Significantly Diverged Did2/Vps46 Orthologues from the Protozoan Parasite Giardia lamblia

Abstract

The endosomal compartment performs extensive sorting functions in most eukaryotes, some of which are accomplished with the help of the multivesicular body (MVB) sorting pathway. This pathway depends on the sequential action of complexes, termed the endosomal sorting complex required for transport (ESCRT). After successful sorting, the crucial step of recycling of the ESCRT complex components requires the activation of the AAA ATPase Vps4, and Did2/Vps46 plays an important role in this activation event. The endolysosomal system of the protozoan parasite Giardia lamblia appears to lack complexity, for instead of having distinct early endosomes, late endosomes and lysosomes, there are only peripheral vesicles (PVs) that are located close to the cell periphery. Additionally, comparative genomics studies predict the presence of only a subset of the ESCRT components in G. lamblia. Thus, it is possible that the MVB pathway is not functional in G. lamblia. To address this issue, the present study focused on the two putative orthologues of Did2/Vps46 of G. lamblia as their function is likely to be pivotal for a functional MVB sorting pathway. In spite of considerable sequence divergence, compared to other eukaryotic orthologues, the proteins encoded by both these genes have the ability to function as Did2/Vps46 in the context of the yeast ESCRT pathway. Furthermore, they also localized to the cellular periphery, where PVs are also located. Thus, this report is the first to provide experimental evidence indicating the presence of a functional ESCRT component in G. lamblia by characterizing the putative Did2/Vps46 orthologues.

Unexpected organellar locations of ESCRT machinery in Giardia intestinalis and complex evolutionary dynamics spanning the transition to parasitism in the lineage Fornicata

“…Previous work analyzing only the Giardia intestinalis AWB ESCRT machinery reported absences in various components such as ESCRT-II VPS36, ESCRT-III CHMP7, and ESCRT-IIIA subunits (Dutta et. al., 2015, Saha et.…”

“…Previous investigations of the Giardia ESCRT-IIIA components determined a possible role for this complex at the endolysosomal peripheral vacuoles (Dutta et. al., 2015, Saha et.…”

“…Previous bioinformatics studies have shown Giardia intestinalis assemblage AI isolate AWB to possess patchy ESCRT-II, ESCRT-III, and ESCRT-IIIA machinery (Leung et al, 2008). However, key components within each of these were reported to be absent (Leung et al, 2008, Dutta et. al., 2015, Saha et al, 2018).…”

Resolving the homology—function relationship through comparative genomics of membrane-trafficking machinery and parasite cell biology

“…G. lamblia encodes two paralogues of Vps46, one of which, Vps46A, localizes to the cytoplasm and shows intense signal near the plasma membrane, consistent with a possible role at peripheral vacuoles [96,97]. Furthermore, either paralogue is capable of restoring vacuolar sorting of carboxypeptidase S in a yeast Vps46 knockout [97], suggesting at least partial conservation of function between yeast and Giardia .…”

“…Furthermore, either paralogue is capable of restoring vacuolar sorting of carboxypeptidase S in a yeast Vps46 knockout [97], suggesting at least partial conservation of function between yeast and Giardia .…”