Purchase this article with an account.
C.A. Barden, H.L. Chandler, P. Lu, C.M. H. Colitz; Phosphorylation of Telomerase and Estrogen Receptor–Alpha by AKT in Cataracts . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2866.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Increased telomerase activity is a consistent finding in all cataracts (and posterior capsular opacification, PCO) that have lens epithelial cells (LEC) undergoing epithelial–mesenchymal transformation (EMT). EMT is a nonspecific change of LEC during cataractogenesis causing the cells to undergo pseudometaplasia and migration. TERT, the catalytic subunit of telomerase, and estrogen receptor alpha (ERa) interact in cataractous LEC but not in normal LEC and both require phosphorylation for activation. Our hypothesis was to characterize the kinase(s) responsible for the phosphorylation and activation of TERT and ERa in LEC; and to determine if there is a difference between normal and cataractous LEC in this respect. Methods: Protein was extracted from normal and cataractous (diabetic and inherited) canine anterior lens capsules and quantitated by standard Bradford assay. Routine Western blot analysis was performed to evaluate normal and cataractous LEC for ERa, phosphorylated Akt (pAkt), and TERT. Then, co–immunoprecipitations were performed to evaluate whether pAkt was interatcting with ERa and/or TERT. Results: ERa, pAkt, and TERT were overexpressed in cataractous LEC and negligibly expressed in normal LEC. TERT and ERa do not co–precipitate with pAkt in normal LEC; further supporting that pAkt is not the kinase involved in normal LEC’s telomerase activity. However, TERT and ERa co–precipitate with pAkt in cataractous LEC, implying that phosphorylation of TERT and ERa are Akt–dependent during cataractogenesis. Conclusions: These results support the role of pAkt in activation of telomerase activity in cataractous LEC. In addition, pAkt also activates ERa that may be involved in regulating telomerase at the transcriptional level prior to or during EMT. A pull–down assay will be performed on similar samples to determine if the above interactions are direct interactions, confirming phosphorylation by pAkt. A better understanding of the molecular changes LEC undergo during EMT may lead to therapeutic management of cataractogenesis and PCO.
This PDF is available to Subscribers Only