Post-translational modification of spectrin induced by excitatory amino acids in cultured cerebellar granule cells

We have utilized primary cultures from rat cerebellum, 95% enriched in granule cells, to investigate the expression of proteins of the cortical cytoskeleton and of the synaptic vesicles and the relationship between excitatory amino acid receptors activation and calcium dependent proteolysis of fodrin. Exposure of neuronal cell cultures to N-methyl-D-aspartate (NMDA) in the absence of Mg(2+) and in the presence of glycine causes the appearance of 150 kDa proteolytic fragment (s) of-fodrin as detected by immunoblots. The effect of NMDA on fodrin proteolysis is inhibited by the NMDA antagonist 2-amino-5-phosphonovalerate (APV), by 3 mM Mg(2+), by calpain I inhibitor and by the omission of extracellular calcium. The kainate, at the same concentration of NMDA, is less effective and no degradation of fodrin is observed after exposure of cerebellar neurons to quisqualate. These findings suggest that calcium/calpain I-dependent fodrin proteolysis is selectively associated to the functional activation of NMDA receptors.