Soulas-Sprauel, P. | bioRxiv Science

bioRxiv2026

CASM potentiates STING-driven NFκB signaling in immune cells

Stimulator of Interferon Gene (STING), a key player of antimicrobial immune responses, has emerged as a promising target to mitigate inflammation and cancer. Following STING activation, proinflammatory molecules and type I Interferons (IFN) are released thus favoring the establishment of effective immune responses and adaptive immunity. Autophagy has been proposed to negatively regulate STING signaling. While STING activation drives microtubule-associated proteins 1A/1B light chain 3B (hereafter referred to as LC3) lipidation, the underlying mechanisms and functional consequences remain however incompletely defined. Especially, the consequences of STING-associated Conjugation of autophagy related (ATG) 8 to Single Membranes (CASM) in the control of immune responses remain elusive. Using innate and adaptive cells specifically inactivated for autophagy or CASM, we found that STING agonists primarily trigger CASM over autophagy. While STING-associated autophagy exerts negative feedback on the STING pathway and downstream type I IFN and pro-inflammatory responses, with different underlying molecular mechanisms between immune cells, STING-driven CASM potentiates NF{kappa}B-associated TNF production. These results overall uncover a new function of CASM and underscore the relevance of both CASM and autophagy in shaping STING signaling

cell biology↗

bioRxiv2024

Lymphopenia drives T cell exhaustion in immunodeficient STING gain-of-function mice

STING gain-of-function (GOF) mutations are associated with the severe autoinflammatory disease designated STING Associated Vasculopathy with onset in Infancy (SAVI). Mice with the STING GOF V154M mutation develop profound T cell lymphopenia, partly due to a blockage of T cell development in the thymus. To better characterize the mechanisms of peripheral T cell dysfunctions, we conducted a transcriptomic and phenotypic analysis on sorted splenic CD4+ and CD8+ mature T cells from STING GOF V154M mice. We identify a T cell exhaustion phenotype that manifests at a terminal stage, acquired early in life but only after reaching the peripheral environment. This phenotype is independent of type I interferons and does not rely on intrinsic STING activation in either T cells or stromal cells. Mechanistically, the limited number of mature T cells that reach the periphery appear to be quickly impacted by the lymphopenic environment, experiencing heightened stimulation of the IL-7 receptor and TCR pathways, including the NFAT pathway, a key factor in T cell exhaustion. By performing transplantation experiments with STING GOF long term-hematopoietic stem cells (LT-HSCs) along with supportive wild-type bone marrow (BM) cells, we were able to prevent the T cell exhaustion of STING GOF T cells in the resulting non-lymphopenic context, demonstrating that lymphopenia is a major driver of T cell exhaustion in STING GOF mice. T cell exhaustion, although less severe, was also observed in lymphopenic mice carrying Rag1 hypomorphic mutations. In conclusion, our results, which highlight T cell exhaustion induced by lymphopenia, could have important implications for the management of patients with severe immune deficiencies. HighlightsO_LIWe describe a phenotype of T cell exhaustion in STING GOF V154M mice, which is acquired early in life and in the periphery. C_LIO_LISTING GOF-associated T cell exhaustion is independent of type I IFNs, and STING GOF/activation in T cells or in stromal cells is not sufficient for T cell exhaustion. C_LIO_LILymphopenia is a major driver of T cell exhaustion in STING GOF mice, and increased antigenic/IL-7 stimulation of T cells in the lymphopenic context of STING GOF mice could be implicated in the induction of T cell exhaustion. C_LI

immunology↗