Windross, S. J. | bioRxiv Science

bioRxiv2022

Adaptation to ER-stress via serine glycine metabolism licences STING signalling and CMV control in intestinal epithelial cells

Inflammatory bowel diseases (IBD) are characterized by chronic relapsing inflammation of the gastrointestinal tract. While the molecular causality between endoplasmic reticulum (ER) stress and intestinal inflammation is widely accepted, the metabolic consequences of chronic ER-stress on the pathophysiology of IBD remain unclear. By using in vitro, ex vivo, in vivo mouse models and patient datasets, we identified a distinct polarisation of the mitochondrial one-carbon (1C) metabolism and a fine-tuning of the amino acid uptake in intestinal epithelial cells tailored to support GSH and NADPH metabolism upon chronic ER-stress. This metabolic phenotype strongly correlates with IBD severity and therapy-response. Mechanistically, we uncover that both chronic ER-stress and serine limitation disrupt cGAS/STING-signalling, impairing the epithelial response against viral and bacterial infection, fuelling experimental enteritis. Consequently, antioxidant treatment restores STING function and virus control. Collectively, our data highlight the importance of the plasticity of serine metabolism to allow proper cGAS/STING-signalling and innate immune responses upon chronic inflammation in the gut.

cell biology↗

bioRxiv2018

Immunostimulatory guide RNAs mediate potent antiviral response

Genome-editing with CRISPR has emerged as a technology with broad therapeutic potential. However, it is unclear whether CRISPR will elicit innate immune responses, which could impact both positively and negatively on the desired therapeutic effects. Here, we have examined the immune-stimulatory properties of different variants of guide RNAs (gRNAs) - in vitro transcribed gRNA (IVT-gRNA) and synthetic gRNAs with or without chemical modifications, full-length or duplexed. We find that only IVT-gRNA evokes strong expression of cytokines in a panel of cell lines while all the synthetic RNAs do not. We further find that sensing of IVT-gRNA proceeds mainly through the RIG-I/MAVS RNA sensing axis. One potential use of CRISPR is for antiviral therapy. The antiviral actions of the gRNA tested up until now have been relying purely on the gene editing function of the CRISPR machinery, which weakens its feasibility due to the difficulty to target all infected cells. When IVT-gRNA was combined with unmodified Cas9 mRNA, which also induces cytokine expression, strong immune response was obtained while maintaining nuclease activity of CRISPR. Remarkably, such combination inhibited herpes simplex virus type-1 (HSV-1) replication even though the nuclease activity was modest, and provided bystander protection to the cells that were not transfected with CRIPSR molecules. The antiviral activity of IVT-gRNA was also observed in vivo in HSV-1-infected Cas9+ mice, thus demonstrating the therapeutic potential. Our study further extends the applications of CRISPR by exploiting the immunostimulatory function of gRNAs.

immunology↗