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

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.

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.

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

1998 ◽  
Vol 78 (2) ◽  
pp. 487-545 ◽  
Author(s):  
R. DEVÉS ◽  
C. A. R. BOYD
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Structure And Function ◽  
Xenopus Laevis Oocytes ◽  
Amino Acid Transporters ◽  
Cdna Clones ◽  
Animal Cells ◽  
Cationic Amino Acid ◽  
Cationic Amino Acids ◽  
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.

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

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.

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

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.

ESSENTIAL AMINO ACIDS IN MICROORGANISMS

1957 ◽  
Vol 3 (5) ◽  
pp. 721-728 ◽  
Author(s):  
F. Reusser ◽  
J. F. T. Spencer ◽  
H. R. Sallans
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Quantitative Method ◽  
Essential Amino Acids ◽  
Cellular Protein ◽  
One Dimensional ◽  
Low Concentrations ◽  
Amino Acid Determination ◽  
High Concentrations ◽  
Acid Determination

The cells of 19 species of bacteria, actinomyces, and yeasts were analyzed for protein and essential amino acids. A rapid quantitative method for amino acid determination using one-dimensional paper chromatography was developed. The cellular protein from all species contained relatively high concentrations of lysine, somewhat lower concentrations of tryptophan and threonine, and very low concentrations of methionine. All of the 10 essential amino acids were found in each species tested, although individual differences in the relative and absolute amounts were observed.

scholarly journals Supplemental leucine and isoleucine affect expression of cationic amino acid transporters and myosin, serum concentration of amino acids, and growth performance of pigs

2013 ◽  
Vol 12 (1) ◽  
pp. 115-126 ◽  
Author(s):  
M. Cervantes-Ramírez ◽  
V. Mendez-Trujillo ◽  
B.A. Araiza-Piña ◽  
M.A. Barrera-Silva ◽  
D. González-Mendoza ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Serum Concentration ◽  
Growth Performance ◽  
Amino Acid Transporters ◽  
Cationic Amino Acid ◽  
Affect Expression

Cis-inhibition and trans-stimulation of cationic amino acid transport in the perfused rat pancreas

1991 ◽  
Vol 261 (3) ◽  
pp. C506-C514 ◽  
Author(s):  
J. H. Sweiry ◽  
M. Munoz ◽  
G. E. Mann
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Maximum Velocity ◽  
Isobutyric Acid ◽  
Perfused Rat Pancreas ◽  
Cultured Fibroblasts ◽  
Rat Pancreas ◽  
Dual Isotope ◽  
Cationic Amino Acid ◽  
Cationic Amino Acids

Transport of cationic amino acids in the isolated perfused rat pancreas was studied using dual-isotope dilution techniques. At 50 microM substrate concentration, unidirectional tracer uptakes for L-arginine (56 +/- 1%), L-lysine (49 +/- 2%), and L-ornithine (44 +/- 3%) were followed by rapid tracer efflux. In the presence of Na+, influx of L-arginine [Michaelis constant (Km) = 1.74 +/- 0.15 mM, maximum velocity (Vmax) = 1.97 +/- 0.07 mumol.min-1.g-1] and L-lysine (Km = 2.48 +/- 0.17 mM, Vmax = 2.42 +/- 0.08 mumol.min-1.g-1) was mediated by a common transport system, sensitive to cis-inhibition by L-ornithine, 2,4-L-diaminobutyric acid, D-lysine, and D-arginine. Substrates for system A [alpha-(methylamino)isobutyric acid] and an anionic carrier (L-aspartate) were poor cis-inhibitors of L-arginine entry. Removal of Na+ resulted in a 40% reduction in cationic amino acid influx. After cell loading (20 min), L-[3H]-lysine cleared predominantly from a slowly exchanging pool with a rate constant of 5.97 +/- 0.67 min. An influx/efflux permeability ratio of 14.5 +/- 1.6 was determined, and efflux of L-lysine was trans-stimulated by vascular challenges with cationic or large neutral amino acids. The specificity, relative Na+ independence, and exchange properties of this saturable cationic amino acid transporter in the pancreatic epithelium resemble those reported for system y+ in cultured fibroblasts and hepatocytes.

scholarly journals PQLC2 recruits the C9orf72 complex to lysosomes in response to cationic amino acid starvation

2019 ◽  
Vol 219 (1) ◽  
Author(s):  
Joseph Amick ◽  
Arun Kumar Tharkeshwar ◽  
Gabriel Talaia ◽  
Shawn M. Ferguson
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Starvation ◽  
Cationic Amino Acid Transporter ◽  
Cationic Amino Acid ◽  
Binding Partner ◽  
Sensing Mechanism ◽  
Cationic Amino Acids ◽  
Sense And Respond ◽  
Amino Acid Sensing

The C9orf72 protein is required for normal lysosome function. In support of such functions, C9orf72 forms a heterotrimeric complex with SMCR8 and WDR41 that is recruited to lysosomes when amino acids are scarce. These properties raise questions about the identity of the lysosomal binding partner of the C9orf72 complex and the amino acid–sensing mechanism that regulates C9orf72 complex abundance on lysosomes. We now demonstrate that an interaction with the lysosomal cationic amino acid transporter PQLC2 mediates C9orf72 complex recruitment to lysosomes. This is achieved through an interaction between PQLC2 and WDR41. The interaction between PQLC2 and the C9orf72 complex is negatively regulated by arginine, lysine, and histidine, the amino acids that PQLC2 transports across the membrane of lysosomes. These results define a new role for PQLC2 in the regulated recruitment of the C9orf72 complex to lysosomes and reveal a novel mechanism that allows cells to sense and respond to changes in the availability of cationic amino acids within lysosomes.

scholarly journals PQLC2 signals lysosomal cationic amino acid abundance to the C9orf72 complex

2019 ◽  
Author(s):  
Joseph Amick ◽  
Arun Kumar Tharkeshwar ◽  
Gabriel Talaia ◽  
Shawn M. Ferguson
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transporter ◽  
Cationic Amino Acid Transporter ◽  
Cationic Amino Acid ◽  
Binding Partner ◽  
Sensing Mechanism ◽  
Cationic Amino Acids ◽  
Sense And Respond ◽  
Amino Acid Sensing

AbstractThe C9orf72 protein is required for normal lysosome function. In support of such functions, C9orf72 forms a heterotrimeric complex with SMCR8 and WDR41 that is recruited to lysosomes when amino acids are scarce. These properties raise questions about the identity of the lysosomal binding partner of the C9orf72 complex and the amino acid sensing mechanism that regulates C9orf72 complex abundance on lysosomes. We now demonstrate that an interaction with the lysosomal cationic amino acid transporter PQLC2 mediates C9orf72 complex recruitment to lysosomes. This is achieved through an interaction between PQLC2 and WDR41. The interaction between PQLC2 and the C9orf72 complex is negatively regulated by arginine, lysine and histidine, amino acids that PQLC2 transports across the membrane of lysosomes. These results define a new role for PQLC2 in the regulated recruitment of the C9orf72 complex to lysosomes and reveal a novel mechanism that allows cells to sense and respond to changes in the availability of cationic amino acids within lysosomes.

scholarly journals Amino Acid Transporters as Targets for Cancer Therapy: Why, Where, When, and How

2020 ◽  
Vol 21 (17) ◽  
pp. 6156 ◽  
Author(s):  
Stefan Bröer
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cancer Cells ◽  
Cancer Cell ◽  
Synthetic Lethality ◽  
Protein Translation ◽  
Essential Amino Acids ◽  
Selective Vulnerability ◽  
Amino Acid Transporters ◽  
Knock Out

Amino acids are indispensable for the growth of cancer cells. This includes essential amino acids, the carbon skeleton of which cannot be synthesized, and conditionally essential amino acids, for which the metabolic demands exceed the capacity to synthesize them. Moreover, amino acids are important signaling molecules regulating metabolic pathways, protein translation, autophagy, defense against reactive oxygen species, and many other functions. Blocking uptake of amino acids into cancer cells is therefore a viable strategy to reduce growth. A number of studies have used genome-wide silencing or knock-out approaches, which cover all known amino acid transporters in a large variety of cancer cell lines. In this review, these studies are interrogated together with other databases to identify vulnerabilities with regard to amino acid transport. Several themes emerge, such as synthetic lethality, reduced redundancy, and selective vulnerability, which can be exploited to stop cancer cell growth.

Sign in / Sign up

Export Citation Format

Share Document