title: The glaucoma-associated olfactomedin domain of myocilin forms polymorphic fibrils that are constrained by partial unfolding and peptide sequence.
abstract: The glaucoma-associated olfactomedin domain of myocilin (myoc-OLF) is a recent addition to the growing list of disease-associated amyloidogenic proteins. Inherited, disease-causing myocilin variants aggregate intracellularly instead of being secreted to the trabecular meshwork, which is a scenario toxic to trabecular meshwork cells and leads to early onset of ocular hypertension, the major risk factor for glaucoma. Here we systematically structurally and biophysically dissected myoc-OLF to better understand its amyloidogenesis. Under mildly destabilizing conditions, wild-type myoc-OLF adopts non-native structures that readily fibrillize when incubated at a temperature just below the transition for tertiary unfolding. With buffers at physiological pH, two main endpoint fibril morphologies are observed: (a) straight fibrils common to many amyloids and (b) unique micron-length, ~300 nm or larger diameter, species that lasso oligomers, which also exhibit classical spectroscopic amyloid signatures. Three disease-causing variants investigated herein exhibit non-native tertiary structures under physiological conditions, leading to a variety of growth rates and a fibril morphologies. In particular, the well-documented D380A variant, which lacks calcium, forms large circular fibrils. Two amyloid-forming peptide stretches have been identified, one for each of the main fibril morphologies observed. Our study places myoc-OLF within the larger landscape of the amylome and provides insight into the diversity of myoc-OLF aggregation that plays a role in glaucoma pathogenesis.
authors: School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive Northwest, Atlanta, GA 30332-0400, USA.
authors: Shannon E
authors: SE
authors: Hill
authors: School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive Northwest, Atlanta, GA 30332-0400, USA.
authors: Rebecca K
authors: RK
authors: Donegan
authors: School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive Northwest, Atlanta, GA 30332-0400, USA. Electronic address: raquel.lieberman@chemistry.gatech.edu.
authors: Raquel L
authors: RL
authors: Lieberman
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000378:metabolism; D002942:Circular Dichroism; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000737:chemistry; D005136:Eye Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005901:Glaucoma / Q000235:genetics / Q000378:metabolism; D006023:Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D012965:Sodium Chloride; D000099179:Myocilin
chemical_list: D000682:Amyloid; D003598:Cytoskeletal Proteins; D016326:Extracellular Matrix Proteins; D005136:Eye Proteins; D006023:Glycoproteins; D012965:Sodium Chloride; D000099179:Myocilin; C081451:olfactomedin
keywords: AFM; ANS; ER; FTIR; Fourier transform infrared spectroscopy; TEV; TM; ThT; amyloid; anilinonaphthalene-1-sulfonate; atomic force microscopy; circular dichroism; endoplasmic reticulum; protein misfolding; protein structure; thioflavin T; tobacco etch virus; trabecular meshwork