Kobi Rosenblum

Alzheimer’s disease (AD) is a complex neurodegenerative disorder characterized by synaptic failure, cognitive impairment and neuropsychiatric symptoms (NPS). Apathy is the most common NPS seen in AD patients, and its underlying mechanisms remain unknown. Here, we investigated the roles of neuronal eukaryotic elongation factor 2 (eEF2) phosphorylation (by its kinase eEF2K) in AD-associated cognitive deficits and NPS. We performed a series of experiments using a multidisciplinary approach including genetics, behavioral assays, synaptic electrophysiology, and unbiased proteomics. The results demonstrated that neuron-specific inhibition of eEF2K and eEF2 phosphorylation can alleviate cognitive deficits, synaptic plasticity impairments, and apathy-like behavior in aged APP/PS1 AD model mice. Our findings indicate the therapeutic potential of targeting the eEF2K signaling in the treatment of dementia and NPS in AD and related dementias (ADRDs).

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.

Measuring precise emotional tagging for taste information, with or without the use of words, is challenging. While affective taste valence and salience are core components of emotional experiences, traditional behavioral assays for taste preference, which often rely on cumulative consumption, lack the resolution to distinguish between different affective states, such as innate versus learned aversion, which are known to be mediated by distinct neural circuits. To overcome this limitation, we developed an open-source system for high-resolution microstructural analysis of licking behavior in freely moving mice. Our approach integrates traditional lick burst analysis with a proprietary software pipeline that utilizes interlick interval (ILI) distributions and principal component analysis (PCA) to create a multidimensional behavioral profile of the animal. Using this system, we characterized the licking patterns associated with innate appetitive, aversive, and neutral tastants. While conventional burst analysis failed to differentiate between two palatable stimuli (water and saccharin), our multidimensional approach revealed distinct and quantifiable behavioral signatures for each. Critically, this approach successfully dissociates innate and learned aversive taste valences, a distinction that cannot be achieved using standard metrics. By providing the designs for our custom-built setup and analysis software under an open-source license, this study offers a comprehensive and accessible methodology for examining hedonic responses in future studies. This powerful toolkit enhances our understanding of sensory valence processing and provides a robust platform for future investigations of the neurobiology of ingestive behavior.

Peptide drug technologies offer powerful approaches to develop potent and selective lead molecules for therapeutic and research applications. However, new and optimized delivery approaches are necessary to overcome current pitfalls including fast degradation in cells and tissue. Extracellular signal-regulated kinases 1/2 (ERK1/2) exemplifies proteins that play crucial and varied roles within distinct cellular compartments. Here, we established an innovative method, based on viral vectors, which utilizes the endogenous biogenesis of neurotrophins to deliver and express a biologically active peptide to attenuate specifically ERK1/2 nuclear functions in specific brain area of the adult forebrain. In contrast to our hypothesis, nuclear functions of ERK1/2 in the forebrain are fundamental for the extinction of associative-aversive memories, but not for acquisition, nor for retrieval of these memories. Our research demonstrates the feasibility and applicability of viral vectors to deliver a peptide of interest to manipulate specific molecular processes and/or protein interactions in specific tissue.

To protect the body from infections, the brain has evolved the ability to coordinate behavioral and immunological responses. The conditioned immune response (CIR) is a form of Pavlovian conditioning wherein a sensory (for example, taste) stimulus, when paired with an immunomodulatory agent, evokes aversive behavior and an anticipatory immune response after re-experiencing the taste. Although taste and its valence are represented in the anterior insular cortex and immune response in the posterior insula and although the insula is pivotal for CIRs, the precise circuitry underlying CIRs remains unknown. Here, we demonstrated that a bidirectional circuit connecting the anterior and posterior (aIC–pIC) insula mediates the CIR in male mice. Retrieving the behavioral dimension of the association requires activity of aIC-to-pIC neurons, whereas modulating the anticipatory immunological dimension requires bidirectional projections. These results illuminate a mechanism by which experience shapes interactions between sensory internal representations and the immune system. Moreover, this newly described intrainsular circuit contributes to the preservation of brain-dependent immune homeostasis.

Activation of neuronal protein synthesis upon learning is critical for the formation of long-term memory. Here, we report that learning in the contextual fear conditioning paradigm engenders a decrease in eIF2α (eukaryotic translation initiation factor 2) phosphorylation in astrocytes in the hippocampal CA1 region, which promotes protein synthesis. Genetic reduction of eIF2α phosphorylation in hippocampal astrocytes enhanced contextual and spatial memory and lowered the threshold for the induction of long-lasting plasticity by modulating synaptic transmission. Thus, learning-induced dephosphorylation of eIF2α in astrocytes bolsters hippocampal synaptic plasticity and consolidation of long-term memories.

Biological aging can be described as accumulative, prolonged metabolic stress and is the major risk factor for cognitive decline and Alzheimer’s disease (AD). Recently, we identified and described a quinone reductase 2 (QR2) pathway in the brain, in which QR2 acts as a removable memory constraint and metabolic buffer within neurons. QR2 becomes overexpressed with age, and it is possibly a novel contributing factor to age-related metabolic stress and cognitive deficit. We found that, in human cells, genetic removal of QR2 produced a shift in the proteome opposing that found in AD brains while simultaneously reducing oxidative stress. We therefore created highly specific QR2 inhibitors (QR2is) to enable evaluation of chronic QR2 inhibition as a means to reduce biological age–related metabolic stress and cognitive decline. QR2is replicated results obtained by genetic removal of QR2, while local QR2i microinjection improved hippocampal and cortical-dependent learning in rats and mice. Continuous consumption of QR2is in drinking water improved cognition and reduced pathology in the brains of AD-model mice (5xFAD), with a noticeable between-sex effect on treatment duration. These results demonstrate the importance of QR2 activity and pathway function in the healthy and neurodegenerative brain and what we believe to be the great therapeutic potential of QR2is as first-in-class drugs.

Avoiding potentially harmful, and consuming safe food is crucial for the survival of living organisms. However, the perceived valence of sensory information can change following conflicting experiences. Pleasurability and aversiveness are two crucial parameters defining the perceived valence of a taste and can be impacted by novelty. Importantly, the ability of a given taste to serve as the conditioned stimulus (CS) in conditioned taste aversion (CTA) is dependent on its valence. Activity in anterior insula (aIC) Layer IV–VI pyramidal neurons projecting to the basolateral amygdala (BLA) is correlated with and necessary for CTA learning and retrieval, as well as the expression of neophobia toward novel tastants, but not learning taste familiarity. Yet, the cellular mechanisms underlying the updating of taste valence representation in this specific pathway are poorly understood. Here, using retrograde viral tracing and whole-cell patch-clamp electrophysiology in trained mice, we demonstrate that the intrinsic properties of deep-lying Layer IV–VI, but not superficial Layer I–III aIC-BLA neurons, are differentially modulated by both novelty and valence, reflecting the subjective predictability of taste valence arising from prior experience. These correlative changes in the profile of intrinsic properties of LIV–VI aIC-BLA neurons were detectable following both simple taste experiences, as well as following memory retrieval, extinction learning, and reinstatement.