Abstract
The myristoylated zeta inhibitory peptide (ZIP), which was originally developed as a protein kinase C/Mζ (PKCζ/PKMζ) inhibitor, is known to produce the loss of different forms of memories. However, ZIP induces memory loss even in the absence of PKMζ, and its mechanism of action, therefore, remains elusive. Here, through a kinome-wide screen, we found that glycogen synthase kinase 3 beta (GSK-3β) 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-3β inhibitor, 6-bromoindirubin-3-acetoxime (BIO-acetoxime). Consistently, GSK-3β inhibition by BIO-acetoxime infusion or GSK-3β knockdown by GSK-3β 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-3β in the LA. Our findings suggest that GSK-3β activation is a critical step for ZIP-induced disruption of memory.
Highlights
The myristoylated zeta inhibitory peptide (ZIP), which was originally developed as a protein kinase C/ Mζ (PKCζ/protein kinase Mζ (PKMζ)) inhibitor, is known to produce the loss of different forms of memories
Several kinases have been implicated in Long-term potentiation (LTP): Ca2+/calmodulin-dependent protein kinase II (CaMKII), mitogen-activated protein kinase (MAPK), protein kinase A (PKA), and protein kinase C (PKC)[2]
Our findings suggest that activated GSK-3β is a key off-target effector of ZIP and contributes to ZIP-induced memory disruption
Summary
The myristoylated zeta inhibitory peptide (ZIP), which was originally developed as a protein kinase C/ Mζ (PKCζ/PKMζ) inhibitor, is known to produce the loss of different forms of memories. ZIP application in the knockout mice induces L-LTP reveral[29,31] and memory disruption[29,30,31] as it does in wild type mice In these studies, a scrambled version of ZIP (SCR-ZIP), which has been used frequently as a control d rug[15,20,25,32], has effects on PKMζ activity, L-LTP and memory that are similar to those of ZIP, suggesting that SCR-ZIP may not be an ideal control for ZIP. Inhibition of PKCι/λ by shRNA reversed L-LTP and impaired long-term memory in PKMζ-knockout m ice[33] Together, these findings raise the question of whether ZIP targets molecules other than PKMζ
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