Interleukin-1␤ (IL-1␤ IntroductionInterleukin-1␤ (IL-1␤) plays an important role in infection and inflammation. 1 The generation of IL-1␤ is divided into 2 stages. In the first stage, inflammatory stimuli activate nuclear factor-B (NF-B) to promote the synthesis of pro-IL-1␤. In the second stage, pro-IL-1␤ protein is cleaved by caspase-1 to generate mature p17 IL-1␤ protein. The activation of caspase-1 is dependent on the formation of large multiprotein complexes inflammasomes in macrophages and monocytes. [2][3][4][5][6] Assembly of inflammasomes is stimulated by infection, inflammation, or danger signals. The NACHT domain-, leucine-rich repeat-, and pyrin domaincontaining protein 3 (NLRP3, also known as NALP3 or cryopyrin) inflammasome responds to a large array of stimulation, including microbial products, toxins, adenosine triphosphate (ATP), crystalline, aggregated particles. [7][8][9][10][11][12][13][14] The NLRP3 protein consists of an N-terminal pyrin domain for protein-protein interaction, a central NACHT domain for nucleotide binding and self-oligomerization, and C-terminal leucine-rich repeat motifs for ligand sensing. Mutation of the NLRP3 gene is associated with several autoinflammatory disorders, and NLRP3 is also linked to gout and diabetes. 5,15 Two signals are required for formation of NLRP3 inflammasome. NF-B-containing inflammatory signals activate NLRP3 expression. 16 A second inflammatory signal then stimulates the assembly of the NLRP3 inflammasome, through the binding of NLRP3 to apoptosis-associated speck-like protein containing a CARD domain (ASC) and recruitment of procaspase-1 molecule. Reactive oxygen species 10,13,17 and lysosomal protease cathepsin B 12,13 are potential activators of the NLRP3 inflammasome assembly. However, how inflammatory stimuli promote the formation of the NLRP3 inflammasome remains largely unclear. [2][3][4][5][6] In contrast, NLRP1 inflammasome has been successfully reconstituted in vitro with the recombinant proteins. 18 Part of the difficulties is the result of the spontaneous formation of inflammasome in vitro on cell membrane damage during the preparation of cell lysates. 19 Death-associated protein kinase (DAP-kinase, DAPk, or DAPK) is calcium/calmodulin-regulated Ser/Thr kinase that acts as a tumor suppressor. 20,21 Diminished DAPK expression is found in various types of cancer, including B lymphoma and chronic lymphocytic leukemia. 22-24 DAPK also mediates pathologic damages, such as N-methyl-D-aspartate receptor-triggered neuronal cell death. 25 DAPK is organized into multiple domains: an N-terminal kinase domain, followed by a calcium/calmodulin regulatory fragment, ankyrin repeats, a cytoskeleton binding region, and a C-terminal death domain. The multifunctional domains of DAPK are linked to diverse activities. 20,21 [26][27][28][29] and specific inhibition of T cell receptor-induced activation by DAPK. 30 DAPK is also part of a negative-feedback module in regulating the expression of inflammatory genes. 31 Recent studies reveal an intriguing interpl...

Application of regulatory T cells (Tregs) in transplantation, autoimmunity and allergy has been extensively explored, but how Foxp3 and Treg stability is regulated in vivo is incompletely understood. Here, we identify a requirement for Deltex1 (DTX1), a contributor to T-cell anergy and Foxp3 protein level maintenance in vivo. Dtx1−/− Tregs are as effective as WT Tregs in the inhibition of CD4+CD25− T-cell activation in vitro. However, the suppressive ability of Dtx1−/− Tregs is greatly impaired in vivo. We find that Foxp3 expression is diminished when Dtx1−/− Tregs are co-transferred with effector T cells in vivo. DTX1 promotes the degradation of HIF-1α. Knockout of HIF-1α restores the Foxp3 stability and rescues the defective suppressive activity in Dtx1−/− Treg cells in vivo. Our results suggest that DTX1 exerts another level of control on Treg stability in vivo by sustaining the expression of Foxp3 protein in Tregs.

Phosphoinositide 3-kinase δ (PI3Kδ) has a key role in lymphocytes, and inhibitors that target this PI3K have been approved for treatment of B cell malignancies1–3. Although studies in mouse models of solid tumours have demonstrated that PI3Kδ inhibitors (PI3Kδi) can induce anti-tumour immunity4,5, its effect on solid tumours in humans remains unclear. Here we assessed the effects of the PI3Kδi AMG319 in human patients with head and neck cancer in a neoadjuvant, double-blind, placebo-controlled randomized phase II trial (EudraCT no. 2014-004388-20). PI3Kδ inhibition decreased the number of tumour-infiltrating regulatory T (Treg) cells and enhanced the cytotoxic potential of tumour-infiltrating T cells. At the tested doses of AMG319, immune-related adverse events (irAEs) required treatment to be discontinued in 12 out of 21 of patients treated with AMG319, suggestive of systemic effects on Treg cells. Accordingly, in mouse models, PI3Kδi decreased the number of Treg cells systemically and caused colitis. Single-cell RNA-sequencing analysis revealed a PI3Kδi-driven loss of tissue-resident colonic ST2 Treg cells, accompanied by expansion of pathogenic T helper 17 (TH17) and type 17 CD8+ T (TC17) cells, which probably contributed to toxicity; this points towards a specific mode of action for the emergence of irAEs. A modified treatment regimen with intermittent dosing of PI3Kδi in mouse models led to a significant decrease in tumour growth without inducing pathogenic T cells in colonic tissue, indicating that alternative dosing regimens might limit toxicity.

Death-associated protein kinase 1 (DAPK1, DAPk, DAPK) is known for its involvement in apoptosis and autophagyassociated cell death. Here, we identified an unexpected function of DAPK1 in suppressing necroptosis. DAPK1deficiency renders macrophages and dendritic cells susceptible to necroptotic death. We also observed an inhibitory role for DAPK1 in necroptosis in HT-29 cells, since knockdown or knockout of DAPK1 in such cells increased their sensitivity to necroptosis. Increased necroptosis was associated with enhanced formation of the RIPK1-RIPK3-MLKL complex in these DAPK1-deficient cells. We further found that DAPK1-deficiency led to decreased MAPK activated kinase 2 (MK2) activation and reduced RIPK1 S321 phosphorylation, with this latter representing a critical step controlling necrosome formation. Most TNF signaling pathways, including ERK, JNK, and AKT, were not regulated by DAPK. In contrast, DAPK bound p38 MAPK and selectively promoted p38 MAPK activation, resulting in enhanced MK2 phosphorylation. Our results reveal a novel role for DAPK1 in inhibiting necroptosis and illustrate an unexpected selectivity for DAPK1 in promoting p38 MAPK-MK2 activation. Importantly, our study suggests that modulation of necroptosis and p38/MK2-mediated inflammation may be achieved by targeting DAPK1.