The Metastable XBP1u Transmembrane Domain Defines Determinants for Intramembrane Proteolysis by Signal Peptide Peptidase.
Cell Rep
; 26(11): 3087-3099.e11, 2019 03 12.
Article
en En
| MEDLINE
| ID: mdl-30865896
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.
Palabras clave
Texto completo:
1
Bases de datos:
MEDLINE
Asunto principal:
Ácido Aspártico Endopeptidasas
/
Proteolisis
/
Proteína 1 de Unión a la X-Box
/
Membranas Intracelulares
Límite:
Humans
Idioma:
En
Revista:
Cell Rep
Año:
2019
Tipo del documento:
Article
País de afiliación:
Alemania