Article

Expression of glutamate carboxypeptidase II in human brain.

Department of Biochemistry, Institute of Organic Chemistry and Biochemistry, Academy of Science of the Czech Republic, Flemingovo n.2, Prague 6, 16610 Czech Republic.
Neuroscience (impact factor: 3.38). 03/2007; 144(4):1361-72. DOI:10.1016/j.neuroscience.2006.10.022 pp.1361-72
Source: PubMed

ABSTRACT Glutamate carboxypeptidase II (GCPII) is a transmembrane glycoprotein expressed in various tissues. When expressed in the brain it cleaves the neurotransmitter N-acetylaspartylglutamate (NAAG), yielding free glutamate. In jejunum it hydrolyzes folylpoly-gamma-glutamate, thus facilitating folate absorption. The prostate form of GCPII, known as prostate specific membrane antigen (PSMA), is an established cancer marker. The NAAG-hydrolyzing activity of GCPII has been implicated in a number of pathological conditions in which glutamate is neurotoxic (e.g. amyotrophic lateral sclerosis, Huntington's disease, Alzheimer's disease, epilepsy, schizophrenia, and stroke). Inhibition of GCPII was shown to be neuroprotective in tissue culture and in animal models. GCPII is therefore an interesting putative therapeutic target. However, only very limited and controversial data on the expression and localization of GCPII in human brain are available. Therefore, we set out to analyze the activity and expression of GCPII in various compartments of the human brain using a radiolabeled substrate of the enzyme and the novel monoclonal antibody GCP-04, which recognizes an epitope on the extracellular portion of the enzyme and is more sensitive to GCPII than to the homologous GCPIII. We show that this antibody is more sensitive in immunoblots than the widely used antibody 7E11. By Western blot, we show that there are approximately 50-300 ng of GCPII/mg of total protein in human brain, depending on the specific area. Immunohistochemical analysis revealed that astrocytes specifically express GCPII in all parts of the brain. GCPII is enzymatically active and the level of activity follows the expression pattern. Using pure recombinant GCPII and homologous GCPIII, we conclude that GCPII is responsible for the majority of overall NAAG-hydrolyzing activity in the human brain.

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    American Journal of Clinical Nutrition 08/2007; 86(2):514-21. · 6.67 Impact Factor
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Keywords

Alzheimer's disease
 
amyotrophic lateral sclerosis
 
extracellular portion
 
facilitating folate absorption
 
free glutamate
 
GCPII
 
GCPII/mg
 
Glutamate carboxypeptidase II
 
homologous GCPIII
 
Huntington's disease
 
Immunohistochemical analysis
 
interesting putative therapeutic target
 
NAAG-hydrolyzing activity
 
neurotransmitter N-acetylaspartylglutamate
 
novel monoclonal antibody GCP-04
 
prostate specific membrane antigen
 
pure recombinant GCPII
 
specific area
 
various compartments
 
various tissues