ZDHHC5-mediated NLRP3 palmitoylation promotes NLRP3-NEK7 interaction and inflammasome activation

Palmitoylation of NLRP3 Modulates Inflammasome Activation and Inflammatory Bowel Disease Development

Aberrant activity of NLRP3 has been shown associations with severe diseases. Palmitoylation is a kind of protein post-translational modification, which has been shown to regulate cancer development and the innate immune system. Here, we showed that NLRP3 is palmitoylated at Cys419 and that palmitoyltransferase ZDHHC17 is the predominant enzyme that mediates NLRP3 palmitoylation and promotes NLRP3 activation by interacting with NLRP3 and facilitating NIMA-related kinase 7 (NEK7)-NLRP3 interactions. Blockade of NLRP3 palmitoylation by a palmitoylation inhibitor, 2-bromopalmitate, effectively inhibited NLRP3 activation in vitro. Also, in a dextran sulfate sodium-induced colitis model in mice, 2-bromopalmitate application could attenuate weight loss, improve the survival rate, and rescue pathological changes in the colon of mice. Overall, our study reveals that palmitoylation of NLPR3 modulates inflammasome activation and inflammatory bowel disease development. We propose that drugs targeting NLRP3 palmitoylation could be promising candidates in the treatment of NLRP3-mediated inflammatory diseases.

FDA-approved disulfiram inhibits the NLRP3 inflammasome by regulating NLRP3 palmitoylation

The NLRP3 inflammasome is dysregulated in autoinflammatory disorders caused by inherited mutations and contributes to the pathogenesis of several chronic inflammatory diseases. In this study, we discovered that disulfiram, a safe US Food and Drug Administration (FDA)-approved drug, specifically inhibits the NLRP3 inflammasome but not the NLRC4 or AIM2 inflammasomes. Disulfiram suppresses caspase-1 activation, ASC speck formation, and pyroptosis induced by several stimuli that activate NLRP3. Mechanistically, NLRP3 is palmitoylated at cysteine 126, a modification required for its localization to the trans-Golgi network and inflammasome activation, which was inhibited by disulfiram. Administration of disulfiram to animals inhibited the NLRP3, but not NLRC4, inflammasome in vivo. Our study uncovers a mechanism by which disulfiram targets NLRP3 and provides a rationale for using a safe FDA-approved drug for the treatment of NLRP3-associated inflammatory diseases.

Breaking the vicious cycle: Targeting the NLRP3 inflammasome for treating sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is a collection of clinical syndromes resulting from sepsis and characterized by widespread brain dysfunction. The high prevalence of SAE has adverse outcomes on the clinical management and prognosis of sepsis patients. However, currently, there are no effective treatments to ameliorate SAE. The pathogenesis of SAE is complex, including neuroinflammation and microglia activation, destruction of the blood-brain barrier (BBB), neurotransmitter dysfunction, cerebral metabolism and mitochondrial impairment, accumulation of amyloid beta and tauopathy, complement activation, among others. Furthermore, these mechanisms intertwine with each other, further complicating the comprehension of SAE. Among them, neuroinflammation mediated by hyperactivated microglia is considered the primary etiology of SAE. This instigates a detrimental cycle wherein BBB permeability escalates, facilitating direct damage to the central nervous system (CNS) by various neurotoxic substances. Activation of the NLRP3 inflammasome, situated within microglia, can be triggered by diverse danger signals, leading to cell pyroptosis, apoptosis, and tauopathy. These complex processes intricately regulate the onset and progression of neuroinflammation. In this review, we focus on elucidating the inhibitory regulatory mechanism of the NLRP3 inflammasome in microglia, which ultimately manifests as suppression of the inflammatory response. Our ultimate objective is to augment comprehension regarding the role of microglial NLRP3 inflammasome as we explore potential targets for therapeutic interventions against SAE.

Effect and mechanism of T lymphocytes on human induced pluripotent stem cell-derived cardiomyocytes via Proteomics

BACKGROUND

Abnormalities in T cell activation play an important role in the pathogenesis of myocarditis, and persistent T cell responses can lead to autoimmunity and chronic cardiac inflammation, as well as even dilated cardiomyopathy. Although previous work has examined the role of T cells in myocarditis in animal models, the specific mechanism for human cardiomyocytes has not been investigated.

METHODS

In this study, we constructed the human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and established the T cell-mediated cardiac injury model by co-culturing with activated CD4 + T or CD8 + T cells that were isolated from peripheral mononuclear blood to elucidate the pathogenesis of myocardial cell injury caused by inflammation.

RESULTS

By combination of quantitative proteomics with tissue and cell immunofluorescence examination, we established a proteome profile of inflammatory myocardia from hiPSC-CMs with obvious cardiomyocyte injury and increased levels of lactate dehydrogenase content, creatine kinase isoenzyme MB and cardiac troponin. A series of molecular dysfunctions of hiPSC-CMs was observed and indicated that CD4 + cells could produce direct cardiomyocyte injury by activating the NOD-like receptor signals pathway.

CONCLUSIONS

The data presented in our study established a proteome map of inflammatory myocardial based on hiPSC-CMs injury model. These results can provide guidance in the discovery of improved clinical treatments for myocarditis.

Fatty acid synthesis promotes inflammasome activation through NLRP3 palmitoylation

Despite its significance, the role of lipid metabolism in NLRP3 inflammasome remains elusive. Here, we reveal a critical role for fatty acid synthase (FASN) in NLRP3 inflammasome activation. We demonstrate that pharmacological or genetic depletion of FASN dampens NLRP3 activation in primary mouse and human macrophages and in mice. This disruption in NLRP3 activation is contingent upon FASN activity. Accordingly, abolishing cellular palmitoylation, a post-translational modification in which the FASN product palmitate is reversibly conjugated to cysteine residues of target proteins, blunts inflammasome signaling. Correspondingly, an acyl-biotin exchange assay corroborated NLRP3 palmitoylation. Mechanistically, Toll-like receptor (TLR) ligation introduces palmitoylation at NLRP3 Cys898, permitting NLRP3 translocation to dispersed trans-Golgi network (dTGN) vesicles, the site of inflammasome assembly, upon NLRP3 activation. Accordingly, the NLRP3 Cys898 mutant exhibits reduced palmitoylation, limited translocation to the dTGN compartment, and diminished inflammasome activation. These results underscore mechanistic insights through which lipid metabolism licenses NLRP3 inflammasome assembly and activation.

Enzymatic control of intermolecular interactions for generating synthetic nanoarchitectures in cellular environment

Nanoarchitectonics, as a technology to arrange nano-sized structural units such as molecules in a desired configuration, requires nano-organization, which usually relies on intermolecular interactions. This review briefly introduces the development of using enzymatic reactions to control intermolecular interactions for generating artificial nanoarchitectures in a cellular environment. We begin the discussion with the early examples and uniqueness of enzymatically controlled self-assembly. Then, we describe examples of generating intracellular nanostructures and their relevant applications. Subsequently, we discuss cases of forming nanostructures on the cell surface via enzymatic reactions. Following that, we highlight the use of enzymatic reactions for creating intercellular nanostructures. Finally, we provide a summary and outlook on the promises and future direction of this strategy. Our aim is to give an updated introduction to the use of enzymatic reaction in regulating intermolecular interactions, a phenomenon ubiquitous in biology but relatively less explored by chemists and materials scientists. Our goal is to stimulate new developments in this simple and versatile approach for addressing societal needs.

Mechanisms and functions of protein S-acylation

Over the past two decades, protein S-acylation (often referred to as S-palmitoylation) has emerged as an important regulator of vital signalling pathways. S-Acylation is a reversible post-translational modification that involves the attachment of a fatty acid to a protein. Maintenance of the equilibrium between protein S-acylation and deacylation has demonstrated profound effects on various cellular processes, including innate immunity, inflammation, glucose metabolism and fat metabolism, as well as on brain and heart function. This Review provides an overview of current understanding of S-acylation and deacylation enzymes, their spatiotemporal regulation by sophisticated multilayered mechanisms, and their influence on protein function, cellular processes and physiological pathways. Furthermore, we examine how disruptions in protein S-acylation are associated with a broad spectrum of diseases from cancer to autoinflammatory disorders and neurological conditions.

Post-translational control of NLRP3 inflammasome signaling

Inflammasomes serve as critical sensors for disruptions to cellular homeostasis, with inflammasome assembly leading to inflammatory caspase activation, gasdermin cleavage, and cytokine release. While the canonical pathways leading to priming, assembly, and pyroptosis are well characterized, recent work has begun to focus on the role of post-translational modifications (PTMs) in regulating inflammasome activity. A diverse array of PTMs, including phosphorylation, ubiquitination, SUMOylation, acetylation, and glycosylation, exert both activating and inhibitory influences on members of the inflammasome cascade through effects on protein-protein interactions, stability, and localization. Dysregulation of inflammasome activation is associated with a number of inflammatory diseases, and evidence is emerging that aberrant modification of inflammasome components contributes to this dysregulation. This review provides insight into PTMs within the NLRP3 inflammasome pathway and their functional consequences on the signaling cascade and highlights outstanding questions that remain regarding the complex web of signals at play.

When pyro(ptosis) meets palm(itoylation)

Pyroptosis, a programmed cell death process, is vital for the immune response against microbial infections and internal danger signals. Recent studies have highlighted the importance of protein palmitoylation, a modification that involves attaching palmitate to cysteine residues, in regulating key proteins involved in pyroptosis. Palmitoylation of cGAS at residue C474 by ZDHHC18 affects its enzymatic activity and DNA binding ability. Similarly, ZDHHC9 promotes cGAS activity through palmitoylation at residues C404/405. NLRP3 palmitoylation at residue C844, mediated by ZDHHC12, impacts its stability and interactions with other proteins, crucial for activating the NLRP3 inflammasome and triggering inflammation. However, the role of ZDHHC5 in NLRP3 palmitoylation remains uncertain due to conflicting findings. Palmitoylation at C88/91 is essential for STING activation and induction of type I interferons. It modulates the formation of multimeric complexes and downstream signaling pathways. GSDMD palmitoylation at C191 is necessary for pore formation and membrane translocation, while GSDME palmitoylation at C407/408 is associated with drug-induced pyroptosis. Moreover, palmitoylation of NOD1 and NOD2 influences their membrane recruitment and immune signaling pathways in response to bacterial peptidoglycans, acting as upstream regulators of pyroptosis. This review summarizes the important roles for palmitoylation in regulating the function of key pyroptosis-related proteins, shedding light on the intricate mechanisms governing immune responses and inflammation.

Targeting epigenetic and post-translational modifications regulating pyroptosis for the treatment of inflammatory diseases

Inflammatory diseases, including infectious diseases, diabetes-related diseases, arthritis-related diseases, neurological diseases, digestive diseases, and tumor, continue to threaten human health and impose a significant financial burden despite advancements in clinical treatment. Pyroptosis, a pro-inflammatory programmed cell death pathway, plays an important role in the regulation of inflammation. Moderate pyroptosis contributes to the activation of native immunity, whereas excessive pyroptosis is associated with the occurrence and progression of inflammation. Pyroptosis is complicated and tightly controlled by various factors. Accumulating evidence has confirmed that epigenetic modifications and post-translational modifications (PTMs) play vital roles in the regulation of pyroptosis. Epigenetic modifications, which include DNA methylation and histone modifications (such as methylation and acetylation), and post-translational modifications (such as ubiquitination, phosphorylation, and acetylation) precisely manipulate gene expression and protein functions at the transcriptional and post-translational levels, respectively. In this review, we summarize the major pathways of pyroptosis and focus on the regulatory roles and mechanisms of epigenetic and post-translational modifications of pyroptotic components. We also illustrate these within pyroptosis-associated inflammatory diseases. In addition, we discuss the effects of novel therapeutic strategies targeting epigenetic and post-translational modifications on pyroptosis, and provide prospective insight into the regulation of pyroptosis for the treatment of inflammatory diseases.

Deacylases-structure, function, and relationship to diseases

Reversible S-acylation plays a pivotal role in various biological processes, modulating protein functions such as subcellular localization, protein stability/activity, and protein-protein interactions. These modifications are mediated by acyltransferases and deacylases, among which the most abundant modification is S-palmitoylation. Growing evidence has shown that this rivalrous pair of modifications, occurring in a reversible cycle, is essential for various biological functions. Aberrations in this process have been associated with various diseases, including cancer, neurological disorders, and immune diseases. This underscores the importance of studying enzymes involved in acylation and deacylation to gain further insights into disease pathogenesis and provide novel strategies for disease treatment. In this Review, we summarize our current understanding of the structure and physiological function of deacylases, highlighting their pivotal roles in pathology. Our aim is to provide insights for further clinical applications.

A palmitoylation-depalmitoylation relay spatiotemporally controls GSDMD activation in pyroptosis

Gasdermin D (GSDMD) is the executor of pyroptosis, which is important for host defence against pathogen infection. Following activation, caspase-mediated cleavage of GSDMD releases an amino-terminal fragment (GSDMD-NT), which oligomerizes and forms pores in the plasma membrane, leading to cell death and release of proinflammatory cytokines. The spatial and temporal regulation of this process in cells remains unclear. Here we identify GSDMD as a substrate for reversible S-palmitoylation on C192 during pyroptosis. The palmitoyl acyltransferase DHHC7 palmitoylates GSDMD to direct its cleavage by caspases. Subsequently, palmitoylation of GSDMD-NT promotes its translocation to the plasma membrane, where APT2 depalmitoylates GSDMD-NT to unmask the C192 residue and promote GSDMD-NT oligomerization. Perturbation of either palmitoylation or depalmitoylation suppresses pyroptosis, leading to increased survival of mice with lipopolysaccharide-induced lethal septic shock and increased sensitivity to bacterial infection. Our findings reveal a model through which a palmitoylation-depalmitoylation relay spatiotemporally controls GSDMD activation during pyroptosis.

NLRP3 Cys126 palmitoylation by ZDHHC7 promotes inflammasome activation

Nucleotide oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome hyperactivation contributes to many human chronic inflammatory diseases, and understanding how NLRP3 inflammasome is regulated can provide strategies to treat inflammatory diseases. Here, we demonstrate that NLRP3 Cys126 is palmitoylated by zinc finger DHHC-type palmitoyl transferase 7 (ZDHHC7), which is critical for NLRP3-mediated inflammasome activation. Perturbing NLRP3 Cys126 palmitoylation by ZDHHC7 knockout, pharmacological inhibition, or modification site mutation diminishes NLRP3 activation in macrophages. Furthermore, Cys126 palmitoylation is vital for inflammasome activation in vivo. Mechanistically, ZDHHC7-mediated NLRP3 Cys126 palmitoylation promotes resting NLRP3 localizing on the trans-Golgi network (TGN) and activated NLRP3 on the dispersed TGN, which is indispensable for recruitment and oligomerization of the adaptor ASC (apoptosis-associated speck-like protein containing a CARD). The activation of NLRP3 by ZDHHC7 is different from the termination effect mediated by ZDHHC12, highlighting versatile regulatory roles of S-palmitoylation. Our study identifies an important regulatory mechanism of NLRP3 activation that suggests targeting ZDHHC7 or the NLRP3 Cys126 residue as a potential therapeutic strategy to treat NLRP3-related human disorders.

The NLR family of innate immune and cell death sensors

Nucleotide-binding oligomerization domain (NOD)-like receptors, also known as nucleotide-binding leucine-rich repeat receptors (NLRs), are a family of cytosolic pattern recognition receptors that detect a wide variety of pathogenic and sterile triggers. Activation of specific NLRs initiates pro- or anti-inflammatory signaling cascades and the formation of inflammasomes-multi-protein complexes that induce caspase-1 activation to drive inflammatory cytokine maturation and lytic cell death, pyroptosis. Certain NLRs and inflammasomes act as integral components of larger cell death complexes-PANoptosomes-driving another form of lytic cell death, PANoptosis. Here, we review the current understanding of the evolution, structure, and function of NLRs in health and disease. We discuss the concept of NLR networks and their roles in driving cell death and immunity. An improved mechanistic understanding of NLRs may provide therapeutic strategies applicable across infectious and inflammatory diseases and in cancer.