Giardia lamblia and Retromer: two evolutionary ancestors.

TOUZ, M.C., ; RIVERO, M.R.; ZAMPONI N.; RÓPOLO, A.S.; MIRAS S.L

Ascochinga, Córdoba

Congreso; XXIV Reunión Anual de la Sociedad Argentina de Protozoología; 2010

Giardia is a flagellated protozoan parasite that resides in the upper small intestine of several vertebrate hosts, including humans, and is one of the most frequent causes of defined waterborne diarrhea worldwide. Giardia trophozoites lack the organelles that are involved in intracellular protein trafficking and secretion in most types of eukaryotic cells, such as the Golgi apparatus. Giardia also lacks a typical endosomal/lysosomal system. Instead, it possesses peripheral vacuoles (PVs), located underneath the plasma membrane of the trophozoites, which function as both endosomes and lysosomes.These vacuoles play a central role controlling the degradation, recycling, and secretion of proteins during growth and differentiation of the parasite. To accomplish their functions, lysosomal hydrolases must be succesfully delivered to the PV compartment. Crucial to maintaining the forward transport of hydrolases is the efficient retrieval of the receptor from the PVs to the sorting compartment (Golgi?). Failure to recycle the receptor might ultimately lead to its destruction in the PVs. In the present study, we analyzed whether Giardia utilizes a retromer complex to control the PV-to-Golgi retrieval of lysosomal hydrolase receptors. Although the retromer complex in Giardia seems to possess homology with one of more evolved cells, we still believe that it might show many particularities. Therefore, disclosing whether or not this complex plays a critical function in protein recycling and cell viability will contribute to understand how to control the cell cycle and how the endosomal/lysosomal pathway has evolved during the eukaryotic evolution. Besides, enlighten the endosomal-lysosomal pathway in Giardia may contribute to the design of therapeutic agents against this important human pathogen.