Sec8: a novel positive regulator of RIG-I in anti-RNA viral defense.

Sec8, an exocyst complex subunit, is pivotal in facilitating the docking of exocytic vesicles to fusion sites on the plasma membrane. However, its involvement in the antiviral innate immune response and virus replication remains unclear. In this study, Sec8 is identified as a novel positive regulator of RIG-I, enhancing the IFN-I signaling response against RNA viruses both in vivo and in vitro. Additionally, Sec8 stabilizes RIG-I by inhibiting its ubiquitination and subsequent proteasome-mediated degradation. Mechanistically, STUB1 degrades RIG-I via K48-linked ubiquitination at Lys190, while Sec8 suppresses STUB1 mRNA by reducing the expression of p53 and competes with STUB1 for binding to RIG-I's CARD domain, thereby preventing STUB1-mediated RIG-I degradation. Importantly, Sec8-deficient mice were more susceptible to RNA virus infection compared to wild-type mice. These findings elucidate a mechanism that Sec8 positively regulates RIG-I in the antiviral innate immune response, offering insights for developing novel therapeutic strategies and targeted antiviral medications.