Reversible and site-specific immobilization of β2-adrenergic receptor by aptamer-directed method for receptor-drug interaction analysis

Can the heptapeptide ASSIVSF of the β2-adrenoceptor recognize ephedrine and pseudoephedrine epimers in a complex system?

Epimer separation is crucial in the field of analytical chemistry, separation science, and the pharmaceutical industry. No reported methods could separate simultaneously epimers or even isomers and remove other unwanted, co-existing, interfering substances from complex systems like herbal extracts. Herein, we prepared a heptapeptide-modified stationary phase for the separation of 1R,2S-(-)-ephedrine [(-)-Ephe] and 1S,2S-(+)-pseudoephedrine [(+)-Pse] epimers from Ephedra sinica Stapf extract and blood samples. The heptapeptide stationary phase was comprehensively characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The separation efficiency of the heptapeptide column was compared with an affinity column packed with full-length β2-AR functionalized silica gel (β2-AR column). The binding affinity of the heptapeptide with (+)-Pse was 3-fold greater than that with (-)-Ephe. Their binding mechanisms were extensively characterized by chromatographic analysis, ultraviolet spectra, circular dichroism analysis, isothermal titration calorimetry, and molecule docking. An enhanced hydrogen bonding was clearly observed in the heptapeptide-(+)-Pse complex. Such results demonstrated that the heptapeptide can recognize (+)-Pse and (-)-Ephe epimers in a complex system. This work, we believe, was the first report to simultaneously separate epimers and remove non-specific interfering substances from complex samples. The method was potentially applicable to more challenging sample separation, such as chiral separation from complex systems.

Advances in receptor chromatography for drug discovery and drug-receptor interaction studies

Receptor chromatography involves high-throughput separation and accurate drug screening based on specific drug-receptor recognition and affinity, which has been widely used to screen active compounds in complex samples. This review summarizes the immobilization methods for receptors from three aspects: random covalent immobilization methods, site-specific covalent immobilization methods and dual-target receptor chromatography. Meanwhile, it focuses on its applications from three angles: screening active compounds in natural products, in natural-product-derived DNA-encoded compound libraries and drug-receptor interactions. This review provides new insights for the design and application of receptor chromatography, high-throughput and accurate drug screening, drug-receptor interactions and more. Teaser: This review summarizes the immobilization methods of receptors and the application of receptor chromatography, which will provide new insights for the design and application of receptor chromatography, rapid drug screening, drug-receptor interactions and more.

Preparation and characterization of immobilized 5-HT1A receptor stationary phase for high throughput screening of the receptor-binding ligands from complex systems like Curcuma wenyujin Y. H. Chen et C. Ling extract

The incidence of depression has increased significantly during the COVID-19 pandemic. This disease is closely associated with serotonin _1A (5-HT_1A) receptor and often treated by complex prescription containing Curcuma wenyujin Y. H. Chen et C. Ling. Therefore, we hypothesized that this herb contains bioactive compounds specially binding to the receptor. However, the rapid discovery of new ligands of 5-HT_1A receptor is still challenging due to the lack of efficient screening methods. To address this problem, we developed and characterized a novel approach for the rapid screening of ligands by using immobilized 5-HT_1A receptor as the chromatographic stationary phase. Briefly, haloalkane dehalogenase was fused at the C-terminal of 5-HT_1A receptor, and the modified 5-HT_1A receptor was immobilized on amino-microspheres by the reaction between haloalkane dehalogenase and 6-chlorohexanoic acid linker. Scanning electron microscope and X-ray photo-electron were used to characterize the morphology and element of the immobilized receptor. The binding of three specific ligands to 5-HT_1A receptor was investigated by two different methods. Moreover, we examined the feasibility of 5-HT_1A receptor colume in high throughput screening of new ligands from complex systems as exemplified by Curcuma wenyujin Y. H. Chen et C. Ling. Gweicurculactone, 2-hydroxy-1-(3,4-dihydroxybenzene)-7-(4′-hydroxybezene)-heptane and curcuminol F were identified as the ligands of 5-HT_1A receptor with the binding energies of −7.06 kcal/mol, −7.77 kcal/mol and −5.26 kcal/mol, respectively. Collectively, these results indicated that the immobilized 5-HT_1A receptor was capable of screening bioactive compound from complex system, providing an effective methodology for high throughput screening.

Immobilization of peroxisome proliferator-activated receptor gamma and the application in screening modulators of the receptor from herbal medicine

Screening and identification of potential compounds from herbal medicine is a prevailing way to find a lead for the development of innovative drugs. This promotes the development of new methods that are feasible in complex matrices. Here, we described a one-step reversible methodology to immobilize nuclear peroxisome proliferator-activated receptor gamma (PPARγ) onto amino microsphere coated with a DNA strand specifically binding to the receptor. The specific interaction allowed us to achieve the immobilization of PPARγ by mixing the DNA modified microspheres with E. coli lysates expressing the receptor. Characterization of the immobilized receptor was carried out by morphology and binding specificity analysis. Feasibility of immobilized PPARγ in the drug-receptor interaction analysis was performed by an injection amount-dependent method. Besides, immobilized PPARγ was also applied in screening modulators of the receptor from Coptidis Rhizoma extract. The binding of the screened compounds to PPARγ was examined by time-resolved fluorescence resonance energy transfer assay. The results showed that immobilized PPARγ was stable for thirty days with a high-specificity of ligand recognition at the subtype receptor level. Berberine and palmatine were the bioactive compounds of Coptidis Rhizoma specifically binding to PPARγ. The two compounds exhibited half maximal inhibitory concentrations of 4.11 and 2.98 μM during their binding to the receptor. We concluded that the current method is possible to become a common strategy for the immobilization of nuclear receptors, and the immobilized receptor is a high throughput method for recognizing and separating the receptor modulators from complex matrices including herbal medicine.

Two-point immobilization of a conformation-specific beta2-adrenoceptor for recognizing the receptor agonists or antagonists inspired by binding-induced DNA assembly

Immobilized protein has advanced in many areas like drug discovery. While this field evolved rapidly over the last three decades, the immobilization platform for the G-protein-coupled receptor (GPCR) remains unpromising due to its instability under the relatively harsh conditions of current methodologies. Taking beta₂-adrenoceptor (β₂-AR) as an example, we presented here a general strategy for immobilization of GPCRs by combining the His₆-tag trap system, conformation-specific aptamer, and target binding induced DNA hybridization. Morphology characterization by diverse assays confirmed a monolayer of β₂-AR on the microsphere surface. The radio-ligand binding assay and immuno-transmission electron microscopy showed desirable ligand- and antibody-binding activities. A case study of chromatography using the immobilized receptor as a stationary phase exhibited a demonstrable conformation specificity that enables the selective recognition of the receptor agonists or antagonists. Owing to the competitive strand displacement during the immobilization, the method proved to be capable of sensitively and directly determining the receptor density on the surface which enormously challenges most of the reported assays. This method is possible to turn into a general strategy for the immobilization of GPCRs with a defined orientation, conformation, function, and density, thus paving the way for precisely realizing the receptor-ligand binding interaction and screening the receptor agonist or antagonist with high efficiency.