ARF1 prevents aberrant type I IFN induction by regulating STING activation and recycling

Type I interferon (IFN) signalling is tightly controlled. Upon recognition of DNA by cyclic GMP AMP synthase (cGAS), stimulator of interferon genes (STING) translocates along the endoplasmic reticulum (ER)-Golgi axis to induce IFN signalling. Termination is achieved through autophagic degradation or recycling of STING by retrograde Golgi-to-ER transport. Here, we identify the GTPase ARF1 as a crucial negative regulator of cGAS-STING signaling. Heterozygous ARF1 missense mutations cause a novel type I interferonopathy associated with enhanced IFN stimulated gene expression. Disease-associated, GTPase-defective, ARF1 results in increased cGAS-STING dependent type I IFN signalling in cell lines and primary patient cells. Mechanistically, mutated ARF1 perturbs mitochondrial fusion causing cGAS activation by aberrant mitochondrial DNA, and promotes accumulation of active STING at the Golgi/ERGIC due to defective retrograde transport. Our data show that ARF1 has an unexpected dual role in maintaining cGAS-STING homeostasis, through the promotion of mitochondrial fusion and STING recycling. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was supported by DFG (German Research Foundation) grants SP1600/4-1 (to KMJS), SPP1923 (to KMJS and FK), CRC1279 (to KMJS, FK, JM, CR, SW and PW), as well as the BMBF to FK (Restrict SARS-CoV-2) and KMJS (IMMUNOMOD) and Emmy Noether Programme 458004906 to CCOM. YJC sincerely thanks Mathieu Rodero, Tatiana Moreau, Elizabeth Sztul and Paul Randazzo for the generation of early preliminary data not included in the manuscript, and Marine Depp and Carolina Uggenti for providing the eGFP-STING plasmid. YJC also thanks Paolo Piccolo for expert clinical phenotyping, Ignazia Prigione for experimental support, Gillian Rice for deriving interferon scores, and Jean-Madeleine de Sainte Agathe for clinical advice. YJC acknowledges the European Research Council (786142 E-T1IFNs), a state subsidy from the Agence Nationale de la Recherche (France) under the Investissements d avenir program bearing the reference ANR-10-IAHU-01, and MSDAVENIR (Devo-Decode Project). This study makes use of data generated by the DECIPHER community, with a full list of contributing centres available at http://decipherge nomics.org/about/ stats and via email from contact{at}deciphergenomics.org. Funding for the DECIPHER project was provided by the Wellcome Trust. AL acknowledges Inserm International Research Project (Inserm IRP) program. MH, LK, SK and VH are part of the international graduate school in molecular medicine, Ulm (IGradU). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Clinical information and samples were obtained with informed consent. The study was approved by the Comite de Protection des Personnes (ID-RCB/EUDRACT: 2014-A01017-40) in France, and the Leeds (East) Research Ethics Committee (REC reference: 10/H1307/2 IRAS project ID: 62971) in the UK. ARF1 patient cells were handled with approval of the Ethics Committee at Ulm University (Approval 530/21). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The SILAC Mass Spectrometry data have been deposited at the MassIVE database (accession no. MSV000089711). The exome and genome sequencing data are not publicly available due to the possibility of compromising privacy. Other datasets generated in this study are available from the corresponding authors upon reasonable request subject to technical constraints and completion of a material transfer agreement.