Endoplasmic Reticulum Protein Quality Control Is Determined by Cooperative Interactions between Hsp/c70 Protein and the CHIP E3 Ligase
The C terminus of Hsp70 interacting protein (CHIP) E3 ligase functions as a key regulator of protein quality control by binding the C-terminal (M/I)EEVD peptide motif of Hsp/c70(90) with its N-terminal tetratricopeptide repeat (TPR) domain and facilitating polyubiquitination of misfolded client prot...
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Published in | The Journal of biological chemistry Vol. 288; no. 43; pp. 31069 - 31079 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
United States
Elsevier Inc
25.10.2013
American Society for Biochemistry and Molecular Biology |
Subjects | |
Online Access | Get full text |
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Summary: | The C terminus of Hsp70 interacting protein (CHIP) E3 ligase functions as a key regulator of protein quality control by binding the C-terminal (M/I)EEVD peptide motif of Hsp/c70(90) with its N-terminal tetratricopeptide repeat (TPR) domain and facilitating polyubiquitination of misfolded client proteins via its C-terminal catalytic U-box. Using CFTR as a model client, we recently showed that the duration of the Hsc70-client binding cycle is a primary determinant of stability. However, molecular features that control CHIP recruitment to Hsp/c70, and hence the fate of the Hsp/c70 client, remain unknown. To understand how CHIP recognizes Hsp/c70, we utilized a dominant negative mutant in which loss of a conserved proline in the U-box domain (P269A) eliminates E3 ligase activity. In a cell-free reconstituted ER-associated degradation system, P269A CHIP inhibited Hsc70-dependent CFTR ubiquitination and degradation in a dose-dependent manner. Optimal inhibition required both the TPR and the U-box, indicating cooperativity between the two domains. Neither the wild type nor the P269A mutant changed the extent of Hsc70 association with CFTR nor the dissociation rate of the Hsc70-CFTR complex. However, the U-box mutation stimulated CHIP binding to Hsc70 while promoting CHIP oligomerization. CHIP binding to Hsc70 binding was also stimulated by the presence of an Hsc70 client with a preference for the ADP-bound state. Thus, the Hsp/c70 (M/I)EEVD motif is not a simple anchor for the TPR domain. Rather CHIP recruitment involves reciprocal allosteric interactions between its TPR and U-box domains and the substrate-binding and C-terminal domains of Hsp/c70.
Background: The CHIP E3 ligase regulates Hsp70 pro-degradation activities.
Results: The P269A CHIP U-box mutation induces CHIP oligomerization and modulates nucleotide- and substrate-dependent interactions between the TPR domain and Hsp70 C terminus.
Conclusion: The U-box domain plays a key role in CHIP recruitment to Hsp70-client complexes, possibly by controlling oligomerization.
Significance: Hsp70-CHIP substrate triage is governed by complex allosteric interactions between multiple domains in both proteins. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M113.479345 |