Bidirectional modulation of HIF-2 activity through chemical ligands

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Discovery

Background:

• Hypoxia-inducible factor-2 (HIF-2) is a transcription factor crucial in cellular responses to oxygen levels.
• Dysregulated HIF-2 activity is implicated in diseases such as cancer and anemia associated with chronic kidney disease.
• Targeting HIF-2 with small molecules presents a promising therapeutic avenue.

Purpose of the Study:

• To investigate the mechanisms of small molecule ligands binding to the HIF-2α subunit.
• To identify novel HIF-2α agonists and antagonists and elucidate their modes of action.
• To understand how ligands modulate HIF-2α-ARNT heterodimerization and transcriptional activity.

Main Methods:

• Utilized X-ray crystallography to determine the binding modes of ligands.
• Employed biophysical techniques to assess ligand binding affinity and effects on heterodimerization.
• Conducted cell-based functional assays to evaluate the impact of ligands on HIF-2 transcriptional activity.

Main Results:

• Identified chemically distinct antagonists that share a common mechanism of weakening HIF-2α-ARNT heterodimerization by displacing residue M252.
• Discovered first-in-class HIF-2α agonists that stabilize heterodimerization by displacing residue Y281.
• Demonstrated that ligands binding to the same pocket can act as inhibitors or activators through allosteric modulation of different residues.

Conclusions:

• Ligands targeting the HIF-2α PAS-B pocket can allosterically control HIF-2 transcriptional activity.
• The specific pocket residue mobilized dictates whether a ligand acts as an inhibitor or an activator.
• These findings provide a foundation for developing precise HIF-2-modulating therapeutics.