Molecular cloning and functional characterization of porcine cyclic GMP–AMP synthase

•Porcine cGAS mRNA is predominantly expressed in the spleen, duodenum, jejunum, and ileum.•Porcine cGAS localizes not only in the cytosol, but also on the ER membrane.•Overexpression of porcine cGAS stimulates IFN-β expression.•Porcine cGAS-induced IFN-β expression is dependent on STING and IRF3.•Porcine cGAS is involved in PRV- and poly(dA:dT)-induced IFN-β expression. Cyclic GMP–AMP synthase (cGAS), which belongs to the nucleotidyltransferase family, recognizes cytosolic DNA and induces the type I interferon (IFN) pathway through the synthesis of the second messenger cGAMP. In this study, porcine cGAS (p-cGAS) was identified and its tissue distribution, subcellular localization, and functions in innate immunity were characterized. The coding sequence of p-cGAS is 1494bp long, encodes 497 amino acids, and is most similar (74%) to Bos taurus cGAS. p-cGAS mRNA is abundant in the spleen, duodenum, jejunum, and ileum. The subcellular distribution of p-cGAS is not only in the cytosol, but also on the endoplasmic reticulum (ER) membrane. The overexpression of wild-type p-cGAS in porcine kidney epithelial cells, but not its catalytically inactive mutants, induced IFN-β expression, which was dependent on STING and IRF3. However, the downregulation of p-cGAS by RNA interference markedly reduced IFN-β expression after pseudorabies virus (PRV) infection or poly(dA:dT) transfection. These results demonstrate that p-cGAS is an important DNA sensor, required for IFN-β activation.