Calpain-mediated degradation of PSD-95 in developing and adult rat brain

PSD-95 is a major postsynaptic density protein that is degraded as a result of synaptic activity. We used four different methods to test the hypothesi s that calpain is involved in PSD-95 turnover. Treatment of synaptic membra nes with purified calpain resulted in a decrease in immunoreactivity of the native 95 kDa protein and the appearance of two smaller molecular weight s pecies, migrating at 50 and 36 kDa, respectively. Calcium treatment of froz en-thawed brain sections produced an identical digestion pattern, an effect blocked by calpain inhibitors. N-methyl-D-aspartate treatment of organotyp ic hippocampal cultures produced truncation of PSD-95 and accumulation of t he 36 kDa species. Finally, calpain-generated degradation products of PSD95 were prominent in neonatal hippocampus, and disappeared with postnatal dev elopment. Our data suggest that PSD-95 is a substrate for calpain, and that calpain-mediated truncation contributes to PSD-95 turnover. (C) 2000 Elsev ier Science Ireland Ltd. All rights reserved.