The transient association of ERp57 with N-glycosylated proteins is regulated by glucose trimming

Fimme J. Van Der Wal, Jason D. Oliver, Stephen High

Research output: Contribution to journalArticlepeer-review

Abstract

The thiol-dependent reductase ERp57 has been shown to interact specifically with in vitro o synthesised glycoproteins imported into canine pancreatic microsomes. On this basis, it was proposed that ERp57 forms part of a glycoprotein-specific folding 'machinery', present in the lumen of the endoplasmic reticulum (ER). In this study, we have investigated the interaction of ERp57 with newly synthesised proteins using semi-permeabilised mammalian cells (SP cells), in which the ER remains essentially intact and, hence, resembles that of a living cell. We demonstrate that ERp57 interacts preferentially with the glycosylated versions of soluble and membrane proteins, and that this interaction occurs in combination with calnexin and calreticulin. For the first time, we have performed a detailed analysis of the kinetics of ERp57 binding to newly synthesised glycoproteins. We find that ERp57 associates transiently with glycoproteins - a characteristic of molecular chaperones. Using mutant SP cells deficient in glucosidase I, we confirm that the binding of ERp57 to glycoproteins depends upon glucose trimming. We also demonstrate, for the first time, that the release of ERp57 from glycoprotein substrates is dependent upon glucose trimming. These data are combined to present a unified model for the role of ERp57/ER lectin complexes during glycoprotein folding in vivo.
Original languageEnglish
Pages (from-to)51-59
Number of pages8
JournalEuropean Journal of Biochemistry
Volume256
Issue number1
DOIs
Publication statusPublished - 15 Aug 1998

Keywords

  • Endoplasmic reticulum
  • ERp57/GRP58
  • Molecular chaperone
  • N-linked glycosylation
  • Protein disulphide isomerase

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