Effect of ionizing radiation exposure on Trypanosoma cruzi ubiquitin-proteasome system.

Abstract

tIn recent years, proteasome involvement in the damage response induced by ionizing radiation (IR)became evident. However, whether proteasome plays a direct or indirect role in IR-induced damageresponse still unclear. Trypanosoma cruzi is a human parasite capable of remarkable high tolerance toIR, suggesting a highly efficient damage response system. Here, we investigate the role of T. cruzi pro-teasome in the damage response induced by IR. We exposed epimastigotes to high doses of gamma rayand we analyzed the expression and subcellular localization of several components of the ubiquitin-proteasome system. We show that proteasome inhibition increases IR-induced cell growth arrest andproteasome-mediated proteolysis is altered after parasite exposure. We observed nuclear accumulationof 19S and 20S proteasome subunits in response to IR treatments. Intriguingly, the dynamic of 19S par-ticle nuclear accumulation was more similar to the dynamic observed for Rad51 nuclear translocationthan the observed for 20S. In the other hand, 20S increase and nuclear translocation could be relatedwith an increase of its regulator PA26 and high levels of proteasome-mediated proteolysis in vitro. Theintersection between the opposed peaks of 19S and 20S protein levels was marked by nuclear accumu-lation of both 20S and 19S together with Ubiquitin, suggesting a role of ubiquitin-proteasome system inthe nuclear protein turnover at the time. Our results revealed the importance of proteasome-mediatedproteolysis in T. cruzi IR-induced damage response suggesting that proteasome is also involved in T. cruziIR tolerance. Moreover, our data support the possible direct/signaling role of 19S in DNA damage repair.Based on these results, we speculate that spatial and temporal differences between the 19S particle and20S proteasome controls proteasome multiple roles in IR damage response.