The glaucoma-associated olfactomedin domain of myocilin forms polymorphic fibrils that are constrained by partial unfolding and peptide sequence.

TitleThe glaucoma-associated olfactomedin domain of myocilin forms polymorphic fibrils that are constrained by partial unfolding and peptide sequence.
Publication TypeJournal Article
Year of Publication2014
AuthorsHill SE, Donegan RK, Lieberman RL
JournalJournal of molecular biology
Volume426
Issue4
Pagination921-35
Date Published2014 Feb 20
ISSN1089-8638
KeywordsAmino Acid Sequence, Amyloid, Circular Dichroism, Cytoskeletal Proteins, Extracellular Matrix Proteins, Eye Proteins, Glaucoma, Glycoproteins, Humans, Hydrogen-Ion Concentration, Molecular Sequence Data, Protein Folding, Protein Structure, Tertiary, Sodium Chloride
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.

DOI10.1016/j.jmb.2013.12.002
Alternate JournalJ. Mol. Biol.