Tissue-specific Expression and Dimerization of the Endoplasmic Reticulum Oxidoreductase Ero1β

Sanjika Dias-Gunasekara,Jacob Gubbens,Marcel Van Lith,Christine Dunne,J.A Gareth Williams,Ritu Kataky,David Scoones,Adrian Lapthorn,Neil J Bulleid,Adam M Benham

doi:10.1074/jbc.m505023200

Abstract

Endoplasmic reticulum oxidoreductases (Eros) are essential for the formation of disulfide bonds. Understanding disulfide bond catalysis in mammals is important because of the involvement of protein misfolding in conditions such as diabetes, arthritis, cancer, and aging. Mammals express two related Ero proteins, Ero1alpha and Ero1beta. Ero1beta is incompletely characterized but is of physiological interest because it is induced by the unfolded protein response. Here, we show that Ero1beta can form homodimers and mixed heterodimers with Ero1alpha, in addition to Ero-PDI dimers. Ero-Ero dimers require the Ero active site, occur in vivo, and can be modeled onto the Ero1p crystal structure. Our data indicate that the Ero1beta protein is constitutively strongly expressed in the stomach and the pancreas, but in a cell-specific fashion. In the stomach, selective expression of Ero1beta occurs in the enzyme-producing chief cells. In pancreatic islets, Ero1beta expression is high, but is inversely correlated with PDI and PDIp levels, demonstrating that cell-specific differences exist in the regulation of oxidative protein folding in vivo.

Highlights

Disulfide bond formation is an essential component of the protein folding process, and disulfide bonds are required for structural stability, enzymatic function, and regulation of protein activity [7]
Ero1␤ Proteins Are Highly Expressed in Stomach and Pancreas—Despite much interest in ER oxidoreductases, little is known about the expression of Endoplasmic reticulum oxidoreductases (Eros) proteins in mammalian tissues
Given that studies at the mRNA level suggest that Ero1␤ transcripts are high in stomach and pancreas [11], we investigated whether Ero1␤ proteins could be detected in these mouse tissues

Summary

Introduction

Disulfide bond formation is an essential component of the protein folding process, and disulfide bonds are required for structural stability, enzymatic function, and regulation of protein activity [7]. Monomeric wild-type Ero1␤ existed as a population of mainly oxidized molecules (OX) of ϳ60 kDa, based on the faster migration of the protein on non-reducing SDS-PAGE (Fig. 4A, lane 1).

Results

Conclusion