University of Sussex
Browse
Li, Zhaobo.pdf (56.52 MB)

Identification of degradation pathways for HSP90 client proteins

Download (56.52 MB)
thesis
posted on 2023-06-09, 05:23 authored by Zhaobo Li
Heat shock protein 90 (HSP90) is an ATP-dependent molecular chaperone that plays critical roles in regulating the folding, stabilization, post-translational modification, activation and maturation of its various client proteins, of which many are oncoproteins. Impairing the function of HSP90 by the inhibition of its ATPase cycle with inhibitors such as AUY922 promotes the ubiquitylation and proteasomal degradation of its client proteins. However, we currently do not fully understand the mechanism for ATPase-inhibited triggered degradation of client proteins, and which E3 ligase systems are involved. Although previous studies revealed a number of E3 ligases including CHIP and CUL5 as potentially E3 ligases involved in the degradation of HSP90-dependent client protein, these have often used cancer cells that may have dysregulated systems. Additionally, other components of such E3 ligase systems have not been well characterised. Using a Reverse Transfection Format (RTF) siRNA screen system we identified two E3 ligases that are involved in two independent pathways for mediating proteasomal degradation of the HSP90-dependent protein kinase CRAF in HEK293 cells. The elongin BC-CUL5-SOCS-box protein (ECS) complex operates one pathway for the degradation of CRAF, while a novel but poorly described HECTD3 from the HECT-family was identified as the main E3 ligase for degrading CRAF following the pharmaceutical inhibition of HSP90. We revealed a potential complexes consisting of CRAF, HSP90 and HECTD3, which may contribute towards identifying the pathway for the degrading of such HSP90-dependent client protein kinases. We were also able to show that depriving access of CRAF to CDC37 and therefore HSP90 resulted in an HECTD3 and CUL5 independent degradation pathway. These studies form the basis of establishing the complex network of pathways that help to regulate CRAF protein levels.

History

File Version

  • Published version

Pages

236.0

Department affiliated with

  • Biochemistry Theses

Qualification level

  • doctoral

Qualification name

  • phd

Language

  • eng

Institution

University of Sussex

Full text available

  • Yes

Legacy Posted Date

2017-03-27

Usage metrics

    University of Sussex (Theses)

    Categories

    No categories selected

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC