Search

The technique of cryogenic-electron microscopy (cryo-EM) has revolutionized the field of membrane protein structure and function with a focus on the dominantly observed molecular species. This report describes the structural characterization of a fully active human apelin receptor (APJR) complexed with heterotrimeric G protein observed in both 2:1 and 1:1 stoichiometric ratios. We use cryo-EM single-particle analysis to determine the structural details of both species from the same sample preparation. Protein preparations, in the presence of the endogenous peptide ligand ELA or a synthetic small molecule, both demonstrate these mixed stoichiometric states. Structural differences in G protein engagement between dimeric and monomeric APJR suggest a role for the stoichiometry of G protein-coupled receptor- (GPCR-)G protein coupling on downstream signaling and receptor pharmacology. Furthermore, a small, hydrophobic dimer interface provides a starting framework for additional class A GPCR dimerization studies. Together, these findings uncover a mechanism of versatile regulation through oligomerization by which GPCRs can modulate their signaling.

Apelin is an endogenous peptide that is involved in many diseases such as cardiovascular diseases, obesity, and cancer, which has made it an attractive target for drug discovery. Herein, we explore the penultimate and final sequence positions of [Pyr1]-apelin-13 (Ape13) via C-terminal N α-alkylated amide bonds and the introduction of positive charges, potentially targeting the allosteric sodium pocket, by assessing the binding affinity and signaling profiles at the apelin receptor (APJ). Synthetic analogues modified within this segment of Ape13 showed high affinity (K i 0.12-0.17 nM vs Ape13 K i 0.7 nM), potent Gαi1 activation (EC50 Gαi1 0.4-0.9 nM vs Ape13 EC50 1.1 nM), partial agonist behavior disfavoring β-arrestin 2 recruitment for positively charged ligands (e.g., 49 (SBL-AP-058), EC50 β-arr2 275 nM, E max 54%) and high plasma stability for N-alkyl ligands (t 1/2 > 7 h vs Ape13 t 1/2 0.5 h). Combining the benefits of the N α-alkylated amide bond with the guanidino substitution in a constrained ligand ledto 63 (SBL-AP-049), which displayed increased plasma stability (t 1/2 5.3 h) and strong reduction of β-arrestin 2 signaling with partial maximal efficacy (EC50 β-arr 864 nM, E max 48%), significantly reducing the hypotensive effect in vivo.

Side-chain-constrained amino acids are useful tools to modulate the biological properties of peptides. In this study, we applied side-chain constraints to apelin-13 (Ape13) by substituting the Pro12 and Phe13 positions, affecting the binding affinity and signaling profile on the apelin receptor (APJ). The residues 1Nal, Trp, and Aia were found to be beneficial substitutions for Pro12, and the resulting analogues displayed high affinity for APJ (Ki 0.08-0.18 nM vs Ape13 Ki 0.7 nM). Besides, constrained (d-Tic) or α,α-disubstituted residues (Dbzg; d-α-Me-Tyr(OBn)) were favorable for the Phe13 position. Compounds 47 (Pro12-Phe13 replaced by Aia-Phe, Ki 0.08 nM) and 53 (Pro12-Phe13 replaced by 1Nal-Dbzg, Ki 0.08 nM) are the most potent Ape13 analogues activating the Gα12 pathways (53, EC50 Gα12 2.8 nM vs Ape13, EC50 43 nM) known to date, displaying high affinity, resistance to ACE2 cleavage as well as improved pharmacokinetics in vitro (t1/2 5.8-7.3 h in rat plasma) and in vivo.

Cell migration is a ubiquitous process necessary to maintain and restore tissue functions. However, in cancer, cell migration leads to metastasis development and thus worsens the prognosis. Although the mechanism of cell migration is well understood, the identification of new targets modulating cell migration and deciphering their signaling events could lead to new therapies to restore tissue functions in diseases, such as inflammatory bowel disease, or to block metastatic development in different forms of cancer. Previous research has identified the G-protein-coupled P2Y6 receptor as an innovative target that could dictate cell migration under normal and pathological conditions. Surprisingly, there is little information on the cellular events triggered by activated P2Y6 during cell migration. Here, we demonstrated that P2Y6 activation stimulated A549 human lung cancer cells and Caco-2 colorectal cancer cell migration. Activated P2Y6 increased the number of filopodia and focal adhesions; two migratory structures required for cell migration. The generation of these structures involved Gαq /calcium/protein kinases C (PKC) and Gα13 /RHO-associated protein kinase-dependent pathways that dictate the formation of the migratory structures. These pathways led to the stabilization of the actin cytoskeleton through a PKC-dependent phosphorylation of cofilin. These results support the idea that the P2Y6 receptor represents a target of interest to modulate cell migration and revealed an intricate dialogue between two Gα-protein signaling pathways.

A comprehensive understanding of signalling downstream of GPCRs requires a broad approach to capture novel signalling modalities in addition to established pathways. Here, using an array of sixteen validated BRET-based biosensors, we analyzed the ability of seven different β-adrenergic ligands to engage five distinct signalling pathways downstream of the β1-adrenergic receptor (β1AR). In addition to generating signalling signatures and capturing functional selectivity for the different ligands toward these pathways, we also revealed coupling to signalling pathways that have not previously been ascribed to the βAR. These include coupling to Gz and G12 pathways. The signalling cascade linking the β1AR to calcium mobilization was also characterized using a combination of BRET-based biosensors and CRISPR-engineered HEK 293 cells lacking the Gαs subunit or with pharmacological or genetically engineered pathway inhibitors. We show that both Gs and G12 are required for the full calcium response. Our work highlights the power of combining signal profiling with genome editing approaches to capture the full complement of GPCR signalling activities in a given cell type and to probe their underlying mechanisms.

BackgroundPain is reported as the leading cause of disability in the common forms of inflammatory arthritis conditions. Acting as a key player in nociceptive processing, neuroinflammation, and neuron-glia communication, the chemokine CCL2/CCR2 axis holds great promise for controlling chronic painful arthritis. Here, we investigated how the CCL2/CCR2 system in the dorsal root ganglion (DRG) contributes to the peripheral inflammatory pain sensitization.MethodsRepeated intrathecal (i.t.) administration of the CCR2 antagonist, INCB3344 was tested for its ability to reverse the nociceptive-related behaviors in the tonic formalin and complete Freund’s adjuvant (CFA) inflammatory models. We further determined by qPCR the expression of CCL2/CCR2, SP and CGRP in DRG neurons from CFA-treated rats. Using DRG explants, acutely dissociated primary sensory neurons and calcium mobilization assay, we also assessed the release of CCL2 and sensitization of nociceptors. Finally, we examined by immunohistochemistry following nerve ligation the axonal transport of CCL2, SP, and CGRP from the sciatic nerve of CFA-treated rats.ResultsWe first found that CFA-induced paw edema provoked an increase in CCL2/CCR2 and SP expression in ipsilateral DRGs, which was decreased after INCB3344 treatment. This upregulation in pronociceptive neuromodulators was accompanied by an enhanced nociceptive neuron excitability on days 3 and 10 post-CFA, as revealed by the CCR2-dependent increase in intracellular calcium mobilization following CCL2 stimulation. In DRG explants, we further demonstrated that the release of CCL2 was increased following peripheral inflammation. Finally, the excitation of nociceptors following peripheral inflammation stimulated the anterograde transport of SP at their peripheral nerve terminals. Importantly, blockade of CCR2 reduced sensory neuron excitability by limiting the calcium mobilization and subsequently decreased peripheral transport of SP towards the periphery. Finally, pharmacological inhibition of CCR2 reversed the pronociceptive action of CCL2 in rats receiving formalin injection and significantly reduced the neurogenic inflammation as well as the stimuli-evoked and movement-evoked nociceptive behaviors in CFA-treated rats.ConclusionsOur results provide significant mechanistic insights into the role of CCL2/CCR2 within the DRG in the development of peripheral inflammation, nociceptor sensitization, and pain hypersensitivity. We further unveil the therapeutic potential of targeting CCR2 for the treatment of painful inflammatory disorders.

International audience; The current opioid crisis highlights the urgent need to develop safe and effective pain medications. Thus, neurotensin (NT) compounds represent a promising approach, as the antinociceptive effects of NT are mediated by activation of the two G protein-coupled receptor subtypes (i.e., NTS1 and NTS2) and produce potent opioid-independent analgesia. Here, we describe the synthesis and pharmacodynamic and pharmacokinetic properties of the first constrained NTS2 macrocyclic NT(8-13) analog. The Tyr11 residue of NT(8-13) was replaced with a Trp residue to achieve NTS2 selectivity, and a rationally designed side-chain to side-chain macrocyclization reaction was applied between Lys8 and Trp11 to constrain the peptide in an active binding conformation and limit its recognition by proteolytic enzymes. The resulting macrocyclic peptide, CR-01-64, exhibited high-affinity for NTS2 (Ki 7.0 nM), with a more than 125-fold selectivity over NTS1, as well as an improved plasma stability profile (t1/2 > 24 h) compared with NT (t1/2 ~ 2 min). Following intrathecal administration, CR-01-64 exerted dose-dependent and long-lasting analgesic effects in acute (ED50 = 4.6 µg/kg) and tonic (ED50 = 7.1 µg/kg) pain models as well as strong mechanical anti-allodynic effects in the CFA-induced chronic inflammatory pain model. Of particular importance, this constrained NTS2 analog exerted potent nonopioid antinociceptive effects and potentiated opioid-induced analgesia when combined with morphine. At high doses, CR-01-64 did not cause hypothermia or ileum relaxation, although it did induce mild and short-term hypotension, all of which are physiological effects associated with NTS1 activation. Overall, these results demonstrate the strong therapeutic potential of NTS2-selective analogs for the management of pain.

Neurotensin (NT) receptor type 2 (NTS2) represents an attractive target for the development of new NT-based analgesics. Here, we report the synthesis and functional in vivo characterization of the first constrained NTS2-selective macrocyclic NT analog. While most chemical optimization studies rely on the NT(8-13) fragment, we focused on NT(7-12) as a scaffold to design NTS2-selective macrocyclic peptides. Replacement of Ile12 by Leu, and Pro7/Pro10 by allylglycine residues followed by cyclization via ring-closing metathesis led to macrocycle 4, which exhibits good affinity for NTS2 (50 nM), high selectivity over NTS1 (>100 μM), and improved stability compared to NT(8-13). In vivo profiling in rats reveals that macrocycle 4 produces potent analgesia in three distinct rodent pain models, without causing the undesired effects associated with NTS1 activation. We further provide evidence of its non-opioid antinociceptive activity, therefore highlighting the strong therapeutic potential of NTS2-selective analogs for the management of acute and chronic pain.

Cysteinyl leukotriene G protein-coupled receptors, CysLT1R and CysLT2R, regulate bronchoconstrictive and pro-inflammatory effects and play a key role in allergic disorders, cardiovascular diseases, and cancer. CysLT1R antagonists have been widely used to treat asthma disorders, while CysLT2R is a potential target against uveal melanoma. However, very few selective antagonist chemotypes for CysLT receptors are available, and the design of such ligands has proved to be challenging. To overcome this obstacle, we took advantage of recently solved crystal structures of CysLT receptors and an ultra-large Enamine REAL library, representing a chemical space of 680 M readily available compounds. Virtual ligand screening employed 4D docking models comprising crystal structures of CysLT1R and CysLT2R and their corresponding ligand-optimized models. Functional assessment of the candidate hits yielded discovery of five novel antagonist chemotypes with sub-micromolar potencies and the best Ki = 220 nM at CysLT1R. One of the hits showed inverse agonism at the L129Q constitutively active mutant of CysLT2R, with potential utility against uveal melanoma.

Background: Pain is reported as the leading cause of disability in the common forms of inflammatory arthritis conditions. Acting as a key player in nociceptive processing, neuroinflammation and neuron-glia communication, the chemokine CCL2/CCR2 axis holds great promise for controlling chronic painful arthritis. Here, we investigated how the CCL2/CCR2 system in the dorsal root ganglion (DRG) contributes to the peripheral inflammatory pain sensitization.Methods: Repeated intrathecal (i.t.) administration of the CCR2 antagonist, INCB3344 was tested for its ability to reverse the nociceptive-related behaviors in the tonic formalin and complete Freund’s adjuvant (CFA) inflammatory models. We further determined by qPCR the expression of CCL2/CCR2, SP and CGRP in DRG neurons from CFA-treated rats. Using DRG explants, acutely dissociated primary sensory neurons and calcium mobilization assay, we also assessed the release of CCL2 and sensitization of nociceptors. Finally, we examined by immunohistochemistry following nerve ligation the axonal transport of CCL2, SP and CGRP from the sciatic nerve of CFA-treated rats.Results: We first found that CFA-induced paw oedema provoked an increase in CCL2/CCR2 and SP expression in ipsilateral DRGs, which was decreased after INCB3344 treatment. This upregulation in pronociceptive neuromodulators was accompanied by an enhanced nociceptive neuron excitability on days 3 and 10 post-CFA, as revealed by the CCR2-dependent increase in intracellular calcium mobilization following CCL2 stimulation. In DRG explants, we further demonstrated that the release of CCL2 was increased following peripheral inflammation. Finally, the excitation of nociceptors following peripheral inflammation stimulated the anterograde transport of SP at their peripheral nerve terminals. Importantly, blockade of CCR2 reduced sensory neuron excitability by limiting the calcium mobilization and subsequently decreased peripheral transport of SP towards the periphery. Finally, pharmacological inhibition of CCR2 reversed the pronociceptive action of CCL2 in rats receiving formalin injection and significantly reduced the neurogenic inflammation as well as the stimuli-evoked and movement-evoked nociceptive behaviors in CFA-treated rats.Conclusions: Our results provide significant mechanistic insights into the role of CCL2/CCR2 within the DRG in the development of peripheral inflammation, nociceptor sensitization and pain hypersensitivity. We further unveil the therapeutic potential of targeting CCR2 for the treatment of painful inflammatory disorders.

The endogenous tridecapeptide neurotensin (NT) has emerged as an important inhibitory modulator of pain transmission, exerting its analgesic action through the activation of the G protein-coupled receptors, NTS1 and NTS2. Whereas both NT receptors mediate the analgesic effects of NT, NTS1 activation also produces hypotension and hypothermia, which may represent obstacles for the development of new pain medications. In the present study, we implemented various chemical strategies to improve the metabolic stability of the biologically active fragment NT(8-13) and assessed their NTS1/NTS2 relative binding affinities. We then determined their ability to reduce the nociceptive behaviors in acute, tonic, and chronic pain models and to modulate blood pressure and body temperature. To this end, we synthesized a series of NT(8-13) analogs carrying a reduced amide bond at Lys8-Lys9 and harboring site-selective modifications with unnatural amino acids, such as silaproline (Sip) and trimethylsilylalanine (TMSAla). Incorporation of Sip and TMSAla respectively in positions 10 and 13 of NT(8-13) combined with the Lys8-Lys9 reduced amine bond (JMV5296) greatly prolonged the plasma half-life time over 20 hours. These modifications also led to a 25-fold peptide selectivity toward NTS2. More importantly, central delivery of JMV5296 was able to induce a strong antinociceptive effect in acute (tail-flick), tonic (formalin), and chronic inflammatory (CFA) pain models without inducing hypothermia. Altogether, these results demonstrate that the chemically-modified NT(8-13) analog JMV5296 exhibits a better therapeutic profile and may thus represent a promising avenue to guide the development of new stable NT agonists and improve pain management., This is the post-print (accepted) version of the following article: Vivancos M, et al. (2021), Behav Brain Res. doi: 10.1016/j.bbr.2021.113189, which has been accepted and published in final form at https://www.sciencedirect.com/science/article/pii/S0166432821000772

Therapeutic hypothermia represents a brain-protective strategy for multiple emergency situations, such as stroke or traumatic injury. Neurotensin (NT), which exerts its effects through activation of two G protein-coupled receptors, namely NTS1 and NTS2, induces a strong and long-lasting decrease in core body temperature after its central administration. Growing evidence demonstrates that NTS1 is the receptor subtype mediating the hypothermic action of NT. As such, potent NTS1 agonists designed on the basis of the minimal C-terminal NT(8-13) bioactive fragment have been shown to produce mild hypothermia and exert neuroprotective effects under various clinically relevant conditions. The high susceptibility of NT(8-13) to protease degradation (half-life 24 h; 16). Among them, the NT(8-13) analogs harboring the reduced amine bond combined with the unnatural amino acids TMSAla13 (4) and Sip10 (6) or the di-substitution Lys11 - TMSAla13 (12), D-Trp11-TMSAla13 (14), and Dmt11-Tle12 (16) produced sustained hypothermic effects (−3°C for at least 1 h). Importantly, we observed that hypothermia was mainly driven by the increased stability of the NT(8-13) derivatives, instead of the high binding-affinity at NTS1. Altogether, these results reveal the importance of the reduced amine bond in optimizing the metabolic properties of the NT(8-13) peptide and support the development of stable NTS1 agonists as first drug candidate in neuroprotective hypothermia.

Neurotensin (NT) is a tridecapeptide displaying interesting antinociceptive properties through its action on its receptors, NTS1 and NTS2. Neurotensin-like compounds have been shown to exert better antinociceptive properties than morphine at equimolar doses. In this article, we characterized the molecular effects of a novel neurotensin (8–13) (NT(8–13)) analog containing an unnatural amino acid. This compound, named JMV2009, displays a Silaproline in position 10 in replacement of a proline in the native NT(8–13). We first examined the binding affinities of this novel NT(8–13) derivative at both NTS1 and NTS2 receptor sites by performing competitive displacement of iodinated NT on purified cell membranes. Then, we evaluated the ability of JMV2009 to activate NTS1-related G proteins as well as to promote the recruitment of β-arrestins 1 and 2 by using BRET-based cellular assays in live cells. We next assessed its ability to induce p42/p44 MAPK phosphorylation and NT receptors internalization using western blot and cell-surface ELISA, respectively. Finally, we determined the in vitro plasma stability of this NT derivative. This article is associated with the original article “Pain relief devoid of opioid side effects following central action of a silylated neurotensin analog” published in European Journal of Pharmacology [1] . The reader is directed to the associated article for results interpretation, comments, and discussion.

Cell-based functional assays are an important part of compound screening and drug lead optimization, and they can also play a crucial role in the determination of the residues involved in ligand binding and signaling for a particular G-protein-coupled receptor. Conventional methods used for Gα(q/15)-coupled receptors rely on the use of fluorescent probes for Ca(++) sensing (such as Fura-2 and Fluo-4) or on the incorporation of [(3)H]-inositol into inositol 1,4,5- triphosphate (IP3). However, these methods are not suitable for screening large libraries of compounds or for screening several mutants of the same receptor. In contrast, the IP-One assay by Cisbio is a TR-FRET assay suitable for large compound library screening when using stable cell lines that express a specific 7TMR. However, when using transiently transfected mutants of a 7TMR, this assay is not ideal, as it requires a two-step protocol of cell culture. Therefore, we have optimized the IP-One assay protocol using the reverse transfection method in 384-well plates. This offers a time- and resource-efficient alternative to the two-step protocol previously used for the screening of several mutants of Gα(q/15)-coupled 7TMRs.

Pepducins are cell-penetrating, membrane-tethered lipopeptides designed to target the intracellular region of a G protein-coupled receptor (GPCR) in order to allosterically modulate the receptor's signaling output. In this proof-of-concept study, we explored the pain-relief potential of a pepducin series derived from the first intracellular loop of neurotensin receptor type 1 (NTS1), a class A GPCR that mediates many of the effects of the neurotensin (NT) tridecapeptide, including hypothermia, hypotension and analgesia. We used BRET-based biosensors to determine the pepducins' ability to engage G protein signaling pathways associated with NTS1 activation. We observed partial Gq and G13 activation at a 10 {\mu}M concentration, indicating that these pepducins may act as allosteric agonists of NTS1. Additionally, we used surface plasmon resonance (SPR) as a label-free assay to monitor pepducin-induced responses in CHO-K1 cells stably expressing hNTS1. This whole-cell integrated assay enabled us to subdivide our pepducin series into three profile response groups. In order to determine the pepducins' antinociceptive potential, we then screened the series in an acute pain model (tail-flick test) by measuring tail withdrawal latencies to a thermal nociceptive stimulus, following intrathecal pepducin administration (275 nmol/kg). We further evaluated promising pepducins in a tonic pain model (formalin test), as well as in neuropathic (Chronic Constriction Injury) and inflammatory (Complete Freund's Adjuvant) chronic pain models. We report one pepducin, PP-001, that consistently reduced rat nociceptive behaviors, even in chronic pain paradigm. Altogether, these results suggest that NTS1-derived pepducins may represent a promising strategy in pain-relief., Comment: This is the accepted version of the following article: Brouillette RL, et al. (2020), Pharmacological Research. doi:10.1016/j.phrs.2020.104750 , which has been accepted and published in final form at https://doi.org/10.1016/j.phrs.2020.104750

The neurotensin receptors are attractive targets for the development of new analgesic compounds. They represent potential alternatives or adjuvants to opioids. Herein, we report the structural optimization of our recently reported macrocyclic peptide analogues of NT(8-13). The macrocycle was formed via ring-closing metathesis (RCM) between an ortho allylated tyrosine residue in position 11 and the side chain of alkene-functionalized amino acid in position 8 of NT(8-13). Minute modifications led to significant binding affinity improvement ( Ki improved from 5600 to 15 nM) with greatly improved plasma stability compared to NT(8-13). This study also delineates the structural features influencing these parameters. The signaling profiles of the new macrocycles were determined on the NTS1 receptor, and the physiological effects of the two most potent and stable analogues were assessed in vivo using rodent models. Both compounds displayed strong analgesic effects.

The apelin receptor generates increasing interest as a potential target across several cardiovascular indications. However, the short half-life of its cognate ligands, the apelin peptides, is a limiting factor for pharmacological use. In this study, we systematically explored each position of apelin-13 to find the best position to cyclize the peptide, with the goal to improve its stability while optimizing its binding affinity and signaling profile. Macrocyclic analogues showed a remarkably higher stability in rat plasma (half-life >3 h versus 24 min for Pyr-apelin-13), accompanied by improved affinity (analogue 15, Ki 0.15 nM and t1/2 6.8 h). Several compounds displayed higher inotropic effects ex vivo in the Langendorff isolated heart model in rats (analogues 13 and 15, maximum response at 0.003 nM versus 0.03 nM of apelin-13). In conclusion, this study provides stable and active compounds to better characterize the pharmacology of the apelinergic system.

The human neurotensin 1 receptor (hNTS1) is a G protein-coupled receptor involved in many physiological functions, including analgesia, hypothermia, and hypotension. To gain a better understanding of which signaling pathways or combination of pathways are linked to NTS1 activation and function, we investigated the ability of activated hNTS1, which was stably expressed by CHO-K1 cells, to directly engage G proteins, activate second messenger cascades and recruit \b{eta}-arrestins. Using BRET-based biosensors, we found that neurotensin (NT), NT(8-13) and neuromedin N (NN) activated the G{\alpha}q-, G{\alpha}i1-, G{\alpha}oA-, and G{\alpha}13-protein signaling pathways as well as the recruitment of \b{eta}-arrestins 1 and 2. Using pharmacological inhibitors, we further demonstrated that all three ligands stimulated the production of inositol phosphate and modulation of cAMP accumulation along with ERK1/2 activation. Interestingly, despite the functional coupling to G{\alpha}i1 and G{\alpha}oA, NT was found to produce higher levels of cAMP in the presence of pertussis toxin, supporting that hNTS1 activation leads to cAMP accumulation in a G{\alpha}s-dependent manner. Additionally, we demonstrated that the full activation of ERK1/2 required signaling through both a PTX-sensitive Gi/o-c-Src signaling pathway and PLCb-DAG-PKC-Raf-1- dependent pathway downstream of Gq. Finally, the whole-cell integrated signatures monitored by the cell-based surface plasmon resonance and changes in the electrical impedance of a confluent cell monolayer led to identical phenotypic responses between the three ligands. The characterization of the hNTS1-mediated cellular signaling network will be helpful to accelerate the validation of potential NTS1 biased ligands with an improved therapeutic/adverse effect profile., Comment: This is the accepted (postprint) version of the following article: Besserer-Offroy \'E, et al. (2017). Eur J Pharmacol. doi: 10.1016/j.ejphar.2017.03.046, which has been accepted and published in its final form at http://www.sciencedirect.com/science/article/pii/S0014299917302157 V1: Preprint version V2: Accepted version (postprint)

Cell migration is a ubiquitous process necessary to maintain and restore tissue functions. However, in cancer, cell migration leads to metastasis development and thus worsens the prognosis. Although the mechanism of cell migration is well understood, the identification of new targets modulating cell migration and deciphering their signaling events could lead to new therapies to restore tissue functions in diseases, such as inflammatory bowel disease, or to block metastatic development in different forms of cancer. Previous research has identified the G-protein-coupled P2Y

Cell-based functional assays are an important part of compound screening and drug lead optimization, and they can also play a crucial role in the determination of the residues involved in ligand binding and signaling for a particular G-protein-coupled receptor. Conventional methods used for Gαq/15-coupled receptors rely on the use of fluorescent probes for Ca++ sensing (such as Fura-2 and Fluo-4) or on the incorporation of [3H]-inositol into inositol 1,4,5- triphosphate (IP3). However, these methods are not suitable for screening large libraries of compounds or for screening several mutants of the same receptor. In contrast, the IP-One assay by Cisbio is a TR-FRET assay suitable for large compound library screening when using stable cell lines that express a specific 7TMR. However, when using transiently transfected mutants of a 7TMR, this assay is not ideal, as it requires a two-step protocol of cell culture. Therefore, we have optimized the IP-One assay protocol using the reverse transfection method in 384-well plates. This offers a time- and resource-efficient alternative to the two-step protocol previously used for the screening of several mutants of Gαq/15-coupled 7TMRs.

Neurotensin (NT) exerts naloxone-insensitive antinociceptive action through its binding to both NTS1 and NTS2 receptors and NT analogs provide stronger pain relief than morphine on a molecular basis. Here, we examined the analgesic/adverse effect profile of a new NT(8-13) derivative denoted JMV2009, in which the Pro10 residue was substituted by a silicon-containing unnatural amino acid silaproline. We first report the synthesis and in vitro characterization (receptor-binding affinity, functional activity and stability) of JMV2009. We next examined its analgesic activity in a battery of acute, tonic and chronic pain models. We finally evaluated its ability to induce adverse effects associated with chronic opioid use, such as constipation and analgesic tolerance or related to NTS1 activation, like hypothermia. In in vitro assays, JMV2009 exhibited high binding affinity for both NTS1 and NTS2, improved proteolytic resistance as well as agonistic activities similar to NT, inducing sustained activation of p42/p44 MAPK and receptor internalization. Intrathecal injection of JMV2009 produced dose-dependent antinociceptive responses in the tail-flick test and almost completely abolished the nociceptive-related behaviors induced by chemical somatic and visceral noxious stimuli. Likewise, increasing doses of JMV2009 significantly reduced tactile allodynia and weight bearing deficits in nerve-injured rats. Importantly, chronic agonist treatment did not result in the development of analgesic tolerance. Furthermore, JMV2009 did not cause constipation and was ineffective in inducing hypothermia. These findings suggest that NT drugs can act as an effective opioid-free medication for the management of pain or can serve as adjuvant analgesics to reduce the opioid adverse effects., Comment: This is the post-print (accepted) version of the following article: T\'etreault P, et al. (2020), Eur J Pharmacol. doi: 10.1016/j.ejphar.2020.173174, which has been accepted and published in final form at https://doi.org/10.1016/j.ejphar.2020.173174

Cysteinyl leukotriene G protein-coupled receptors CysLT1 and CysLT2 regulate pro-inflammatory responses associated with allergic disorders. While selective inhibition of CysLT1R has been used for treating asthma and associated diseases for over two decades, CysLT2R has recently started to emerge as a potential drug target against atopic asthma, brain injury and central nervous system disorders, as well as several types of cancer. Here, we describe four crystal structures of CysLT2R in complex with three dual CysLT1R/CysLT2R antagonists. The reported structures together with the results of comprehensive mutagenesis and computer modeling studies shed light on molecular determinants of CysLTR ligand selectivity and specific effects of disease-related single nucleotide variants., Cysteinyl leukotriene G protein-coupled receptors CysLT1 and CysLT2 regulate pro-inflammatory responses associated with allergic disorders. Here, authors describe four crystal structures of CysLT2R in complex with three dual CysLT1R/CysLT2R antagonists, which shed light on CysLTR ligand selectivity.

Improvements in the survival of breast cancer patients have led to the emergence of bone health and pain management as key aspects of patient’s quality of life. Here, we used a female rat MRMT-1 model of breast cancer-induced bone pain to compare the effects of three drugs used clinically morphine, nabilone and zoledronate on tumor progression, bone remodeling and pain relief. We found that chronic morphine reduced the mechanical hypersensitivity induced by the proliferation of the luminal B aggressive breast cancer cells in the tumor-bearing femur and prevented spinal neuronal and astrocyte activation. Using MTT cell viability assay and MRI coupled to 18FDG PET imaging followed by ex vivo 3D µCT, we further demonstrated that morphine did not directly exert tumor growth promoting or inhibiting effects on MRMT-1 cancer cells but induced detrimental effects on bone healing by disturbing the balance between bone formation and breakdown. In sharp contrast, both the FDA-approved bisphosphonate zoledronate and the synthetic cannabinoid nabilone prescribed as antiemetics to patients receiving chemotherapy were effective in limiting the osteolytic bone destruction, thus preserving the bone architecture. The protective effect of nabilone on bone metabolism was further accompanied by a direct inhibition of tumor growth. As opposed to zoledronate, nabilone was however not able to manage bone tumor-induced pain and reactive gliosis. Altogether, our results revealed that morphine, nabilone and zoledronate exert disparate effects on tumor growth, bone metabolism and pain control. These findings also support the use of nabilone as an adjuvant therapy for bone metastases.

Neurotensin (NT) exerts its analgesic effects through activation of the G protein-coupled receptors NTS1 and NTS2. This opioid-independent antinociception represents a potential alternative for pain management. While activation of NTS1 also induces a drop in blood pressure and body temperature, NTS2 appears to be an analgesic target free of these adverse effects. Here, we report modifications of NT at Tyr11 to increase selectivity toward NTS2, complemented by modifications at the N-terminus to impair proteolytic degradation of the biologically active NT(8-13) sequence. Replacement of Tyr11 by either 6-OH-Tic or 7-OH-Tic resulted in a significant loss of binding affinity to NTS1 and subsequent NTS2 selectivity. Incorporation of the unnatural amino acid β3hLys at position 8 increased the half-life to over 24 h in plasma. Simultaneous integration of both β3hLys8 and 6-OH-Tic11 into NT(8-13) produced a potent and NTS2-selective analogue with strong analgesic action after intrathecal delivery in the rat formalin-induced pain model with an ED50 of 1.4 nmol. Additionally, intravenous administration of this NT analogue did not produce persistent hypotension or hypothermia. These results demonstrate that NT analogues harboring unnatural amino acids at positions 8 and 11 can enhance crucial pharmacokinetic and pharmacodynamic features for NT(8-13) analogues, i.e., proteolytic stability, NTS2 selectivity, and improved analgesic/adverse effect ratio.

A comprehensive understanding of signalling downstream of GPCRs requires a broad approach to capture novel signalling modalities in addition to established pathways. Here, using an array of sixteen validated BRET-based biosensors, we analyzed the ability of seven different β-adrenergic ligands to engage five distinct signalling pathways downstream of the β1-adrenergic receptor (β1AR). In addition to generating signalling signatures and capturing functional selectivity for the different ligands toward these pathways, we also revealed coupling to signalling pathways that have not previously been ascribed to the βAR. These include coupling to Gz and G12 pathways. The signalling cascade linking the β1AR to calcium mobilization was also characterized using a combination of BRET-based biosensors and CRISPR-engineered HEK 293 cells lacking the Gαs subunit or with pharmacological or genetically engineered pathway inhibitors. We show that both Gs and G12 are required for the full calcium response. Our work highlights the power of combining signal profiling with genome editing approaches to capture the full complement of GPCR signalling activities in a given cell type and to probe their underlying mechanisms.

Quantifying cell surface expression of G Protein-Coupled Receptors (GPCRs) can be exteremly important for the expression of mutant receptors. Herein we report a useful Enzyme-Linked Immunosorbent Assay (ELISA) for the cell-surface detection of a HA-tagged version of a GPCR.

Clinical evidences suggest that an imbalance between descending inhibition and facilitation drives the development of chronic pain. However, potential mechanisms promoting the establishment of a persistent pain state and the increased pain vulnerability remain unknown. This preclinical study was designed to evaluate temporal changes in descending pain modulation at specific experimental endpoints (12, 28, 90 and 168 days) using a novel double-hit model of chronic/tonic pain (first hit: chronic constriction injury (CCI) model; second hit: tonic formalin pain in the contralateral hindpaw). Basal activity of bulbo-spinal monoaminergic systems was further assessed through liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) screening of cerebrospinal fluid (CSF). We found that CCI-operated rats exhibited a reduced nociceptive response profile, peaking on day 28, when subjected to tonic pain. This behavioral response was accompanied by a rapid increase in basal CSF serotonin and norepinephrine levels 12 days after neuropathy, followed by a return to sham levels on day 28. These molecular and behavioral adaptive changes in descending pain inhibition seemed to slowly fade over time. We therefore suggest that chronic neuropathic pain produces a transient hyperactivation of bulbo-spinal monoaminergic drive when previously primed using a tonic pain paradigm (i.e., formalin test), translating into inhibition of subsequent nociceptive behaviors. Altogether, we propose that early hyperactivation of descending pain inhibitory mechanisms, and its potential ensuing exhaustion, could be part of the temporal neurophysiological chain of events favoring chronic neuropathic pain establishment.

Long-term cognitive deficits are observed after treatment of brain tumors or metastases by radiotherapy. Treatment optimization thus requires a better understanding of the effects of radiotherapy on specific brain regions, according to their sensitivity and interconnectivity. In the present study, behavioral tests supported by immunohistology and magnetic resonance imaging provided a consistent picture of the persistent neurocognitive decline and neuroinflammation after the onset of irradiation-induced necrosis in the right primary somatosensory cortex of Fischer rats. Necrosis surrounded by neovascularization was first detected 54 days after irradiation and then spread to 110 days in the primary motor cortex, primary somatosensory region, striatum and right ventricle, resulting in fiber bundle disruption and demyelination in the corpus callosum of the right hemisphere. These structural damages translated into selective behavioral changes including spatial memory loss, disinhibition of anxiety-like behaviors, hyperactivity and pain hypersensitivity, but no significant alteration in motor coordination and grip strength abilities. Concomitantly, activated microglia and reactive astrocytes, accompanied by infiltration of leukocytes (CD45+) and T-cells (CD3+) cooperated to shape the neuroinflammation response. Overall, our study suggests that the slow and gradual onset of cellular damage would allow adaptation in brain regions that are susceptible to neuronal plasticity; while other cerebral structures that do not have this capacity would be more affected. The planning of radiotherapy, adjusted to the sensitivity and adaptability of brain structures, could therefore preserve certain neurocognitive functions; while higher doses of radiation could be delivered to brain areas that can better adapt to this treatment. In addition, strategies to block early post-radiation events need to be explored to prevent the development of long-term cognitive dysfunction.

Two distinct antagonist-bound structures of CysLT1R reveal unique ligand-binding modes and signaling mechanisms., The G protein–coupled cysteinyl leukotriene receptor CysLT1R mediates inflammatory processes and plays a major role in numerous disorders, including asthma, allergic rhinitis, cardiovascular disease, and cancer. Selective CysLT1R antagonists are widely prescribed as antiasthmatic drugs; however, these drugs demonstrate low effectiveness in some patients and exhibit a variety of side effects. To gain deeper understanding into the functional mechanisms of CysLTRs, we determined the crystal structures of CysLT1R bound to two chemically distinct antagonists, zafirlukast and pranlukast. The structures reveal unique ligand-binding modes and signaling mechanisms, including lateral ligand access to the orthosteric pocket between transmembrane helices TM4 and TM5, an atypical pattern of microswitches, and a distinct four-residue–coordinated sodium site. These results provide important insights and structural templates for rational discovery of safer and more effective drugs.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

G protein-coupled receptors (GPCRs) are important therapeutic targets that exhibit functional selectivity (biased signaling), in which different ligands or receptor variants elicit distinct downstream signaling. Understanding all the signaling events and biases that contribute to both the beneficial and adverse effects of GPCR stimulation by given ligands is important for drug discovery. Here, we report the design, validation, and use of pathway-selective bioluminescence resonance energy transfer (BRET) biosensors that monitor the engagement and activation of signaling effectors downstream of G proteins, including protein kinase C (PKC), phospholipase C (PLC), p63RhoGEF, and Rho. Combined with G protein and β-arrestin BRET biosensors, our sensors enabled real-time monitoring of GPCR signaling at different levels in downstream pathways in both native and engineered cells. Profiling of the responses to 14 angiotensin II (AngII) type 1 receptor (AT1R) ligands enabled the clustering of compounds into different subfamilies of biased ligands and showed that, in addition to the previously reported functional selectivity between Gαq and β-arrestin, there are also biases among G protein subtypes. We also demonstrated that biases observed at the receptor and G protein levels propagated to downstream signaling pathways and that these biases could occur through the engagement of different G proteins to activate a common effector. We also used these tools to determine how naturally occurring AT1R variants affected signaling bias. This suite of BRET biosensors provides a useful resource for fingerprinting biased ligands and mutant receptors and for dissecting functional selectivity at various levels of GPCR signaling.

Opioid and neurotensin (NT) receptors are expressed in both central and peripheral nervous systems where they modulate nociceptive responses. Nowadays, opioid analgesics like morphine remain the most prescribed drugs for the treatment of moderate to severe pain. However, despite their daily used, opioids can produce life-threatening side effects, such as constipation or respiratory depression. Besides, NT analogs exert strong opioid-independent analgesia. Here, we thus hypothesized that the combined use of opioid and NT agonists would require lower doses to produce significant analgesic effects, hence decreasing opioid-induced adverse effects. We used isobologram analyses to determine if the combination of a NT brain-penetrant analog, An2-NT(8-13) with morphine results in an inhibitory, synergistic or additive analgesic response. We found that intravenous administration of An2-NT(8-13) reduced by 90% the nocifensive behaviors induced by formalin injection, at the dose of 0.018 mg/kg. Likewise, subcutaneous morphine reduced pain by 90% at 1.8 mg/kg. Importantly, isobologram analyses revealed that the co-injection of An2-NT(8-13) with morphine induced an additive analgesic response. We finally assessed the effects of morphine and An2-NT(8-13) on the gastrointestinal tract motility using the charcoal meal test. As opposed to morphine which significantly reduced the intestinal motility at the analgesic effective dose of 1.8 mg/kg, An2-NT(8-13) did not affect the charcoal meal intestinal transit at 0.018 mg/kg. Interestingly, at the dose providing 90% pain relief, the co-administration of morphine with An2-NT(8-13) had a reduced effect on constipation. Altogether, these results suggest that combining NT agonists with morphine may improve its analgesic/adverse effect ratio.

In this study, affinities and activities of derivatized analogues of Dmt-dermorphin[1–4] (i.e. Dmt- d -Ala-Phe-GlyNH2, Dmt = 2′,6′-dimethyl-(S)-tyrosine) for the µ opioid receptor (MOP) and δ opioid receptor (DOP) were evaluated using radioligand binding studies, functional cell-based assays and isolated organ bath experiments. By means of solid-phase or solution-phase Suzuki-Miyaura cross-couplings, various substituted regioisomers of the phenylalanine moiety in position 3 of the sequence were prepared. An 18-membered library of opioid tetrapeptides was generated via screening of the chemical space around the Phe3 side chain. These substitutions modulated bioactivity, receptor subtype selectivity and highly effective ligands with subnanomolar binding affinities, contributed to higher functional activities and potent analgesic actions. In search of selective peptidic ligands, we show here that the Suzuki-Miyaura reaction is a versatile and robust tool which could also be deployed elsewhere.

ELABELA (ELA) was recently discovered as a novel endogenous ligand of the apelin receptor (APJ), a G protein-coupled receptor. ELA signaling was demonstrated to be crucial for normal heart and vasculature development during embryogenesis. We delineate here ELA's structure- activity relationships and report the identification of analogue 3 (ELA(19-32)), a fragment of ELA that binds to APJ, activates the G alpha(i1) and beta-arrestin-2 signaling pathways, and induces receptor internalization similarly to its parent endogenous peptide. An alanine scan performed on 3 revealed that the C-terminal residues are critical for binding to APJ and signaling. Finally, using isolated-perfused hearts and in vivo hemodynamic and echocardiographic measurements, we demonstrate that ELA and 3 both reduce arterial pressure and exert positive inotropic effects on the heart. Altogether, these results present ELA and 3 as potential therapeutic options in managing cardiovascular diseases

Compounds acting via the GPCR neurotensin receptor type 2 (NTS2) display analgesia in relevant preclinical models. The amide bond in nonpeptide NTS1 antagonists plays a central role in receptor recognition and molecular conformation. Using NTS2 FLIPR and binding assays, we found that it is also a key molecular structure for binding and calcium mobilization at NTS2. We found that reversed amides display a shift from agonist to antagonist activity and provided examples of the first competitive nonpeptide antagonists observed in the NTS2 FLIPR assay. These compounds will be valuable tools for determining the role of calcium signaling in vitro to NTS2 mediated analgesia.

Apelin is the endogenous ligand of the APJ receptor, a member of the G protein-coupled receptor family. This system plays an important role in the regulation of blood pressure and cardiovascular functions. To better understand the role of its C-terminal Phe(13) residue on ligand binding, receptor signaling, and hypotension, we report a series of modified analogues in which Phe(13) was substituted by unnatural amino acids. These modifications delivered new compounds exhibiting higher affinity and potency to inhibit cAMP accumulation compared to apelin-13. In particular, analogues Bpa(13) or (α-Me)Phe(13) were 30-fold more potent to inhibit cAMP accumulation than apelin-13. Tyr(OBn)(13) substitution led to a 60-fold improvement in binding affinity and induced stronger and more sustained drop in blood pressure compared to apelin-13. Our study identified new potent analogues of apelin-13, which represent valuable probes to better understand its structure-function relationship.

The epidemic of type 2 diabetes mellitus (T2DM) is fueled by added fructose consumption. Here, we thus combined high-fat/high-fructose diet, with multiple low-dose injections of streptozotocin (HF/HF/Stz) to emulate the long-term complications of T2DM. HF/HF/Stz rats, monitored over 56 weeks, exhibited metabolic dysfunctions associated with the different stages of the T2DM disease progression in humans: an early prediabetic phase characterized by an hyperinsulinemic period with modest dysglycemia, followed by a late stage of T2DM with frank hyperglycemia, normalization of insulinemia, marked dyslipidemia, hepatic fibrosis and pancreatic β-cell failure. Histopathological analyses combined to [18F]-FDG PET imaging further demonstrated the presence of several end-organ long-term complications, including reduction in myocardial glucose utilization, renal dysfunction as well as microvascular neuropathy and retinopathy. We also provide for the first time a comprehensive µ-PET whole brain imaging of the changes in glucose metabolic activity within discrete cerebral regions in HF/HF/Stz diabetic rats. Altogether, we developed and characterized a unique non-genetic preclinical model of T2DM adapted to the current diet and lifestyle that recapitulates the major metabolic features of the disease progression, from insulin resistance to pancreatic β-cell dysfunction, and closely mimicking the target-organ damage occurring in type 2 diabetic patients at advanced stages.

Compounds acting via the GPCR neurotensin receptor type 2 (NTS2) display analgesic effects in relevant animal models. Using a pharmacophore model based on known NT receptor nonpeptide compounds, we screened commercial databases to identify compounds that might possess activity at NTS2 receptor sites. Modification of our screening hit to include structural features known to be recognized by NTS1 and NTS2, led to the identification of the novel NTS2 selective nonpeptide, N-{[6-chloro-4-(2,6-dimethoxyphenyl)quinazolin-2-yl]carbonyl}-l-leucine (9). This compound is a potent partial agonist in the FLIPR assay with a profile of activity similar to that of the reference NTS2 analgesic nonpeptide levocabastine (5).

[Image: see text] Neurotensin exerts potent analgesic effects following activation of its cognate GPCRs. In this study, we describe a systematic exploration, using structure-based design, of conformationally constraining neurotensin (8–13) with the help of macrocyclization and the resulting impacts on binding affinity, signaling, and proteolytic stability. This exploratory study led to a macrocyclic scaffold with submicromolar binding affinity, agonist activity, and greatly improved plasma stability.