In Silico and Experimental Evidence for Theasaponin E2 as a Modulator of the AKT1/GSK-3β Signaling Axis in Osteoclast Differentiation

Theasaponin E2 (TE2) is a triterpenoid saponin isolated from Camellia sinensis seeds with reported anti-inflammatory, antibacterial, and antitumor activities; however, its effects on osteoclasts remain unclear. In this study, TE2 markedly inhibited RANKL-induced osteoclast differentiation in RAW264.7 cells without affecting precursor-cell viability. TE2 also significantly reduced the number and viability of mature, differentiated osteoclasts. Mechanistically, TE2 suppressed RANKL-induced phosphorylation of AKT at Ser473 and GSK-3β at Ser9, as determined by ELISA. Molecular docking predicted that TE2 could interact with the interdomain allosteric pocket of AKT1 at the pleckstrin homology–kinase domain interface (PDB ID: 7NH5; docking score, −9.8 kcal/mol) and the ATP-binding pocket of GSK-3β (PDB ID: 5K5N; docking score, −7.7 kcal/mol). The selected docking poses contained multiple hydrogen-bonding interactions with donor–acceptor distances of 2.79–3.19 Å. Collectively, these findings indicate that TE2 suppresses osteoclast differentiation and reduces mature osteoclast viability, potentially through modulation of the AKT/GSK-3β signaling axis. TE2 may therefore represent a promising natural-product candidate for further investigation in conditions characterized by excessive osteoclast-mediated bone resorption.