Publications

Purpose: To interrogate animal physiology in vivo, there is a lack of non-genetic methods to control the activity of endogenous proteins with pharmacological and spatiotemporal precision. To address this need, we recently developed targeted covalent photoswitchable (TCP) compounds that enable the remote control of endogenous glutamate receptors (GluRs) using light. Methods: We combine the photopharmacological effector TCP9 with neuronal activity sensors to demonstrate all-optical reversible control of endogenous GluRs across multiple spatiotemporal scales in rat brain tissue ex vivo and in Xenopus tadpole brains in vivo. Findings: TCP9 allows photoactivation of neuronal ensembles, individual neurons, and single synapses in ex vivo tissue and in intact brain in vivo, which is challenging using optogenetics and neurotransmitter uncaging. TCP9 covalently targets AMPA and kainate receptors, maintaining their functionality and photoswitchability for extended periods (>8 h) after a single compound application. This allows tracking endogenous receptor physiology during synaptic plasticity events such as the reduction of functional AMPA receptors during long-term depression in hippocampal neurons. Conclusion: TCP9 is a unique non-invasive tool for durable labeling, reversible photoswitching, and functional tracking of native receptors in brain tissue without genetic manipulation.

JTD Keywords: 2-photon, Ampa receptors, Ampar, Azobenzene, Caged glutamate, Calcium imaging, Covalent drug, Dendritic spines, Hippocampus, Kainate, Long-term depression, Optical control, Optopharmacology, Photopharmacology, Photoswitch, Plasticity, Proteins, Pulse-chase, Rat, Subunit, Surface expression, Synaptic ampa, Xenopus

Dopaminergic neurotransmission is involved in several important brain functions, such as motor control, learning, reward-motivated behavior, and emotions. Dysfunctions of dopaminergic system may lead to the development of various neurological and psychiatric disorders, like Parkinson's disease, schizophrenia, depression, and addictions. Despite years of sustained research, it is not fully established how dopaminergic neurotransmission governs these important functions through a relatively small number of neurons that release dopamine. Light-driven neurotechnologies, based on the use of small light-regulated molecules or overexpression of light-regulated proteins in neurons, have greatly contributed to the advancement of our understanding of dopaminergic circuits and our ability to control them selectively. Here, we overview the current state-of-the-art of light-driven control of dopaminergic neurotransmission. While we provide a concise guideline for the readers interested in pharmacological, pharmacogenetic, and optogenetic approaches to modulate dopaminergic neurotransmission, our primary focus is on the usage of photocaged and photo-switchable small dopaminergic molecules. We argue that photopharmacology, photoswitchable molecules of varied modalities, can be employed in a wide range of experimental paradigms, providing unprecedent insights into the principles of dopaminergic control, and represent the most promising light-based therapeutic approach for spatiotemporally precise correction of dopamine-related neural functions and pathologies.

JTD Keywords: Activation, Azobenzene, Caged compounds, Caged ligands, Catecholamine, D1, D2, Dendritic spines, Dopamine, Mechanisms, Neuromodulation, Neuronal circuits, Optogenetics, Optopharmacology, Phasic dopamine, Photoisomerization, Photolysi, Photopharmacology, Photoswitc, Protein-coupled receptors, Release

In Alzheimer's disease, fibrillar tau pathology accumulates and spreads through the brain and synapses are lost. Evidence from mouse models indicates that tau spreads trans-synaptically from pre- to postsynapses and that oligomeric tau is synaptotoxic, but data on synaptic tau in human brain are scarce. Here we used sub-diffraction-limit microscopy to study synaptic tau accumulation in postmortem temporal and occipital cortices of human Alzheimer's and control donors. Oligomeric tau is present in pre- and postsynaptic terminals, even in areas without abundant fibrillar tau deposition. Furthermore, there is a higher proportion of oligomeric tau compared with phosphorylated or misfolded tau found at synaptic terminals. These data suggest that accumulation of oligomeric tau in synapses is an early event in pathogenesis and that tau pathology may progress through the brain via trans-synaptic spread in human disease. Thus, specifically reducing oligomeric tau at synapses may be a promising therapeutic strategy for Alzheimer's disease.Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.

JTD Keywords: accumulation, alpha-synuclein, array tomography, cognitive impairment, dendritic spines, mouse model, neurodegeneration, neurons, synapses, Alzheimer, Amyloid-beta, Synapse, Tau

Synaptic plasticity involves structural modifications in dendritic spines that are modulated by local protein synthesis and actin remodeling. Here, we investigated the molecular mechanisms that connect synaptic stimulation to these processes. We found that the phosphorylation of isoform-specific sites in eEF1A2-an essential translation elongation factor in neurons-is a key modulator of structural plasticity in dendritic spines. Expression of a nonphosphorylatable eEF1A2 mutant stimulated mRNA translation but reduced actin dynamics and spine density. By contrast, a phosphomimetic eEF1A2 mutant exhibited decreased association with F-actin and was inactive as a translation elongation factor. Activation of metabotropic glutamate receptor signaling triggered transient dissociation of eEF1A2 from its regulatory guanine exchange factor (GEF) protein in dendritic spines in a phosphorylation-dependent manner. We propose that eEF1A2 establishes a cross-talk mechanism that coordinates translation and actin dynamics during spine remodeling.

JTD Keywords: cytoskeleton, expression, f-actin, factor 1-alpha, factor 1a, messenger-rna, nucleotide exchange, protein-synthesis, synaptic plasticity, Actin cytoskeleton, Actins, Aminoacyl-transfer-rna, Dendritic spines, Neuronal plasticity, Neurons, Peptide elongation factor 1, Protein biosynthesis