The Metastable XBP1u Transmembrane Domain Defines Determinants for Intramembrane Proteolysis by Signal Peptide Peptidase

Sara Suna Yücel, Walter Stelzer, Alessandra Lorenzoni, Manfred Wozny, Dieter Langosch, Marius K. Lemberg

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Unspliced XBP1 mRNA encodes XBP1u, the transcriptionally inert variant of the unfolded protein response (UPR) transcription factor XBP1s. XBP1u targets its mRNA-ribosome-nascent-chain-complex to the endoplasmic reticulum (ER) to facilitate UPR activation and prevents overactivation. Yet, its membrane association is controversial. Here, we use cell-free translocation and cellular assays to define a moderately hydrophobic stretch in XBP1u that is sufficient to mediate insertion into the ER membrane. Mutagenesis of this transmembrane (TM) region reveals residues that facilitate XBP1u turnover by an ER-associated degradation route that is dependent on signal peptide peptidase (SPP). Furthermore, the impact of these mutations on TM helix dynamics was assessed by residue-specific amide exchange kinetics, evaluated by a semi-automated algorithm. Based on our results, we suggest that SPP-catalyzed intramembrane proteolysis of TM helices is not only determined by their conformational flexibility, but also by side-chain interactions near the scissile peptide bond with the enzyme's active site.

Original languageEnglish
Pages (from-to)3087-3099.e11
JournalCell Reports
Volume26
Issue number11
DOIs
StatePublished - 12 Mar 2019

Keywords

  • ERAD
  • GxGD aspartic intramembrane protease
  • HO1
  • SPP
  • XBP1u
  • exosite
  • regulated intramembrane proteolysis
  • subsite
  • transmembrane helix dynamics

Fingerprint

Dive into the research topics of 'The Metastable XBP1u Transmembrane Domain Defines Determinants for Intramembrane Proteolysis by Signal Peptide Peptidase'. Together they form a unique fingerprint.

Cite this