Figure I.

Phosphoinositide-specific binding of proteins to distinct endosomal populations. The change of phosphoinositides (PtdIns) on endosomes is reflected in their protein composition, because their associated protein factors often bind to endosomal membranes via modular domains (e.g., PH, FYVE, PX, or PROPPIN) that can specifically interact with distinct forms of PtdIns. Note that WIPI49 is one of the few PROPPIN domain-containing proteins and we hypothesize that it could bind to the membrane of late endosomes, though experimental validation is needed to prove its late endosomal localization.