BPS2026 – Co-stimulation of TREM2 with cooperative ligands counteracts lost activities caused by Alzheimer’s disease-associated variants

Alzheimer’s disease (AD) is the leading cause of dementia with multiple genetic risk factors including triggering receptor expressed on myeloid cells 2 (TREM2) and apolipoprotein E (apoE). TREM2 has three primary binding surfaces—basic site, hydrophobic site, and multimerization site. The multimerization site can interact with other TREM2 subunits to form homo-multimers, and AD-associated disease variants in TREM2 can reduce multimerization. TREM2’s basic and hydrophobic sites can act as binding interfaces for ligands, with the potential for ligands being able to individually bind TREM2’s basic and hydrophobic sites to have cooperative effects on TREM2-dependent activities. Further, apoE is a known TREM2 ligand that interacts with TREM2’s hydrophobic site, and AD-associated TREM2 variants reduce TREM2-apoE interactions. In this study, we implemented combined computational, biophysical, and cellular experiments to identify ligands capable of co-stimulating TREM2, including regulating TREM2-apoE binding. We first implemented computational predictions to identify potential ligands capable of binding TREM2 and regulating how other ligands may interact with TREM2, including apoE. We then validated these ligands could regulate TREM2-apoE interactions with bio-layer interferometry (BLI) experiments. Additionally, cellular experiments were implemented to determine whether co-stimulation of TREM2 with ligands targeting the hydrophobic and basic sites could cooperatively regulate TREM2-mediated cellular functions. Here, we were able to identify a ligand capable of upregulating apoE binding with common variant TREM2 and a second ligand that inhibited apoE interactions in common variant TREM2; however, both ligands upregulated TREM2-apoE interactions in TREM2 R47H variant. We additionally identified a pair of ligands that bind to the basic and hydrophobic sites on TREM2 and cooperatively regulate TREM2 signaling and counteract lost TREM2 multimerization caused by TREM2 AD-associated variants. Acknowledgements: this work was supported by the NIH (R01AG068395, R01AG081228, and T32EB023872).