Focal Adhesion Kinase–Mediated Activation of Glycogen Synthase Kinase 3β Regulates IL-33 Receptor Internalization and IL-33 Signaling

Abstract

IL-33, a relatively new member of the IL-1 cytokine family, plays a crucial role in allergic inflammation and acute lung injury. ST2L, the receptor for IL-33, is expressed on immune effector cells and lung epithelia, and plays a critical role in triggering inflammation. We have previously shown that ST2L stability is regulated by the ubiquitin-proteasome system, however its upstream internalization has not been studied. Here, we demonstrate that glycogen synthase kinase 3β (GSK3β) regulates ST2L internalization and IL-33 signaling. IL-33 treatment induced ST2L internalization, an effect was attenuated by inhibition or downregulation of GSK3β. GSK3β was found to interact with ST2L on serine residue 446 in response to IL-33 treatment. GSK3β binding site mutant (ST2LS446A) and phosphorylation site mutant (ST2LS442A) are resistant to IL-33-induced ST2L internalization. We also found that IL-33 activated focal adhesion kinase (FAK). Inhibition of FAK impaired IL-33-induced GSK3β activation and ST2L internalization. Further, inhibition of ST2L internalization enhanced IL-33-induced cytokine release in lung epithelial cells. These results suggest that modulation of the ST2L internalization by FAK/GSK3β might serve as a unique strategy to lessen pulmonary inflammation.

The family of the interleukin‐1 receptors

“…IL‐1R4 expression is also regulated at a protein level on the cell surface. In the absence of IL‐33 stimulation, IL‐1R4 is constantly turned over with a reported protein half‐life of about 5 hours . Upon binding of IL‐33 to IL‐1R4 and recruitment of IL‐1R3, the IL‐33 R complex is internalized.…”

Wounds that heal and wounds that don’t − The role of the IL-33/ST2 pathway in tissue repair and tumorigenesis

“…Once activated, GSK-3β binds to and phosphorylates ST2L resulting in the swift internalization of ST2L. Once internalized ST2L is polyubiquitinated by the E3 ubiquitin ligase FBXL19 and subsequently degraded by the proteasome [31]. As sST2 functions as a decoy receptor for IL-33 it negatively regulates ST2 signalling by sequestering IL-33 and has been shown to down regulate Th2 cell-mediated immunologic responses [32].…”

Interleukin-33 and its Receptor in Pulmonary Inflammatory Diseases

“…31 Glycogen synthase kinase 3β (GSK3β), a serine/threonine kinase, regulates ST2L internalization. 51 It has been shown that inhibition of GSK3β attenuated IL-33–induced cytokine release. 31 As a negative regulator of the IL-33/ST2 signaling pathway, TIR8 (also known as SIGIRR) dimerizes with ST2L and ultimately dampens the bioactivity of IL-33.…”

“…IL-33 triggers IL-8 and IL-6 release from PBMCs, pulmonary endothelial cells, and epithelial cells, 31,51,80,99 thus inducing neutrophil influx into alveolar spaces. The effect of IL-33 on cytokine production might be partly blocked by sST2 80 or downregulation of ST2L.…”