Document Detail


Amino acid starvation induces the SNAT2 neutral amino acid transporter by a mechanism that involves eukaryotic initiation factor 2alpha phosphorylation and cap-independent translation.
MedLine Citation:
PMID:  16621798     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Nutritional stress caused by amino acid starvation involves a coordinated cellular response that includes the global decrease of protein synthesis and the increased production of cell defense proteins. Part of this response is the induction of transport system A for neutral amino acids that leads to the recovery of cell volume and amino acid levels once extracellular amino acid availability is restored. Hypertonic stress also increases system A activity as a mechanism to promote a rapid recovery of cell volume. Both a starvation-dependent and a hypertonic increase of system A transport activity are due to the induction of SNAT2, the ubiquitous member of SLC38 family. The molecular mechanisms underlying SNAT2 induction were investigated in tissue culture cells. We show that the increase in system A transport activity and SNAT2 mRNA levels upon amino acid starvation were blunted in cells with a mutant eIF2alpha that cannot be phosphorylated. In contrast, the induction of system A activity and SNAT2 mRNA levels by hypertonic stress were independent of eIF2alpha phosphorylation. The translational control of the SNAT2 mRNA during amino acid starvation was also investigated. It is shown that the 5'-untranslated region contains an internal ribosome entry site that is constitutively active in amino acid-fed and -deficient cells and in a cell-free system. We also show that amino acid starvation caused a 2.5-fold increase in mRNA and protein expression from a reporter construct containing both the SNAT2 intronic amino acid response element and the SNAT2-untranslated region. We conclude that the adaptive response of system A activity to amino acid starvation requires eukaryotic initiation factor 2alpha phosphorylation, increased gene transcription, and internal ribosome entry site-mediated translation. In contrast, the response to hypertonic stress does not involve eukaryotic initiation factor 2alpha phosphorylation, suggesting that SNAT2 expression can be modulated by specific signaling pathways in response to different stresses.
Authors:
Francesca Gaccioli; Charlie C Huang; Chuanping Wang; Elena Bevilacqua; Renata Franchi-Gazzola; Gian Carlo Gazzola; Ovidio Bussolati; Martin D Snider; Maria Hatzoglou
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2006-04-18
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  281     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2006 Jun 
Date Detail:
Created Date:  2006-06-26     Completed Date:  2006-08-18     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  17929-40     Citation Subset:  IM    
Affiliation:
Departments of Nutrition and Biochemistry, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
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MeSH Terms
Descriptor/Qualifier:
5' Untranslated Regions
Amino Acid Transport System A / genetics*,  metabolism*
Amino Acids / metabolism*
Animals
Cell-Free System
Eukaryotic Initiation Factor-2 / metabolism*
Gene Expression Regulation / physiology
Genes, Reporter
Glioma
Hela Cells
Humans
Hypertonic Solutions
Osmotic Pressure
Phosphorylation
Protein Biosynthesis / physiology*
RNA, Messenger / metabolism
Ribosomes / physiology
Signal Transduction / physiology
Transcriptional Activation / physiology
Grant Support
ID/Acronym/Agency:
R01 DK 53307/DK/NIDDK NIH HHS; R01 DK 60596/DK/NIDDK NIH HHS
Chemical
Reg. No./Substance:
0/5' Untranslated Regions; 0/Amino Acid Transport System A; 0/Amino Acids; 0/Eukaryotic Initiation Factor-2; 0/Hypertonic Solutions; 0/RNA, Messenger; 0/SLC38A2 protein, human

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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