The minimal machinery required for vesicle fusion via SNARE proteins in the ancient eukaryote Giardia lamblia.

GOTTIG N; ELÍAS VE; QUIROGA R; TOUZ MC; LUJÁN HD

Ashburn, Virginia, USA

Conferencia; Howard Hughes Medical Institute Meeting of International Research Scholars; 2006

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 moleculres and mechanisms specifically involved in vesicular docking and fusion. In higher eukaryotes, the soluble N-ehthylmaleimide-sensitive factor attachment protein receptors (SNARE) of the vesicle-associated membrane protein (VAMP) and syntaxin proteins play essential roles in the processes through the formation of complexes between proteins present on donor and target membranes. We present results from a search of the Giardia genome for SNARE-enconding genes, the analysis of the subcellular localization of their products, and the functionality of the mere seven SNAREs identified in this parasite. We also demonstrate that expression of some of these SNAREs is regulated or their localization modified during encystation. We also show that Giardia SNAREs distinctively localize to different subcellular organelles. The specificity and degreee of interaction 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.