Expression of Wild Type and Truncated Myocilins in Trabecular Meshwork Cells: their Subcellular Localization

ABSTRACT

PURPOSE: To investigate subcellular localizations of wild type myocilin and trunctated (Q368X) myocilin in cultured human trabecular meshwork (TM) cells. METHODS: GFP and GFP tagged truncated myocilin, full-length myocilin, and stromelysin were expressed in TM cells using adenoviral vectors, and their secretory properties were examined by western blotting. To determine the subcellular localizations of myocilins, cellular organelles of the infected TM cells were stained with antibodies or orgenelle specific fluorescent indicators and examined under confocal microscope. RESULTS: Wild type myocilin was expressed as discrete fine vesicles in the perinuclear region of TM cells as well as in ER, but not in microtubules or mitochondria. Colocalization of wild type and truncated myocilin, indicative of in vivo interaction of the proteins, was also observed in cells co-expressing the proteins. Truncated myocilin was found to be accumulated as aggregates in ER, and inhibited the secretion of normal myocilin. CONCLUSIONS: Our result suggests that intracellular accumulation of truncated myocilin may cause a dysfunction of the cells, resulting in alterations in structural compartmentalization of trabecular ECM and obstruction of aqueous outflow.