EHD

EHD (PF3D7_0304200) is a membrane-bound protein that functions in endocytic vesicle biogenesis and lipid mobilization during the intra-erythrocytic development of Plasmodium falciparum (PMID:26284889). It localizes to vesicles that originate at the parasite plasma membrane and migrate through the cytosol to accumulate in a large multi-vesicular-like structure juxtaposed to the food vacuole; this structure co-stains with Nile Red, marking it as a neutral lipid storage site (PMID:26284889). Pharmacological inhibition of endocytosis blocks the development of EHD-labeled vesicles and their delivery to this site, placing EHD within the endocytic vesicle biogenesis and trafficking pathway (PMID:26284889). EHD physically associates with the AP-2μ subunit of the AP-2 adaptin complex, linking it to a clathrin-independent endosomal transport route (PMID:32098816). Beyond these membrane-trafficking associations, the enzymatic activity and detailed molecular mechanism of PF3D7_0304200 have not been characterized in the available corpus.

1. 2015 Medium

   Establishing where EHD acts required knowing its subcellular itinerary; live imaging showed it marks plas-membrane-derived vesicles that converge on a Nile Red-positive neutral lipid store near the food vacuole, tying it to lipid trafficking.

   Evidence GFP-fusion live/time-lapse imaging with Nile Red and food-vacuole membrane co-staining in P. falciparum

   PMID:26284889

   Open questions at the time

   • Does not establish the biochemical activity of EHD or whether it drives vesicle scission versus tethering
   • Does not identify the lipid cargo or the mechanism of delivery to the storage site
2. 2015 Medium

   To test whether EHD's vesicle itinerary is genuinely endocytic, inhibitor experiments and proteomics placed it functionally within the endocytic machinery rather than being a passive marker.

   Evidence Pharmacological endocytosis inhibition with GFP imaging, plus co-purification proteomics in P. falciparum

   PMID:26284889

   Open questions at the time

   • Inhibitors are not specific to EHD, so a direct requirement for EHD in vesicle formation is inferred rather than shown by loss-of-function
   • The proteomic co-purification with endocytosis modulators is a single experiment without reciprocal validation
3. 2020 Medium

   Identifying molecular partners was needed to connect EHD to a defined trafficking pathway; co-IP/MS showed it binds the AP-2μ adaptin subunit, embedding it in a clathrin-independent endosomal transport route.

   Evidence Co-immunoprecipitation of HA-tagged AP-2μ followed by mass spectrometry with reverse-IP controls in P. falciparum

   PMID:32098816

   Open questions at the time

   • Does not resolve whether the EHD–AP-2μ interaction is direct or bridged by other proteins
   • Does not define the functional consequence of the interaction for EHD or AP-2

• The enzymatic activity of EHD (the corpus asserts an NTPase role in the current model but no timeline discovery demonstrates it) and the phenotypic consequence of EHD loss remain undefined.
• No direct genetic knockout/knockdown phenotype for EHD reported
• No demonstration of NTPase or membrane-remodeling activity
• No structural information on the EH domain or its ligand