Biology subjects

Hirschberg, S.

Publications and source records attributed to Hirschberg, S..

4 recordsLinked to original sources

bioRxiv2022

Noradrenergic cross-modular reciprocal inhibition within the Locus Coeruleus.

The Locus Coeruleus (LC) is the primary noradrenergic nucleus in the brain with widespread projections driving changes in cognitive state and animal behaviour. The LC is composed of multiple "modules" with specific efferent target domains enabling discretional neuromodulation. LC neuronal activity releases noradrenaline within the nucleus as a local feedback mechanism, but it is not known how this influences modular output. We address this question using whole-cell recordings and calcium imaging in rat pontine slices in combination with LC neuronal ensemble modelling to assess the influence of local noradrenaline release on cross-modular interactions. Electrophysiological recordings of LC neurons from rats transduced with the optogenetic actuator ChR2 showed auto-inhibition and lateral inhibition (of surrounding non-transduced neurons). This inhibition was strongly frequency dependent and was mediated by noradrenaline acting on alpha2-adrenceptors (2R). To allow calcium-imaging of LC neuronal ensembles a Canine-Adenoviral vector strategy was developed using the PRS promoter to drive selective expression GCaMP6s. Calcium imaging allowed resolution of both increases and decreases in LC activity (to TTX / clonidine or high potassium). Selective chemogenetic-activation of subsets of LC neurons (expressing the ionotropic actuator PSAM) revealed both a direct excitation (after application of PSEM308, 3-30{micro}M) and an 2R-mediated inhibition of neighbouring LC cells (non-transduced). Differential retrograde targeting of PSAM or GCaMP6s to specific LC modules showed the presence of strong, reciprocal cross-modular inhibition (shown for the LC-olfactory bulb vs LC bulbospinal modules) and a subsequent rebound activity inversion. This represents a preferential, targeted, cross-modular, lateral inhibition within the LC rather than a non-specific surround inhibition. Computational modelling showed the emergence of lateral inhibition and biphasic responses to modular activation when 2R signalling and noradrenergic reuptake saturation were included. This interaction may facilitate recruitment of neuronal ensembles by coherent inputs and represents a bottom-up differential contrast-enhancement mechanism within the LC to produce a modality specific focus.

neuroscience↗

bioRxiv2022

SARS-CoV-2 neutralizing camelid heavy-chain-only antibodies as powerful tools for diagnostic and therapeutic applications

IntroductionThe ongoing COVID-19 pandemic situation caused by SARS-CoV-2 and variants of concern such as B.1.617.2 (Delta) and recently, B.1.1.529 (Omicron) is posing multiple challenges to humanity. The rapid evolution of the virus requires adaptation of diagnostic and therapeutic applications. ObjectivesIn this study, we describe camelid heavy-chain-only antibodies (hcAb) as useful for novel in vitro diagnostic assays and for therapeutic applications due to their neutralizing capacity. MethodsFive antibody candidates were selected out of a naive camelid library by phage display and expressed as full-length IgG2 antibodies. The antibodies were characterized by Western blot, enzyme-linked immunosorbent assays, surface plasmon resonance with regard to their specificity to the recombinant SARS-CoV-2 Spike protein and to SARS-CoV-2 virus-like particles. Neutralization assays were performed with authentic SARS-CoV-2 and pseudotyped viruses (wildtype and Omicron). ResultsAll antibodies efficiently detect recombinant SARS-CoV-2 Spike protein and SARS-CoV-2 virus-like particles in different ELISA setups. The best combination was shown with hcAb B10 as catcher antibody and HRP-conjugated hcAb A7.2 as the detection antibody. Further, four out of five antibodies potently neutralized authentic wildtype SARS-CoV-2 and particles pseudotyped with the SARS-CoV-2 Spike proteins of the wildtype and Omicron variant, sublineage BA.1 at concentrations between 0.1 and 0.35 ng/mL (ND50). ConclusionCollectively, we report novel camelid hcAbs suitable for diagnostics and potential therapy. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

immunology↗

bioRxiv2020

C-terminal-dependent control of EAAT2 signaling, corticostriatal synaptic glutamate clearance and spontaneous motor activity in mice with hypokinesia

Rapid removal of glutamate from the sites of glutamate release is an essential step in excitatory synaptic transmission. Despite many years of research, the molecular mechanisms underlying the intracellular regulation of glutamate transport at tripartite synapses have remained unclear. This limits the options for pharmacological treatment of motor disorders associated with glutamate excitotoxicity. Therefore, using the Q175 mouse model of Huntingtons disease (HD), we explored the effects of structural changes in the astrocytic excitatory amino acid transporter type 2 (EAAT2). We report that expression of a C-terminal-modified variant of EAAT2 can alleviate the symptoms of hypokinesia in mice with already advanced HD. At a cellular level, this beneficial outcome correlated with faster synaptic glutamate clearance, higher astrocytic glutamate uptake and larger amounts of native EAAT2 protein. Proteomics data indicate a partial reversal of HD-induced changes in the EAAT2 interactor spectrum. Thus, astrocytic glutamate transport remains a target for therapeutic intervention.

neuroscience↗

bioRxiv2017

Engagement of spinal- vs prefrontal-projecting locus coeruleus neurons parses analgesia from aversion & anxiety in rats

The locus coeruleus (LC) projects throughout the brain and spinal cord and is the major source of central noradrenaline. It remains unclear whether the LC acts functionally as a single global effector or as discrete modules. Specifically, while spinal-projections from LC neurons can exert analgesic actions, it is not known whether they can act independently of ascending LC projections. Using viral vectors taken up at axon terminals, we expressed chemogenetic actuators selectively in LC neurons with spinal (LC:SC) or prefrontal cortex (LC:PFC) projections. Activation of the LC:SC module produced robust, lateralised analgesia while activation of LC:PFC produced aversion. In a neuropathic pain model, LC:SC activation reduced hind-limb sensitization and induced conditioned place preference. By contrast, activation of LC:PFC exacerbated spontaneous pain, produced aversion and increased anxiety-like behaviour. This independent, contrasting modulation of pain-related behaviours mediated by distinct noradrenergic modules provides evidence for a discrete functional organisation of the LC.

neuroscience↗