- Central administration of TRV027 improves baroreflex sensitivity and vascular reactivity in spontaneously hypertensive rats. [Journal Article]
- CSClin Sci (Lond) 2018 Jun 14
- TRV027 is a biased agonist for the Angiotensin (Ang)-II type 1 receptor (AT1R), able to recruit β-arrestin 2 independently of G-proteins activation. β-arrestin activation in the central nervous syste...
TRV027 is a biased agonist for the Angiotensin (Ang)-II type 1 receptor (AT1R), able to recruit β-arrestin 2 independently of G-proteins activation. β-arrestin activation in the central nervous system (CNS) was suggested to oppose the effects of Ang-II. This study evaluates the effect of central infusion of TRV027 on arterial pressure (AP), autonomic function, baroreflex sensitivity and peripheral vascular reactivity. Spontaneously hypertensive (SH) and Wistar Kyoto (WKY) rats were treated with TRV027 for 14 days (20 ng/hour) delivered to the lateral ventricle via osmotic minipumps. Mechanistic studies were performed in HEK293T cells co-transfected with AT1R and angiotensin converting enzyme type 2 (ACE2) treated with TRV027 (100 nM) or Ang-II (100 nM). TRV027 infusion in SHR reduced AP (~20 mmHg, p <0.05), sympathetic vasomotor activity (ΔMAP = -47.2 ±2.8 vs. -64 ±5.1 mmHg, p < 0.05) and low-frequency (LF) oscillations of AP (1.7 ±0.2 vs. 5.8 ±0.4 mmHg2, p <0.05) compared to the SHR control group. TRV027 also increased vagal tone, improved baroreflex sensitivity, reduced the reactivity of mesenteric arteries to Ang-II and increased vascular sensitivity to phenylephrine, acetylcholine and sodium nitroprusside. In vitro , TRV027 prevented the Ang-II-induced up-regulation of ADAM17 and in contrast to Ang-II, had no effects on ACE2 activity and expression levels. Furthermore, TRV027 induced lesser interactions between AT1R and ACE2 compared to Ang-II. Together, these data suggest that due to its biased activity for the β-arrestin pathway, TRV027 has beneficial effects within the CNS on hypertension, autonomic and vascular function, possibly through preserving ACE2 compensatory activity in neurons.
- Structure-activity relationships of imidazothiazinones and analogs as antagonists of the cannabinoid-activated orphan G protein-coupled receptor GPR18. [Journal Article]
- EJEur J Med Chem 2018 Jun 01; 155:381-397
- GPR18 is a cannabinoid-activated orphan G protein-coupled receptor (GPCR) that is selectively expressed on immune cells. Despite its significant potential as a drug target for inflammatory diseases a...
GPR18 is a cannabinoid-activated orphan G protein-coupled receptor (GPCR) that is selectively expressed on immune cells. Despite its significant potential as a drug target for inflammatory diseases and cancer immunotherapy, only very few GPR18 ligands have been described to date. In the present study we investigated the structure-activity relationships (SARs) of (Z)-2-(3-(4-chlorobenzyloxy)benzylidene)-6,7-dihydro-2H-imidazo[2,1-b][1,3]thiazin-3(5H)-one (PSB-CB5, 5), the most potent GPR18 antagonist described to date. Analogs were synthesized that exhibit broad modifications of the heterocyclic core and/or variation of substituents at the benzylidene moiety. The compounds were investigated in β-arrestin recruitment assays as inhibitors of human GPR18 activation by tetrahydrocannabinol (THC). Selectivity was assessed versus the cannabinoid receptors (CB1 and CB2) and versus GPR55, another orphan GPCR that interacts with cannabinoids. Phenyloxyalkyloxy-substituted benzylidenethiazinones with long alkyl chains (optimal length: hexamethylene) efficiently blocked GPR18 with similarly high potency as lead structure 5. (Z)-2-(3-(6-(4-Chlorophenoxy)hexyloxy)benzylidene)-6,7-dihydro-2H-imidazo[2,1-b][1,3]thiazin-3(5H)-one (PSB-CB-27, 23) exhibited the best profile: it displayed an IC50 value of 650 nM at GPR18 and showed improved selectivity versus CB receptors as compared to lead structure 5. Importantly, in contrast to 5, which showed only partial inhibition (60%), 23 led to a complete blockade of THC-induced GPR18 activation and is thus a superior tool for target validation. In addition, several compounds, e.g. 18 and 22, were identified as dual GPR18/GPR55 antagonists with similar potency at both targets, and selectivity versus CB receptors.
- Cryo-EM structure of human rhodopsin bound to an inhibitory G protein. [Journal Article]
- NatNature 2018 Jun 13
- G-protein-coupled receptors comprise the largest family of mammalian transmembrane receptors. They mediate numerous cellular pathways by coupling with downstream signalling transducers, including the...
G-protein-coupled receptors comprise the largest family of mammalian transmembrane receptors. They mediate numerous cellular pathways by coupling with downstream signalling transducers, including the hetrotrimeric G proteins Gs (stimulatory) and Gi (inhibitory) and several arrestin proteins. The structural mechanisms that define how G-protein-coupled receptors selectively couple to a specific type of G protein or arrestin remain unknown. Here, using cryo-electron microscopy, we show that the major interactions between activated rhodopsin and Gi are mediated by the C-terminal helix of the Gi α-subunit, which is wedged into the cytoplasmic cavity of the transmembrane helix bundle and directly contacts the amino terminus of helix 8 of rhodopsin. Structural comparisons of inactive, Gi-bound and arrestin-bound forms of rhodopsin with inactive and Gs-bound forms of the β2-adrenergic receptor provide a foundation to understand the unique structural signatures that are associated with the recognition of Gs, Gi and arrestin by activated G-protein-coupled receptors.
- Ligand-selective small molecule modulators of the constitutively active vGPCR US28. [Journal Article]
- EJEur J Med Chem 2018 May 31; 155:244-254
- US28 is a broad-spectrum constitutively active G protein-coupled receptor encoded by the human cytomegalovirus (HCMV). It binds and scavenges multiple CC-chemokines as well as CX3CL1 (fractalkine) by...
US28 is a broad-spectrum constitutively active G protein-coupled receptor encoded by the human cytomegalovirus (HCMV). It binds and scavenges multiple CC-chemokines as well as CX3CL1 (fractalkine) by constitutive receptor endocytosis to escape immune surveillance. We herein report the design and characterization of a novel library of US28-acting commercially available ligands based on the molecular descriptors of two previously reported US28-acting structures. Among these, we identify compounds capable of selectively recognizing CCL2-and CCL4-, but not CX3CL1-induced receptor conformations. Moreover, we find a direct correlation between the binding properties of small molecule ligands to CCL-induced conformations at the wild-type receptor and functional activity at the C-terminal truncated US28Δ300. As US28Δ300 is devoid of arrestin-recruitment and endocytosis, this highlights the potential usefulness of this construct in future drug discovery efforts aimed at specific US28 conformations. The new scaffolds identified herein represent valuable starting points for the generation of novel anti-HCMV therapies targeting the virus-encoded chemokine receptor US28 in a conformational-selective manner.
- Evidence for the Existence of a CXCL17 Receptor Distinct from GPR35. [Journal Article]
- JIJ Immunol 2018 Jun 06
- The chemokine CXCL17 is associated with the innate response in mucosal tissues but is poorly characterized. Similarly, the G protein-coupled receptor GPR35, expressed by monocytes and mast cells, has...
The chemokine CXCL17 is associated with the innate response in mucosal tissues but is poorly characterized. Similarly, the G protein-coupled receptor GPR35, expressed by monocytes and mast cells, has been implicated in the immune response, although its precise role is ill-defined. A recent manuscript reported that GPR35 was able to signal in response to CXCL17, which we set out to confirm in this study. GPR35 was readily expressed using transfection systems but failed to signal in response to CXCL17 in assays of β-arrestin recruitment, inositol phosphate production, calcium flux, and receptor endocytosis. Similarly, in chemotaxis assays, GPR35 did not confirm sensitivity to a range of CXCL17 concentrations above that observed in the parental cell line. We subsequently employed a real time chemotaxis assay (TAXIScan) to investigate the migratory responses of human monocytes and the monocytic cell line THP-1 to a gradient of CXCL17. Freshly isolated human monocytes displayed no obvious migration to CXCL17. Resting THP-1 cells showed a trend toward directional migration along a CXCL17 gradient, which was significantly enhanced by overnight incubation with PGE2 However, pretreatment of PGE2-treated THP-1 cells with the well-characterized GPR35 antagonist ML145 did not significantly impair their migratory responses to CXCL17 gradient. CXCL17 was susceptible to cleavage with chymase, although this had little effect its ability to recruit THP-1 cells. We therefore conclude that GPR35 is unlikely to be a bona fide receptor for CXCL17 and that THP-1 cells express an as yet unidentified receptor for CXCL17.
- The binding of Captopril to Angiotensin-I Converting Enzyme triggers signaling pathways activation. [Journal Article]
- AJAm J Physiol Cell Physiol 2018 Jun 06
- Hypertension is a global health problem and ACE inhibitors are largely used to control this pathology. Recently, it has been shown that ACE can also act as a transducer signal molecule when its inhib...
Hypertension is a global health problem and ACE inhibitors are largely used to control this pathology. Recently, it has been shown that ACE can also act as a transducer signal molecule when its inhibitors or substrates bind to it. This new role of ACE could contribute to understanding some of the effects not explained by its catalytic activity only. In this study we investigated signaling pathways activation in Chinese hamster ovary (CHO) cells stably expressing ACE (CHO-ACE) under different treatments. We also investigated gene modulation after 4h and 24h captopril treatments. Our results demonstrated that CHO-ACE cells when stimulated with AngI, ramipril or captopril led to JNK and ERK1/2 phosphorylation. To verify any physiological role at endogenous level we made use of primary cultures of mesangial cells from spontaneously hypertensive rats (SHR) and Wistar rats. Our results showed that ERK1/2 activation occurred only in primary cultures of mesangial cells from SHR rats upon captopril stimulation suggesting that this signaling pathway is differentially regulated during hypertension. Our results also showed that captopril treatment leads to decrease of COX2, interleukin 1β and β-arrestin 2 gene expression level.Our findings strengthen the fact that in addition to the blockage of enzymatic activity, ACE inhibitors also trigger signaling pathways activation and this may contribute to their beneficial effects in the treatment of hypertension and other pathologies.
- Molecular mechanism of modulating arrestin conformation by GPCR phosphorylation. [Journal Article]
- NSNat Struct Mol Biol 2018; 25(6):538-545
- Arrestins regulate the signaling of ligand-activated, phosphorylated G-protein-coupled receptors (GPCRs). Different patterns of receptor phosphorylation (phosphorylation barcode) can modulate arresti...
Arrestins regulate the signaling of ligand-activated, phosphorylated G-protein-coupled receptors (GPCRs). Different patterns of receptor phosphorylation (phosphorylation barcode) can modulate arrestin conformations, resulting in distinct functional outcomes (for example, desensitization, internalization, and downstream signaling). However, the mechanism of arrestin activation and how distinct receptor phosphorylation patterns could induce different conformational changes on arrestin are not fully understood. We analyzed how each arrestin amino acid contributes to its different conformational states. We identified a conserved structural motif that restricts the mobility of the arrestin finger loop in the inactive state and appears to be regulated by receptor phosphorylation. Distal and proximal receptor phosphorylation sites appear to selectively engage with distinct arrestin structural motifs (that is, micro-locks) to induce different arrestin conformations. These observations suggest a model in which different phosphorylation patterns of the GPCR C terminus can combinatorially modulate the conformation of the finger loop and other phosphorylation-sensitive structural elements to drive distinct arrestin conformation and functional outcomes.
- Strength in numbers-an arrestin interaction code. [Journal Article]
- NSNat Struct Mol Biol 2018; 25(6):437-439
- Synthesis, molecular modelling studies and biological evaluation of new oxoeicosanoid receptor 1 agonists. [Journal Article]
- BMBioorg Med Chem 2018 May 23
- The oxoeicosanoid receptor 1 (OXER1) is a member of the G-protein coupled receptors (GPCR) family, and is involved in inflammatory processes and oncogenesis. As such it is an attractive target for ph...
The oxoeicosanoid receptor 1 (OXER1) is a member of the G-protein coupled receptors (GPCR) family, and is involved in inflammatory processes and oncogenesis. As such it is an attractive target for pharmacological intervention. The present study aimed to shed light on the molecular fundaments of OXER1 modulation using chemical probes structurally related to the natural agonist 5-oxo-ETE. In a first step, 5-oxo-ETE and its closely related derivatives (5-oxo-EPE and 4-oxo-DHA) were obtained by conducting concise and high-yielding syntheses. The biological activity of obtained compounds was assessed in terms of potency (EC50) and efficacy (Emax) for arrestin recruitment. Finally, molecular modelling and simulation were used to explore binding characteristics of 5-oxo-ETE and derivatives with the aim to rationalize biological activity. Our data suggest that the tested 5-oxo-ETE derivatives (i) insert quickly into the membrane, (ii) access the receptor via transmembrane helices (TMs) 5 and 6 from the membrane side and (iii) drive potency and efficacy by differential interaction with TM5 and 7. Most importantly, we found that the methyl ester of 5-oxo-ETE (1a) showed even a higher maximum response than the natural agonist (1). In contrast, shifting the 5-oxo group into position 4 results in inactive compounds (4-oxo DHA compounds (3) and (3a)). All in all, our study provides relevant structural data that help understanding better OXER1 functionality and its modulation. The structural information presented herein will be useful for designing new lead compounds with desired signalling profiles.
New Search Next
- A Surprising Recipe for Designing Biased Ligands. [Journal Article]
- JMJ Med Chem 2018 Jun 04
- The determination of the potential value of receptor trafficking at melanocortin receptors has been hampered by the absence of known biased ligands. Heterobivalent MC4R ligands linking agonist to ant...
The determination of the potential value of receptor trafficking at melanocortin receptors has been hampered by the absence of known biased ligands. Heterobivalent MC4R ligands linking agonist to antagonist small peptidic moieties were designed and found to act as Gαs enhancers while minimally activating β-arrestin recruitment. The strategy invoked offers intriguing promise as a surprising approach that is possibly broadly applicable to the challenge of designing biased ligands at other GPCRs.