Overactive Neuronal eEF2K/eEF2 signaling is associated with cognitive impairment and apathy-like behavior

Dysregulated protein synthesis has been implicated in multiple neurodevelopmental, neurodegenerative, and neuropsychiatric diseases. Protein synthesis or mRNA translation is critically regulated through phosphorylation of eukaryotic elongation factor 2 (eEF2) by its kinase eEF2K. Increased eEF2K activity leads to elevated phosphorylation and inhibition of eEF2 and inhibits the elongation phase of protein synthesis. Recent studies suggest a link between eEF2 hyper-phosphorylation and several neuronal diseases characterized by cognitive impairments. Phosphorylation of eEF2 by eEF2K has also been implicated as a molecular mechanism for the rapid antidepressant effect of ketamine. Whether there exists a causal relationship between overactive eEF2K/eEF2 signaling and impaired synaptic and cognitive function remains unknown. To fill this critical knowledge gap, we generated a transgenic mouse model (eEF2K-cKI) overexpressing eEF2K in excitatory neurons to investigate how eEF2K/eEF2 signaling can impact cognitive functions and neuropsychiatric behaviors. We assessed hippocampal-dependent learning and memory, as well as multiple neuropsychiatric domains associated with a depressive phenotype including despair, anhedonia, apathy, anxiety, and sociability. The eEF2K-cKI mice exhibit learning and memory impairments, and robust apathy-like phenotype without other despair/depression-like behaviors. We also found impaired long-term potentiation and altered dendritic spine and synaptic morphology in the hippocampus of the eEF2K-cKI mice. Proteomic analysis revealed changes in levels of proteins associated with neuropsychiatric and neurodegenerative disorders. Our findings present direct evidence supporting the pathophysiological role of aberrant eEF2K/eEF2 signaling in brain function and help provide insight into novel mechanisms and therapeutic avenues for neuronal diseases characterized by dementia and neuropsychiatric symptoms.