The transport of glutamine into mammalian cells.

Glutamine has many important functions in mammalian cells, and glutamine transport across cell membranes has accordingly been extensively studied. In the past few years a number of important glutamine transport proteins have been sequenced and their molecular properties have been characterised. In general, four major transporters are important physiologically.

Expression and activity of the glutamate transporter EAAT2 in cardiac hypertrophy: implications for ischaemia reperfusion injury.

The expression and activity of the glutamate transporter, excitatory amino acid transporter 2 (EAAT2), in cardiac hypertrophy were investigated with respect to glutamate's potential as a cardioprotective agent. Sarcolemmal vesicles (SV) isolated from hypertrophic hearts of male spontaneously hypertensive rats (SHR) or normotrophic hearts from age-matched male Wistar Kyoto rats (WKY) were used to measure the relative level of EAAT2 expression by Western blotting and the initial rate of 0-0.3 mM L-[(14)C]glutamate uptake.

Identification of the promoter elements involved in the stimulation of ASCT2 expression by glutamine availability in HepG2 cells and the probable involvement of FXR/RXR dimers.

Expression of the glutamine transport protein ASCT2 in the human hepatoma cell line HepG2 is increased when cells are cultured in the presence of glutamine and this has been shown to be due to stimulation of the ASCT2 promoter. Analysis of a number of promoter constructs localised the activation site to be between bases -653 and -543. Gel shift assays identified an IR-1 repeat within a 24bp region of this sequence which bound at least two nuclear proteins.

The pig CYP2E1 promoter is activated by COUP-TF1 and HNF-1 and is inhibited by androstenone.

Functional analysis of the pig cytochrome P4502E1 (CYP2E1) promoter identified two major activating elements. One corresponded to the hepatic nuclear factor 1 (HNF-1) consensus binding sequence at nucleotides -128/-98 and the other was located in the region -292/-266. The binding of proteins in pig liver nuclear extracts to a synthetic double-stranded oligonucleotide corresponding to this more distal activating sequence was studied by electrophoretic mobility shift assay.

Glutamine availability up-regulates expression of the amino acid transporter protein ASCT2 in HepG2 cells and stimulates the ASCT2 promoter.

Glutamine transport into the human hepatoma cell line HepG2 is catalysed primarily by an ASCT2-type transporter identical in sequence with that cloned previously from JAR cells. An antibody raised against the C-terminus of the ASCT2 protein was shown to recognize ASCT2 on Western blots. Using this antibody, it was found that variation in cell growth rate did not affect ASCT2 expression, but both growth rate and ASCT2 expression were significantly reduced by glutamine deprivation.

Characterisation of androstenone metabolism in pig liver microsomes.

Androstenone (5 alpha-androst-16-en-3-one) is a steroid pheromone produced in the testis. Excessive accumulation of androstenone together with skatole (3-methyl-indole) in the adipose tissue of some male pigs leads to "boar taint". In isolated pig hepatocytes androstenone represses the expression of cytochrome P450IIE1 (CYP2E1), the enzyme principally responsible for skatole metabolism.

Aspartate transporter expression and activity in hypertrophic rat heart and ischaemia-reperfusion injury.

This study's rationale was that the expression and activity of aspartate transporters in hypertrophied hearts might be different from normal hearts, which could affect the use of aspartate in myocardial protection of hypertrophied hearts. mRNA expression of system X(ag)(-) transporters in hearts from normal (Wistar Kyoto) and hypertrophied (spontaneously hypertensive rat) rats was investigated by RT-PCR. EAAT3 protein expression in isolated cells and vesicles from normal and hypertrophied hearts was investigated by Western blotting.

Glutamate loading protects freshly isolated and perfused adult cardiomyocytes against intracellular ROS generation.

Glutamate loading has been shown to protect single isolated perfused cardiomyocytes against metabolic inhibition and wash-off. The mechanism underpinning this protection is unknown. This study aimed to investigate whether reactive oxygen species (ROS) are generated by single isolated perfused cardiomyocytes and whether the protective effect of glutamate loading on cell metabolism is linked to ROS.

Glutaminase isoform expression in cell lines derived from human colorectal adenomas and carcinomas.

This paper describes some properties of glutamine oxidation and glutaminase isoform expression in cell lines derived from human colorectal adenomas and carcinomas. The slow-growing adenoma-derived cell line AA/C1, and the rapidly proliferating carcinoma cell line HT29, both required glutamine for growth. The rate of (14)CO(2) production from [U-(14)C]glutamine was faster in AA/C1 cells than in HT29 cells.

Identification of a plasma membrane glutamine transporter from the rat hepatoma cell line H4-IIE-C3.

Glutamine is taken up into the rat hepatoma cell line H4-IIE-C3 by a Na+-dependent transport system which is specific for glutamine, alanine, serine, cysteine and asparagine and does not tolerate substitution of Na+ by Li+. Glutamine transport was relatively weakly inhibited by a 50-fold excess of leucine and was not inhibited by phenylalanine or N -methyl aminoisobutyrate. These general properties are characteristic of the recently identified ASCT/B0 family of transporters.

Cytochrome P450IIE1 (CYP2E1) is induced by skatole and this induction is blocked by androstenone in isolated pig hepatocytes.

Skatole, a derivative of tryptophan, is produced in the hind-gut of pigs and is metabolised via hepatic cytochrome P4502E1 (CYP2E1). Excessive accumulation of skatole together with androstenone, a metabolite of testosterone, in adipose tissue in some pigs is a major cause of 'boar taint' and is associated with defective expression of CYP2E1. This phenomenon is not understood because factors regulating CYP2E1 expression in pig liver have not yet been characterised.

Characterisation and cloning of a Na(+)-dependent broad-specificity neutral amino acid transporter from NBL-1 cells: a novel member of the ASC/B(0) transporter family.

Na(+)-dependent neutral amino acid transport into the bovine renal epithelial cell line NBL-1 is catalysed by a broad-specificity transporter originally termed System B(0). This transporter is shown to differ in specificity from the B(0) transporter cloned from JAR cells [J. Biol.