The role of protein kinase C (PKC) in N-methyl-d-aspartate (NMDA) receptor-mediated biochemical differentiation and c-fos protein expression was investigated in cultured cerebellar granule neurons. The biochemical differentiation of glutamatergic granule cells was studied in terms of the specific activity of phosphate-activated glutaminase, an enzyme important in the synthesis of the putative neurotransmitter pool of glutamate. When the partially depolarized cells were treated with NMDA for the last 1 to 3 days (between 2 and 5 days in vitro), it elevated the specific activity of glutaminase. In contrast, NMDA had little effect on the activity of aspartate aminotransferase or of lactate dehydrogenase. Treatment of 10-day old granule neurons with NMDA also resulted in a marked increase in the immunocytochemically measured expression of c-fos protein. The increases in both the activity of glutaminase and the steady state level of c-fos protein were specific to the activation of NMDA receptors, as they were completely blocked by d,l-2-amino-5-phosphonovaleric acid. The specific stimulation of NMDA receptors in PKC-depleted granule neurons or in the presence of reasonably specific PKC inhibitors also produced significant elevation in the activity of glutaminase and the expression of c-fos protein. These increases were similar in magnitude to those observed in the granule neurons of the respective control groups. Our findings demonstrate that PKC is not directly involved in the NMDA receptor-mediated signal transduction processes associated with biochemical differentiation and c-fos induction in cerebellar granule neurons. © 1995 Plenum Publishing Corporation.
|Publication status||Published - 1 May 1995|
- c-fos protein expression
- cerebellar granule neuron
- protein kinase C
- regulation of glutaminase