Biochimica et biophysica acta. Molecular cell research最新文献

Ectodomain shedding, a post-translational process mediated primarily by A Disintegrin and Metalloprotease (ADAM) family members, represents a fundamental mechanism regulating intercellular communications. By cleaving the extracellular domains of membrane-anchored cytokines, receptors, growth factors, and adhesion molecules, ADAM proteases dynamically shape cytokine signaling networks that underpin immune regulation, inflammation, and tissue homeostasis. Among these enzymes, ADAM10 and ADAM17 are key effectors whose tightly controlled activity ensures the fine-tuning of pro- and anti-inflammatory pathways. Dysregulated ADAM function perturbs cytokine gradients and receptor availability, contributing to the pathogenesis of cancer, autoimmune disorders, and chronic inflammatory diseases. In this review, we provide updated perspectives on the mechanisms governing ADAM activation and substrate selectivity, including prodomain processing, trafficking, interaction with protein partners, and modulation by inflammatory stimuli. We further highlight species-specific differences and genetic polymorphisms that influence ADAM expression and catalytic efficiency, emphasizing their translational relevance in precision medicine. Collectively, delineating the ADAM/cytokine signaling axis offers crucial insights into immune homeostasis and unveils novel opportunities for therapeutic intervention in cancer and immune-mediated diseases.

Polyphosphate (polyP) is an ancient, evolutionarily conserved inorganic polymer found in all domains of life. PolyP functions in energy storage, metal chelation, phosphate buffering, and regulation of fundamental physiological processes such as blood coagulation, bone mineralisation, and mitochondrial energy metabolism. Here, we summarize current knowledge of polyP-metabolizing enzymes. In prokaryotes, polyP synthesis is primarily catalysed by polyphosphate kinases (PPK1 and PPK2), which synthesize long-chain polymers from adenosine triphosphate (ATP) or guanosine triphosphate (GTP); notable these enzymes are absent in higher eukaryotes. In yeast, the vacuolar transporter chaperone (VTC) complex functions as a polyP polymerase-translocase, coupling synthesis with vacuolar import. In mammals, the enzymatic machinery responsible for polyP formation remains elusive, although mitochondrial F₁F₀-ATP synthase and inositol pyrophosphate signalling have been implicated. PolyP degradation is mediated by two major enzyme families: exo- and endopolyphosphatases. Members of these families - including exopolyphosphatases (PPX) and endopolyphosphatases (PPN) in yeast and bacteria as well as Nudix hydrolases and h-Prune in mammals - play key roles in maintaining intracellular phosphate homeostasis and regulating the dynamic turnover of polyP. Defining the molecular pathways of polyP synthesis and degradation will reveal novel therapeutic targets in infection, thrombosis, and metabolic disease.

Osteoclasts play an essential role as the main functional cells for bone resorption in osteomyelitis (OM). Staphylococcus aureus (SA), a prevalent pathogen causing bone infections, significantly contributes to OM by synthesizing substantial quantities of staphylococcal protein A (SpA). However, the potential mechanisms underlying the effects of SpA on osteoclastogenesis in OM need to be further explored. In our study, we found that SpA promoted the osteoclast differentiation and the inflammatory response in macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-kappa B ligand (RANKL)-treated THP-1 cells in a dose-dependent manner. Additionally, SpA-treated cells exhibited upregulation of the long non-coding RNA (lncRNA) plasmacytoma variant translocation 1 (PVT1). Silencing PVT1 reversed SpA-mediated inhibition of cell viability, and abolished SpA-induced promotion of osteoclast differentiation and the release of pro-inflammatory factors. Mechanistically, the upregulation of lncRNA PVT1 was regulated by methyltransferase-like 3 (METTL3)-mediated RNA N6-methyladenosine (m6A) modification. PVT1 increased the stability of hypoxia-inducible factor-1α (HIF-1α) by binding to its mRNA, thereby activating the HIF-1α/RANKL pathway and the pro-inflammatory NF-κB and MAPK signaling pathways. Furthermore, rescue experiments demonstrated that the silencing of METTL3-mediated upregulation of cell viability, along with the inhibition of osteoclast differentiation and inflammatory response, was reversed by overexpression of PVT1 in the presence of SpA. Meanwhile, the inhibitory effects induced by knockdown of PVT1 on osteoclast differentiation and inflammation were reversed by elevating HIF-1α. These data uncover that elevated expression of PVT1, regulated by METTL3-mediated m6A modification, activates the HIF-1α/RANKL pathway, thereby exacerbating osteoclast activation in SpA-induced OM.

Immune-mediated inflammatory diseases (IMIDs) are complex conditions commonly associated with alterations in cytokine biology. In rheumatoid arthritis (RA), the systemic activities of cytokines, such as interleukin (IL)-6, have led to the clinical introduction of targeted medicines that greatly improve patient outcomes. However, the beneficial effects of these therapies extend beyond improvements in joint pathology and often affect a range of RA-associated comorbidities that influence a patient's quality of life. For IL-6, these include impacts on cardiovascular risk, metabolic diseases, neuropsychiatric conditions, pain, fatigue, and altered tissue homeostasis. Reviewing the involvement of classical IL-6R signalling and IL-6 trans-signalling in these processes, we will examine the mechanistic basis for these comorbidities and consider the implications for therapy in RA and related IMIDs.

Sustained signaling mediated by β-arrestins (βarr) in endosomal compartments has been described for several classical G protein-coupled receptors (GPCR), yet whether adhesion GPCRs-many of which exhibit constitutive activity driven by intrinsic agonism-engage similar βarr-dependent signaling mechanisms, remains unresolved. Here, we investigated two splice variants of the synapse-organizing adhesion GPCR ADGRL1/Latrophilin-1 using overexpression approaches and G-protein biosensors in HEK293 cells. Both ADGRL1 splice variants exhibited conserved βarr recognition motifs, displayed βarr-dependent trafficking properties, recruited βarr intrinsically at the plasma membrane and early endosomes, and assembled into βarr-containing complexes. Prolonged stimulation with neurexin1β promoted receptor internalization into βarr-positive vesicles with splice variant-dependent trafficking kinetics. In contrast to the canonical paradigm of sustained signaling set by classical GPCRs, knockdown- and knockout-mediated depletion of endogenous βarr suppressed ADGRL1-mediated activation of biosensors representing all four G-protein families, phenocopying dynamin inhibition. Endosome-targeted biosensors revealed splice variant-specific βarr- and dynamin-dependent G-protein trafficking profiles, and a marked endosomal retention of active G-proteins in the absence of βarr. Consistent with a role for βarr as G-protein adaptors in endosomes, ADGRL1 activity generated splice-dependent patterns of βarr/G-protein complex assembly, shared for Gs but divergent for Gq and G13. Collectively, these data identify β-arrestins as key organizers of adhesion GPCR-mediated signaling acting through receptor endosomal priming, select complex assembly and spatiotemporal control of G protein trafficking.

The NOD-like receptor (NLR) family pyrin domain-containing protein 3 (NLRP3) is a critical cytosolic inflammasome sensor of exogenous and endogenous danger signals and is a highly attractive medicinal target against inflammatory diseases. The molecular mechanism leading to NLRP3 inflammasome activation through conformational changes of NLRP3 and apoptosis-associated speck-like protein containing a CARD (ASC) proteins remains largely enigmatic. Here, we report several bioluminescent NLRP3 inflammasome reporters based on split-luciferase complementation assay to monitor structural and molecular changes of NLRP3 inflammasome. The designed split-luciferase NLRP3 reporter showed that NLRP3 molecules are in close spatial proximity in the resting state and undergo dynamic rearrangements upon nigericin stimulation. The reporter was responsive to the probable structural changes caused by MCC950 as a specific small-molecule inhibitor of NLRP3 oligomerization. Using these reporters, our findings indicate that while serine 5 of NLRP3 plays a crucial role in NLRP3 inflammasome regulation, it does not appear to be essential for NLRP3 oligomerization. Instead, it appears to be involved in the interaction of NLRP3 and ASC. To further investigate the molecular mechanisms underlying the impact of the serine 5 on NLRP3 inflammasome function, we conducted protein docking simulations. The molecular modeling revealed that the mutation of serine 5 to aspartate indirectly disrupts the interaction between aspartate 31 of NLRP3 and arginine 5 of ASC within the NLRP3-ASC interface. These findings demonstrate the utility of the reporters for monitoring interactions within the NLRP3 inflammasome, providing a platform for measuring dynamic changes of NLRP3 inflammasome and elucidating the mode of action of therapeutic agents.