Signal transduction pathways in Trypanosoma cruzi, proteins involved in osmoregulation and endocytosis processes.

SCHOIJET, AC; DOCAMPO R; MIRANDA K; DE SOUZA W; TORRES HN; FLAWIÁ MM; ALONSO GD

Rosario. Santa Fe, Argentina.

Congreso; VIII Congreso Argentino de Protozoologia y Enfermedades Parasitarias.; 2008

Trypanosoma cruzi, the etiological agent of Chagas’ disease, has to respond to a variety of environmental changes during its life cycle. This parasite has been shown to possess a robust regulatory volume decrease (RVD) mechanism that reverses cell swelling under hyposmotic stress, which involves the efflux of aminoacids and inorganic ions plus the release of water by the contractile vacuole complex. Here we report the contribution of TcrPDEC2, a cAMP phosphodiesterase and TcVps34, a phosphatidylinositol 3-kinase to osmoregulation and membrane trafficking in T. cruzi. Inhibitors of TcrPDEC2 induced an increase in RVD in wild type cells exposed to hyposmotic stress. In addition, TcrPDEC2 it’s localized in the spongiome around the contractile vacuole of T. cruzi epimastigote cells, supporting its role in osmoregulation. Since TcrPDEC2 possesses a FYVE domain able to bind to phosphatidylinositol 3-phosphate (PI 3-P), we hypothesized that PI 3-P production might also have a role in osmoregulation. Consequently we functional characterize TcVps34, the first class III PI 3-kinase from T. cruzi. TcVps34 overexpressing cells showed enlarged contractile vacuoles and defects in the flagellar pocket and the citostome. Furthermore, these cells were more resistant to severe hiposmotic stress than wild type cells. In addition, TcVps34 overexpressing cells showed defects in vesicular acidification and receptor-mediated endocytosis. Finally, we demonstrated that TcVps34 interacts with TcVps15, a serin-theronine protein kinase that regulates Vps34 in yeast, suggesting the presence of an associated complex between these proteins.