The single epsin homolog in Giardia lamblia localizes to the ventral disk of trophozoites and is not associated with clathrin membrane coats

- The Giardia lamblia genome codes for a putative truncated epsinR homolog.
- The giardial epsin is not involved in membrane trafficking.
- The C-terminal domain targets giardial epsin to the ventral disk organelle.
- The N-terminal ENTH domain binds to phosphatidylinositol 3,4,5-trisphosphate.
- Giardial epsin links the plasma membrane to the ventral disk cytoskeleton.

Epsins serve as recruitment platforms for clathrin membrane coat protein components and induce membrane curvature via their N-terminal homology (ENTH) domain. Unexpectedly, the single ENTH domain protein, a putative epsinR homolog (Glepsin), in the diverged protozoan parasite Giardia lamblia, localizes exclusively to the specialized attachment organelle, the ventral disk (VD). Glepsin binds both to phosphatidylinositol (3,4,5)-trisphosphate phospholipids and the VD cytoskeleton, but lacks canonical domains for interaction with clathrin coat components. This suggests reassignment of giardial epsin function from membrane trafficking to a structural role in linking the plasma membrane to the highly specialized VD during evolution of this genus.

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