Clare Elizabeth Bryant

Innate immune signalling is uniquely driven through the formation of supramolecular organising centres (SMOCs), which couple receptor activation with downstream effector recruitment. The adaptor protein TRIF coordinates interferon, inflammatory, and cell death responses downstream of TLR3 and TLR4 activation, yet exactly how this protein drives such diverse outputs remains unresolved. Recent structural studies of recombinant TRIF, alongside single-molecule fluorescence imaging of endogenously expressed TRIF in live cells, reveal that TRIF assembles into complexes with heterogeneous size and morphology, with monomeric and low-order complexes associated with early-phase interferon signalling and mature, RIPK1-containing complexes associated with NF-κB activation. This review explores how differences in the structural architecture of the TRIFosome, from TIR-mediated oligomerisation through to RHIM-mediated cross-linking, may underlie this divergence in signalling outcome. Finally, this review discusses the translational opportunities that coordinating scaffold assembly with downstream function presents, including structure-selective therapeutics capable of shifting the balance between TRIF’s signalling outputs and novel diagnostics that could be built on TRIFosome heterogeneity as a molecular fingerprint of disease.

Macrophages exhibit a range of time-dependent responses to external stimuli, but at the single cell-level how receptor input is converted into heterogeneous inflammatory outputs, and how termination occurs remains unclear. Toll-like receptor (TLR) signaling is initiated through supramolecular protein assemblies. In this work, using macrophages with endogenously tagged myeloid differentiation primary response 88 (MyD88), and in primary mouse macrophages, we identify pre-existing heterogeneity in MyD88 abundance as a hidden single-cell variable that shapes the threshold for productive MyD88 assembly and downstream signaling. Strong agonism converts this basal heterogeneity into rapid growth of large MyD88 assemblies, robust NFκB activation, cytokine production, and induction of negative regulators. In contrast, weak agonism produces delayed and less efficient assembly, low-amplitude cytokine output, and weaker feedback engagement, resulting in persistent low-output signaling. Parallel transcriptomic analysis of Alzheimer's disease (AD) brain tissue, and blood samples across additional acute and chronic inflammatory disease cohorts, reveals a consistent, disproportionate activation-relative-to-feedback signature, suggesting incomplete activation-feedback coupling as a correlative but recurring feature of chronic inflammatory disease.

Toll-like receptors (TLRs) drive innate immunity via assembly of macromolecular signal transduction platforms [supramolecular organizing centers (SMOCs)] coordinated by adaptor proteins such as Toll/interleukin-1 receptor (IL-1R) domain–containing adaptor-inducing interferon-β (TRIF), but whether oligomeric TRIFosomes form is unknown. Here, using cryo–electron microscopy and biophysical characterization of full-length TRIF in vitro, we show that it forms filamentous oligomers, which associate with the TRIF signaling partners receptor interacting protein 1 (RIP1) and RIP3 kinases, suggesting that oligomeric TRIFosomes could form. Endogenous TRIF, however, is predominantly monomeric in the absence of ligand, only forming TRIFosome oligomers in macrophages after stimulation of TLR4 or TLR3 when large, macromolecular signaling complexes form. TRIFosomes are fully formed 45 min after TLR3 or 60 min after TLR4 stimulation, commensurate with activation of nuclear factor κB in these cells. TLR3/4 activation triggers rapid interferon signaling prior to TRIFosome formation through monomeric TRIF, unexpectedly suggesting that a macromolecular platform of TRIF is not required to drive this signaling pathway. Collectively, these data show TRIFosome macromolecular platform formation and, unexpectedly, that TLR signaling can be SMOC-independent in addition to being SMOC-dependent.

The Concise Guide to Pharmacology 2025/26 marks the seventh edition in this series of biennial publications in the British Journal of Pharmacology. Presented in landscape format, the guide provides a comparative overview of the pharmacology of drug target families. The concise nature of the Concise Guide refers to the style of presentation, being clear, accessible, and well‐structured, rather than the scope of the content, which spans approximately 500 pages. The Concise Guide summarises the key pharmacological properties of around 1900 human drug targets, and nearly 7000 interactions, involving around 4400 ligands. While the content is a substantially condensed version of the more detailed information and links available at the www.guidetopharmacology.org website, the printed guide serves as a permanent, citable, point‐in‐time record, that remains stable despite ongoing updates to the online database. The full contents of this publication can be found at https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/bph.70233 . The Concise Guides provide expert‐curated recommendations of ‘Gold Standard’ selective pharmacological tools, available either commercially or as donations, which enable the identification of individual drug targets or families of drug targets. While the Concise Guide offers a more streamlined overview, more comprehensive information, including detailed pharmacological profiles and links to multiple online databases, is available through the Guide to Pharmacology website. The 2025/26 edition of the Concise Guide is based on material current as of mid‐2025, and supersedes all previous editions, including the 2023/24 Guide, and earlier Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC‐IUPHAR), and as such provides official IUPHAR classification and nomenclature for human drug targets, where applicable. Catalytic receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein‐coupled receptors, ion channels, nuclear hormone receptors, enzymes and transporters. Each section includes nomenclature guidance, concise summaries, information of the best available pharmacological tools, key references, and suggestions for further reading.

Impaired mitochondrial bioenergetics in macrophages promotes hyperinflammatory cytokine responses, but whether inherited mtDNA mutations drive similar phenotypes is unknown. Here, we profiled macrophages harbouring a heteroplasmic mitochondrial tRNA ^Ala mutation ( m.5019A > G ) to address this question. These macrophages exhibit combined respiratory chain defects, reduced oxidative phosphorylation, disrupted cristae architecture, and compensatory metabolic adaptations in central carbon metabolism. Upon inflammatory activation, m.5019A > G macrophages produce elevated type I interferon (IFN), while exhibiting reduced pro-inflammatory cytokines and oxylipins. Mechanistically, suppression of pro-IL-1β and COX2 requires autocrine IFN-β signalling. IFN-β induction is biphasic: an early TLR4-IRF3 driven phase, and a later response involving mitochondrial nucleic acids and the cGAS-STING pathway. In vivo, lipopolysaccharide (LPS) challenge of m.5019A > G mice results in elevated type I IFN signalling and exacerbated sickness behaviour. These findings reveal that a pathogenic mtDNA mutation promotes an imbalanced innate immune response, which has potential implications for the progression of pathology in mtDNA disease patients.

During bacterial infection both the host cell and its invader must rapidly divert resources to synthesize specific proteins. For the host, these factors may be needed for innate immune responses, including programmed cell death, and in the bacteria newly synthesized proteins may include survival factors that counteract host defences. Salmonella is an important bacterial pathogen that invades and multiplies within host cells. It is well established that epithelial cell invasion is dependent upon the Salmonella pathogenicity island 1 (SPI-1) type III injectisome, a biological needle that penetrates host cells and injects effectors that promote bacterial internalization. However, the importance of the SPI-1 injectisome in infection of professional phagocytes such as macrophages, the predominant host cell type supporting systemic infection, is less clear. Through time-resolved parallel transcriptomic and translatomic studies of macrophage infection, we reveal SPI-1 injectisome-dependent infection of macrophages triggers rapid translation of transcription factors, including Early Growth Response 1 (EGR1). Despite EGR1’s short half-life, its swift synthesis, driven by untranslated regions of its mRNA, is sufficient to inhibit the transcription of pro-inflammatory genes; this restrains inflammation and macrophage death which would otherwise abort systemic infection. This demonstrates the importance of translational activation in host–pathogen dynamics during bacterial infection.

Pattern Recognition Receptors (PRRs, [118]) (nomenclature as agreed by NC-IUPHAR sub-committee on Pattern Recognition Receptors, [21]) participate in the innate immune response to microbial agents, the stimulation of which leads to activation of intracellular enzymes and regulation of gene transcription. PRRs express multiple leucine-rich regions to bind a range of microbially-derived ligands, termed PAMPs or pathogen-associated molecular patterns or endogenous ligands, termed DAMPS or damage-associated molecular patterns. These include peptides, carbohydrates, peptidoglycans, lipoproteins, lipopolysaccharides, and nucleic acids. PRRs include both cell-surface and intracellular proteins. PRRs may be divided into signalling-associated members, identified here, and endocytic members, the function of which appears to be to recognise particular microbial motifs for subsequent cell attachment, internalisation and destruction. Some are involved in inflammasome formation, and modulation of IL-1β cleavage and secretion, and others in the initiation of the type I interferon response. PRRs included in the Guide To PHARMACOLOGY are:Catalytic PRRs (see links below this overview)Toll-like receptors (TLRs)Nucleotide-binding oligomerization domain, leucine-rich repeat containing receptors (NLRs, also known as NOD (Nucleotide oligomerisation domain)-like receptors)RIG-I-like receptors (RLRs)Caspase 4 and caspase 5 Non-catalytic PRRsAbsent in melanoma (AIM)-like receptors (ALRs)C-type lectin-like receptors (CLRs)Other pattern recognition receptorsAdvanced glycosylation end-product specific receptor (RAGE)

Pattern Recognition Receptors (PRRs, [118]) (nomenclature as agreed by NC-IUPHAR sub-committee on Pattern Recognition Receptors, [21]) participate in the innate immune response to microbial agents, the stimulation of which leads to activation of intracellular enzymes and regulation of gene transcription. PRRs express multiple leucine-rich regions to bind a range of microbially-derived ligands, termed PAMPs or pathogen-associated molecular patterns or endogenous ligands, termed DAMPS or damage-associated molecular patterns. These include peptides, carbohydrates, peptidoglycans, lipoproteins, lipopolysaccharides, and nucleic acids. PRRs include both cell-surface and intracellular proteins. PRRs may be divided into signalling-associated members, identified here, and endocytic members, the function of which appears to be to recognise particular microbial motifs for subsequent cell attachment, internalisation and destruction. Some are involved in inflammasome formation, and modulation of IL-1β cleavage and secretion, and others in the initiation of the type I interferon response. PRRs included in the Guide To PHARMACOLOGY are:Catalytic PRRs (see links below this overview)Toll-like receptors (TLRs)Nucleotide-binding oligomerization domain, leucine-rich repeat containing receptors (NLRs, also known as NOD (Nucleotide oligomerisation domain)-like receptors)RIG-I-like receptors (RLRs)Caspase 4 and caspase 5 Non-catalytic PRRsAbsent in melanoma (AIM)-like receptors (ALRs)C-type lectin-like receptors (CLRs)Other pattern recognition receptorsAdvanced glycosylation end-product specific receptor (RAGE)

The gut microbiome modulates immunotherapy treatment responses, and this may explain why immune checkpoint inhibitors, such as anti-PD-1, are only effective in some patients. Previous studies correlated lipopolysaccharide (LPS)-producing gut microbes with poorer prognosis; however, LPS from diverse bacterial species can range from immunostimulatory to inhibitory. Here, by functionally analysing faecal metagenomes from 112 patients with melanoma, we found that a subset of LPS-producing bacteria encoding immunostimulatory hexa-acylated LPS was enriched in microbiomes of clinical responders. In an implanted tumour mouse model of anti-PD-1 treatment, microbiota-derived hexa-acylated LPS was required for effective anti-tumour immune responses, and LPS-binding antibiotics and a small-molecule TLR4 antagonist abolished anti-PD-1 efficacy. Conversely, oral administration of hexa-acylated LPS to mice significantly augmented anti-PD-1-mediated anti-tumour immunity. Penta-acylated LPS did not improve anti-PD-1 efficacy in vivo and inhibited hexa-acylated LPS-induced immune activation in vitro. Microbiome hexa-acylated LPS therefore represents an accessible predictor and potential enhancer of immunotherapy responses.