Membrane dynamics in giardia: Structure, function, and host interactions

Giardia intestinalis is an extracellular parasite that inhabits the human intestinal tract, with trophozoite and cyst stages in its life cycle. In this chapter we review basic aspects of structural organization, integrating information of the role of the plasma membrane in various aspects related to its composition, function, and importance at different stages, from the trophozoite form, involvement in encystation, to interactions with the host. Additionally, the membrane's composition, biochemical activities, receptors, and various functions it performs at different stages will be thoroughly explored. The parasite exhibits a unique and fascinating organelle: the peripheral vesicles (PVs). The membranes of these PVs will be explored, foscusing in how they drive endocytic uptake, mediate exocytic release, and carry out lysosomal degradation, all of which are essential for maintaining cellular homeostasis. Additionally, the membranes of the endoplasmic reticulum and their critical role in protein maturation and compartmentalization, both vital for proper cellular functions, will be addressed. Another key role of membranes to be explored is in the encystation process, with the presence of encystation-specific vesicles (ESVs), which are crucial in the life cycle of G. intestinalis, enabling survival in hostile conditions. The transformation of these vesicles and their contribution to protein maturation, ensuring the infectivity and resistance of the parasite, will offer a comprehensive understanding of the mechanisms underlying this parasite's survival and adaptation. The modulation of Giardia's membranes during the adhesion process to host cells will also be addressed, along with the variant surface proteins (VSPs), which are key players in the parasite's immune evasion mechanisms.