Gasdermins gone wild: new roles for GSDMs in regulating cellular homeostasis

Pyroptosis: A spoiler of peaceful coexistence between cells in degenerative bone and joint diseases

BACKGROUND

As people age, degenerative bone and joint diseases (DBJDs) become more prevalent. When middle-aged and elderly people are diagnosed with one or more disorders such as osteoporosis (OP), osteoarthritis (OA), and intervertebral disc degeneration (IVDD), it often signals the onset of prolonged pain and reduced functionality. Chronic inflammation has been identified as the underlying cause of various degenerative diseases, including DBJDs. Recently, excessive activation of pyroptosis, a form of programed cell death (PCD) mediated by inflammasomes, has emerged as a primary driver of harmful chronic inflammation. Consequently, pyroptosis has become a potential target for preventing and treating DBJDs.

AIM OF REVIEW

This review explored the physiological and pathological roles of the pyroptosis pathway in bone and joint development and its relation to DBJDs. Meanwhile, it elaborated the molecular mechanisms of pyroptosis within individual cell types in the bone marrow and joints, as well as the interplay among different cell types in the context of DBJDs. Furthermore, this review presented the latest compelling evidence supporting the idea of regulating the pyroptosis pathway for DBJDs treatment, and discussed the potential, limitations, and challenges of various therapeutic strategies involving pyroptosis regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In summary, an interesting identity for the unregulated pyroptosis pathway in the context of DBJDs was proposed in this review, which was undertaken as a spoiler of peaceful coexistence between cells in a degenerative environment. Over the extended course of DBJDs, pyroptosis pathway perpetuated its activity through crosstalk among pyroptosis cascades in different cell types, thus exacerbating the inflammatory environment throughout the entire bone marrow and joint degeneration environment. Correspondingly, pyroptosis regulation therapy emerged as a promising option for clinical treatment of DBJDs.

Metabolic Inhibition Induces Pyroptosis in Uveal Melanoma

Few treatment options are available for patients with metastatic uveal melanoma. Although the bispecific tebentafusp is FDA approved, immunotherapy has largely failed, likely given the poorly immunogenic nature of uveal melanoma. Treatment options that improve the recognition of uveal melanoma by the immune system may be key to reducing disease burden. We investigated whether uveal melanoma has the ability to undergo pyroptosis, a form of immunogenic cell death. Publicly available patient data and cell line analysis showed that uveal melanoma expressed the machinery needed for pyroptosis, including gasdermins D and E (GSDMD and E), caspases 1, 3, 4, and 8, and ninjurin-1. We induced cleavage of GSDMs in uveal melanoma cell lines treated with metabolic inhibitors. In particular, the carnitine palmitoyltransferase 1 (CPT1) inhibitor, etomoxir, induced propidium iodide uptake, caspase 3 cleavage, and the release of HMGB1 and IL-1β, indicating that the observed cleavage of GSDMs led to pyroptosis. Importantly, a gene signature reflecting CPT1A activity correlated with poor prognosis in patients with uveal melanoma and knockdown of CPT1A also induced pyroptosis. Etomoxir-induced pyroptosis was dependent on GSDME but not on GSDMD, and a pyroptosis gene signature correlated with immune infiltration and improved response to immune checkpoint blockade in a set of patients with uveal melanoma. Together, these data show that metabolic inhibitors can induce pyroptosis in uveal melanoma cell lines, potentially offering an approach to enhance inflammation-mediated immune targeting in patients with metastatic uveal melanoma. Implications: Induction of pyroptosis by metabolic inhibition may alter the tumor immune microenvironment and improve the efficacy of immunotherapy in uveal melanoma.

GSDMD Deficiency Attenuates the Development of Ascending Aortic Dissections in a Novel Mouse Model

BACKGROUND

Mechanisms driving the development of type A aortic dissection (TAD) are currently poorly understood, and animal models of spontaneous TAD are limited. In the present study, we developed a novel mouse TAD model and evaluated the role of GSDMD (gasdermin D) in TAD development.

METHODS

TADs were created by treating the ascending aorta of adult C57BL/6J mice with Act E (active elastase) and β-aminopropionitrile. The temporal progress of the TAD pathology was rigorously characterized by histological evaluation and scanning electron microscopy, while potential mechanisms were explored using bulk RNA sequencing of specimens collected at multiple time points. With this novel TAD model, we conducted additional experiments to investigate the impact of GSDMD deficiency on TAD formation.

RESULTS

Ascending aortas challenged with Act E and β-aminopropionitrile developed pathology featuring the early onset of intimomedial tears (complete penetration) and intramural hematomas, followed by progressive medial loss and aortic dilation. Ingenuity pathway analysis and functional annotation of differentially expressed genes suggested that a unique inflammatory microenvironment, rather than general inflammation, promotes the onset of TADs by specifically recruiting neutrophils to the aortic wall. At later stages, T cell-mediated immune injury emerged as the primary driver of pathology. Gsdmd deficiency attenuated medial loss, adventitial fibrosis, and dilation of TADs. This protective effect correlated with a reduced cell death and decreased T-cell infiltration in TADs. Notably, cleaved GSDMD was detected in human TADs but was absent in healthy aortas.

CONCLUSIONS

A novel mouse TAD model was developed, specifically targeting the ascending aorta. This model generates a unique microenvironment that activates specific immune cell subsets, driving the onset and subsequent remodeling of TADs. Consistently, Gsdmd deficiency mitigates TAD development, likely by modulating cell death and T-cell responses. This model provides a valuable tool for studying immune injury mechanisms in TAD pathogenesis.

Versatility of gasdermin D beyond pyroptosis

Gasdermin D (GSDMD) has garnered significant attention primarily for the pore-forming role of its p30 N-terminal fragment (NT-p30) generated during pyroptosis, a proinflammatory form of cell death. However, emerging evidence suggests that the formation of GSDMD-NT pores is reversible, and the activation of GSDMD does not necessarily lead to pyroptosis. Instead, this process may take part either in other forms of cell death, or in various state changes of living cells, including (i) inflammation regulation, (ii) endolysosomal pathway rewiring, (iii) granule exocytosis, (iv) type II immunity, (v) food tolerance maintenance, and (vi) temporary permeability alteration. This review explores the latest insights into the involvement of GSDMD in cell death and homeostasis maintenance, aiming to underscore the pleiotropic nature of GSDMD.

The Mechanisms and Implications of Cardiolipin in the Regulation of Cell Death

Cardiolipin (CL), an exclusive phospholipid, is predominantly found within the confines of the inner mitochondrial membrane, playing an indispensable role in the sustenance of mitochondrial operations and the regulation of cellular energy metabolism. The influence of CL on the pathways of cell death has garnered significant interest in recent scholarly discourse. This review delves into the multifaceted roles of CL across various modes of cell demise, encompassing apoptosis, autophagy, pyroptosis, ferroptosis, necrosis, and necroptosis. The discussion extends to the examination of CL's implications in a clinical context, particularly concerning cardiovascular maladies, neurological degeneration, and oncological conditions. Through an integrative analysis of contemporary research findings, the aim is to elucidate the intricate dynamics of CL's involvement in cell death phenomena. While acknowledging the inherent limitations and the hurdles faced by current research endeavors, the therapeutic potential of CL as a modulator of cell death pathways is nonetheless encouraging. Forthcoming investigations must surmount these obstacles, thereby uncovering the nuanced mechanisms and impacts of CL in the realm of cell death and associated pathologies, potentially paving the way for innovative clinical intervention strategies.

TIGAR alleviates cognitive impairment in rats with chronic cerebral hypoperfusion by suppressing oxidative stress and pyroptosis

BACKGROUND

It is postulated that oxidative stress and pyroptosis, which are induced by chronic cerebral hypoperfusion (CCH), contribute to the pathogenesis of vascular cognitive impairment (VCI). The protective role of TIGAR in neurologic illnesses has been the subject of extensive examination, yet its role in models of CCH-induced cognitive impairment remains unexplored. The objective of this study was to ascertain whether TIGAR is a neuroprotective agent in rats with CCH that reduces oxidative stress and pyroptosis.

METHODS

A CCH model was established in rats through the use of bilateral common carotid artery occlusion (BCCAO). The effects of TIGAR on cognitive function and anxiety-depressive behaviors in rats with CCH were examined. To this end, the Y-maze and open field tests were employed. Nissl and hematoxylin-eosin (H&E) staining were used to assess histologic changes in the CA1 area of the hippocampus. Hippocampal glutathione (GSH) activity, malondialdehyde (MDA) content, and NADPH/NADP+ ratio were measured using the WST-8 colorimetric method to assess oxidative stress. The expression of TIGAR and pyroptosis-related proteins was assessed by western blotting.

RESULTS

A model of CCH-induced cognitive impairment was successfully established. Four weeks after BCCAO, cerebral blood flow returned to normal in the rats, and cognitive impairment and anxiety-depression-like behavior developed. In rats with CCH, MDA levels increased, GSH activity and NADPH/NADP+ ratio decreased, and pyroptosis-related protein expression increased. The pathologic findings indicated that there was an exacerbation of neuronal injury in the CA1 area of the hippocampus and that the cells were loosely arranged. In rats with CCH, overexpression of TIGAR reduced pyroptosis-associated protein expression while increasing MDA content, GSH activity, and NADPH/NADP+ ratio. It promoted neuronal cell survival, and improved cognitive function and anxiety-depression-like behavior.

CONCLUSION

Overexpression of TIGAR reduced CCH-induced oxidative stress and pyroptosis and ameliorated cognitive dysfunction and anxiety-depression-like behavior in rats. These findings suggest that TIGAR counteracts oxidative stress and prevents pyroptosis, making it a promising target for the treatment of VCI.

Gasdermin D deletion prevents liver injury and exacerbates extrahepatic damage in a murine model of alcohol-induced ACLF

Background

Gasdermin D (GSDM-D), a key executor of pyroptosis, is increased in various liver diseases and contributes to disease progression. Alcohol induces inflammasome activation and cell death, which are both linked to GSDM-D activation. However, its role in alcohol-induced acute-on-chronic liver failure (ACLF) remains unclear.

Methods

ACLF was induced in GSDM-D-deficient or wild-type (WT) mice by 28-day bile duct ligation surgery plus a single 5 g/kg alcohol binge leading to acute decompensation. Nine hours after the alcohol binge, blood, liver, kidney and cerebellum specimens were collected for analysis.

Results

Active GSDM-D was significantly increased in humans and mice ACLF livers compared with both healthy controls and cirrhotic livers. GSDM-D-deficient mice with ACLF showed decreased inflammation, neutrophil infiltration and fibrosis in the liver, together with a reduction in pyroptotic, apoptotic and necroptotic death, compared with WT ACLF mice. Notably, GSDM-D-deficient mice also showed decreased liver regeneration and hepatocyte function. This was associated with an increase in senescence and expression of stem-like/cholangiocyte markers in the liver. Interestingly, in the kidney, GSDM-D-deficient mice showed an increase in histopathological damage score, decreased function and increased expression of necroptosis-related genes. In the cerebellum, GSDM-D deficiency increased the expression of neuroinflammation markers, astrocyte activation and apoptosis-related genes.

Conclusion

Our data indicate that GSDM-D deficiency has organ-specific effects in ACLF. While it reduces inflammation, neutrophil activation, cell death and fibrosis in the liver, GSDM-D deficiency impairs the synthetic function and increases senescence in hepatocytes. GSDM-D deficiency also increases kidney injury and neuroinflammation in ACLF.

Biological and pharmacological roles of pyroptosis in pulmonary inflammation and fibrosis: recent advances and future directions

Pyroptosis, an inflammatory regulated cell death (RCD) mechanism, is characterized by cellular swelling, membrane rupture, and subsequent discharge of cellular contents, exerting robust proinflammatory effects. Recent studies have significantly advanced our understanding of pyroptosis, revealing that it can be triggered through inflammasome- and caspase-independent pathways, and interacts intricately with other RCD pathways (e.g., pyroptosis, necroptosis, ferroptosis, and cuproptosis). The pathogenesis of pulmonary fibrosis (PF), including idiopathic pulmonary fibrosis (IPF) and other interstitial lung diseases, involves a multifaceted interplay of factors such as pathogen infections, environmental pollutants, genetic variations, and immune dysfunction. This chronic and progressive interstitial lung disease is characterized by persistent inflammation, extracellular matrix (ECM) accumulation, and fibrotic alveolar wall thickening, which potentially contribute to deteriorated lung function. Despite recent advances in understanding pyroptosis, the mechanisms by which it regulates PF are not entirely elucidated, and effective strategies to improve clinical outcomes remain unclear. This review strives to deliver a comprehensive overview of the biological functions and molecular mechanisms of pyroptosis, exploring its roles in the pathogenesis of PF. Furthermore, it examines potential biomarkers and therapeutic agents for anti-fibrotic treatments.

Role of Pyroptosis in Endometrial Cancer and Its Therapeutic Regulation

Pyroptosis is an inflammatory cell death induced by inflammasomes that release several pro-inflammatory mediators such as interleukin-18 (IL-18) and interleukin-1β (IL-1β). Pyroptosis, a type of programmed cell death, has recently received increased interest both as a therapeutic and immunological mechanism. Numerous studies have provided substantial evidence supporting the involvement of inflammasomes and pyroptosis in a variety of pathological conditions including cancers, nerve damage, inflammatory diseases and metabolic conditions. Researchers have demonstrated that dysregulation of pyroptosis and inflammasomes contribute to the progression of endometriosis and gynecological malignancies. Current research also indicates that inflammasome and pyroptosis-dependent signaling pathways may further induce the progression of endometrial cancer (EC). More specifically, dysregulation of NLR family pyrin domain 3 (NLRP3) and caspase-1-dependent pyroptosis play a contributory role in the pathogenesis and development of EC. Therefore, pyroptosis-regulated protein gasdermin D (GSDMD) may be an independent prognostic biomarker for the detection of EC. This review presents the molecular mechanisms of pyroptosis-dependent signaling pathways and their contributory role and function in advancing EC. Moreover, this review offers new insights into potential future applications and innovative approaches in utilizing pyroptosis to develop effective anti-cancer therapies.

Conformational Switch of a Peptide Provides a Novel Strategy to Design Peptide Loaded Porous Organic Polymer for Pyroptosis Pathway Mediated Cancer Therapy

While peptide-based drug development is extensively explored, this strategy has limitations due to rapid excretion from the body (or shorter half-life in the body) and vulnerability to protease-mediated degradation. To overcome these limitations, a novel strategy for the development of a peptide-based anticancer agent is introduced, utilizing the conformation switch property of a chameleon sequence stretch (PEP1) derived from a mycobacterium secretory protein, MPT63. The selected peptide is then loaded into a new porous organic polymer (PG-DFC-POP) synthesized using phloroglucinol and a cresol derivative via a condensation reaction to deliver the peptide selectively to cancer cells. Utilizing ensemble and single-molecule approaches, this peptide undergoes a transition from a disordered to an alpha-helical conformation, triggered by the acidic environment within cancer cells that is demonstrated. This adopted alpha-helical conformation resulted in the formation of proteolysis-resistant oligomers, which showed efficient membrane pore-forming activity selectively for negatively charged phospholipids accumulated in cancer cell membranes. The experimental results demonstrated that the peptide-loaded PG-DFC-POP-PEP1 exhibited significant cytotoxicity in cancer cells, leading to cell death through the Pyroptosis pathway, which is established by monitoring numerous associated events starting from lysosome membrane damage to GSDMD-induced cell membrane demolition. This novel conformational switch-based drug design strategy is believed to have great potential in endogenous environment-responsive cancer therapy and the development of future drug candidates to mitigate cancers.

Gasdermin D-mediated metabolic crosstalk promotes tissue repair

The establishment of an early pro-regenerative niche is crucial for tissue regeneration1,2. Gasdermin D (GSDMD)-dependent pyroptosis accounts for the release of inflammatory cytokines upon various insults3-5. However, little is known about its role in tissue regeneration followed by homeostatic maintenance. Here we show that macrophage GSDMD deficiency delays tissue recovery but has little effect on the local inflammatory milieu or the lytic pyroptosis process. Profiling of the metabolite secretome of hyperactivated macrophages revealed a non-canonical metabolite-secreting function of GSDMD. We further identified 11,12-epoxyeicosatrienoic acid (11,12-EET) as a bioactive, pro-healing oxylipin that is secreted from hyperactive macrophages in a GSDMD-dependent manner. Accumulation of 11,12-EET by direct supplementation or deletion of Ephx2, which encodes a 11,12-EET-hydrolytic enzyme, accelerated muscle regeneration. We further demonstrated that EPHX2 accumulated within aged muscle, and that consecutive 11,12-EET treatment rejuvenated aged muscle. Mechanistically, 11,12-EET amplifies fibroblast growth factor signalling by modulating liquid-liquid phase separation of fibroblast growth factors, thereby boosting the activation and proliferation of muscle stem cells. These data depict a GSDMD-guided metabolite crosstalk between macrophages and muscle stem cells that governs the repair process, which offers insights with therapeutic implications for the regeneration of injured or aged tissues.

Pulmonary damage induction upon Acrylic amide exposure via activating miRNA-223-3p and miRNA-325-3p inflammasome/pyroptosis and fibrosis signaling pathway: New mechanistic approaches of A green-synthesized extract

Exposure to acrylic amide (AD) has garnered worldwide attention due to its potential adverse health effects, prompting calls from the World Health Organization for intensified research into associated risks. Despite this, the relationship between oral acrylic amide (acrylamide) (AD) exposure and pulmonary dysfunction remains poorly understood. Our study aimed to investigate the correlation between internal oral exposure to AD and the decline in lung function, while exploring potential mediating factors such as tissue inflammation, oxidative stress, pyroptosis, and apoptosis. Additionally, we aimed to evaluate the potential protective effect of zinc oxide nanoparticles green-synthesized moringa extract (ZNO-MONPs) (10 mg/kg b.wt) against ACR toxicity and conducted comprehensive miRNA expression profiling to uncover novel targets and mechanisms of AD toxicity (miRNA 223-3 P and miRNA 325-3 P). Furthermore, we employed computational techniques to predict the interactions between acrylic amide and/or MO-extract components and tissue proteins. Using a rat model, we exposed animals to oral acrylamide (20 mg/kg b.wt for 2 months). Our findings revealed that AD significantly downregulated the expression of miRNA 223-3 P and miRNA 325-3 P, targeting NLRP-3 & GSDMD, respectively, indicating the induction of pyroptosis in pulmonary tissue via an inflammasome activating pathway. Moreover, AD exposure resulted in lipid peroxidative damage and reduced levels of GPX, CAT, GSH, and GSSG. Notably, AD exposure upregulated apoptotic, pyroptotic, and inflammatory genes, accompanied by histopathological damage in lung tissue. Immunohistochemical and immunofluorescence techniques detected elevated levels of indicative harmful proteins including vimentin and 4HNE. Conversely, concurrent administration of ZNO-MONPs with AD significantly elevated the expression of miRNA 223-3 P and miRNA 325-3 P, protecting against oxidative stress, apoptosis, pyroptosis, inflammation, and fibrosis in rat lungs. In conclusion, our study highlights the efficacy of ZNO-MONPs NPs in protecting pulmonary tissue against the detrimental impacts of foodborne toxin AD.

Gasdermin-B (GSDMB) takes center stage in antibacterial defense, inflammatory diseases, and cancer

One of the hottest topics in biomedical research is to decipher the functional implications of the Gasdermin (GSDM) protein family in human pathologies. These proteins are the key effectors of a lytic and pro-inflammatory cell death type termed pyroptosis (also known as "Gasdermin-mediated programmed cell death"). However, ever-growing evidence showed that GSDMs can play multiple and complex roles in a context-dependent manner. In this sense, Gasdermin-B (GSDMB; the only GSDM gene absent in mice and rats) has been implicated in antibacterial defense, numerous inflammatory pathologies (e.g., asthma, ulcerative colitis), and cancer, but both cell death-dependent and -independent functions have been reported in these diseases, fueling the debate on whether GSDMB has genuine pyroptotic capacity. Recently, a series of seminal papers cast light on the GSDMB multitasking capacity by showing that different GSDMB transcriptional isoforms have distinct biological activities. Nonetheless, there are still obscure areas to be clarified on the precise functional involvement of GSDMB translated variants in physiological and pathological conditions. In this viewpoint, we critically discuss the most recent and exciting data on this topic and propose a series of relevant challenges that need to be overcome before GSDMB-driven biomedical applications (as a biomarker of disease risk/progression/outcome or as specific therapeutic target) become a reality in clinical settings.

Cell Membrane Perforation: Patterns, Mechanisms and Functions

Cell membrane is crucial for the cellular activities, and any disruption to it may affect the cells. It is demonstrated that cell membrane perforation is associated with some biological processes like programmed cell death (PCD) and infection of pathogens. Specific developments make it a promising technique to perforate the cell membrane controllably and precisely. The pores on the cell membrane provide direct pathways for the entry and exit of substances, and can also cause cell death, which means reasonable utilization of cell membrane perforation is able to assist intracellular delivery, eliminate diseased or cancerous cells, and bring about other benefits. This review classifies the patterns of cell membrane perforation based on the mechanisms into 1) physical patterns, 2) biological patterns, and 3) chemical patterns, introduces the characterization methods and then summarizes the functions according to the characteristics of reversible and irreversible pores, with the aim of providing a comprehensive summary of the knowledge related to cell membrane perforation and enlightening broad applications in biomedical science.

Induction of IFIT1/IFIT3 and inhibition of Bcl-2 orchestrate the treatment of myeloma and leukemia via pyroptosis

Induction of pyroptosis is proposed as a promising strategy for the treatment of hematological malignancies, but little is known. In the present study, we find clioquinol (CLQ), an anti-parasitic drug, induces striking myeloma and leukemia cell pyroptosis on a drug screen. RNA sequencing reveals that the interferon-inducible genes IFIT1 and IFIT3 are markedly upregulated and are essential for CLQ-induced GSDME activation and cell pyroptosis. Specifically, IFIT1 and IFIT3 form a complex with BAX and N-GSDME therefore directing N-GSDME translocalization to mitochondria and increasing mitochondrial membrane permeabilization and triggering pyroptosis. Furthermore, venetoclax, an activator of BAX and an inhibitor of Bcl-2, displays strikingly synergistic effects with CLQ against leukemia and myeloma via pyroptosis. This study thus reveals a novel mechanism for mitochondrial GSDME in pyroptosis and it also illustrates that induction of IFIT1/T3 and inhibition of Bcl-2 orchestrate the treatment of leukemia and myeloma via pyroptosis.

Gasdermin D regulates soluble fms-like tyrosine kinase 1 release in macrophages

Preeclampsia (PE) is a serious complication, and soluble fms-like tyrosine kinase (sFLT1) released from the placenta is one of the causes of PE pathology. Trophoblasts are the primary source of sFLT1; however, monocytes/macrophages exist enough in the placenta can also secrete sFLT1. Sterile inflammatory responses, especially NLRP3 inflammasome and its downstream gasdermin D (GSDMD)-regulated pyroptosis, may be involved in the development of PE pathology. In this study, we investigated whether human monocyte/macrophage cell line THP-1 cells secrete sFLT1 depending on the NLRP3 inflammasome and GSDMD. To differentiate THP-1 monocytes into macrophages, treatment with phorbol 12-myristate 13-acetate (PMA) induced sFLT1 with interleukin (IL)- 1β, but did not induce cell lytic death. IL-1β secretion induced by PMA inhibited by deletion of NLRP3 and inhibitors of NLRP3 and caspase-1, but deletion of NLRP3 and these inhibitors did not affect sFLT1 secretion in THP-1 cells. Both gene deletion and inhibition of GSDMD dramatically decreased IL-1β and sFLT1 secretion from THP-1 cells. Treatment with CA074-ME (a cathepsin B inhibitor) also reduced the secretion of both sFLT1 and IL-1β in THP-1 cells. In conclusion, THP-1 macrophages release sFLT1 in a GSDMD-dependent manner, but not in the NLRP3 inflammasome-dependent manner, and this sFLT1 release may be associated with the non-lytic role of GSDMD. In addition, sFLT1 levels induced by PMA are associated with lysosomal cathepsin B in THP-1 macrophages. We suggest that sFLT1 synthesis regulated by GSDMD are involved in the pathology of PE.

Using CRISPR-Cas9/phosphoproteomics to identify substrates of calcium/calmodulin-dependent kinase 2δ

Ca2+/Calmodulin-dependent protein kinase 2 (CAMK2) family proteins are involved in the regulation of cellular processes in a variety of tissues including brain, heart, liver, and kidney. One member, CAMK2δ (CAMK2D), has been proposed to be involved in vasopressin signaling in the renal collecting duct, which controls water excretion through regulation of the water channel aquaporin-2 (AQP2). To identify CAMK2D target proteins in renal collecting duct cells (mpkCCD), we deleted Camk2d and carried out LC-MS/MS-based quantitative phosphoproteomics. Specifically, we used CRISPR/Cas9 with two different guide RNAs targeting the CAMK2D catalytic domain to create multiple CAMK2D KO cell lines. AQP2 protein abundance was lower in the CAMK2D KO cells than in CAMK2D-intact controls. AQP2 phosphorylation at Ser256 and Ser269 (normalized for total AQP2) was decreased. However, trafficking of AQP2 to and from the apical plasma membrane was sustained. Large-scale quantitative phosphoproteomic analysis (TMT-labeling) in the presence of the vasopressin analog dDAVP (0.1 nM, 30 min) allowed quantification of 11,570 phosphosites of which 169 were significantly decreased, while 206 were increased in abundance in CAMK2D KO clones. These data are available for browsing or download at https://esbl.nhlbi.nih.gov/Databases/CAMK2D-proteome/. Motif analysis of the decreased phosphorylation sites revealed a target preference of -(R/K)-X-X-p(S/T)-X-(D/E), matching the motif identified in previous in vitro phosphorylation studies using recombinant CAMK2D. Thirty five of the significantly downregulated phosphorylation sites in CAMK2D KO cells had exactly this motif and are judged to be likely direct CAMK2D targets. This adds to the list of known CAMK2D target proteins found in prior reductionist studies.

Toxoplasma gondii Induces Pyroptosis in Human Placental Trophoblast and Amniotic Cells by Inducing ROS Production and Activation of Cathepsin B and NLRP1/NLRP3/NLRC4/AIM2 Inflammasome

Toxoplasma gondii infection in pregnant women may cause fetal anomalies; however, the underlying mechanisms remain unclear. The current study investigated whether T. gondii induces pyroptosis in human placental cells and the underlying mechanisms. Human placental trophoblast (BeWo and HTR-8/SVneo) and amniotic (WISH) cells were infected with T. gondii, and then reactive oxygen species (ROS) production, cathepsin B (CatB) release, inflammasome activation, and pyroptosis induction were evaluated. The molecular mechanisms of these effects were investigated by treating the cells with ROS scavengers, a CatB inhibitor, or inflammasome-specific siRNA. T. gondii infection induced ROS generation and CatB release into the cytosol in placental cells but decreased mitochondrial membrane potential. T. gondii-infected human placental cells and villi exhibited NLRP1, NLRP3, NLRC4, and AIM2 inflammasome activation and subsequent pyroptosis induction, as evidenced by increased expression of ASC, cleaved caspase-1, and mature IL-1β and gasdermin D cleavage. In addition to inflammasome activation and pyroptosis induction, adverse pregnancy outcome was shown in a T. gondii-infected pregnant mouse model. Administration of ROS scavengers, CatB inhibitor, or inflammasome-specific siRNA into T. gondii-infected cells reversed these effects. Collectively, these findings show that T. gondii induces NLRP1/NLRP3/NLRC4/AIM2 inflammasome-dependent caspase-1-mediated pyroptosis via induction of ROS production and CatB activation in placental cells. This mechanism may play an important role in inducing cell injury in congenital toxoplasmosis.

Structural and functional insights into GSDMB isoforms complex roles in pathogenesis

SHADSGasdermins (GSDMs) have garnered significant scientific interest due to their protective and detrimental roles in innate immunity, host defense, inflammation, and cancer alongside with other pathologies. While GSDMs are mostly recognized as key effectors of a lytic type of pro-inflammatory cell death known as pyroptosis, they do also take part in other cell death processes (NETosis, secondary necrosis, or apoptosis) and exhibit cell-death independent functions depending on the cellular context. Among GSDMs, Gasdermin B (GSDMB) pyroptotic capacity has been a subject of conflicting findings in scientific literature even when its processing, and subsequent activation, by Granzyme A (GZMA) was decoded. Nevertheless, recent groundbreaking publications have shed light on the crucial role of alternative splicing in determining the pyroptotic capacity of GSDMB isoforms, which depends on the presence of exon 6-derived elements. This comprehensive review pays attention to the relevant structural differences among recently crystalized GSDMB isoforms. As a novelty, the structural aspects governing GSDMB isoform susceptibility to GZMA-mediated activation have been investigated. By elucidating the complex roles of GSDMB isoforms, this review aims to deepen the understanding of this multifunctional player and its potential implications in disease pathogenesis and therapeutic interventions. [Figure: see text].