UNC93B1 controls STING activation in dendritic cells
MAISONNEUVE L. 1, DE LAVERGNE M. 1, FOUCHET J. 1, PODSYPANINA K. 1, MANOURY B. 1
1 INEM, INSERM U1151-CNRS UMR 8253, Université Paris Cité, Faculté de Médecine Necker, Paris, France
UNC93B1, a highly conserved 12-membrane spanning molecule residing in the endoplasmic reticulum (ER), has been identified as a key regulator in the trafficking and folding to endosomes of intracellular Toll-like receptors (TLRs) that detect microbial nucleic acids. Indeed, a mutation in the Unc93b1 gene (3d mutation) results in inhibition of intracellular TLRs signalling in dendritic cells (DCs). We have shown that UNC93B1, also binds the Ca2+ sensor stromal interaction molecule 1 or STIM1 in the ER and that this association is essential for antigen cross presentation. The group of Gwack has demonstrated abberant localisation of STING (stimulator of interferon genes) in cells deficient for STIM1, resulting in enhanced interferon secretion at the steady state. Indeed, STIM1 is required for STING localisation in the ER and the absence of STIM1 triggers STING trafficking to the Golgi apparatus and its activation. STING in an ER protein essential for type I interferon response to DNA pathogens and its abberant activation is linked to inflammation and autoimmunity. We observe that in murine dendritic cells, which express high levels of UNC93B1, UNC93B1 interacts with STING. Notably, we find that in DCs expressing the 3d mutant or less UNC93B1 protein, ER-to-Golgi trafficking of STING is defective leading to a decrease in type I IFN secretion. Furthermore, we find that overexpression of UNC93B1 in human monocyte derived DCs leads to an increase in type I IFN production. Altogether, these results point to an important role of UNC93B1 in STING-dependent type I IFN signalling.