Stress-Independent Activation of XBP1s and/or ATF6 Reveals Three Functionally Diverse ER Proteostasis Environments

• Published in: Cell reports (Cambridge) Vol. 3; no. 4; pp. 1279 - 1292
• Main Authors: Shoulders, Matthew D., Ryno, Lisa M., Genereux, Joseph C., Moresco, James J., Tu, Patricia G., Wu, Chunlei, Yates, John R., Su, Andrew I., Kelly, Jeffery W., Wiseman, R. Luke
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 25.04.2013; Elsevier
• Subjects: Activating Transcription Factor 6 - metabolism; DNA-Binding Proteins - metabolism; Doxorubicin - toxicity; Endoplasmic Reticulum - metabolism; HEK293 Cells; Hep G2 Cells; Humans; Prealbumin - metabolism; Protein Folding - drug effects; Proteomics; Regulatory Factor X Transcription Factors; Transcription Factors - metabolism; Transcription, Genetic - drug effects; Transcriptome - drug effects; Trimethoprim - pharmacology; Unfolded Protein Response; X-Box Binding Protein 1
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2013.03.024

The unfolded protein response (UPR) maintains endoplasmic reticulum (ER) proteostasis through the activation of transcription factors such as XBP1s and ATF6. The functional consequences of these transcription factors for ER proteostasis remain poorly defined. Here, we describe methodology that enables orthogonal, small-molecule-mediated activation of the UPR-associated transcription factors XBP1s and/or ATF6 in the same cell independent of stress. We employ transcriptomics and quantitative proteomics to evaluate ER proteostasis network remodeling owing to the XBP1s and/or ATF6 transcriptional programs. Furthermore, we demonstrate that the three ER proteostasis environments accessible by activating XBP1s and/or ATF6 differentially influence the folding, trafficking, and degradation of destabilized ER client proteins without globally affecting the endogenous proteome. Our data reveal how the ER proteostasis network is remodeled by the XBP1s and/or ATF6 transcriptional programs at the molecular level and demonstrate the potential for selective restoration of aberrant ER proteostasis of pathologic, destabilized proteins through arm-selective UPR activation. [Display omitted] [Display omitted] ► Orthogonal, ligand-dependent control of XBP1s and/or ATF6 in a single cell ► Proteomic and transcriptomic characterization of XBP1s and/or ATF6 activation ► XBP1s and/or ATF6 influences pathogenic protein fates, but not the endogenous proteome ► Arm-selective UPR activation reduces secretion of destabilized transthyretin variants The unfolded protein response adapts endoplasmic reticulum (ER) proteostasis via stress-responsive transcription factors, including XBP1s and ATF6. Here, Wiseman and colleagues implement technology for the orthogonal, ligand-dependent activation of XBP1s and/or ATF6 in a single cell. They characterize how XBP1s and/or ATF6 activation affects ER proteostasis pathway composition and function. Adapted ER environments influence the proteostasis of destabilized protein variants without affecting the endogenous proteome. The work informs the development of proteostasis-environment-adapting therapeutics for protein-misfolding-related diseases.