Acidocalcisomes and the Contractile Vacuole Complex Are Involved in Osmoregulation in Trypanosoma cruzi

Abstract

Trypanosoma cruzi, the etiologic agent of Chagas disease, resists extreme fluctuations in osmolarity during its life cycle. T. cruzi possesses a robust regulatory volume decrease mechanism that completely reverses cell swelling when submitted to hypo-osmotic stress. The efflux of amino acids and K ؉ release could account for only part for this volume reversal. In this work we demonstrate that swelling of acidocalcisomes mediated by an aquaporin and microtubule-and cyclic AMP-mediated fusion of acidocalcisomes to the contractile vacuole complex with translocation of this aquaporin and the resulting water movement are responsible for the volume reversal not accounted for by efflux of osmolytes. Contractile vacuole bladders were isolated by subcellular fractionation in iodixanol gradients, showed a high concentration of basic amino acids and inorganic phosphate, and were able to transport protons in the presence of ATP or pyrophosphate. Taken together, these results strongly support a role for acidocalcisomes and the contractile vacuole complex in osmoregulation and identify a functional role for aquaporin in protozoal osmoregulation.

Rab32 is essential for maintaining functional acidocalcisomes, and for growth and infectivity of Trypanosoma cruzi

“…2B) or hyperosmotic ( Fig. 2C) conditions, we observed that staining of VP1 overlapped with that of GFP at the CVC region, in agreement with the previously reported fusion of these organelles under osmotic stress Rohloff et al, 2004). The lack of colocalization between GFP-TcRab32 and the acidocalcisome marker under isosmotic conditions could be attributed to the dynamic nature of the interaction between these two organelles.…”

Hyperosmotic Stress Induces Aquaporin-dependent Cell Shrinkage, Polyphosphate Synthesis, Amino Acid Accumulation, and Global Gene Expression Changes in Trypanosoma cruzi

“…Hyperosmotic stress also resulted in a great increase in the size of the contractile vacuole. In previous work, we demonstrated that the TcAQP1 localized to the contractile vacuole was involved in the regulatory volume decrease after hyposmotic stress (36). Our present results suggest that TcAQP1 and the contractile vacuole are also involved in water efflux during hyperosmotic stress.…”

A Solanesyl-diphosphate Synthase Localizes in Glycosomes of Trypanosoma cruzi

“…Fluorescence Microscopy-For co-localization with a glycosomal marker, T. cruzi Y strain epimastigotes slides were prepared as previously described (35). Antibody concentrations were as follows: affinity-purified rabbit anti-TcSPPS antibody at 1:4,000; supernatant from an anti-TbPPDK producing mouse hybridoma culture at 1:10; anti-mouse Alexa 488 at 1:1,000; anti-rabbit Alexa 546 at 1:1,000.…”