Document Detail


Involvement of sialic acid in the regulation of {gamma}-aminobutyric acid uptake activity of {gamma}-aminobutyric acid transporter 1.
MedLine Citation:
PMID:  21045010     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
The γ-aminobutyric acid (GABA) transporters (GATs) have long been recognized for their key role in the uptake of neurotransmitters. The GAT1 belongs to the family of Na(+)- and Cl(-)-coupled transport proteins, which possess 12 putative transmembrane (TM) domains and three N-glycosylation sites on the extracellular loop between TM domains 3 and 4. Previously, we demonstrated that terminal trimming of N-glycans is important for the GABA uptake activity of GAT1. In this work, we examined the effect of deficiency, removal or oxidation of surface sialic acid residues on GABA uptake activity to investigate their role in the GABA uptake of GAT1. We found that the reduced concentration of sialic acid on N-glycans was paralleled by a decreased GABA uptake activity of GAT1 in Chinese hamster ovary (CHO) Lec3 cells (mutant defective in sialic acid biosynthesis) in comparison to CHO cells. Likewise, either enzymatic removal or chemical oxidation of terminal sialic acids using sialidase or sodium periodate, respectively, resulted in a strong reduction in GAT1 activity. Kinetic analysis revealed that deficiency, removal or oxidation of terminal sialic acids did not affect the K(m) GABA values. However, deficiency and removal of terminal sialic acids of GAT1 reduced the V(max) GABA values with a reduced apparent affinity for extracellular Na(+). Oxidation of cell surface sialic acids also strongly reduced V(max) without affecting both affinities of GAT1 for GABA and Na(+), respectively. These results demonstrated for the first time that the terminal sialic acid of N-linked oligosaccharides of GAT1 plays a crucial role in the GABA transport process.
Authors:
Jing Hu; Jian Fei; Werner Reutter; Hua Fan
Publication Detail:
Type:  Journal Article     Date:  2010-11-02
Journal Detail:
Title:  Glycobiology     Volume:  21     ISSN:  1460-2423     ISO Abbreviation:  Glycobiology     Publication Date:  2011 Mar 
Date Detail:
Created Date:  2011-02-07     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9104124     Medline TA:  Glycobiology     Country:  England    
Other Details:
Languages:  eng     Pagination:  329-39     Citation Subset:  IM    
Affiliation:
Institut für Biochemie und Molekularbiologie, Campus Benjamin Franklin, Charité-Universitätsmedizin Berlin, Arnimallee 22, 14195 Berlin-Dahlem, Germany;
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