inhibits mTORC1 signalling, leucine-stimulated insulin secretion and islet cell proliferation. In summary, we show that the LAT1 is required for regulating β-cell signalling and function in islets and thus may be a novel pharmacological/nutritional target for the treatment and prevention of type 2 diabetes.
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Affiliation(s)
- Qi Cheng
- Research School of BiologyAustralian National University, Acton, Australia
| | - Violeta D Beltran
- Department of InfectionImmunity and Inflammation, University of Leicester, UK
| | - Stanley M H Chan
- Health Innovations Research Institute (HIRI)School of Medical Sciences, RMIT University, Bundoora, Australia
| | - Jeremy R Brown
- Department of InfectionImmunity and Inflammation, University of Leicester, UK
| | - Alan Bevington
- Department of InfectionImmunity and Inflammation, University of Leicester, UK
| | - Terence P Herbert
- Health Innovations Research Institute (HIRI)School of Medical Sciences, RMIT University, Bundoora, Australia
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16
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Li Y, Wei H, Li F, Chen S, Duan Y, Guo Q, Liu Y, Yin Y. Supplementation of branched-chain amino acids in protein-restricted diets modulates the expression levels of amino acid transporters and energy metabolism associated regulators in the adipose tissue of growing pigs. ACTA ACUST UNITED AC 2016; 2:24-32. [PMID: 29767034 PMCID: PMC5940986 DOI: 10.1016/j.aninu.2016.01.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 01/29/2016] [Accepted: 01/31/2016] [Indexed: 12/17/2022]
Abstract
This experiment was conducted to investigate the effects of branched-chain amino acids (BCAA) supplemented in protein-restricted diets on the growth performance and the expression profile of amino acid transporters and energy metabolism related regulators in the white adipose tissue (WAT) of different regional depots including dorsal subcutaneous adipose (DSA) and abdominal subcutaneous adipose (ASA). A total of 24 crossbred barrows (7.40 ± 0.70 kg) were randomly divided into 4 groups and were fed the following isocaloric diets for 33 days: 1) a recommended adequate protein diet (AP, 20% CP, as a positive control); 2) a low protein diet (LP, 17% CP); 3) the LP diet supplemented with BCAA (LP + B, 17% CP) to reach the same level of the AP diet group; 4) the LP diet supplemented with 2 times the amount of BCAA (LP + 2B, 17% CP). The daily gain and daily feed intake of the LP diet group were the lowest among all the treatments (P < 0.01). The feed conversion was improved markedly in the group of LP + B compared with the LP diet group (P < 0.05). No significant difference was noted for the serum biochemical parameter concentrations of glucose, triglyceride, nonesterified fatty acid and insulin among the groups (P > 0.05). Moreover, BCAA supplementation down-regulated the expression levels of amino acid transporters including L-type amino acid transporter 1 and sodium-coupled neutral amino acid transporter 2 in DSA, but up-regulated the expression level of L-type amino acid transporter 4 in ASA (P < 0.05). Meanwhile, the energy sensor AMP-activated protein kinase α was activated in the DSA of pigs fed LP diet and in the ASA of the pigs fed AP or LP + 2B diets (P < 0.05). The mRNA expression profile of the selected mitochondrial component and mitochondrial biogenesis associated regulators in DSA and ASA also responded differently to dietary BCAA supplementation. These results suggested that the growth performance of growing pigs fed protein restricted diets supplemented with BCAA could catch up to that of the pigs fed AP diets. The results also partly demonstrated that the regulation mechanisms of BCAA are different in the adipose tissues of different depots.
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Affiliation(s)
- Yinghui Li
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
- University of Chinese Academy of Sciences, Beijing 100039, China
| | - Hongkui Wei
- College of Animal Sciences, Huazhong Agricultural University, Wuhan 430070, China
| | - Fengna Li
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
- Hunan Co-Innovation Center of Animal Production Safety (CICAPS), Changsha 410128, China
- Corresponding authors.
| | - Shuai Chen
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
- University of Chinese Academy of Sciences, Beijing 100039, China
| | - Yehui Duan
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
- University of Chinese Academy of Sciences, Beijing 100039, China
| | - Qiuping Guo
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
- University of Chinese Academy of Sciences, Beijing 100039, China
| | - Yingying Liu
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
- University of Chinese Academy of Sciences, Beijing 100039, China
| | - Yulong Yin
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China
- Changsha Lvye Biotechnology Limited Company Academician Expert Workstation, Changsha 410126, China
- Hang Zhou King Techina Limited Company Academician Expert Workstation, Hangzhou 311107, China
- Corresponding authors.
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Xu M, Sakamoto S, Matsushima J, Kimura T, Ueda T, Mizokami A, Kanai Y, Ichikawa T. Up-Regulation of LAT1 during Antiandrogen Therapy Contributes to Progression in Prostate Cancer Cells. J Urol 2015; 195:1588-1597. [PMID: 26682754 DOI: 10.1016/j.juro.2015.11.071] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/27/2015] [Indexed: 02/06/2023]
Abstract
PURPOSE Cancer cells require massive amounts of amino acids for survival. LAT1 (L-type amino acid transporter 1) transports essential amino acids, including leucine, which trigger the downstream mTOR (mammalian target of rapamycin) pathway. We examined the association between androgen receptor and LAT1, and the association between LAT1 expression and the acquisition of castration resistance. MATERIALS AND METHODS Western blot and real-time polymerase chain reaction were performed to study protein and mRNA expression. siRNA was used to knock down target genes. A total of 92 prostate biopsy specimens of patients who underwent androgen deprivation therapy were used for immunohistochemical analyses. Cox hazard proportional models and the Kaplan-Meier method were used for statistical analyses. RESULTS LAT1 was highly expressed in hormone resistant prostate cancer cell lines. Knockdown of LAT1 in LNCaP and C4-2 cells significantly suppressed cell proliferation, migration and invasion. Androgen receptor siRNA or androgen receptor blocking through bicalutamide (10 μM) or MDV3100 (10 μM) significantly increased LAT1 expression (p <0.01). Treatment with dihydrotestosterone (0.1 to 10 nM) reduced LAT1 expression in a dose dependent manner (p <0.01). Bicalutamide/MDV3100 plus siLAT1 synergistically suppressed prostate cancer cell proliferation compared to single inhibition by androgen receptor or LAT1 (p <0.01). High LAT1 expression correlated with significantly shorter prostate specific antigen recurrence-free survival in patients receiving androgen deprivation therapy (p <0.0001). LAT1 expression was an independent predictor of castration resistance on multivariate analysis (HR 3.56, p = 0.0133). CONCLUSIONS The current data may indicate a novel mechanism to acquire castration resistance through activation of the amino acid transporter LAT1.
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Affiliation(s)
- Minhui Xu
- Department of Urology, Chiba University Graduate School of Medicine, Chiba, Japan
| | - Shinichi Sakamoto
- Department of Urology, Chiba University Graduate School of Medicine, Chiba, Japan.
| | - Jun Matsushima
- Department of Diagnostic Pathology, Chiba University Graduate School of Medicine, Chiba, Japan
| | - Toru Kimura
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Tokyo, Japan
| | - Takeshi Ueda
- Prostate Center and Division of Urology, Chiba Cancer Center, Chiba, Japan
| | - Atsushi Mizokami
- Department of Integrative Cancer Therapy and Urology, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan
| | - Yoshikatsu Kanai
- Division of Bio-system Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Tomohiko Ichikawa
- Department of Urology, Chiba University Graduate School of Medicine, Chiba, Japan
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18
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Liu Y, Kong X, Li F, Tan B, Li Y, Duan Y, Yin Y, He J, Hu C, Blachier F, Wu G. Co-dependence of genotype and dietary protein intake to affect expression on amino acid/peptide transporters in porcine skeletal muscle. Amino Acids 2016; 48:75-90. [PMID: 26255284 DOI: 10.1007/s00726-015-2066-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 07/29/2015] [Indexed: 10/23/2022]
Abstract
A total of 96 barrows (48 pure-bred Bama mini-pigs representing fatty genotype, and 48 Landrace pigs representing lean genotype) were randomly assigned to either a low- or adequate-protein treatment diet. The experimental period commenced at 5 weeks of age and extended to the finishing period. After euthanasia, blood and skeletal muscle samples were collected from pigs at the nursery, growing, and finishing phases. Our results indicate that the concentrations of free AAs in the plasma and muscle decreased as the age of the pigs increased. In addition, a strain × growth phase interaction (P < 0.05) was observed for the free AA pool in the plasma and muscle. The low-protein diet upregulated (P < 0.05) the mRNA levels for T1R1/T1R3 involved in glutamate binding, but downregulated (P < 0.05) the mRNA levels for PAT1, PAT2, and ASCT2, which transport neutral AAs into muscles. Bama mini-pigs had higher (P < 0.05) mRNA levels for LAT1, SNAT2, and EAAC1, but a lower (P < 0.05) mRNA level for PepT1, compared with Landrace pigs. Collectively, our findings indicate that adequate provision of dietary protein plays an important role in regulating profiles of free AA pools and expression of key AA/peptide transporters/transceptors in a genotype- and tissue-specific manner.
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Wu L, Liao P, He L, Feng Z, Ren W, Yin J, Duan J, Li T, Yin Y. Dietary L-arginine supplementation protects weanling pigs from deoxynivalenol-induced toxicity. Toxins (Basel) 2015; 7:1341-54. [PMID: 25884909 DOI: 10.3390/toxins7041341] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 04/01/2015] [Accepted: 04/07/2015] [Indexed: 12/20/2022] Open
Abstract
This study was conducted to determine the positive effects of dietary supplementation with l-arginine (Arg) on piglets fed a deoxynivalenol (DON)-contaminated diet. A total of eighteen, 28-day-old healthy weanling pigs were randomly assigned into one of three groups: uncontaminated basal diet (control group), 6 mg/kg DON-contaminated diet (DON group) and 6 mg/kg DON + 1% l-arginine (DON + ARG group). After 21 days of Arg supplementation, piglets in the DON and DON + ARG groups were challenged by feeding 6 mg/kg DON-contaminated diet for seven days. The results showed that DON resulted in damage to piglets. However, clinical parameters, including jejunal morphology, amino acid concentrations in the serum, jejunum and ileum, were improved by Arg (p < 0.05). Furthermore, the mRNA levels for sodium-glucose transporter-1 (SGLT-1), glucose transporter type-2 (GLUT-2) and y+l-type amino acid transporter-1 (y+LAT-1) were downregulated in the DON group, but the values were increased in the DON + ARG group (p < 0.05). Collectively, these results indicate that dietary supplementation with Arg exerts a protective role in pigs fed DON-contaminated diets.
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Margolis LM, Rivas DA. Implications of exercise training and distribution of protein intake on molecular processes regulating skeletal muscle plasticity. Calcif Tissue Int 2015; 96:211-21. [PMID: 25348078 PMCID: PMC6691734 DOI: 10.1007/s00223-014-9921-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 10/15/2014] [Indexed: 12/19/2022]
Abstract
To optimize its function, skeletal muscle exhibits exceptional plasticity and possesses the fundamental capacity to adapt its metabolic and contractile properties in response to various external stimuli (e.g., external loading, nutrient availability, and humoral factors). The adaptability of skeletal muscle, along with its relatively large mass and high metabolic rate, makes this tissue an important contributor to whole body health and mobility. This adaptational process includes changes in the number, size, and structural/functional properties of the myofibers. The adaptations of skeletal muscle to exercise are highly interrelated with dietary intake, particularly dietary protein, which has been shown to further potentiate exercise training-induced adaptations. Understanding the molecular adaptation of skeletal muscle to exercise and protein consumption is vital to elicit maximum benefit from exercise training to improve human performance and health. In this review, we will provide an overview of the molecular pathways regulating skeletal muscle adaptation to exercise and protein, and discuss the role of subsequent timing of nutrient intake following exercise.
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Affiliation(s)
- Lee M Margolis
- Nutrition, Exercise Physiology and Sarcopenia Laboratory, Jean Mayer USDA Human Nutrition Research Center On Aging, Tufts University, 711 Washington Street, Boston, MA, 02111, USA
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Jiang R, Teng Y, Huang Y, Gu J, Ma L, Li M, Zhou Y. Preeclampsia serum-induced collagen I expression and intracellular calcium levels in arterial smooth muscle cells are mediated by the PLC-γ1 pathway. Exp Mol Med 2014; 46:e115. [PMID: 25257609 DOI: 10.1038/emm.2014.59] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 07/28/2014] [Accepted: 07/31/2014] [Indexed: 01/08/2023] Open
Abstract
In women with preeclampsia (PE), endothelial cell (EC) dysfunction can lead to altered secretion of paracrine factors that induce peripheral vasoconstriction and proteinuria. This study examined the hypothesis that PE sera may directly or indirectly, through human umbilical vein ECs (HUVECs), stimulate phospholipase C-γ1-1,4,5-trisphosphate (PLC-γ1-IP3) signaling, thereby increasing protein kinase C-α (PKC-α) activity, collagen I expression and intracellular Ca2+ concentrations ([Ca2+]i) in human umbilical artery smooth muscle cells (HUASMCs). HUASMCs and HUVECs were cocultured with normal or PE sera before PLC-γ1 silencing. Increased PLC-γ1 and IP3 receptor (IP3R) phosphorylation was observed in cocultured HUASMCs stimulated with PE sera (P<0.05). In addition, PE serum significantly increased HUASMC viability and reduced their apoptosis (P<0.05); these effects were abrogated with PLC-γ1 silencing. Compared with normal sera, PE sera increased [Ca2+]i in cocultured HUASMCs (P<0.05), which was inhibited by PLC-γ1 and IP3R silencing. Finally, PE sera-induced PKC-α activity and collagen I expression was inhibited by PLC-γ1 small interfering RNA (siRNA) (P<0.05). These results suggest that vasoactive substances in the PE serum may induce deposition in the extracellular matrix through the activation of PLC-γ1, which may in turn result in thickening and hardening of the placental vascular wall, placental blood supply shortage, fetal hypoxia–ischemia and intrauterine growth retardation or intrauterine fetal death. PE sera increased [Ca2+]i and induced PKC-α activation and collagen I expression in cocultured HUASMCs via the PLC-γ1 pathway.
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Toyoda M, Kaira K, Ohshima Y, Ishioka NS, Shino M, Sakakura K, Takayasu Y, Takahashi K, Tominaga H, Oriuchi N, Nagamori S, Kanai Y, Oyama T, Chikamatsu K. Prognostic significance of amino-acid transporter expression (LAT1, ASCT2, and xCT) in surgically resected tongue cancer. Br J Cancer 2014; 110:2506-13. [PMID: 24762957 PMCID: PMC4021522 DOI: 10.1038/bjc.2014.178] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 01/14/2014] [Accepted: 03/04/2014] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Amino-acid transporters are necessary for the tumour cell growth and survival, and have a crucial role in the development and invasiveness of cancer cells. But, it remains unclear about the prognostic significance of L-type amino-acid transporter 1 (LAT1), system ASC amino-acid transporter-2 (ASCT2), and xCT expression in patients with tongue cancer. We conducted the clinicopathological study to investigate the protein expression of these amino-acid transporters in tongue cancer. METHODS Eighty-five patients with surgically resected tongue cancer were evaluated. Tumour sections were stained by immunohistochemistry for LAT1, ASCT2, xCT, 4F2hc/CD98hc (4F2hc), Ki-67, and microvessel density (MVD) determined by CD34, and p53. RESULTS L-type amino-acid transporter 1 and 4F2hc were highly expressed in 61% (52 out of 85) and 45% (38 out of 47), respectively. ASC amino-acid transporter-2 and xCT were positively expressed in 59% (50 out of 85) and 21% (18 out of 85), respectively. The expression of both LAT1 and ASCT2 was significantly associated with disease staging, lymph-node metastasis, lymphatic permeation, 4F2hc expression and cell proliferation (Ki-67). xCT expression indicated a significant association with advanced stage and tumour factor. By univariate analysis, disease staging, lymphatic permeation, vascular invasion, LAT1, ASCT2, 4F2hc, and Ki-67 had a significant relationship with overall survival. Multivariate analysis confirmed that LAT1 was an independent prognostic factor for predicting poor prognosis. CONCLUSIONS L-type amino-acid transporter 1 and ASCT2 can serve as a significant prognostic factor for predicting worse outcome after surgical treatment and may have an important role in the development and aggressiveness of tongue cancer.
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Affiliation(s)
- M Toyoda
- Department of Otolaryngology-Head and Neck Surgery, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - K Kaira
- Department of Molecular Medicine and Science, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
- Department of Diagnostic Pathology, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
- Oncology Center, Gunma University Hospital, Maebashi, Gunma, Japan
| | - Y Ohshima
- Medical Radioisotope Application Group, Quantum Beam Science Directorate, Japan Atomic Energy Agency, Watanuki, Takasaki, Gunma, Japan
| | - N S Ishioka
- Medical Radioisotope Application Group, Quantum Beam Science Directorate, Japan Atomic Energy Agency, Watanuki, Takasaki, Gunma, Japan
| | - M Shino
- Department of Otolaryngology-Head and Neck Surgery, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - K Sakakura
- Department of Otolaryngology-Head and Neck Surgery, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Y Takayasu
- Department of Otolaryngology-Head and Neck Surgery, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - K Takahashi
- Department of Otolaryngology-Head and Neck Surgery, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - H Tominaga
- Department of Molecular Imaging, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - N Oriuchi
- Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - S Nagamori
- Division of Bio-System Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Y Kanai
- Division of Bio-System Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - T Oyama
- Department of Diagnostic Pathology, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - K Chikamatsu
- Department of Otolaryngology-Head and Neck Surgery, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
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Shimizu K, Kaira K, Tomizawa Y, Sunaga N, Kawashima O, Oriuchi N, Tominaga H, Nagamori S, Kanai Y, Yamada M, Oyama T, Takeyoshi I. ASC amino-acid transporter 2 (ASCT2) as a novel prognostic marker in non-small cell lung cancer. Br J Cancer 2014; 110:2030-9. [PMID: 24603303 PMCID: PMC3992511 DOI: 10.1038/bjc.2014.88] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Revised: 01/19/2014] [Accepted: 01/23/2014] [Indexed: 01/26/2023] Open
Abstract
Background: ASC amino-acid transporter 2 (ASCT2) is a major glutamine transporter that has an essential role in tumour growth and progression. Although ASCT2 is highly expressed in various cancer cells, the clinicopathological significance of its expression in non-small cell lung cancer (NSCLC) remains unclear. Methods: One hundred and four patients with surgically resected NSCLC were evaluated as one institutional cohort. Tumour sections were stained by immunohistochemistry (IHC) for ASCT2, Ki-67, phospho-mTOR (mammalian target of rapamycin), and CD34 to assess the microvessel density. Two hundred and four patients with NSCLC were also validated by IHC from an independent cohort. Results: ASC amino-acid transporter 2 was expressed in 66% of patients, and was closely correlated with disease stage, lymphatic permeation, vascular invasion, CD98, cell proliferation, angiogenesis, and mTOR phosphorylation, particularly in patients with adenocarcinoma (AC). Moreover, two independent cohorts confirmed that ASCT2 was an independent marker for poor outcome in AC patients. Conclusions: ASC amino-acid transporter 2 expression has a crucial role in the metastasis of pulmonary AC, and is a potential molecular marker for predicting poor prognosis after surgery.
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Affiliation(s)
- K Shimizu
- Department of Thoracic and Visceral Surgery, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma 371-8511, Japan
| | - K Kaira
- 1] Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma, Japan [2] Department of Diagnostic Pathology, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma, Japan
| | - Y Tomizawa
- Department of Internal Medicine, NHO Nishi-Gunma Hospital, 2854 Kanai Shibukawa, Gunma, Japan
| | - N Sunaga
- Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma, Japan
| | - O Kawashima
- Department of Surgery, NHO Nishi-Gunma Hospital, 2854 Kanai Shibukawa, Gunma, Japan
| | - N Oriuchi
- Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma, Japan
| | - H Tominaga
- Department of Molecular Imaging, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma, Japan
| | - S Nagamori
- Division of Bio-system Pharmacology, Department of Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Y Kanai
- Division of Bio-system Pharmacology, Department of Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - M Yamada
- Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma, Japan
| | - T Oyama
- Department of Diagnostic Pathology, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma, Japan
| | - I Takeyoshi
- Department of Thoracic and Visceral Surgery, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma 371-8511, Japan
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Kaira K, Sunose Y, Ohshima Y, Ishioka NS, Arakawa K, Ogawa T, Sunaga N, Shimizu K, Tominaga H, Oriuchi N. Clinical significance of L-type amino acid transporter 1 expression as a prognostic marker and potential of new targeting therapy in biliary tract cancer. BMC Cancer. 2013;13:482. [PMID: 24131658 PMCID: PMC4016614 DOI: 10.1186/1471-2407-13-482] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Accepted: 09/25/2013] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The expression of L-type amino acid transporter 1 (LAT1) has been described to play essential roles in tumor cell growth and survival. However, it remains unclear about the clinicopathological significance of LAT1 expression in biliary tract cancer. This study was conducted to determine biological significance of LAT1 expression and investigate whether LAT1 could be a prognostic biomarker for biliary tract cancer. METHODS A total of 139 consecutive patients with resected pathologic stage I-IV biliary tract adenocarcinoma were retrospectively reviewed. Tumor specimens were stained by immunohistochemistry for LAT1, Ki-67, microvessel density determined by CD34, and p53; and prognosis of patients was correlated. Biological significance of LAT1 expression was investigated by in vitro and in vivo experiments with LAT inhibitor, 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) using cholangiocarcinoma cell line. RESULTS In total patients, high LAT1 expressions were recognized in 64.0%. The expression of LAT1 was closely correlated with lymphatic metastases, cell proliferation and angiogenesis, and was a significant indicator for predicting poor outcome after surgery. LAT1 expression was a significant independent predictor by multivariate analysis. Both in vitro and in vivo preliminary experiments indicated that BCH significantly suppressed growth of the tumor and yielded an additive therapeutic efficacy to gemcitabine and 5-FU. CONCLUSIONS High expression of LAT1 is a promising pathological marker to predict the outcome in patients with biliary tract adenocarcinoma. Inhibition of LAT1 may be an effective targeted therapy for this distressing disease.
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Abstract
During tumor progression cells acquire an altered metabolism, either as a cause or as a consequence of an increased need of energy and nutrients. All four major classes of macromolecules are affected: carbohydrates, proteins, lipids and nucleic acids. As a result of the changed needs, solute carriers (SLCs) which are the major transporters of these molecules are differently expressed. This renders them important targets in the treatment of cancer. Blocking or activating SLCs is one possible therapeutic strategy. For example, some SLCs are upregulated in tumor cells due to the increased demand for energy and nutritional needs. Thus, blocking them and turning off the delivery of fuel or nutrients could be one way to interfere with tumor progression. Specific drug delivery to cancer cells via transporters is another approach. Some SLCs are also interesting as chemosensitizing targets because blocking or activating them may result in an altered response to chemotherapy. In this review we summarize the roles of SLCs in cancer therapy and specifically their potential as direct or indirect targets, as drug carriers or as chemosensitizing targets.
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Affiliation(s)
- Sara El-Gebali
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
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Ohtsuki S, Ikeda C, Uchida Y, Sakamoto Y, Miller F, Glacial F, Decleves X, Scherrmann JM, Couraud PO, Kubo Y, Tachikawa M, Terasaki T. Quantitative targeted absolute proteomic analysis of transporters, receptors and junction proteins for validation of human cerebral microvascular endothelial cell line hCMEC/D3 as a human blood-brain barrier model. Mol Pharm 2012; 10:289-96. [PMID: 23137377 DOI: 10.1021/mp3004308] [Citation(s) in RCA: 165] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Human cerebral microvascular endothelial cell line hCMEC/D3 is an established model of the human blood-brain barrier (BBB). The purpose of the present study was to determine, by means of quantitative targeted absolute proteomics, the protein expression levels in hCMEC/D3 cells of multiple transporters, receptors and junction proteins for comparison with our previously reported findings in isolated human brain microvessels. Among 91 target molecules, 12 transporters, 2 receptors, 1 junction protein and 1 membrane marker were present at quantifiable levels in plasma membrane fraction of hCMEC/D3 cells. ABCA2, MDR1, MRP4, BCRP, GLUT1, 4F2hc, MCT1, ENT1, transferrin and insulin receptors and claudin-5 were detected in both hCMEC/D3 cells and human brain microvessels. After normalization based on Na(+)/K(+) ATPase expression, the differences in protein expression levels between hCMEC/D3 cells and human brain microvessels were within 4-fold for these proteins, with the exceptions of ENT1, transferrin receptor and claudin-5. ABCA8, LAT1, LRP1 and γ-GTP were below the limit of quantification in the cells, but were found in human brain microvessels. ABCA3, ABCA6, MRP1 and ATA1 were found only in hCMEC/D3 cells. Furthermore, compared with human umbilical vein endothelial cells (HUVECs) as reference nonbrain endothelial cells, MDR1 was found only in hCMEC/D3 cells, and GLUT1 expression was 15-fold higher in hCMEC/D3 cells than in HUVECs. In conclusion, this is the first study to examine the suitability and limitations of the hCMEC/D3 cell line as a BBB functional model in terms of quantitative expression levels of transporters, receptors and tight junction proteins.
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Affiliation(s)
- Sumio Ohtsuki
- Division of Membrane Transport and Drug Targeting, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
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Rosario FJ, Kanai Y, Powell TL, Jansson T. Mammalian target of rapamycin signalling modulates amino acid uptake by regulating transporter cell surface abundance in primary human trophoblast cells. J Physiol 2012; 591:609-25. [PMID: 23165769 DOI: 10.1113/jphysiol.2012.238014] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Abnormal fetal growth increases the risk for perinatal complications and predisposes for the development of obesity, diabetes and cardiovascular disease later in life. Emerging evidence suggests that changes in placental amino acid transport directly contribute to altered fetal growth. However, the molecular mechanisms regulating placental amino acid transport are largely unknown. Here we combined small interfering (si) RNA-mediated silencing approaches with protein expression/localization and functional studies in cultured primary human trophoblast cells to test the hypothesis that mammalian target of rapamycin complex 1 (mTORC1) and 2 (mTORC2) regulate amino acid transporters by post-translational mechanisms. Silencing raptor (inhibits mTORC1) or rictor (inhibits mTORC2) markedly decreased basal System A and System L amino acid transport activity but had no effect on growth factor-stimulated amino acid uptake. Simultaneous inhibition of mTORC1 and 2 completely inhibited both basal and growth factor-stimulated amino acid transport activity. In contrast, mTOR inhibition had no effect on serotonin transport. mTORC1 or mTORC2 silencing markedly decreased the plasma membrane expression of specific System A (SNAT2, SLC38A2) and System L (LAT1, SLC7A5) transporter isoforms without affecting global protein expression. In conclusion, mTORC1 and mTORC2 regulate human trophoblast amino acid transporters by modulating the cell surface abundance of specific transporter isoforms. This is the first report showing regulation of amino acid transport by mTORC2. Because placental mTOR activity and amino acid transport are decreased in human intrauterine growth restriction our data are consistent with the possibility that dysregulation of placental mTOR plays an important role in the development of abnormal fetal growth.
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Affiliation(s)
- Fredrick J Rosario
- Center for Pregnancy and Newborn Research, Department of Obstetrics and Gynecology, University of Texas Health Science Center San Antonio, Mail Code 7836, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
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Dickinson JM, Drummond MJ, Coben JR, Volpi E, Rasmussen BB. Aging differentially affects human skeletal muscle amino acid transporter expression when essential amino acids are ingested after exercise. Clin Nutr 2012; 32:273-80. [PMID: 22889597 DOI: 10.1016/j.clnu.2012.07.009] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 07/13/2012] [Accepted: 07/24/2012] [Indexed: 01/17/2023]
Abstract
BACKGROUND & AIMS Amino acid transporters have been proposed as regulators of protein synthesis. The primary aim of this study was to determine whether amino acid transporter expression is increased in human muscle following resistance exercise (RE) coupled with essential amino acid (EAA) ingestion, and whether a differential response occurs with aging. Secondly, we aimed to compare this response to a previous study examining RE alone. METHODS Young (n = 7, 30 ± 2 yr) and older men (n = 6, 70 ± 2 yr) ingested EAA 1 h after RE. Muscle biopsies were obtained at rest and 3 and 6 h post exercise to examine amino acid transporter mRNA and protein expression. RESULTS In both age groups, RE + EAA increased mRNA of L-type amino acid transporter 1 (LAT1)/solute linked carrier (SLC)7A5, sodium-coupled neutral amino acid transporter 2 (SNAT2)/SLC38A2, and cationic amino acid transporter 1/SLC7A1 (p < 0.05). SNAT2 protein increased in young at 3 and 6 h (p < 0.05), whereas old maintained higher LAT1 protein (p < 0.05). Compared to RE alone, RE + EAA enhanced amino acid transporter expression only in young (p < 0.05). CONCLUSIONS RE increases muscle amino acid transporter expression in young and older adults, however, post exercise EAA ingestion enhances amino acid transporter expression only in young indicating that aging may influence the function of specific amino acid transporters.
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Affiliation(s)
- Jared M Dickinson
- Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, TX 77555, United States.
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Pasiakos SM. Exercise and amino acid anabolic cell signaling and the regulation of skeletal muscle mass. Nutrients 2012; 4:740-58. [PMID: 22852061 DOI: 10.3390/nu4070740] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 06/29/2012] [Accepted: 07/02/2012] [Indexed: 12/21/2022] Open
Abstract
A series of complex intracellular networks influence the regulation of skeletal muscle protein turnover. In recent years, studies have examined how cellular regulators of muscle protein turnover modulate metabolic mechanisms contributing to the loss, gain, or conservation of skeletal muscle mass. Exercise and amino acids both stimulate anabolic signaling potentially through several intracellular pathways including the mammalian target of rapamycin complex 1 and the mitogen activated protein kinase cell signaling cascades. As novel molecular regulators of muscle integrity continue to be explored, a contemporary analysis of the literature is required to understand the metabolic mechanisms by which contractile forces and amino acids affect cellular process that contribute to long-term adaptations and preservation of muscle mass. This article reviews the literature related to how exercise and amino acid availability affect cellular regulators of skeletal muscle mass, especially highlighting recent investigations that have identified mechanisms by which contractile forces and amino acids modulate muscle health. Furthermore, this review will explore integrated exercise and nutrition strategies that promote the maintenance of muscle health by optimizing exercise, and amino acid-induced cell signaling in aging adults susceptible to muscle loss.
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Abstract
Amino acid availability is a rate-limiting factor in the regulation of protein synthesis. When amino acid supplies become restricted, mammalian cells employ homeostatic mechanisms to rapidly inhibit processes such as protein synthesis, which demands high levels of amino acids. Muscle cells in particular are subject to high protein turnover rates to maintain amino acid homeostasis. Mammalian target of rapamycin complex 1 (mTORC1) is an evolutionary conserved multiprotein complex that coordinates a network of signaling cascades and functions as a key mediator of protein translation, gene transcription, and autophagy. Signal transduction through mTORC1, which is centrally involved in muscle growth through enhanced protein translation, is governed by intracellular amino acid supply. The branched-chain amino acid leucine is critical for muscle growth and acts in part through activation of mTORC1. Recent research has revealed that mTORC1 signaling is coordinated primarily at the lysosomal membranes. This discovery has sparked a wealth of research in this field, revealing several different signaling molecules involved in transducing the amino acid signal to mTORC1, including the Rag GTPases, MAP4K3, and Vps34/ULK1. This review evaluates the current knowledge regarding cellular mechanisms that control and sense the intracellular amino acid pool. We discuss the role of leucine and mTORC1 in the regulation of amino acid transport via the system L and system A transporters such as LAT1 and SNAT2, as well as protein degradation via autophagic and proteasomal pathways. We also describe the complexities of energy homeostasis via AMPK and cell receptor-mediated growth signals that also converge on mTORC1. Leucine is a particularly potent regulator of protein turnover, to the extent where leucine stimulation alone is sufficient to stimulate mTORC1 signal transduction. The significance of leucine in this context is not yet known; however, recent advancements in this area will also be covered within this review.
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Affiliation(s)
- Kayleigh M Dodd
- Institute of Medical Genetics, Cardiff University, Heath Park, Cardiff, Wales, UK
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Suryawan A, Nguyen HV, Almonaci RD, Davis TA. Abundance of amino acid transporters involved in mTORC1 activation in skeletal muscle of neonatal pigs is developmentally regulated. Amino Acids 2013; 45:523-30. [PMID: 22643846 DOI: 10.1007/s00726-012-1326-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 05/15/2012] [Indexed: 01/22/2023]
Abstract
Previously we demonstrated that the insulin- and amino acid-induced activation of the mammalian target of rapamycin complex 1 (mTORC1) is developmentally regulated in neonatal pigs. Recent studies have indicated that members of the System A transporter (SNAT2), the System N transporter (SNAT3), the System L transporters (LAT1 and LAT2), and the proton-assisted amino acid transporters (PAT1 and PAT2) have crucial roles in the activation of mTORC1 and that the abundance of amino acid transporters is positively correlated with their activation. This study aimed to determine the effect of the post-prandial rise in insulin and amino acids on the abundance or activation of SNAT2, SNAT3, LAT1, LAT2, PAT1, and PAT2 and whether the response is modified by development. Overnight fasted 6- and 26-day-old pigs were infused for 2 h with saline (Control) or with insulin or amino acids to achieve fed levels while amino acids or insulin, respectively, as well as glucose were maintained at fasting levels. The abundance of SNAT2, SNAT3, LAT1, LAT2, PAT1, and PAT2 was higher in muscle of 6- compared with 26-day-old pigs. The abundance of the PAT2-mTOR complex was greater in 6- than in 26-day-old pigs, consistent with the higher activation of mTORC1. Neither insulin nor amino acids altered amino acid transporter or PAT2-mTOR complex abundance. In conclusion, the amino acid transporters, SNAT 2/3, LAT 1/2, and PAT1/2, likely have important roles in the enhanced amino acid-induced activation of mTORC1 in skeletal muscle of the neonate.
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Valdovinos-Flores C, Gonsebatt ME. The role of amino acid transporters in GSH synthesis in the blood-brain barrier and central nervous system. Neurochem Int 2012; 61:405-14. [PMID: 22634224 DOI: 10.1016/j.neuint.2012.05.019] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 04/17/2012] [Accepted: 05/15/2012] [Indexed: 12/22/2022]
Abstract
Glutathione (GSH) plays a critical role in protecting cells from oxidative stress and xenobiotics, as well as maintaining the thiol redox state, most notably in the central nervous system (CNS). GSH concentration and synthesis are highly regulated within the CNS and are limited by availability of the sulfhydryl amino acid (AA) l-cys, which is mainly transported from the blood, through the blood-brain barrier (BBB), and into neurons. Several antiporter transport systems (e.g., x(c)(-), x(-)(AG), and L) with clearly different luminal and abluminal distribution, Na(+), and pH dependency have been described in brain endothelial cells (BEC) of the BBB, as well as in neurons, astrocytes, microglia and oligodendrocytes from different brain structures. The purpose of this review is to summarize information regarding the different AA transport systems for l-cys and its oxidized form l-cys(2) in the CNS, such as expression and activity in blood-brain barrier endothelial cells, astrocytes and neurons and environmental factors that modulate transport kinetics.
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Benner J, Daniel H, Spanier B. A glutathione peroxidase, intracellular peptidases and the TOR complexes regulate peptide transporter PEPT-1 in C. elegans. PLoS One 2011; 6:e25624. [PMID: 21980510 PMCID: PMC3182239 DOI: 10.1371/journal.pone.0025624] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 09/08/2011] [Indexed: 11/18/2022] Open
Abstract
The intestinal peptide transporter PEPT-1 in Caenorhabditis elegans is a rheogenic H+-dependent carrier responsible for the absorption of di- and tripeptides. Transporter-deficient pept-1(lg601) worms are characterized by impairments in growth, development and reproduction and develop a severe obesity like phenotype. The transport function of PEPT-1 as well as the influx of free fatty acids was shown to be dependent on the membrane potential and on the intracellular pH homeostasis, both of which are regulated by the sodium-proton exchanger NHX-2. Since many membrane proteins commonly function as complexes, there could be proteins that possibly modulate PEPT-1 expression and function. A systematic RNAi screening of 162 genes that are exclusively expressed in the intestine combined with a functional transport assay revealed four genes with homologues existing in mammals as predicted PEPT-1 modulators. While silencing of a glutathione peroxidase surprisingly caused an increase in PEPT-1 transport function, silencing of the ER to Golgi cargo transport protein and of two cytosolic peptidases reduced PEPT-1 transport activity and this even corresponded with lower PEPT-1 protein levels. These modifications of PEPT-1 function by gene silencing of homologous genes were also found to be conserved in the human epithelial cell line Caco-2/TC7 cells. Peptidase inhibition, amino acid supplementation and RNAi silencing of targets of rapamycin (TOR) components in C. elegans supports evidence that intracellular peptide hydrolysis and amino acid concentration are a part of a sensing system that controls PEPT-1 expression and function and that involves the TOR complexes TORC1 and TORC2.
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Affiliation(s)
- Jacqueline Benner
- ZIEL Research Center of Nutrition and Food Sciences, Abteilung Biochemie, Technische Universität München, Freising, Germany
| | - Hannelore Daniel
- ZIEL Research Center of Nutrition and Food Sciences, Abteilung Biochemie, Technische Universität München, Freising, Germany
| | - Britta Spanier
- ZIEL Research Center of Nutrition and Food Sciences, Abteilung Biochemie, Technische Universität München, Freising, Germany
- * E-mail:
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Nakanishi T, Tamai I. Solute Carrier Transporters as Targets for Drug Delivery and Pharmacological Intervention for Chemotherapy. J Pharm Sci 2011; 100:3731-50. [DOI: 10.1002/jps.22576] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 03/29/2011] [Accepted: 03/31/2011] [Indexed: 01/11/2023]
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Nissen-Meyer LS, Popescu MC, Hamdani el H, Chaudhry FA. Protein kinase C-mediated phosphorylation of a single serine residue on the rat glial glutamine transporter SN1 governs its membrane trafficking. J Neurosci 2011; 31:6565-75. [PMID: 21525297 DOI: 10.1523/JNEUROSCI.3694-10.2011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Molecular mechanisms involved in the replenishment of the fast neurotransmitters glutamate and GABA are poorly understood. Glutamine sustains their generation. However, glutamine formation from the recycled transmitters is confined to glial processes and requires facilitators for its translocation across the glial and neuronal membranes. Indeed, glial processes are enriched with the system N transporter SN1 (Slc38a3), which, by bidirectional transport, maintains steady extracellular glutamine levels and thereby furnishes neurons with the primary precursor for fast neurotransmitters. We now demonstrate that SN1 is phosphorylated by protein kinase Cα (PKCα) and PKCγ. Electrophysiological characterization shows that phosphorylation reduces V(max) dramatically, whereas no significant effects are seen on the K(m). Phosphorylation occurs specifically at a single serine residue (S52) in the N-terminal rat (Rattus norvegicus) SN1 and results in sequestration of the protein into intracellular reservoirs. Prolonged activation of PKC results in partial degradation of SN1. These results provide the first demonstration of phosphorylation of SN1 and regulation of its activity at the plasma membrane. Interestingly, membrane trafficking of SN1 resembles that of the glutamate transporter GLT and the glutamate-aspartate transporter GLAST: it involves the same PKC isoforms and occurs in the same glial processes. This suggests that the glutamate/GABA-glutamine cycle may be modified at two key points by similar signaling events and unmasks a prominent role for PKC-dependent phosphorylation. Our data suggest that extracellular glutamine levels may be fine-tuned by dynamic regulation of glial SN1 activity, which may impact on transmitter generation, contribute to defining quantal size, and have profound effects on synaptic plasticity.
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Deldicque L, Bertrand L, Patton A, Francaux M, Baar K. ER stress induces anabolic resistance in muscle cells through PKB-induced blockade of mTORC1. PLoS One 2011; 6:e20993. [PMID: 21698202 PMCID: PMC3116857 DOI: 10.1371/journal.pone.0020993] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 05/17/2011] [Indexed: 12/31/2022] Open
Abstract
Background Anabolic resistance is the inability to increase protein synthesis in response to an increase in amino acids following a meal. One potential mediator of anabolic resistance is endoplasmic reticulum (ER) stress. The purpose of the present study was to test whether ER stress impairs the response to growth factors and leucine in muscle cells. Methods Muscle cells were incubated overnight with tunicamycin or thapsigargin to induce ER stress and the activation of the unfolded protein response, mTORC1 activity at baseline and following insulin and amino acids, as well as amino acid transport were determined. Results ER stress decreased basal phosphorylation of PKB and S6K1 in a dose-dependent manner. In spite of the decrease in basal PKB phosphorylation, insulin (10–50 nM) could still activate both PKB and S6K1. The leucine (2.5–5 mM)-induced phosphorylation of S6K1 on the other hand was repressed by low concentrations of both tunicamycin and thapsigargin. To determine the mechanism underlying this anabolic resistance, several inhibitors of mTORC1 activation were measured. Tunicamycin and thapsigargin did not change the phosphorylation or content of either AMPK or JNK, both increased TRB3 mRNA expression and thapsigargin increased REDD1 mRNA. Tunicamycin and thapsigargin both decreased the basal phosphorylation state of PRAS40. Neither tunicamycin nor thapsigargin prevented phosphorylation of PRAS40 by insulin. However, since PKB is not activated by amino acids, PRAS40 phosphorylation remained low following the addition of leucine. Blocking PKB using a specific inhibitor had the same effect on both PRAS40 and leucine-induced phosphorylation of S6K1. Conclusion ER stress induces anabolic resistance in muscle cells through a PKB/PRAS40-induced blockade of mTORC1.
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Affiliation(s)
- Louise Deldicque
- Université catholique de Louvain, Institute of Neuroscience, Research Group in Muscle and Exercise Physiology, Louvain-la-Neuve, Belgium
- Research Centre for Exercise and Health, Department of Biomedical Kinesiology, K.U. Leuven, Leuven, Belgium
| | - Luc Bertrand
- Université catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pole of Cardiovascular Research, Woluwe-Saint-Lambert, Belgium
| | - Amy Patton
- Department of Neurobiology, Physiology and Behaviour, University of California Davis, Davis, California, United States of America
| | - Marc Francaux
- Université catholique de Louvain, Institute of Neuroscience, Research Group in Muscle and Exercise Physiology, Louvain-la-Neuve, Belgium
| | - Keith Baar
- Department of Neurobiology, Physiology and Behaviour, University of California Davis, Davis, California, United States of America
- * E-mail:
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Miko E, Margitai Z, Czimmerer Z, Várkonyi I, Dezso B, Lányi A, Bacsó Z, Scholtz B. miR-126 inhibits proliferation of small cell lung cancer cells by targeting SLC7A5. FEBS Lett 2011; 585:1191-6. [PMID: 21439283 DOI: 10.1016/j.febslet.2011.03.039] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2010] [Revised: 03/16/2011] [Accepted: 03/16/2011] [Indexed: 11/19/2022]
Abstract
Despite intensive efforts to improve therapies, small cell lung cancer (SCLC) still has a dismal median survival of 18 months. Since miR-126 is under-expressed in the majority of SCLC tumors, we investigated the effect of miR-126 overexpression on the proliferation and cell cycle distribution of H69 cells. Our results demonstrate that miR-126 inhibits proliferation of H69 cells, by delaying the cells in the G1 phase. Short interfering RNA (siRNA) mediated suppression of SLC7A5, a predicted target of mir-126, has the same effect on H69 cells. We also show for the first time that SLC7A5 is a direct target of miR-126.
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Affiliation(s)
- Edit Miko
- Dept. of Biochemistry and Molecular Biology, Clinical Genomics Center, University of Debrecen Medical and Health Science Center, Hungary
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Ohtsuki S, Yamaguchi H, Kang YS, Hori S, Terasaki T. Reduction of L-type amino acid transporter 1 mRNA expression in brain capillaries in a mouse model of Parkinson's disease. Biol Pharm Bull 2010; 33:1250-2. [PMID: 20606323 DOI: 10.1248/bpb.33.1250] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The blood-brain barrier (BBB) expresses transporters that influence both dopaminergic neuronal function and drug therapy for Parkinson's disease (PD). The purpose of the present study was to clarify changes of transporter mRNA expression at the BBB in mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as a model of PD, in order to understand the pathophysiological role of BBB transport function in PD. At 7 d after MPTP treatment, mice showed a motor deficit and a loss of dopaminergic neurons. At the same time, L-type amino acid transporter 1 (LAT1) mRNA expression in the brain capillary fraction of the MPTP-treated mice was significantly reduced by 62.6% compared with saline-treated mice, while no significant change was observed in the expression of glucose transporter 1, creatine transporter 1, taurine transporter, organic cation transporter 2, serotonin transporter, norepinephrine transporter and dopamine transporter. LAT1 mRNA expression in whole brain was not affected at 1, 3 and 5 d after the treatment, but was reduced by 46.3% at 7 d. LAT1 mediates the transport of large neutral amino acids, including tyrosine, as well as the PD-therapeutic drug levodopa, across the BBB. Our findings indicate that decreased LAT1 expression at the BBB in PD patients may adversely affect amino acid supply from the circulating blood and levodopa distribution into the brain.
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Affiliation(s)
- Sumio Ohtsuki
- Division of Membrane Transport and Drug Targeting, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan
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Liang Z, Cho HT, Williams L, Zhu A, Liang K, Huang K, Wu H, Jiang C, Hong S, Crowe R, Goodman MM, Shim H. Potential Biomarker of L-type Amino Acid Transporter 1 in Breast Cancer Progression. Nucl Med Mol Imaging 2010; 45:93-102. [PMID: 24899987 DOI: 10.1007/s13139-010-0068-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Accepted: 11/04/2010] [Indexed: 12/16/2022] Open
Abstract
PURPOSE L-type amino acid transporter 1 (LAT1) is essential for the transport of large neutral amino acids. However, its role in breast cancer growth remains largely unknown. The purpose of the study is to investigate whether LAT1 is a potential biomarker for the diagnosis and treatment of breast cancer. METHODS LAT1 mRNA and protein levels in breast cancer cell lines and tissues were analyzed. In addition, the effects of targeting LAT1 for the inhibition of breast cancer cell tumorigenesis were assessed with soft agar assay. The imaging of xenograft with anti-1-amino-3-[(18)F]fluorocyclobutane-1-carboxylic acid (anti-[(18)F]FACBC) PET was assessed for its diagnostic biomarker potential. RESULTS Normal breast tissue or low malignant cell lines expressed low levels of LAT1 mRNA and protein, while highly malignant cancer cell lines and high-grade breast cancer tissue expressed high levels of LAT1. In addition, higher expression levels of LAT1 in breast cancer tissues were consistent with advanced-stage breast cancer. Furthermore, the blockade of LAT1 with its inhibitor, 2-amino-bicyclo[2.2.1]heptane-2-carboxylic acid (BCH), or the knockdown of LAT1 with siRNA, inhibited proliferation and tumorigenesis of breast cancer cells. A leucine analog, anti-[(18)F]FACBC, has been demonstrated to be an excellent PET tracer for the non-invasive imaging of malignant breast cancer using an orthotopic animal model. CONCLUSIONS The overexpression of LAT1 is required for the progression of breast cancer. LAT1 represents a potential biomarker for therapy and diagnosis of breast cancer. Anti-[(18)F]FACBC that correlates with LAT1 function is a potential PET tracer for malignant breast tumor imaging.
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Affiliation(s)
- Zhongxing Liang
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA ; Winship Cancer Institute, Emory University School of Medicine, Atlanta, USA
| | - Heidi T Cho
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA
| | - Larry Williams
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA
| | - Aizhi Zhu
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA
| | - Ke Liang
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA
| | - Ke Huang
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA
| | - Hui Wu
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA
| | - Chunsu Jiang
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA
| | - Samuel Hong
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA
| | - Ronald Crowe
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA
| | - Mark M Goodman
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA ; Winship Cancer Institute, Emory University School of Medicine, Atlanta, USA
| | - Hyunsuk Shim
- Department of Radiology, Emory University School of Medicine, 1365C Clifton Road NE, Atlanta, GA 30322 USA ; Winship Cancer Institute, Emory University School of Medicine, Atlanta, USA
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Drummond MJ, Glynn EL, Fry CS, Timmerman KL, Volpi E, Rasmussen BB. An increase in essential amino acid availability upregulates amino acid transporter expression in human skeletal muscle. Am J Physiol Endocrinol Metab 2010; 298:E1011-8. [PMID: 20304764 PMCID: PMC2867366 DOI: 10.1152/ajpendo.00690.2009] [Citation(s) in RCA: 161] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Essential amino acids (EAA) stimulate skeletal muscle mammalian target of rapamycin complex 1 (mTORC1) signaling and protein synthesis. It has recently been reported that an increase in amino acid (AA) transporter expression during anabolic conditions is rapamycin-sensitive. The purpose of this study was to determine whether an increase in EAA availability increases AA transporter expression in human skeletal muscle. Muscle biopsies were obtained from the vastus lateralis of seven young adult subjects (3 male, 4 female) before and 1-3 h after EAA ingestion (10 g). Blood and muscle samples were analyzed for leucine kinetics using stable isotopic techniques. Quantitative RT-PCR, and immunoblotting were used to determine the mRNA and protein expression, respectively, of AA transporters and members of the general AA control pathway [general control nonrepressed (GCN2), activating transcription factor (ATF4), and eukaryotic initiation factor (eIF2) alpha-subunit (Ser(52))]. EAA ingestion increased blood leucine concentration, delivery of leucine to muscle, transport of leucine from blood into muscle, intracellular muscle leucine concentration, ribosomal protein S6 (Ser(240/244)) phosphorylation, and muscle protein synthesis. This was followed with increased L-type AA transporter (LAT1), CD98, sodium-coupled neutral AA transporter (SNAT2), and proton-coupled amino acid transporter (PAT1) mRNA expression at 1 h (P < 0.05) and modest increases in LAT1 protein expression (3 h post-EAA) and SNAT2 protein expression (2 and 3 h post-EAA, P < 0.05). Although there were no changes in GCN2 expression and eIF2 alpha phosphorylation, ATF4 protein expression reached significance by 2 h post-EAA (P < 0.05). We conclude that an increase in EAA availability upregulates human skeletal muscle AA transporter expression, perhaps in an mTORC1-dependent manner, which may be an adaptive response necessary for improved AA intracellular delivery.
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Affiliation(s)
- Micah J Drummond
- University of Texas Medical Branch, Department of Physical Therapy, Division of Rehabilitation Sciences, Sealy Center on Aging, 301 Univ. Blvd., Galveston, TX 77555-1144, USA
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Chrostowski MK, McGonnigal BG, Stabila JP, Padbury JF. Role of the L-amino acid transporter-1 (LAT-1) in mouse trophoblast cell invasion. Placenta 2010; 31:528-34. [PMID: 20421131 DOI: 10.1016/j.placenta.2009.12.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2009] [Revised: 12/06/2009] [Accepted: 12/08/2009] [Indexed: 11/15/2022]
Abstract
LAT-1 (L-type amino acid transporter 1) is a system L, Na(+)-independent amino acid transporter responsible for transport of large neutral amino acids. Dysregulated expression of LAT-1 is characteristic of many primary human cancers and it's over expression is related to tumor invasion. LAT-1 is highly expressed in the trophoblast giant cells (TGCs) at the time of implantation. Since trophoblast giant cells are highly invasive during the process of endometrial implantation and placentation, LAT-1 may play a role in the invasive phenotype. Our objectives were to identify the effects of increased and decreased LAT-1 expression on mouse trophoblast invasion. We therefore examined the role of amino acid deprivation, pharmacologic blockade specific to leucine transport and gene silencing (siRNA) on LAT-1 expression and trophoblast cell invasion. We utilized mouse primary trophoblast stem (TS) cells. LAT-1 mRNA expression was quantified by real time qPCR, protein by Western blotting and cell invasion was measured in Transwell plates through Matrigel. Amino acid transport using uptake of tritiated leucine. Under limited leucine availability and/or pharmacologic blockage, LAT-1 gene expression was significantly increased, p<0.05. This was associated with a 3-fold increase in cell invasion, p<0.05. In contrast, following siRNA-mediated gene silencing decreased LAT-1 expression (both mRNA and protein) was associated with decreased cell invasion and decreased leucine uptake, p<0.05. Upregulation of LAT-1 gene expression via limited amino acid availability or following pharmacologic blockade of transport leads to an increase in mouse trophoblast stem cell invasiveness. Downregulation of LAT-1 expression via genetic silencing leads to inhibition of invasiveness. These results demonstrate that LAT-1 plays an important role in trophoblast invasion.
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Affiliation(s)
- M K Chrostowski
- Division of Biology and Medicine, Graduate Program in Pathobiology, Brown University, Providence, Rhode Island, USA
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Abstract
Activation of vascular smooth muscle cells (VSMCs) to migrate and proliferate is essential for the formation of intimal hyperplasia. Hence, selectively targeting activated VSMCs is a potential strategy against vaso-occlusive disorders such as in-stent restenosis, vein-graft stenosis, and transplant vasculopathy. We show that CD98 heavy chain (CD98hc) is markedly up-regulated in neointimal and cultured VSMCs, and that activated but not quiescent VSMCs require CD98hc for survival. CD98hc mediates integrin signaling and localizes amino acid transporters to the plasma membrane. SMC-specific deletion of CD98hc did not affect normal vessel morphology, indicating that CD98hc was not required for the maintenance of resident quiescent VSMCs; however, CD98hc deletion reduced intimal hyperplasia after arterial injury. Ex vivo and in vitro, loss of CD98hc suppressed proliferation and induced apoptosis in VSMCs. Furthermore, reconstitution with CD98hc mutants showed that CD98hc interaction with integrins was necessary for the survival of VSMCs. These studies establish the importance of CD98hc in VSMC proliferation and survival. Furthermore, loss of CD98hc was selectively deleterious to activated VSMCs while sparing resident quiescent VSMCs, suggesting that activated VSMCs are physiologically dependent on CD98hc, and hence, CD98hc is a potential therapeutic target in vaso-occlusive disorders.
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Affiliation(s)
- Per Fogelstrand
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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Baird FE, Bett KJ, MacLean C, Tee AR, Hundal HS, Taylor PM. Tertiary active transport of amino acids reconstituted by coexpression of System A and L transporters in Xenopus oocytes. Am J Physiol Endocrinol Metab 2009; 297:E822-9. [PMID: 19622785 DOI: 10.1152/ajpendo.00330.2009] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The System L transporter facilitates cellular import of large neutral amino acids (AAs) such as Leu, a potent activator of the intracellular target of rapamycin (TOR) pathway, which signals for cell growth. System L is an AA exchanger, proposed to accumulate certain AAs by coupling to dissipation of concentration gradient(s) of exchange substrates generated by secondary active AA transporters such as System A (SNAT2). We addressed the hypothesis that this type of coupling (termed tertiary active transport) acts as an indirect mechanism to extend the range of AA stimulating TOR to those transported by both Systems A and L (e.g., Gln) through downstream enhancement of Leu accumulation. System A overexpression enabled Xenopus oocytes to accumulate substrate AAs (notably Ser, Gln, Ala, Pro, Met; totaling 2.6 nmol/oocyte) from medium containing a physiological AA mixture at plasma concentrations. Net accumulation of System L (4F2hc-xLAT1) substrates from this medium by System L-overexpressing oocytes was increased by 90% (from 0.7 to 1.35 nmol/oocyte; mainly Leu, Ile) when Systems A and L were coexpressed, coincident with a decline in accumulation of specific System A substrates (Gln, Ser, Met), as expected if the latter were also System L substrates and functional coupling of the transport Systems occurred. AA flux coupling was confirmed as trans-stimulation of Leu influx in System L-expressing oocytes by Gln injection (0.5 nmol/oocyte). The observed changes in Leu accumulation are sufficient to activate the TOR pathway in oocytes, although intracellular AA metabolism limits the potential for AA accumulation by tertiary active transport in this system.
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Affiliation(s)
- Fiona E Baird
- Div. of Molecular Physiology, College of Life Sciences, Univ. of Dundee, Dundee, Scotland, UK
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Gao H, Wu G, Spencer TE, Johnson GA, Bazer FW. Select Nutrients in the Ovine Uterine Lumen. IV. Expression of Neutral and Acidic Amino Acid Transporters in Ovine Uteri and Peri-Implantation Conceptuses1. Biol Reprod 2009; 80:1196-208. [DOI: 10.1095/biolreprod.108.075440] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
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Gao H, Wu G, Spencer TE, Johnson GA, Bazer FW. Select nutrients in the ovine uterine lumen. VI. Expression of FK506-binding protein 12-rapamycin complex-associated protein 1 (FRAP1) and regulators and effectors of mTORC1 and mTORC2 complexes in ovine uteri and conceptuses. Biol Reprod 2009; 81:87-100. [PMID: 19299312 DOI: 10.1095/biolreprod.109.076257] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
FRAP1 (FK506-binding protein 12-rapamycin complex-associated protein 1), a component of the nutrient-sensing cell signaling pathway, is critical for cell growth and metabolism. The present study determined expression of FRAP1 and associated members of the mTORC1 and mTORC2 cell signaling pathways in uteri of cyclic and pregnant ewes and conceptuses, as well as effects of pregnancy, progesterone (P4), and interferon tau (IFNT) on their expression. The mRNAs for FRAP1, LST8, MAPKAP1, RAPTOR, RICTOR, TSC1, TSC2, RHEB, and EIF4EBP1 were localized to luminal, superficial glandular, and glandular epithelia and stromal cells of uteri from cyclic and pregnant ewes, as well as trophectoderm and endoderm of conceptuses between Days 13 and 18 of pregnancy. The abundance of FRAP1, RAPTOR, RICTOR, TSC1, and TSC2 mRNAs in endometria was unaffected by pregnancy status or by day of the estrous cycle or pregnancy; however, levels of LST8, MAPKAP1, RHEB, and EIF4EBP1 mRNA increased in endometria during early pregnancy. In ovariectomized ewes, P4 and IFNT stimulated expression of RHEB and EIF4EBP1 in uterine endometria. Total endometrial FRAP1 protein and phosphorylated FRAP1 protein levels were affected by pregnancy status and by day after onset of estrus, and phosphorylated FRAP1 protein was detected in nuclei of uterine epithelia and conceptuses. In endometria of pregnant ewes, increases in abundance of mRNAs for RICTOR, RHEB, and EIF4EBP1, as well as RHEB protein, correlated with rapid conceptus growth and development during the peri-implantation period. These results suggest that the FRAP1 cell signaling pathway mediates interactions between the maternal uterus and peri-implantation conceptuses and that P4 and IFNT affect this pathway by regulating expression of RHEB and EIF4EBP1.
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Affiliation(s)
- Haijun Gao
- Center for Animal Biotechnology and Genomics, Texas A&M University, College Station, Texas 77843-2471, USA
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Nicklin P, Bergman P, Zhang B, Triantafellow E, Wang H, Nyfeler B, Yang H, Hild M, Kung C, Wilson C, Myer VE, MacKeigan JP, Porter JA, Wang YK, Cantley LC, Finan PM, Murphy LO. Bidirectional transport of amino acids regulates mTOR and autophagy. Cell 2009; 136:521-34. [PMID: 19203585 DOI: 10.1016/j.cell.2008.11.044] [Citation(s) in RCA: 1285] [Impact Index Per Article: 85.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Revised: 10/04/2008] [Accepted: 11/21/2008] [Indexed: 01/08/2023]
Abstract
Amino acids are required for activation of the mammalian target of rapamycin (mTOR) kinase which regulates protein translation, cell growth, and autophagy. Cell surface transporters that allow amino acids to enter the cell and signal to mTOR are unknown. We show that cellular uptake of L-glutamine and its subsequent rapid efflux in the presence of essential amino acids (EAA) is the rate-limiting step that activates mTOR. L-glutamine uptake is regulated by SLC1A5 and loss of SLC1A5 function inhibits cell growth and activates autophagy. The molecular basis for L-glutamine sensitivity is due to SLC7A5/SLC3A2, a bidirectional transporter that regulates the simultaneous efflux of L-glutamine out of cells and transport of L-leucine/EAA into cells. Certain tumor cell lines with high basal cellular levels of L-glutamine bypass the need for L-glutamine uptake and are primed for mTOR activation. Thus, L-glutamine flux regulates mTOR, translation and autophagy to coordinate cell growth and proliferation.
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Affiliation(s)
- Paul Nicklin
- Respiratory Diseases Area, Novartis Institutes for BioMedical Research, Novartis Horsham Research Centre, West Sussex, UK
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Abstract
Nutrient signalling by the mTOR (mammalian target of rapamycin) pathway involves upstream sensing of free AA (amino acid) concentrations. Several AA-regulated kinases have recently been identified as putative intracellular AA sensors. Their activity will reflect the balance between AA flows through underlying mechanisms which together determine the size of the intracellular free AA pool. For indispensable AAs, these mechanisms are primarily (i) AA transport across the cell membrane, and (ii) protein synthesis/breakdown. The System L AA transporter is the primary conduit for cellular entry of indispensable neutral AAs (including leucine and phenylalanine) and potentially a key modulator of AA-sensitive mTOR signalling. Coupling of substrate flows through System L and other AA transporters (e.g. System A) may extend the scope for sensing nutrient abundance. Factors influencing AA transporter activity (e.g. hormones) may affect intracellular AA concentrations and hence indirectly mTOR pathway activity. Several AA transporters are themselves regulated by AA availability through 'adaptive regulation', which may help to adjust the gain of AA sensing. The substrate-binding sites of AA transporters are potentially direct sensors of AA availability at both faces of the cell surface, and there is growing evidence that AA transporters of the SNAT (sodium-coupled neutral AA transporter) and PAT (proton-assisted AA transporter) families may operate, at least under some circumstances, as transporter-like sensors (or 'transceptors') upstream of mTOR.
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Abstract
The mTOR (mammalian target of rapamycin) signalling pathway functions as a nutrient sensor, both in individual cells and, more globally, in organs such as the fat body in Drosophila and the hypothalamus in the rat. The activity of placental amino acid transporters is decreased in IUGR (intrauterine growth restriction), and recent experimental evidence suggests that these changes contribute directly to the restricted fetal growth. We have shown that mTOR regulates the activity of the placental L-type amino acid transporter system and that placental mTOR activity is decreased in IUGR. The present review summarizes the emerging evidence implicating placental mTOR signalling as a key mechanism linking maternal nutrient and growth factor concentrations to amino acid transport in the human placenta. Since fetal growth is critically dependent on placental nutrient transport, placental mTOR signalling plays an important role in the regulation of fetal growth.
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Roos S, Kanai Y, Prasad PD, Powell TL, Jansson T. Regulation of placental amino acid transporter activity by mammalian target of rapamycin. Am J Physiol Cell Physiol 2009; 296:C142-50. [DOI: 10.1152/ajpcell.00330.2008] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The activity of placental amino acid transporters is decreased in intrauterine growth restriction (IUGR), but the underlying regulatory mechanisms have not been established. Inhibition of the mammalian target of rapamycin (mTOR) signaling pathway has been shown to decrease the activity of the system L amino acid transporter in human placental villous fragments, and placental mTOR activity is decreased in IUGR. In the present study, we used cultured primary trophoblast cells to study mTOR regulation of placental amino acid transporters in more detail and to test the hypothesis that mTOR alters amino acid transport activity by changes in transporter expression. Inhibition of mTOR by rapamycin significantly reduced the activity of system A (−17%), system L (−28%), and taurine (−40%) amino acid transporters. mRNA expression of isoforms of the three amino acid transporter systems in response to mTOR inhibition was measured using quantitative real-time PCR. mRNA expression of l-type amino acid transporter 1 (LAT1; a system L isoform) and taurine transporter was reduced by 13% and 50%, respectively; however, mTOR inhibition did not alter the mRNA expression of system A isoforms (sodium-coupled neutral amino acid transporter-1, -2, and -4), LAT2, or 4F2hc. Rapamycin treatment did not significantly affect the protein expression of any of the transporter isoforms. We conclude that mTOR signaling regulates the activity of key placental amino acid transporters and that this effect is not due to a decrease in total protein expression. These data suggest that mTOR regulates placental amino acid transporters by posttranslational modifications or by affecting transporter translocation to the plasma membrane.
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Kobayashi K, Ohnishi A, Promsuk J, Shimizu S, Kanai Y, Shiokawa Y, Nagane M. Enhanced tumor growth elicited by L-type amino acid transporter 1 in human malignant glioma cells. Neurosurgery 2008; 62:493-503; discussion 503-4. [PMID: 18382329 DOI: 10.1227/01.neu.0000316018.51292.19] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
OBJECTIVE To study the expression and function of L-type amino acid transporter 1 (LAT1), a major catalytic subunit of system L that is responsible for the transport of large neutral amino acids, including most essential amino acids, in concert with the covalently bound 4F2 heavy chain, and is implicated in tumorigenesis. METHODS Human glioma cell lines and tumor specimens were analyzed for LAT1 expression using Western blotting and reverse transcription polymerase chain reaction analysis. The rate of neutral amino acid uptake was measured using L-[C]leucine. The proliferation and apoptosis rates were analyzed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide and terminal deoxynucleotidyl transferase-mediated nick end-labeling assays, respectively, on inhibition of system L by 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid. The effects on proliferation and tumor growth caused by exogenously overexpressed LAT1 were similarly analyzed. RESULTS LAT1 was expressed in most human high-grade gliomas and glioma cell lines at various levels, with more ubiquitous expression of 4F2 heavy chain. Glioma cells with high LAT1 expression exhibited a marked increase in the uptake rate of L-[C]leucine. 2-Aminobicyclo-(2,2,1)-heptane-2-carboxylic acid treatment not only suppressed deoxyribonucleic acid synthesis in association with the up-regulation of the cyclin-dependent kinase inhibitor p21 but also enhanced apoptosis with caspase activation, thereby exerting both cytostatic and cytocidal effects in glioma cells with high LAT1 expression levels. Furthermore, overexpression of LAT1 in glioma cells with low endogenous LAT1 expression significantly enhanced the rates of tumor cell growth in athymic mice. CONCLUSION LAT1, the major transporter of system L, is frequently expressed at higher levels in high-grade gliomas than in low-grade gliomas and brain tissues, and it may play an important role in enhancing the rates of tumor cell proliferation and growth in vivo.
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Affiliation(s)
- Keiichi Kobayashi
- Department of Neurosurgery, Kyorin University School of Medicine, Tokyo, Japan
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