EXPRESSION OF ENDOPLASMIC RETICULUM OXIDOREDUCTASES (EROS) AND THEIR ROLE IN THE GI TRACT

Abstract

It has been shown that some ER redox enzymes are differentially expressed in stomach and oesophagus tissue. The tissues of the gastrointestinal system, which are subject to external changes of environment during the process of digestion, represent a novel area in which human ER oxidoreductases (Eros) can be studied. Barrett's oesophagus is a common premalignant condition characterised by acid and bile reflux. We hypothesised that the development of metaplastic tissue in Barrettʼs may be associated with changes in the expression of Eros, and that the environment of gastric reflux could drive oxidative changes in the structure of Eros. In this thesis, it is shown that Ero1α is expressed at a higher level in OE33 oesophageal adenocarcinoma cells than in OE21 oesophageal squamous carcinoma cells. Ero1β is not expressed in these cells. Altering pH or culture media or bile acid treatment does not cause any detectable changes in the expression or oxidation state of Ero1α, Ero1β or Protein Disulphide Isomerases (PDIs) in the OE21 and OE33 cell lines. Human Ero1β was produced as a recombinant HIS-tagged protein, which was inactive when thioredoxin was used as a substrate, but could oxidise PDI in vitro. Attempts were made to produce redox-state specific antibodies against either Ero1α or Ero1β. Ero1α and Ero1β-HIS recombinant proteins were used to produce hybridomas, which were tested for Ero1α or Ero1β specificity in rodent tissue and cell lines