Osmoregulation and endocytic signaling in Trypanosoma cruzi

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

Villa Carlos Paz. Cordoba, Argentina.

Congreso; XLIV Reunión Anual de SAIB; 2008

SAIB

  Trypanosoma cruzi, the etiological agent of Chagas’ disease, has a regulatory volume decrease (RVD) mechanism which reverses cell swelling under hyposmotic stress and allows it to respond to several environmental changes. 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 localizes in the spongiome around the contractile vacuole in 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 characterized TcVps34, the first class III PI 3-kinase from T. cruzi. TcVps34 overexpressing cells showed enlarged contractile vacuoles and defects in the region of the flagellar pocket. Furthermore, these cells were more resistant to severe hyposmotic stress than wild type cells. In addition, TcVps34 overexpressing parasites showed alterations in vesicular acidification and receptor-mediated endocytosis. Finally, TcVps34 interacts with TcVps15, a Ser-Thr protein kinase that regulates Vps34 in yeast, suggesting the presence of a complex between these proteins.