title: Melanosomal formation of PMEL core amyloid is driven by aromatic residues.
abstract: PMEL is a pigment cell protein that forms physiological amyloid in melanosomes. Many amyloids and/or their oligomeric precursors are toxic, causing or contributing to severe, incurable diseases including Alzheimer's and prion diseases. Striking similarities in intracellular formation pathways between PMEL and various pathological amyloids including Aβ and PrPScsuggest PMEL is an excellent model system to study endocytic amyloid. Learning how PMEL fibrils assemble without apparent toxicity may help developing novel therapies for amyloid diseases. Here we identify the critical PMEL domain that forms the melanosomal amyloid core (CAF). An unbiased alanine-scanning screen covering the entire region combined with quantitative electron microscopy analysis of the full set of mutants uncovers numerous essential residues. Many of these rely on aromaticity for function suggesting a role for π-stacking in melanosomal amyloid assembly. Various mutants are defective in amyloid nucleation. This extensive data set informs the first structural model of the CAF and provides insights into how the melanosomal amyloid core forms.
authors.affiliation: Department of Immunobiology, Yale University School of Medicine, 300 Cedar Street, New Haven CT 06519, USA.
authors.forename: Jia Shee
authors.initials: JS
authors.lastname: Hee
authors.affiliation: Department of Immunobiology, Yale University School of Medicine, 300 Cedar Street, New Haven CT 06519, USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Mitchell
authors.affiliation: Department of Cell Biology, Yale University School of Medicine, 300 Cedar Street, New Haven CT 06519, USA.
authors.forename: Xinran
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Immunobiology, Yale University School of Medicine, 300 Cedar Street, New Haven CT 06519, USA.
authors.forename: Ralf M
authors.initials: RM
authors.lastname: Leonhardt
mesh_terms: D058227:Amyloidogenic Proteins / Q000737:chemistry / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D020460:Melanosomes / Q000378:metabolism*; D058951:gp100 Melanoma Antigen / Q000737:chemistry / Q000378:metabolism*
chemical_list: D058227:Amyloidogenic Proteins; C548637:PMEL protein, human; D058951:gp100 Melanoma Antigen