An Hsp90 co-chaperone protein in yeast is functionally replaced by site-specific posttranslational modification in humans

Abbey D Zuehlke,Kristin Beebe,Michael Reidy,Genesis M Rivera-Marquez,Thomas Prince,D Joshua Lee,Daniel Masison,Jill Johnson,Sunmin Lee,Sarah Alsomairy,Jane B Trepel,Len Neckers,Paul Lapointe,Wanping Xu,Coney Lin

doi:10.1038/ncomms15328

Abstract

Heat shock protein 90 (Hsp90) is an essential eukaryotic molecular chaperone. To properly chaperone its clientele, Hsp90 proceeds through an ATP-dependent conformational cycle influenced by posttranslational modifications (PTMs) and assisted by a number of co-chaperone proteins. Although Hsp90 conformational changes in solution have been well-studied, regulation of these complex dynamics in cells remains unclear. Phosphorylation of human Hsp90α at the highly conserved tyrosine 627 has previously been reported to reduce client interaction and Aha1 binding. Here we report that these effects are due to a long-range conformational impact inhibiting Hsp90α N-domain dimerization and involving a region of the middle domain/carboxy-terminal domain interface previously suggested to be a substrate binding site. Although Y627 is not phosphorylated in yeast, we demonstrate that the non-conserved yeast co-chaperone, Hch1, similarly affects yeast Hsp90 (Hsp82) conformation and function, raising the possibility that appearance of this PTM in higher eukaryotes represents an evolutionary substitution for HCH1.

Highlights

Heat shock protein 90 (Hsp90) is an essential eukaryotic molecular chaperone
Since this amino acid is adjacent to the C-terminal region of Hsp[90], whose mutation causes defects in yeast growth and client remodelling (Fig. 1a)[21], we asked whether Hch[1] may influence these phenotypes
We assessed the impact on growth of HCH1 expression in combination with the previously identified Hsp82-W585T mutation[21]

Summary

Introduction

To properly chaperone its clientele, Hsp[90] proceeds through an ATP-dependent conformational cycle influenced by posttranslational modifications (PTMs) and assisted by a number of co-chaperone proteins. We propose that the Hsp82Y606E phosphomimetic mutation in yeast (equivalent to the previously identified Hsp90-Y627E in human cells20) has similar effects on growth, Hsp[90] conformation and client activity as does expression of HCH1. This residue is not phosphorylated in yeast[22], Hsp90-Y627 phosphorylation and its phosphomimetic mutation have both been associated with client dissociation and loss of Aha[1] binding in human cells[20]. Our current data are consistent with the possibility that this PTM may serve a similar function as Hch[1] in higher eukaryotes

Methods

Results

Conclusion