Regulatory inter-domain interactions influence Hsp70 recruitment to the DnaJB8 chaperone

Bryan D Ryder,Sofia Bali,Patrick C A Van Der Wel,Irina Matlahov,Lukasz A Joachimiak,Jaime Vaquer-Alicea

doi:10.1038/s41467-021-21147-x

Abstract

The Hsp40/Hsp70 chaperone families combine versatile folding capacity with high substrate specificity, which is mainly facilitated by Hsp40s. The structure and function of many Hsp40s remain poorly understood, particularly oligomeric Hsp40s that suppress protein aggregation. Here, we used a combination of biochemical and structural approaches to shed light on the domain interactions of the Hsp40 DnaJB8, and how they may influence recruitment of partner Hsp70s. We identify an interaction between the J-Domain (JD) and C-terminal domain (CTD) of DnaJB8 that sequesters the JD surface, preventing Hsp70 interaction. We propose a model for DnaJB8-Hsp70 recruitment, whereby the JD-CTD interaction of DnaJB8 acts as a reversible switch that can control the binding of Hsp70. These findings suggest that the evolutionarily conserved CTD of DnaJB8 is a regulatory element of chaperone activity in the proteostasis network.

Highlights

The Hsp40/Hsp[70] chaperone families combine versatile folding capacity with high substrate specificity, which is mainly facilitated by Hsp40s
Prior studies have highlighted the ability of DnaJB8 to assemble into oligomers, but little is known about DnaJB8 domain interactions in cells[17,22]
We expressed DnaJB8 fused to a green fluorescent protein (GFP) derivative mClover[3] (DnaJB8–Clover) in HEK293 cells (Fig. 1a)

Summary

Introduction

The Hsp40/Hsp[70] chaperone families combine versatile folding capacity with high substrate specificity, which is mainly facilitated by Hsp40s. 1234567890():,; The cellular chaperone network needs to handle a diversity of protein substrates in numerous different (mis)folded states This demands a combination of broad versatility and specificity in terms of substrate recognition, even though the central players 70 kDa heat-shock protein (Hsp70) and 90 kDa Hsp (Hsp90) are highly conserved. This apparent contradiction is resolved by the Hsp[40] (DnaJ) family of proteins, which are chaperones that recruit and regulate the activity of Hsp[70] chaperones in refolding misfolded proteins[1,2,3,4]. The oligomers’ structural and dynamic heterogeneity has greatly hindered efforts to study them, yielding for DnaJB6 limited-resolution cryogenic electron microscopy data[21] or requiring invasive deletion mutations to gain structural insight into soluble mutant variants[17,18,19]

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Conclusion