Biology subjects

Plouffe, B.

Publications and source records attributed to Plouffe, B..

8 recordsLinked to original sources

bioRxiv2026

A conserved hydrophobic interaction governs GPCR-transducer association

A central feature of G protein-coupled receptor (GPCR) desensitization is the direct competition between heterotrimeric G proteins and {beta}-arrestins ({beta}arrs) for an overlapping binding site within the intracellular receptor cavity. Although numerous high-resolution structures of GPCR-transducer complexes exist, the exact nature of this shared site and the molecular basis of transducer competition remain unclear. To investigate this, we employed an interdisciplinary approach integrating systemic mutational mapping, bioinformatics, and structural analysis across multiple classes of GPCRs and their transducers and regulators. We identified two highly conserved leucine residues within both the {beta}arr finger loop and the G C-terminal -helix, which engage a hydrophobic patch on GPCRs formed by TM3, TM5, and TM6 in a nearly identical manner, thereby stabilizing the complexes. Notably, the GPCR kinase N-terminal -helix also contains hydrophobic residues that associate with this same receptor patch and are vital for the GPCR-GRK engagement. Our findings reveal a conserved hydrophobic interface that mediates direct competition among GPCR transducers and regulators suggesting a universal mechanism that governs receptor access and desensitization.

biochemistry↗

bioRxiv2025

Plasma membrane rather than endosomal Gq signaling drives transcriptional activity by the viral chemokine receptor US28 in glioblastoma

US28 is a human cytomegalovirus-encoded chemokine receptor homologue that has high agonist-independent activity, internalizes constitutively, and plays an oncomodulatory role in glioblastoma. As G protein signaling was originally believed to strictly occur at the plasma membrane, it has been assumed that US28s constitutive Gq/11 signaling is mediated by a minor population at the plasma membrane. However, accumulating evidence shows that some GPCRs activate G proteins from intracellular organelles, such as endosomes. Importantly, endosomal rather than plasma membrane G protein signaling has been associated with transcriptional activity. Here, we demonstrate that the endosomal US28 population robustly activates Gq/11, and thus, provides the major contribution of Gq/11 signaling. Surprisingly, US28 signaling at the plasma membrane rather than from endosomes primarily drives upregulation of gene expression involved in cell proliferation and inflammatory responses that are associated with glioblastoma and cancer. Our findings highlight the crucial role of receptor signaling location in cellular responses.

cell biology↗

bioRxiv2025

Identification of a novel GREMLIN1 uptake pathway in epithelial cells that requires BMP binding

Gremlin1 is a member of a cysteine-knot containing family of secreted antagonists of bone morphogenetic protein signaling. GREM1 binding to BMP targets prevents their engagement with cognate BMP receptors, attenuating BMP-dependent gene expression. Some evidence suggests that GREM1 can directly bind to receptor tyrosine kinases on the plasma membrane, further complicating our understanding of GREM1 biology. To attempt to clarify the modalities of GREM1 signaling, we show that GREM1 protein is produced and secreted by intestinal fibroblasts and endocytosed by neighbouring epithelial cells. GREM1 uptake is a slow process and occurs by both clathrin- and caveolin-mediated endocytosis. Cell membrane heparin sulfate proteoglycans are required for GREM1 binding and uptake, and once internalised, GREM1 appears to localise to the early endosomes. Addition of BMP2 enhanced GREM1 uptake into cells. Remarkably, generation of a BMP-resistant GREM1 mutant abolished GREM1 uptake both in the presence and absence of BMP2. These data suggest that GREM1 binding and uptake into cells requires BMP binding, a process that may contribute to the antagonism of BMP signaling by GREM1. SummaryIn this article, we demonstrate differential GREM1 mRNA versus protein expression in mouse intestine. We also identify a novel GREM1 endocytosis pathway whereby mammalian cells take up GREM1 protein in what appears to be a BMP-dependent mechanism.

cell biology↗

bioRxiv2024

Multiple triggers converge to preferential effector coupling in the CB2R through a complex allosteric communication network

G protein-coupled receptors are important therapeutic drug targets for a wide range of diseases. Their ability to preferentially engage specific signaling pathways over others can be exploited to design drugs that target only disease-associated pathways leading to an improved safety profile. However, the underlying molecular mechanisms for preferential pathway engagement are complex and remain largely elusive. To elucidate the multifaceted actions at the receptor level that lead to preferential coupling, we employ a combination of techniques. Our approach integrates systematic mutagenesis of the CB2R and comprehensive profiling of Gi2 and {beta}-arrestin1 engagements with computer simulations to track mutant-induced impacts on receptor dynamics. Most importantly, our research discloses multiple triggers on a complex allosteric communication network (ACN) that converge to preferential CB2R coupling by modulating evolutionary conserved motifs (e.g., CWxP, NPxxY, sodium binding site). Potent triggers for a preferential Gi2 response exhibit high levels of connectivity and are located in proximity to connections with high information transmission. Our insights highlight the complexity of GPCR signaling and can guide the rational design of drug candidates tailored to evoke specific functional responses that can enhance the precision and efficacy of therapeutic interventions.

cell biology↗

bioRxiv2023

Structure of the human Duffy antigen receptor

The Duffy antigen receptor, also known as FY glycoprotein or CD234, is a seven transmembrane protein expressed primarily at the surface of red blood cells, which displays promiscuous binding to multiple chemokines. Not only does it serve as the basis of the Duffy blood group system but it also acts as the primary attachment site for malarial parasite Plasmodium vivax on erythrocytes and as one of the nucleating receptors for the pore forming toxins secreted by Staphylococcus aureus. Despite a predicted 7TM architecture and efficient binding to a spectrum of chemokines, it fails to exhibit canonical second messenger response such as calcium release, likely due to a lack of G protein coupling. Unlike prototypical GPCRs and {beta}-arrestin-biased atypical chemokine receptors, the Duffy antigen receptor also appears to lack {beta}-arrestin binding, making it an enigmatic 7TM chemokine receptor. In order to decipher the molecular mechanism of this intriguing functional divergence exhibited by the Duffy antigen receptor, we have determined its cryo-EM structure in complex with a C-C type chemokine, CCL7. The structure reveals a relatively superficial binding mode of CCL7, with the N-terminus of the receptor serving as the key interaction interface, and a partially formed orthosteric binding pocket lacking the second site for chemokine recognition compared to prototypical chemokine receptors. The structural framework allows us to employ HDX-MS approach to uncover ligand-induced structural changes in the receptor and draw important insights into the promiscuous nature of chemokine binding. Interestingly, we also observe a dramatic shortening of TM5 and 6 on the intracellular side, compared to prototypical GPCRs, which precludes the coupling of canonical signal-transducers namely G proteins, GRKs and {beta}-arrestins, as demonstrated through extensive cellular assays. Taken together, our study uncovers a previously unknown structural mechanism that imparts unique functional divergence on the 7TM fold encoded in the Duffy antigen receptor while maintaining its scavenging function and should facilitate the designing of novel therapeutics targeting this receptor.

biochemistry↗

bioRxiv2023

β-arrestin-dependent and -independent endosomal G protein activation by the vasopressin type 2 receptor

The vasopressin type 2 receptor (V2R) is an essential GPCR in renal regulation of water homeostasis. Upon stimulation, the V2R activates Gs and Gq/11, which is followed by robust recruitment of {beta}-arrestins and receptor internalization into endosomes. Unlike canonical GPCR signaling, the {beta}-arrestin association with the V2R does not terminate Gs activation, and thus, Gs-mediated signaling is sustained while the receptor is internalized. Here, we demonstrate that this V2R ability to co-interact with G protein/{beta}-arrestin and promote endosomal G protein signaling is not restricted to Gs, but also involves Gq/11. Furthermore, our data implies that {beta}-arrestins potentiate Gs/Gq/11 activation at endosomes rather than terminating their signaling. Surprisingly, we found that the V2R internalizes and promote endosomal G protein activation independent of {beta}-arrestins to a minor degree. These new observations challenge the current model of endosomal GPCR signaling and suggest that this event can occur in both {beta}-arrestin-dependent and -independent manners. IMPACT STATEMENTThe vasopressin type 2 receptor promotes dual Gs and Gq/11 signaling at early endosomes in {beta}-arrestin-dependent and -independent manners.

cell biology↗

bioRxiv2022

Endosomal Chemokine Receptor Signalosomes Regulate Central Mechanisms Underlying Cell Migration

Chemokine receptors are GPCRs that regulate chemotactic migration of a wide variety of cells including immune and cancer cells. Most chemokine receptors contain features associated with the ability to stimulate G protein signaling during {beta}-arrestin-mediated receptor internalization into endosomes. As endosomal signaling of certain non-GPCR receptors plays a major role in cell migration, we chose to investigate the potential role of endosomal chemokine receptor signaling on mechanisms governing this function. Applying a combination of pharmacological and cell biological approaches, we demonstrate that the model chemokine receptor CCR7 recruits G protein and {beta}-arrestin simultaneously upon chemokine stimulation, which enables internalized receptors to activate G protein from endosomes. Furthermore, spatiotemporal-resolved APEX2 proteome profiling shows that endosomal CCR7 uniquely enriches specific Rho GTPase regulators as compared to plasma membrane CCR7, which is directly associated with enhanced activity of the Rho GTPase Rac1 and chemotaxis of immune T cells. As Rac1 drives the formation of membrane protrusions during chemotaxis, our findings suggest an important integrated function of endosomal chemokine receptor signaling in cell migration.

cell biology↗

bioRxiv2021

Vasopressin V2 is a promiscuous G protein-coupled receptor that is biased by its peptide ligands

Activation of the G protein-coupled receptors by agonists may result in the activation of one or more G proteins, and in the recruitment of arrestins. The balance of activation of different pathways can be influenced by the ligand. Using BRET-based biosensors, we showed that the vasopressin V2 receptor activates or at least engages many different G proteins across all G protein subfamilies in response to its native agonist arginine vasopressin (AVP). This includes members of the Gi/o and G12/13 families that have not been previously reported. These signalling pathways are also activated by the synthetic peptide desmopressin and natural homologs of AVP, namely oxytocin and the non-mammalian hormone vasotocin. They demonstrated varying degrees of functional selectivity relative to AVP, as quantified using the operational model for quantifying ligand bias. Additionally, we modelled G protein activation as a Michaelis-Menten reaction. This approach provided a complementary way to quantify signalling bias, with an added benefit of clear separation of the effects of ligand affinity from the intrinsic activity of the receptor. These results showed that V2 receptor is not only promiscuous in its ability to engage several G proteins, but also that its signalling profile could be easily biased by small structural changes in the ligand.

pharmacology and toxicology↗