Secretory granule biogenesis during Giardia lamblia differentiation into cyst

NATALIA GOTTIG; MARIA JIMENA NORES; VANINA ELIAS; ALBERTO SOLARI; MARIA CAROLINA TOUZ; HUGO DANIEL LUJAN

Mendoza - Argentina

Conferencia; VII Congreso Argentino de Protozoología y Enfermedades Parasitarias; 2005

Sociedad Argentina de Protozoología

Giardia is an intestinal parasitic protozoan of humans. Trophozoites undergo fundamental changes to survive outside the intestine by differentiating into cysts. Encystation entails the synthesis, processing, transport, secretion and assembly of cyst wall components. Among those molecules are three closely related  proteins  that localize within encystation-specific secretory vesicles (ESVs) in encysting trophozoites and in the cyst wall of mature cysts. The CWP genes predict proteins of 26 (CWP1), 39 (CWP2), and 27 (CWP3) kDa, having 61% identity in a 26 kDa overlapping region. CWP2 differs from CWP1 and CWP3 by a 121-residue carboxy-terminal extension rich in basic amino acids. In this work we determined the role of the alkaline extension of CWP2. CWP constructs with or without the CWP2 basic tail were transfected into trophozoites and two types mammalian cells, those with and without endogenous secretory granules.Our results indicate that the CWP2  basic tail is necessary but not sufficient to induce the biogenesis of ESVs in non-encysting trophozoites and that there must exist a receptor for this tail in Giardia .These results provide new insights into the minimal machinery for protein trafficking utilized by Giardia during differentiation into cyst.