Inositol 1,4,5-trisphosphate receptor determines intracellular Ca2+ concentration in Trypanosoma cruzi throughout its life cycle

Abstract

Regulation of intracellular Ca2+ concentration ([Ca2+]i) is vital for eukaryotic organisms. Recently, we identified a Ca2+ channel (TcIP3R) associated with intracellular Ca2+ stores in Trypanosoma cruzi, the parasitic protist that causes Chagas disease. In this study, we measured [Ca2+]i during the parasite life cycle and determined whether TcIP3R is involved in the observed variations. Parasites expressing R-GECO1, a red fluorescent, genetically encoded Ca2+ indicator for optical imaging that fluoresces when bound to Ca2+, were produced. Using these R-GECO1-expressing parasites to measure [Ca2+]i, we found that the [Ca2+]i in epimastigotes was significantly higher than that in trypomastigotes and lower than that in amastigotes, and we observed a positive correlation between TcIP3R mRNA expression and [Ca2+]i during the parasite life cycle both in vitro and in vivo. We also generated R-GECO1-expressing parasites with TcIP3R expression levels that were approximately 65% of wild-type (wt) levels (SKO parasites), and [Ca2+]i in the wt and SKO parasites was compared. The [Ca2+]i in SKO parasites was reduced to approximately 50–65% of that in wt parasites. These results show that TcIP3R is the determinant of [Ca2+]i in T. cruzi. Since Ca2+ signaling is vital for these parasites, TcIP3R is a promising drug target for Chagas disease.