UPR Activation and the Down-Regulation of α-Crystallin in Human High Myopia-Related Cataract Lens Epithelium.
OBJECTIVE
To investigate the expression of αA- and αB-crystallin and the unfolded protein response in the lens epithelium of patients with high myopia-related cataracts.


METHODS
The central portion of the human anterior lens capsule together with the adhering epithelial cells, approximately 5 mm in diameter, were harvested and processed within two hours after cataract surgery from high myopia-related (spherical equivalent ≥-10.00 diopters) and age-related cataract patients or from high myopia but non-cataractous patients (tissue were collected from ocular trauma patients with high myopia and lens trauma). Anterior lens samples from fresh cadaver normal human eyes were used as normal control (collected within 6 hours from death). Real-time PCR was performed to detect the mRNA levels of α-crystallins as well as unfolded protein response (UPR)-related GRP78, spliced-XBP1, ATF4 and ATF6. Western blot analysis was used to determine the protein level of α-crystallin, GRP78, p-IRE1α, p-eIF2α and ATF6.


RESULTS
In the lens epithelium of the high myopia-related cataract group and the age related cataract group, the mRNA and soluble protein expression of αA- and αB-crystallin were both decreased; additionally, the protein levels of ATF6, p-eIF2α and p-IRE1α and the gene expression levels of spliced XBP1, GRP78, ATF6 and ATF4 were greatly increased relative to the normal control.


CONCLUSIONS
These results suggest the significant loss of soluble α-crystallin and the activation of the UPR in the lens epithelium of patients with high myopia-related cataract, which may be associated with the cataractogenesis of high myopia-related cataract.
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
Jing
J
Yang
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China; Department of Ophthalmology, the First People's Hospital of Foshan, Guangdong, China.
Sheng
S
Zhou
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
Jianjun
J
Gu
Department of Ophthalmology, the Huichang County People's Hospital, Jiangxi, China.
Minfei
M
Guo
Department of Ophthalmology, Zhaoqing Gaoyao People's Hospital, Guangdong, China.
Honghui
H
Xia
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
Yizhi
Y
Liu
D000328:Adult; D002386:Cataract / Q000150:complications / Q000235:genetics* / Q000473:pathology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004848:Epithelium / Q000378:metabolism / Q000473:pathology; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000150:complications / Q000235:genetics* / Q000473:pathology; D040901:Proteomics; D056811:Unfolded Protein Response / Q000235:genetics; D038202:alpha-Crystallin A Chain / Q000096:biosynthesis / Q000235:genetics*; D038203:alpha-Crystallin B Chain / Q000096:biosynthesis / Q000235:genetics*
D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D038202:alpha-Crystallin A Chain; D038203:alpha-Crystallin B Chain