MARK3 promotes host antiviral defense by driving GEF-H1-mediated TBK1 activation

Innate immunity constitutes the body's first line of defense against pathogenic challenge, serving not only as a physical and cellular bulwark that rapidly curbs microbial proliferation but also as the essential rheostat that orchestrates downstream adaptive immune responses. Here, we identified MARK3, a serine/threonine protein kinase of the conserved MARK family, as a crucial regulator of innate antiviral immunity that promotes type I interferon (IFN-I) production in a kinase-dependent manner. Using both in vitro and in vivo models, we demonstrate that MARK3 exerts broad-spectrum antiviral activity via a signaling axis involving GEF-H1 and TBK1. Mechanistically, MARK3 directly interacts with GEF-H1 and phosphorylates it at Ser645. This phosphorylation event potentiates the activation of TBK1, leading to enhanced IRF3 phosphorylation. Activated IRF3 then translocates to the nucleus, where it triggers potent IFN-I induction and the downstream expression of interferon-stimulated genes (ISGs). Our study establishes MARK3 as an important antiviral kinase and defines the MARK3-GEF-H1-TBK1 axis as a novel signaling pathway driving interferon-mediated antiviral defense.