The Minimal Machinery Required for Vesicle Fusion via SNARE Proteins in the Ancient Eukaryote Giardia lamblia.

HUGO DANIEL LUJÁN; VANINA ELIANA, ELIAS; RODRIGO QUIROGA; NATALIA GOTTIG; MARIA CAROLINA TOUZ

Virginia- Estados Unidos

Congreso; Meeting of International Research Scholars; 2006

Howard Hughes Medical Institute

Giardia is an early branching protist with unusual eukaryotic characteristics, including the absence of a morphologically evident Golgi apparatus. Although both constitutive and regulated pathways for protein secretion exist in Giardia, little is known about the molecules and mechanisms specifically involved in vesicular docking and fusion. In higher eukaryotes, soluble N-ethylmaleimide-sensitive factor-attachment protein receptor (SNARE) of the vesicle-associated membrane protein (VAMP) and Syntaxin proteins play essential roles in these processes through the formation of complexes between proteins present on donor and target membranes. In this work, we present results from a complete search of the Giardia genome for SNARE encoding genes, the analysis of the structures and subcellular localization of their products, and the functionality of the only seven SNAREs identified in this parasite. Besides, we demonstrate that expression of some of these SNAREs is regulated or their localization modified during trophozoite differentiation into cysts. We also show that Giardia SNAREs distinctively localize to different subcellular organelles and that the specificity and degree of interactions between Q-SNAREs and R-SNAREs indicate that Giardia requires a small number of SNAREs to accomplish all the vesicle docking and fusion events that are critical for growth, adaptation, differentiation, and transmission of this important human pathogen.