1
|
Gyawali A, Gautam S, Hyeon SJ, Ryu H, Kang YS. L-Citrulline Level and Transporter Activity Are Altered in Experimental Models of Amyotrophic Lateral Sclerosis. Mol Neurobiol 2020; 58:647-657. [PMID: 33000451 DOI: 10.1007/s12035-020-02143-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 09/22/2020] [Indexed: 01/25/2023]
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron disease caused by the death of the neurons regulating the voluntary muscles which leads to the progressive paralysis. We investigated the difference of transport function of L-citrulline in ALS disease model (NSC-34/hSOD1G93A, MT) and a control model (NSC-34/hSOD1wt, WT). The [14C]L-citrulline uptake was significantly reduced in MT cells as compared with that of control. The Michaelis-Menten constant (Km) for MT cells was 0.67 ± 0.05 mM, whereas it was 1.48 ± 0.21 mM for control. On the other hand, the Vmax values for MT and control were 10.9 ± 0.8 nmol/mg protein/min and 18.3 ± 2.9 nmol/mg protein/min, respectively. The Km and Vmax values showed the high affinity and low capacity for MT as compared with control. Moreover, the uptake of [14C]L-citrulline was significantly inhibited by 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) and harmaline which is the inhibitor of the large neutral amino acid transporter1 (LAT1) in NSC-34 cell lines. Furthermore, [14C]L-citrulline uptakes took place in Na+-independent manner. It was also inhibited by the neutral amino acids such as citrulline and phenylalanine. Likewise, L-dopa, gabapentin, and riluzole significantly inhibited the [14C]L-citrulline uptake. It shows the competitive inhibition for L-dopa in ALS cell lines. On the other hand, [14C]L-citrulline uptake in the presence of riluzole showed competitive inhibition in WT cells, whereas it was uncompetitive for MT cells. The small interfering RNA experiments showed that LAT1 is involved in the [14C]L-citrulline uptake in NSC-34 cell lines. On the other hand, in the examination of the alteration in the expression level of LAT1, it was significantly lower in MT cells as compared with that of control. Similarly, in the spinal cord of ALS, transgenic mice revealed a slight but significant decrease in LAT1 immunoreactivity in motor neurons of ALS mice compared with control. However, the LAT1 immunoreactivity in non-motor neurons and in astrocytes was relatively increased in the spinal cord gray matter of ALS mice. The experimental evidences of our results suggest that the change of transport activity of [14C]L-citrulline may be partially responsible for the pathological alteration in ALS.
Collapse
Affiliation(s)
- Asmita Gyawali
- College of Pharmacy and Drug Information Research Institute, Sookmyung Women's University, Seoul, Republic of Korea
| | - Shashi Gautam
- College of Pharmacy and Drug Information Research Institute, Sookmyung Women's University, Seoul, Republic of Korea
| | - Seung Jae Hyeon
- Laboratory for Brain Gene Regulation and Epigenetics, Center for Neuroscience, Korea Institute of Science and Technology, Seoul, 02792, Republic of Korea
| | - Hoon Ryu
- Laboratory for Brain Gene Regulation and Epigenetics, Center for Neuroscience, Korea Institute of Science and Technology, Seoul, 02792, Republic of Korea
- Boston University Alzheimer's Disease Center Department of Neurology, Boston University School of Medicine, Boston, MA, 02183, USA
| | - Young-Sook Kang
- College of Pharmacy and Drug Information Research Institute, Sookmyung Women's University, Seoul, Republic of Korea.
| |
Collapse
|
2
|
Chirino LM, Kumar S, Okumura M, Sterner DE, Mattern M, Butt TR, Kambayashi T. TAM receptors attenuate murine NK-cell responses via E3 ubiquitin ligase Cbl-b. Eur J Immunol 2020; 50:48-55. [PMID: 31531847 PMCID: PMC7769591 DOI: 10.1002/eji.201948204] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/24/2019] [Accepted: 09/16/2019] [Indexed: 01/22/2023]
Abstract
TAM receptors (Tyro3, Axl, and Mer) are receptor tyrosine kinases (RTKs) that are expressed by multiple immune cells including NK cells. Although RTKs typically enhance cellular functions, TAM receptor ligation blocks NK-cell activation. The mechanisms by which RTKs block NK-cell signaling downstream of activating receptors are unknown. In this report, we demonstrate that TAM receptors attenuate NK cell responses via the activity of E3 ubiquitin ligase Casitas B lineage lymphoma b (Cbl-b). Specifically, we show that Tyro3, Axl, and Mer phosphorylate Cbl-b, and Tyro3 ligation activates Cbl-b by phosphorylating tyrosine residues 133 and 363. Ligation of TAM receptors by their ligand Gas6 suppresses activating receptor-stimulated NK-cell functions such as IFN-γ production and degranulation, in a TAM receptor kinase- and Cbl-b-dependent manner. Moreover, Gas6 ligation induces the degradation of LAT1, a transmembrane adaptor protein required for NK cell activating receptor signaling, in WT but not in Cbl-b knock-out NK cells. Together, these results suggest that TAM receptors may attenuate NK-cell function by phosphorylating Cbl-b, which in turn dampens NK-cell activation signaling by promoting the degradation of LAT1. Our data therefore support a mechanism by which RTKs attenuate, rather than stimulate, signaling pathways via the activation of ubiquitin ligases.
Collapse
Affiliation(s)
- Leilani M. Chirino
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104
| | | | - Mariko Okumura
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104
| | | | | | | | - Taku Kambayashi
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104
| |
Collapse
|
3
|
Beaumatin F, O'Prey J, Barthet VJA, Zunino B, Parvy JP, Bachmann AM, O'Prey M, Kania E, Gonzalez PS, Macintosh R, Lao LY, Nixon C, Lopez J, Long JS, Tait SWG, Ryan KM. mTORC1 Activation Requires DRAM-1 by Facilitating Lysosomal Amino Acid Efflux. Mol Cell 2019; 76:163-176.e8. [PMID: 31492633 PMCID: PMC6892261 DOI: 10.1016/j.molcel.2019.07.021] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 05/15/2019] [Accepted: 07/15/2019] [Indexed: 02/06/2023]
Abstract
Sensing nutrient availability is essential for appropriate cellular growth, and mTORC1 is a major regulator of this process. Mechanisms causing mTORC1 activation are, however, complex and diverse. We report here an additional important step in the activation of mTORC1, which regulates the efflux of amino acids from lysosomes into the cytoplasm. This process requires DRAM-1, which binds the membrane carrier protein SCAMP3 and the amino acid transporters SLC1A5 and LAT1, directing them to lysosomes and permitting efficient mTORC1 activation. Consequently, we show that loss of DRAM-1 also impacts pathways regulated by mTORC1, including insulin signaling, glycemic balance, and adipocyte differentiation. Interestingly, although DRAM-1 can promote autophagy, this effect on mTORC1 is autophagy independent, and autophagy only becomes important for mTORC1 activation when DRAM-1 is deleted. These findings provide important insights into mTORC1 activation and highlight the importance of DRAM-1 in growth control, metabolic homeostasis, and differentiation.
Collapse
Affiliation(s)
- Florian Beaumatin
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Jim O'Prey
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Valentin J A Barthet
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK; Institute of Cancer Sciences, University of Glasgow, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Barbara Zunino
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Jean-Philippe Parvy
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | | | - Margaret O'Prey
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Elżbieta Kania
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Pablo Sierra Gonzalez
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK; Institute of Cancer Sciences, University of Glasgow, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Robin Macintosh
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Laurence Y Lao
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Colin Nixon
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Jonathan Lopez
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK; Institute of Cancer Sciences, University of Glasgow, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Jaclyn S Long
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Stephen W G Tait
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK; Institute of Cancer Sciences, University of Glasgow, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Kevin M Ryan
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK; Institute of Cancer Sciences, University of Glasgow, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK.
| |
Collapse
|
4
|
Abstract
Tissue-specific genes are believed to be good drug targets due to improved safety. Here we show that this intuitive notion is not reflected in phase 1 and 2 clinical trials, despite the historic success of tissue-specific targets and their 2.3-fold overrepresentation among targets of marketed non-oncology drugs. We compare properties of tissue-specific genes and drug targets. We show that tissue-specificity of the target may also be related to efficacy of the drug. The relationship may be indirect (enrichment in Mendelian disease and PTVesc genes) or direct (elevated betweenness centrality scores for tissue-specifically produced enzymes and secreted proteins). Reduced evolutionary conservation of tissue-specific genes may represent a bottleneck for drug projects, prompting development of novel models with smaller evolutionary gap to humans. We show that the opportunities to identify tissue-specific drug targets are not exhausted and discuss potential use cases for tissue-specific genes in drug research.
Collapse
Affiliation(s)
- Maria Ryaboshapkina
- Translational Science, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden.
| | - Mårten Hammar
- Translational Science, Cardiovascular, Renal and Metabolism, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| |
Collapse
|
5
|
Yue M, Jiang J, Gao P, Liu H, Qing G. Oncogenic MYC Activates a Feedforward Regulatory Loop Promoting Essential Amino Acid Metabolism and Tumorigenesis. Cell Rep 2019; 21:3819-3832. [PMID: 29281830 DOI: 10.1016/j.celrep.2017.12.002] [Citation(s) in RCA: 134] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 10/24/2017] [Accepted: 11/30/2017] [Indexed: 12/18/2022] Open
Abstract
Most tumor cells exhibit obligatory demands for essential amino acids (EAAs), but the regulatory mechanisms whereby tumor cells take up EAAs and EAAs promote malignant transformation remain to be determined. Here, we show that oncogenic MYC, solute carrier family (SLC) 7 member 5 (SLC7A5), and SLC43A1 constitute a feedforward activation loop to promote EAA transport and tumorigenesis. MYC selectively activates Slc7a5 and Slc43a1 transcription through direct binding to specific E box elements within both genes, enabling effective EAA import. Elevated EAAs, in turn, stimulate Myc mRNA translation, in part through attenuation of the GCN2-eIF2α-ATF4 amino acid stress response pathway, leading to MYC-dependent transcriptional amplification. SLC7A5/SLC43A1 depletion inhibits MYC expression, metabolic reprogramming, and tumor cell growth in vitro and in vivo. These findings thus reveal a MYC-SLC7A5/SLC43A1 signaling circuit that underlies EAA metabolism, MYC deregulation, and tumorigenesis.
Collapse
Affiliation(s)
- Ming Yue
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; Department of Pharmacy, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430014, China
| | - Jue Jiang
- Medical Research Institute, Wuhan University, Wuhan 430071, China
| | - Peng Gao
- Affiliated Dalian Sixth People's Hospital, Dalian Medical University, Dalian 116031, China
| | - Hudan Liu
- Medical Research Institute, Wuhan University, Wuhan 430071, China; Zhongnan Hospital of Wuhan University, Wuhan 430071, China.
| | - Guoliang Qing
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; Medical Research Institute, Wuhan University, Wuhan 430071, China; Zhongnan Hospital of Wuhan University, Wuhan 430071, China.
| |
Collapse
|
6
|
Wei ZY, Feng MM, Yang B, Yan ZY, Wang BQ, Bu XY. Methylmercury-l-Cysteine targeting L-type amino acid transporter conjugate cytotoxicity on C6 glioma cells. J BIOL REG HOMEOS AG 2018; 32:147-151. [PMID: 29504379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Glioma is the most common primary tumor in the brain, accounting for about 40~50% of intracranial primary tumors. Most chemotherapeutic drugs have difficulty in penetrating the blood-brain barrier, and their clinical applications are greatly limited. We evaluated the effects of methylmercury-L-cysteine (MeHg-L-cys) and methylmercury chloride (MMC) on apoptosis of C6 glioma cells. L-type amino acid transporter (LAT1) was used to investigate the targeted transport function and cytotoxicity of MeHg- L-cys in glioma. MeHg-L-cys enhanced the ability of targeting glioma cells and reduced the adverse reactions to normal brain tissues. Therefore, it is significantly important to develop new anti-glioma drugs targeting the blood-brain barrier.
Collapse
Affiliation(s)
- Z Y Wei
- Department of Neurosurgery, The No.371 Central Hospital of the Peoples Liberation Army, Xinxiang, China
| | - M M Feng
- Department of Neurosurgery, Henan Provincial Peoples Hospital, The Peoples Hospital of Zhengzhou University, The Peoples Hospital of Henan University, Zhengzhou, China
| | - B Yang
- Department of Neurosurgery, Henan Provincial Peoples Hospital, The Peoples Hospital of Zhengzhou University, The Peoples Hospital of Henan University, Zhengzhou, China
| | - Z Y Yan
- Department of Neurosurgery, Henan Provincial Peoples Hospital, The Peoples Hospital of Zhengzhou University, The Peoples Hospital of Henan University, Zhengzhou, China
| | - B Q Wang
- Department of Neurosurgery, Henan Provincial Peoples Hospital, The Peoples Hospital of Zhengzhou University, The Peoples Hospital of Henan University, Zhengzhou, China
| | - X Y Bu
- Department of Neurosurgery, Henan Provincial Peoples Hospital, The Peoples Hospital of Zhengzhou University, The Peoples Hospital of Henan University, Zhengzhou, China
| |
Collapse
|
7
|
Jiang X, Zhang Y, Yang Y, Yang J, Asico LD, Chen W, Felder RA, Armando I, Jose PA, Yang Z. Gastrin stimulates renal dopamine production by increasing the renal tubular uptake of l-DOPA. Am J Physiol Endocrinol Metab 2017; 312:E1-E10. [PMID: 27780818 PMCID: PMC5283882 DOI: 10.1152/ajpendo.00116.2016] [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] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 10/18/2016] [Accepted: 10/23/2016] [Indexed: 01/02/2023]
Abstract
Gastrin is a peptide hormone that is involved in the regulation of sodium balance and blood pressure. Dopamine, which is also involved in the regulation of sodium balance and blood pressure, directly or indirectly interacts with other blood pressure-regulating hormones, including gastrin. This study aimed to determine the mechanisms of the interaction between gastrin and dopamine and tested the hypothesis that gastrin produced in the kidney increases renal dopamine production to keep blood pressure within the normal range. We show that in human and mouse renal proximal tubule cells (hRPTCs and mRPTCs, respectively), gastrin stimulates renal dopamine production by increasing the cellular uptake of l-DOPA via the l-type amino acid transporter (LAT) at the plasma membrane. The uptake of l-DOPA in RPTCs from C57Bl/6J mice is lower than in RPTCs from normotensive humans. l-DOPA uptake in renal cortical slices is also lower in salt-sensitive C57Bl/6J than in salt-resistant BALB/c mice. The deficient renal cortical uptake of l-DOPA in C57Bl/6J mice may be due to decreased LAT-1 activity that is related to its decreased expression at the plasma membrane, relative to BALB/c mice. We also show that renal-selective silencing of Gast by the renal subcapsular injection of Gast siRNA in BALB/c mice decreases renal dopamine production and increases blood pressure. These results highlight the importance of renal gastrin in stimulating renal dopamine production, which may give a new perspective in the prevention and treatment of hypertension.
Collapse
MESH Headings
- Amino Acid Transport System y+L/drug effects
- Amino Acid Transport System y+L/metabolism
- Animals
- Blood Pressure/drug effects
- Blood Pressure/physiology
- Cells, Cultured
- Dopamine/biosynthesis
- Dopamine/urine
- Down-Regulation
- Gastrins/genetics
- Gastrins/metabolism
- Gastrins/pharmacology
- Gene Silencing
- Humans
- Immunoblotting
- Kidney/drug effects
- Kidney/metabolism
- Kidney Cortex/drug effects
- Kidney Cortex/metabolism
- Kidney Tubules, Proximal/cytology
- Kidney Tubules, Proximal/drug effects
- Kidney Tubules, Proximal/metabolism
- Levodopa/metabolism
- Male
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- RNA, Messenger/drug effects
- RNA, Messenger/metabolism
- RNA, Small Interfering
- Real-Time Polymerase Chain Reaction
- Receptor, Cholecystokinin B/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
Collapse
Affiliation(s)
- Xiaoliang Jiang
- Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences (CAMS) and Comparative Medicine Centre, Peking Union Medical, Beijing, China
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Yanrong Zhang
- Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences (CAMS) and Comparative Medicine Centre, Peking Union Medical, Beijing, China
| | - Yu Yang
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland;
- Department of Pathology, The University of Texas Medical Branch, Galveston, Texas
| | - Jian Yang
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland;
- Department of Cardiology, Daping Hospital, The Third Military Medical University and Chongqing Institute of Cardiology, Chongqing, China
| | - Laureano D Asico
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Wei Chen
- Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences (CAMS) and Comparative Medicine Centre, Peking Union Medical, Beijing, China
| | - Robin A Felder
- Department of Pathology, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Ines Armando
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Pedro A Jose
- Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
- Department of Medicine, Division of Kidney Disease and Hypertension, The George Washington University School of Medicine and Health Sciences, Washington, DC; and
- Department of Pharmacology and Physiology, The George Washington University School of Medicine and Health Sciences, Washington, DC
| | - Zhiwei Yang
- Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences (CAMS) and Comparative Medicine Centre, Peking Union Medical, Beijing, China;
| |
Collapse
|
8
|
Yang J, Tan Q, Zhu W, Chen C, Liang X, Pan L. Cloning and molecular characterization of cationic amino acid transporter y⁺LAT1 in grass carp (Ctenopharyngodon idellus). Fish Physiol Biochem 2014; 40:93-104. [PMID: 23817987 DOI: 10.1007/s10695-013-9827-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 06/18/2013] [Indexed: 06/02/2023]
Abstract
The solute carrier family 7A, member 7 gene encodes the light chain- y⁺L amino acid transporter-1 (y⁺LAT1) of the heterodimeric carrier responsible for cationic amino acid (CAA) transport across the basolateral membranes of epithelial cells in intestine and kidney. Rising attention has been given to y⁺LAT1 involved in CAA metabolic pathways and growth control. The molecular characterization and function analysis of y⁺LAT1 in grass carp (Ctenopharyngodon idellus) is currently unknown. In the present study, full-length cDNA (2,688 bp), which encodes y⁺LAT1 and contains a 5'-untranslated region (319 bp), an open reading frame (1,506 bp) and a 3'-untranslated region (863 bp), has been cloned from grass carp. Amino acid sequence of grass carp y⁺LAT1 contains 11 transmembrane domains and shows 95 %, 80 % and 75 % sequence similarity to zebra fish, amphibian and mammalian y⁺LAT1, respectively. The tissue distribution and expression regulation by fasting of y⁺LAT1 mRNA were analyzed using real-time PCR. Our results showed that y⁺LAT1 mRNA was highly expressed in midgut, foregut and spleen while weakly expressed in hindgut, kidney, gill, brain, heart, liver and muscle. Nutritional status significantly influenced y⁺LAT1 mRNA expression in fish tissues, such as down-regulation of y⁺LAT1 mRNA expression after fasting (14 days).
Collapse
Affiliation(s)
- Jixuan Yang
- Fisheries College, Huazhong Agricultural University, Wuhan, 430070, China
| | | | | | | | | | | |
Collapse
|
9
|
Tsitsiou E, Sibley CP, D’Souza SW, Catanescu O, Jacobsen DW, Glazier JD. Homocysteine is transported by the microvillous plasma membrane of human placenta. J Inherit Metab Dis 2011; 34:57-65. [PMID: 20567909 PMCID: PMC2966547 DOI: 10.1007/s10545-010-9141-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [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] [Received: 01/29/2010] [Revised: 04/01/2010] [Accepted: 05/31/2010] [Indexed: 12/18/2022]
Abstract
Elevated maternal plasma concentrations of homocysteine (Hcy) are associated with pregnancy complications and adverse neonatal outcomes. The postulate that we wish to advance here is that placental transport of Hcy, by competing with endogenous amino acids for transporter activity, may account for some of the damaging impacts of Hcy on placental metabolism and function as well as fetal development. In this article, we provide an overview of some recent studies characterising the transport mechanisms for Hcy across the microvillous plasma membrane (MVM) of the syncytiotrophoblast, the transporting epithelium of human placenta. Three Hcy transport systems have been identified, systems L, A and y(+)L. This was accomplished using a strategy of competitive inhibition to investigate the effects of Hcy on the uptake of well-characterised radiolabelled substrates for each transport system into isolated MVM vesicles. The reverse experiments were also performed, examining the effects of model substrates on [³⁵S]L-Hcy uptake. This article describes the evidence for systems L, A and y(+)L involvement in placental Hcy transport and discusses the physiological implications of these findings with respect to placental function and fetal development.
Collapse
Affiliation(s)
- Eleni Tsitsiou
- Maternal and Fetal Health Research Group, School of Biomedicine, University of Manchester, Manchester Academic Health Science Centre, St Mary’s Hospital, Oxford Road, Manchester M13 9WL, UK
| | - Colin P. Sibley
- Maternal and Fetal Health Research Group, School of Biomedicine, University of Manchester, Manchester Academic Health Science Centre, St Mary’s Hospital, Oxford Road, Manchester M13 9WL, UK
| | - Stephen W. D’Souza
- Maternal and Fetal Health Research Group, School of Biomedicine, University of Manchester, Manchester Academic Health Science Centre, St Mary’s Hospital, Oxford Road, Manchester M13 9WL, UK
| | - Otilia Catanescu
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Donald W. Jacobsen
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Jocelyn D. Glazier
- Maternal and Fetal Health Research Group, School of Biomedicine, University of Manchester, Manchester Academic Health Science Centre, St Mary’s Hospital, Oxford Road, Manchester M13 9WL, UK.
| |
Collapse
|
10
|
Pinheiro da Costa BE, de Almeida PB, Conceição IR, Antonello ICF, d'Avila DO, Poli-de-Figueiredo CE. Erythrocytes L-arginine y+ transporter inhibition by N-ethylmaleimide in ice-bath. Cell Biochem Biophys 2010; 58:69-73. [PMID: 20668961 DOI: 10.1007/s12013-010-9089-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Erythrocytes L: -arginine uptake is conveyed by y+ and y+L membrane transport systems. Pre-incubation with N-ethylmaleimide for 10 min at 37°C inhibits the y+ system. The aim of this study was to determine the ideal pre-incubation temperature in evaluating y+ and y+L systems. Cells were pre-incubated with or without N-ethylmaleimide for 10 min at 4°C and 37°C. L: -Arginine uptake was quantified by radioisotope and standard erythrocytes membrane flux methodology. Results demonstrate that erythrocytes L: -arginine content is depleted by pre-incubation at 37°C for 10 min, thus changing the V (max) measurement. The inhibitory effect of N-ethylmaleimide pre-incubation was temperature independent and already complete after 1 min of incubation. No significant difference in kinetic parameters was detected between cells pre-incubated at 37°C or 4°C, under zero-trans conditions. In conclusion, we suggest that measurement of erythrocytes L: -arginine uptake by y+ and y+L systems could be carried out without N-ethylmaleimide pre-incubation at 37°C.
Collapse
Affiliation(s)
- Bartira Ercília Pinheiro da Costa
- Programa de Pós-graduação em Medicina e Ciências da Saúde (Nefrologia), Faculdade de Medicina/Instituto de Pesquisas Biomédicas/Hospital São Lucas, Pontifícia Universidade Católica do Rio Grande do Sul, 2° Andar - Laboratório de Nefrologia, Instituto de Pesquisas Biomédicas/HSL, Porto Alegre, RS 90610-000, Brazil.
| | | | | | | | | | | |
Collapse
|
11
|
Brahmajothi MV, Mason SN, Whorton AR, McMahon TJ, Auten RL. Transport rather than diffusion-dependent route for nitric oxide gas activity in alveolar epithelium. Free Radic Biol Med 2010; 49:294-300. [PMID: 20423728 PMCID: PMC2916064 DOI: 10.1016/j.freeradbiomed.2010.04.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 04/15/2010] [Accepted: 04/16/2010] [Indexed: 01/24/2023]
Abstract
The pathway by which inhaled NO gas enters pulmonary alveolar epithelial cells has not been directly tested. Although the expected mechanism is diffusion, another route is the formation of S-nitroso-L-cysteine, which then enters the cell through the L-type amino acid transporter (LAT). To determine if NO gas also enters alveolar epithelium this way, we exposed alveolar epithelial-rat type I, type II, L2, R3/1, and human A549-cells to NO gas at the air liquid interface in the presence of L- and D-cysteine+/-LAT competitors. NO gas exposure concentration dependently increased intracellular NO and S-nitrosothiol levels in the presence of L- but not D-cysteine, which was inhibited by LAT competitors, and was inversely proportional to diffusion distance. The effect of L-cysteine on NO uptake was also concentration dependent. Without preincubation with L-cysteine, NO uptake was significantly reduced. We found similar effects using ethyl nitrite gas in place of NO. Exposure to either gas induced activation of soluble guanylyl cylase in a parallel manner, consistent with LAT dependence. We conclude that NO gas uptake by alveolar epithelium achieves NO-based signaling predominantly by forming extracellular S-nitroso-L-cysteine that is taken up through LAT, rather than by diffusion. Augmenting extracellular S-nitroso-L-cysteine formation may augment pharmacological actions of inhaled NO gas.
Collapse
Affiliation(s)
| | - S. Nicholas Mason
- Department of Pediatrics, Duke University Medical Center, Durham, NC 27710
| | - A. Richard Whorton
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710
| | - Timothy J. McMahon
- Department of Medicine, Duke University Medical Center, Durham, NC 27710
| | - Richard L. Auten
- Department of Pediatrics, Duke University Medical Center, Durham, NC 27710
- to whom correspondence should be addressed: R.L. Auten, DUMC Box 3373, Durham NC 27710
| |
Collapse
|
12
|
Tsitsiou E, Sibley CP, D'Souza SW, Catanescu O, Jacobsen DW, Glazier JD. Homocysteine transport by systems L, A and y+L across the microvillous plasma membrane of human placenta. J Physiol 2009; 587:4001-13. [PMID: 19564394 PMCID: PMC2756434 DOI: 10.1113/jphysiol.2009.173393] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [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: 04/01/2009] [Accepted: 06/29/2009] [Indexed: 12/26/2022] Open
Abstract
Elevated maternal plasma levels of homocysteine (Hcy) are associated with pregnancy complications and adverse neonatal outcomes, suggesting placental transport of Hcy may impact on fetal development. However, such transport mechanisms have not been defined. In this study we characterise Hcy transport mechanisms across the microvillous plasma membrane (MVM) of the syncytiotrophoblast, the transporting epithelium of human placenta. Three candidate transport systems, systems L, A and y(+)L, were examined utilising competitive inhibition to investigate the effects of Hcy on the uptake of well-characterised radiolabelled substrates for each system into isolated MVM vesicles, and that of model substrates on 10 microm [(35)S]l-Hcy uptake. System L activity was inhibited by both l-Hcy and dl-Hcy, comparable to model substrates including 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid (BCH). System L constituted the major transport mechanism, with significant BCH inhibition (69%) of [(35)S]l-Hcy uptake. System A activity was also inhibited by l-Hcy and dl-Hcy with a smaller contribution (21%) to [(35)S]l-Hcy uptake. Inhibition by l-Hcy and dl-Hcy of system y(+)L activity was Na(+) sensitive with a significant inhibition constant (K(i)) shift observed following K(+) replacement; l-arginine reduced [(35)S]l-Hcy uptake by 19%. Kinetic modelling of [(35)S]l-Hcy uptake resolved two, Na(+)-independent, transport components (K(m) 72 microm and 9.7 mm). This study provides evidence for the involvement of systems L, A and y(+)L in placental Hcy transport. Such transport, by competing with endogenous amino acids for transporter activity, could have major implications for syncytiotrophoblast metabolism and function as well as fetal development.
Collapse
Affiliation(s)
- Eleni Tsitsiou
- Maternal and Fetal Health Research Group, University of Manchester, St Mary's Hospital, Hathersage Road, Manchester M13 0JH, UK
| | | | | | | | | | | |
Collapse
|
13
|
Rotmann A, Simon A, Martiné U, Habermeier A, Closs EI. Activation of classical protein kinase C decreases transport via systems y+ and y+L. Am J Physiol Cell Physiol 2007; 292:C2259-68. [PMID: 17329401 DOI: 10.1152/ajpcell.00323.2006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Activation of protein kinase C (PKC) downregulates the human cationic amino acid transporters hCAT-1 (SLC7A1) and hCAT-3 (SLC7A3) (Rotmann A, Strand D, Martiné U, Closs EI. J Biol Chem 279: 54185-54192, 2004; Rotmann A, Vekony N, Gassner D, Niegisch G, Strand D, Martine U, Closs EI. Biochem J 395: 117-123, 2006). However, others found that PKC increased arginine transport in various mammalian cell types, suggesting that the expression of different arginine transporters might be responsible for the opposite PKC effects. We thus investigated the consequence of PKC activation by phorbol-12-myristate-13-acetate (PMA) in various human cell lines expressing leucine-insensitive system y(+) [hCAT-1, hCAT-2B (SLC7A2), or hCAT-3] as well as leucine-sensitive system y(+)L [y(+)LAT1 (SLC7A7) or y(+)LAT2 (SLC7A6)] arginine transporters. PMA reduced system y(+) activity in all cell lines tested, independent of the hCAT isoform expressed, while mRNAs encoding the individual hCAT isoforms were either unchanged or increased. System y(+)L activity was also inhibited by PMA. The extent and onset of inhibition varied between cell lines; however, a PMA-induced increase in arginine transport was never observed. In addition, when expressed in Xenopus laevis oocytes, y(+)LAT1 and y(+)LAT2 activity was reduced by PMA, and this inhibition could be prevented by the PKC inhibitor bisindolylmaleimide I. In ECV304 cells, PMA-induced inhibition of systems y(+) and y(+)L could be prevented by Gö6976, a specific inhibitor of conventional PKCs. Thymelea toxin, which activates preferentially classical PKC, had a similar inhibitory effect as PMA. In contrast, phosphatidylinositol-3,4,5-triphosphate-dipalmitoyl, an activator of atypical PKC, had no effect. These data demonstrate that systems y(+) and y(+)L are both downregulated by classical PKC.
Collapse
Affiliation(s)
- Alexander Rotmann
- Dept. of Pharmacology, Johannes Gutenberg University, Obere Zahlbacher Str. 67, 55101 Mainz, Germany
| | | | | | | | | |
Collapse
|
14
|
Brunini TMC, Yaqoob MM, Roberts NB, Ellory JC, Moss MB, Siqueira MAS, Mann GE, Mendes Ribeiro AC. CHARACTERIZATION OF CATIONIC AMINO ACID TRANSPORT SYSTEMS IN RAT ERYTHROCYTES: LACK OF EFFECT OF URAEMIA ON l-ARGININE INFLUX. Clin Exp Pharmacol Physiol 2006; 33:702-7. [PMID: 16895543 DOI: 10.1111/j.1440-1681.2006.04421.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [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] [Indexed: 11/27/2022]
Abstract
1. Chronic renal failure (CRF) is associated with the abnormal regulation of nitric oxide (NO) synthesis at the systemic level. The transport of L-arginine, upregulated in blood cells from uraemic patients, modulates NO synthesis in this pathological condition. The model of partial nephrectomy in rats is widely accepted as a valid model of uraemia. Because there are no reports of L-arginine transport in blood cells from uraemic rats, the aim of the present study was to investigate L-arginine transport in red blood cells (RBCs) from these rats. 2. The kinetics of L-arginine transport in RBC and plasma and the amino acid profiles of RBC were investigated in control, sham-operated and subtotally nephrectomized rats. 3. L-Arginine transport was mediated via the cationic amino acid transport system y+ and a transport system with kinetics resembling the human system y+L. In control RBC, the apparent Ki for L-leucine inhibition of L-arginine transport via system y+L was 0.16 +/- 0.02 and 4.8 +/- 2 mmol/L in the presence of Li+ and Na+, respectively. 4. The Vmax values for L-arginine transport via system y+L and system y+ were similar in RBC from control sham-operated and uraemic rats. Moreover, L-arginine concentrations in plasma and RBC were not affected by uraemia. 5. The findings of the present study provide the first evidence that L-arginine transport in rat erythrocytes is mediated by two distinct cationic transport systems with characteristics of systems y+ and y+L, which accept neutral amino acids only in the presence of Li+. In contrast with previous studies in uraemic patients, plasma levels and maximal transport rates of L-arginine were not altered in this rat model of CRF.
Collapse
Affiliation(s)
- T M C Brunini
- Departamento de Farmacologia e Psicobiologia, Instituto de Biologia, Universidade do Estado do Rio de Janeiro, Brazil
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Angelo S, Cabrera S, Rojas AM, Rodríguez N, Devés R. Testing the hypothesis that system y(+)L accounts for high- and low-transport phenotypes in chicken erythrocytes using L-leucine as substrate. J Membr Biol 2005; 204:93-100. [PMID: 16151705 DOI: 10.1007/s00232-005-0751-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2004] [Revised: 05/06/2005] [Indexed: 10/25/2022]
Abstract
Experiments were carried out to test the hypothesis that system y(+)L accounts for the high (HT) and low (LT) amino-acid transport phenotypes in chicken erythrocytes and to explain the different effect of selective breeding on lysine and leucine fluxes. L: -Leucine transport was characterized in individuals which had been separated into two groups (HT and LT) according to their capacity to transport L: -lysine across the erythrocyte membrane. Whereas lysine influx (1 muM: ) in the two groups differed by 32-fold (HT/LT), leucine influx was not significantly different. Average rates (nmol/ L cells/ min) were: 227 (HT) and 7.0 (LT) for L: -lysine, and 8.9 (HT) and 7.1 (LT) for L: -leucine. The differential ability of L: -lysine and L: -leucine fluxes to discriminate between the HT and LT phenotypes was shown to be consistent with the interactions of these substrates with system y(+)L and to vary depending on the conditions of the assay. It is shown that the two phenotypes can be clearly discriminated by measuring L: -leucine influx in the presence of Li(+). These results support the hypothesis that the HT and LT phenotypes reflect alterations in the function of system y(+)L and illustrate that the choice of the appropriate substrate and medium composition must be carefully considered when investigating the consequences of either experimental or natural alterations of broad-scope transporters.
Collapse
Affiliation(s)
- S Angelo
- Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago 7, Casilla 70005 Chile
| | | | | | | | | |
Collapse
|
16
|
Regnault TRH, Marconi AM, Smith CH, Glazier JD, Novak DA, Sibley CP, Jansson T. Placental amino acid transport systems and fetal growth restriction – A workshop report. Placenta 2005; 26 Suppl A:S76-80. [PMID: 15837072 DOI: 10.1016/j.placenta.2005.02.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/06/2005] [Indexed: 11/25/2022]
Affiliation(s)
- T R H Regnault
- Department of Pediatrics, Division of Perinatal Medicine, University of Colorado Health Sciences Center, Perinatal Research Center, PO Box 6508, F441, Aurora, CO 80045, USA.
| | | | | | | | | | | | | |
Collapse
|
17
|
Rotoli BM, Bussolati O, Sala R, Gazzola GC, Dall'Asta V. The transport of cationic amino acids in human airway cells: expression of system y+L activity and transepithelial delivery of NOS inhibitors. FASEB J 2005; 19:810-2. [PMID: 15746185 DOI: 10.1096/fj.04-2924fje] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The transport of arginine has been characterized in human airway Calu-3 cells. As assessed with RT-PCR, Calu-3 cells express the genes for several transporters, such as the system y+-related SLC7A1, SLC7A2, and SLC7A4; the system y+L-related SLC7A6, SLC7A7, and SLC3A2; and the system B0,+-related SLC6A14. In polarized Calu-3 cell monolayers, apical arginine influx has a leucine-sensitive, sodium-dependent component and a leucine- and lysine-resistant sodium-independent fraction. At the basolateral membrane, arginine transport was fully sodium-independent and partially inhibited by leucine provided that sodium was present in the extracellular medium. Moreover, extracellular leucine trans-stimulated arginine efflux from the basolateral membrane in the presence, but not in the absence, of sodium. The transepithelial, apical to basolateral, arginine transport strictly depended on the presence of sodium and was markedly inhibited by apical leucine, but significantly trans-stimulated by the neutral amino acid added at the basolateral side. When added at the apical side, the NOS-inhibitors NMMA and NIL, CAA analogs with a free carboxyl group, markedly inhibited the apical arginine influx and the transepithelial flux of the cationic amino acid. The same compounds trans-stimulated basolateral arginine efflux. None of these effects were observed in the presence of the methyl ester analog NAME. The basolateral medium of Calu-3 cell monolayers, obtained after incubation in the presence of the three inhibitors at the apical side, inhibited the production of NO by activated murine macrophages. The inhibitory effect of the Calu-3 cell conditioned medium was time-dependent and markedly higher with NMMA and NIL than with NAME. Moreover, the NOS-inhibitory effect of the medium was significantly enhanced if NMMA and NIL, at the apical side, and basolateral leucine were simultaneously present during the conditioning procedure. These results indicate that 1) human airway epithelial cells express a functional system y+L at the basolateral membrane; 2) in this model, transepithelial arginine transport involves apical influx through system B0,+ and basolateral efflux through system y+L, and 3) the same transporters also perform an efficient transepithelial transport of amino acid-like NOS inhibitors.
Collapse
Affiliation(s)
- Bianca Maria Rotoli
- Sezione di Patologia Generale e Clinica, Dipartimento di Medicina Sperimentale, Università degli Studi di Parma, Parma, Italy
| | | | | | | | | |
Collapse
|
18
|
Figueiredo AE, Almeida PB, Pinheiro da Costa BE, D'Avila DO, Poli de Figueiredo CE. Erythrocyte L-arginine uptake in peritoneal dialysis patients: systems y and y+ L. Adv Perit Dial 2005; 21:2-4. [PMID: 16686274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
L-Arginine is the substrate for nitric oxide synthesis and may enter cells by the y+ and y+ L transport systems. Peritoneal membrane characteristics may depend on vascular function and the L-arginine-nitric oxide pathway. In a cross-sectional study, we evaluated erythrocyte L-arginine uptake in stable peritoneal dialysis (PD) patients with various categories of peritoneal transport function. We used 14C as a marker and N-ethyl-maleimide as an inhibitor of the y+ system to measure maximal uptake capacity (Vma in ulmol/L cell/h) and the half-saturation constant (Km in micromol/L) in erythrocytes. The sample consisted of 41 patients (mean age: 50 +/- 17 years; 5 with diabetes; 18 men). Mean dialysate-toplasma creatinine (D/P(Cr)) was 0.62 +/- 0.14. Peritoneal membrane transport was classified as high, high-average, low-average, or low in 10, 11, 11, and 9 patients, respectively. Mean y+ L Vmax, was 208 +/- 111 micromol/L cell/h, 494 +/- 893 micromol/L cell/h, 222 +/- 59 micromol/L cell/h, and 193 +/- 63 umol/L cell/h [p = 0.404, analysis of variance (ANOVA)] for the high, high-average, low-average, and low transporters respectively. Similarly, mean y+ Vmax was 963 +/- 1034 micromol/L cell/h 843 +/- 366 micromol/L cell/h, 639 +/- 254 micromol/L cell/h, and 774 +/- 378 micromol/L cell/h (p = 0.647, ANOVA). As with Vmax, the y+ L Km and y+ Km values were not significantly different between the various peritoneal transport categories. A negative correlation was observed between y+ Vmax and Kt/V (r = -0.393, p = 0.011). Erythrocyte uptake of L-arginine does not vary with peritoneal membrane transport characteristics, but maximal L-arginine uptake capacity is higher in patients with a lower Kt/V.
Collapse
Affiliation(s)
- Ana E Figueiredo
- Programa de Pós-graduação em Medicina e Ciências da Saúde (Nefrologia), Laboratório de Nefrologia, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil
| | | | | | | | | |
Collapse
|
19
|
Arancibia-Garavilla Y, Toledo F, Casanello P, Sobrevia L. Nitric oxide synthesis requires activity of the cationic and neutral amino acid transport system y+L in human umbilical vein endothelium. Exp Physiol 2004; 88:699-710. [PMID: 14603368 DOI: 10.1113/eph8802647] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
L-arginine transport is mediated by the cationic/neutral amino acid transport system y+L and cationic amino acid transporters y+/CATs in human umbilical vein endothelial cells (HUVECs). System y+/CATs activity may be rate-limiting for nitric oxide (NO) synthesis, but no reports have demonstrated system y+L involvement in NO synthesis in endothelium. We investigated the role of system y+L in NO synthesis in HUVECs. Transport of 1.5 microM L-arginine was inhibited (P < 0.05) by L-lysine (K(i), 1.4 micro M), L-leucine (K(i), 1.8 micro M) and L-phenylalanine (K(i), 4.1 microM), but was unaltered (P > 0.05) by L-alanine or L-cysteine. The system y+/CATs inhibitor, N-ethylmaleimide (NEM), did not alter 1.5 microM L-arginine transport, but inhibited (92 +/- 3 %) 100 microM L-arginine transport. L-arginine transport in the presence of NEM was saturable (V(max), 0.37 +/- 0.02 pmol (microg protein)(-1) min(-1); K(m), 1.5 +/- 0.3 microM) and competitively inhibited by L-leucine in the presence of Na+ (V(max), 0.49 +/- 0.06 pmol (microg protein)(-1) min(-1); K(m), 6.5 +/- 0.9 microM). HUVECs express SLC3A2/4F2hc, SLC7A7/4F2-lc2 and SLC7A6/4F2-lc3 genes encoding for the high-affinity transport system y+L. N(G)-Nitro-L-arginine methyl ester and L-leucine, but not NEM, inhibited NO synthesis in medium containing 1.5 microM L-arginine. Cells exposed to 25 mM D-glucose (24 h) exhibited reduced system y+L activity (V(max), 0.15 +/- 0.008 pmol (microg protein)(-1) min(-1); K(m), 1.4 +/- 0.3 microM) and NO synthesis. However, 25 mM D-glucose increased NO synthesis and L-arginine transport via system y+. Thus, L-arginine transport through system y+L plays a role in NO synthesis, which could be a determining factor in pathological conditions where the endothelial L-arginine-NO pathway is altered, such as in diabetes mellitus.
Collapse
Affiliation(s)
- Yerko Arancibia-Garavilla
- Cellular and Molecular Physiology Laboratory (CMPL), Department of Obstetrics and Gynaecology, Medical Research Centre (CIM), School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, PO Box 114-D, Santiago, Chile
| | | | | | | |
Collapse
|
20
|
Brunini TMC, Yaqoob MM, Novaes Malagris LE, Ellory JC, Mann GE, Mendes Ribeiro AC. Increased nitric oxide synthesis in uraemic platelets is dependent on L-arginine transport via system y(+)L. Pflugers Arch 2003; 445:547-50. [PMID: 12634924 DOI: 10.1007/s00424-002-0978-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2002] [Revised: 10/04/2002] [Accepted: 10/15/2002] [Indexed: 01/28/2023]
Abstract
Bleeding tendency in uraemic patients seems to be related to alterations in the activity of the L-arginine-nitric oxide (NO) signalling pathway in platelets. We have reported previously that L-arginine influx into human platelets is mediated by the high-affinity cationic amino acid transport system y(+)L. In the present study we examined the dependency of nitric oxide synthase (NOS) activity on L-arginine transport in platelets isolated from healthy controls and uraemic patients on haemodialysis. We investigated basal and ADP-stimulated NOS activity, as reflected by the conversion of L-[(3)H]arginine to L-[(3)H]citrulline, in platelets obtained from healthy controls and uraemic patients on haemodialysis. To determine whether NOS activity depended on L-arginine transport, we analysed the effects of competitive inhibitors of L-arginine transport via system y(+)L on NOS activity. Basal NOS activity was increased from 0.21+/-0.06 to 0.7+/-0.2 pmol/10(8) platelets ( n=9, P<0.05) in uraemic patients. Stimulation by ADP (10 micro M) significantly increased NOS activity (inhibitable by L-NAME) in control platelets (252%) but failed to increase further the elevated NOS activity in uraemic platelets. Homocysteine and L-leucine, competitive inhibitors of system y(+)L, markedly inhibited NOS activity in uraemic platelets. These observations indicate that platelets from uraemic patients on haemodialysis generate more NO than control platelets and that entry of L-arginine via system y(+)L is most likely rate-limiting for platelet NO production in chronic renal failure.
Collapse
Affiliation(s)
- T M C Brunini
- Departamento de Farmacologia e Psicobiologia, Instituto de Biologia, Av. 28 de Setembro 87, CEP 20551-030, Rio de Janeiro, Brazil.
| | | | | | | | | | | |
Collapse
|
21
|
Vargas M, Devés R. System y+L-like activities account for high and low amino-acid transport phenotypes in chicken erythrocytes. J Membr Biol 2001; 183:183-93. [PMID: 11696860 DOI: 10.1007/s00232-001-0066-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2001] [Indexed: 11/28/2022]
Abstract
The functional properties of the transport of lysine across the chicken erythrocyte membrane were investigated. The animal population studied (male Leghorn chickens, 6-14 weeks old) was found to consist of two groups presenting either low (LT, 19 individuals) or high transport rates (HT, 20 individuals). The rates of influx in the two groups, measured at a concentration of l-lysine of 1 microm, differed by a factor of 34. The transport activities observed in LT and HT erythrocytes were compatible with the general features of system y+L, but showed some differences in specificity. The transporter in the LT group was found to bind l-lysine, l-leucine, l-methionine and l-glutamine with high affinity, in the presence of sodium, as described for system y+L in human erythrocytes. The activity present in HT erythrocytes exhibited a much lower affinity for l-leucine, but was able to interact strongly with l-glutamine and l-methionine. The specificity pattern of the HT transporter, has not been described in other cell types. In other respects, the properties of the two systems were similar. Sodium replacement with potassium, drastically reduced the affinity for l-leucine, without affecting lysine transport. Both transporters function as tightly coupled exchangers, are inactivated by p-chloromercuribenzene sulfonate and resistant to N-ethylmaleimide. These findings explain previous results obtained in selective breeding experiments of chicken with high and low amino-acid transport activity.
Collapse
Affiliation(s)
- M Vargas
- Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Casilla 70005, Santiago 7, Chile
| | | |
Collapse
|