Gasdermin D maintains bone mass by rewiring the endo-lysosomal pathway of osteoclastic bone resorption.

Gasdermin D (GSDMD)-mediated pyroptosis induces immunogenic cell death and promotes inflammation. However, the functions of GSDMD in tissue homeostasis remain unclear. Here, we identify a physiological function of GSDMD in osteoclasts via a non-lytic p20-generated protein, which prevents bone loss to maintain bone homeostasis. In the late stage of RANKL-induced osteoclastogenesis, GSDMD underwent cleavage, which is dependent on RIPK1 and caspase-8/-3, to yield this p20 product. Gsdmd-deficient osteoclasts showed normal differentiation but enhanced bone resorption with excessive lysosomal activity. Mice with complete or myeloid-specific Gsdmd deletion exhibited increased trabecular bone loss and more severe aging/ovariectomy-induced osteoporosis. GSDMD p20 was preferentially localized to early endosomes and limited endo-lysosomal trafficking and maturation, relying on its oligomerization and control of phosphoinositide conversion by binding to phosphatidylinositol 3-phosphate (PI(3)P). We have thus identified an anti-osteoclastic function of GSDMD as a checkpoint for lysosomal maturation and secretion and linked this to bone homeostasis and endosome-lysosome biology.

Tumor-associated macrophages are shaped by intratumoral high potassium via Kir2.1.

The tumor microenvironment (TME) is a unique niche governed by constant crosstalk within and across all intratumoral cellular compartments. In particular, intratumoral high potassium (K+) has shown immune-suppressive potency on T cells. However, as a pan-cancer characteristic associated with local necrosis, the impact of this ionic disturbance on innate immunity is unknown. Here, we reveal that intratumoral high K+ suppresses the anti-tumor capacity of tumor-associated macrophages (TAMs). We identify the inwardly rectifying K+ channel Kir2.1 as a central modulator of TAM functional polarization in high K+ TME, and its conditional depletion repolarizes TAMs toward an anti-tumor state, sequentially boosting local anti-tumor immunity. Kir2.1 deficiency disturbs the electrochemically dependent glutamine uptake, engendering TAM metabolic reprogramming from oxidative phosphorylation toward glycolysis. Kir2.1 blockade attenuates both murine tumor- and patient-derived xenograft growth. Collectively, our findings reveal Kir2.1 as a determinant and potential therapeutic target for regaining the anti-tumor capacity of TAMs within ionic-imbalanced TME.

Kir2.1-mediated membrane potential promotes nutrient acquisition and inflammation through regulation of nutrient transporters.

Immunometabolism contributes to inflammation, but how activated macrophages acquire extracellular nutrients to fuel inflammation is largely unknown. Here, we show that the plasma membrane potential (Vm) of macrophages mediated by Kir2.1, an inwardly-rectifying K+ channel, is an important determinant of nutrient acquisition and subsequent metabolic reprogramming promoting inflammation. In the absence of Kir2.1 activity, depolarized macrophage Vm lead to a caloric restriction state by limiting nutrient uptake and concomitant adaptations in nutrient conservation inducing autophagy, AMPK (Adenosine 5'-monophosphate-activated protein kinase), and GCN2 (General control nonderepressible 2), which subsequently depletes epigenetic substrates feeding histone methylation at loci of a cluster of metabolism-responsive inflammatory genes, thereby suppressing their transcription. Kir2.1-mediated Vm supports nutrient uptake by facilitating cell-surface retention of nutrient transporters such as 4F2hc and GLUT1 by its modulation of plasma membrane phospholipid dynamics. Pharmacological targeting of Kir2.1 alleviated inflammation triggered by LPS or bacterial infection in a sepsis model and sterile inflammation in human samples. These findings identify an ionic control of macrophage activation and advance our understanding of the immunomodulatory properties of Vm that links nutrient inputs to inflammatory diseases.

Epithelial Gasdermin D shapes the host-microbial interface by driving mucus layer formation.

Goblet cells and their main secretory product, mucus, play crucial roles in orchestrating the colonic host-microbe interactions that help maintain gut homeostasis. However, the precise intracellular machinery underlying this goblet cell-induced mucus secretion remains poorly understood. Gasdermin D (GSDMD) is a recently identified pore-forming effector protein that causes pyroptosis, a lytic proinflammatory type of cell death occurring during various pathophysiological conditions. Here, we reveal an unexpected function of GSDMD in goblet cell mucin secretion and mucus layer formation. Specific deletion of Gsdmd in intestinal epithelial cells (ΔIEC) led to abrogated mucus secretion with a concomitant loss of the mucus layer. This impaired colonic mucus layer in GsdmdΔIEC mice featured a disturbed host-microbial interface and inefficient clearance of enteric pathogens from the mucosal surface. Mechanistically, stimulation of goblet cells activates caspases to process GSDMD via reactive oxygen species production; in turn, this activated GSDMD drives mucin secretion through calcium ion-dependent scinderin-mediated cortical F-actin disassembly, which is a key step in granule exocytosis. This study links epithelial GSDMD to the secretory granule exocytotic pathway and highlights its physiological nonpyroptotic role in shaping mucosal homeostasis in the gut.

Ubiquitination of NLRP3 by gp78/Insig-1 restrains NLRP3 inflammasome activation.

The NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome plays a pivotal role in defending the host against infection as well as sterile inflammation. Activation of the NLRP3 inflammasome is critically regulated by a de-ubiquitination mechanism, but little is known about how ubiquitination restrains NLRP3 activity. Here, we showed that the membrane-bound E3 ubiquitin ligase gp78 mediated mixed ubiquitination of NLRP3, which inhibited NLRP3 inflammasome activation by suppressing the oligomerization and subcellular translocation of NLRP3. In addition, the endoplasmic reticulum membrane protein insulin-induced gene 1 (Insig-1) was required for this gp78-NLRP3 interaction and gp78-mediated NLRP3 ubiquitination. gp78 or Insig-1 deficiency in myeloid cells led to exacerbated NLRP3 inflammasome-dependent inflammation in vivo, including lipopolysaccharide-induced systemic inflammation and alum-induced peritonitis. Taken together, our study identifies gp78-mediated NLRP3 ubiquitination as a regulatory mechanism that restrains inflammasome activation and highlights NLRP3 ubiquitination as a potential therapeutic target for inflammatory diseases.

AKT controls NLRP3 inflammasome activation by inducing DDX3X phosphorylation.

The NLRP3 inflammasome, a critical component of the innate immune system, induces caspase-1 activation and interleukin-1ß maturation and drives cell fate toward pyroptosis. However, the mechanism of NLRP3 inflammasome activation still remains elusive. Here we provide evidence that AKT regulates NLRP3 inflammasome activation. Upon NLRP3 activation, AKT activity is inhibited by second stimulus-induced reactive oxygen species. In contrast, AKT activation leads to NLRP3 inhibition and improved mitochondrial fitness. Mechanistically, AKT induces the phosphorylation of the DDX3X (DEAD-box helicase 3, X-linked), a recently identified NLRP3 inflammasome component, and impairs the interaction between DDX3X and NLRP3. Furthermore, an AKT agonist reduces NLRP3-dependent inflammation in two in vivo models of LPS-induced sepsis and Alum-induced peritonitis. Altogether, our study highlights an important role of AKT in controlling NLRP3 inflammasome activation.

An Efficient Ensemble Binarized Deep Neural Network on Chip with Perception-Control Integrated.

Lightweight UAVs equipped with deep learning models have become a trend, which can be deployed for automatic navigation in a wide range of civilian and military missions. However, real-time applications usually need to process a large amount of image data, which leads to a very large computational complexity and storage consumption, and restricts its deployment on resource-constrained embedded edge devices. To reduce the computing requirements and storage occupancy of the neural network model, we proposed the ensemble binarized DroNet (EBDN) model, which implemented the reconstructed DroNet with the binarized and ensemble learning method, so that the model size of DroNet was effectively compressed, and ensemble learning method was used to overcome the defect of the poor performance of the low-precision network. Compared to the original DroNet, EBDN saves more than 7 times of memory footprint with similar model accuracy. Meanwhile, we also proposed a novel and high-efficiency hardware architecture to realize the EBDN on the chip (EBDNoC) system, which perfectly realizes the mapping of an algorithm model to hardware architecture. Compared to other solutions, the proposed architecture achieves about 10.21 GOP/s/kLUTs resource efficiency and 208.1 GOP/s/W energy efficiency, while also providing a good trade-off between model performance and resource utilization.

Histone Deacetylase 3 Couples Mitochondria to Drive IL-1ß-Dependent Inflammation by Configuring Fatty Acid Oxidation.

Immune cell function depends on specific metabolic programs dictated by mitochondria, including nutrient oxidation, macromolecule synthesis, and post-translational modifications. Mitochondrial adaptations have been linked to acute and chronic inflammation, but the metabolic cues and precise mechanisms remain unclear. Here we reveal that histone deacetylase 3 (HDAC3) is essential for shaping mitochondrial adaptations for IL-1ß production in macrophages through non-histone deacetylation. In vivo, HDAC3 promoted lipopolysaccharide-induced acute inflammation and high-fat diet-induced chronic inflammation by enhancing NLRP3-dependent caspase-1 activation. HDAC3 configured the lipid profile in stimulated macrophages and restricted fatty acid oxidation (FAO) supported by exogenous fatty acids for mitochondria to acquire their adaptations and depolarization. Rather than affecting nuclear gene expression, HDAC3 translocated to mitochondria to deacetylate and inactivate an FAO enzyme, mitochondrial trifunctional enzyme subunit α. HDAC3 may serve as a controlling node that balances between acquiring mitochondrial adaptations and sustaining their fitness for IL-1ß-dependent inflammation.