Biology subjects

Lebon, G.

Publications and source records attributed to Lebon, G..

3 recordsLinked to original sources

bioRxiv2024

A photoswitchable positive allosteric modulator to control the activation of the metabotropic glutamate receptor 5 by light

1.The metabotropic glutamate receptor 5 (mGlu5) is widely expressed in the brain, where it plays an important role in synaptic plasticity, learning and memory, making it a therapeutic target of interest in various neurological disorders. In this study, we developed a photoswitchable positive allosteric modulator (PAM) of the mGlu5, as a novel tool for this clinically relevant drug target. To that aim, we used an azologisation strategy of the mGlu5 PAM agonist VU0424465 leading to the molecule azoglurax. We observed a reversible photoisomerization of azoglurax in solution with optimal wavelengths of 365 nm and 435 nm for trans to cis and cis to trans isomerization, respectively. In cell-based assays, azoglurax potentiates the agonist-induced activity of mGlu5 with a sub-micromolar potency in the dark. This potency is reduced under UV illumination. Similar to its parent molecule, azoglurax acts as an allosteric agonist of mGlu5, activating the receptor in absence of glutamate, as demonstrated on a glutamate-insensitive mutant receptor. Docking and site-directed mutagenesis experiments also suggest that azoglurax and VU0424465 bind the same pocket. In addition, molecular dynamics on cis-azoglurax-bound mGlu5 suggests that it azoglurax cis isomer does not bind stably in the receptor, in contrast to the trans-isomer, explaining the difference of activity between the two isomers. In conclusion, azoglurax is the first mGlu5 photoswitchable PAM agonist reported to date, retaining the properties and the binding mode of its parent in the dark, while the insertion of an azobenzene confers light-regulated activity. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/629646v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@1e0c1f4org.highwire.dtl.DTLVardef@dd7e36org.highwire.dtl.DTLVardef@1892657org.highwire.dtl.DTLVardef@1343743_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO C_FIG

pharmacology and toxicology↗

bioRxiv2023

Conformational diversity in class C GPCR positive allosteric modulation

The metabotropic glutamate receptors (mGlus) are class C G protein coupled receptors (GPCR) that form obligate dimers activated by the major excitatory neurotransmitter L-glutamate1,2. The architecture of mGlu receptor comprises an extracellular Venus-Fly Trap domain (VFT) connected to a transmembrane domain (7TM) through a Cysteine-Rich Domain (CRD). The binding of L-glutamate in the VFTs and subsequent conformational change results in the signal being transmitted to the 7TM inducing G-protein binding and activation 3-6. The mGlu receptors signal transduction can be allosterically potentiated by positive allosteric modulators (PAMs) binding to the 7TMs, which are of therapeutic interest in various neurological disorders7-9. Here, we report the cryoEM structures of metabotropic glutamate receptor 5 (mGlu5) purified with three chemically and pharmacologically distinct PAMs. We find that PAMs modulate the receptor equilibrium through their different binding modes, revealing how their interactions in the 7TMs impact the mGlu5 receptor conformational landscape and function. In addition, we identified a PAM-free but agonist-bound intermediate state that is stabilised by interactions mediated by intracellular loop 2. The activation of mGlu5 receptor is a multi-step sequential process in which the binding of the PAMs in the 7TM modulates the equilibrium towards the active state.

biochemistry↗

bioRxiv2019

Piezo1 is required for outflow tract and aortic valve development.

Aims-During embryogenesis, the onset of circulatory blood flow generates a variety of hemodynamic forces which reciprocally induce changes in cardiovascular development and performance. It has been known for some time that these forces can be detected by as yet unknown mechanosensory systems which in turn promote cardiogenic events such as outflow tract and aortic valve development. PIEZO1 is a mechanosensitive ion channel present in endothelial cells where it serves to detect hemodynamic forces making it an ideal candidate to play a role during cardiac development. We sought to determine whether PIEZO1 is required for outflow tract and aortic valve development. Methods and results-By analysing heart development in zebrafish we have determined that piezo1 is expressed in the developing outflow tract where it serves to detect hemodynamic forces. In particular, we have found that mechanical forces generated during the cardiac cycle activate Piezo1 which triggers nitric oxide to be released in the outflow tract. Consequently, disrupting Piezo1 signalling leads to defective outflow tract and aortic valve development and indicates this gene may be involved in the etiology of congenital heart diseases. Based on these findings, we analysed genomic data generated from a cohort of bicuspid aortic valve patients and identified 3 probands who each harboured a novel variant in PIEZO1. Subsequent in vitro and in vivo assays indicates that these variants behave as dominant negatives leading to an inhibition of normal PIEZO1 mechanosensory activity and defective aortic valve development. Conclusion-These data indicate that the mechanosensitive ion channel piezo1 is required for OFT and aortic valve development and, furthermore, dominant negative variants of PIEZO1 appear to be associated with BAV in humans.

developmental biology↗