Specific Labeling of Lens Aldehyde Dehydrogenase Class 1 from 3H-Cholesterol or Its Derivatives

Publisher Website
Google Scholar
Abstract
We investigated the possibility that sterols could covalently modify ocular lens cell proteins. Incubation of cultured bovine lens epithelial cells (BLEC) with 3H-cholesterol led to the labeling of a cytosolic protein of about 52 kD. Two-dimensional electrophoresis of the BLEC soluble proteins and fluorography revealed one labeled protein of 52 kD, pI = 6.6, plus a weakly labeled, slightly more acidic protein of the same size. MALDI-MS analysis of both proteins recovered from duplicate gels indicated both to be aldehyde dehydrogenase class 1 (ALDH-1). The identity was confirmed by immunoprecipitation with antiserum to ALDH-1. Alkaline hydrolysis of 3H-labeled ALDH-1 released most of the radiolabel as compounds much more polar than cholesterol. We speculate that lens ALDH-1 can participate in the oxidation of cholesterol or its derivatives to unidentified sterol carboxylic acids and that the labeled protein reflects capture of ALDH-1 with sterol intermediates covalently bound to the enzyme in ester linkage. Lens ALDH-1 might, therefore, participate in the detoxication of polar sterols.