INIMEC - CONICET   05467
INSTITUTO DE INVESTIGACION MEDICA MERCEDES Y MARTIN FERREYRA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Secretory granule biogenesis during Giardia lamblia differentiation into cyst.
Autor/es:
MARIA CAROLINA TOUZ; GOTTIG N; ELIAS EV; QUIROGA R; SOLARI AJ; LUJAN HD
Lugar:
Wood Hole, MA. USA.
Reunión:
Congreso; Molecular Parasitology Meeting XIV. Marine Biological Laboratory.; 2006
Resumen:
The parasitic protozoan Giardia lamblia undergoes important changes to survive outside the intestine of their hosts by differentiating into infective cysts. During encystation, three cyst wall proteins (CWPs) are specifically expressed and concentrated within encystation-specific vesicles (ESVs). ESVs are electron-dense secretory granules that transport CWPs before exocytosis and extracellular polymerization into a rigid cyst wall. Since secretory granules form at the trans-Golgi in higher eukaryotes and Giardia lacks an identifiable Golgi apparatus, the aim of this work was to investigate the molecular basis of secretory granule formation in Giardia by examining the role of CWPs in this process. Although CWP1, 2 and 3 are structurally similar in their 26 kDa leucine-rich overlapping region, CWP2 is distinguished by the presence of a 13 kDa carboxy-terminal basic extension. In non-encysting trophozoites, expression of different CWP chimeras indicate that the CWP2 basic extension is necessary for biogenesis of ESVs, which occurs in a compartment derived from the endoplasmic reticulum. Nevertheless, CWP2´s basic extension per se is insufficient to trigger ESVs formation, indicating that other domains in CWPs are also required. We found CWP2 is a key regulator of ESVs formation by acting as an aggregation factor for CWP1 and CWP3 throughout interactions mediated by its conserved region. CWP2 also acts as a ligand for sorting via its C-terminal basic extension. These findings show that granule biogenesis requires complex interactions among granule components and membrane receptors.