Identification of the ZU5 domain in UNC5C as a potential receptor for Schisandrin A: experimental and computational insights.

Despite numerous reports on Schisandrin A's potential clinical and pharmacological mechanisms, comprehensive screening is still urgently needed. In this study, we screened 39 potential in vivo receptors of Schisandrin A using Phage Display Peptide Library combined with Basic Local Alignment Search Tool. And we further investigated the binding mechanism of Schisandrin A with the candidate ZU5 domain in netrin receptor UNC5C isoform X1 (ZU5) by Fluorescence Spectroscopy, Isothermal Titration Calorimetry, and Molecular Dynamics Simulation. The results showed that Schisandrin A spontaneously bound with equimolar ZU5 driven by the enthalpy change, with van der Waals force and hydrogen bond as the main forces. The obvious fluctuations of loops and the transformation of one random coil into an α-helix in the ZU5 evidenced the binding following the induced-fit theory. Leu61 and Leu96 of ZU5 participated in multiple types of interaction forces and contributed the greatest energy, indicating their key roles in binding Schisandrin A. Moreover, the biphenyl rings and the methoxy group of Schisandrin A might play essential roles for its receptor recognition and the physiological effects, ascribing to their deep participation in the binding with ZU5. In short, this work not only screened out 39 potential in vivo receptors of Schisandrin A, verified ZU5 as one candidate, but also provided valuable information on the detailed binding progress in the experimental and computational aspects, facilitating the mechanism research in the treatment of neurodegenerative disease and structure modification research for Schisandrin A that may help its clinical application.