Non-canonical NFKB signaling endows suppressive function through FOXP3-dependent regulatory T cell program

Regulatory T cells (Tregs) play a central role in modulating adaptive immune responses in humans and mice. The precise biological role of non-canonical nuclear factor 'κ-light-chain-enhancer' of activated B cells (NFKB) signaling in human Tregs has yet to be fully elucidated. To gain insight into this process, a Treg-like cell line (MT-2) was genetically modified using CRISPR/Cas9. Interestingly, NFKB2 knockout MT-2 cells exhibited downregulation of FOXP3, while NFKB1 knockout did not. Additionally, mRNA expression of FOXP3-dependent molecules was significantly reduced in NFKB2 knockout MT-2 cells. To better understand the functional role of the NFKB signaling, the NFKB1/NFKB2 loci of human primary Tregs were genetically edited using CRISPR/Cas9. Similar to MT-2 cells, NFKB2 knockout human Tregs displayed significantly reduced FOXP3 expression. Furthermore, NFKB2 knockout human Tregs showed downregulation of FOXP3-dependent molecules and a diminished suppressive function compared to wild-type and NFKB1 knockout Tregs. These findings indicate that non-canonical NFKB signaling maintains a Treg-like phenotype and suppressive function in human Tregs through the FOXP3-dependent regulatory T cell program.

CXCR4 signaling at the fetal-maternal interface may drive inflammation and syncytia formation during ovine pregnancy†

Early pregnancy features complex signaling between fetal trophoblast cells and maternal endometrium directing major peri-implantation events including localized inflammation and remodeling to establish proper placental development. Proinflammatory mediators are important for conceptus attachment, but a more precise understanding of molecular pathways regulating this process is needed to understand how the endometrium becomes receptive to implantation. Both chemokine ligand 12 (CXCL12) and its receptor CXCR4 are expressed by fetal and maternal tissues. We identified this pair as a critical driver of placental angiogenesis, but their additional importance to inflammation and trophoblast cell survival, proliferation, and invasion imply a role in syncytia formation at the fetal-maternal microenvironment. We hypothesized that CXCL12 encourages both endometrial inflammation and conceptus attachment during implantation. We employed separate ovine studies to (1) characterize endometrial inflammation during early gestation in the ewe, and (2) establish functional implications of CXCL12 at the fetal-maternal interface through targeted intrauterine infusion of the CXCR4 inhibitor AMD3100. Endometrial tissues were evaluated for inflammatory mediators, intracellular signaling events, endometrial modifications, and trophoblast syncytialization using western blotting and immunohistochemistry. Endometrial tissue from ewes receiving CXCR4 inhibitor demonstrated dysregulated inflammation and reduced AKT and NFKB, paired with elevated autophagic activity compared to control. Immunohistochemical observation revealed an impairment in endometrial surface remodeling and diminished trophoblast syncytialization following localized CXCR4 inhibition. These data suggest CXCL12-CXCR4 regulates endometrial inflammation and remodeling for embryonic implantation, and provide insight regarding mechanisms that, when dysregulated, lead to pregnancy pathologies such as intrauterine growth restriction and preeclampsia.

Cleavage of sequestosome 1/p62 by an enteroviral protease results in disrupted selective autophagy and impaired NFKB signaling

The adaptor protein, sequestosome 1 (SQSTM1)/p62, plays an essential role in mediating selective autophagy. It serves as an autophagy receptor targeting ubiquitinated proteins to autophagosomes for degradation. In addition, it functions as a scaffold protein to regulate signaling pathways. Here we explored the interplay between coxsackievirus B3 (CVB3) and SQSTM1-mediated selective autophagy. We reported that SQSTM1 was cleaved at glycine 241 following CVB3 infection through the activity of viral protease 2A(pro). The resulting cleavage fragments of SQSTM1 were no longer the substrates of autophagy, and their ability to form protein aggregates was greatly decreased. Although the C-terminal truncation sustained the binding activity of SQSTM1 to microtubule-associated protein 1 light chain (LC3), it failed to interact with ubiquitinated proteins. It was also found that colocalization between the C-terminal fragment of SQSTM1 (SQSTM1-C) and LC3 and ubiquitin within the punctate structures was markedly disrupted. Moreover, we observed that SQSTM1-C retained the ability of SQSTM1 to stabilize antioxidant transcription factor NFE2L2 [nuclear factor (erythroid-derived 2)-like 2]; however, both the N-terminal fragment of SQSTM1 (SQSTM1-N) and SQSTM1-C lost the function of SQSTM1 in activating NFKB (the nuclear factor of kappa light polypeptide gene enhancer in B-cells) pathway. Collectively, our results suggest a novel model by which cleavage of SQSTM1 as a result of CVB3 infection impairs the function of SQSTM1 in selective autophagy and host defense signaling.