β-arrestin1 protects intestinal tight junction through promoting mitofusin 2 transcription to drive parkin-dependent mitophagy in colitis.

Background: Intestinal barrier defect is an essential inflammatory bowel disease (IBD) pathogenesis. Mitochondrial dysfunction results in energy deficiency and oxidative stress, which contribute to the pathogenesis of IBD. β-arrestin1 (ARRB1) is a negative regulator that promotes G protein-coupled receptors desensitization, endocytosis, and degradation. However, its role in maintaining the intestinal barrier remains unclear.

Methods: Dextran sulfate sodium-induced colitis was performed in ARRB1 knockout and wild-type mice. Intestinal permeability and tight junction proteins were measured to evaluate the intestinal barrier. Mitochondria function and mitophagic flux in mice and cell lines were detected. Finally, the interaction between ARRB1 and mitofusin 2 was investigated by co-immunoprecipitation and dual luciferase assay.

Results: We identified that ARRB1 protected the intestinal tight junction barrier against experimental colitis in vivo. ARRB1 deficiency was accompanied by abnormal mitochondrial morphology, lower adenosine triphosphate (ATP) production, and severe oxidative stress. In vitro, the knockdown of ARRB1 reduced ATP levels and mitochondrial membrane potential while increasing reactive oxygen species levels and oxidative stress. Upon ARRB1 ablation, mitophagy was inhibited, accompanied by decreased LC3BII, phosphatase and tension homologue-induced protein kinase1 (PINK1), and parkin, but increased p62 expression. Mitophagy inhibition via PINK1 siRNA or mitochondrial division inhibitor 1 impaired ARRB1-mediated tight junction protection. The interaction of ARRB1 with E2F1 activated mitophagy by enhancing the transcription of mitofusin 2.

Conclusions: Our results suggest that ARRB1 is critical to maintaining the intestinal tight junction barrier by promoting mitophagy. These results reveal a novel link between ARRB1 and the intestinal tight junction barrier, which provides theoretical support for colitis treatment.