Acidocalcisomes and the contractile vacuole complex are involved in osmoregulation in Trypanosoma cruzi.
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.
Laboratory of Molecular Parasitology, Department of Pathobiology and Center for Zoonoses Research, University of Illinois at Urbana-Champaign, Urbana, Illinois 61802, USA.
Peter
P
Rohloff
Andrea
A
Montalvetti
Roberto
R
Docampo
D000818:Animals; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D008627:Mercuric Chloride / Q000494:pharmacology; D008854:Microscopy, Electron; D008870:Microtubules / Q000378:metabolism; D009997:Osmotic Pressure; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012835:Silver Nitrate / Q000494:pharmacology; D014349:Trypanosoma cruzi / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D014882:Water-Electrolyte Balance / Q000187:drug effects
D020346:Aquaporins; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D008627:Mercuric Chloride; D012835:Silver Nitrate; D000242:Cyclic AMP