Live-cell microscopy or fluorescence anisotropy with budded baculoviruses - which way to go with measuring ligand binding to M4 muscarinic receptors?

Tahk, M.-J.; Torp, J.; Ali, M. A. S.; Fishman, D.; Parts, L.; Grätz, L.; Müller, C.; Keller, M.; Veiksina, S.; Laasfeld, T.; Rinken, A.

doi:10.1101/2021.12.22.473643

bioRxiv · 10.1101/2021.12.22.473643

Live-cell microscopy or fluorescence anisotropy with budded baculoviruses - which way to go with measuring ligand binding to M4 muscarinic receptors?

Tahk, M.-J.·Torp, J.·Ali, M. A. S.·Fishman, D.·Parts, L.·Grätz, L.·Müller, C.·Keller, M.·Veiksina, S.·Laasfeld, T.·Rinken, A.

View original source ↗Export metadata ↓

Abstract

M4 muscarinic receptor is a G protein-coupled receptor that has been associated with alcohol and cocaine abuse, Alzheimers disease and schizophrenia which makes it an interesting drug target. For many G protein-coupled receptors, the development of high-affinity fluorescence ligands has expanded the options for high throughput screening of drug candidates and serve as useful tools in fundamental receptor research. So far, the lack of suitable fluorescence ligands has limited studying M4 receptor ligand binding. Here, we explored the possibilities of using fluorescence-based methods for studying binding affinity and kinetics to M4 receptor of both labeled and unlabeled ligands. We used two TAMRA-labeled fluorescence ligands, UR-MK342 and UR-CG072, for assay development. Using budded baculovirus particles as M4 receptor preparation and fluorescence anisotropy method, we determined the affinities and binding kinetics of both fluorescence ligands. The fluorescence ligands could also be used as reported probes for determining binding affinities of a set of unlabeled ligands. Based on these results, we took a step further towards a more natural signaling system and developed a method using live CHO-K1-hM4R cells and automated fluorescence microscopy suitable for routine determination of unlabeled ligand affinities. For quantitative image analysis, we developed random forest and deep learning-based pipelines for cell segmentation. The pipelines were integrated into the user-friendly open-source Aparecium software. Both developed methods were suitable for measuring fluorescence ligand saturation binding, association and dissociation kinetics as well as for screening binding affinities of unlabeled ligands. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/473643v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@17dfac6org.highwire.dtl.DTLVardef@1db1760org.highwire.dtl.DTLVardef@dba2a0org.highwire.dtl.DTLVardef@191f149_HPS_FORMAT_FIGEXP M_FIG C_FIG

Source connections

Published article ↗

Explore related subjects

pharmacology and toxicology Preprint

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Tahk, M.-J., Torp, J., Ali, M. A. S., Fishman, D., Parts, L., Grätz, L., Müller, C., Keller, M., Veiksina, S., Laasfeld, T., Rinken, A.. 2021-12-23. Live-cell microscopy or fluorescence anisotropy with budded baculoviruses - which way to go with measuring ligand binding to M4 muscarinic receptors?. https://doi.org/10.1101/2021.12.22.473643

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

PCB-Exposed Gut Microbiota Recapitulate Neurobehavioral Deficits and Reprogram Hippocampal Transcriptomic Signatures

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants associated with developmental neurotoxicity and autism spectrum disorder (ASD). However, whether PCB-induced alterations in gut microbiota contribute to neurodevelopmental toxicity independently of direct chemical exposure remains unclear. Here, we investigated whether transplantation of PCB-associated gut microbiota produces early neurobehavioral alterations and disrupts brain molecular pathways in offspring. Gut microbiota from conventional dams exposed to the Fox River PCB mixture (FRM; 6.0 mg/kg/day) or vehicle were transplanted into germ-free recipient females without direct PCB administration. At postnatal day 7 (P7), offspring underwent ultrasonic vocalization (USV) testing, whole-brain RNA sequencing (n = 4/sex/group), and untargeted serum metabolomics. Untargeted serum metabolomics were also performed in donor dams. PCB-associated fecal microbiota transplantation (FMT) significantly reduced offspring USVs, reproducing effects observed following direct maternal PCB exposure. Brain transcriptomics in offspring identified substantially more differentially expressed genes in males (9,339) than females (1,082), including 512 shared genes. Concordantly regulated genes revealed downregulation of neurotransmitter signaling and ion channel pathways alongside upregulation of RNA processing pathways. Male-associated responses involved altered protein synthesis and neuronal signaling, whereas female-associated responses involved DNA repair and extracellular matrix remodeling. Despite these molecular differences, behavioral responses showed no significant sex-dependent effect. Maternal metabolomics revealed increased bile acids and decreased indole-3-propionic acid, highlighting potential AhR-NF{kappa}B and bile acid-associated signaling mechanisms. Offspring metabolomics further identified alterations in lipid-associated metabolites and metabolic profiles. Collectively, these findings show that transferring PCB-exposed microbiota reproduces early neurobehavioral alterations and induces shared and sex-biased molecular responses, identifying the maternal gut microbiome as a candidate mediator linking PCB exposure to developmental neurotoxicity.

pharmacology and toxicology↗

bioRxiv2026

Mathematical model of phenotypic plasticity predicts interconversion is a drug target for neuroblastoma.

Neuroblastoma is a paediatric cancer arising from the sympathetic nervous system as neural crest cells, made up of noradrenergic (NOR/ADRN/N), mesenchymal like (MES/S), and intermediate (I-type/I) cell types. These cells can interconvert between types, contributing to treatment resistance and relapse. We developed a mathematical model to investigate how interconversion patterns affect the efficacy of phenotype-specific inhibitors. We used three ordinary differential equations to describe the dynamics of the three populations, including logistic growth, interconversion, and drug-induced death. Of the 64 possible interconversion patterns, five reduced the target population: two for N cells and three for S cells. N targeting patterns were more effective with higher interconversion rates, while mesenchymal targeting patterns were more effective with lower interconversion rates. Stability analysis revealed that natural tumour growth was always unstable, but during treatment, N-suppressing patterns combined with an S inhibitor gave the most consistently stable origin. Testing multi-stage and cyclic treatment schedules revealed that N-suppressing patterns with an S inhibitor, followed by an S-suppressing pattern with an N inhibitor, achieved more reliable remission. Three of the five patterns of interest correspond to reported biological plausibility, and known compounds exist to induce most of the required transitions, supporting the clinical relevance of these strategies for improving neuroblastoma treatment outcomes.

pharmacology and toxicology↗

bioRxiv2026

Organism-dependent ecotoxicological effects of transition metal-containing layered double hydroxides

Due to low environmental stability of certain molecule classes, such as phytohormones and RNA interference, layered double hydroxides (LDHs) have been investigated as nanocarriers capable of protecting and transporting molecules of interest in natural systems. Herein, the ecotoxicological effects of LDH nanoparticles composed by different transition metals (Al-Ni, Al-Co, and Al-Cu) were evaluated in maize (Zea mays), tomato (Lycopersicum esculentum), and the nematode Caenorhabditis elegans, two important crops and one soil organism found in agricultural systems. Plants were exposed to the nanoparticles through foliar spraying (5, 50, and 500 ug/mL), and physiological parameters were evaluated. In C. elegans, lethality, locomotion, larval development, and body length were analyzed. The nanoparticles exhibited high colloidal stability and characteristic lamellar morphology. The results demonstrated low phytotoxicity for all formulations, without significant changes in photochemical activity, effective quantum yield of photosystem II (psi-PSII), stomatal conductance (gs), and chlorophyll index (Chl a+b; ICF) in plants. In contrast, C. elegans exhibited greater sensitivity, showing reduced motility, developmental delay, and decreased body length, although mortality remained below 12% under all evaluated conditions. Toxicity was dependent on the metallic composition, following the order Al-Cu > Al-Ni > Al-Co. Collectively, the results indicate that LDHs exhibit high compatibility with those two crops but may cause sublethal effects in soil organisms. These findings highlight the importance of multispecies ecotoxicological assessments for the safe development of nanocarriers intended for agricultural applications.

pharmacology and toxicology↗