Shifting Sands: Modulating Interactions and Outputs of the CHIP‐Hsp70/HOP‐Hsp70 Protein Quality Control Complexes

Journal Article · Wed Oct 03 00:00:00 EDT 2018 · FASEB Journal

DOI:https://doi.org/10.1096/fasebj.31.1_supplement.915.6· OSTI ID:1787052

Page, Richard C. ^[1]; Zhang, Huaqun ^[1]; Cottingim, Kelsey ^[1]; VanPelt, Jamie ^[1]; Nix, Jay C. ^[2]; Schisler, Jonathan ^[3]

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1. Department of Chemistry and Biochemistry Miami University Oxford OH
2. Molecular Biology Consortium, Beamline 4.2.2 Lawrence Berkeley National Laboratory Berkeley CA
3. Department of Medicine University of North Carolina Chapel Hill Chapel Hill NC

The 70‐kilodalton heat shock protein (Hsp70) interacts with tetratricopeptide repeat (TPR) domains of CHIP (C‐terminus of Hsp70 Interacting Protein) and HOP (Hsp Organizing Protein) using a two‐carboxylate clamp binding mechanism. Differential affinity for the TPR domains of CHIP and HOP are achieved through interactions with the six residues preceding the carboxy‐terminal Asp ₆₄₁ of Hsp70. In particular, phosphorylation of Hsp70 Thr ₆₃₆ produces a dramatic swing in binding affinities that shift preferential formation of CHIP/Hsp70 complexes to preferential formation of HOP/Hsp70 complexes. Given that CHIP‐Hsp70 complexes promote ubiquitin‐mediated degradation of Hsp70‐chaperoned clients while HOP‐Hsp70 complexes promote refolding of Hsp70‐chaperoned clients, phosphorylation of Hsp70 Thr ₆₃₆ acts as a switch that directs the output and function of cellular protein quality control. Herein, through biophysical assays and new structures of CHIP‐Hsp70 and Hop‐Hsp70 we identify the molecular mechanism that enables phosphorylation‐driven switching that directs interactions within the CHIP‐Hsp70/HOP‐Hsp70 protein quality control complexes. We also present a structure‐guided mutation of Hsp70 that bypasses Thr ₆₃₆ phosphorylation‐driven switching by recovering affinity of CHIP for phosphorylated Hsp70, thereby redirecting Hsp70 to preferentially bind to CHIP. This structure‐guided mutation corrects a binding defect present in wild type CHIP and provides a system for studying the effect of shifting output of the CHIP‐Hsp70/HOP‐Hsp70 protein quality control complexes toward chaperoned ubiquitination via the CHIP‐Hsp70 complex. Support or Funding Information The authors acknowledge financial support from the US National Science Foundation (Award No. MCB 1552113 to RCP), the American Heart Association (Award No. 16SDG26960000 to RCP), the Burroughs Wellcome Fund (Award No. 1014031 to RCP), and institutional support from Miami University through the Robert H. and Nancy J. Blayney Professorship (to RCP). The Advanced Light Source is supported by the US Department of Energy under contract number DE‐AC03‐76SF00098 at Lawrence Berkeley National Laboratory.

• Sponsoring Organization: USDOE
• Grant/Contract Number: DE‐AC03‐76SF00098
• OSTI ID: 1787052
• Journal Information: FASEB Journal, Journal Name: FASEB Journal Vol. 31 Journal Issue: S1; ISSN 0892-6638
• Publisher: FASEB
• Country of Publication: United States
• Language: English