Actin cytoskeleton remodeling primes RIG-I-like receptor activation.
The current dogma of RNA-mediated innate immunity is that sensing of immunostimulatory RNA ligands is sufficient for the activation of intracellular sensors and induction of interferon (IFN) responses. Here, we report that actin cytoskeleton disturbance primes RIG-I-like receptor (RLR) activation. Actin cytoskeleton rearrangement induced by virus infection or commonly used reagents to intracellularly deliver RNA triggers the relocalization of PPP1R12C, a regulatory subunit of the protein phosphatase-1 (PP1), from filamentous actin to cytoplasmic RLRs. This allows dephosphorylation-mediated RLR priming and, together with the RNA agonist, induces effective RLR downstream signaling. Genetic ablation of PPP1R12C impairs antiviral responses and enhances susceptibility to infection with several RNA viruses including SARS-CoV-2, influenza virus, picornavirus, and vesicular stomatitis virus. Our work identifies actin cytoskeleton disturbance as a priming signal for RLR-mediated innate immunity, which may open avenues for antiviral or adjuvant design.
Targeting STING to promote antitumor immunity.
Trends in cell biology
Pharmacology-based methods that promote antitumor immunity have the potential to be highly efficacious while avoiding the systemic cytotoxicity associated with traditional chemotherapies. Activation of type I interferon (IFN) signaling in antigen-presenting cell types [e.g., macrophages and dendritic cells (DCs)] is critical, if not essential, for inducing a tumor-specific adaptive immune response, including the activation of cytolytic CD8 T cells. In the context of promoting antitumor immunity, the cyclic GMP-AMP synthase/stimulator of IFN genes (cGAS/STING) pathway has emerged as a principal regulator of essential type I IFN signaling. As such, STING represents a highly attractive target for developing a first-in-class immunotherapy, albeit one with a potential for significant cell type- and downstream pathway-dependent on-target toxicities, as well as conceivable pharmacogenomic liabilities.