title: Developmental increase in ecto-5'-nucleotidase activity overlaps with appearance of two immunologically distinct enzyme isoforms in rat hippocampal synaptic plasma membranes.
abstract: Ecto-5'-nucleotidase (e-5NT), a glycosylphosphatidylinositol-linked membrane protein, catalyzes a conversion of AMP to adenosine, which influences nearly every aspect of brain physiology, including embryonic and postnatal brain development. The present study aimed to investigate a pattern of expression, activity and kinetic properties of e-5NT in the hippocampal formation and synaptic plasma membrane (SPM) preparations in rats at postnatal days (PDs) 7, 15, 20, 30 and 90. By combining gene expression analysis and enzyme histochemistry, we observed that e-5NT mRNA reached the adult level at PD20, while the enzyme activity continued to increase beyond this age. Further analysis revealed that hippocampal layers rich in synapses expressed the highest levels of e-5NT activity, while in layers populated with neuronal cell bodies, the enzyme activity was weak or absent. Therefore, activity and expression of e-5NT were analyzed in SPM preparations isolated from rats at different ages. The presence of two protein bands of about 65 and 68 kDa was determined by immunoblot analysis. The 65-kDa band was present at all ages, and its abundance increased from PD7 to PD20. The 68-kDa band appeared at PD15 and increased until PD30, coinciding with the increase of e-5NT activity, substrate affinity and enzymatic efficiency. Since distinct e-5NT isoforms may derive from different patterns of the enzyme protein N-glycosylation, we speculate that long-term regulation of e-5NT activity in adulthood may be effectuated at posttranslational level and without overall change in the gene and protein expression.
authors.affiliation: Laboratory of Molecular Biology and Endocrinology, VINCA Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001, Belgrade, Serbia, istanojevic@vinca.rs.
authors.forename: Ivana
authors.initials: I
authors.lastname: Grkovic
authors.forename: Ivana
authors.initials: I
authors.lastname: Bjelobaba
authors.forename: Nadezda
authors.initials: N
authors.lastname: Nedeljkovic
authors.forename: Natasa
authors.initials: N
authors.lastname: Mitrovic
authors.forename: Dunja
authors.initials: D
authors.lastname: Drakulic
authors.forename: Milos
authors.initials: M
authors.lastname: Stanojlovic
authors.forename: Anica
authors.initials: A
authors.lastname: Horvat
mesh_terms: D015720:5'-Nucleotidase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D018507:Gene Expression Regulation, Developmental; D006624:Hippocampus / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013570:Synaptic Membranes / Q000201:enzymology / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D012333:RNA, Messenger; D015720:5'-Nucleotidase