HSP70 chaperones IL-33 in chronic airway disease.

Rationale: IL-33 is a key driver of type 2 inflammation relevant to airway epithelial biology. However, the mechanisms for IL-33 secretion and regulation in the context of chronic airway disease is poorly understood.

Objectives: We sought to define how a disease associated isoform IL-33d34 that escapes nuclear sequestration and is tonically secreted from epithelial cells can be recruited to non-canonical secretory pathways.

Methods: IL-33d34 interaction with HSP70 was assessed and validated by affinity purification, mass-spectrometry and miniTurboID proximity labeling. Secretion and activity reporter assays were used to probe the effect of HSP70 on epithelial IL-33d34 secretion and receptor binding. Human airway disease biospecimens were analyzed for dysregulation of heat shock pathways revealing modulation of TCP1 complex intermediates.

Measurements and main results: We confirmed that HSP70 interacts directly with IL-33d34, recruits the cytokine to a vesicular compartment and enhances stability upon secretion. IL-33, HSP70 and other key mediators of proteostasis were found to be dysregulated in airway disease biospecimens and secreted extracellular vesicles. The IL-33d34 interactome was characterized and novel secretion modulators were identified.

Conclusions: This study confirms a role for HSP70 in non-canonical IL-33d34 secretion and function that may be amenable for therapeutic targeting in airway diseases.