title: A lumenal domain-dependent pathway for sorting to intralumenal vesicles of multivesicular endosomes involved in organelle morphogenesis.
abstract: Cargo partitioning into intralumenal vesicles (ILVs) of multivesicular endosomes underlies such cellular processes as receptor downregulation, viral budding, and biogenesis of lysosome-related organelles such as melanosomes. We show that the melanosomal protein Pmel17 is sorted into ILVs by a mechanism that is dependent upon lumenal determinants and conserved in non-pigment cells. Pmel17 targeting to ILVs does not require its native cytoplasmic domain or cytoplasmic residues targeted by ubiquitylation and, unlike sorting of ubiquitylated cargo, is insensitive to functional inhibition of Hrs and ESCRT complexes. Chimeric protein and deletion analyses indicate that two N-terminal lumenal subdomains are necessary and sufficient for ILV targeting. Pmel17 fibril formation, which occurs during melanosome maturation in melanocytes, requires a third lumenal subdomain and proteolytic processing that itself requires ILV localization. These results establish an Hrs- and perhaps ESCRT-independent pathway of ILV sorting by lumenal determinants and a requirement for ILV sorting in fibril formation.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Theos
authors.forename: Steven T
authors.initials: ST
authors.lastname: Truschel
authors.forename: Daniele
authors.initials: D
authors.lastname: Tenza
authors.forename: Ilse
authors.initials: I
authors.lastname: Hurbain
authors.forename: Dawn C
authors.initials: DC
authors.lastname: Harper
authors.forename: Joanne F
authors.initials: JF
authors.lastname: Berson
authors.forename: Penelope C
authors.initials: PC
authors.lastname: Thomas
authors.forename: Graça
authors.initials: G
authors.lastname: Raposo
authors.forename: Michael S
authors.initials: MS
authors.lastname: Marks
mesh_terms: D000951:Antigens, Neoplasm; D015415:Biomarkers / Q000378:metabolism; D002460:Cell Line; D011992:Endosomes / Q000378:metabolism*; D006801:Humans; D058965:MART-1 Antigen; D020460:Melanosomes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009024:Morphogenesis; D009363:Neoplasm Proteins / Q000378:metabolism; D015388:Organelles / Q000378:metabolism*; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D022161:Transport Vesicles / Q000378:metabolism*; D058951:gp100 Melanoma Antigen
chemical_list: D000951:Antigens, Neoplasm; D015415:Biomarkers; D058965:MART-1 Antigen; C548667:MLANA protein, human; D008562:Membrane Glycoproteins; D009363:Neoplasm Proteins; C548637:PMEL protein, human; D011993:Recombinant Fusion Proteins; D058951:gp100 Melanoma Antigen