Characterization of the complete set of SNARES in the Golgi-lacking eukaryote Giardia lamblia.

ELÍAS EV; QUIROGA R; GOTTIG N; LUJÁN HD

Córdoba, Argentina.

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB).; 2008

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB).

Giardia is an eukaryotic protozoan with unusual characteristics, such as 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 involved in vesicular docking and fusion. In higher eukaryotes, soluble N-ethylmaleimide-sensitive factor-attachment protein receptors (SNAREs) of the vesicle-associated membrane protein (VAMP) and Syntaxin families play essential roles in these processes. An exhaustive search of the complete Giardia genome identified genes for 17 SNARE proteins, some of which possess atypical amino acids at the zero layer of the SNARE domain. The expression and localization of all SNAREs demonstrate that specific SNAREs localize to distinct subcellular organelles. Our results suggest that these compartments represent the extent of the endomembrane system in eukaryotes. Comparison of Giardia SNAREs homologous to Golgi SNAREs from other organisms does not allow the detection of a typical Golgi apparatus in trophozoites. Moreover, depletion of individual genes demonstrated that several SNAREs are essential for viability. Thus, Giardia requires a smaller number of SNAREs, compared to other eukaryotes, to accomplish all the vesicle trafficking events that are critical for growth and differentiation of this important human pathogen.