Exploring the cellular effects of small molecule inhibitors of Oxysterol-binding Protein

Abstract

Oxysterol-binding protein (OSBP) is the founding member of a conserved protein family found among eukaryotes that functions as a lipid transporter between the ER and Golgi. OSBP is ubiquitously expressed in all tissues and is an essential host protein in the viral replication of many public health menaces, especially the Enteroviruses. Over the past decade, many broad-spectrum anti-viral small molecules have been identified as OSBP inhibitors. The anti-cancer and anti-viral natural product, OSW-1, is of interest due to its high affinity for OSBP and its ability to cause proteasomal degradation of OSBP. The work outlined in this dissertation details the unique ability of the OSW-1 compound to induce persistent OSBP repression in cells through multiple days without affecting cell viability. Even in the absence of the OSW-1 compound, the reduced OSBP levels confers a prophylactic anti-viral activity against clinical isolates of Enterovirus viruses. This long-term reduction is specific for OSBP in the proteasome, and reduction occurs through an unknown mechanism that does not involve OSBP proteolysis or transcriptional repression. Of the known OSBP small molecule inhibitors with anti-viral activity, only OSW-1 triggered the long-term repression of OSBP. The OSBP inhibitor compound T-00127-HEV2 was the only compound tested able to protect OSBP levels from the OSW-1-induced repression of the protein. Of the OSBP inhibitor compounds, only the OSW-1 compound was able to induce the prophylactic anti-viral response against two clinical isolates of Enterovirus viruses. The results produced will be beneficial in future research that seeks to define OSBP cellular regulation, especially upon OSW-1 treatment, and to potentially develop prophylactic anti-viral therapeutics through targeting OSBP.