GSK-3 beta activation is required for ZIP-induced disruption of learned fear

Abstract

The myristoylated zeta inhibitory peptide (ZIP), which was originally developed as a protein kinase C/M zeta (PKC zeta/PKM zeta) inhibitor, is known to produce the loss of different forms of memories. However, ZIP induces memory loss even in the absence of PKM zeta, and its mechanism of action, therefore, remains elusive. Here, through a kinome-wide screen, we found that glycogen synthase kinase 3 beta (GSK-3 beta) was robustly activated by ZIP in vitro. ZIP induced depotentiation (a cellular substrate of memory erasure) of conditioning-induced potentiation at LA synapses, and the ZIP-induced depotentiation was prevented by a GSK-3 beta inhibitor, 6-bromoindirubin-3-acetoxime (BIO-acetoxime). Consistently, GSK-3 beta inhibition by BIO-acetoxime infusion or GSK-3 beta knockdown by GSK-3 beta shRNA in the LA attenuated ZIP-induced disruption of learned fear. Furthermore, conditioned fear was decreased by expression of a non-inhibitable form of GSK-3 beta in the LA. Our findings suggest that GSK-3 beta activation is a critical step for ZIP-induced disruption of memory.