Persistent, Multi-Generational Reduction of Oxysterol-Binding Protein Caused by Compound Treatment Induces Prophylactic Anti-Viral Activity.

Oxysterol-binding protein (OSBP) is a lipid transport and regulatory protein required for the replication of Enterovirus genus viruses, which includes many significant human pathogens. Short-term exposure (i.e., 1-6 hours) to a low dose (i.e., 1 nM) of the natural product compound OSW-1 induces a reduction of cellular OSBP levels by ~90% in multiple different cell lines with no measurable cytotoxicity, defect in cellular proliferation, or global proteome reduction. Interestingly, the reduction of OSBP levels persists multiple days after the low-dose, transient OSW-1-compound treatment is ended and the intracellular OSW-1-compound levels drop to undetectable levels. The reduction in OSBP levels is inherited in multiple generations of cells that are propagated after the OSW-1-compound treated is stopped. The enduring multi-day, multi-generational reduction of OSBP levels triggered by the OSW-1-compound is not due to proteasome degradation of OSBP or due to a reduction in OSBP mRNA levels. OSW-1-compound treatment induces transient autophagy in cells, but blocking autophagy does not rescue OSBP levels. Although the specific cellular mechanism of long-term OSBP repression is not yet identified, these results clearly show the existence of an OSBP specific cellular regulation process that triggered upon treatment with an OSBP-binding compound. The stable reduction of OSBP levels upon short-term, transient OSW-1-compound treatment will be a powerful tool to understand OSBP regulation and cellular function. Additionally, the persistent reduction in OSBP levels triggered by the transient OSW-1-compound treatment substantially reduces viral replication in treated cells. Therefore, the long-term, compound-induced reduction of OSBP in cells presents a new route to broad spectrum anti-Enterovirus activity, including as a novel route to anti-viral prophylactic treatment through small molecule targeting a human host protein.