Characterization of the activation of glutaminase induced by N-methyl-D-aspartate and potassium in cerebellar granule cells

✍ Scribed by S. Alavez; L. Gutiérrez-Kobeh; J. Morán

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 884 KB
• Volume: 45
• Category: Article
• ISSN: 0360-4012
• DOI: 10.1002/(sici)1097-4547(19960901)45:5<637::aid-jnr13>3.0.co;2-w

✦ Synopsis

Chronic stimulation of cerebellar granule cells with N-methyl-D-aspartate (NMDA) or KCI induces a specific activation of the enzymes directly involved in glutamate neurotransmitter synthesis. Phosphate-activated glutaminase (PAG) activity is enhanced in cultured granule neurons incubated with 150 pM NMDA or 25 mM KCl. Other enzymes are not affected by this treatment like lactate dehydrogenase (LDH) and glutamate dehydrogenase (GLDH), which is also a mitochondria1 enzyme but not directly involved in neurotransmitter synthesis. This effect is dependent on protein synthesis and is induced after 12 h r of NMDA or KCl stimulation. Kinetics of PAG activity showed that K, values were unaffected, in contrast to V,,, values that were increased approximately 70% and 215% over control by NMDA and KCI treatment, respectively. For GLDH, we found two isoforms that were affected differentially by the experimental conditions. Western blot analysis clearly evidenced an increase of approximately 120-180% in the amount of PAG in NMDAand KCI-treated cells, whereas GLDH was not significantly modified. These results demonstrate that the NMDA-and KCIinduced activation of PAG are not due to the modification of the preexisting enzyme, but to an increase in the synthesis of this enzyme. This suggests that NMDA receptor stimulation during critical periods of the cerebellar granule cell development leads to the activation of gene expression involved in the process of cell differentiation.