scholarly journals The SNAT4 isoform of the system A amino acid transporter is functional in human placental microvillous plasma membrane

2009 ◽  
Vol 587 (1) ◽  
pp. 61-72 ◽  
Author(s):  
M. Desforges ◽  
K. J. Mynett ◽  
R. L. Jones ◽  
S. L. Greenwood ◽  
M. Westwood ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Amino Acid ◽  
Amino Acid Transporter ◽  
System A ◽  
Acid Transporter

scholarly journals Characterization of the amino acid response element within the human sodium-coupled neutral amino acid transporter 2 (SNAT2) System A transporter gene

2006 ◽  
Vol 395 (3) ◽  
pp. 517-527 ◽  
Author(s):  
Stela S. Palii ◽  
Michelle M. Thiaville ◽  
Yuan-Xiang Pan ◽  
Can Zhong ◽  
Michael S. Kilberg
Keyword(s):  
Amino Acid ◽  
Rna Polymerase Ii ◽  
Mammalian Cells ◽  
Amino Acid Transporter ◽  
Neutral Amino Acid ◽  
System A ◽  
Neutral Amino Acid Transporter ◽  
Acid Transporter ◽  
Amino Acid Response

The neutral amino acid transport activity, System A, is enhanced by amino acid limitation of mammalian cells. Of the three gene products that encode System A activity, the one that exhibits this regulation is SNAT2 (sodium-coupled neutral amino acid transporter 2). Fibroblasts that are deficient in the amino acid response pathway exhibited little or no induction of SNAT2 mRNA. Synthesis of SNAT2 mRNA increased within 1–2 h after amino acid removal from HepG2 human hepatoma cells. The amino acid responsive SNAT2 genomic element that mediates the regulation has been localized to the first intron. Increased binding of selected members of the ATF (activating transcription factor) and C/EBP (CCAAT/enhancer-binding protein) families to the intronic enhancer was established both in vitro and in vivo. In contrast, there was no significant association of these factors with the SNAT2 promoter. Expression of exogenous individual ATF and C/EBP proteins documented that specific family members are associated with either activation or repression of SNAT2 transcription. Chromatin immunoprecipitation analysis established in vivo that amino acid deprivation led to increased RNA polymerase II recruitment to the SNAT2 promoter.

scholarly journals SNAT4 isoform of system A amino acid transporter is expressed in human placenta

2006 ◽  
Vol 290 (1) ◽  
pp. C305-C312 ◽  
Author(s):  
M. Desforges ◽  
H. A. Lacey ◽  
J. D. Glazier ◽  
S. L. Greenwood ◽  
K. J. Mynett ◽  
...  
Keyword(s):  
Amino Acid ◽  
Protein Expression ◽  
Western Blot ◽  
Human Placenta ◽  
Blot Analysis ◽  
First Trimester ◽  
Amino Acid Transporter ◽  
Full Term ◽  
System A ◽  
Acid Transporter

The system A amino acid transporter is encoded by three members of the Slc38 gene family, giving rise to three subtypes: Na+-coupled neutral amino acid transporter (SNAT)1, SNAT2, and SNAT4. SNAT2 is expressed ubiquitously in mammalian tissues; SNAT1 is predominantly expressed in heart, brain, and placenta; and SNAT4 is reported to be expressed solely by the liver. In the placenta, system A has an essential role in the supply of neutral amino acids needed for fetal growth. In the present study, we examined expression and localization of SNAT1, SNAT2, and SNAT4 in human placenta during gestation. Real-time quantitative PCR was used to examine steady-state levels of system A subtype mRNA in early (6–10 wk) and late (10–13 wk) first-trimester and full-term (38–40 wk) placentas. We detected mRNA for all three isoforms from early gestation onward. There were no differences in SNAT1 and SNAT2 mRNA expression with gestation. However, SNAT4 mRNA expression was significantly higher early in the first trimester compared with the full-term placenta ( P < 0.01). We next investigated SNAT4 protein expression in human placenta. In contrast to the observation for gene expression, Western blot analysis revealed that SNAT4 protein expression was significantly higher at term compared with the first trimester ( P < 0.05). Immunohistochemistry and Western blot analysis showed that SNAT4 is localized to the microvillous and basal plasma membranes of the syncytiotrophoblast, suggesting a role for this isoform of system A in amino acid transport across the placenta. This study therefore provides the first evidence of SNAT4 mRNA and protein expression in the human placenta, both at the first trimester and at full term.

scholarly journals The H+-Coupled Electrogenic Lysosomal Amino Acid Transporter LYAAT1 Localizes to the Axon and Plasma Membrane of Hippocampal Neurons

2003 ◽  
Vol 23 (4) ◽  
pp. 1265-1275 ◽  
Author(s):  
Christopher C. Wreden ◽  
Juliette Johnson ◽  
Cindy Tran ◽  
Rebecca P. Seal ◽  
David R. Copenhagen ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Amino Acid ◽  
Hippocampal Neurons ◽  
Amino Acid Transporter ◽  
Acid Transporter
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