Identification of AIF1 as a protein target of notoginsenosides in brain tissue of mice with intracerebral hemorrhage based on hapten immunoaffinity fishing technique

Abstract

Background

Intracerebral hemorrhage (ICH) is a deadly stroke with high mortality or disability. Although recent research has demonstrated the efficacy of Panax notoginseng in ICH therapy, it is unclear which proteins may be targeted to achieve these advantages.

Methods

First, we generated polyclonal antibodies against notoginsenosides by immunizing rats with a ginsenoside Rh1-mcKLH conjugate. Second, the potential target proteins of notoginsenosides in brain tissue of ICH mice were identified using LC-MS-based hapten immunoaffinity fishing (HIAF). Third, the disease target databases and these proteins intersected. Fourth, biolayer interferometry (BLI), molecular docking, and site-directed mutagenesis were performed to validate allograft inflammatory factor 1 (AIF1) as a protein target of notoginsenosides. Last, bioinformatics analysis was performed to examine AIF1's biological characteristics.

Results

A potential protein target of notoginsenosides, AIF1, was found by intersecting the identified protein targets with the disease target databases via LC-MS-based HIAF. BLI analysis revealed that Compound K (CK) and AIF1 had the highest direct interaction, with an average shift value of 0.1091 nm. Subsequently, site-directed mutagenesis, molecular docking, and BLI kinetic analysis demonstrated that CK specifically bound to AIF1 with an affinity value of 4.33 ± 0.17E-6 M, with a significant reliance on residues L122 and E125. Bioinformatics analysis showed that AIF1 and its directly interacting proteins were associated with microglial activation.

Conclusion

Our study proposed a new technology for screening natural small molecule protein targets, and successfully identified AIF1 as a protein target of notoginsenosides, providing a chemical and biological basis for further research into targeting AIF1 to treat ICH.