The Human IL-22 Receptor Is Regulated through the Action of the Novel E3 Ligase Subunit FBXW12, Which Functions as an Epithelial Growth Suppressor

Abstract

Interleukin- (IL-) 22 signaling is protective in animal models of pneumonia and bacteremia by Klebsiella pneumoniae and mediates tissue recovery from influenza and Staph aureus infection. We recently described processing of mouse lung epithelial IL-22 receptor (IL-22R) by ubiquitination on the intracellular C-terminal. To identify cellular factors that regulate human IL-22R, we screened receptor abundance while overexpressing constituents of the ubiquitin system and identify that IL-22R can be shuttled for degradation by multiple previously uncharacterized F-box protein E3 ligase subunits. We observe that in human cells IL-22R is destabilized by FBXW12. FBXW12 causes depletion of endogenous and plasmid-derived IL-22R in lung epithelia, binds the E3 ligase constituent Skp-1, and facilitates ubiquitination of IL-22R in vitro. FBXW12 knockdown with shRNA increases IL-22R abundance and STAT3 phosphorylation in response to IL-22 cytokine treatment. FBXW12 shRNA increases human epithelial cell growth and cell cycle progression with enhanced constitutive activity of map kinases JNK and ERK. These findings indicate that the heretofore-undescribed protein FBXW12 functions as an E3 ligase constituent to ubiquitinate and degrade IL-22R and that therapeutic FBXW12 inhibition may enhance IL-22 signaling and bolster mucosal host defense and infection containment.

Receptor for advanced glycation end products is targeted by FBXO10 for ubiquitination and degradation

“…There is increasing interest in the role of E3 ligase proteins in pulmonary inflammatory conditions. We have previously shown a role for several E3 ligase proteins and subunits in acute lung injury and in pulmonary fibrosis (FIEL1) (24, 26, 27, 37–40). The emerging paradigm is that modulation of specific E3 ligase activity may be a strategy to modify substrate protein levels in pathophysiologic states, such as acute lung injury, or in the progression of pulmonary fibrosis.…”

“…The SCF complex in particular targets phosphorylated substrates for ubiquitination through a recognition module, F-box protein. After overexpressing a library of F-box plasmids (24)(25)(26)(27) in B2B cells in a preliminary screen, we identified that one F-box component, FBXO10, was sufficient to decrease RAGE protein levels in B2B cells (Fig. 7A).…”

IL-22 Plays a Critical Role in Maintaining Epithelial Integrity During Pulmonary Infection

“…Further, IL-22 was shown to inactivate GSK3β, perhaps as a feedback mechanism to terminate IL-22Ra1 signaling. IL-22Ra1 was also shown to be regulated via ubiquitination by the E3 ligase FBXW12 (25). This interaction destabilizes IL-22Ra1.…”

Ubiquitination-mediated degradation of cell cycle-related proteins by F-box proteins

“…On the other hand, FBXW12 is reported to be deleted or methylated in epithelial ovarian cancer (Chesnaye Ede et al, 2015). Interestingly, knockdown of FBXW12 increases human epithelial cell growth and cell cycle progression (Franz et al, 2015), suggesting that FBXW12 is an epithelial growth suppressor probably by inhibiting cell cycle progression.…”