Document Detail


Posttranslational alanine trans-stimulation of zwitterionic amino acid transport systems in human intestinal Caco-2 cells.
MedLine Citation:
PMID:  11971679     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
BACKGROUND: Neutral dietary amino acids, such as alanine, are transported across the gut lumen by both Na(+)-dependent (System B) and Na(+)-independent (System L) carriers, but the nature of the acute phase of substrate-induced uptake is unknown. This study examined the effects of acute amino acid substrate exposure on the rapid modulation of apical membrane alanine transport in cultured human intestinal cells. METHODS: System B and System L transport activity kinetics, as well as ATB(0) mRNA levels, were measured in confluent Caco-2 monolayers treated with various metabolic agents during short-term and extended time periods. RESULTS: Depleting the incubation medium of alanine attenuated both System B and System L uptake activities within 30 mins, with a complete return to baseline values within 3 h. Extracellular alanine added to depleted Caco-2 cells rapidly (within 5 min) increased alanine transport activities. Kinetic analysis showed that acute alanine exposure increased both K(m) and V(max) of each transport system, indicative of a trans-stimulation effect. Augmenting intracellular alanine levels using the cytosolic alanine aminotransferase inhibitor, aminooxyacetic acid, increased alanine uptake activity. Acute exposure to other substrates of Systems B and L also increased the uptake of alanine, while nonsubstrates did not affect alanine uptake. Cycloheximide or actinomycin did not affect substrate acute activation of System B, and the steady-state level of ATB(0) mRNA was not altered by amino acid exposure. CONCLUSION: Increasing alanine availability to intestinal cells, by either exogenous substrate exposure or inhibition of intracellular catabolism, acutely and reversibly increases apical membrane alanine transport activity via a posttranslation trans-stimulation mechanism.
Authors:
Ming Pan; Wiley W Souba; Christopher L Wolfgang; Anne M Karinch; Bruce R Stevens
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Journal of surgical research     Volume:  104     ISSN:  0022-4804     ISO Abbreviation:  J. Surg. Res.     Publication Date:  2002 May 
Date Detail:
Created Date:  2002-04-24     Completed Date:  2002-06-11     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0376340     Medline TA:  J Surg Res     Country:  United States    
Other Details:
Languages:  eng     Pagination:  63-9     Citation Subset:  IM    
Affiliation:
Department of Surgery, Pennsylvania State University, Hershey, Pennsylvania 17033, USA.
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MeSH Terms
Descriptor/Qualifier:
Alanine / pharmacokinetics,  pharmacology*
Amino Acid Transport Systems, Neutral / metabolism*
Amino Acids / deficiency
Biological Transport
Caco-2 Cells
Dose-Response Relationship, Drug
Humans
Intestines / metabolism*,  pathology
Kinetics
Protein Processing, Post-Translational*
Time Factors
Chemical
Reg. No./Substance:
0/Amino Acid Transport Systems, Neutral; 0/Amino Acids; 56-41-7/Alanine

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


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