MGluR7 allosteric modulator AMN082 corrects protein synthesis and pathological phenotypes in FXS
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ABSTRACT:
SUBMITTER: Dr. Vipendra Kumar
PROVIDER: S-SCDT-10_1038-S44321-024-00038-W | biostudies-other |
REPOSITORIES: biostudies-other
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Project description:Background and purposeThe δ-opioid receptor is an emerging target for the management of chronic pain and depression. Biased signalling, the preferential activation of one signalling pathway over another downstream of δ-receptors, may generate better therapeutic profiles. BMS 986187 is a positive allosteric modulator of δ-receptors. Here, we ask if BMS 986187 can directly activate the receptor from an allosteric site, without an orthosteric ligand, and if a signalling bias is generated.Experimental approachWe used several clonal cell lines expressing δ-receptors, to assess effects of BMS 986187 on events downstream of δ-receptors by measuring G-protein activation, β-arrestin 2 recruitment, receptor phosphorylation, loss of surface receptor expression, ERK1/ERK2 phosphorylation, and receptor desensitization.Key resultsBMS 986187 is a G protein biased allosteric agonist, relative to β-arrestin 2 recruitment. Despite showing direct and potent G protein activation, BMS 986187 has a low potency to recruit β-arrestin 2. This appears to reflect the inability of BMS 986187 to elicit any significant receptor phosphorylation, consistent with low receptor internalization and a slower onset of desensitization, compared with the full agonist SNC80.Conclusions and implicationsThis is the first evidence of biased agonism mediated through direct binding to an allosteric site on an opioid receptor, without a ligand at the orthosteric site. Our data suggest that agonists targeting δ-receptors, or indeed any GPCR, through allosteric sites may be a novel way to promote signalling bias and thereby potentially produce a more specific pharmacology than can be observed by activation via the orthosteric site.
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Project description:Receptor component protein (RCP) is a 148 amino acid intracellular peripheral membrane protein, previously identified as promoting the coupling of CGRP to cAMP production at the CGRP receptor, a heterodimer of calcitonin receptor like-receptor (CLR), a family B G protein-coupled receptor (GPCR) and receptor activity modifying protein 1 (RAMP1). We extend these observations to show that it selectively enhances CGRP receptor coupling to Gs but not Gq or pERK activation. At other family B GPCRs, it enhances cAMP production at the calcitonin, corticotrophin releasing factor type 1a and glucagon-like peptide type 2 receptors with their cognate ligands but not at the adrenomedullin type 1 (AM1), gastric inhibitory peptide and glucagon-like peptide type 1 receptors, all expressed in transfected HEK293S cells. However, there is also cell-line variability as RCP did not enhance cAMP production at the endogenous calcitonin receptor in HEK293T cells and it has previously been reported that it is active on the AM1 receptor expressed on NIH3T3 cells. RCP appears to behave as a positive allosteric modulator at coupling a number of family B GPCRs to Gs, albeit in a manner that is regulated by cell-specific factors. It may exert its effects at the interface between the 2nd intracellular loop of the GPCR and Gs, although there is likely to be some overlap between this location and that occupied by the C-terminus of RAMPs if they bind to the GPCRs.
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Project description:Canonical targeting of Polycomb Repressive Complex 1 (PRC1) to repress developmental genes is mediated by cell type-specific, paralogous chromobox (CBX) proteins (CBX2, 4, 6, 7 and 8). Based on their central role in silencing and their dysregulation associated with human disease including cancer, CBX proteins are attractive targets for small molecule chemical probe development. Here, we have used a quantitative and target-specific cellular assay to discover a potent positive allosteric modulator (PAM) of CBX8. The PAM activity of UNC7040 antagonizes H3K27me3 binding by CBX8 while increasing interactions with nucleic acids. We show that treatment with UNC7040 leads to efficient and selective eviction of CBX8-containing PRC1 from chromatin, loss of silencing and reduced proliferation across different cancer cell lines. Our discovery and characterization of UNC7040 not only reveals the most cellularly potent CBX8-specific chemical probe to date, but also corroborates a mechanism of Polycomb regulation by non-specific CBX nucleotide binding activity.
2022-01-03 | GSE182592 | GEO
Project description:Hepatitis B e antigen (HBeAg) is an important immunomodulator for promoting host immune tolerance during chronic hepatitis B (CHB) infection. In patients with CHB, HBeAg loss and seroconversion represent partial immune control of CHB infection and are regarded as valuable endpoints. However, the current approved treatments have only a limited efficacy in achieving HBeAg seroconversion in HBeAg-positive patients. Hepatitis B virus (HBV) core protein has been recognized as an attractive antiviral target, and two classes of core protein allosteric modulator (CpAM) have been discovered: the phenylpropenamides (PPAs) and the heteroaryldihydropyrimidines (HAPs). However, their differentiation and potential therapeutic benefit beyond HBV DNA inhibition remain to be seen. Here, we show that in contrast to PPA series compound AT-130, a HAP CpAM, HAP_R01, reduced HBeAg levels in multiple in vitro and in vivo HBV experimental models. Mechanistically, we found that HAP_R01 treatment caused the misassembly of capsids formed by purified HBeAg in vitro. In addition, HAP_R01 directly reduces HBeAg levels by inducing intracellular precore protein misassembly and aggregation. Using a HAP_R01-resistant mutant, we found that HAP_R01-mediated HBeAg and core protein reductions were mediated through the same mechanism. Furthermore, HAP_R01 treatment substantially reduced serum HBeAg levels in an HBV mouse model. Conclusion: Unlike PPA series compound AT-130, HAP_R01 not only inhibits HBV DNA levels but also directly reduces HBeAg through induction of its misassembly. HAP_R01, as well as other similar CpAMs, has the potential to achieve higher anti-HBeAg seroconversion rates than currently approved therapies for patients with CHB. Our findings also provide guidance for dose selection when designing clinical trials with molecules from HAP series.
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Project description:Biased agonism is a paradigm that may explain the selective activation of a signaling pathway via a GPCR that activates multiple signals. The autoantibody-induced inactivation of the calcium-sensing receptor (CaSR) causes acquired hypocalciuric hypercalcemia (AHH). Here, we describe an instructive case of AHH in which severe hypercalcemia was accompanied by an increased CaSR antibody titer. These autoantibodies operated as biased allosteric modulators of CaSR by targeting its Venus flytrap domain near the Ca2+-binding site. A positive allosteric modulator of CaSR, cinacalcet, which targets its transmembrane domain, overcame this autoantibody effect and successfully corrected the hypercalcemia in this patient. Hence, this is the first study to our knowledge that identifies the interaction site of a disease-causing GPCR autoantibody working as its biased allosteric modulator and demonstrates that cinacalcet can correct the AHH autoantibody effects both in vitro and in our AHH patient. Our observations provide potentially new insights into how biased agonism works and how to design a biased allosteric modulator of a GPCR. Our observations also indicate that the diagnosis of AHH is important because the severity of hypercalcemia may become fatal if the autoantibody titer increases. Calcimimetics may serve as good treatment options for some patients with severe AHH.
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Project description:The parathyroid hormone type 1 receptor (PTH1R) acts as a canonical class B G protein-coupled receptor, regulating crucial functions including calcium homeostasis and bone formation. The identification and development of PTH1R non-peptide allosteric modulators have obtained widespread attention. It has been found that a negative allosteric modulator (NAM) could inhibit the activation of PTH1R, but the implied mechanism remains unclear. Herein, extensive molecular dynamics simulations together with multiple analytical approaches are utilized to unravel the mechanism of PTH1R allosteric inhibition. The results suggest that the binding of NAM destabilizes the structure of the PTH1R-PTH-spep/qpep (the C terminus of Gs/Gq proteins) complexes. Moreover, the presence of NAM weakens the binding of PTH/peps (spep and qpep) and PTH1R. The intra- and inter-molecular couplings are also weakened in PTH1R upon NAM binding. Interestingly, compared with our previous study of the positive allosteric effects induced by extracellular Ca2+, the enhanced correlation between the PTH and G-protein binding sites is significantly reduced by the replacement of this negative allosteric regulator. Our findings might contribute to the development of new therapeutic agents for diseases caused by the abnormal activation of PTH1R.
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