The reprogramming of tumor-associated macrophages (TAMs) by radiotherapy is associated with cancer patient's response and sensitization to immune checkpoint blockade, but the molecular mechanisms involved remain largely unknown. Here, we show that following ionizing radiation (IR), macrophages accumulate single and double strand-DNA breaks and fragmented mitochondria in their cytosol, and stabilize the DNA sensor cyclic GMP-AMP synthase (cGAS). We demonstrate that mitochondrial fragmentation is induced by the activation of the dynamin-related protein 1 (DRP1), and controls the stabilization of cGAS and the proinflammatory activation of irradiated macrophages. Furthermore, pharmacological and genetic inhibitions of cGAS impair the proinflammatory activation of irradiated macrophages, thus revealing that cGAS is a central effector of IR-mediated proinflammatory macrophage activation. Interestingly, we also report that the purinergic receptor P2Y2 acts as an endogenous repressor of the proinflammatory macrophage activation and demonstrate that P2Y2 inactivation enhances the capacity of irradiated macrophages to undergo a proinflammatory activation. Our results thus define a new signaling pathway elicited in macrophages by IR directing mitochondrial dynamics, cytosolic DNA recognition by cGAS and proinflammatory phenotype, which is enhanced following P2Y2 inactivation. ### Competing Interest Statement Jean-Luc Perfettini is founding member of Findimmune SAS, an Immuno-Oncology Biotech company. Jean-Luc Perfettini disclosed research funding not related to this work from NH TherAguix and Wonna Therapeutics.

Purinergic receptors and NOD-like receptor protein 3 (NLRP3) inflammasome regulate inflammation and viral infection, but their effects on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection remain poorly understood. Here, we report that the purinergic receptor P2X7 and NLRP3 inflammasome are cellular host factors required for SARS-CoV-2 infection. Lung autopsies from patients with severe coronavirus disease 2019 (COVID-19) reveal that NLRP3 expression is increased in host cellular targets of SARS-CoV-2 including alveolar macrophages, type II pneumocytes and syncytia arising from the fusion of infected macrophages, thus suggesting a potential role of NLRP3 and associated signaling pathways to both inflammation and viral replication. In vitro studies demonstrate that NLRP3-dependent inflammasome activation is detected upon macrophage abortive infection. More importantly, a weak activation of NLRP3 inflammasome is also detected during the early steps of SARS-CoV-2 infection of epithelial cells and promotes the viral replication in these cells. Interestingly, the purinergic receptor P2X7, which is known to control NLRP3 inflammasome activation, also favors the replication of D614G and alpha SARS-CoV-2 variants. Altogether, our results reveal an unexpected relationship between the purinergic receptor P2X7, the NLRP3 inflammasome and the permissiveness to SARS-CoV-2 infection that offers novel opportunities for COVID-19 treatment.