A trypanosoma cruzi phosphatidylinositol 3-kinase (TcVps34) is involved in osmoregulation and receptor-mediated endocytosis

SCHOIJET, A.C.; MIRANDA, K.; GIRARD-DIAS W.; DE SOUZA, W.; FLAWIÁ, M.M.; TORRES, H.N.; DOCAMPO, R.; ALONSO, G.D.

JOURNAL OF BIOLOGICAL CHEMISTRY

The American Society for Biochemistry and Molecular Biology

Lugar: Rockville Pike Bethesda; Año: 2008 vol. 14 p. 31541 - 31550

0021-9258

Trypanosoma cruzi, the etiological agent of Chagas disease,has the ability to respond to a variety of environmental changesduring its life cycle both in the insect vector and in the vertebratehost. Because regulation of transcription initiation seems to benonfunctional in this parasite, it is important to investigateother regulatory mechanisms of adaptation. Regulatory mechanismsat the level of signal transduction pathways involvingphosphoinositides are good candidates for this purpose. Herewe report the identification of the first phosphatidylinositol3-kinase (PI3K) in T. cruzi, with similarity with its yeast counterpart,Vps34p. TcVps34 specifically phosphorylates phosphatidylinositolto produce phosphatidylinositol 3-phosphate, thusconfirming that it belongs to class III PI3K family. Overexpressionof TcVps34 resulted in morphological and functional alterationsrelated to vesicular trafficking. Although inhibition ofTcVps34 with specific PI3K inhibitors, such as wortmannin andLY294,000, resulted in reduced regulatory volume decreaseafter hyposmotic stress, cells overexpressing this enzyme wereresistant to these inhibitors. Furthermore, these cells were ableto recover their original volume faster than wild type cells when they were submitted to severe hyposmotic stress. In addition, inTcVps34-overexpressing cells, the activities of vacuolar-H-ATPase and vacuolar H-pyrophosphatase were altered, suggestingdefects in the acidification of intracellular compartments.Furthermore, receptor-mediated endocytosis waspartially blocked although fluid phase endocytosis was notaffected, confirming a function for TcVps34 in membrane trafficking.Taken together, these results strongly support thatTcVps34 plays a prominent role in vital processes for T. cruzisurvival such as osmoregulation, acidification, and vesiculartrafficking.