title: Reversal of mutant myocilin non-secretion and cell killing: implications for glaucoma.
abstract: Glaucoma is a progressive blinding disease characterized by gradual loss of vision due to optic neuropathy and retinal ganglion cell death. Increased intraocular pressure is a common feature of glaucoma that is thought to arise from an increased resistance to outflow of aqueous humor through the trabecular meshwork. Mutations of the myocilin gene are one cause of autosomal dominant juvenile- and adult-onset primary open angle glaucoma, but the mechanism by which mutant myocilins cause disease is poorly understood. We have found that disease-causing myocilin mutants are misfolded, are highly aggregation-prone and accumulate in large aggregates in the endoplasmic reticulum (ER) of human embryonic kidney cells and differentiated primary human trabecular meshwork (HTM) cells. In HTM cells, Pro370Leu mutant myocilin is not secreted under normal culture conditions and prolonged expression results in abnormal cell morphology and cell killing. Culturing HTM cells at 30 degrees C, a condition known to facilitate protein folding, promotes secretion of mutant myocilin, normalizes cell morphology and reverses cell lethality. Our results indicate that myocilin-associated glaucoma is an ER storage disease and suggest a progression of events in which chronic expression of misfolded, non-secreted myocilin leads to HTM cell death, trabecular meshwork dysfunction and, ultimately, a dominant glaucoma phenotype. The beneficial effects of facilitating folding and secretion of mutant myocilin suggest a new type of treatment for this form of glaucoma.
authors.affiliation: Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305-5120, USA.
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Liu
authors.forename: Douglas
authors.initials: D
authors.lastname: Vollrath
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D037281:Calnexin / Q000378:metabolism; D037282:Calreticulin / Q000378:metabolism; D002457:Cell Extracts / Q000032:analysis; D002460:Cell Line; D002470:Cell Survival; D003546:Cysteine Endopeptidases / Q000378:metabolism; D003598:Cytoskeletal Proteins; D003902:Detergents / Q000737:chemistry; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D005136:Eye Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005822:Genetic Vectors; D005901:Glaucoma / Q000178:diet therapy / Q000235:genetics*; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D045586:Intranuclear Inclusion Bodies / Q000648:ultrastructure; D008856:Microscopy, Fluorescence; D009097:Multienzyme Complexes / Q000378:metabolism; D020125:Mutation, Missense; D011233:Precipitin Tests; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D017510:Protein Folding; D013696:Temperature; D014162:Transfection; D000099179:Myocilin
chemical_list: D037281:Calnexin; D037282:Calreticulin; D002457:Cell Extracts; D003546:Cysteine Endopeptidases; D003598:Cytoskeletal Proteins; D003902:Detergents; D005136:Eye Proteins; D006023:Glycoproteins; D009097:Multienzyme Complexes; D046988:Proteasome Endopeptidase Complex; D000099179:Myocilin