HUWE1-mediated ubiquitination and degradation of TTC4 aggravates allergic rhinitis via inhibiting PINK1/parkin-dependent mitophagy and promoting FKBP5/NF-κB-induced Treg/Th17 imbalance: HUWE1-mediated TTC4 ubiquitination and degradation aggravates AR.

BACKGROUND: Previously, we proved that tetratricopeptide repeat domain 4 (TTC4) protected against inflammatory injury in allergic rhinitis (AR). This study further explored whether HECT, UBA, and WWE domain containing protein 1 (HUWE1) functions as an E3 ubiquitin ligase targeting TTC4 to participate in AR pathogenesis. METHODS: HNEpCs were stimulated with IL-13 in vitro, and mice were sensitized with ovalbumin to establish AR model. Cell viability measured by CCK-8. Intracellular and mitochondrial oxidant productions and mitochondrial membrane potential were detected with DCFH-DA, MitoSOX Red, and JC-1 staining, respectively. The proportions of Th17/Treg cells were analyzed with flow cytometry. RT-qPCR, western blot, immunofluorescence, immunohistochemistry, and ELISA were conducted to examine mRNA and protein levels. Nasal histopathology was assessed by H&E and Giemsa staining. Co-immunoprecipitation and ubiquitination assay dissect the molecular mechanism. RESULTS: HUWE1 was increased in AR mice and IL-13-stimulated HNEpCs. HUWE1 silencing stabilized TTC4 via inhibiting its ubiquitination-dependent degradation. HUWE1 knockdown diminished NLRP3 inflammasome activation and mitochondrial oxidative damage, and enhanced mitophagy under IL-13 condition, which were abolished by TTC4 silencing. Mitophagy inhibitor 3-MA/Mdivi-1 counteracted the beneficial effects of HUWE1 depletion/TTC4 overexpression on IL-13-induced HNEpCs injury. In AR mice, HUWE1 depletion relieved nasal mucosal thickening, inflammatory response and NLRP3 activation, as well as restored Treg/Th17 balance and inactivated FK506-binding protein 5 (FKBP5)/NF-κB pathway, which were abrogated upon TTC4 knockdown. CONCLUSION: HUWE1 silencing reduced TTC4 ubiquitination-dependent degradation, which enhanced mitophagy to relieve mitochondrial oxidative damage and mitigatedFKBP5/NF-κB-triggered Treg/Th17 imbalance, thus improving AR. This study provided promising therapeutic targets for AR.