Authors: Chai Fang, Ai Hua, Li Juan, Yang Xinguang
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Background
Misfolding of Myocilin protein plays an important role in the pathogenesis of primary open angle glaucoma (POAG). GRP78 can transfer the misfolded proteins out endocytoplasmic reticulum and keep the protein synthesis function of endoplasmic reticulum.However the relationship between GRP78 and Myocilin in the pathogenesis of POAG has not been elucidated.
Objective
This study was to investigate and analyze the co-expressions of GRP78 and Myolicin in trabecular meshwork cells (TMCs) of POAG.
Methods
The trabecular meshwork tissues were obtained during the surgery of POAG and healthy donor for the isolated and in vitro culture of TMCs, and the morphology of the cells was compared between POAG-derived TMCs and donor-derived TMCs.The expression of specific factors for TMCs were detected by immunochemistry.The cells were divided into normal control group, tunicamycin (Tm)-treated group and staurosporine (STS)-treated group, and the cells were cultured by regular medium, the 1 μmol/L Tm medium or 0.1 μmol/L STS medium for 24 hours respectively.The co-expression of GRP78 and Myocilin in the cells were detected using immunofluorescence assay.This study was approved by Ethics Committee of Xi’an No.4 Hospital, and written informed consent was obtained from each patient before surgery.
Results
Primarily cultured cells showed the flat star-like and irregular appearance with 3-5 processes, round nuclei, abundant cytoplasm and black engulf particles.The 3-7 generations of POAG-derived cells grew well, showing positive expressions of laminin (LN), fibronectin (FN), neuronal specific enolase (NSE) and Vimentin.Immunofluorescence assay showed positive expressions of GRP78 and Myocilin in the cells of the Tm group, STS group and normal control group, with the reddish and green fluorescence separately.Incomplete co-expression of GRP78 and Myocilin was seen in donor-derived TMCs, and complete co-expression of GRP78 and Myocilin was found in the POAG-derived TMCs in the normal control group.Complete co-expression of GRP78 and Myocilin was exhibited in both donor- and POAG-derived TMCs in the Tm group and STS group.In addition, accumulation of GRP78 protein around nucleus was seen in both donor- and POAG-derived TMCs in the Tm group.
Conclusions
GRP78 and Myocilin proteins are completely co-expressed in POAG-derived TMCs, inferring that GRP78 and Myocilin play an interaction role in the pathogenesis and development of POAG.GRP78 may play a cytoprotective role against the apoptosis of TMCs caused by endoplasmic reticulum stress.