Giardia lamblia Adaptor Protein 2 Plays an Essential Role in Receptor-mediated Endocytosis and Lysosome Trafficking.

RIVERO MR; VRANYCH CV; ZAMPONI N; ROPOLO AS; TOUZ MC

Woods Hole. USA.

Congreso; Annual Molecular Parasitology Meeting; 2008

The divergent eukaryote Giardia lamblia possesses only two clathrin-adaptor protein complexes (AP) involved in lysosomal protein trafficking. In mammalian cells, AP2 has been widely viewed as a key player molecule in clathrin-mediated endocytosis, simultaneously binding both clathrin and receptors. In this work, we characterize Giardia AP2, which shares high structural identity with the mammalian AP2 complex and a vital role in maintenance of the endocytic system. Specific monoclonal antibody against the µ2 subunit was used to analyze gAP2 subcellular localization, its interaction with associated proteins (e.g. receptors) and its association with clathrin. Production of µ2 double stranded RNA for protein knock-down was used to study the role of gAP2 in receptor-dependent and -independent endocytic mechanisms and the implication in Giardia survival. Furthermore, standard molecules together with a putative LDL-membrane receptor were employed in studying receptor mediated endocytosis by using classical and cutting-edged technologies like confocal and total internal reflection fluorescence (TIRF) microscopy, among others. Because there is no evidence of the presence of any clathrin-associated sorting proteins in the Giardia genome, we consider the possibility that this primitive eukaryote has a simplified mechanism for endocytosis with only AP2 being involved.