Regulation of system L amino acid transport byTetrahymena thermophilia

A rapid method for the functional reconstruction of amino acid transport from liver plasma-membrane vesicles using the neutral detergent decanoyl-N-glucamide (‘MEGA-10’) is described. The method is a modification of that previously employed in this laboratory for reconstitution of amino acid transport systems from kidney brush-border membranes [Lynch & McGivan (1987) Biochem. J. 244, 503-508]. The transport activities termed ‘System A’, ‘System N’, and ‘System L’ are all reconstituted. The reconstitution procedure is rapid and efficient and is suitable as an assay for transport activity in studies involving membrane fractionation. By using this reconstitution procedure, System A transport activity was partially purified by lectin-affinity chromatography.

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Expression and regulation of 4F2hc and hLAT1 in human trophoblasts

AJP Cell Physiology ◽

10.1152/ajpcell.2002.282.1.c196 ◽

2002 ◽

Vol 282 (1) ◽

pp. C196-C204 ◽

Cited By ~ 46

Author(s):

Yoko Okamoto ◽

Masahiro Sakata ◽

Kazuhiro Ogura ◽

Toshiya Yamamoto ◽

Masaaki Yamaguchi ◽

...

Keyword(s):

Amino Acid ◽

Cell Line ◽

Transport System ◽

Human Placenta ◽

Amino Acid Transport ◽

Calcium Ionophore ◽

Acid Transport ◽

Amino Acid Transport System ◽

System L ◽

Choriocarcinoma Cell Line

The neutral amino acid transport system L is a sodium-independent transport system in human placenta and choriocarcinoma cells. Recently, it was found that the heterodimer composed of hLAT1 (a light-chain protein) and 4F2 heavy chain (4F2hc), a type II transmembrane glycoprotein, is responsible for system L amino acid transport. We found that the mRNAs of 4F2hc and hLAT1 were expressed in the human placenta and a human choriocarcinoma cell line. The levels of the 4F2hc and hLAT1 proteins in the human placenta increased at full term compared with those at midtrimester. Immunohistochemical data showed that these proteins were localized mainly in the placental apical membrane. Data from leucine uptake experiments, Northern blot analysis, and immunoblot analysis showed that this transport system was partially regulated by protein kinase C and calcium ionophore in the human choriocarcinoma cell line. Our results suggest that the heterodimer of 4F2hc and hLAT1 may play an important role in placental amino acid transport system L.

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Expression of the surface antigen 4F2hc affects system-L-like neutral-amino-acid-transport activity in mammalian cells

Biochemical Journal ◽

10.1042/bj3240535 ◽

1997 ◽

Vol 324 (2) ◽

pp. 535-541 ◽

Cited By ~ 32

Author(s):

Stefan BRÖER ◽

Angelika BRÖER ◽

Bernd HAMPRECHT

Keyword(s):

Amino Acid ◽

Surface Antigen ◽

Amino Acid Transport ◽

Cho Cells ◽

Mammalian Cells ◽

Primary Cultures ◽

Transport Systems ◽

Acid Transport ◽

Transport Activity ◽

System L

Mammalian cells possess a variety of amino acid-transport systems with overlapping substrate specificity. System L is one of the major amino acid-transport systems of non-epithelial cells. By expression cloning we have recently demonstrated that the surface antigen 4F2hc (CD98) is a necessary component for expression of system-L-like amino acid-transport activity in C6-BU-1 rat glioma cells [Bröer, Bröer and Hamprecht (1995) Biochem. J. 312, 863–870]. 4F2hc mRNA was detected in CHO cells, COS cells, activated lymphocytes isolated from mouse spleen and primary cultures of astrocytes. In all these cell types, Na+-independent isoleucine transport was mediated by system L. No contribution of system y+L to isoleucine or arginine transport was detected in C6-BU-1 cells. In lymphocytes, both system-L-like amino acid-transport activity and 4F2hc mRNA levels increased after treatment with phorbol ester plus ionomycin. Antisense oligonucleotides caused modest inhibition of Na+-independent isoleucine transport in C6-BU-1 cells and primary cultures of astroglial cells, whereas arginine transport was unaffected. Overexpression of 4F2hc cDNA in CHO cells resulted in an increase in Na+-independent isoleucine transport.

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Reduction of In Vivo Placental Amino Acid Transport Precedes the Development of Intrauterine Growth Restriction in the Non-Human Primate

Nutrients ◽

10.3390/nu13082892 ◽

2021 ◽

Vol 13 (8) ◽

pp. 2892

Author(s):

Fredrick J. Rosario ◽

Anita Kramer ◽

Cun Li ◽

Henry L. Galan ◽

Theresa L. Powell ◽

...

Keyword(s):

Amino Acid ◽

Amino Acid Transport ◽

Intrauterine Growth Restriction ◽

Growth Restriction ◽

Acid Transport ◽

Mole Percent ◽

System A ◽

System L ◽

Human Primate

Intrauterine growth restriction (IUGR) is associated with reduced placental amino acid transport (AAT). However, it remains to be established if changes in AAT contribute to restricted fetal growth. We hypothesized that reduced in vivo placental AAT precedes the development of IUGR in baboons with maternal nutrient restriction (MNR). Baboons were fed either a control (ad libitum) or MNR diet (70% of control diet) from gestational day (GD) 30. At GD 140, in vivo transplacental AA transport was measured by infusing nine (13)C- or (2)H-labeled essential amino acids (EAAs) as a bolus into the maternal circulation at cesarean section. A fetal vein-to-maternal artery mole percent excess ratio for each EAA was measured. Microvillous plasma membrane (MVM) system A and system L transport activity were determined. Fetal and placental weights were not significantly different between MNR and control. In vivo, the fetal vein-to-maternal artery mole percent excess ratio was significantly decreased for tryptophan in MNR. MVM system A and system L activity was markedly reduced in MNR. Reduction of in vivo placental amino acid transport precedes fetal growth restriction in the non-human primate, suggesting that reduced placental amino acid transfer may contribute to IUGR.

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