scholarly journals Characterization of the apicomplexan amino acid transporter (ApiAT) family inToxoplasma gondii

2018 ◽  
Author(s):  
Kathryn E. R. Parker ◽  
Stephen J. Fairweather ◽  
Esther Rajendran ◽  
Martin Blume ◽  
Malcolm J. McConville ◽  
...  
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Amino Acid ◽  
Toxoplasma Gondii ◽  
Amino Acid Transporters ◽  
Apicomplexan Parasites ◽  
Large Neutral Amino Acids ◽  
Neutral Amino Acids ◽  
The Family

AbstractApicomplexan parasites are auxotrophic for a range of amino acids which must be salvaged from their host cells, either through direct uptake or degradation of host proteins. Here, we describe a family of plasma membrane-localized amino acid transporters, termed the Apicomplexan Amino acid Transporters (ApiATs), that are ubiquitous in apicomplexan parasites. Functional characterization of the ApiATs ofToxoplasma gondiiindicate that several of these transporters are important for intracellular growth of the tachyzoite stage of the parasite, which is responsible for acute infections. We demonstrate that the ApiAT proteinTgApiAT5-3 is an exchanger for aromatic and large neutral amino acids, with particular importance for L-tyrosine scavenging and amino acid homeostasis, and thatTgApiAT5-3 is critical for parasite virulence. Our data indicate thatT. gondiiexpresses additional proteins involved in the uptake of aromatic amino acids, and we present a model for the uptake and homeostasis of these amino acids. Our findings identify a family of amino acid transporters in apicomplexans, and highlight the importance of amino acid scavenging for the biology of this important phylum of intracellular parasites.Author SummaryThe Apicomplexa comprise a large number of parasitic protozoa that have obligate intracellular lifestyles and cause significant human and animal diseases, including malaria, cryptosporidiosis, toxoplasmosis, coccidiosis in poultry, and various cattle fevers. Apicomplexans must scavenge essential nutrients from their hosts in order to proliferate and cause disease, including a range of amino acids. The direct uptake of these nutrients is presumed to be mediated by transporter proteins located in the plasma membrane of intracellular stages, although the identities of these proteins are poorly defined. Using a combination of bioinformatic, genetic, cell biological, and physiological approaches, we have characterized a family of plasma membrane-localized transporter proteins that we have called the Apicomplexan Amino acid Transporters (ApiATs). The family is found in apicomplexans and their closest free-living relatives. We show thatTgApiAT5-3, a member of the family in the apicomplexanToxoplasma gondii, is an exchanger for aromatic and large neutral amino acids. In particular, it is critical for uptake of tyrosine, and for parasite virulence in a mouse infection model. We conclude that ApiATs are a family of plasma membrane transporters that play crucial roles in amino acid scavenging by apicomplexan parasites.

Regulation of Amino Acid Influx and Efflux at the Basolateral Plasma Membrane of the Salivary Gland Epithelium: Effects of Parasympathetic Nerve Stimulation

1987 ◽  
Vol 66 (2) ◽  
pp. 569-575 ◽  
Author(s):  
G.E. Mann ◽  
D.L. Yudilevich
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Amino Acid ◽  
Nerve Stimulation ◽  
Transport Systems ◽  
Acid Uptake ◽  
Parasympathetic Nerve ◽  
Large Neutral Amino Acids ◽  
Neutral Amino Acids ◽  
Basolateral Plasma Membrane

Basolateral amino acid transport systems in the salivary epithelium of resting and secreting cat submandibular glands were characterized by means of a rapid paired-tracer dilution technique. Amino acid uptake was measured by comparison of venous tracer concentration profiles for a labeled amino acid and D-mannitol (an extracellular tracer of similar size) following an intra-arterial bolus injection of both radioactive molecules. Unidirectional uptake of 21 amino acids, dopamine, noradrenaline, and serotonin was quantified in non-secreting glands. During 8 Hz parasympathetic nerve stimulation, significant epithelial uptakes were measured for L-[3H] alanine and L-[3H] phenylalanine, but less than 0.2% of the injected amino acid was recovered in the collected saliva. In non-secreting glands, cross-inhibition studies of L-[3H] alanine, L-[3H] phenylalanine, and L-[3H] lysine uptake by unlabeled amino acid competitors and detailed kinetic influx experiments indicated that epithelial uptake was mediated by three distinct parallel transport systems: ASC (short-chain neutral), L (branched-chain and aromatic neutral), and y+ (cationic). Rapid metabolism of alanine was inhibited by aminooxyacetate, and the metabolic uncoupler dinitrophenol selectively accelerated the efflux of transported large neutral amino acids and L-lysine. Concurrent autoradiographic experiments suggest that transport sites for small and large neutral amino acids are localized in the basolateral plasma membrane of acinar, demilunar, and striated ductal cells.

scholarly journals Characterization of apicomplexan amino acid transporters (ApiATs) in the malaria parasite Plasmodium falciparum

2021 ◽  
Author(s):  
Jan Stephan Wichers ◽  
Carolina van Gelder ◽  
Gwendolin Fuchs ◽  
Julia Mareike Ruge ◽  
Emma Pietsch ◽  
...  
Keyword(s):  
Amino Acids ◽  
Plasmodium Falciparum ◽  
Plasma Membrane ◽  
Amino Acid ◽  
Host Cell ◽  
Amino Acid Transporters ◽  
Asexual Parasite ◽  
Malaria Parasites ◽  
Functional Inactivation ◽  
Uptake Of Nutrients

ABSTRACTDuring the symptomatic human blood phase, malaria parasites replicate within red blood cells. Parasite proliferation relies on the uptake of nutrients, such as amino acids, from the host cell and the blood plasma, requiring transport across multiple membranes. Amino acids are delivered to the parasite through the parasite surrounding vacuolar compartment by specialized nutrient-permeable channels of the erythrocyte membrane and the parasitophorous vacuole membrane (PVM). However, further transport of amino acid across the parasite plasma membrane (PPM) is currently not well characterized. In this study, we focused on a family of Apicomplexan amino acid transporters (ApiATs) that comprises five members in Plasmodium falciparum. First, we localized four of the PfApiATs at the PPM using endogenous GFP-tagging. Next, we applied reverse genetic approaches to probe into their essentiality during asexual replication and gametocytogenesis. Upon inducible knockdown and targeted gene disruption a reduced asexual parasite proliferation was detected for PfApiAT2 and PfApiAT4. Functional inactivation of individual PfApiATs targeted in this study had no effect on gametocyte development. Our data suggest that individual PfApiATs are partially redundant during asexual in vitro proliferation and fully redundant during gametocytogenesis of P. falciparum parasites.IMPORTANCEMalaria parasites live and multiply inside cells. To facilitate their extremely fast intracellular proliferation they hijack and transform their host cells. This also requires the active uptake of nutrients, such as amino acids, from the host cell and the surrounding environment through various membranes that are the consequence of the parasite’s intracellular lifestyle. In this manuscript we focus on a family of putative amino acid transporters termed ApiAT. We show expression and localization of four transporters in the parasite plasma membrane of Plasmodium falciparum-infected erythrocytes that represent one interface of the pathogen to its host cell. We probed into the impact of functional inactivation of individual transporters on parasite growth in asexual and sexual blood stages of P. falciparum and reveal that only two of them show a modest but significant reduction in parasite proliferation but no impact on gametocytogenesis pointing towards redundancy within this transporter family.

Stimulated amino acid imbalance and histidine transport in rat brain slices

1975 ◽  
Vol 229 (1) ◽  
pp. 229-234 ◽  
Author(s):  
J Lutz ◽  
JK Tews ◽  
AE Harper
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Brain Slices ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Large Neutral Amino Acids ◽  
Neutral Amino Acids ◽  
Low Protein ◽  
Amino Acid Imbalance ◽  
The Brain

Histidine concentration in the brain decreases rapidly when rats are fed a low protein diet in which an amino acid imbalance is created by addition of an amino acid mixture devoid of histidine. Competition for histidine transport into the brain was suggested as an explanation for this effect. Therefore, animo acid mixtures simulating composition of plasma from rats fed basal or histidine-imbalanced diets were added to media to evaluate their effects on uptake of histidine by brain slices during a 60-min incubation period. At the concentrations actually found in plasma, the unbalanced mixture decreased histidine uptake significantly more than did the basal mixture. Two distinct inhibition patterns were observed with different groups of amino acids: a linear decrease in histidine uptake with a mixture of the small neutral, hydroxyl, basic, and acidic amino acids, and a hyperbolic decrease with a mixture of large neutral amino acids, and a hyperbolic decrease with a mixture of large neutral amino acids. Inhibition of histidine transport by the complete mixtures reflected these two effects. Plasma patterns and concentrations of competitive amino acids as well as the concentration of histidine appear to be factors involved in decreasing histidine transport into the brain.

scholarly journals The zebrafish cationic amino acid transporter/glycoprotein-associated family: sequence and spatiotemporal distribution during development of the transport system b0,+ (slc3a1/slc7a9)

2021 ◽  
Author(s):  
Ståle Ellingsen ◽  
Shailesh Narawane ◽  
Anders Fjose ◽  
Tiziano Verri ◽  
Ivar Rønnestad
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Transport System ◽  
Expression Patterns ◽  
Amino Acid Transporter ◽  
Rapid Screening ◽  
Cationic Amino Acid ◽  
Large Neutral Amino Acids ◽  
Neutral Amino Acids ◽  
Acid Transporter

AbstractSystem b0,+ absorbs lysine, arginine, ornithine, and cystine, as well as some (large) neutral amino acids in the mammalian kidney and intestine. It is a heteromeric amino acid transporter made of the heavy subunit SLC3A1/rBAT and the light subunit SLC7A9/b0,+AT. Mutations in these two genes can cause cystinuria in mammals. To extend information on this transport system to teleost fish, we focused on the slc3a1 and slc7a9 genes by performing comparative and phylogenetic sequence analysis, investigating gene conservation during evolution (synteny), and defining early expression patterns during zebrafish (Danio rerio) development. Notably, we found that slc3a1 and slc7a9 are non-duplicated in the zebrafish genome. Whole-mount in situ hybridization detected co-localized expression of slc3a1 and slc7a9 in pronephric ducts at 24 h post-fertilization and in the proximal convoluted tubule at 3 days post-fertilization (dpf). Notably, both the genes showed co-localized expression in epithelial cells in the gut primordium at 3 dpf and in the intestine at 5 dpf (onset of exogenous feeding). Taken together, these results highlight the value of slc3a1 and slc7a9 as markers of zebrafish kidney and intestine development and show promise for establishing new zebrafish tools that can aid in the rapid screening(s) of substrates. Importantly, such studies will help clarify the complex interplay between the absorption of dibasic amino acids, cystine, and (large) neutral amino acids and the effect(s) of such nutrients on organismal growth.

Na+-dependent transport of large neutral amino acids occurs at the abluminal membrane of the blood-brain barrier

2003 ◽  
Vol 285 (6) ◽  
pp. E1167-E1173 ◽  
Author(s):  
Robyn L. O'Kane ◽  
Richard A. Hawkins
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Blood Brain Barrier ◽  
Basement Membranes ◽  
Brain Barrier ◽  
Large Neutral Amino Acid ◽  
Large Neutral Amino Acids ◽  
Neutral Amino Acids ◽  
Blood Brain ◽  
Dependent Transport

Several Na+-dependent carriers of amino acids exist on the abluminal membrane of the blood-brain barrier (BBB). These Na+-dependent carriers are in a position to transfer amino acids from the extracellular fluid of brain to the endothelial cells and thence to the circulation. To date, carriers have been found that may remove nonessential, nitrogen-rich, or acidic (excitatory) amino acids, all of which may be detrimental to brain function. We describe here Na+-dependent transport of large neutral amino acids across the abluminal membrane of the BBB that cannot be ascribed to currently known systems. Fresh brains, from cows killed for food, were used. Microvessels were isolated, and contaminating fragments of basement membranes, astrocyte fragments, and pericytes were removed. Abluminal-enriched membrane fractions from these microvessels were prepared. Transport was Na+dependent, voltage sensitive, and inhibited by 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid, a particular inhibitor of the facilitative large neutral amino acid transporter 1 (LAT1) system. The carrier has a high affinity for leucine ( Km21 ± 7 μM) and is inhibited by other neutral amino acids, including glutamine, histidine, methionine, phenylalanine, serine, threonine, tryptophan, and tyrosine. Other established neutral amino acids may enter the brain by way of LAT1-type facilitative transport. The presence of a Na+-dependent carrier on the abluminal membrane capable of removing large neutral amino acids, most of which are essential, from brain indicates a more complex situation that has implications for the control of essential amino acid content of brain.

scholarly journals Distribution Volume of Radiolabeled Large Neutral Amino Acids in Brain Tissue

1998 ◽  
Vol 18 (12) ◽  
pp. 1288-1293 ◽  
Author(s):  
Sung-Cheng Huang ◽  
David B. Stout ◽  
Randa E. Yee ◽  
Nagichettiar Satyamurthy ◽  
Jorge R. Barrio
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Brain Tissue ◽  
Blood Brain Barrier ◽  
Distribution Volume ◽  
Neutral Amino Acid ◽  
Large Neutral Amino Acid ◽  
Large Neutral Amino Acids ◽  
Neutral Amino Acids ◽  
Amino Acid Levels

Variations in the cerebellum to plasma ratio at late times in 6-[18F]fluoro-l-DOPA studies are shown to be consistent with competitive binding of large neutral amino acids for a common transporter in the blood—brain barrier and the stability of brain tissue large neutral amino acid level in the presence of plasma level changes. The distribution volume of an inert large neutral amino acid can be estimated from plasma and tissue large neutral amino acid levels and apparent half-saturation concentrations ( Km) of the transporter in the blood—brain barrier. Stability of brain large neutral amino acid levels is supported by literature findings and can be explained by high saturation of the large neutral amino acid transporter at physiologic conditions.

scholarly journals Ssy1p and Ptr3p Are Plasma Membrane Components of a Yeast System That Senses Extracellular Amino Acids

1999 ◽  
Vol 19 (8) ◽  
pp. 5405-5416 ◽  
Author(s):  
Hanna Klasson ◽  
Gerald R. Fink ◽  
Per O. Ljungdahl
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Amino Acid ◽  
Genetic Selection ◽  
Functional Expression ◽  
Subcellular Fractionation ◽  
Peptide Transporter ◽  
Amino Acid Transporters ◽  
Amino Acid Permease ◽  
Membrane Components

ABSTRACT Mutations in SSY1 and PTR3 were identified in a genetic selection for components required for the proper uptake and compartmentalization of histidine in Saccharomyces cerevisiae. Ssy1p is a unique member of the amino acid permease gene family, and Ptr3p is predicted to be a hydrophilic protein that lacks known functional homologs. Both Ssy1p and Ptr3p have previously been implicated in relaying signals regarding the presence of extracellular amino acids. We have found that ssy1 andptr3 mutants belong to the same epistasis group; single andssy1 ptr3 double-mutant strains exhibit indistinguishable phenotypes. Mutations in these genes cause the nitrogen-regulated general amino acid permease gene (GAP1) to be abnormally expressed and block the nonspecific induction of arginase (CAR1) and the peptide transporter (PTR2).ssy1 and ptr3 mutations manifest identical differential effects on the functional expression of multiple specific amino acid transporters. ssy1 and ptr3 mutants have increased vacuolar pools of histidine and arginine and exhibit altered cell growth morphologies accompanied by exaggerated invasive growth. Subcellular fractionation experiments reveal that both Ssy1p and Ptr3p are localized to the plasma membrane (PM). Ssy1p requires the endoplasmic reticulum protein Shr3p, the amino acid permease-specific packaging chaperonin, to reach the PM, whereas Ptr3p does not. These findings suggest that Ssy1p and Ptr3p function in the PM as components of a sensor of extracellular amino acids.

scholarly journals Expression Cloning and Characterization of a Transporter for Large Neutral Amino Acids Activated by the Heavy Chain of 4F2 Antigen (CD98)

1998 ◽  
Vol 273 (37) ◽  
pp. 23629-23632 ◽  
Author(s):  
Yoshikatsu Kanai ◽  
Hiroko Segawa ◽  
Ken-ichi Miyamoto ◽  
Hiroshi Uchino ◽  
Eiji Takeda ◽  
...  
Keyword(s):  
Amino Acids ◽  
Heavy Chain ◽  
Expression Cloning ◽  
Large Neutral Amino Acids ◽  
Neutral Amino Acids

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

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.

scholarly journals SLC36 family of proton-coupled amino acid transporters (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

2019 ◽  
Vol 2019 (4) ◽  
Author(s):  
Catriona M.H. Anderson ◽  
David T. Thwaites
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Amino Acid ◽  
Expression Patterns ◽  
Cell Types ◽  
Tissue Expression ◽  
Amino Acid Transporters ◽  
Beige Adipocytes ◽  
Mtorc1 Pathway ◽  
Amino Acids And Derivatives

Members of the SLC36 family of proton-coupled amino acid transporters are involved in membrane transport of amino acids and derivatives. The four transporters show variable tissue expression patterns and are expressed in various cell types at the plasma-membrane and in intracellular organelles. PAT1 is expressed at the luminal surface of the small intestine and absorbs amino acids and derivatives [3]. In lysosomes, PAT1 functions as an efflux mechanism for amino acids produced during intralysosomal proteolysis [2, 15]. PAT2 is expressed at the apical membrane of the renal proximal tubule [5] and at the plasma-membrane in brown/beige adipocytes [17]. PAT1 and PAT4 are involved in regulation of the mTORC1 pathway [8]. More comprehensive lists of substrates can be found within the reviews under Further Reading and in the references.

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