Characterization of ADP ribosylation factors evidence an atypical golgi apparatus in Giardia lamblia

MARIANA L FERRARI; FERNANDO D RIVERO; HUGO D LUJAN

Potrero de los Funes, San Luis

Congreso; XLVII reunion anual de la Sociedad Argentina de Investigacion en Bioquimica y Biologia Molecular; 2011

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Giardia lamblia is an intestinal parasite that belongs to the earliestdiverging branch of the eukaryotic lineage of descent. Giardiaappears as a ?living fossil? since it has neither typical mitochondria,peroxisomes, nor a classical Golgi apparatus (GA). Although bothconstitutive and regulated pathways for protein secretion exist inGiardia, little is known about the molecular mechanisms involvedin vesicular traffic. An exhaustive search of the complete Giardiagenome identified genes for seven giardial ARF proteins (ADPRibosylation Factors), one RER1 (Retention in EndoplasmicReticulum 1) and one p24 (cargo receptor). The expression andlocalization of these proteins evidenced colocalization with specificmarkers for distinct subcellular organelles. Interestingly, ARF4(ORF:13930) and RER1 (ORF:15413), in addition to SNAREs Qb1and Qb2, displayed a vesicular pattern different from typical Giardiasubcompartments, and colocalized with heterologous markers forthe GA. Additionally, treatment with fungal toxin Brefeldin-Aevidenced partial dissociation from these vesicular structures andredistribution of ARF4 and RER1 into the ER. Our results not onlycontribute to understanding the complex system of vesiculartrafficking but also suggest the existence of a structurally atypicalGolgi apparatus, capable of carrying out the functions of packagingand sorting of proteins in Giardia