Biology subjects

Thibeault, P. E.

Publications and source records attributed to Thibeault, P. E..

5 recordsLinked to original sources

bioRxiv2026

Liver-specific loss of the transcriptional coregulator ARGLU1 protects against diet-induced obesity in mice through decreased lipid absorption

New medications that decrease food intake show promise in addressing the global obesity epidemic; however, additional therapies are needed for patients who are intolerant or unresponsive to these drugs. ARGLU1 is a transcriptional coregulator of several nuclear receptors. Herein, we detail the discovery that mice lacking ARGLU1 in hepatocytes (LKO) are resistant to diet-induced obesity, with no difference in food intake, locomotion, or energy expenditure compared to wildtype mice. Interestingly, LKO mice exhibited decreased CYP8B1, corresponding to fewer 12-hydroxylated bile acids, increasing the relative hydrophobicity of bile which decreases lipid emulsification. Notably, LKO mice have lower plasma and liver cholesterol levels, attributed to impaired lipid absorption. Furthermore, LKO mice showed preferential use of fatty acids as their fuel source. Herein, we establish a mechanistic basis for resistance of ARGLU1 LKO mice to diet-induced obesity, identifying a potential new molecular target for obesity.

physiology↗

bioRxiv2025

Helix-8 and Carboxyl Terminal Tail Regulation of Proteinase Activated Receptor-4 (PAR4) signalling

The 8th-helix (H8) and carboxyl terminal tail (CT) of GPCRs are crucial for interactions with intracellular signaling molecules and regulatory proteins. We investigated how H8 and CT residues influence signaling in PAR4, a tethered-ligand activated GPCR. Our analysis revealed that PAR4 activation by thrombin or AYPGKF-NH2 stimulates {beta}-arrestin-1/-2 recruitment and activates multiple G proteins (Gq, G11, Gz, G15, G12, G13, Gi1-3, GoA/B). Mutation of the H8 sequence (R352AGLFQRS359) significantly reduced G protein activation and {beta}-arrestin recruitment, with residues Leu355-Glu357 being particularly important. Mutations of specific lysine residues in H8 and CT also impaired signaling. Additionally, we identified a crucial TM7-H8 interaction and found that CT phosphorylation sites regulate {beta}-arrestin recruitment. Finally, using AlphaFold3 we predicted interactions between PAR4, {beta}-arrestins, and G proteins, revealing novel receptor regulatory sites in the intracellular loops, transmembrane domains, H8 and CT.

pharmacology and toxicology↗

bioRxiv2021

S. aureus-serine protease-like protein B (SplB) activates PAR2 and induces endothelial barrier dysfunction

Withdrawal StatementThe authors have withdrawn their manuscript owing to the following reason: Unfortunately, the preparation of the recombinant serine protease-like protein B (SplB) used in this study was found to contain impurities, so that the effects presented cannot be unambiguously attributed to the protease SplB. We therefore retract the manuscript from bioRxiv. We apologize for any inconvenience this may have caused. Therefore, the authors do not wish this work to be cited as reference for the project. We want to clarify that the issue was identified in the preparation of the SplB protein and does not reflect on the contributions of individual authors. If you have any questions, please contact the corresponding author.

immunology↗

bioRxiv2020

Role of the C-terminal tail in regulating Proteinase Activated Receptor 2 (PAR2) signalling

The C-terminal tail of G-protein-coupled receptors contain important regulatory sites that enable interaction with intracellular signalling effectors. Here we examine the relative contribution of the C-tail serine/threonine phosphorylation sites (Ser383-385, Ser387-Thr392) and the helix-8 palmitoylation site (Cys361) in signalling regulation downstream of the proteolytically-activated GPCR, PAR2. We examined Gq/11-coupled calcium signalling, {beta}-arrestin-1/-2 recruitment, and MAPK activation (p44/42 phosphorylation) by wild-type and mutant receptors expressed in a CRISPR/Cas9 PAR2-knockout HEK-293 cell background. We find that alanine substitution of the membrane proximal serine residues (Ser383-385Ala) had no effect on SLIGRL-NH2- or trypsin-stimulated {beta}-arrestin recruitment. Alanine substitutions in the Ser387-Thr392 cluster resulted in a large ([~]50%) decrease in {beta}-arrestin-1/2 recruitment triggered by the activating peptide, SLIGRL-NH2, but was without effect on trypsin-activated {beta}-arrestin-1/-2 recruitment. Additionally, we find that alanine substitution of the helix-8 cysteine residue (Cys361Ala) led to a ([~]50%) decrease in {beta}-arrestin-1/-2 recruitment in response to both trypsin and SLIGRL-NH2. We further show that Gq/11inhibition with YM254890, inhibited ERK phosphorylation by PAR2 agonists, while genetic deletion of {beta}-arrestin-1/-2 by CRISPR/Cas9 enhanced MAPK activation. Knockout of {beta}-arrestins also enhanced Gq/11-mediated calcium signalling. In line with these findings, C-tail serine/threonine and cysteine residue mutants that have decreased {beta}-arrestin recruitment also showed enhanced ERK activation. Thus, our studies point to multiple mechanisms that regulate {beta}-arrestin interaction with PAR2 to regulate receptor-mediated signalling.

pharmacology and toxicology↗

bioRxiv2019

Proteinase-Activated Receptor 4 (PAR4) Activation Triggers Cell Membrane Blebbing through RhoA and β-arrestin

Proteinase-Activated Receptors (PARs) are a four-member family of G-protein coupled receptors that are activated via proteolysis. PAR4 is a member of this family that is cleaved and activated by serine proteinases such as thrombin, trypsin and cathepsin-G. PAR4 is expressed in a variety of tissues and cell types including platelets, vascular smooth muscle cells and neuronal cells. In studying PAR4 signalling and trafficking, we observed dynamic changes in the cell membrane with spherical membrane protrusions that resemble plasma membrane blebbing. Since non-apoptotic membrane blebbing is now recognized as an important regulator of cell migration, cancer cell invasion, and vesicular content release we sought to elucidate the signalling pathway downstream of PAR4 activation that leads to such events. Using a combination of pharmacological inhibition and CRISPR/Cas9-mediated gene-editing approaches we establish that PAR4-dependent membrane blebbing occurs independently of the Gq/11 and Gi signalling pathways and is dependent on signalling via the {beta}-arrestin-1/-2 and RhoA signalling pathways. In order to gain a more comprehensive understanding of {beta}-arrestin-mediated signalling downstream of PAR4 and to guide future studies, we undertook RNA-seq analysis of PAR4 activated genes in control cells and in cells lacking {beta}-arrestin-1/-2. A list of differentially expressed genes was generated followed by Gene Ontology (GO) and enrichment analysis, revealing PAR4 regulation of genes involved in processes including blood coagulation and circulation, cell-cell adhesion, sensory perception and neuron-neuron synaptic transmission-terms that relate back to known functions of PAR4 and are consistent with our finding of membrane blebbing triggered by PAR4 activation. Together these studies provide further mechanistic insight into PAR4 regulation of cellular function.\n\nSignificance StatementWe find that the thrombin receptor PAR4 triggers cell membrane blebbing in a RhoA- and {beta}-arrestin-dependent manner. In addition to identifying novel cellular responses mediated by PAR4, these data provide further evidence for biased signaling in PAR4 since membrane blebbing was dependent on some, but not all, signaling pathways activated by PAR4. Finally through CRISPR/Cas9-mediated targeting and RNA-seq analysis we catalogue here PAR4-dependent transcription that is dependent on {beta}-arrestin.

pharmacology and toxicology↗