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The Metastable XBP1u Transmembrane Domain Defines Determinants for Intramembrane Proteolysis by Signal Peptide Peptidase
- Source :
- Cell Reports, Vol 26, Iss 11, Pp 3087-3099.e11 (2019)
- Publication Year :
- 2019
- Publisher :
- Elsevier, 2019.
-
Abstract
- Summary: 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. : Using XBP1u and determining its functional association with Sec61, Yücel et al. describe a model in which SPP requires both conformational flexibility and site-specific interactions to proteolyze its substrate. Keywords: regulated intramembrane proteolysis, GxGD aspartic intramembrane protease, ERAD, exosite, subsite, transmembrane helix dynamics, XBP1u, HO1, SPP
- Subjects :
- Biology (General)
QH301-705.5
Subjects
Details
- Language :
- English
- ISSN :
- 22111247
- Volume :
- 26
- Issue :
- 11
- Database :
- Directory of Open Access Journals
- Journal :
- Cell Reports
- Publication Type :
- Academic Journal
- Accession number :
- edsdoj.60d8072ac21a442c9cfc6d10165dcdc1
- Document Type :
- article
- Full Text :
- https://doi.org/10.1016/j.celrep.2019.02.057