Orwig, Susan D.
Biophysical and structural characterization of proteins implicated in glaucoma and Gaucher disease.
Degree: PhD, Chemistry and Biochemistry, 2011, Georgia Tech
The inherited form of primary open angle glaucoma, a disorder characterized by increased intraocular pressure and retina degeneration, is linked to mutations in the olfactomedin (OLF) domain of the myocilin gene. Disease-causing myocilin variants accumulate within trabecular meshwork cells instead of being secreted to the trabecular extracellular matrix thought to regulate aqueous humor flow and control intraocular pressure. Like other diseases of protein misfolding, we hypothesize myocilin toxicity originates from defects in protein biophysical properties. In this thesis, the first preparative recombinant high-yield expression and purification system for the C-terminal OLF domain of myocilin (myoc-OLF) is described. To determine the relative stability of wild-type (WT) and mutant OLF domains, a fluorescence thermal stability assay was adapted to provide the first direct evidence that mutated OLF is folded but less thermally stable than WT. In addition, mutant myocilin can be stabilized by chemical chaperones. Together, this work provides the first quantitative demonstration of compromised stability among identified OLF variants and placing myocilin glaucoma in the context of other complex diseases of protein misfolding.
Subsequent investigations into the biophysical properties of WT myoc-OLF provide insight into its structure and function. In particular, myoc-OLF is stable in the presence of glycosaminoglycans (GAGs), as well as over a wide pH range in buffers with functional groups reminiscent of such GAGs. Myoc-OLF contains significant â-sheet and â-turn secondary structure as revealed by circular dichroism analysis. At neutral pH, thermal melts indicate a highly cooperative transition with a melting temperature of ~55°C. A compact core structural domain of OLF was identified by limited proteolysis and consists of approximately residues 238-461, which retains the single disulfide bond and is as stable as the full myoc-OLF construct. This construct also is capable of generating 3D crystals for structure determination. This data, presented in Chapter 3, inform new testable hypotheses for interactions with specific trabecular extracellular matrix components.
To gain further insight into the biological function of myoc-OLF, a facile fluorescence chemical stability assay was designed to identify possible ligands and drug candidates. In the assay described in Chapter 4, the target protein is initially destabilized with a chemical denaturant and is tested for re-stabilization upon the addition of small molecules. The assay requires no prior knowledge of the structure and/or function of the target protein, and it is amendable to high-throughput screening. Application of the assay using a library of 1,280 compounds revealed 14 possible ligands and drug candidates for myoc-OLF that may also generate insights into myoc-OLF function.
Due to the high â-sheet content of monomeric myoc-OLF and presence of an aggregated species upon myoc-OLF purification, the ability of myoc-OLF to form amyloid fibrils was suspected and…
Advisors/Committee Members: Dr. Raquel Lieberman (Committee Chair), Dr. A. (Yomi) Oyelere (Committee Member), Dr. Al Merril (Committee Member), Dr. Loren Williams (Committee Member), Dr. Nicholas Hud (Committee Member), Dr. Roger Wartell (Committee Member).
Subjects/Keywords: Open-angle glaucoma; Pharmacological chaperones; High-throughput drug screen; Amyloid fibrils; Gaucher disease; Myocilin; Glaucoma; Eye Diseases; Eye Diseases Genetic aspects; Intraocular pressure; Body fluids Pressure; Eye
to Zotero / EndNote / Reference
APA (6th Edition):
Orwig, S. D. (2011). Biophysical and structural characterization of proteins implicated in glaucoma and Gaucher disease. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/45816
Chicago Manual of Style (16th Edition):
Orwig, Susan D. “Biophysical and structural characterization of proteins implicated in glaucoma and Gaucher disease.” 2011. Doctoral Dissertation, Georgia Tech. Accessed January 17, 2021.
MLA Handbook (7th Edition):
Orwig, Susan D. “Biophysical and structural characterization of proteins implicated in glaucoma and Gaucher disease.” 2011. Web. 17 Jan 2021.
Orwig SD. Biophysical and structural characterization of proteins implicated in glaucoma and Gaucher disease. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2021 Jan 17].
Available from: http://hdl.handle.net/1853/45816.
Council of Science Editors:
Orwig SD. Biophysical and structural characterization of proteins implicated in glaucoma and Gaucher disease. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/45816