Targeting the von Hippel-Lindau E3 ubiquitin ligase using small molecules to disrupt the VHL/HIF-1α interaction

Abstract

E3 ubiquitin ligases, which bind protein targets, leading to their ubiquitination and subsequent degradation, are attractive drug targets due to their exquisite substrate specificity. However, the development of small-molecule inhibitors has proven extraordinarily challenging as modulation of E3 ligase activities requires the targeting of protein-protein interactions. Using rational design, we have generated the first small molecule targeting the von Hippel-Lindau protein (VHL), the substrate recognition subunit of an E3 ligase, and an important target in cancer, chronic anemia, and ischemia. We have also obtained the crystal structure of VHL bound to our most potent inhibitor, confirming that the compound mimics the binding mode of the transcription factor HIF-1α, a substrate of VHL. These results have the potential to guide future development of improved lead compounds as therapeutics for the treatment of chronic anemia and ischemia.

Figure 1

(A) HIF-1α accumulation leads to the transcriptional upregulation of genes involved in the hypoxic response, such as erythropoietin (Epo), VEGF and others. (B) Under normoxic conditions, HIF-1α is hydroxylated, recognized by VHL, ubiquitinated, and degraded by the proteasome, preventing transcriptional upregulation.

Figure 2

WaterLOGSY NMR spectroscopy shows binding of 3, but not L-Hyp or NAc-Hyp-NMe, to VHL.

Scheme 1. Solid-Phase Synthesis of VHL Ligands

Figure 3

The 2.9 Å cocrystal structure of 15 (white carbons) bound to VHL, indicating that its binding mimics that of the HIF-1α peptide (yellow carbons, PDB 1LM8(21)).

Figure 4

Graphical representation showing the key interactions between 15 and VHL.