Twayana, K. | Search bioRxiv

bioRxiv2026

Glutamate transporter xCT is important for cGAS-dependent interferon responses to DNA and to HSV-1

Metabolic reprogramming is a key component of antiviral immunity, yet how metabolite transport regulates innate immune signaling remains incompletely understood. Here, we show that infection with herpes simplex virus 1 (HSV-1) and stimulation with cytosolic DNA induce the cellular export of glutamate via the xCT (SLC7A11) transporter and that inhibition of xCT reduces cellular resistance to viral replication. Mechanistically, xCT inhibition impaired cGAS-STING signaling by reducing DNA-induced cGAMP production, thereby diminishing type I interferon (IFN/{beta}) responses and downstream induction of interferon-stimulated genes. Interestingly, modulating intracellular glutamate levels through inhibition of other glutamate pathways, e.g., glutaminolysis or glutamate import, also affected cellular IFN responses, suggesting that glutamate is a central control knob for DNA sensing. Finally, we demonstrate that HSV-1 suppresses xCT expression via a mechanism dependent on the immediate early viral protein ICP27, thereby promoting viral replication by limiting cGAS-dependent IFN induction. Together, these findings identify xCT-dependent glutamate transport as a critical metabolic regulator of cGAS-STING-mediated antiviral immunity.

immunology↗

bioRxiv2023

Human inborn errors of long-chain fatty acid oxidation show impaired inflammatory responses to TLR4-ligand LPS

Stimulation of mammalian cells with inflammatory inducers such as lipopolysaccharide (LPS) leads to alterations in the activity of central cellular metabolic pathways. Interestingly, these metabolic changes seem to be important for the subsequent release of pro-inflammatory cytokines. This has become particularly clear for enzymes of the tricarboxylic acid (TCA) cycle such as succinate dehydrogenase (SDH). LPS leads to inhibition of SDH activity and accumulation of succinate to enhance the LPS-induced formation of IL-1{beta}. If enzymes involved in beta-oxidation of fatty acids are important for sufficient responses to LPS is currently not clear. Using cells from various patients with inborn fatty acid oxidation disorders, we report that disease-causing deleterious variants of Electron Transfer Flavoprotein Dehydrogenase (ETFDH) and of Very Long Chain Acyl-CoA Dehydrogenase (ACADVL), both cause insufficient responses to stimulation with LPS. The insufficiencies included reduced TLR4 expression levels, impaired TLR4 signaling, and reduced or absent induction of pro-inflammatory cytokines such as IL-6. The insufficient responses to LPS were reproduced in cells from normal healthy controls by targeted loss-of-function of either ETFDH or ACADVL, supporting that the deleterious ETFDH and ACADVL variants cause the attenuated responses to LPS. ETFDH and ACADVL encode two distinct enzymes both involved in fatty acid beta-oxidation, and patients with these deficiencies cannot sufficiently metabolize long-chain fatty acids. With this report, we therefore provide genetic evidence from two genetically distinct but phenotypically similar human metabolic diseases, that genes important for beta-oxidation of long-chain fatty acids are also important for inflammatory responses to LPS.

immunology↗