Dictyostelium EHD associates with Dynamin and participates in phagosome maturation

Abstract

Proteins that contain Eps15 homology domains (EHDs) in their C-terminus are newly identified key regulators of endosomal membrane trafficking. Here, we show that D. discoideum contains a single EHD protein (referred to as EHD) that localizes to endosomal compartments and newly formed phagosomes. We provide the first evidence that EHD regulates phagosome maturation. Deletion of EHD results in defects in intraphagosomal proteolysis and acidification. These defects are linked to early delivery of lysosomal enzymes and fast retrieval of the vacuolar H + -ATPase in maturing phagosomes. We also demonstrate that EHD physically interacts with DymA. Our results indicate that EHD and DymA can associate independently with endomembranes, and yet they share identical kinetics in recruitment to phagosomes and release during phagosome maturation. Functional analysis of ehd − , dymA − and double dymA − ehd − knockout strains indicate that DymA and EHD play non-redundant and independent functions in phagosome maturation. Finally, we show that the absence of EHD leads to increased tubulation of endosomes, indicating that EHD participates in the scission of endosomal tubules, as reported for DymA.

Dynamin-Like Protein B of Dictyostelium Contributes to Cytokinesis Cooperatively with Other Dynamins

“…DlpA may function independently of dlpB in phagocytosis. DymA has been reported to localize at the phagosomes during their maturation but, unlike dlpA, dymA did not localize at the phagocytic cup at an early stage of phagocytosis [60]. The regulatory mechanisms underlying the localization of dlpA and dymA at the cleavage furrow or the phagocytic apparatus remain elusive.…”

The endocytic pathways of Dictyostelium discoideum

“…Recently it was also shown that the Dictyostelium orthologue of EHD (Eps15 homology domain containing protein) is also recruited very early to phagosomes (Gueho et al, 2016). EHD proteins are structurally and functionally related to dynamin.…”

“…EHD proteins are structurally and functionally related to dynamin. Dictyostelium EHD and DymA physically interact and are recruited to the nascent phagosome simultaneously, but independently (Gueho et al, 2016). In mammals, EHD1 has been shown to regulate retromer-mediated trafficking (Zhang et al, 2012).…”

“…In mammals, EHD1 has been shown to regulate retromer-mediated trafficking (Zhang et al, 2012). Whilst disruption of DymA or EHD both result in hyper-tubulation of endosomal compartments, they appear to play functionally independent roles in phagosome maturation as in contrast to DymA mutants, EHD knockout phagosomes acidify more rapidly (Gueho et al, 2016).…”

“…Whilst it is easy to imagine a role for dynamin and EHD in the scission of recycling vesicles from nascent phagosomes and macropinosomes, this is yet to be directly tested. As WASH and the retromer are only present for the first 2-3 minutes following engulfment, but DymA and EHD remain for as long as 30 minutes, there are also likely to be a number of additional trafficking steps regulated by this membrane cleavage machinery (Buckley et al, 2016;Gueho et al, 2016).…”