URSOLIC ACID NEGATIVELY MODULATES THE LIPID DROPLET METABOLISM, A KEY COMPONENT OF THE ROTAVIRUS INFECTION

TOHMÉ, M. JULIETA; CONVERTI, AYELEN; CARUSO, BENJAMÍN; WILKE, NATALIA; COLOMBO, M. ISABEL; DELGUI, LAURA R.

Congreso; Congreso SAIB 2022 - Reunión anual Edición LVIII; 2022

Rotavirus (RV) is one of the leading causes of acute severe gastroenteritis, mainly affecting children under five years of age. Severe cases are associated with dehydration and can lead to the death of children. Even though there are RV vaccines available that have been demonstrated to be effective for RV immunization, the poor socioeconomic conditions and the limited access to public health, among other factors, are responsible for the lower immunization rates in low-income countries, which are also the most affected.The treatment of RV gastroenteritis is based on avoiding dehydration; this is why the study of potential anti-RV is needed. We demonstrated that ursolic acid (UA), a natural triterpenoid, exerts anti-RV effect in vitro. Then, we observed that the anti-RV effect of UA was due to the negative modulation of the lipid content in the infected cells. Lipid droplets (LDs) are ubiquitous organelles composed of a neutral lipid core, surrounded by a phospholipid monolayer associated with several proteins that play a key role in the LDs metabolism. Also, LDs are crucial organelles involved in the RV replication cycle. When infected with RV, we observed a peak of accumulation of LDs at 2 hours post-infection (h p.i.). But, the treatment with UA significantly reduced the accumulation of LDs, and the peak at 2 h p.i. did not occur. Concomitantly, the number and size of RV viroplasms (VPs) formed in UA-treated conditions were significantly lower and the viral progeny abrogated.To elucidate the mechanism of action of the UA-induced negative modulation of LDs, we approached several studies. We implemented biophysical techniques based on the formation of lipid lenses that resembled LDs, to determine the effect of UA on lens formation. Thereby, we demonstrated that UA interferes with LDs biogenesis. Also, intending to analyze LDs degradation, we observed that the treatment of the cells with UA reduced the number and size of LDs by inducing lipolysis.LDs can be degraded by two interdependent types of autophagy sequentially acting: chaperone-mediated autophagy (CMA) and macroautophagy. The CMA is responsible for degrading the proteins that surround LDs, perilipin 2 (PLIN2) and 3, and then the macroautophagy degrades the lipid content of the LDs. We demonstrated that UA favours CMA, inducing the accumulation of the phosphorylated form of PLIN2, which also losses its distribution associated with LDs. Finally, we observed that LC3 II, a key marker of macroautophagy, was significantly accumulated in UA-treated cells at 4 h p.i. and that LDs and LC3 II co-colocalized, suggesting that UA induces CMA and macroautophagy, both processes involved in LDs degradation.Altogether, our results indicate that UA negatively interferes with LDs biogenesis and favours LDs lipolysis, driving to a reduction in the number and size of LDs, crucial organelles for RV replication, then conducting to a reduction in VPs formation and finally lowering a new viral progeny production.