Deficiency of beta-arrestin2 alleviates apoptosis through GRP78-ATF6-CHOP signaling pathway in primary Sjogren's syndrome.

The etiology of primary Sjogren's syndrome (pSS) remains unknown, and there is no ideal drug for the specific treatment of pSS. beta-arrestin2 is a key protein that mediates desensitization and internalization of G protein-coupled receptors (GPCRs) and it participates in inflammatory and immune responses that have been found to mediate apoptosis in autoimmune disease. In this study, we established an experimental Sjogren's syndrome (ESS) mouse model to elucidate the molecular mechanisms of beta-arrestin2 in pSS. First, excessive activation of beta-arrestin2 and GRP78-ATF6-CHOP apoptosis signaling were detected in specimens from pSS patients. In vivo, we found that inhibition of GRP78-ATF6-CHOP apoptosis signaling improved ESS symptoms, and the targeted deletion of beta-arrestin2 significantly increased saliva flow, alleviated salivary gland indices, and improved tissue integrity in the ESS model by downregulating GRP78-ATF6-CHOP apoptosis signaling. In vitro, we used IFNalpha to stimulate human salivary gland epithelial cells (HSGECs), and the results showed that IFNalpha activated GRP78-ATF6-CHOP apoptosis signaling, decreased cell viability, and induced apoptosis, which were negatively regulated by the ERS inhibitor 4-PBA. In addition, beta-arrestin2 depletion downregulated GRP78-ATF6-CHOP apoptosis signaling to alleviate cell apoptosis, and the effect depended on the interaction between GRP78 and beta-arrestin2. In summary, our results suggest that excessive activation of GRP78-ATF6-CHOP apoptosis signaling is involved in the pathogenesis of pSS and that beta-arrestin2 encourages inflammation-induced epithelial apoptosis through GRP78-ATF6-CHOP apoptosis signaling. This research further clarified the underlying role of beta-arrestin2 and provided an experimental foundation for beta-arrestin2 depletion in the treatment of the human autoimmune disorder pSS.