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Novel Components of the Stress Assembly Sec Body Identified by Proximity Labeling
Chujun Zhang1, Elisavet Kalaitsidou2,3, J Mirjam A Damen4
1Hubrecht Institute of the KNAW and UMC Utrecht, 3584 CT Utrecht, The Netherlands.
Cells
|April 13, 2023
Summary
Sec bodies are stress-induced assemblies. This study identified 52 proteins within these structures using APEX2 tagging, revealing their role in storing ER and Golgi components during cellular stress.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Sec bodies are membraneless organelles formed by the coalescence of endoplasmic reticulum exit sites (ERES).
- Their formation is stress-induced, but their protein composition and assembly mechanisms remain incompletely understood.
Purpose of the Study:
- To identify the comprehensive protein content of stress-induced Sec bodies.
- To investigate the regulation and potential function of Sec bodies in cellular stress response.
Main Methods:
- Utilized APEX2 proximity-dependent biotinylation of Sec24AB to tag and identify Sec body proteins.
- Compared APEX2 'on' (biotin-phenol and H2O2) and 'off' conditions to specifically enrich Sec body interactors.
- Verified identified proteins through imaging and assessed their transcriptional/translational regulation.
Main Results:
- Identified 52 proteins specifically enriched in Sec bodies, including numerous ER and Golgi proteins.
- Observed that these proteins are packaged without defined stoichiometry.
- Found no evidence of transcriptional or translational regulation of Sec body components during stress-induced formation.
Conclusions:
- Sec body formation is likely driven by the aggregation of intrinsically disordered proteins, rather than transcriptional or translational control.
- Sec bodies may function as storage depots for ERES, ER, and Golgi components during cellular stress.
- The findings provide novel insights into the composition and assembly of stress granules.
