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Updated: Nov 16, 2025
In Vitro Analysis of E3 Ubiquitin Ligase Function
Published on: May 14, 2021
Hsp70 acts as a fine-switch that controls E3 ligase CHIP-mediated TAp63 and ΔNp63 ubiquitination and degradation
H Helena Wu1, Benfan Wang1, Stephen R Armstrong1
1370 Heritage Medical Research Center, Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
Abstract:
The major clinical problem in human cancer is metastasis. Metastases are the cause of 90% of human cancer deaths. TAp63 is a critical suppressor of tumorigenesis and metastasis. ΔNp63 acts as a dominant-negative inhibitor to block the function of p53 and TAp63. Although several ubiquitin E3 ligases have been reported to regulate p63 stability, the mechanism of p63 regulation remains partially understood. Herein, we show that CHIP, an E3 ligase with a U-box domain, physically interacts with p63 and promotes p63 degradation. Notably, Hsp70 depletion by siRNA stabilizes TAp63 in H1299 cells and destabilizes ΔNp63 in SCC9 cells. Loss of Hsp70 results in a reduction in the TAp63-CHIP interaction in H1299 cells and an increase in the interaction between ΔNp63 and CHIP in SCC9 cells. Our results reveal that Hsp70 acts as a molecular switch to control CHIP-mediated ubiquitination and degradation of p63 isoforms. Furthermore, regulation of p63 by the Hsp70-CHIP axis contributes to the migration and invasion of tumor cells. Hence, our findings demonstrate that Hsp70 is a crucial regulator of CHIP-mediated ubiquitination and degradation of p63 isoforms and identify a new pathway for maintaining TAp63 or ΔNp63 stability in cancers.
Insights
Heat shock protein 70 (Hsp70) regulates cancer metastasis by controlling the degradation of p63 isoforms via the E3 ligase CHIP. This discovery reveals a new pathway for stabilizing p63 in cancers.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Metastasis causes 90% of cancer deaths, with TAp63 suppressing tumors and ΔNp63 promoting them.
- The precise mechanisms regulating p63 stability by ubiquitin E3 ligases are not fully understood.
Purpose of the Study:
- To elucidate the role of CHIP (an E3 ligase) in p63 regulation.
- To investigate the function of Hsp70 as a molecular switch in p63 degradation.
- To determine how the Hsp70-CHIP axis impacts cancer cell migration and invasion.
Main Methods:
- Investigated the interaction between CHIP and p63.
- Utilized siRNA to deplete Hsp70 in cancer cell lines (H1299 and SCC9).
- Assessed the impact of Hsp70 depletion on p63 isoform stability and interactions with CHIP.
Main Results:
- CHIP directly interacts with p63 and promotes its degradation.
- Hsp70 depletion stabilizes TAp63 and destabilizes ΔNp63, depending on the cell type.
- Hsp70 modulates the interaction between p63 isoforms and CHIP, controlling ubiquitination and degradation.
- The Hsp70-CHIP pathway influences tumor cell migration and invasion.
Conclusions:
- Hsp70 acts as a molecular switch regulating CHIP-mediated ubiquitination and degradation of TAp63 and ΔNp63.
- This identifies a novel pathway controlling p63 isoform stability in cancer.
- Targeting the Hsp70-CHIP axis may offer new therapeutic strategies for managing cancer metastasis.
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