title: Amyloid fibril formation by the glaucoma-associated olfactomedin domain of myocilin.
abstract: Myocilin is a protein found in the extracellular matrix of trabecular meshwork tissue, the anatomical region of the eye involved in regulating intraocular pressure. Wild-type (WT) myocilin has been associated with steroid-induced glaucoma, and variants of myocilin have been linked to early-onset inherited glaucoma. Elevated levels and aggregation of myocilin hasten increased intraocular pressure and glaucoma-characteristic vision loss due to irreversible damage to the optic nerve. In spite of reports on the intracellular accumulation of mutant and WT myocilin in vitro, cell culture, and model organisms, these aggregates have not been structurally characterized. In this work, we provide biophysical evidence for the hallmarks of amyloid fibrils in aggregated forms of WT and mutant myocilin localized to the C-terminal olfactomedin (OLF) domain. These fibrils are grown under a variety of conditions in a nucleation-dependent and self-propagating manner. Protofibrillar oligomers and mature amyloid fibrils are observed in vitro. Full-length mutant myocilin expressed in mammalian cells forms intracellular amyloid-containing aggregates as well. Taken together, this work provides new insights into and raises new questions about the molecular properties of the highly conserved OLF domain, and suggests a novel protein-based hypothesis for glaucoma pathogenesis for further testing in a clinical setting.
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA.
authors.forename: Susan D
authors.initials: SD
authors.lastname: Orwig
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Perry
authors.forename: Laura Y
authors.initials: LY
authors.lastname: Kim
authors.forename: Katherine C
authors.initials: KC
authors.lastname: Turnage
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.forename: Douglas
authors.initials: D
authors.lastname: Vollrath
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Schmidt-Krey
authors.forename: Raquel L
authors.initials: RL
authors.lastname: Lieberman
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000096:biosynthesis*; D001703:Biophysics; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D005136:Eye Proteins / Q000737:chemistry / Q000378:metabolism*; D005901:Glaucoma / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D000099179:Myocilin
chemical_list: D000682:Amyloid; D003598:Cytoskeletal Proteins; D016326:Extracellular Matrix Proteins; D005136:Eye Proteins; D006023:Glycoproteins; D000099179:Myocilin; C081451:olfactomedin