Modulation Of Receptor Activity Research Articles

Pharmacological characterization of allosteric modulators:A case for chemokine receptors.

Chemokine receptors are relevant targets for a multitude of immunological diseases, but drug attrition for these receptors is remarkably high. While many drug discovery programs have been pursued, most prospective drugs failed in the follow-up studies due to clinical inefficacy, and hence there is a clear need for alternative approaches. Allosteric modulators of receptor function represent an excellent opportunity for novel drugs, as they modulate receptor activation in a controlled manner and display increased selectivity, and their pharmacological profile can be insurmountable. Here, we discuss allosteric ligands and their pharmacological characterization for modulation of chemokine receptors. Ligands are included if (1) they show clear signs of allosteric modulation in vitro and (2) display evidence of binding in a topologically distinct manner compared to endogenous chemokines. We discuss how allosteric ligands affect binding of orthosteric (endogenous) ligands in terms of affinity as well as binding kinetics in radioligand binding assays. Moreover, their effects on signaling events in functional assays and how their binding site can be elucidated are specified. We substantiate this with examples of published allosteric ligands targeting chemokine receptors and hypothetical graphs of pharmacological behavior. This review should serve as an effective starting point for setting up assays for characterizing allosteric ligands to develop safer and more efficacious drugs for chemokine receptors and, ultimately, other G protein-coupled receptors.

Synthesis, biological evaluation, and stability studies of raloxifene mono- and bis-sulfamates as dual-targeting agents

All three possible sulfamate derivatives of the selective estrogen receptor modulator Raloxifene (bis-sulfamate 7 and two mono-sulfamates 8–9) were synthesized and evaluated as inhibitors of the clinical drug target steroid sulfatase (STS), both in cell-free and in cell-based assays, and also as estrogen receptor (ER) modulators. Bis-sulfamate 7 was the most potent STS inhibitor with an IC50 of 12.2 nM in a whole JEG3 cell-based assay, with the two mono-sulfamates significantly weaker. The estrogen receptor-modulating activities of 7–9 showed generally lower affinities compared to Raloxifene HCl, diethylstilbestrol and other known ligands, with mono-sulfamate 8 being the best ligand (Ki of 1.5 nM) for ERα binding, although 7 had a Ki of 13 nM and both showed desirable antagonist activity. The antiproliferative activities of the sulfamate derivatives against the T-47D breast cancer cell line showed 7 as most potent (GI50 = 7.12 µM), comparable to that of Raloxifene. Compound 7 also showed good antiproliferative potency in the NCI-60 cell line panel with a GI50 of 1.34 µM against MDA-MB-231 breast cancer cells. Stability testing of 7–9 showed that bis-sulfamate 7 hydrolyzed by desulfamoylation at a surprisingly rapid rate, initially leading selectively to 8 and finally to Raloxifene 3 without formation of 9. The mechanisms of these hydrolysis reactions could be extensively rationalized. Conversion of Raloxifene (3) into its bis-sulfamate (7) thus produced a promising drug lead with nanomolar dual activity as an STS inhibitor and ERα antagonist, as a potential candidate for treatment of estrogen-dependent breast cancer.

Membrane-Mediated Allosteric Action of Serotonin on a Noncognate G-Protein-Coupled Receptor.

The structure and dynamics of the lipid membrane can affect the activity of membrane proteins. Therefore, small lipophilic molecules that alter membrane properties (such as the neurotransmitter serotonin) can potentially modulate receptor activity without binding to the receptor. Here, we investigated how the activity of neuropeptide Y type 4 receptor (Y4R, reconstituted in lipid bicelles) is modulated by serotonin, which has no known interaction with Y4R. We found a serotonin-concentration-dependent decrease (down to 0.1 mM of serotonin) in the ligand affinity of Y4R. This effect correlates with a serotonin-induced reduction of the resistance of the bilayer to indentation (measured by atomic force microscopy) and bilayer thickness (measured by solid state NMR) in two different types of zwitterionic lipid bicelles. Our findings indicate a "membrane-mediated allosteric effect" of serotonin on the activation of Y4R and suggest the potential for developing pharmacophores, which can modulate cellular signaling without directly interacting with any receptor.

Molecular Docking Studies of Thiazolidinediones on Receptor for Advanced Glycation End Products (RAGE)

Background: Advanced glycation end products (AGE), are abnormal glycation of molecular proteins and nucleic acid, and its interaction with receptors for advanced glycation end products (RAGE) culminates in metabolic, neurodegenerative, and lifestyle disorders. Thiazolidinediones are insulin sensitizers with anti-glycation activity and are currently used clinically as anti-diabetic drugs. Research rationale: Studies show that thiazolidinediones also exhibit antioxidant and antiglycation activity; hence we proposed that this anti-glycation activity of thiazolidinedione may be due to its anti-RAGE action, thus preventing further RAGE-AGE interaction. Purpose of the study: Aim of the current study is to assess In-silico anti-RAGE activity of nine thiazolidinediones namely pioglitazone, rosiglitazone, ciglitazone, darglitazone, englitazone, netoglitazone, rivoglitazone, troglitazone and balaglitazone with RAGE. Materials and Methods: Nine thiazolidinediones namely, pioglitazone, rosiglitazone, ciglitazone, darglitazone, englitazone, netoglitazone, rivoglitazone, troglitazone and balaglitazone were downloaded from PubChem database. RAGE protein was downloaded from the PDB database. The nine thiazolidinediones were docked with RAGE protein using Auto Dock software and interaction parameters were studied. Result: All nine thiazolidinediones showed acceptable binding energy below (-8Kcal/mol) with 1-5 hydrogen bonds. Rosiglitazone exhibits the highest binding energy (-8.24Kcal/mol) with 2 hydrogen bonds for RAGE. Troglitazone exhibits the lowest binding energy (-9.95Kcal/mol) with 3 hydrogen bonds for RAGE. Conclusion: Thus our Insilco docking studies of thiazolidinedione derivatives with RAGE conclude that these nine thiazolidinedione derivatives exhibit anti-glycation activity by direct interaction with receptors of RAGE. Thus, this work warrants future preclinical studies to claim its RAGE receptor modulation activity.

Molecular design of peptide therapeutics via N-terminal modification.

Glucagon-like peptide-1, glucose-dependent insulinotropic polypeptide, and glucagon are three naturally occurring peptide hormones that mediate glucoregulation. Several agonists representing appropriately modified native ligands have been developed to maximize metabolic benefits with reduced side-effects and many have entered the clinic as type 2 diabetes and obesity therapeutics. In this work, we describe strategies for improving the stability of the peptide ligands by making them refractory to dipeptidyl peptidase-4 catalyzed hydrolysis and inactivation. We describe a series of alkylations with variations in size, shape, charge, polarity, and stereochemistry that are able to engender full activity at the receptor(s) while simultaneously resisting enzyme-mediated degradation. Utilizing this strategy, we offer a novel method of modulating receptor activity and fine-tuning pharmacology without a change in peptide sequence.

Thiophene derivative inflicts cytotoxicity via an intrinsic apoptotic pathway on human acute lymphoblastic leukemia cells.

In an effort to identify novel anti-cancer agents, we employed a well-established High Throughput Screening (HTS) assay to assess the cytotoxic effect of compounds within the ChemBridge DIVERSet Library on a lymphoma cell line. This screen revealed a novel thiophene, F8 (methyl 5-[(dimethylamino)carbonyl]-4-methyl-2-[(3-phenyl-2-propynoyl) amino]-3-thiophenecarboxylate), that displays anti-cancer activity on lymphoma, leukemia, and other cancer cell lines. Thiophenes and thiophene derivatives have emerged as an important class of heterocyclic compounds that have displayed favorable drug characteristics. They have been previously reported to exhibit a broad spectrum of properties and varied uses in the field of medicine. In addition, they have proven to be effective drugs in various disease scenarios. They contain anti-inflammatory, anti-anxiety, anti-psychotic, anti-microbial, anti-fungal, estrogen receptor modulating, anti-mitotic, kinase inhibiting and anti-cancer activities, rendering compounds with a thiophene a subject of significant interest in the scientific community. Compound F8 consistently induced cell death at a low micromolar range on a small panel of cancer cell lines after a 48 h period. Further investigation revealed that F8 induced phosphatidylserine externalization, reactive oxygen species generation, mitochondrial depolarization, kinase inhibition, and induces apoptosis. These findings demonstrate that F8 has promising anti-cancer activity.

Respiratory syncytial virus–approved mAb Palivizumab as ligand for anti-idiotype nanobody-based synthetic cytokine receptors

Synthetic cytokine receptors can modulate cellular functions based on an artificial ligand to avoid off-target and/or unspecific effects. However, ligands that can modulate receptor activity so far have not been used clinically because of unknown toxicity and immunity against the ligands. Here, we developed a fully synthetic cytokine/cytokine receptor pair based on the antigen-binding domain of the respiratory syncytial virus-approved mAb Palivizumab as a synthetic cytokine and a set of anti-idiotype nanobodies (AIPVHH) as synthetic receptors. Importantly, Palivizumab is neither cross-reactive with human proteins nor immunogenic. For the synthetic receptors, AIPVHH were fused to the activating interleukin-6 cytokine receptor gp130 and the apoptosis-inducing receptor Fas. We found that the synthetic cytokine receptor AIPVHHgp130 was efficiently activated by dimeric Palivizumab single-chain variable fragments. In summary, we created an invitro nonimmunogenic full-synthetic cytokine/cytokine receptor pair as a proof of concept for future invivo therapeutic strategies utilizing nonphysiological targets during immunotherapy.

The estrogen receptor modulatory activity and neuroprotective activity of novel prenylated flavonoids and their structure–activity relationship

AbstractPrenylated flavonoids are promising nutraceuticals with diverse bioactivities. However, publications on the mechanism of action and structure–activity relationship of prenylated flavonoids are limited. In the present work, six novel prenylated flavonoids (C8–C13) with diversity structure were prepared. Their estrogen receptor (ER) modulator activity and neuroprotective activity were investigated by cell assays. C8, C9, and C10 with 8‐C‐prenyl and 7‐OH showed agonistic activities toward ERα and ERβ, along with high ERβ selectivity. However, C11 and C12 were ERα‐selective agonists. The position and substituent moiety of prenylation, C‐ring configuration, and flavonoid skeleton were important for the ER modulating activities. Hydrogen bonds between 3′‐OH and Leu339 in ERβ, and 5′‐OH and Glu305 in ERβ might respond for the higher agonistic activity of C8 and C10, respectively. C8, C9, C11, and C12 showed more potency than 17β‐estradiol on neuroprotection in glutamate‐treated PC‐12 cells. C8 and C12 could reverse reactive oxygen species overproduction and reduction of Δψm induced by glutamate through increase of the expression of ERS1, SOD1, SOD2, CAT, and GPx4 and decrease of caspase‐3 expression, suggesting C8, and C9 might interact with ERα, promote antioxidant defense, mitigate oxidative stress, and improve mitochondrial function to exert the neuroprotection activities.

The immune activity of selective estrogen receptor modulators is gene and macrophage subtype-specific yet converges on Il1b downregulation

Raloxifene belongs to the family of Selective Estrogen Receptor Modulators (SERMs), which are drugs widely prescribed for Estrogen Receptor alpha (ERα)-related pathologies. Recently, SERMs are being tested in repurposing strategies for ERα-independent clinical indications, including a wide range of microbial infections. Macrophages are central in the fight against pathogen invasion. Despite estrogens have been shown to regulate macrophage phenotype, SERMs activity in these cells is still poorly defined. We investigated the activity of Raloxifene in comparison with another widely used SERM, Tamoxifen, on immune gene expression in macrophages obtained from mouse and human tissues, including mouse peritoneal macrophages, bone marrow-derived macrophages, microglia or human blood-derived macrophages, assaying for the involvement of the ERα, PI3K and NRF2 pathways also under inflammatory conditions. Our data demonstrate that Raloxifene acts by a dual mechanism, which entails ERα antagonism and off-target mediators. Moreover, micromolar concentrations of Raloxifene increase the expression of immune metabolic genes, such as Vegfa and Hmox1, through PI3K and NRF2 activation selectively in peritoneal macrophages. Conversely, Il1b mRNA down-regulation by SERMs is consistently observed in all macrophage subtypes and unrelated to the PI3K/NRF2 system. Importantly, the production of the inflammatory cytokine TNFα induced by the bacterial endotoxin, LPS, is potentiated by SERMs and paralleled by the cell subtype-specific increase in IL1β secretion. This work extends our knowledge on the biological and molecular mechanisms of SERMs immune activity and indicate macrophages as a pharmacological target for the exploitation of the antimicrobial potential of these drugs.

Differential Activity of Orthosteric Agonists and Allosteric Modulators at Metabotropic Glutamate Receptor 7.

Metabotropic glutamate receptor 7 (mGlu7) is a G protein coupled receptor that has demonstrated promise as a therapeutic target across a number of neurologic and psychiatric diseases. Compounds that modulate the activity of mGlu7, such as positive and negative allosteric modulators, may represent new therapeutic strategies to modulate receptor activity. The endogenous neurotransmitter associated with the mGlu receptor family, glutamate, exhibits low efficacy and potency in activating mGlu7, and surrogate agonists, such as the compound L-(+)-2-Amino-4-phosphonobutyric acid (L-AP4), are often used for receptor activation and compound profiling. To understand the implications of the use of such agonists in the development of positive allosteric modulators (PAMs), we performed a systematic evaluation of receptor activation using a system in which mutations can be made in either protomer of the mGlu7 dimer; we employed mutations that prevent interaction with the orthosteric site as well as the G-protein coupling site of the receptor. We then measured increases in calcium levels downstream of a promiscuous G protein to assess the effects of mutations in one of the two protomers in the presence of two different agonists and three positive allosteric modulators. Our results reveal that distinct PAMs, for example N-[3-Chloro-4-[(5-chloro-2-pyridinyl)oxy]phenyl]-2-pyridinecarboxamide (VU0422288) and 3-(2,3-Difluoro-4-methoxyphenyl)-2,5-dimethyl-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine (VU6005649), do exhibit different maximal levels of potentiation with L-AP4 versus glutamate, but there appear to be common stable receptor conformations that are shared among all of the compounds examined here. SIGNIFICANCE STATEMENT: This manuscript describes the systematic evaluation of the mGlu7 agonists glutamate and L-(+)-2-Amino-4-phosphonobutyric acid (L-AP4) in the presence and absence of three distinct potentiators examining possible mechanistic differences. These findings demonstrate that mGlu7 potentiators display subtle variances in response to glutamate versus L-AP4.

Role of Insect and Mammal Glutathione Transferases in Chemoperception.

Glutathione transferases (GSTs) are ubiquitous key enzymes with different activities as transferases or isomerases. As key detoxifying enzymes, GSTs are expressed in the chemosensory organs. They fulfill an essential protective role because the chemosensory organs are located in the main entry paths of exogenous compounds within the body. In addition to this protective function, they modulate the perception process by metabolizing exogenous molecules, including tastants and odorants. Chemosensory detection involves the interaction of chemosensory molecules with receptors. GST contributes to signal termination by metabolizing these molecules. By reducing the concentration of chemosensory molecules before receptor binding, GST modulates receptor activation and, therefore, the perception of these molecules. The balance of chemoperception by GSTs has been shown in insects as well as in mammals, although their chemosensory systems are not evolutionarily connected. This review will provide knowledge supporting the involvement of GSTs in chemoperception, describing their localization in these systems as well as their enzymatic capacity toward odorants, sapid molecules, and pheromones in insects and mammals. Their different roles in chemosensory organs will be discussed in light of the evolutionary advantage of the coupling of the detoxification system and chemosensory system through GSTs.

Design and Synthesis of New Quinazolin-4-one Derivatives with Negative mGlu7 Receptor Modulation Activity and Antipsychotic-Like Properties.

Following the glutamatergic theory of schizophrenia and based on our previous study regarding the antipsychotic-like activity of mGlu7 NAMs, we synthesized a new compound library containing 103 members, which were examined for NAM mGlu7 activity in the T-REx 293 cell line expressing a recombinant human mGlu7 receptor. Out of the twenty-two scaffolds examined, active compounds were found only within the quinazolinone chemotype. 2-(2-Chlorophenyl)-6-(2,3-dimethoxyphenyl)-3-methylquinazolin-4(3H)-one (A9-7, ALX-171, mGlu7 IC50 = 6.14 µM) was selective over other group III mGlu receptors (mGlu4 and mGlu8), exhibited satisfactory drug-like properties in preliminary DMPK profiling, and was further tested in animal models of antipsychotic-like activity, assessing the positive, negative, and cognitive symptoms. ALX-171 reversed DOI-induced head twitches and MK-801-induced disruptions of social interactions or cognition in the novel object recognition test and spatial delayed alternation test. On the other hand, the efficacy of the compound was not observed in the MK-801-induced hyperactivity test or prepulse inhibition. In summary, the observed antipsychotic activity profile of ALX-171 justifies the further development of the group of quinazolin-4-one derivatives in the search for a new drug candidate for schizophrenia treatment.

Abstract 1530: Derivatives of betulinic acid act as modulators of the androgen receptor and report cytotoxicity towards cancer cell lines

Abstract INTRODUCTION Triterpenoids are naturally occurring substances with a broad spectrum of beneficial effects for human health. Betulinic acid belongs to the group of pentacyclic triterpenoids and is well known for its antitumor activities. The library of about 1000 betulinic acid-derived triterpenes was collected and analyzed for cytotoxic activity on cancer and non-cancer cell lines (A549, CCRF-CEM, CEM-DNR, HCT116, K562, K562-TAX, U2OS, BJ and MRC-5) in our Institute over the last 20 years. Steroidal triterpenes are precursors of cholesterol, the precursor of testosterone, the fundamental ligand of the androgen receptor that is the key regulator in several physiological and pathological processes. Finding new modulators of androgen receptor is critical for the treatment of various androgen-dependent diseases, including prostate cancer or anabolic deficiencies. Betulinic acid and its derivatives showed structural similarity with steroids and therefore were selected to be tested for androgen receptor activity modulation. METHODS The stably transfected cell line HEK 293T GFP-AR was used to determine the translocation activity of the androgen receptor from the cytoplasm to the nucleus after the treatment with the derivatives. The high throughput fluorescent microscopy device and image analysis comprised the data, and compounds with the proved activity were selected for subsequent analysis. The luciferase reporter gene assay was further used to evaluate the effect of compounds on the transcriptional activity of the androgen receptor. The MTS assay was performed to assess the cytotoxicity. RESULTS Betulinic acid and its eight derivatives were identified to have 5-6 - fold higher translocation activity of AR (ratio cytoplasm GFP intensity/nuclear GFP intensity) than the negative control. Validation on luminescence luciferase reporter assay confirmed 4-5 - fold induction for five derivatives, whereas three derivatives were not active. Interestingly only two of them showed substantial cytotoxicities (IC50< 50 µM) as they possess significant inhibitory activity against all tested cancer cell lines with favorable therapeutic index against the non-cancer cell lines. CONCLUSION Derivatives of betulinic acid were proven to have modulatory activity on the androgen receptor pathway. The two derivatives of betulinic acid also displayed cytotoxicity towards almost all of the tested cancer cell lines. There could be not only AR modulation responsible for anticancer activity as the derivatives of betulinic acid are well know disruptors of mitochondrion functions as well. The synergy of these two mechanisms of action could potentiate the antitumor activity of the selected compounds. This work was supported by ENOCH CZ.02.1.01/0.0/0.0/16_019/0000868, CZ-OPENSCREEN - LM2018130, EATRIS-CZ - LM2018133. Citation Format: Alzbeta Srovnalova, Sona Gurska, Milan Urban, Jan Sarek, Jiri Rehulka, Petr Dzubak, Marian Hajduch. Derivatives of betulinic acid act as modulators of the androgen receptor and report cytotoxicity towards cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1530.

Structure–Activity Relationships of a Negative Allosteric Modulator of the D3 Dopamine Receptor and Investigation of its Binding Site

Dopamine receptors (DARs) are G protein‐coupled receptors (GPCRs) that regulate diverse physiological functions and are involved in the treatment and/or etiology of many neuropsychiatric disorders including schizophrenia and substance use disorder (SUD). DARs are classified as either D1‐like (D1R and D5R) or D2‐like (D2R, D3R, and D4R) based on structural homology and pharmacological profiles. Antagonists of D2‐like DARs are currently used in the therapies for many neuropsychiatric disorders. D3R‐selective antagonists have the potential to be better therapeutics for schizophrenia or SUD as they could attenuate psychotic or drug craving symptoms without the motor side effects frequently produced by D2R‐preferring antagonists. Unfortunately, discovery of subtype‐selective compounds for the D3R and D2R has been challenging due to high sequence homology within the orthosteric binding sites of DARs. However, compounds that modulate receptor activities through interactions with less conserved allosteric sites have the potential to be highly selective. To find highly selective allosteric antagonists of the D3R, we screened the NIH Molecular Libraries Program 400,000+ small molecule library with a D3R‐mediated β‐arrestin recruitment assay. We found that one compound, MLS6357, was selective for the D3R over the D2R and D4R in several functional outputs including β‐arrestin recruitment and G‐protein activation. Radioligand binding and functional assays using closely related GPCRs revealed that MLS6357 has very limited cross‐reactivity with other GPCRs. Additionally, Schild‐type functional assays showed that MLS6357 acts as a purely non‐competitive negative allosteric modulator (NAM) of the D3R. We synthesized and characterized >60 analogs of MLS6357 using iterative medicinal chemistry approaches, which revealed structure–activity relationships and enabled further optimization of the scaffold. These efforts produced analogs that are 10‐fold and 30‐fold more potent than the parent compound in D3R‐mediated β‐arrestin recruitment and G‐protein activation assays, respectively. Moreover, some analogs appear to display functional selectivity for inhibition of G‐protein activation versus inhibition of β‐arrestin recruitment, and vice versa, and some also display inverse agonist activity. To identify the allosteric binding site for the MLS6357 scaffold on the D3R, we utilized various D3R/D2R chimeras, receptor mutants, and molecular modeling techniques to reveal and characterize receptor regions necessary for compound efficacy. Further refinement of the binding pocket for MLS6357 will inform future medicinal chemistry efforts. Ultimately, this novel scaffold may be of benefit as a pharmacological probe or therapeutic lead for D3R‐related pathophysiology.

Selective Estrogen Receptor Modulators (SERMs) Synergize with Cisplatin, Induce Apoptosis and Suppress Cellular Migration and Colony Formation of Lung Cancer Cells.

Lung cancer remains the leading cause of cancer-related deaths worldwide. Hence, novel therapeutic approaches targeting crucial pathways are needed to improve its treatment. Previous studies have verified the involvement of the estrogen pathway, mediated through estrogen receptor β (ERβ), in the development and progression of lung carcinogenesis. Selective estrogen receptor modulators (SERMs) are a group of estrogen receptor agonists/antagonists that have tissue selective effects. Many of the available SERMs are used for the management of breast cancer. However, their role in lung cancer is still under investigation. The aim of this research is to investigate the anti-tumorigenic activity of the selective estrogen receptor modulators, tamoxifen, raloxifene, and toremifene, against different lung cancer cell lines. The anti-proliferative and combined effects of SERMs with standard chemotherapy were evaluated by MTT assay. Cell migration was assessed using a wound-healing assay. The mechanism of cell death was determined using the Annexin V-FITC/ propidium iodide staining flow cytometry method. Cells' capability to form colonies was evaluated by soft agar colony formation assay. Estrogen receptors expression was determined using real-time PCR. Our results have demonstrated the presence of ERβ in A549, H1299, and H661 lung cancer cells. Cellular proliferation assay suggested that SERMs have significantly reduced lung cancer cells proliferation in a time and concentration- dependent manner. Additionally, SERMs exhibited a synergistic effect against A549 cells when combined with cisplatin. SERMs treatment have increased cell apoptosis and resulted in concentration-dependent inhibition of cell migration and colony formation of A549 cells. Selective estrogen receptor modulators may possess potential therapeutic utility for the treatment of lung cancer as monotherapy or in combination with standard chemotherapy.

Activation of the adhesion G protein–coupled receptor GPR133 by antibodies targeting its N-terminus

We recently demonstrated that GPR133 (ADGRD1), an adhesion G protein–coupled receptor involved in raising cytosolic cAMP levels, is necessary for growth of glioblastoma (GBM) and is de novo expressed in GBM relative to normal brain tissue. Our previous work suggested that dissociation of autoproteolytically generated N-terminal and C-terminal fragments of GPR133 at the plasma membrane correlates with receptor activation and signaling. To promote the goal of developing biologics that modulate GPR133 function, we investigated the effects of antibodies against the N-terminus of GPR133 on receptor signaling. Here, we show that treatment of HEK293T cells overexpressing GPR133 with these antibodies increased cAMP levels in a concentration-dependent manner. Analysis of culture medium following antibody treatment further indicated the presence of complexes of these antibodies with the autoproteolytically cleaved N-terminal fragments of GPR133. In addition, cells expressing a cleavage-deficient mutant of GPR133 (H543R) did not respond to antibody stimulation, suggesting that the effect is cleavage dependent. Finally, we demonstrate the antibody-mediated stimulation of WT GPR133, but not the cleavage-deficient H543R mutant, was reproducible in patient-derived GBM cells. These findings provide a paradigm for modulation of GPR133 function with biologics and support the hypothesis that the intramolecular cleavage in the N-terminus modulates receptor activation and signaling.

Transcutaneous vagus nerve stimulation attenuates autoantibody-mediated cardiovagal dysfunction and inflammation in a rabbit model of postural tachycardia syndrome.

Previous studies demonstrated M2 muscarinic acetylcholine receptor-activating autoantibodies (M2R-AAb) were present in some patients with postural tachycardia syndrome (POTS). This study examines how these autoantibodies might contribute to the pathophysiology of POTS, and whether low-level tragus stimulation (LLTS) can ameliorate autoantibody-mediated autonomic dysregulation in the rabbit. Five New Zealand white rabbits were immunized with a M2R second extracellular loop peptide to produce cholinomimetic M2R-AAb. Tilt test and infusion studies were performed on conscious rabbits before immunization, 6weeks after immunization, and 8weeks after immunization with 2-week daily LLTS treatment. Each rabbit served as its own control. Compared to preimmune state, an enhanced heart rate increase and decreased parasympathetic activity upon tilting were observed in immunized rabbits. Furthermore, these rabbits demonstrated an attenuated heart rate-slowing response to infusion of the M2R orthosteric agonist arecaidine propargyl ester (APE), suggesting an inhibitory allosteric effect of M2R-AAb. There was also a significant increase in serum inflammatory cytokines in immunized rabbits. LLTS treatment suppressed the postural tachycardia, improved the sympathovagal balance with increased acetylcholine secretion, reduced the levels of inflammatory cytokines, and reversed the attenuated heart rate response to APE in immunized rabbits. No suppression of M2R-AAb expression by LLTS was found during this short-term study period. Receptor-modulating activity of M2R-AAb produced in immunized rabbits was confirmed with in vitro bioassay. Autoantibody inhibition of cholinergic ligand activity may be involved in the development of cardiovagal dysfunction and inflammation associated with POTS, both of which can be improved by vagal stimulation.

Challenging Approach to the Development of Novel Estrogen Receptor Modulators Based on the Chemical Properties of Guaiazulene.

Tamoxifen, a therapeutic agent for breast cancer, has been associated with genetic polymorphisms in the metabolism of N,N-dialkylaminoethyl substituent, which plays an important role in the expression of selective estrogen receptor modulator (SERM) activity. To solve this problem, we developed a novel estrogen receptor (ER) modulator, Az-01, on the basis of the aromaticity, dipole moment, and isopropyl group of guaiazulene. Az-01 showed four-fold lower binding affinity for ER than E2 but had similar ER-binding affinity to that of 4-hydroxytamoxifen (4-HOtam). Unlike tamoxifen, Az-01 acted as a partial agonist with very weak estrogenic activity at high concentrations when used alone, and it showed potent anti-estrogenic activity in the presence of E2. The cell proliferation and inhibition activities of Az-01 were specific to ER-expressing MCF-7 cells, and no effect of Az-01 on other cell proliferation signals was observed. These findings are important for the development of new types of SERMs without the N,N-dialkylaminoethyl substituent as a privileged functional group for SERMs.

A Surface Plasmon Resonance-Based Strategy to Characterize Interactions of NLR Proteins with Associated Factors.

NOD-like receptors (NLRs) are established as key regulators of the innate immune system. In recent years, an increasing number of interaction partners have been described that modulate receptor activity by direct binding. Characterizing these interactions can be challenging because these receptors tend to adopt different conformational states. We have developed a protocol that employs intracellular protein biotinylation to provide a straightforward immobilization strategy in surface plasmon resonance experiments. With this highly sensitive and label-free technique, the kinetics and affinities of NLR and co-factor interactions can be measured directly at the protein level.

Probing Allosteric Modulation of Membrane Receptor in the Native State by Data Mining-Integrated Tracking Microscopy

Probing Allosteric Modulation of Membrane Receptor in the Native State by Data Mining-Integrated Tracking Microscopy