ATF6-mediated mild ER stress inhibits HBV transcription and replication, which is dependent on mTOR activation

Chronic hepatitis B (CHB) remains a serious global health problem. In our previous investigation, HBV was found to activate a mild ER stress, which facilitated the establishment of persistent HBV infection. However, the role of ER stress manipulation in HBV replication and its underlying mechanisms remain still unclear. Our data showed that mild ER stress inhibited HBV transcription and replication, while severe ER stress enhanced them. Mechanistically, in contrary to the effect on HBV replication, mild ER stress activated whereas severe ER stress inhibited mTOR signaling in HBV-infected cells. Further, mTOR signaling was revealed to be critical for mild ER stress-mediated HBV inhibition. Furthermore, ATF6 but not PERK or IRE1α was found to be involved in mild ER stress-mediated mTOR and the following HBV inhibition. Moreover, ATF6, per se, could inhibit HBV transcription and replication via activating mTOR signaling. Together, ATF6-mediated mild ER stress inhibited HBV transcription and replication through mTOR activation, which might present as an important therapeutic target for CHB patients.