Interleukin-1β sequesters hypoxia inducible factor 2α to the primary cilium

Area of Science:

• Cell Biology
• Molecular Biology
• Signaling Pathways

Background:

• The primary cilium is crucial for cellular signaling in development, health, and disease.
• It plays a key role in anabolic and inflammatory responses, particularly to interleukin-1β (IL-1β).
• Hypoxia-inducible factor 2 alpha (HIF-2α) is implicated in both anabolic and inflammatory processes.

Purpose of the Study:

• To investigate the association between the primary cilium and hypoxia-inducible factors (HIFs) in inflammatory signaling.
• To determine if primary cilia elongation influences HIF-2α expression and localization during inflammation.

Main Methods:

• Articular chondrocytes were treated with IL-1β and prolyl hydroxylase inhibitors.
• Primary cilia elongation, arl13b trafficking, and HIF-2α expression/localization were analyzed.
• Experiments involved blocking HIFα transcription and using a hypomorphic mutation in IFT88.

Main Results:

• IL-1β induced primary cilia elongation and altered arl13b trafficking in chondrocytes.
• Cilia elongation correlated with transient increases in HIF-2α expression and its accumulation within the primary cilium.
• Prolyl hydroxylase inhibition also caused cilia elongation and HIF-2α accumulation, independent of HIFα transcriptional activity.

Conclusions:

• Primary cilia sequester HIF-2α, suggesting a negative regulatory role in its expression and activity.
• This study demonstrates for the first time that primary cilia regulate HIF signaling in the context of inflammation.