PKMζ maintains memories by regulating GluR2-dependent AMPA receptor trafficking

The maintenance of long-term memory in hippocampus, neocortex and amygdala requires the persistent action of the atypical protein kinase C isoform, protein kinase M zeta (PKM zeta). We found that inactivating PKM zeta in the amygdala impaired fear memory in rats and that the extent of the impairment was positively correlated with a decrease in postsynaptic GluR2. Blocking the GluR2-dependent removal of postsynaptic AMPA receptors abolished the behavioral impairment caused by PKM zeta inhibition and the associated decrease in postsynaptic GluR2 expression, which correlated with performance. Similarly, blocking this pathway for removal of GluR2-containing receptors from postsynaptic sites in amygdala slices prevented the reversal of long-term potentiation caused by inactivating PKM zeta. Similar behavioral results were obtained in the hippocampus for unreinforced recognition memory of object location. Together, these findings indicate that PKM zeta maintains long-term memory by regulating the trafficking of GluR2-containing AMPA receptors, the postsynaptic expression of which directly predicts memory retention.