Abstract
Purpose: :
Cataract is a major ocular disease that causes blindness in many developing countries. Studies from our laboratory and many others have shown that apoptosis plays a critical role in cataractogenesis. αA-crystallin (αA), a lens structure protein belongs to the small heat shock protein family that exerts anti-apoptotic functions. Mice deficient in αA (αA-/-) develops cataracts, and cell apoptosis was significant detected in αA-/- lens epithelium even before formation of obvious cataracts. However, the underlying molecular mechanism is largely unknown. The p53 protein plays a pivotal role in activating and integrating apoptosis pathways. The protein level of p53 is tight regulated by Ubiquitination. The purpose of the presented study is to explore the possible anti- apoptotic mechanism of αA through regulating the p53-mediated apoptotic signaling pathway.
Methods: :
Co-immunoprecipitation assays were used to investigate interactions between αA and p53. Reverse transcription polymerase chain reaction and Western-blot analysis were utilized to study the regulation of p53 signaling pathway in human lens epithelial cells (HLECs). MTT assay was used to evaluate cell viability under stressed conditions.
Results: :
Our results showed that αA could directly bind to p53. Such interaction leads to significantly reduction of p53 level and activity. As a result, expression of its downstream target genes such as Bax was also downregulated. Mechanistically, αA enhances the interaction between p53 and its ubiquitin E3 ligase to promote p53 degradation.
Conclusions: :
These observations suggest that one of the mechanisms for αA to protect LECs from apoptosis, thus the lens pathology occurs through negative regulation of p53 functions.
Keywords: apoptosis/cell death • cataract • crystallins