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Published on: September 2, 2019
ERdj3 regulates BiP occupancy in living cells
1Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Journal of Cell Science
|February 5, 2013
Summary
Co-chaperones like ERdj3 enhance the protein-folding capacity of Hsp70 BiP by increasing its client affinity and regulating delivery. This interaction is crucial for protein homeostasis in the endoplasmic reticulum.
Area of Science:
- Cellular Biology
- Protein Folding
- Molecular Chaperones
Background:
- Co-chaperones modulate chaperone activity, significantly influencing the protein-folding environment.
- Endoplasmic reticulum (ER) co-chaperone ERdj3, a J protein, interacts with Hsp70 BiP, stimulating its ATPase activity and enhancing client protein binding.
Purpose of the Study:
- To investigate ERdj3 availability and its impact on BiP availability and client binding in living cells.
- To elucidate the role of J proteins in regulating BiP-client interactions within the ER.
Main Methods:
- Fluorescence Recovery After Photobleaching (FRAP) analysis to assess protein mobility.
- Native gel electrophoresis and co-immunoprecipitation to determine protein complex formation.
- Studies in living cells to observe protein dynamics and interactions.
Main Results:
- Overexpressed ERdj3-sfGFP significantly reduced BiP-GFP mobility in a client-dependent manner.
- ERdj3-GFP exhibited consistently low mobility, independent of client protein levels.
- ERdj3 was found to associate with a complex including Sec61α, suggesting translocon binding.
- Mutant BiP, unable to interact with ERdjs, showed increased mobility.
Conclusions:
- ERdjs play a dual role: increasing BiP's affinity for clients and regulating client delivery to BiP.
- ERdj3 association with the translocon facilitates early interactions with nascent peptides, promoting BiP activity.
- BiP engagement with clients is enhanced in ER subdomains rich in ERdj proteins, optimizing protein folding.
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