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Published on: November 29, 2013
RACK1 vs. HSP90: competition for HIF-1 alpha degradation vs. stabilization
1Vascular Biology Program, Institute of Cell Engineering, Department of Pediatrics, and McKusick-Nathans Institute of Genetic Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Cell Cycle (Georgetown, Tex.)
|March 16, 2007
Summary
Receptor of activated protein C kinase (RACK1) promotes the degradation of Hypoxia-Inducible Factor 1-alpha (HIF-1alpha). RACK1 competes with HSP90, facilitating HIF-1alpha ubiquitination and degradation via the Elongin-C/B ligase complex.
Area of Science:
- Molecular Biology
- Cellular Biology
- Biochemistry
Background:
- Oxygen homeostasis is crucial for metazoan life.
- Hypoxia-Inducible Factor 1 (HIF-1) regulates gene transcription in response to oxygen levels.
- HIF-1alpha degradation is typically mediated by oxygen, prolyl hydroxylase (PHD), VHL E3 ubiquitin ligase, and the proteasome.
Purpose of the Study:
- To investigate the role of Receptor of Activated Protein C Kinase 1 (RACK1) in HIF-1alpha regulation.
- To elucidate the mechanism by which RACK1 influences HIF-1alpha stability.
- To understand the interplay between RACK1, HSP90, and the ubiquitin-proteasome system in controlling HIF-1alpha.
Main Methods:
- Identification of RACK1 as a HIF-1alpha interacting protein.
- Assays to determine RACK1's effect on HIF-1alpha degradation.
- Analysis of RACK1's competition with HSP90 for HIF-1alpha binding.
- Investigation of RACK1's interaction with the Elongin-C/B ubiquitin ligase complex.
Main Results:
- RACK1 promotes oxygen-independent degradation of HIF-1alpha.
- RACK1 competes with Heat Shock Protein 90 (HSP90) for binding to the HIF-1alpha PAS-A domain.
- RACK1 facilitates HIF-1alpha ubiquitination and proteasomal degradation by recruiting the Elongin-C/B ubiquitin ligase complex.
- RACK1 is essential for HSP90 inhibitor-induced HIF-1alpha degradation.
Conclusions:
- RACK1 functions as a key regulator of HIF-1alpha stability through an oxygen-independent pathway.
- RACK1 acts as a molecular switch, competing with HSP90 and recruiting the E3 ubiquitin ligase complex to target HIF-1alpha for degradation.
- This RACK1-mediated pathway offers a novel target for modulating HIF-1alpha activity.
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