Comparative in silico analysis of CHIR99021, Azakenpaullone and Tricantin interactions with GSK3β, a key protein in stem cell fates

Glycogen Synthase Kinase 3β (GSK3β) is a multifunctional serine/threonine-protein kinase that serves as a pivotal regulator of various human pluripotent stem cell (hPSCs) functions, including self-renewal, adhesion, survival, and differentiation in addition to have an effect on motility of sperm. Despite advancement in understanding the critical roles of GSK3β inhibition in various stem cell functions, the exact molecular basis of its inactivation using various small-molecule inhibitors remains poorly understood. Investigating the mechanistic details of the actions of inhibitors targeting GSK3 proteins, such as CHIR99021, Azakenpaullone, and Tricantin, could be extremely beneficial for improving novel defined stem cell culture systems and cancer research. The present study aimed to predict the binding mode of the aforementioned ligands with GSK3β, by molecular docking and metadynamic simulation, and compare the three-dimensional structure of the inactive conformation of GSK3β in the presence of three inhibitors. Also, the pharmacokinetic or ADMET properties of ligands, such as Lipinski's rule of five violations for drug-likeness, QPlog S, QPlog K, and bioactivity scoring, were predicted. The analysis of protein stability revealed that in the absence of inhibitors, the GSK3β has higher flexibility, while in the presence of CHIR and AZA, the rate of flexibility of most protein regions, especially the envelope area, decreased. It was found that though all small molecules are capable of facilitating the inhibition of GSK3β protein, but the flexibility of protein is a bit higher for CHIR than those for other two ligands.