Transporters for Cationic Amino Acids in Animal Cells: Discovery, Structure, and Function

Devés, R., and C. A. R. Boyd. Transporters for Cationic Amino Acids in Animal Cells: Discovery, Structure, and Function. Physiol. Rev. 78: 487–545, 1998. — The structure and function of the four cationic amino acid transporters identified in animal cells are discussed. The systems differ in specificity, cation dependence, and physiological role. One of them, system y+, is selective for cationic amino acids, whereas the others (B0,+, b0,+, and y+L) also accept neutral amino acids. In recent years, cDNA clones related to these activities have been isolated. Thus two families of proteins have been identified: 1) CAT or cationic amino acid transporters and 2) BAT or broad-scope transport proteins. In the CAT family, three genes encode for four different isoforms [CAT-1, CAT-2A, CAT-2(B) and CAT-3]; these are ∼70-kDa proteins with multiple transmembrane segments ( 12 – 14 ), and despite their structural similarity, they differ in tissue distribution, kinetics, and regulatory properties. System y+is the expression of the activity of CAT transporters. The BAT family includes two isoforms (rBAT and 4F2hc); these are 59- to 78-kDa proteins with one to four membrane-spanning segments, and it has been proposed that these proteins act as transport regulators. The expression of rBAT and 4F2hc induces system b0,+and system y+L activity in Xenopus laevis oocytes, respectively. The roles of these transporters in nutrition, endocrinology, nitric oxide biology, and immunology, as well as in the genetic diseases cystinuria and lysinuric protein intolerance, are reviewed. Experimental strategies, which can be used in the kinetic characterization of coexpressed transporters, are also discussed.

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Structure and Function of Cationic Amino Acid Transporters (CATs)

The Journal of Membrane Biology ◽

10.1007/s00232-006-0875-7 ◽

2006 ◽

Vol 213 (2) ◽

pp. 67-77 ◽

Cited By ~ 143

Author(s):

E.I. Closs ◽

J.-P. Boissel ◽

A. Habermeier ◽

A. Rotmann

Keyword(s):

Amino Acid ◽

Structure And Function ◽

Amino Acid Transporters ◽

Cationic Amino Acid ◽

And Function

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Coordinated Action of Multiple Transporters in the Acquisition of Essential Cationic Amino Acids by the Intracellular Parasite Toxoplasma gondii

10.1101/2021.06.25.450001 ◽

2021 ◽

Author(s):

Stephen J Fairweather ◽

Esther Rajendran ◽

Martin Blume ◽

Kiran Javed ◽

Birte Steinhoefel ◽

...

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Toxoplasma Gondii ◽

Large Family ◽

Essential Amino Acids ◽

Amino Acid Transporters ◽

Cationic Amino Acid ◽

Intracellular Parasites ◽

Cationic Amino Acids ◽

High Concentrations

Intracellular parasites of the phylum Apicomplexa are dependent on the scavenging of essential amino acids from their hosts. We previously identified a large family of apicomplexan-specific plasma membrane-localized amino acid transporters, the ApiATs, and showed that the Toxoplasma gondii transporter TgApiAT1 functions in the selective uptake of arginine. TgApiAT1 is essential for parasite virulence, but dispensable for parasite growth in medium containing high concentrations of arginine, indicating the presence of at least one other arginine transporter. Here we identify TgApiAT6-1 as the second arginine transporter. Using a combination of parasite assays and heterologous characterisation of TgApiAT6-1 in Xenopus laevis oocytes, we demonstrate that TgApiAT6-1 is a general cationic amino acid transporter that mediates both the high-affinity uptake of lysine and the low-affinity uptake of arginine. TgApiAT6-1 is the primary lysine transporter in the disease-causing tachyzoite stage of T. gondii and is essential for parasite proliferation. We demonstrate that the uptake of cationic amino acids by TgApiAT6-1 is "trans-stimulated" by cationic and neutral amino acids and is likely promoted by an inwardly negative membrane potential. These findings demonstrate that T. gondii has evolved overlapping transport mechanisms for the uptake of essential cationic amino acids, and we draw together our findings into a comprehensive model that highlights the finely-tuned, regulated processes that mediate cationic amino acid scavenging by these intracellular parasites.

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Coordinated action of multiple transporters in the acquisition of essential cationic amino acids by the intracellular parasite Toxoplasma gondii

PLoS Pathogens ◽

10.1371/journal.ppat.1009835 ◽

2021 ◽

Vol 17 (8) ◽

pp. e1009835

Author(s):

Stephen J. Fairweather ◽

Esther Rajendran ◽

Martin Blume ◽

Kiran Javed ◽

Birte Steinhöfel ◽

...

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Toxoplasma Gondii ◽

Large Family ◽

Essential Amino Acids ◽

Amino Acid Transporters ◽

Cationic Amino Acid ◽

Intracellular Parasites ◽

Cationic Amino Acids ◽

High Concentrations

Intracellular parasites of the phylum Apicomplexa are dependent on the scavenging of essential amino acids from their hosts. We previously identified a large family of apicomplexan-specific plasma membrane-localized amino acid transporters, the ApiATs, and showed that the Toxoplasma gondii transporter TgApiAT1 functions in the selective uptake of arginine. TgApiAT1 is essential for parasite virulence, but dispensable for parasite growth in medium containing high concentrations of arginine, indicating the presence of at least one other arginine transporter. Here we identify TgApiAT6-1 as the second arginine transporter. Using a combination of parasite assays and heterologous characterisation of TgApiAT6-1 in Xenopus laevis oocytes, we demonstrate that TgApiAT6-1 is a general cationic amino acid transporter that mediates both the high-affinity uptake of lysine and the low-affinity uptake of arginine. TgApiAT6-1 is the primary lysine transporter in the disease-causing tachyzoite stage of T. gondii and is essential for parasite proliferation. We demonstrate that the uptake of cationic amino acids by TgApiAT6-1 is ‘trans-stimulated’ by cationic and neutral amino acids and is likely promoted by an inwardly negative membrane potential. These findings demonstrate that T. gondii has evolved overlapping transport mechanisms for the uptake of essential cationic amino acids, and we draw together our findings into a comprehensive model that highlights the finely-tuned, regulated processes that mediate cationic amino acid scavenging by these intracellular parasites.

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Amino acid sequence of the encephalitogenic basic protein from human myelin

Biochemical Journal ◽

10.1042/bj1230057 ◽

1971 ◽

Vol 123 (1) ◽

pp. 57-67 ◽

Cited By ~ 182

Author(s):

P. R. Carnegie

Keyword(s):

Amino Acids ◽

Central Nervous System ◽

Nervous System ◽

Amino Acid ◽

Basic Protein ◽

Structure And Function ◽

Autoimmune Encephalomyelitis ◽

The Central Nervous System ◽

And Function ◽

Experimental Autoimmune

Myelin from the central nervous system contains an unusual basic protein, which can induce experimental autoimmune encephalomyelitis. The basic protein from human brain was digested with trypsin and other enzymes and the sequence of the 170 amino acids was determined. The localization of the encephalitogenic determinants was described. Possible roles for the protein in the structure and function of myelin are discussed.

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Na(+)-independent transport (uniport) of amino acids and glucose in mammalian cells.

Journal of Experimental Biology ◽

10.1242/jeb.196.1.93 ◽

1994 ◽

Vol 196 (1) ◽

pp. 93-108

Author(s):

D K Kakuda ◽

C L MacLeod

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Mammalian Cells ◽

Glucose Transporter ◽

Sequence Similarity ◽

Amino Acid Sequence Similarity ◽

Amino Acid Transporters ◽

Cationic Amino Acid ◽

Transporter Family ◽

Share Amino Acid Sequence

Recent advances have made possible the isolation of the genes and their cDNAs encoding Na(+)-independent amino acid transporters. Two classes of amino acid 'uniporters' have been isolated. One class contains the mCAT (murine cationic amino acid transporter) gene family that encodes proteins predicted to span the membrane 12-14 times and exhibits structural properties similar to the GLUT (glucose transporter) family and to other well-known transporters. The other class consists of two known genes, rBAT (related to B system amino acid transporters) and 4F2hc, that share amino acid sequence similarity with alpha-amylases and alpha-glucosidases. They are type II glycoproteins predicted to span the membrane only once, yet they mediate the Na(+)-independent transport of cationic and zwitterionic amino acids in Xenopus oocytes. Mutations in the human rBAT gene have been identified by Palacín and his co-workers in several families suffering from a heritable form of cystinuria. This important finding clearly establishes a key role for rBAT in cystine transport. The two classes of amino acid transporters are compared with the well-studied GLUT family of Na(+)-independent glucose transporters.

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Amino-acid-dependent modulation of amino acid transport in Xenopus laevis oocytes.

Journal of Experimental Biology ◽

10.1242/jeb.199.4.923 ◽

1996 ◽

Vol 199 (4) ◽

pp. 923-931 ◽

Cited By ~ 2

Author(s):

P M Taylor ◽

S Kaur ◽

B Mackenzie ◽

G J Peter

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Xenopus Laevis ◽

Amino Acid Transport ◽

Acid Mixture ◽

Xenopus Laevis Oocytes ◽

Amino Acid Transporters ◽

Amino Acid Supplementation ◽

Acid Transport ◽

Acid Supplementation

We have measured rates of uptake of arginine, glutamine, glutamate, serine, phenylalanine and glycine in Xenopus laevis oocytes cultured for periods of up to 24h in saline in the presence or absence of a mixture of 20 amino acids at concentrations approximating those in Xenopus plasma. Amino acid supplementation increased the total intracellular amino acid concentration from 8.2 to 18.4 nmol per oocyte. Specific Na(+)-dependent amino acid transporters (systems B0,+, Xag-) exhibit 'adaptive regulation' (up-regulation during amino acid deprivation and down-regulation during amino acid supplementation). Na(+)-independent transporters of glutamate, glutamine and glycine (including system asc) display an opposite modulation in activity, which may help to combat amino-acid-induced oxidative stress by increasing the supply of glutathione precursors. Single amino acids at physiological plasma concentrations (0.47 mmol l-1 L-alanine, 0.08 mmol l-1 L-glutamate) mimicked at least some effects of the amino acid mixture. The mechanisms of transport modulation do not appear to include trans-amino acid or membrane potential effects and, in the case of Na(+)-independent transport, are independent of protein or mRNA synthesis. Furthermore, activation of protein kinase C by phorbol 12-myristate 13-acetate did not significantly affect endogenous glutamine and glutamate transport. The Xenopus oocyte appears to possess endogenous signalling mechanisms for selectively modulating the activity of amino acid transport proteins expressed in its surface membranes, a factor for consideration when using oocytes as an expression system for structure-function studies of cloned amino acid transporters.

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The heterodimeric amino acid transporter 4F2hc/y+LAT2 mediates arginine efflux in exchange with glutamine

Biochemical Journal ◽

10.1042/bj3490787 ◽

2000 ◽

Vol 349 (3) ◽

pp. 787-795 ◽

Cited By ~ 134

Author(s):

Angelika BRÖER ◽

Carsten A. WAGNER ◽

Florian LANG ◽

Stefan BRÖER

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Mammalian Cells ◽

Substrate Inhibition ◽

Cell Types ◽

Xenopus Laevis Oocytes ◽

Cationic Amino Acid ◽

New Family ◽

Arginine Uptake ◽

Intracellular Binding

The cationic amino acid arginine, due to its positive charge, is usually accumulated in the cytosol. Nevertheless, arginine has to be released by a number of cell types, e.g. kidney cells, which supply other organs with this amino acid, or the endothelial cells of the blood–brain barrier which release arginine into the brain. Arginine release in mammalian cells can be mediated by two different transporters, y+LAT1 and y+LAT2. For insertion into the plasma membrane, these transporters have to be associated with the type-II membrane glycoprotein 4F2hc [Torrents, Estevez, Pineda, Fernandez, Lloberas, Shi, Zorzano and Palacin (1998) J. Biol. Chem. 273, 32437–32445]. The present study elucidates the function and distribution of y+LAT2. In contrast to y+LAT1, which is expressed mainly in kidney epithelial cells, lung and leucocytes, y+LAT2 has a wider tissue distribution, including brain, heart, testis, kidney, small intestine and parotis. When co-expressed with 4F2hc in Xenopus laevis oocytes, y+LAT2 mediated uptake of arginine, leucine and glutamine. Arginine uptake was inhibited strongly by lysine, glutamate, leucine, glutamine, methionine and histidine. Mutual inhibition was observed when leucine or glutamine was used as substrate. Inhibition of arginine uptake by neutral amino acids depended on the presence of Na+, which is a hallmark of y+LAT-type transporters. Although arginine transport was inhibited strongly by glutamate, this anionic amino acid was only weakly transported by 4F2hc/y+LAT2. Amino acid transport via 4F2hc/y+LAT2 followed an antiport mechanism similar to the other members of this new family. Only preloaded arginine could be released in exchange for extracellular amino acids, whereas marginal release of glutamine or leucine was observed under identical conditions. These results indicated that arginine has the highest affinity for the intracellular binding site and that arginine release may be the main physiological function of this transporter.

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60 YEARS OF POMC: Lipotropin and beta-endorphin: a perspective

Journal of Molecular Endocrinology ◽

10.1530/jme-16-0033 ◽

2016 ◽

Vol 56 (4) ◽

pp. T13-T25 ◽

Cited By ~ 10

Author(s):

D G Smyth

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Amino Acid Analysis ◽

Structure And Function ◽

Biologically Active ◽

Molecular Endocrinology ◽

And Function ◽

The Brain ◽

Quantitative Amino Acid Analysis

Many important fields of research had a humble origin. In the distant past, A J P Martin’s discovery that amino acids could be separated by paper chromatography and Moore and Stein’s use of columns for quantitative amino acid analysis provided the first steps towards the determination of structure in complex biologically active molecules. They opened the door to reveal the essential relationship that exists between structure and function. In molecular endocrinology, for example, striking advances have been made by chemists with their expertise in the identification of structure working with biologists who contributed valuable knowledge and experience. Advantage was gained from the convergence of different background, and it is notable that the whole is greater than the sum. In the determination of structure, it may be recalled that four of the world’s great pioneers (Archibald Martin, Rodney Porter, Fred Sanger and Vincent du Vigneaud) were acknowledged for their fundamental contributions when individually they were awarded the Nobel Prize. They foresaw that the identification of structure would prove of outstanding importance in the future. Indeed, study of the structures of β-endorphin and enkephalin and the different forms of opiate activity they engender has led to a transformation in our understanding of chemical transmission in the brain.

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A GC-MS/Single-Cell Method to Evaluate Membrane Transporter Substrate Specificity and Signaling

Frontiers in Molecular Biosciences ◽

10.3389/fmolb.2021.646574 ◽

2021 ◽

Vol 8 ◽

Author(s):

Stephen J. Fairweather ◽

Shoko Okada ◽

Gregory Gauthier-Coles ◽

Kiran Javed ◽

Angelika Bröer ◽

...

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Substrate Specificity ◽

Signaling Pathways ◽

Intracellular Signaling ◽

Vital Role ◽

Cellular Growth ◽

Amino Acid Transporters ◽

Cationic Amino Acids ◽

Nutrient Signaling

Amino acid transporters play a vital role in metabolism and nutrient signaling pathways. Typically, transport activity is investigated using single substrates and competing amounts of other amino acids. We used GC-MS and LC-MS for metabolic screening of Xenopus laevis oocytes expressing various human amino acid transporters incubated in complex media to establish their comprehensive substrate profiles. For most transporters, amino acid selectivity matched reported substrate profiles. However, we could not detect substantial accumulation of cationic amino acids by SNAT4 and ATB0,+ in contrast to previous reports. In addition, comparative substrate profiles of two related sodium neutral amino acid transporters known as SNAT1 and SNAT2, revealed the latter as a significant leucine accumulator. As a consequence, SNAT2, but not SNAT1, was shown to be an effective activator of the eukaryotic cellular growth regulator mTORC1. We propose, that metabolomic profiling of membrane transporters in Xenopus laevis oocytes can be used to test their substrate specificity and role in intracellular signaling pathways.

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