Biology subjects

Philibert, C. E.

Publications and source records attributed to Philibert, C. E..

3 recordsLinked to original sources

bioRxiv2024

Direct detection of endogenous Gαi activity in cells with a sensitive conformational biosensor

Activation of heterotrimeric G-proteins (G{beta}{gamma}) by G-protein-coupled receptors (GPCRs) is not only a mechanism broadly used by eukaryotes to transduce signals across the plasma membrane, but also the target for a large fraction of clinical drugs. However, approaches typically used to assess this signaling mechanism by directly measuring G-protein activity, like optical biosensors, suffer from limitations. On one hand, many of these biosensors require expression of exogenous GPCRs and/or G-proteins, compromising readout fidelity. On the other hand, biosensors that measure endogenous signaling may still interfere with the signaling process under investigation or suffer from having a small dynamic range of detection, hindering broad applicability. Here, we developed an optical biosensor that detects the endogenous G-protein active species Gi-GTP upon stimulation of endogenous GPCRs more robustly than current state-of-the-art sensors for the same purpose. Its design is based on the principle of bystander Bioluminescence Resonance Energy Transfer (BRET) and leverages the Gi-binding protein named GINIP as a high affinity and specific detector module of the GTP-bound conformation of Gi. We optimized this design to prevent interference with Gi-dependent signaling (cAMP inhibition) and to enable implementation in different experimental systems with endogenous GPCRs, including neurotransmitter receptors in primary astroglial cells or opioid receptors in cell lines, which revealed opioid neuropeptide-mediated activation profiles different from those observed with other biosensors involving exogenous GPCRs and G-proteins. Overall, we introduce a biosensor that directly and sensitively detects endogenous activation of G-proteins by GPCRs across different experimental settings without interfering with the subsequent propagation of signaling.

pharmacology and toxicology↗

bioRxiv2024

Chronic potentiation of metabotropic glutamate receptor 2 with a nanobody accelerates amyloidogenesis in Alzheimer's disease.

Immunotherapy of Alzheimers disease (AD) is a promising approach to reduce the accumulation of amyloid-beta (A{beta}), a critical event in the onset of the disease. Targeting the group II metabotropic glutamate receptors, mGlu2 and mGlu3, could be important in controlling A{beta} production, although their respective contribution remains unclear due to the lack of selective tools. Here, we show that enhancing mGlu2 receptor activity increases A{beta}1-42 peptide production whereas activation of mGlu3 has no effect. We show that such a difference likely results from the direct interaction of APP with mGlu3, but not with mGlu2 receptors, that prevents APP amyloidogenic cleavage and A{beta}1-42 peptides production. We then show that chronic treatments of the AD model 5xFAD mice with a brain-penetrating mGlu2-potentiating nanobody accelerated amyloid aggregation and exacerbated memory deficits, but had no effect in control mice. Our results confirm that a selective mGluR2 activation exacerbates AD disease development, suggesting that therapeutic benefices could be obtained with blockers of this receptor. Our study also provides the proof-of-concept that chronic administration of nanobodies targeting neuroreceptors can be envisioned to treat brain diseases.

neuroscience↗

bioRxiv2024

Direct interrogation of context-dependent GPCR activity with a universal biosensor platform

G protein-coupled receptors (GPCRs) are the largest family of druggable proteins in the human genome, but progress in understanding and targeting them is hindered by the lack of tools to reliably measure their nuanced behavior in physiologically-relevant contexts. Here, we developed a collection of compact ONE vector G-protein Optical (ONE-GO) biosensor constructs as a scalable platform that can be conveniently deployed to measure G-protein activation by virtually any GPCR with high fidelity even when expressed endogenously in primary cells. By characterizing dozens of GPCRs across many cell types like primary cardiovascular cells or neurons, we revealed new insights into the molecular basis for G-protein coupling selectivity of GPCRs, pharmacogenomic profiles of anti-psychotics on naturally-occurring GPCR variants, and G-protein subtype signaling bias by endogenous GPCRs depending on cell type or upon inducing disease-like states. In summary, this open-source platform makes the direct interrogation of context-dependent GPCR activity broadly accessible.

biochemistry↗