Ent3p an ENTH
domain containing protein is required for protein sorting in the multivesicular
body.
Sylvie Friant,
Anne Eugster, Eve-Isabelle Pecheur, Francois Letourneur
UMR5086 du CNRS, IBCP, 7 passage du Vercors, Lyon, 69367, France
(s.friant@ibcp.fr)
The vacuole, like the mammalian lysosome, is the primary site of hydrolase-mediated turnover of macromolecules in yeast. Many newly synthesized vacuolar proteins are transported to the lysosome/vacuole from the Golgi apparatus via sorting at the multivesicular body (MVB). A genetic screen used for isolation of new vacuolar protein sorting mutants resulted in isolation of the ent3-1 temperature-sensitive mutant. Ent3p is a yeast epsin N-terminal homology (ENTH) domain containing protein localized to the endosomal compartment. Ent3p is a specific PtdIns(3,5)P2 binding protein. The ENTH domain of Ent3p is required for its PtdIns(3,5)P2 binding activity and for its membrane interaction in vitro and in vivo. The ent3-1 mutant is defective in protein sorting into the MVB and shows a delay in transport of vacuolar hydrolases, whereas endocytosis and protein secretion are unaffected. Taken together, these results show that Ent3p is required for protein sorting into the intralumenal vesicles of the MVB via PtdIns(3,5)P2 binding.