Calpain-mediated truncation of rat brain AMPA receptors increases their Triton X-100 solubility

Previous studies have indicated that calpain activation results in the trun cation of the C-terminal domains of AMPA and NMDA receptor subunits. The pr esent study determined the distribution of the truncated species of the sub units between Triton-soluble and -insoluble fractions. Western blots were p erformed with various antibodies to quantify the amounts of the various spe cies of GluR1, GluR2, GluR3 and NR2B subunits. The results indicate that ca lpain activation decreased the amount of all the intact subunits in Triton- insoluble fractions. Calpain-generated truncated forms of GluR1 and GluR2, but not NR2B, were absent in these fractions, and were recovered in Triton- soluble fractions. These findings suggest that calpain-mediated truncation of AMPA but not NMDA receptor C-terminal domains results in modifications o f the interactions between the receptors and postsynaptic densities, and th at this mechanism could be involved in activity-dependent changes in the su bcellular distribution of AMPA receptors. (C) 2000 Elsevier Science B.V. Al l rights reserved.