VHL inhibitors as chemical probes of the hypoxia signalling pathway

Abstract

Von Hippel–Lindau (VHL) is the E3 ubiquitin ligase targeting hypoxia-inducible transcription factor-alpha (HIF α) for proteasomal degradation. The crucial function of VHL in response to hypoxia and cellular oxygen sensing are well established, owing to the use of genetic tools through knockout and knockdown that inactivate VHL. However, the functional consequences of specifically interrupting the interaction between VHL and HIF α remain to be elucidated. The development of a chemical probe that unambiguously blocks the VHL:HIF α interaction downstream of HIF α hydroxylation by prolyl hydroxylase domain (PHD) enzymes, would address biological questions about VHL molecular targets and functional consequences of disrupting the interaction.

Here, small molecules inhibiting the VHL:HIF α interaction were shown for the first time to stabilise HIF α and elicit HIF transcriptional activity in cells. The most potent VHL inhibitor identified is VH298. VH298 is potent, cell-permeable, selective, and not toxic at the concentration required for HIF α stabilisation. Further characterisation shows that VHL inhibitor exclusively induces HIF-dependent changes in global gene and protein expression, demonstrating the specificity of the inhibitor. VHL protein level was found to increase in the presence of VHL inhibitor, which in turn promotes the degradation of HIF α in prolonged inhibition.

The work herein characterises the VHL inhibitor as a chemical probe of the hypoxia signalling pathway with great potential to address biological questions regarding the roles and regulation of VHL. The VHL inhibitor is a unique tool due to its on target selectivity and specificity in inducing HIF activity, without affecting HIF-independent response, and exerts its effect further downstream than PHD hydroxylation. This work provides a foundation and cellular proof of concept for future studies evaluating therapeutic potential of VHL inhibitor in diseases, such as chronic anaemia, ischaemia, and inflammation-driven diseases.

Date of Award	2018
Original language	English
Awarding Institution	University of Dundee
Sponsors	Wellcome Trust
Supervisor	Alessio Ciulli (Supervisor) & Sonia Rocha (Supervisor)