Novel Components of the Stress Assembly Sec Body Identified by Proximity Labeling

Chujun Zhang; Elisavet Kalaitsidou; J Mirjam A Damen; Rianne Grond; Catherine Rabouille; Wei Wu

doi:10.3390/cells12071055

Novel Components of the Stress Assembly Sec Body Identified by Proximity Labeling

Cells. 2023 Mar 30;12(7):1055. doi: 10.3390/cells12071055.

Authors

Chujun Zhang¹, Elisavet Kalaitsidou^{2

3}, J Mirjam A Damen⁴, Rianne Grond¹, Catherine Rabouille^{1

5}, Wei Wu^{2

3

4}

Affiliations

¹ Hubrecht Institute of the KNAW and UMC Utrecht, 3584 CT Utrecht, The Netherlands.
² Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), 8A Biomedical Grove, Immunos, Singapore 138648, Singapore.
³ Department of Pharmacy, National University of Singapore, Singapore 117543, Singapore.
⁴ Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
⁵ Department of Biological Science of Cells and Systems, UMC Groningen, 9713 AV Groningen, The Netherlands.

Abstract

Sec bodies are membraneless stress-induced assemblies that form by the coalescence of endoplasmic reticulum exit sites (ERES). Through APEX2 tagging of Sec24AB, we biotinylated and identified the full complement of Sec body proteins. In the presence of biotin-phenol and H₂O₂ (APEX on), APEX2 facilitates the transfer of a biotin moiety to nearby interactors of chimeric Sec24AB. Using this unbiased approach comparing APEX on and off (-H₂O₂) conditions, we identified 52 proteins specifically enriched in Sec bodies. These include a large proportion of ER and Golgi proteins, packaged without defined stoichiometry, which we could selectively verify by imaging. Interestingly, Sec body components are neither transcriptionally nor translationally regulated under the conditions that induce Sec body formation, suggesting that incorporation of these proteins into granules may be driven instead by the aggregation of nucleating proteins with a high content of intrinsically disordered regions. This reinforces the notion that Sec bodies may act as storage for ERES, ER and Golgi components during stress.

Keywords: APEX2; Sec body; early secretory pathway; mass spectrometry; stress granules.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Biotin* / metabolism
Endoplasmic Reticulum / metabolism
Golgi Apparatus / metabolism
Hydrogen Peroxide* / metabolism

Substances

Biotin
Hydrogen Peroxide

Grants and funding

This work was supported by A*STAR SIgN core fund and BMRC Central Research Fund (UIBR). C.Z. is supported by a scholarship of the China Scholarship Council (201706670014).