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Impaired autophagy and delayed autophagic clearance of transforming growth factor β-induced protein (TGFBI) in granular corneal dystrophy type 2

Authors
 Seung-Il Choi ; Bong-Yoon Kim ; Eung Kweon Kim ; Joo Young Kim ; Tae-Im Kim ; Jun-Young Oh ; Shorafidinkhuja Dadakhujaev 
Citation
 Autophagy, Vol.8(12) : 1782~1797, 2012 
Journal Title
 Autophagy 
ISSN
 1554-8627 
Issue Date
2012
Abstract
Granular corneal dystrophy type 2 (GCD2) is an autosomal dominant disease characterized by a progressive age-dependent extracellular accumulation of transforming growth factor β-induced protein (TGFBI). Corneal fibroblasts from GCD2 patients also have progressive degenerative features, but the mechanism underlying this degeneration remains unknown. Here we observed that TGFBI was degraded by autophagy, but not by the ubiquitin/proteasome-dependent pathway. We also found that GCD2 homozygous corneal fibroblasts displayed a greater number of fragmented mitochondria. Most notably, mutant TGFBI (mut-TGFBI) extensively colocalized with microtubule-associated protein 1 light chain 3β (MAP1LC3B, hereafter referred to as LC3)-enriched cytosolic vesicles and CTSD in primary cultured GCD2 corneal fibroblasts. Levels of LC3-II, a marker of autophagy activation, were significantly increased in GCD2 corneal fibroblasts. Nevertheless, levels of SQSTM1/p62 and of polyubiquitinated protein were also significantly increased in GCD2 corneal fibroblasts compared with wild-type (WT) cells. However, LC3-II levels did not differ significantly between WT and GCD2 cells, as assessed by the presence of bafilomycin A 1, the fusion blocker of autophagosomes and lysosomes. Likewise, bafilomycin A 1 caused a similar change in levels of SQSTM1. Thus, the increase in autophagosomes containing mut-TGFBI may be due to inefficient fusion between autophagosomes and lysosomes. Rapamycin, an autophagy activator, decreased mut-TGFBI, whereas inhibition of autophagy increased active caspase-3, poly (ADP-ribose) polymerase 1 (PARP1) and reduced the viability of GCD2 corneal fibroblasts compared with WT controls. These data suggest that defective autophagy may play a critical role in the pathogenesis of GCD2.
URI
http://ir.ymlib.yonsei.ac.kr/handle/22282913/89684
DOI
10.4161/auto.22067
Appears in Collections:
1. 연구논문 > 5. Research Institutes > Corneal Dystrophy Research Institute
1. 연구논문 > 1. College of Medicine > Dept. of Pharmacology
1. 연구논문 > 1. College of Medicine > Dept. of Life Science
1. 연구논문 > 1. College of Medicine > Dept. of Ophthalmology
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Link
 http://www.landesbioscience.com/journals/auto/article/22067/
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