The amino acid transporter CG1139 is required for retrograde transport and fast recovery of gut enterocytes after Serratia marcescens intestinal infection

The intestinal tract is constantly exposed to microbes. Severe infections can arise following the ingestion of pathogenic microbes from contaminating food or water sources. The host directly fights off ingested pathogens with resistance mechanisms, the immune response, or withstands and repairs the damages inflicted either by virulence factors or the host immune effectors, through tolerance/resilience mechanisms. In a previous study, we reported the existence in Drosophila melanogaster of a novel evolutionarily conserved resilience mechanism to intestinal infections with a hemolysin-positive Serratia marcescens strain (SmDb11), the purge of the apical cytoplasm of enterocytes. The epithelium becomes very thin and recovers rapidly, regaining its normal thickness within several hours. Here, we found that this recovery of gut enterocyte morphology is based on the host internal reserves and not on ingested food. Indeed, we observed a retrograde transport of amino acids from the host hemolymph to the enterocytes. We have identified several amino acid transporters required for recovery and we focused on the SLC36 family transporter CG1139. CG1139 is required for the retrograde transport of amino acids. RNA sequencing revealed that genes involved in the positive regulation of growth were observed in wild-type but not CG1139 mutant guts, in which the expression of Myc and genes involved in Insulin signaling is down-regulated. Functional analysis revealed that Myc is also required for the recovery of the thick gut epithelium after infection. Altogether, our results show the importance of an amino acid transporter in the fast regrowth of the enterocytes upon infection. Unexpectedly, we found that this transporter acts non cell-autonomously and can regulate the transcription of other genes, suggesting a signaling function of CG1139 that therefore appears to act as a transceptor.

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ACE2 and gut amino acid transport

Clinical Science ◽

10.1042/cs20200477 ◽

2020 ◽

Vol 134 (21) ◽

pp. 2823-2833 ◽

Cited By ~ 2

Author(s):

Simone M.R. Camargo ◽

Raphael N. Vuille-dit-Bille ◽

Chantal F. Meier ◽

François Verrey

Keyword(s):

Amino Acids ◽

Small Intestine ◽

Amino Acid ◽

Amino Acid Transporter ◽

Neutral Amino Acid ◽

Amino Acid Transporters ◽

Type I ◽

Small Intestinal Mucosa ◽

Neutral Amino Acid Transporter ◽

Acid Transporter

Abstract ACE2 is a type I membrane protein with extracellular carboxypeptidase activity displaying a broad tissue distribution with highest expression levels at the brush border membrane (BBM) of small intestine enterocytes and a lower expression in stomach and colon. In small intestinal mucosa, ACE2 mRNA expression appears to increase with age and to display higher levels in patients taking ACE-inhibitors (ACE-I). There, ACE2 protein heterodimerizes with the neutral amino acid transporter Broad neutral Amino acid Transporter 1 (B0AT1) (SLC6A19) or the imino acid transporter Sodium-dependent Imino Transporter 1 (SIT1) (SLC6A20), associations that are required for the surface expression of these transport proteins. These heterodimers can form quaternary structures able to function as binding sites for SARS-CoV-2 spike glycoproteins. The heterodimerization of the carboxypeptidase ACE2 with B0AT1 is suggested to favor the direct supply of substrate amino acids to the transporter, but whether this association impacts the ability of ACE2 to mediate viral infection is not known. B0AT1 mutations cause Hartnup disorder, a condition characterized by neutral aminoaciduria and, in some cases, pellagra-like symptoms, such as photosensitive rash, diarrhea, and cerebellar ataxia. Correspondingly, the lack of ACE2 and the concurrent absence of B0AT1 expression in small intestine causes a decrease in l-tryptophan absorption, niacin deficiency, decreased intestinal antimicrobial peptide production, and increased susceptibility to inflammatory bowel disease (IBD) in mice. Thus, the abundant expression of ACE2 in small intestine and its association with amino acid transporters appears to play a crucial role for the digestion of peptides and the absorption of amino acids and, thereby, for the maintenance of structural and functional gut integrity.

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The Regulation and Function of the L-Type Amino Acid Transporter 1 (LAT1) in Cancer

International Journal of Molecular Sciences ◽

10.3390/ijms19082373 ◽

2018 ◽

Vol 19 (8) ◽

pp. 2373 ◽

Cited By ~ 24

Author(s):

Travis Salisbury ◽

Subha Arthur

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Cancer Cells ◽

Amino Acid Uptake ◽

Essential Amino Acids ◽

Amino Acid Transporter ◽

Amino Acid Transporters ◽

Acid Uptake ◽

Cancer Pathways ◽

Acid Transporter

The progression of cancer is associated with increases in amino acid uptake by cancer cells. Upon their entry into cells through specific transporters, exogenous amino acids are used to synthesize proteins, nucleic acids and lipids and to generate ATP. The essential amino acid leucine is also important for maintaining cancer-associated signaling pathways. By upregulating amino acid transporters, cancer cells gain greater access to exogenous amino acids to support chronic proliferation, maintain metabolic pathways, and to enhance certain signal transduction pathways. Suppressing cancer growth by targeting amino acid transporters will require an in-depth understanding of how cancer cells acquire amino acids, in particular, the transporters involved and which cancer pathways are most sensitive to amino acid deprivation. L-Type Amino Acid Transporter 1 (LAT1) mediates the uptake of essential amino acids and its expression is upregulated during the progression of several cancers. We will review the upstream regulators of LAT1 and the downstream effects caused by the overexpression of LAT1 in cancer cells.

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Amino acid transporters in the regulation of insulin secretion and signalling

Biochemical Society Transactions ◽

10.1042/bst20180250 ◽

2019 ◽

Vol 47 (2) ◽

pp. 571-590 ◽

Cited By ~ 6

Author(s):

Kiran Javed ◽

Stephen J. Fairweather

Keyword(s):

Amino Acids ◽

Small Intestine ◽

Insulin Secretion ◽

Amino Acid ◽

Insulin Signalling ◽

Amino Acid Transporter ◽

Fibroblast Growth Factor 21 ◽

Amino Acid Transporters ◽

Acid Transporter

Abstract Amino acids are increasingly recognised as modulators of nutrient disposal, including their role in regulating blood glucose through interactions with insulin signalling. More recently, cellular membrane transporters of amino acids have been shown to form a pivotal part of this regulation as they are primarily responsible for controlling cellular and circulating amino acid concentrations. The availability of amino acids regulated by transporters can amplify insulin secretion and modulate insulin signalling in various tissues. In addition, insulin itself can regulate the expression of numerous amino acid transporters. This review focuses on amino acid transporters linked to the regulation of insulin secretion and signalling with a focus on those of the small intestine, pancreatic β-islet cells and insulin-responsive tissues, liver and skeletal muscle. We summarise the role of the amino acid transporter B0AT1 (SLC6A19) and peptide transporter PEPT1 (SLC15A1) in the modulation of global insulin signalling via the liver-secreted hormone fibroblast growth factor 21 (FGF21). The role of vesicular vGLUT (SLC17) and mitochondrial SLC25 transporters in providing glutamate for the potentiation of insulin secretion is covered. We also survey the roles SNAT (SLC38) family and LAT1 (SLC7A5) amino acid transporters play in the regulation of and by insulin in numerous affective tissues. We hypothesise the small intestine amino acid transporter B0AT1 represents a crucial nexus between insulin, FGF21 and incretin hormone signalling pathways. The aim is to give an integrated overview of the important role amino acid transporters have been found to play in insulin-regulated nutrient signalling.

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The Role of Large Neutral Amino Acid Transporter (LAT1) in Cancer

Current Cancer Drug Targets ◽

10.2174/1568009619666190802135714 ◽

2019 ◽

Vol 19 (11) ◽

pp. 863-876 ◽

Cited By ~ 3

Author(s):

Xinjie Lu

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Metabolic Networks ◽

Amino Acid Transporter ◽

Amino Acid Transporters ◽

Large Neutral Amino Acid ◽

Pharmaceutical Drugs ◽

Cationic Amino Acid ◽

Acid Transporter

Background: The solute carrier family 7 (SLC7) can be categorically divided into two subfamilies, the L-type amino acid transporters (LATs) including SLC7A5-13, and SLC7A15, and the cationic amino acid transporters (CATs) including SLC7A1-4 and SLC7A14. Members of the CAT family transport predominantly cationic amino acids by facilitating diffusion with intracellular substrates. LAT1 (also known as SLC7A5), is defined as a heteromeric amino acid transporter (HAT) interacting with the glycoprotein CD98 (SLC3A2) through a conserved disulfide to uptake not only large neutral amino acids, but also several pharmaceutical drugs to cells. Methods: In this review, we provide an overview of the interaction of the structure-function of LAT1 and its essential role in cancer, specifically, its role at the blood-brain barrier (BBB) to facilitate the transport of thyroid hormones, pharmaceuticals (e.g., I-DOPA, gabapentin), and metabolites into the brain. Results: LAT1 expression increases as cancers progress, leading to higher expression levels in highgrade tumors and metastases. In addition, LAT1 plays a crucial role in cancer-associated reprogrammed metabolic networks by supplying tumor cells with essential amino acids. Conclusion: The increasing understanding of the role of LAT1 in cancer has led to an increase in interest surrounding its potential as a drug target for cancer treatment.

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Cloning, Expression, and Functional Characterization of Secondary Amino Acid Transporters of Lactococcus lactis

Journal of Bacteriology ◽

10.1128/jb.01948-12 ◽

2012 ◽

Vol 195 (2) ◽

pp. 340-350 ◽

Cited By ~ 23

Author(s):

Hein Trip ◽

Niels L. Mulder ◽

Juke S. Lolkema

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Lactococcus Lactis ◽

Aromatic Amino Acids ◽

Amino Acid Transporter ◽

Amino Acid Transporters ◽

Acid Uptake ◽

Content Type ◽

Secondary Amino ◽

Acid Transporter

ABSTRACTFourteen genes encoding putative secondary amino acid transporters were identified in the genomes ofLactococcus lactissubsp.cremorisstrains MG1363 and SK11 andL. lactissubsp. lactisstrains IL1403 and KF147, 12 of which were common to all four strains. Amino acid uptake inL. lactiscells overexpressing the genes revealed transporters specific for histidine, lysine, arginine, agmatine, putrescine, aromatic amino acids, acidic amino acids, serine, and branched-chain amino acids. Substrate specificities were demonstrated by inhibition profiles determined in the presence of excesses of the other amino acids. Four knockout mutants, lacking the lysine transporter LysP, the histidine transporter HisP (formerly LysQ), the acidic amino acid transporter AcaP (YlcA), or the aromatic amino acid transporter FywP (YsjA), were constructed. The LysP, HisP, and FywP deletion mutants showed drastically decreased rates of uptake of the corresponding substrates at low concentrations. The same was observed for the AcaP mutant with aspartate but not with glutamate. In rich M17 medium, the deletion of none of the transporters affected growth. In contrast, the deletion of the HisP, AcaP, and FywP transporters did affect growth in a defined medium with free amino acids as the sole amino acid source. HisP was essential at low histidine concentrations, and AcaP was essential in the absence of glutamine. FywP appeared to play a role in retaining intracellularly synthesized aromatic amino acids when these were not added to the medium. Finally, HisP, AcaP, and FywP did not play a role in the excretion of accumulated histidine, glutamate, or phenylalanine, respectively, indicating the involvement of other transporters.

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Pichia pastoris and the Recombinant Human Heterodimeric Amino Acid Transporter 4F2hc-LAT1: From Clone Selection to Pure Protein

Methods and Protocols ◽

10.3390/mps4030051 ◽

2021 ◽

Vol 4 (3) ◽

pp. 51

Author(s):

Satish Kantipudi ◽

Daniel Harder ◽

Sara Bonetti ◽

Dimitrios Fotiadis ◽

Jean-Marc Jeckelmann

Keyword(s):

Amino Acid ◽

Pichia Pastoris ◽

Protein Complexes ◽

Amino Acid Transporter ◽

Amino Acid Transporters ◽

Expression Host ◽

Amino Acids And Derivatives ◽

Heterodimeric Complex ◽

Acid Transporter ◽

And Function

Heterodimeric amino acid transporters (HATs) are protein complexes composed of two subunits, a heavy and a light subunit belonging to the solute carrier (SLC) families SLC3 and SLC7. HATs transport amino acids and derivatives thereof across the plasma membrane. The human HAT 4F2hc-LAT1 is composed of the type-II membrane N-glycoprotein 4F2hc (SLC3A2) and the L-type amino acid transporter LAT1 (SLC7A5). 4F2hc-LAT1 is medically relevant, and its dysfunction and overexpression are associated with autism and tumor progression. Here, we provide a general applicable protocol on how to screen for the best membrane transport protein-expressing clone in terms of protein amount and function using Pichia pastoris as expression host. Furthermore, we describe an overexpression and purification procedure for the production of the HAT 4F2hc-LAT1. The isolated heterodimeric complex is pure, correctly assembled, stable, binds the substrate L-leucine, and is thus properly folded. Therefore, this Pichia pastoris-derived recombinant human 4F2hc-LAT1 sample can be used for downstream biochemical and biophysical characterizations.

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Neutral amino acid transporter ASCT2 displays substrate-induced Na+ exchange and a substrate-gated anion conductance

Biochemical Journal ◽

10.1042/bj3460705 ◽

2000 ◽

Vol 346 (3) ◽

pp. 705-710 ◽

Cited By ~ 58

Author(s):

Angelika BRÖER ◽

Carsten WAGNER ◽

Florian LANG ◽

Stefan BRÖER

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Anion Channel ◽

Amino Acid Transporter ◽

Neutral Amino Acid ◽

Xenopus Laevis Oocytes ◽

Anion Conductance ◽

Neutral Amino Acid Transporter ◽

Inward Currents ◽

Acid Transporter

The neutral amino acid transporter ASCT2 mediates electroneutral obligatory antiport but at the same time requires Na+ for its function. To elucidate the mechanism, ASCT2 was expressed in Xenopus laevis oocytes and transport was analysed by flux studies and two-electrode voltage clamp recordings. Flux studies with 22NaCl indicated that the uptake of one molecule of glutamine or alanine is accompanied by the uptake of four to seven Na+ ions. Similarly to the transport of amino acids, the Na+ uptake was mediated by an obligatory Na+ exchange mechanism that depended on the presence of amino acids but was not stoichiometrically coupled to the amino acid transport. Other cations could not replace Na+ in this transport mechanism. When NaCl was replaced by NaSCN in the transport buffer, the superfusion of oocytes with amino acid substrates resulted in large inward currents, indicating the presence of a substrate-gated anion channel in the ASCT2 transporter. The Km for glutamine derived from these experiments is in good agreement with the Km derived from flux studies; it varied between 40 and 90 μM at holding potentials of -60 and -20 mV respectively. The permeability of the substrate-gated anion conductance decreased in the order SCN- NO3- > I- > Cl- and also required the presence of Na+.

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Downregulation of Placental Amino Acid Transporter Expression and mTORC1 Signaling Activity Contributes to Fetal Growth Retardation in Diabetic Rats

International Journal of Molecular Sciences ◽

10.3390/ijms21051849 ◽

2020 ◽

Vol 21 (5) ◽

pp. 1849

Author(s):

Jie Xu ◽

Jiao Wang ◽

Yang Cao ◽

Xiaotong Jia ◽

Yujia Huang ◽

...

Keyword(s):

Amino Acid ◽

Rat Model ◽

Amino Acid Transporter ◽

Amino Acid Transporters ◽

Amino Acid Transport System ◽

Intrauterine Growth ◽

System L ◽

Acid Transporter ◽

Transporter Expression

Alterations in placental transport may contribute to abnormal fetal intrauterine growth in pregnancies complicated by diabetes, but it is not clear whether the placental amino acid transport system is altered in diabetic pregnancies. We therefore studied the changes in the expressions of placental amino acid transporters in a rat model of diabetes induced by streptozotocin, and tested the effects of hyperglycemia on trophoblast amino acid transporter in vitro. Our results showed that the expressions for key isoforms of system L amino acid transporters were significantly reduced in the placentas of streptozotocin-induced diabetic pregnant rats, which was associated with the decreased birthweight in the rats. A decreased placental efficiency and decreased placental mammalian target of rapamycin (mTOR) complex 1 (mTORC1) activity were also found in the rat model. In addition, hyperglycemia in vitro could inhibit amino acid transporter expression and mTORC1 activity in human trophoblast. Inhibition of mTORC1 activity led to reduced amino acid transporter expression in placental trophoblast. We concluded that reduced placental mTORC1 activity during pregnancy resulted in decreased placental amino acid transporter expression and, subsequently, contributed to fetal intrauterine growth restriction in pregnancies complicated with diabetes.

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Amino Acid Transport Defects in Human Inherited Metabolic Disorders

International Journal of Molecular Sciences ◽

10.3390/ijms21010119 ◽

2019 ◽

Vol 21 (1) ◽

pp. 119 ◽

Cited By ~ 3

Author(s):

Raquel Yahyaoui ◽

Javier Pérez-Frías

Keyword(s):

Amino Acid ◽

Metabolic Disorders ◽

Strong Association ◽

Cell Types ◽

Amino Acid Transporter ◽

Molecular Defect ◽

Amino Acid Transporters ◽

Inherited Disorders ◽

Laboratory Findings ◽

Acid Transporter

Amino acid transporters play very important roles in nutrient uptake, neurotransmitter recycling, protein synthesis, gene expression, cell redox balance, cell signaling, and regulation of cell volume. With regard to transporters that are closely connected to metabolism, amino acid transporter-associated diseases are linked to metabolic disorders, particularly when they involve different organs, cell types, or cell compartments. To date, 65 different human solute carrier (SLC) families and more than 400 transporter genes have been identified, including 11 that are known to include amino acid transporters. This review intends to summarize and update all the conditions in which a strong association has been found between an amino acid transporter and an inherited metabolic disorder. Many of these inherited disorders have been identified in recent years. In this work, the physiological functions of amino acid transporters will be described by the inherited diseases that arise from transporter impairment. The pathogenesis, clinical phenotype, laboratory findings, diagnosis, genetics, and treatment of these disorders are also briefly described. Appropriate clinical and diagnostic characterization of the underlying molecular defect may give patients the opportunity to avail themselves of appropriate therapeutic options in the future.

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Intestinal peptidases form functional complexes with the neutral amino acid transporter B0AT1

Biochemical Journal ◽

10.1042/bj20120307 ◽

2012 ◽

Vol 446 (1) ◽

pp. 135-148 ◽

Cited By ~ 40

Author(s):

Stephen J. Fairweather ◽

Angelika Bröer ◽

Megan L. O'Mara ◽

Stefan Bröer

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Brush Border ◽

Brush Border Membrane ◽

Amino Acid Transporter ◽

The Body ◽

Site Directed Mutagenesis ◽

Substrate Affinity ◽

Xenopus Laevis Oocytes ◽

Acid Transporter

The brush-border membrane of the small intestine and kidney proximal tubule are the major sites for the absorption and re-absorption of nutrients in the body respectively. Transport of amino acids is mediated through the action of numerous secondary active transporters. In the mouse, neutral amino acids are transported by B0AT1 [broad neutral (0) amino acid transporter 1; SLC6A19 (solute carrier family 6 member 19)] in the intestine and by B0AT1 and B0AT3 (SLC6A18) in the kidney. Immunoprecipitation and Blue native electrophoresis of intestinal brush-border membrane proteins revealed that B0AT1 forms complexes with two peptidases, APN (aminopeptidase N/CD13) and ACE2 (angiotensin-converting enzyme 2). Physiological characterization of B0AT1 expressed together with these peptidases in Xenopus laevis oocytes revealed that APN increased the substrate affinity of the transporter up to 2.5-fold and also increased its surface expression (Vmax). Peptide competition experiments, in silico modelling and site-directed mutagenesis of APN suggest that the catalytic site of the peptidase is involved in the observed changes of B0AT1 apparent substrate affinity, possibly by increasing the local substrate concentration. These results provide evidence for the existence of B0AT1-containing digestive complexes in the brush-border membrane, interacting differentially with various peptidases, and responding to the dynamic needs of nutrient absorption in the intestine and kidney.

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