Calcium signaling in trypanosomatid parasites

Abstract

Calcium ion (Ca2+) is an important second messenger in trypanosomatids and essential for their survival although prolonged high intracellular Ca2+ levels lead to cell death. As other eukaryotic cells, trypanosomes use two sources of Ca2+ for generating signals: Ca2+ release from intracellular stores and Ca2+ entry across the plasma membrane. Ca2+ release from intracellular stores is controlled by the inositol 1,4,5-trisphosphate receptor (IP3R) that is located in acidocalcisomes, acidic organelles that are the primary Ca2+ reservoir in these cells. A plasma membrane Ca2+-ATPase controls the cytosolic Ca2+ levels and a number of pumps and exchangers are responsible for Ca2+ uptake and release from intracellular compartments. The trypanosomatid genomes contain a wide variety of signaling and regulatory proteins that bind Ca2+ as well as many Ca2+-binding proteins that await further characterization. The mitochondrial Ca2+ transporters of trypanosomatids have an important role in the regulation of cell bioenergetics and flagellar Ca2+ appears to have roles in sensing the environment. In trypanosomatids in which an intracellular life cycle is present, Ca2+ signaling is important for host cell invasion.