Sorting role of the perinuclear region and ER in Giardia lamblia.

ZAMPONI N; FELIZIANI C; MIRAS S; LANFREDI-RANGEL; TOUZ MC

Congreso; SAIB; 2012

The unicellular parasite Giardia lamblia belongs to the Diplomonads, a group which belongs to the earliest branches in eukaryotic evolution. One of the most striking characteristics of Giardia is the presence of protein sorting even though it lacks a morphological discernible Golgi apparatus. By using bodipy FLC5- ceramide, a marker for Golgi apparatus, we showed that the membrane network comprised by the nuclear envelope and the endoplasmic reticulum (ER) possesses Golgi characteristics in both growing and encysting trophozoites. DAB photooxidation-coupled MET showed that ceramide accumulates specifically at the perinuclear region of the cell, a very dynamic zone, sensitive to brefeldin A treatment and to low temperature exposure. During encystation, there was a remarkable change in the endomembrane system, with ceramide progressively accumulating at the nuclear membrane and ER exit-sites (ERES), from which we observed that secretory granules are formed de novo. This accumulation at the ERES was found also to be sensitive to brefeldinAtreatment, which causes the reabsorption of the secretion material back to the ER, although some fully formed vesicles remained, and were entirely separated from the ER. Altogether, these results suggest that the perinuclear region and ER play an important role in protein and membrane sorting in this unique eukaryotic cell.