Multiple pathways for cationic amino acid transport in rat thyroid epithelial cell line PC Cl3

2005 ◽  
Vol 288 (2) ◽  
pp. C290-C303 ◽  
Author(s):  
Tiziano Verri ◽  
Cinzia Dimitri ◽  
Sonia Treglia ◽  
Fabio Storelli ◽  
Stefania De Micheli ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cell Line ◽  
Amino Acid Transport ◽  
Transport Systems ◽  
Residual Fraction ◽  
Acid Transport ◽  
Thyroid Cells ◽  
Cationic Amino Acid ◽  
Rat Thyroid

Information regarding cationic amino acid transport systems in thyroid is limited to Northern blot detection of y+LAT1 mRNA in the mouse. This study investigated cationic amino acid transport in PC cell line clone 3 (PC Cl3 cells), a thyroid follicular cell line derived from a normal Fisher rat retaining many features of normal differentiated follicular thyroid cells. We provide evidence that in PC Cl3 cells plasmalemmal transport of cationic amino acids is Na+ independent and occurs, besides diffusion, with the contribution of high-affinity, carrier-mediated processes. Carrier-mediated transport is via y+, y+L, and b0,+ systems, as assessed by l-arginine uptake and kinetics, inhibition of l-arginine transport by N-ethylmaleimide and neutral amino acids, and l-cystine transport studies. y+L and y+ systems account for the highest transport rate (with y+L > y+) and b0,+ for a residual fraction of the transport. Uptake data correlate to expression of the genes encoding for CAT-1, CAT-2B, 4F2hc, y+LAT1, y+LAT2, rBAT, and b0,+AT, an expression profile that is also shown by the rat thyroid gland. In PC Cl3 cells cationic amino acid uptake is under TSH and/or cAMP control (with transport increasing with increasing TSH concentration), and upregulation of CAT-1, CAT-2B, 4F2hc/y+LAT1, and rBAT/b0,+AT occurs at the mRNA level under TSH stimulation. Our results provide the first description of an expression pattern of cationic amino acid transport systems in thyroid cells. Furthermore, we provide evidence that extracellular l-arginine is a crucial requirement for normal PC Cl3 cell growth and that long-term l-arginine deprivation negatively influences CAT-2B expression, as it correlates to reduction of CAT-2B mRNA levels.

Amino Acid Transport in a Water-mould: The Possible Regulatory Roles of Calcium and N6-(Δ2-isopentenyl)adenine

1975 ◽  
Vol 53 (9) ◽  
pp. 975-988 ◽  
Author(s):  
Danny P. Singh ◽  
Hérb. B. LéJohn
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Osmotic Shock ◽  
Inhibitory Effect ◽  
Transport Systems ◽  
Acid Transport ◽  
Isopentenyl Adenine ◽  
Energy Dependent ◽  
Water Mould

Transport of amino acids in the water-mould Achlya is an energy-dependent process. Based on competition kinetics and studies involving the influence of pH and temperature on the initial transport rates, it was concluded that the 20 amino acids (L-isomers) commonly found in proteins were transported by more than one, possibly nine, uptake systems. This is similar to the pattern elucidated for some bacteria but unlike those uncovered for all fungi studied to date. The nine different transport systems elucidated are: (i) methionine, (ii) cysteine, (iii) proline, (iv) serine–threonine, (v) aspartic and glutamic acids, (vi) glutamine and asparagine, (vii) glycine and alanine, (viii) histidine, lysine, and arginine, and (ix) phenylalanine–tyrosine–tryptophan and leucine–isoleucine–valine as two overlapping groups. Transport of all of these amino acids was inhibited by azide, cyanide, and its derivatives and 2,4-dinitrophenol. These agents normally interfere with metabolism at the level of the electron transport chain and oxidative phosphorylation. Osmotic shock treatment of the cells released, into the shock fluid, a glycopeptide that binds calcium as well as tryptophan but no other amino acid. The shocked cells are incapable of concentrating amino acids, but remain viable and reacquire this capacity when the glycopeptide is resynthesized.Calcium played more than a secondary role in the transport of the amino acids. When bound to the membrane-localized glycopeptide, it permits concentrative transport to take place. However, excess calcium can inhibit transport which can be overcome by chelating with citrate. Calculations show that the concentration of free citrate is most important. At low citrate concentrations (less than 1 mM) in the absence of exogenously supplied calcium, enhancement of amino acid transport occurs. At high concentrations (greater than 5 mM), citrate inhibits but this effect can be reversed by titrating with calcium. Evidently, the glycopeptide acts as a calcium sink to regulate the concentration of calcium made available to the cell for its membrane activities.N6-(Δ2-isopentenyl) adenine (a plant growth 'hormone') and analogues mimic the inhibitory effect of citrate and bind to the glycopeptide as well. Replot data for citrate and N6-(Δ2-isopentyl) adenine inhibition indicate that both agents have no more than one binding constant. These results implicate calcium, glycopeptide, and energy-dependent transport of solutes in some, as yet undefinable, way.

Placental amino acid transport

1995 ◽  
Vol 268 (6) ◽  
pp. C1321-C1331 ◽  
Author(s):  
A. J. Moe
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Human Placenta ◽  
Amino Acid Transport ◽  
Single Layer ◽  
Maternal Blood ◽  
Transport Systems ◽  
Amino Acid Transporters ◽  
Acid Transport ◽  
Principal Mechanism

Normal fetal growth and development depend on a continuous supply of amino acids from the mother to the fetus. The placenta is responsible for the transfer of amino acids between the two circulations. The human placenta is hemomonochorial, meaning that the maternal and fetal circulations are separated by a single layer of polarized epithelium called the syncytiotrophoblast, which is in direct contact with maternal blood. Transport proteins located in the microvillous and basal membranes of the syncytiotrophoblast are the principal mechanism for transfer from maternal blood to fetal blood. Knowledge of the function and regulation of syncytiotrophoblast amino acid transporters is of great importance in understanding the mechanism of placental transport and potentially improving fetal and newborn outcomes. The development of methods for the isolation of microvillous and basal membrane vesicles from human placenta over the past two decades has contributed greatly to this understanding. Now a primary cultured trophoblast model is available to study amino acid transport and regulation as the cells differentiate. The types of amino acid transporters and their distribution between the syncytiotrophoblast microvillous and basal membranes are somewhat unique compared with other polarized epithelia. These differences may reflect the unusual circumstance of this epithelium that is exposed to blood on both sides. The current state of knowledge as to the types of transport systems present in syncytiotrophoblast, their regulation, and the effects of maternal consumption of drugs on transport are discussed.

scholarly journals Expression and adaptive regulation of amino acid transport system A in a placental cell line under amino acid restriction

Reproduction ◽  
2006 ◽  
Vol 131 (5) ◽  
pp. 951-960 ◽  
Author(s):  
H N Jones ◽  
C J Ashworth ◽  
K R Page ◽  
H J McArdle
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cell Line ◽  
Transport System ◽  
Amino Acid Transport ◽  
Essential Amino Acids ◽  
Acid Transport ◽  
Amino Acid Transport System ◽  
Transcellular Transport ◽  
System A

Trans-placental transport of amino acids is vital for the developing fetus. Using the BeWo cell line as a placental model, we investigated the effect of restricting amino acid availability on amino acid transport system type A. BeWo cells were cultured either in amino acid-depleted (without non-essential amino acids) or control media for 1, 3, 5 or 6 h. System A function was analysed using α(methyl-amino)isobutyric acid (MeAIB) transcellular transport studies. Transporter (sodium coupled neutral amino acid transporter (SNAT1/2)) expression was analysed at mRNA and protein level by Northern and Western blotting respectively. Localisation was carried out using immunocytochemistry. MeAIB transcellular transport was significantly (P< 0.05) increased by incubation of the cells in amino acid-depleted medium for 1 h, and longer incubation times caused further increases in the rate of transfer. However, the initial response was not accompanied by an increase in SNAT2 mRNA; this occurred only after 3 h and further increased for the rest of the 6-h incubation. Similarly, it took several hours for a significant increase in SNAT2 protein expression. In contrast, relocalisation of existing SNAT2 transporters occurred within 30 min of amino acid restriction and continued throughout the 6-h incubation. When the cells were incubated in medium with even lower amino acid levels (without non-essential plus 0.5 × essential amino acids), SNAT2 mRNA levels showed further significant (P< 0.0001) up-regulation. However, incubation of cells in depleted medium for 6 h caused a significant (P= 0.014) decrease in the expression of SNAT1 mRNA. System L type amino acid transporter 2 (LAT2) expression was not changed by amino acid restriction, indicating that the responses seen in the system A transporters were not a general cell response. These data have shown that placental cells adaptin vitroto nutritional stress and have identified the physiological, biochemical and genomic mechanisms involved.

Amino acid transport systems in intestinal brush-border membranes from lepidopteran larvae

1989 ◽  
Vol 257 (3) ◽  
pp. R494-R500 ◽  
Author(s):  
B. Giordana ◽  
V. F. Sacchi ◽  
P. Parenti ◽  
G. M. Hanozet
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Brush Border ◽  
Amino Acid Transport ◽  
Transport Systems ◽  
Acid Transport ◽  
Specific System ◽  
Neutral Amino Acids ◽  
Intestinal Brush Border ◽  
Lepidopteran Larvae

Experiments with intestinal brush-border membrane vesicles from lepidopteran larvae disclosed the occurrence of unique cotransporter proteins that use K+ as the driver cation for the transmembrane transfer of amino acids across the luminal border of midgut enterocytes. Six apical membrane amino acid transport systems have been identified. These systems are 1) a neutral amino acid transporter with a broad spectrum of interactions with most neutral amino acids, which is highly concentrative, strongly K+- and electrical potential-dependent, poorly stereospecific, and recognizes histidine, but not proline, glycine, or alpha-(methylamino)isobutyric acid (MeAIB); 2) a specific system for L-proline; 3) a specific system for glycine with a higher affinity for Na+ than for K+; 4) a specific system for L-lysine, which is dependent on membrane potential, is highly sensitive to external K+, and does not interact with L-arginine or neutral amino acids; 5) a specific K+-dependent process for glutamic acid, which does not recognize aspartic acid; and last, 6) an apparently unique K+- driven mechanism for D-alanine, which is potential-dependent and strongly stereospecific.

AMINO ACID TRANSPORT IN BRAIN CORTEX SLICES: II. COMPETITION BETWEEN AMINO ACIDS

1962 ◽  
Vol 40 (11) ◽  
pp. 1591-1602 ◽  
Author(s):  
P. N. Abadom ◽  
P. G. Scholefield
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Rat Brain ◽  
Amino Acid Transport ◽  
Brain Cortex ◽  
Transport Systems ◽  
Acid Transport ◽  
Inhibitory Effects ◽  
Brain Cortex Slices ◽  
Cortex Slices

Evidence is presented which indicates that several amino acid transport systems are present in rat brain cortex slices, each with its own specificity with regard to substrate and with regard to amino acids which produce inhibitory effects. The nature of these inhibitory effects may be either direct (competition for a limiting number of sites) or indirect (as they are when glutamate or aspartate cause a decrease in the ATP content).Comparison of the specificities of the glycine transport systems present in rat brain cortex slices and in Ehrlich ascites carcinoma cells indicates that these two systems have little in common and the relation of this finding to the structural requirements necessary for chemotherapeutic activity is discussed.

In vivo muscle amino acid transport involves two distinct processes

2004 ◽  
Vol 287 (1) ◽  
pp. E136-E141 ◽  
Author(s):  
Sharon Miller ◽  
David Chinkes ◽  
David A. MacLean ◽  
Dennis Gore ◽  
Robert R. Wolfe
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Interstitial Fluid ◽  
Muscle Blood Flow ◽  
Amino Acid Uptake ◽  
Transport Systems ◽  
Acid Uptake ◽  
Acid Transport ◽  
Rate Limiting

We have tested the hypothesis that transit through the interstitial fluid, rather than across cell membranes, is rate limiting for amino acid uptake from blood into muscle in human subjects. To quantify muscle transmembrane transport of naturally occurring amino acids, we developed a novel 4-pool model that distinguishes between the interstitial and intracellular fluid compartments. Transport kinetics of phenylalanine, leucine, lysine, and alanine were quantified using tracers labeled with stable isotopes. The results indicate that interstitial fluid is a functional compartment insofar as amino acid kinetics are concerned. In the case of leucine and alanine, transit between blood and interstitial fluid was potentially rate limiting for muscle amino acid uptake and release in the postabsorptive state. For example, in the case of leucine, the rate of transport between blood and interstitial fluid compared with the corresponding rate between interstitial fluid and muscle was 247 ± 36 vs. 610 ± 95 nmol·min−1·100 ml leg−1, respectively ( P < 0.05). Our results are consistent with the process of diffusion governing transit from blood to interstitial fluid without selectivity, and of specific amino acid transport systems with varying degrees of efficiency governing transit from interstitial fluid to muscle. These results imply that changes in factors that affect the transit of amino acids from blood through interstitial fluid, such as muscle blood flow or edema, could play a major role in controlling the rate of muscle amino acid uptake.

scholarly journals Amino Acid Transport into Cultured McCoy Cells Infected with Chlamydia trachomatis

2000 ◽  
Vol 68 (9) ◽  
pp. 5439-5442 ◽  
Author(s):  
Angela Harper ◽  
Christopher I. Pogson ◽  
John H. Pearce
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Chlamydia Trachomatis ◽  
Amino Acid Transport ◽  
Equilibrium Concentration ◽  
Transport Systems ◽  
Acid Transport ◽  
Entry Rate ◽  
Great Capacity ◽  
Cationic Amino Acids

ABSTRACT Amino acid transport into McCoy cells infected with strains representative of the two major biovars of Chlamydia trachomatis has been studied to determine if uptake is increased during infection. Preliminary work suggested that the transport systems L, A/ASC (for neutral amino acid transport), N (for transport of Asn, Gln, and His) and y+ (for cationic amino acids) were present in McCoy cells. With lymphogranuloma venereum biovar strain 434, little difference in the influx of representative amino acids Trp, His, and Lys or the analogue 2-aminoisobutyric acid (AIB) was observed during infection. With trachoma biovar strain DK20, a small increase in the initial entry rate and equilibrium concentration of each amino acid was found. McCoy cells appear to have great capacity for concentrating amino acids, which might obviate the need for transport induction by chlamydiae under conditions favoring the growth of infectious organisms.

Neutral amino acid transport systems of microvillous membrane of human placenta

1988 ◽  
Vol 254 (6) ◽  
pp. C773-C780 ◽  
Author(s):  
L. W. Johnson ◽  
C. H. Smith
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Plasma Membranes ◽  
Competitive Inhibition ◽  
Transport Systems ◽  
Acid Uptake ◽  
Acid Transport ◽  
Independent System ◽  
High Affinity

Placental transport produces concentrations of amino acids in fetal blood greater than those of maternal blood. Competitive inhibition studies of zwitterionic amino acid transport in isolated vesicles from the microvillous (maternal facing) plasma membranes of syncytiotrophoblast defined three transport systems: 1) a sodium-dependent system that supports methylaminoisobutyric acid (MeAIB) transport and has the characteristics of an A system; 2) a sodium-independent system with a high affinity for leucine and other amino acids with branched or aromatic side chains; and 3) a sodium-independent system with a preference for alanine as a substrate. The two sodium-independent systems could be further discriminated by marked specificity for trans stimulation with alanine or with leucine. System ASC, known to be present in whole placenta, and the neutral brush-border or imino systems of other polarized epithelia were apparently absent. Kinetic characteristics of the A system make it the probable primary driving force for concentrative transfer of its substrate amino acids to the fetus. Characteristics of the high-affinity leucine system demonstrated that it is saturated by normal serum leucine concentrations. Regulation of either system has the potential to alter placental amino acid uptake and transfer to the fetus.

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