Biology subjects

Weber, A. N.

Publications and source records attributed to Weber, A. N..

7 recordsLinked to original sources

bioRxiv2026

Chitin oligomers induce atypical NLRP3 inflammasome activation and innate immune training

Chitin is a highly abundant poly- N-acetyl-glucosamine (GlcNAc) and linked to immune recognition of fungal infections and asthma in humans. Ubiquitous in fungi and insects, in mammals and plants chitin represents a microbe-associated molecular pattern (MAMP) and whereas highly polymeric chitin is insoluble and immunologically inert, soluble chitin oligomers of 6 to 15 GlcNAc activate immediate pro-inflammatory cytokine release via TLR2 in human immune cells. However, TLR2 ligands do not the most typical activators of the NLRP3 inflammasome pathway or innate immune training, a phenomenon of long-term immunological remodeling. Here we show that especially 16-20 GlcNAc long chitin oligomers activate NLRP3-dependent IL-1{beta} and IL-18 release in human myeloid immune cells in an atypical, phagocytosis-dependent manner. Moreover, phagocytosis and methyl transferase activity were essential for innate immune training, by which the same chito-oligomer-training enhanced TNF release in primary murine and human immune cells. Collectively, this suggests that oligomer length impacts on the immune features of chitin which can be customized using glycan assembly.

immunology↗

bioRxiv2026

Structure of zebrafish NLRP3 reveals a novel mode of inflammasome activation

NLRP3 is an innate immune sensor of a broad range of stimuli, which upon activation forms a multiprotein inflammasome complex triggering caspase-1 activation, IL-1{beta} and IL-18 maturation, and inflammatory cell death. The canonical NLRP3 activation pathway has been well characterized from a structural perspective. It involves the association of NLRP3 with membranes in the form of inactive oligomeric "cage" complexes, which, upon activation, convert to an active oligomeric NLRP3 disc. NLRP3 structural rearrangements during non-classical NLRP3 activation pathways, however, remain unknown. Here, we report a novel mode of NLRP3 activation utilized by the NLRP3 homolog from zebrafish. The cryo-EM structure of zebrafish NLRP3 shows that, unlike human NLRP3, it forms disc-shaped heptamers that undergo further trimerization, resulting in a 21-mer oligomeric arrangement. Surprisingly, a single zebrafish NLRP3 heptamer cannot arrange its PYD domains into a PYD helix and therefore requires a trimer of heptamers to form a PYD filament that enables ASC oligomerization. Furthermore, zebrafish NLRP3 does not associate with the Golgi network, nor does it form inactive "cage" oligomers or interact with NEK7. Thus, our data demonstrate an ancestral non-canonical structural mechanism of NLRP3 activation, which may shed light on alternative NLRP3 activation pathways present in humans.

immunology↗

bioRxiv2024

BTK and MMP9 regulate NLRP3 inflammasome-dependent cytokine and NET responses in primary neutrophils.

BackgroundInflammation is a double-edged state of immune activation that is required to resolve threats harmful to the host but can also cause severe collateral damage. Polymorphonuclear neutrophils (PMN,) the primary leukocyte population in humans, mediate inflammation through the release of cytokines and neutrophil extracellular traps (NETs). Whilst the pathophysiological importance of NETs is unequivocal, the multiple molecular pathways driving NET release are not fully defined. Recently, NET release was linked to the NLRP3 inflammasome which is regulated by Brutons tyrosine kinase (BTK) in macrophages. ObjectiveAs NLRP3 inflammasome regulation by BTK has not been studied in neutrophils, we here explored a potential regulatory role of BTK in primary murine and human neutrophils and matched monocytes or macrophages from Btk-deficient vs WT mice or healthy donors (HD) vs BTK deficient X-linked agammaglobulinemia (XLA) patients, respectively. MethodsCytokine, MPO and MMP-9 release were quantified by ELISA, NET release and inflammasome formation by immunofluorescence. ResultsSurprisingly, in both mouse and human primary neutrophils, we observed a significant increase in NLRP3 inflammasome-dependent IL-1{beta} and NETs when BTK was absent or inhibited, whereas IL-1{beta} release was decreased in corresponding primary mouse macrophages or human PBMC, respectively. This suggests a negative regulatory role of BTK in neutrophil NLRP3 activation. Both IL-1{beta} and NET release in mouse and human primary neutrophils were strictly dependent on NLRP3, caspase-1 and, surprisingly, MMP-9. ConclusionThis highlights BTK and MMP-9 as novel and versatile inflammasome regulators and may have implications for the clinical use of BTK inhibitors. Key messagesO_LINeutrophils contribute to inflammation by release of interleukin-1{beta} and Neutrophil Extracellular Traps (NETs) via the NLRP3 inflammasome C_LIO_LIBrutons tyrosine kinase (BTK) is a negative regulator of NLRP3-mediated primary human neutrophil functions, whereas it positively regulates NLRP3 in monocytes C_LIO_LIMMP-9 is both effector and regulator of the neutrophil NLRP3 inflammasome C_LI Capsule summaryHere we report that interleukin-1{beta} and Neutrophil Extracellular Traps (NETs) release via the NLRP3 inflammasome is negatively regulated by Brutons tyrosine kinase (BTK) in primary neutrophils. Thus, targeting BTK using FDA-approved inhibitors might increase neutrophil functions. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/581733v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@482a15org.highwire.dtl.DTLVardef@1c2f1e0org.highwire.dtl.DTLVardef@195c2a5org.highwire.dtl.DTLVardef@11e1af2_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2022

naRNA is a canonical neutrophil extracellular trap (NET) component and novel inflammation-amplifying composite DAMP

Neutrophil extracellular traps (NETs) are a key antimicrobial feature of cellular innate immunity mediated by polymorphonuclear neutrophils (PMNs), the primary human leukocyte population. NETs trap and kill microbes but have also been linked to inflammation, e.g. atherosclerosis, arthritis or psoriasis by unknown mechanisms. We here characterize naRNA (NET-associated RNA), as a new canonical, abundant, and unexplored inflammatory NET component. naRNA, upon release by NET formation, drove further NET formation in naive PMN, and induced macrophage and keratinocyte activation via TLR8 in humans and Tlr13 in mice, in vitro and in vivo. Importantly, in vivo naRNA strongly drove skin inflammation, whereas genetic ablation of RNA sensing drastically ameliorated psoriatic skin inflammation. Rather than accidentally assembling with LL37 on the NET, naRNA was intracellularly pre-associated in resting neutrophils as a composite DAMP, thus highlighting NET formation as a DAMP release process. This re-defines sterile NETs as an intentionally inflammatory agent, signaling and amplifying neutrophil activation. Moreover, in the many conditions previously linked to NETs and extracellular RNA, TLR-mediated naRNA sensing emerges as both potential cause and new intervention target. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=175 SRC="FIGDIR/small/499571v4_ufig1.gif" ALT="Figure 1"> View larger version (94K): org.highwire.dtl.DTLVardef@11b866org.highwire.dtl.DTLVardef@16139ceorg.highwire.dtl.DTLVardef@1a2905org.highwire.dtl.DTLVardef@17b0e7e_HPS_FORMAT_FIGEXP M_FIG C_FIG Created with biorender.com

immunology↗

bioRxiv2022

Chitin oligomers directly promote lymphoid innate and adaptive immune cell activation

BackgroundChitin is a highly abundant N-acetyl-glucosamine (GlcNAc) polysaccharide which has been linked to immune responses in the context of fungal infections and allergic asthma, especially T helper 2 (Th2) immune responses. Unfortunately, due to the frequent use of crude chitin preparations of unknown purity and degree of polymerization there is still great uncertainty how chitin activates different parts of the human immune system. ObjectiveWe recently identified chitin oligomers of six GlcNAc units as the smallest immunologically active chitin motif and the innate immune receptor TLR2 as primary chitin sensor on human and murine myeloid cells, but the response of lymphoid cells to oligomeric chitin has not been investigated and was addressed here. MethodsFlow cytometric analysis of primary human immune cells upon stimulation with oligomeric chitin. For detailed Methods, please see the Methods section in this articles Online Repository at www.jacionline.org. ResultHere we report that chitin oligomers also activate immune responses by both primary lymphoid innate and adaptive immune cells: Notably, chitin oligomers activated Natural Killer (NK) cells and B lymphocytes. Moreover, the maturation of dendritic cells enabled CD8 T cell recall responses. ConclusionsOur results suggest that chitin oligomers not only trigger immediate innate responses in limited range of myeloid cells but exert critical activities across the entire human immune system. Key messagesChitin oligomers are microbe-associated molecular patterns involved in TLR2-dependent fungal recognition by myeloid immune cells. Here we show that lymphoid cells, most notably Natural Killer (NK) cells and B cells, are activated by oligomeric chitin. Oligomeric chitin also promotes antigen-presenting cell (APC) maturation and CD8 T cell recall responses. Capsule summaryOligomeric chitin is a novel microbe-associated molecular patterns involved in TLR2-dependent fungal recognition by myeloid innate immune cells. Here we show that lymphoid innate and adaptive immune responses are also promoted by oligomeric chitin.

immunology↗

bioRxiv2020

The failure of B cells to induce non-canonical MYD88 splice variants correlates with lymphomagenesis via sustained NF-κB signaling

Gain-of-function mutations of the TLR adaptor and oncoprotein MyD88 drive B cell lymphomagenesis via sustained NF-{kappa}B activation. In myeloid cells, sustained TLR activation and NF-{kappa}B activation lead to the induction of inhibitory MYD88 splice variants that restrain prolonged NF-{kappa}B activation. We therefore sought to investigate whether such a negative feedback loop exists in B cells. Analyzing MYD88 splice variants in normal B cells and different primary B cell malignancies, we observed that MYD88 splice variants in transformed B cells are dominated by the canonical, strongly NF-{kappa}B-activating isoform of MYD88 and contain at least three novel, so far uncharacterized signaling-competent splice isoforms. TLR stimulation in B cells unexpectedly reinforces splicing of NF-{kappa}B-promoting, canonical isoforms rather than the MyD88s, a negative regulatory isoform that is typically induced by TLRs in myeloid cells. This suggests that an essential negative feedback loop restricting TLR signaling in myeloid cells at the level of alternative splicing, is missing in B cells, rendering B cells vulnerable to sustained NF-{kappa}B activation and eventual lymphomagenesis. Our results uncover MYD88 alternative splicing as an unappreciated promoter of B cell lymphomagenesis and provide a rationale why oncogenic MYD88 mutations are exclusively found in B cells.

cancer biology↗

bioRxiv2019

BTK operates a phospho-tyrosine switch to regulate NLRP3 inflammasome activity

Activity of the NLRP3 inflammasome, a critical mediator of inflammation (1), is controlled by accessory proteins (2, 3), post-translational modifications (4, 5), cellular localization (6, 7) and oligomerization (8). How these factors relate, is unclear. We show that the established drug target, Brutons Tyrosine Kinase (BTK) (2, 9), integrates several levels of NLRP3 regulation: BTK phosphorylation of four conserved tyrosine residues, by neutralizing the charge of a polybasic linker region, weakens the interaction of NLRP3 with Golgi phospholipids and may thus guide NLRP3 cytosolic localization. BTK activity also promotes NLRP3 oligomerization and subsequent formation of inflammasomes. As NLRP3 tyrosine modification ultimately also impacts on IL-1{beta} release, we propose BTK-mediated, charge-switch-based NLRP3 regulation as a novel and therapeutically tractable step in the control of inflammation. One Sentence SummaryMulti-phosphorylation of NLRP3 by Brutons tyrosine kinase modulates NLRP3 cellular localization, inflammasome assembly, and IL-1{beta} release.

immunology↗