title: ALIX and the multivesicular endosome: ALIX in Wonderland.
abstract: In yeast and mammalian cells, endosomal sorting complexes required for transport (ESCRT) assist in sorting ubiquitinated proteins into intralumenal vesicles (ILVs) of multivesicular endosomes (MVEs) for degradation in the lysosome/vacuole. In mammalian cells, ESCRTs also drive other topologically identical membrane deformation processes, including cytokinesis, exosome release, and virus budding. Although the ESCRT-associated protein ALIX regulates these mammalian cell-specific functions, it was believed to be dispensable for receptor sorting into ILVs, unlike its yeast homolog Bro1. Despite these differences, recent evidence suggests ALIX and Bro1 share common properties in cargo sorting and ILV formation. We review these commonalities and discuss the role of ALIX in operating 'behind the mirror' during ILV back-fusion with the limiting membrane. We also propose models of how ALIX and some ESCRTs regulate the back-fusion process.
authors.affiliation: Department of Biochemistry, University of Geneva, 30 Quai Ernest Ansermet, 1211 Geneva-4, Switzerland.
authors.forename: Christin
authors.initials: C
authors.lastname: Bissig
authors.affiliation: Department of Biochemistry, University of Geneva, 30 Quai Ernest Ansermet, 1211 Geneva-4, Switzerland. Electronic address: jean.gruenberg@unige.ch.
authors.forename: Jean
authors.initials: J
authors.lastname: Gruenberg
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D056827:Endosomal Sorting Complexes Required for Transport / Q000502:physiology*; D006801:Humans; D057146:Multivesicular Bodies / Q000378:metabolism*; D021381:Protein Transport; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology; D022161:Transport Vesicles / Q000378:metabolism; D057149:Ubiquitinated Proteins / Q000378:metabolism
chemical_list: C480237:Bro1 protein, S cerevisiae; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D056827:Endosomal Sorting Complexes Required for Transport; C117020:PDCD6IP protein, human; D029701:Saccharomyces cerevisiae Proteins; D057149:Ubiquitinated Proteins
keywords: Bro1; EGF receptor; ESCRT-mediated sorting; back-fusion; intralumenal vesicle (ILV); signaling receptor