The Peripheral Vesicles of Trophozoites of the Primitive ProtozoanGiardia lambliaMay Correspond to Early and Late Endosomes and to Lysosomes

The Unique Endosomal/Lysosomal System of Giardia lamblia

“…The presence of hydrolase activities in the PVs was also proved for cysteine proteases and RNases, demonstrating their lysosomal characteristics (Lindmark, 1988;Ward et al, 1997;Touz et al, 2002b). In addition, their potential role in endocytosis was demonstrated by the uptake of exogenous ferritin and Lucifer yellow (Bockman and Winborn, 1968;Lanfredi-Rangel et al, 1998). Pulse-chase experiments with horseradish peroxidase and fluorescent dextran showed an early and persistent labeling of the PVs, suggesting that there is no distinction between early and late endocytic vesicles in Giardia, in contrast to what occurs in higher eukaryotes (LanfrediRangel et al, 1998;Gaechter et al, 2008).…”

“…It was observed that, after internalization, some fluid-phase markers translocated rapidly to the ER or to an associated membrane compartment termed the tubulo-vesicular network (TVN) (Abodeely et al, 2009). Moreover, the presence of protease functions within the TVN, plus 3-D reconstruction and electron microscopy tomography of trophozoites stained for acid phosphatase and glucose-6-phosphatase, suggest that there might be a connection between some vesicles and profiles of the ER (Lanfredi-Rangel et al, 1998;Abodeely et al, 2009a). However, a recent work showed, by immunofluorescence and 3-D reconstruction, that the ER membranes are found throughout the cytoplasm, but do not permeate the space occupied by PVs (Faso and Hehl, 2011).…”

“…In contrast to most eukaryotes, Giardia has highly polarized vacuoles, located underneath the plasma membrane of the dorsal side, which combine some of the characteristics of endosomes and some of lysosomes (Lindmark, 1988;Lanfredi-Rangel et al, 1998;Touz et al, 2004). These PVs, distinguished by their localization, are about 150 nm in diameter with variable oval shapes and contain a core of low electron density (Figure 3).…”

“…These PVs, distinguished by their localization, are about 150 nm in diameter with variable oval shapes and contain a core of low electron density (Figure 3). They are acidic, as shown by the uptake of acridine orange and the lysosomal markers Lyso-sensor and Lysotracker (Lanfredi-Rangel et al, 1998;Touz et al, 2002b;Touz et al, 2003). The first description of hydrolase activity in the PVs came from studies in which acid phosphatase activity was tested, showing a cytochemical localization in these vacuoles as well as in the ER and nuclear envelope cisternae (Feely and Dyer, 1987).…”

A Bioinformatical Approach to Study the Endosomal Sorting Complex Required for Transport (ESCRT) Machinery in Protozoan Parasites: The Entamoeba histolytica Case

“…It is also one of the most primitive organisms, with a substantially different endomembrane morphology as compared to higher eukaryotes. Although the morphology of membrane-bound vesicles in Giardia has been previously described, there exists few information about vesicle budding and fusion (Lanfredi-Rangel et al, 1998). Recently, it was reported that a putative gene encoding a FYVE domain-containing protein homologous to yeast Vps27 is expressed in G. lamblia.…”