IP 3 receptor-mediated Ca 2+ release from acidocalcisomes regulates mitochondrial bioenergetics and prevents autophagy in Trypanosoma cruzi.

In contrast to animal cells, the inositol 1,4,5-trisphosphate receptor of Trypanosoma cruzi (TcIP ₃ R) localizes to acidocalcisomes instead of the endoplasmic reticulum. Here, we present evidence that TcIP ₃ R is a Ca ²⁺ release channel gated by IP ₃ when expressed in DT40 cells knockout for all vertebrate IP ₃ receptors, and is required for Ca ²⁺ uptake by T. cruzi mitochondria, regulating pyruvate dehydrogenase dephosphorylation and mitochondrial O ₂ consumption, and preventing autophagy. Localization studies revealed its co-localization with an acidocalcisome marker in all life cycle stages of the parasite. Ablation of TcIP ₃ R by CRISPR/Cas9 genome editing caused: a) a reduction in O ₂ consumption rate and citrate synthase activity; b) decreased mitochondrial Ca ²⁺ transport without affecting the membrane potential; c) increased ammonia production and AMP/ATP ratio; d) stimulation of autophagosome formation, and e) marked defects in growth of culture forms (epimastigotes) and invasion of host cells by infective stages (trypomastigotes). Moreover, TcIP ₃ R overexpressing parasites showed decreased metacyclogenesis, trypomastigote host cell invasion and intracellular amastigote replication. In conclusion, the results suggest a modulatory activity of TcIP ₃ R-mediated acidocalcisome Ca ²⁺ release on cell bioenergetics in T. cruzi.
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