The regulation of neutral amino acid transport by amino acid availability in animal cells

Shotwell, Mark A.; Oxender, Dale L.

doi:10.1016/0968-0004(83)90099-3

Cited by 31 publications

(25 citation statements)

References 26 publications

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“…Earlier studies of pancreatic amino-acid transport established no regulatory role for islet hormones [4,5,8,20] or alloxan-induced diabetes [4], albeit glucose transport was stimulated by insulin in pancreatic acini [20]. In rat hepatocytes Na+-dependent neutral amino-acid transport via the hormone-sensitive System A [14,38] is elevated by insulin, glucagon and streptozotocin-induced diabetes, and activation of transport by diabetes may occur in vivo as a result of the hyperglucagonemia associated with the disease [2].…”

Section: Introductionmentioning

confidence: 98%

Ionic dependence of amino-acid transport in the exocrine pancreatic epithelium: Calcium dependence of insulin action

Norman

Mann

1987

J. Membrain Biol.

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Rapid unidirectional transport (15 sec) of L-serine and 2-methylaminoisobutyric acid (MeAIB) was studied in the isolated perfused rat pancreas using a dual-tracer dilution technique. Time-course experiments in the presence of normal cation gradients revealed a time-dependent transstimulation of L-serine influx and transinhibition of MeAIB influx. Transport of the model nonmetabolized System A analog MeAIB was Na+ dependent and significantly inhibited during perfusion with 1 mM ouabain. Although transport of L-serine was largely Na+ independent, ouabain caused a time-dependent inhibition of transport. Influx of both amino acids appeared to be inhibited by the ionophore monensin but unaffected by a lowered extracellular potassium concentration. Removal of extracellular calcium had no effect on influx of the natural substrate L-serine, whereas stimulation of transport by exogenous insulin (100 microU/ml) was entirely dependent upon extracellular calcium and unaffected by ouabain. Paradoxically, exogenous insulin had no effect on the time-course of MeAIB influx. The characteristics of L-serine influx described in earlier studies together with our present findings suggest that insulin may modulate the activity of System asc in the exocrine pancreatic epithelium by a calcium-dependent mechanism.

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Section: Introductionmentioning

confidence: 98%

Ionic dependence of amino-acid transport in the exocrine pancreatic epithelium: Calcium dependence of insulin action

Norman

Mann

1987

J. Membrain Biol.

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“…AIB, a non-metabolizable analogue of alanine, is frequently used to investigate alanine transport mechanism in eukaryotes (Lepley & Mukkada, 1983;Shotwell & Oxender, 1983). When Giardia cells were exposed to hypo-osmotic stress in the presence of external AIB, influx was observed.…”

Section: Effect Of Na+ Ci-and Inhibitors On Alanine Effluxmentioning

confidence: 99%

“…(1993) and Nygaard et al (1994) reported that Giardia contained an antiport for alanine influx and efflux, and this antiport showed a broad specificity for other amino acids structurally similar to Lalanine. A characteristic feature of this antiport was its inability to utilize AIB, a compound that is commonly used as a non-metabolizable analogue of alanine in investigation of alanine transport in other systems (Lepley & Mukkada, 1983;Shotwell & Oxender, 1983). On this basis, AIB was chosen to investigate the membrane transporter responsible for the acute response of Giardia to hypo-osmotic stress.…”

Section: Aib Transport Under Hypotonic Conditionsmentioning

confidence: 99%

The role of alanine in the acute response of Giardia intestinalis to hypo-osmotic shock

1995

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The effect of medium hypo-osmolality on cell volume and intracellular amino acid composition was studied in the protozoan parasite Giadia intestinalis. When G. intestinalis was exposed to hypotonic medium, it initially swelled by 40% of its original volume and then decreased its volume, thus demonstrating a regulatory volume decrease process (RVD). These processes were accompanied by a rapid release of intracellular neutral amino acids, especially alanine, but not by amino acids with net charges such as glutamate and ornithine. The net alanine efflux was Na+ and CI-independent, and sensitive to medium osmolality. Alanine efflux was sigmoidal with respect to medium osmolality, with an approximately linear relationship over a range of 250 mOsm kg-l. Alanine efflux was also sensitive to temperature, and an Arrhenius plot gave a Q l o of 36 and an activation energy of 25 kcal mol-l (105 kJ mol-l), suggesting that a carrier-type transport protein, or uniport was involved in the net alanine efflux under hypotonic conditions. This volumeactivated (VA) alanine efflux was not inhibited by ionophores or chloride channel blockers. Of the potential inhibitors tested, only phydroxymercuribenzoate inhibited net alanine efflux. This thiol reagent also inhibited giardial RVD, suggesting that alanine efflux plays a significant role in this process. The VA (alanine) uniport was able to transport 2-aminoisobutyric acid (AIB), a structural analogue of alanine which is frequently used for the characterization of eukaryotic alanine transport but which is not transported by Giardia under isotonic conditions. On the basis of AIB uptake under hypotonic conditions and lack of transactivation of AIB efflux from AIB-loaded cells by external 10 mM alanine or glycine under isotonic conditions, it is evident that the VA (alanine) uniport is different from the previously reported (alanine) antiport.

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“…Recently, transport systems A, ASC, and L have been characterized in Chinese hamster ovary (CHO) cells (2,34). Studies on system L regulation has also been carried out in these cells (24,33,(35)(36)(37) by using a temperature-sensitive leucyl-tRNA synthetase mutant, the CHO tsHl line. When this mutant is incubated at marginally permissive temperatures, a significant increase in leucine transport activity occurs, indicating that the cell responds to leucine limitation resulting from the defective leucyl-tRNA synthetase.…”

mentioning

confidence: 99%

Characterization of a Chinese hamster-human hybrid cell line with increased system L amino acid transport activity.

Lobatón¹,

Moreno²,

Oxender³

1984

Mol. Cell. Biol.

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We have studied leucine transport in several Chinese hamster-human hybrid cell lines obtained by fusion of a temperature-sensitive line of Chinese hamster ovary cells, tsO25C1, and normal human leukocytes. A hybrid cell line exhibiting a twofold increase in L-leucine uptake over that in the parental cell line was found. This hybrid cell line, 158CnpT-1, was temperature resistant, whereas the parental Chinese hamster ovary mutant, tsO25C1, contained a temperature-sensitive leucyl-tRNA synthetase mutation. An examination of the different amino acid transport systems in this hybrid cell line revealed a specific increase of system L activity with no significant changes in systems A and ASC. The Vmax for L-leucine uptake exhibited by the hybrid 158CnpT-1 was twice that in the CHO parental mutant, ts025C1. Cytogenetic analysis showed that the hybrid 158CnpT-1 contains four complete human chromosomes (numbers 4, 5, 10, and 21) and three interspecific chromosomal translocations in a total complement of 34 chromosomes. Biochemical and cytogenetic analysis of segregant clones obtained from hybrid 158CnpT-1 showed that the primary temperature resistance and high system L transport phenotypes can be segregated from this hybrid independently. The loss of the primary temperature resistance was associated with the loss of the human chromosome 5, as previously reported by other laboratories, whereas the loss of the high leucine transport phenotype, which is associated with a lesser degree of temperature resistance, was correlated with the loss of human chromosome 20. Amino acid accumulation in mammalian cells is carried out by several distinct transport systems. The major components for neutral amino acid uptake in mammalian cells are systems A, ASC, and L, which were first identified in Ehrlich ascites tumor cells (5, 26). System A is Na+ dependent and serves mainly for the uptake of amino acids with short, polar, or linear side chains. System L is Na+ independent, shows reactivity toward branched-chain and aromatic amino acids, and exhibits rapid exchange between intracellular and extracellular substrates. System ASC is Na+ dependent and shows a strong preference for alanine, serine, and cysteine. Similar systems have been characterized in a number of different cell lines (1,4,9,13,16,27). Recently, transport systems A, ASC, and L have been characterized in Chinese hamster ovary (CHO) cells (2,34). Studies on system L regulation has also been carried out in these cells (24,33,(35)(36)(37) by using a temperature-sensitive leucyl-tRNA synthetase mutant, the CHO tsHl line. When this mutant is incubated at marginally permissive temperatures, a significant increase in leucine transport activity occurs, indicating that the cell responds to leucine limitation resulting from the defective leucyl-tRNA synthetase. Elevated leucine levels in the growth medium, however, allow CHO tsHl cells to grow at nonpermissive temperatures, indicating that increased uptake of leucine is associated with temperature resistance in this mutant. In ad...

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The regulation of neutral amino acid transport by amino acid availability in animal cells

Cited by 31 publications

References 26 publications

Ionic dependence of amino-acid transport in the exocrine pancreatic epithelium: Calcium dependence of insulin action

Ionic dependence of amino-acid transport in the exocrine pancreatic epithelium: Calcium dependence of insulin action

The role of alanine in the acute response of Giardia intestinalis to hypo-osmotic shock

Characterization of a Chinese hamster-human hybrid cell line with increased system L amino acid transport activity.

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