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Abstract #13762 Published in IGR 8-2
Temperature sensitive secretion of mutant myocilins
Vollrath D; Liu YExperimental Eye Research 2006; 82: 1030-1036
See also comment(s) by Ernst Tamm •
Recent studies have demonstrated that glaucoma-causing mutant myocilin proteins are misfolded and retained in the endoplasmic reticulum of cells. We showed previously that P370L mutant myocilin is poorly secreted at 37° C and prolonged expression of the protein in differentiated human trabecular meshwork cells results in abnormal morphology and cell killing. Culturing cells at a lower temperature, a condition known to facilitate protein folding, enhances secretion and reverses the cytotoxic effects. We wanted to determine if temperature sensitive secretion is a general property of myocilin missense mutants. Wild-type or mutant forms of myocilin were transiently expressed in HEK 293 cells cultured at either 37 or 30° C and protein secretion was assessed by immunoblotting. Of 15 myocilin missense mutants tested, representing a range in severity of associated glaucoma phenotypes, 14 displayed increased secretion at 30° C. The sole exception was K423E, which is associated with an unusual mode of glaucoma inheritance. Generally, there is an inverse relationship between the degree of mutant myocilin secretion at 30° C and the severity of the associated glaucoma phenotype. Mutants that show abundant secretion at 30° C such as T377M, G364V, I499F and D380A are associated with less virulent glaucoma phenotypes, while mutants such as P370L, I477N, and Y437H display little secretion at 30° C and are associated with more virulent glaucoma phenotypes. We conclude that temperature sensitive secretion is a property of most olfactomedin-domain myocilin mutants. The correlation between temperature sensitive secretion and glaucoma phenotype likely reflects the intrinsic susceptibility to misfolding of individual mutant proteins. These results support the hypothesis that myocilin-induced glaucoma is a protein conformational disease. Facilitating mutant protein folding could be a new approach to development of therapies for this disease.
Dr. D. Vollrath, Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305-5120, USA; Department of Ophthalmology, Stanford University School of Medicine, Stanford, CA, USA
Classification:
3.5 Molecular biology incl. SiRNA (Part of: 3 Laboratory methods)
