Affinity Chromatography: A Powerful Tool in Drug Discovery for Investigating Ligand/membrane Protein Interactions

Immobilized cells on microcarriers for efficient and biomimetic screening of active compounds acting on FGFR4 from Fructus evodiae

Cell membrane coating strategies have been increasingly researched in new drug discovery from complex herb extracts. However, these systems failed to maintain the functionality of the coated cells because cell membranes, not whole cells were used. Original source cells can be used as a vector for active compound screening in a manner that mimics in vivo processes. In this study, we established a novel approach to fabricate high-density fibroblast growth factor receptor 4 (FGFR4)-HEK293 cells on microcarriers covered with collagen through cell culture and covalent immobilization between proteins. This method enables the efficient screening of active compounds from herbs. Two compounds, evodiamine and limonin, were obtained from Fructus evodiae, which were proven to inhibit the FGFR4 target. Enhanced immobilization effects and negligible damage to FGFR4-HEK293 cells treated with paraformaldehyde were successfully confirmed by immunofluorescence assays and transmission electron microscopy. A column was prepared and used to analyze different compounds. The results showed that the method was selective, specific, and reproducible. Overall, the high density of cells immobilized on microcarriers achieved through cell culture and covalent immobilization represents a promising strategy for affinity screening. This approach highlights the potential of the affinity screening method to identify active compounds from an herbal matrix against designed targets and its prospects for use in drug discovery from herbs.

Ligand Screening of Membrane Proteins Embedded in Nanodiscs: How to Manage Non-Specific Interactions in Weak Affinity Chromatography?

Miniaturized weak affinity chromatography is emerging as an interesting alternative to conventional biophysical tools for performing fragment-screening studies in the context of fragment-based drug discovery. In order to push back the analytical limits, it is necessary not only to control non-specific interactions with chromatographic support, but also to adapt this methodology by comparing the results obtained on an affinity column to a control column. The work presented in this study focused on fragment screening that targets a model membrane protein, the adenosine A2A receptor, embedded in nanodiscs (NDs) as biomimetic membranes. By studying the retention behavior of test fragment mixtures on supports modified with different types of NDs, we were able to determine the contribution of ND-related non-specific interactions, in particular the electrostatic effect of anionic phospholipids and the hydrophobic effect of neutral phospholipids. Different strategies for the preparation of control columns (empty NDs, orthosteric site blocking) were investigated and are presented for the first time. With these two types of control columns, the screening enabled the identification of two new fragments of AA2AR, which were confirmed by competition experiments and whose Kd values, estimated directly during the screening or after the competition experiments in frontal mode, were in good agreement.

Facile Capture of Recombinant Human Erythropoietin on Mesoporous Affinity Hydrogel Matrix Functionalized with Azoboronate

Boronate affinity ligands (BALs) have gained attention for glycoproteins capture and recognition due to their unique affinity interaction with glycans. In this paper, the effect of azo immobilization of phenylboronic acid on the reduction of adsorption pH of a recombinant glycoprotein (i.e., rhEPO) on hydrogel microparticles was investigated. To evaluate the influence of intraparticle porosity on protein adsorption, microporous (MicroBead) and mesoporous (MesoBead) agarose beads carrying two levels of amine densities were functionalized with azoboronate ligand. Affinity adsorption of the glycoprotein during static and dynamic adsorptions at relatively low pHs of 8 and 7 was studied. Results revealed successful adsorption of rhEPO at pH = 8 through affinity capture of glycans by azoboronate ligands. Increased amine density provided 1.1 and 1.5 times higher static adsorption capacities and dynamic performance efficiencies, respectively. In addition, adsorption capacities and initial adsorption rates of rhEPO on MesoBeads were respectively 1.4 and 2.5-2.8 times of MicroBeads. Also, at pH = 8, MesoBeads recorded higher dynamic recoveries (59 and 91%) compared with microporous ones (46 and 69%) since mesoporosity facilitates intraparticle mass transfer. Reduction of binding pH from 8 to 7 resulted in a sharp decrease in dynamic recovery (14%), indicating the appropriate binding pH of azoPBA to be above 7. The azoboronate affinity ligand is a leading candidate for capturing glycoproteins at relatively low pH. Also, mesoporous microparticles are appropriate tools in more efficient medium-sized protein binding applications.