The Effect of Accumulation of Mutant Myocilins in Human Trabecular Meshwork Cells

ABSTRACT

PURPOSE: To investigate the cellular fate of the mutant myocilins expressed in human trabecular meshwork (TM) cells and their potential cytotoxicity. METHODS: Cultured human TM cells were transduced with adenoviral vectors that expressed green fluorescence protein (GFP) tagged mutant myocilins (G364V, K423E, Y437H, or I477N). The cytopathic effects of the mutant myocilins on the TM cells were verified by protein blot analysis, microscopic examinations, WST-1 cell prliferation assay and yeast two hybrid assay. RESULTS: All of the mutant myocilins examined in the present study accumulated in the endoplasmic reticulum (ER), which was thought to induce ER stress, severe malformed morphology and diminished cell proliferation. In addition, the expression of mutant myocilin could selectively inhibit the secretion of wild-type myocilin. CONCLUSIONS: The dysfunction or decreased number of trabecular meshwork cells due to the cytopathic effect of mutant myocilins may cause diminished turnover of the extracellular matrix of the trabecular meshwork, and thereby increase the resistance of the trabecular outflow, which may be associated with the mechanism of primary open-angle glaucoma.