Highlights d The nuclear matrix protein SAFA is required for antiviral immunity in cells and mice d SAFA directly senses viral RNA in the nucleus d SAFA facilitates antiviral immunity through interacting with chromatin remodelers d Oligomerized SAFA mediates IFNB1 transcription by activating its distal enhancers

Cell refractive index, an intrinsic optical parameter, is closely correlated with the intracellular mass and concentration. By combining optical phase-shifting interferometry (PSI) and atomic force microscope (AFM) imaging, we constructed a label free, non-invasive and quantitative refractive index of single cell measurement system, in which the accurate phase map of single cell was retrieved with PSI technique and the cell morphology with nanoscale resolution was achieved with AFM imaging. Based on the proposed AFM/PSI system, we achieved quantitative refractive index distributions of single red blood cell and Jurkat cell, respectively. Further, the quantitative change of refractive index distribution during Daunorubicin (DNR)-induced Jurkat cell apoptosis was presented, and then the content changes of intracellular biochemical components were achieved. Importantly, these results were consistent with Raman spectral analysis, indicating that the proposed PSI/AFM based refractive index system is likely to become a useful tool for intracellular biochemical components analysis measurement, and this will facilitate its application for revealing cell structure and pathological state from a new perspective.

Toxoplasma gondii is an important neurotropic pathogen that establishes latent infections in humans that can cause toxoplasmosis in immunocompromised individuals. It replicates inside host cells and has developed several strategies to manipulate host immune responses. However, the cytoplasmic pathogen-sensing pathway that detects T. gondii is not well-characterized. Here, we found that cyclic GMP-AMP synthase (cGAS), a sensor of foreign dsDNA, is required for activation of anti-T. gondii immune signaling in a mouse model. We also found that mice deficient in STING (Sting gt/gt mice) are much more susceptible to T. gondii infection than WT mice. Of note, the induction of inflammatory cytokines, type I IFNs, and interferon-stimulated genes in the spleen from Sting gt/gt mice was significantly impaired. Sting gt/gt mice exhibited more severe symptoms than cGAS-deficient mice after T. gondii infection. Interestingly, we found that the dense granule protein GRA15 from T. gondii is secreted into the host cell cytoplasm and then localizes to the endoplasmic reticulum, mediated by the second transmembrane motif in GRA15, which is essential for activating STING and innate immune responses. Mechanistically, GRA15 promoted STING polyubiquitination at Lys-337 and STING oligomerization in a TRAF protein-dependent manner. Accordingly, GRA15-deficient T. gondii failed to elicit robust innate immune responses compared with WT T. gondii. Consequently , GRA15 ؊/؊ T. gondii was more virulent and caused higher mortality of WT mice but not Sting gt/gt mice upon infection. Together, T. gondii infection triggers cGAS/STING signaling, which is enhanced by GRA15 in a STING-and TRAF-dependent manner. The protozoan parasite Toxoplasma gondii can infect nearly all warm-blooded animals (1, 2). As for humans, nearly 30% of the world's population is infected with T. gondii (3). In healthy adults, T. gondii is controlled by the immune system and remains dormant in the brain. However, in immunocompromised individuals, a defect of the immune system leads to the reactivation of the T. gondii parasites and the development of toxoplasmosis. Reactivated parasite replication causes life-threatening brain damage with brain abscesses and necrotic areas (4). Thus, HIV/AIDS patients, cancer patients, and organ transplant recipients are highly susceptible to T. gondii infection. The infection of T. gondii parasites is recognized by pattern recognition receptors (PRRs). 4 Previous studies showed that TLR11 is the PRR of T. gondii in murine cells. TLR11 is able to detect the actin-binding protein Profilin, which is required for entry of T. gondii during infection. TLR11 and TLR12 form a heterodimer in murine dendritic cells (DC) after sensing Profilin and activate adaptor protein MyD88 to initiate downstream signaling for defense against T. gondii (5). Moreover, TLR7 and TLR9 are able to compensate for the loss of TLR11 by activating

Background The CRISPR-Cas13 system is an RNA-guided RNA-targeting system and has been widely used in transcriptome engineering with potentially important clinical applications. However, it is still controversial whether Cas13 exhibits collateral activity in mammalian cells. Results Here, we find that knocking down gene expression using RfxCas13d in the adult brain neurons caused death of mice, which may result from the collateral activity of RfxCas13d rather than the loss of target gene function or off-target effects. Mechanistically, we show that RfxCas13d exhibits collateral activity in mammalian cells, which is positively correlated with the abundance of target RNA. The collateral activity of RfxCas13d could cleave 28s rRNA into two fragments, leading to translation attenuation and activation of the ZAKα-JNK/p38-immediate early gene pathway. Conclusions These findings provide new mechanistic insights into the collateral activity of RfxCas13d in mammalian cells and warn that the biosafety of the CRISPR-Cas13 system needs further evaluation before application to clinical treatments.

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