The first change in the brains of patients with Alzheimer’s disease (AD) and the best biomarker of the disease is synaptic loss. The molecular pathways preceding synaptic loss during AD are still unclear but mounting evidence suggest that loss of PSD-95 is one of the first events leading to synaptic loss as it is significantly depleted in the brains AD patients as well as in neurons exposed to amyloid-beta (Aβ). We discovered that elevated levels of PSD-95 (under a number of different conditions) can protect against, and even reverse, synaptic weakening by Aβ. Because PSD-95 requires palmitoylation to remain at a synapse, we tested if pharmacological blockade of PSD-95 depalmitoylating enzyme, ABHD17, could increase synaptic resilience. In vitro experiments showed that Palmostatin B (an ABHD17 inhibitor), could rescue Aβ-induced synaptic depression and Aβ-mediated effects on dendritic spines. Interestingly, we saw that PSD-95 palmitoylation is significantly reduced in APP/PS1 mice, which might indicate a previously unknown step in the pathophysiology of AD. Palmostatin B injections in the intraperitoneal cavity rapidly rescued palmitoylated PSD-95 in a dose dependent manner in APP/PS1 mice, indicating that this drug can access brain synapses in vivo. Furthermore, preliminary data suggests that Palmostatin B can rescue memory deficits in the Morris Water Maze behavioral test. Consequently, PSD-95 depalmitoylating enzyme could be an exciting new drug target against AD.
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