Abstract 5778: Determining the structure and function relationship of the oxysterol-binding protein (OSBP) to guide drug development

Abstract

Abstract The human Oxysterol Binding Protein Structure and function relationship remains elusive, yet the anti-cancer and antiviral molecules library targeting OSBP and OSBP-Related proteins (ORPs) continues to grow. OSBP is a ubiquitously expressed protein in most eukaryotes, functioning as a master lipid sensor and cholesterol regulator in cells. OSBP and its closely related protein ORP4 are also reported to be essential in several human diseases, including viral infection and cancer cell proliferation. Our lab has shown that the natural product OSW-1 has potential anti-viral and anti-cancer activity through targeting OSBP and ORP4, as confirmed with protein-ligand interactions that showed binding with high affinity. Moreover, several anti-cancer molecules targeting the ORPs provoke different protein conformation changes and, therefore, lead to varying OSBP functions. However, the structure of full-length OSBP is still unknown, which leaves a gap in knowledge regarding the compounds’ mechanism of action or how OSBP could be established as a molecular anti-cancer target. Our goal is to determine the structure and function relationship of OSBP with emphasis on the effect of small molecule ligands on cellular OSBP levels and function. In pursuit of this research goal, we aim to determine the in vitro activity of OSW-1 analogs (OA) isolated in our lab, as well as determine their interaction with OSBP and ORP4 proteins in multiple cancer cell lines. We mainly seek to determine the structure and ligand interaction with the OSBP-ligand binding domain (LBD) and full-length OSBP to shed light on the conformation changes that occur upon ligand binding. Preliminary data indicate that the tested OA compounds are active in multiple cancer cell lines with reduced OSBP levels effect, suggesting a similar mechanism of action to OSW-1. A transient expression of full-length OSBP and LBD showed that the truncated OSBP (LBD) was mostly found in the pellet, which could imply low solubility, while the full-length OSBP showed sufficient solubility. Our efforts are currently focused on purifying full-length OSBP. We are also working towards purifying full-length OSBP with a cleavage site that allows cutting out the LBD, thus solving the insolubility issue. Once obtained, the full-length OSBP and the ligand binding domain will be used for both binding and structure determination studies. Citation Format: Ruth Fiona Bayimenye, Jorge L. Berrios-Rivera, Susan Nimmo, Christina R. Bourne, Anthony W. Burgett. Determining the structure and function relationship of the oxysterol-binding protein (OSBP) to guide drug development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5778.