Granzyme B enters the mitochondria in a Sam50-, Tim22- and mtHsp70-dependent manner to induce apoptosis

Ablation of Sam50 is associated with fragmentation and alterations in metabolism in murine and human myotubes

The sorting and assembly machinery (SAM) Complex is responsible for assembling β-barrel proteins in the mitochondrial membrane. Comprising three subunits, Sam35, Sam37, and Sam50, the SAM complex connects the inner and outer mitochondrial membranes by interacting with the mitochondrial contact site and cristae organizing system complex. Sam50, in particular, stabilizes the mitochondrial intermembrane space bridging (MIB) complex, which is crucial for protein transport, respiratory chain complex assembly, and regulation of cristae integrity. While the role of Sam50 in mitochondrial structure and metabolism in skeletal muscle remains unclear, this study aims to investigate its impact. Serial block-face-scanning electron microscopy and computer-assisted 3D renderings were employed to compare mitochondrial structure and networking in Sam50-deficient myotubes from mice and humans with wild-type (WT) myotubes. Furthermore, autophagosome 3D structure was assessed in human myotubes. Mitochondrial metabolic phenotypes were assessed using Gas Chromatography-Mass Spectrometry-based metabolomics to explore differential changes in WT and Sam50-deficient myotubes. The results revealed increased mitochondrial fragmentation and autophagosome formation in Sam50-deficient myotubes compared to controls. Metabolomic analysis indicated elevated metabolism of propanoate and several amino acids, including ß-Alanine, phenylalanine, and tyrosine, along with increased amino acid and fatty acid metabolism in Sam50-deficient myotubes. Furthermore, impairment of oxidative capacity was observed upon Sam50 ablation in both murine and human myotubes, as measured with the XF24 Seahorse Analyzer. Collectively, these findings support the critical role of Sam50 in establishing and maintaining mitochondrial integrity, cristae structure, and mitochondrial metabolism. By elucidating the impact of Sam50-deficiency, this study enhances our understanding of mitochondrial function in skeletal muscle.

Granzymes in health and diseases: the good, the bad and the ugly

Granzymes are a family of serine proteases, composed of five human members: GA, B, H, M and K. They were first discovered in the 1980s within cytotoxic granules released during NK cell- and T cell-mediated killing. Through their various proteolytic activities, granzymes can trigger different pathways within cells, all of which ultimately lead to the same result, cell death. Over the years, the initial consideration of granzymes as mere cytotoxic mediators has changed due to surprising findings demonstrating their expression in cells other than immune effectors as well as new intracellular and extracellular activities. Additional roles have been identified in the extracellular milieu, following granzyme escape from the immunological synapse or their release by specific cell types. Outside the cell, granzyme activities mediate extracellular matrix alteration via the degradation of matrix proteins or surface receptors. In certain contexts, these processes are essential for tissue homeostasis; in others, excessive matrix degradation and extensive cell death contribute to the onset of chronic diseases, inflammation, and autoimmunity. Here, we provide an overview of both the physiological and pathological roles of granzymes, highlighting their utility while also recognizing how their unregulated presence can trigger the development and/or worsening of diseases.

Light deficiency in Apoe-/-mice increases atheroma plaque size and vulnerability by modulating local immunity

Previous research suggests a potential involvement of the cytokine LIGHT (TNFSF14) in atherosclerosis. In this study, the genetic inactivation of Light in Apolipoprotein E deficient mice (male and female C57BL) augmented plaque size and vulnerability while decreasing Treg cells. Human and mouse transcriptomic results demonstrated deranged immune pathways in human atheromas with low LIGHT expression levels and in Light-deficient murine atheromas. In agreement with this, in vitro LIGHT-treatment of human lymphocytes, induced an elevation of Treg cell prevalence while proteomic analysis showed a downregulation of apoptotic and leukocyte cytotoxic pathways. Consistently, Light-deficient mouse lesions displayed increased plaque apoptosis and detrimental adventitial T-lymphocyte aggregates. Altogether suggested that LIGHT could promote a Treg prevalence in the local immunity to prevent the generation of vulnerable plaques via decreased cytotoxic microenvironment and apoptosis. Light gene delivery in Apoe-/-Light-/- mice, through bone marrow transplantation approaches, consistently diminished lesion size and restored local plaque immunity. Altogether demonstrate that Light-deficiency promotes atheroma plaque progression, at least in part through local loss of immune homeostasis and increased apoptosis. This study suggest that therapies based on the local delivery of LIGHT within plaques might therefore prevent immune cell derangement and advanced atherosclerosis.

Ablation of Sam50 is associated with fragmentation and alterations in metabolism in murine and human myotubes

The Sorting and Assembly Machinery (SAM) Complex is responsible for assembling β-barrel proteins in the mitochondrial membrane. Comprising three subunits, Sam35, Sam37, and Sam50, the SAM complex connects the inner and outer mitochondrial membranes by interacting with the mitochondrial contact site and cristae organizing system (MICOS) complex. Sam50, in particular, stabilizes the mitochondrial intermembrane space bridging (MIB) complex, which is crucial for protein transport, respiratory chain complex assembly, and regulation of cristae integrity. While the role of Sam50 in mitochondrial structure and metabolism in skeletal muscle remains unclear, this study aims to investigate its impact. Serial block-face-scanning electron microscopy (SBF-SEM) and computer-assisted 3D renderings were employed to compare mitochondrial structure and networking in Sam50-deficient myotubes from mice and humans with wild-type (WT) myotubes. Furthermore, autophagosome 3D structure was assessed in human myotubes. Mitochondrial metabolic phenotypes were assessed using Gas Chromatography-Mass Spectrometry-based metabolomics to explore differential changes in WT and Sam50-deficient myotubes. The results revealed increased mitochondrial fragmentation and autophagosome formation in Sam50-deficient myotubes compared to controls. Metabolomic analysis indicated elevated metabolism of propanoate and several amino acids, including ß-Alanine, phenylalanine, and tyrosine, along with increased amino acid and fatty acid metabolism in Sam50-deficient myotubes. Furthermore, impairment of oxidative capacity was observed upon Sam50 ablation in both murine and human myotubes, as measured with the XF24 Seahorse Analyzer. Collectively, these findings support the critical role of Sam50 in establishing and maintaining mitochondrial integrity, cristae structure, and mitochondrial metabolism. By elucidating the impact of Sam50-deficiency, this study enhances our understanding of mitochondrial function in skeletal muscle.

Combination of downregulating FEN1 and PD-1 blockade enhances antitumor activity of CD8+ T cells against HNSCC cells in vitro

BACKGROUND

Programmed cell death ligand 1 (PD-L1) and human leukocyte antigen/major histocompatibility complex (HLA/MHC) are two main kinds of immunophenotypes affecting the susceptibility to anti-PD therapy. Our previous study found that down-regulation of flap endonuclease-1 (FEN1) could not only inhibit PD-L1 expression, but also upregulate HLA expression in head and neck squamous cell carcinoma (HNSCC). We aimed to clarify whether downregulating FEN1 cloud enhance the response to PD-1 blockade, and possible mechanisms in HNSCC in vitro.

METHODS

Differential expression of FEN1 in HNSCC tumor and normal tissues were explored in the TIMER and TISIDB datasets. A HNSCC cells/CD8+ T cells co-culture model was established. HNSCC cell cycle and apoptosis were recorded by flow cytometry. Immune activity markers of granzyme A, granzyme B, and PRF1 expressed in the CD8+ T cells, and IFN-γ, IL-2, and TNF-α secreted in the supernatants were detected by western blot, ELISA, respectively.

RESULTS

FEN1 was highly expressed in HNSCC and associated with low immune infiltration. Downregulating FEN1 could induce HLA class I expression, and inhibit PD-L1 expression in HNSCC cells. Functionally, FEN1 knockdown enhanced the response to αPD-1 mAb by mediating G2/M phase arrest, apoptosis of HNSCC cells. Mechanistically, targeting FEN1 synergized with αPD-1 mAb could reinforce the antitumor response of CD8+ T cells against HNSCC cells, as indicated by increasing granzyme A, granzyme B, and PRF1 expressions, and promoting IFN-γ, IL-2, and TNF-α secretions.

CONCLUSION

These findings might offer a potential combined strategy for patients resistant to anti-PD therapy via combining FEN1 knockdown and PD-1 blockade.

Fluid shear stress enhances natural killer cell's cytotoxicity toward circulating tumor cells through NKG2D-mediated mechanosensing

Tumor cells metastasize to distant organs mainly via hematogenous dissemination, in which circulating tumor cells (CTCs) are relatively vulnerable, and eliminating these cells has great potential to prevent metastasis. In vasculature, natural killer (NK) cells are the major effector lymphocytes for efficient killing of CTCs under fluid shear stress (FSS), which is an important mechanical cue in tumor metastasis. However, the influence of FSS on the cytotoxicity of NK cells against CTCs remains elusive. We report that the death rate of CTCs under both NK cells and FSS is much higher than the combined death induced by either NK cells or FSS, suggesting that FSS may enhance NK cell's cytotoxicity. This death increment is elicited by shear-induced NK activation and granzyme B entry into target cells rather than the death ligand TRAIL or secreted cytokines TNF-α and IFN-γ. When NK cells form conjugates with CTCs or adhere to MICA-coated substrates, NK cell activating receptor NKG2D can directly sense FSS to induce NK activation and degranulation. These findings reveal the promotive effect of FSS on NK cell's cytotoxicity toward CTCs, thus providing new insight into immune surveillance of CTCs within circulation.

Genetic Variation of SAMM50 Is Not an Independent Risk Factor for Alcoholic Hepatocellular Carcinoma in Caucasian Patients

Hepatocellular carcinoma (HCC) is a severe complication of advanced alcoholic liver disease, which is modulated by genetic predisposition. Identifying new genetic loci might improve screening. Genetic variation of SAMM50 was linked to HCC. We aimed to validate this finding in a large cohort of patients with advanced alcoholic liver disease (ALD). A large, well-characterised cohort of patients with alcoholic cirrhosis without (n = 674) and with (n = 386) HCC, as well as controls with HCC due to viral hepatitis (n = 134), controls with heavy alcohol abuse without liver disease (n = 266) and healthy subjects (n = 237), were genotyped for SAMM50 rs3827385 and rs3761472 and for PNPLA3 rs738409. Genotype frequencies were compared between patients with alcohol-associated cirrhosis with and without HCC by uni- and multivariate analysis. Minor variants in both SAMM50 rs3827385 and rs3761472 were significantly more frequent in patients with alcoholic HCC versus alcoholic cirrhosis and versus the control cohorts. An even stronger association was noted for PNPLA3 rs738409. The univariate analysis resulted in an odds ratio (OR) of 1.8 for carriers of at least one minor variant of SAMM50 rs3827385 and rs3761472 (each p < 0.001), but this association was lost in multivariate analysis with age (OR 1.1/year), male sex (OR 3.2), diabetes (OR 1.9) and carriage of PNPLA3 148M (OR 2.1) remaining in the final model. Although minor variants of both SAMM50 loci are strongly associated with alcoholic HCC, this association is not independent of carriage of the well-known risk variant PNPLA3 148M.

Apoptosis evasion via long non-coding RNAs in colorectal cancer

Long non-coding RNA (LncRNA) is a novel and diverse class of regulatory transcripts that are frequently dysregulated in numerous tumor types. LncRNAs are involved in a complicated molecular network, regulating gene expression, and modulating diverse cellular activities in different cancers including colorectal cancer (CRC). Evidence indicates that lncRNAs can be used as a potential biomarker for the prognosis and diagnosis of CRC as they are aberrantly expressed in CRC cells. The high expression or silencing of lncRNAs is associated with cell proliferation, invasion, metastasis, chemoresistance and apoptosis in CRC. LncRNAs exert both pro-apoptotic and anti-apoptotic functions in CRC. The expression of some oncogene lncRNAs is upregulated which leads to the inhibition of apoptotic pathways, similarly, the tumor suppressor lncRNAs are downregulated in CRC. In this review, we describe the function and mechanisms of lncRNAs to regulate the expression of genes that are involved directly or indirectly in controlling cellular apoptosis in CRC. Furthermore, we also discussed the different apoptotic pathways in normal cells and the mechanisms by which CRC evade apoptosis.

Greek Fire, Poison Arrows, and Scorpion Bombs: How Tumor Cells Defend Against the Siege Weapons of Cytotoxic T Lymphocytes

CD8⁺ cytotoxic T lymphocytes (CTLs) are the main cellular effectors of the adaptive immune response against cancer cells, which in turn have evolved sophisticated cellular defense mechanisms to withstand CTL attack. Herein we provide a critical review of the pertinent literature on early and late attack/defense events taking place at the CTL/target cell lytic synapse. We examine the earliest steps of CTL-mediated cytotoxicity (“the poison arrows”) elicited within seconds of CTL/target cell encounter, which face commensurately rapid synaptic repair mechanisms on the tumor cell side, providing the first formidable barrier to CTL attack. We examine how breach of this first defensive barrier unleashes the inextinguishable “Greek fire” in the form of granzymes whose broad cytotoxic potential is linked to activation of cell death executioners, injury of vital organelles, and destruction of intracellular homeostasis. Herein tumor cells deploy slower but no less sophisticated defensive mechanisms in the form of enhanced autophagy, increased reparative capacity, and dysregulation of cell death pathways. We discuss how the newly discovered supra-molecular attack particles (SMAPs, the “scorpion bombs”), seek to overcome the robust defensive mechanisms that confer tumor cell resistance. Finally, we discuss the implications of the aforementioned attack/defense mechanisms on the induction of regulated cell death (RCD), and how different contemporary RCD modalities (including apoptosis, pyroptosis, and ferroptosis) may have profound implications for immunotherapy. Thus, we propose that understanding and targeting multiple steps of the attack/defense process will be instrumental to enhance the efficacy of CTL anti-tumor activity and meet the outstanding challenges in clinical immunotherapy.

Natural killer cells kill extracellular Pseudomonas aeruginosa using contact-dependent release of granzymes B and H

Pseudomonas aeruginosa is an opportunistic pathogen that often infects individuals with the genetic disease cystic fibrosis, and contributes to airway blockage and loss of lung function. Natural killer (NK) cells are cytotoxic, granular lymphocytes that are part of the innate immune system. NK cell secretory granules contain the cytolytic proteins granulysin, perforin and granzymes. In addition to their cytotoxic effects on cancer and virally infected cells, NK cells have been shown to play a role in an innate defense against microbes, including bacteria. However, it is not known if NK cells kill extracellular P. aeruginosa or how bacterial killing might occur at the molecular level. Here we show that NK cells directly kill extracellular P. aeruginosa using NK effector molecules. Live cell imaging of a co-culture of YT cells, a human NK cell line, and GFP-expressing P. aeruginosa in the presence of the viability dye propidium iodide demonstrated that YT cell killing of P. aeruginosa is contact-dependent. CRISPR knockout of granulysin or perforin in YT cells had no significant effect on YT cell killing of P. aeruginosa. Pre-treatment of YT and NK cells with the serine protease inhibitor 3,4-dichloroisocoumarin (DCI) to inhibit all granzymes, resulted in an inhibition of killing. Although singular CRISPR knockout of granzyme B or H had no effect, knockout of both in YT cells completely abrogated killing of P. aeruginosa in comparison to wild type YT cell controls. Nitrocefin assays suggest that the bacterial membrane is damaged. Inhibition of killing by antioxidants suggest that ROS are required for the bactericidal mode-of-action. Taken together, these results identify that NK cells kill P. aeruginosa through a membrane damaging, contact-dependent process that requires granzyme induced ROS production, and moreover, that granzyme B and H are redundant in this killing process.

Natural Killer (NK) cells comprise at least 10% of the resident lymphocytes in the lung and are increasingly recognized as an important part of the immune response to bacterial pathogens. Despite invivo studies demonstrating the importance of NK cells in the host response to the respiratory pathogen Pseudomonas aeruginosa, the mechanism of antimicrobial activity has yet to be found. Using human NK cell lines and NK cells isolated from human peripheral blood, we show that NK cells exhibit direct, contact-dependent cytotoxicity against P. aeruginosa, leading to bacterial cell death. NK cells use granzyme B and H to damage bacterial membranes and permeabilize the cells. We provide evidence that this leads to increased reactive oxygen species (ROS) in the bacteria that kills them. Furthermore, granzyme function appears to be redundant because loss of function by one granzyme is rescued by the activity of the other. These findings identify a role for granzymes in the antibacterial functions of NK cells, providing new insight into the host response to P. aeruginosa infections.

Is Mitochondrial Oxidative Stress a Viable Therapeutic Target in Preeclampsia?

Despite considerable research efforts over the past few decades, the pathology of preeclampsia (PE) remains poorly understood with no new FDA-approved treatments. There is a substantial amount of work being conducted by investigators around the world to identify targets to develop therapies for PE. Oxidative stress has been identified as one of the crucial players in pathogenesis of PE and has garnered a great deal of attention by several research groups including ours. While antioxidants have shown therapeutic benefit in preclinical models of PE, the clinical trials evaluating antioxidants (vitamin E and vitamin C) were found to be disappointing. Although the idea behind contribution of mitochondrial oxidative stress in PE is not new, recent years have seen an enormous interest in exploring mitochondrial oxidative stress as an important pathological mediator in PE. We and others using animals, cell models, and preeclamptic patient samples have shown the evidence for placental, renal, and endothelial cell mitochondrial oxidative stress, and its significance in PE. These studies offer promising results; however, the important and relevant question is can we translate these results into clinical efficacy in treating PE. Hence, the purpose of this review is to review the existing literature and offer our insights on the potential of mitochondrial antioxidants in treating PE.

Bcl-2 Family Members and the Mitochondrial Import Machineries: The Roads to Death

The localization of Bcl-2 family members at the mitochondrial outer membrane (MOM) is a crucial step in the implementation of apoptosis. We review evidence showing the role of the components of the mitochondrial import machineries (translocase of the outer membrane (TOM) and the sorting and assembly machinery (SAM)) in the mitochondrial localization of Bcl-2 family members and how these machineries regulate the function of pro- and anti-apoptotic proteins in resting cells and in cells committed into apoptosis.

Reactive Oxygen Species: Do They Play a Role in Adaptive Immunity?

The immune system protects the host from a plethora of microorganisms and toxins through its unique ability to distinguish self from non-self. To perform this delicate but essential task, the immune system relies on two lines of defense. The innate immune system, which is by nature fast acting, represents the first line of defense. It involves anatomical barriers, physiological factors as well as a subset of haematopoietically-derived cells generically call leukocytes. Activation of the innate immune response leads to a state of inflammation that serves to both warn about and combat the ongoing infection and delivers the antigenic information of the invading pathogens to initiate the slower but highly potent and specific second line of defense, the adaptive immune system. The adaptive immune response calls on T lymphocytes as well as the B lymphocytes essential for the elimination of pathogens and the establishment of the immunological memory. Reactive oxygen species (ROS) have been implicated in many aspects of the immune responses to pathogens, mostly in innate immune functions, such as the respiratory burst and inflammasome activation. Here in this mini review, we focus on the role of ROS in adaptive immunity. We examine how ROS contribute to T-cell biology and discuss whether this activity can be extrapolated to B cells.

Oxidative and Non-Oxidative Antimicrobial Activities of the Granzymes

Cell-mediated cytotoxicity is an essential immune defense mechanism to fight against viral, bacterial or parasitic infections. Upon recognition of an infected target cell, killer lymphocytes form an immunological synapse to release the content of their cytotoxic granules. Cytotoxic granules of humans contain two membrane-disrupting proteins, perforin and granulysin, as well as a homologous family of five death-inducing serine proteases, the granzymes. The granzymes, after delivery into infected host cells by the membrane disrupting proteins, may contribute to the clearance of microbial pathogens through different mechanisms. The granzymes can induce host cell apoptosis, which deprives intracellular pathogens of their protective niche, therefore limiting their replication. However, many obligate intracellular pathogens have evolved mechanisms to inhibit programed cells death. To overcome these limitations, the granzymes can exert non-cytolytic antimicrobial activities by directly degrading microbial substrates or hijacked host proteins crucial for the replication or survival of the pathogens. The granzymes may also attack factors that mediate microbial virulence, therefore directly affecting their pathogenicity. Many mechanisms applied by the granzymes to eliminate infected cells and microbial pathogens rely on the induction of reactive oxygen species. These reactive oxygen species may be directly cytotoxic or enhance death programs triggered by the granzymes. Here, in the light of the latest advances, we review the antimicrobial activities of the granzymes in regards to their cytolytic and non-cytolytic activities to inhibit pathogen replication and invasion. We also discuss how reactive oxygen species contribute to the various antimicrobial mechanisms exerted by the granzymes.

Target-Initiated Great Change in Electrochemical Steric Hindrance for an Assay of Granzyme B Activity

To improve long-term graft patient outcomes and develop more effective antirejection therapies, noninvasive monitoring of acute cellular rejection (ACR) after organ transplantation is urgently needed. As a biomarker of ACR, Granzyme B (GrB) is expected to be applied in the noninvasive monitoring of ACR. Herein, we have developed a method for detecting the GrB activity based on the target-initiated great change in electrochemical steric hindrance by designing a nanoprobe. The nanoprobe is prepared by conjugating a specific peptide, which is responsive to GrB cleavage activity, to gold nanoparticles (AuNPs). Meanwhile, a piece of DNA sequence with G-quadruplex (G4) is attached at the distal end of the peptide. Upon exposure to GrB, the peptide substrate is cleaved to eliminate the steric hindrance between inter-nanoprobes as well as nanoprobe and DNA tetrahedron (TDN), allowing the released DNA strand to hybridize with TDN, giving sensitive signal output. The method can also be used to detect GrB activity in complex biological settings, so it has a great potential for monitoring GrB activity in the blood or urine of graft patients.

The Diversity of the Mitochondrial Outer Membrane Protein Import Channels: Emerging Targets for Modulation

The functioning of mitochondria and their biogenesis are largely based on the proper function of the mitochondrial outer membrane channels, which selectively recognise and import proteins but also transport a wide range of other molecules, including metabolites, inorganic ions and nucleic acids. To date, nine channels have been identified in the mitochondrial outer membrane of which at least half represent the mitochondrial protein import apparatus. When compared to the mitochondrial inner membrane, the presented channels are mostly constitutively open and consequently may participate in transport of different molecules and contribute to relevant changes in the outer membrane permeability based on the channel conductance. In this review, we focus on the channel structure, properties and transported molecules as well as aspects important to their modulation. This information could be used for future studies of the cellular processes mediated by these channels, mitochondrial functioning and therapies for mitochondria-linked diseases.

Protein Import Assay into Mitochondria Isolated from Human Cells

Mitochondria are essential organelles containing approximately 1,500 proteins. Only approximately 1% of these proteins are synthesized inside mitochondria, whereas the remaining 99% are synthesized as precursors on cytosolic ribosomes and imported into the organelle. Various tools and techniques to analyze the import process have been developed. Among them, in vitro reconstituted import systems are of importance to study these processes in detail. These experiments monitor the import reaction of mitochondrial precursors that were previously radiolabeled in a cell-free environment. However, the methods described have been mostly performed in mitochondria isolated from S. cerevisiae. Here, we describe the adaptation of this powerful assay to import proteins into crude mitochondria isolated from human tissue culture cells. Graphic abstract: Overview of the assay to monitor protein import into mitochondria isolated from human cells.

Long Non-coding RNA LINC02474 Affects Metastasis and Apoptosis of Colorectal Cancer by Inhibiting the Expression of GZMB

Background

Colorectal cancer (CRC) is one of the most frequently diagnosed malignancies. Metastasis is the main event that impedes the therapeutic effect on CRC, and its underlying mechanisms remain largely unclear. LINC02474 is a novel long noncoding RNA (lncRNA) associated with metastasis of CRC, while little is known about how LINC02474 regulates these malignant characteristics.

Methods

Expressions of LINC02474 and granzyme B (GZMB) were assessed by quantitative real-time polymerase chain reaction (qRT-PCR) or Western blotting analysis. Cell metastasis was detected by transwell assay and metastatic nude mouse model, and apoptosis was determined by Western blotting analysis and flow cytometry. Besides, the interaction between LINC02474 and GZMB was detected by dual-luciferase reporter assays.

Results

The expression of LINC02474 was significantly up-regulated in CRC tissues. Moreover, depletion of LINC02474 damaged the metastatic abilities of CRC cells in vivo and in vitro while boosting apoptosis. Besides, up-regulation of LINC02474 could promote migration and invasion, while apoptosis was inhibited in CRC cells. Besides, down-regulation of LINC02474 promoted the expression of GZMB, and interference of GZMB could increase the metastatic abilities of CRC cells while reducing apoptosis. Furthermore, LINC02474 was related to the transcriptional repression of GZMB in CRC cells determined by the dual-luciferase reporter assay.

Conclusions

The findings revealed that a novel lncRNA, LINC02474, as an oncogene, could promote metastasis, but limit apoptosis partly by impeding GZMB expression in CRC. Besides, LINC02474 had the potential to be used as a biomarker in the prognosis of CRC.

Perforin and granzymes in neurological infections: From humans to cattle

Perforin and granzymes are essential components of the cytotoxic granules present in cytotoxic T lymphocytes and natural killer cells. These proteins play a crucial role in a variety of conditions, including viral infections, tumor immune surveillance, and tissue rejection. Besides their beneficial effect in most of these situations, perforin and granzymes have also been associated with tissue damage and immune diseases. Moreover, it has been reported that perforin and granzymes released during viral infections could contribute to the pathogenesis of diseases. In this review, we summarize the information available on human perforin and granzymes and their relationship with neurological infections and immune disorders. Furthermore, we compare this information with that available for bovine and present data on perforin and granzymes expression in cattle infected with bovine alphaherpesvirus types1 and -5. To our knowledge, this is the first review analyzing the impact of perforin and granzymes on neurological infections caused by bovine herpesviruses.

A Newly Defined Pyroptosis-Related Gene Signature for the Prognosis of Bladder Cancer

BACKGROUND

Bladder cancer (BC), as the most common urinary system tumor type and the main cause of tumor-related death, has an unsatisfactory prognosis. In recent years, related literature has proposed that cell pyroptosis is an inflammatory form of programmed cell death. However, in BC, the relationship between the expression of pyroptosis-related genes and the prognosis has not been elucidated.

METHODS

We got the RNA sequencing data from TCGA and GEO datasets. Fifty-two pyroptosis-related genes were extracted for further explore. Then, we compared the gene expression levels between the normal bladder and BC tissues. After that, we develop and validate a pyroptosis-related gene prognostic model and made following functional enrichment analysis and single-sample gene set enrichment analysis of the differentially expressed genes between the high- and low-risk groups.

RESULTS

Twenty-nine differentially expressed genes (DEGs) were found between normal and tumor tissues. Based on the median score calculated by the risk score formula from 8 pyroptosis-related genes, 414 patients were equally divided into low- and high-risk subgroups. The survival probability of BC patients in the high-risk group was significantly lower than that in the low-risk group (P < 0.001). Through multivariate analysis, our risk score is an independent factor predicting OS in BC patients. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis show that high-risk populations are rich in immune-related genes and have a decreased immune status. All the above results have been externally verified from GEO cohort.

CONCLUSION

Pyroptosis-related genes are closely related to tumor immunity and are a potential prognostic tool for predicting BCs.

SAM50, a side door to the mitochondria: The case of cytotoxic proteases

SAM50, a 7-8 nm diameter β-barrel channel of the mitochondrial outer membrane, is the central channel of the sorting and assembly machinery (SAM) complex involved in the biogenesis of β-barrel proteins. Interestingly, SAM50 is not known to have channel translocase activity; however, we have recently found that this channel is necessary and sufficient for mitochondrial entry of cytotoxic proteases. Cytotoxic lymphocytes eliminate cells that pose potential hazards, such as virus- and bacteria-infected cells as well as cancer cells. They induce cell death following the delivery of granzyme cytotoxic proteases into the cytosol of the target cell. Although granzyme A and granzyme B (GA and GB), the best characterized of the five human granzymes, trigger very distinct apoptotic cascades, they share the ability to directly target the mitochondria. GA and GB do not have a mitochondrial targeting signal, yet they enter the target cell mitochondria to disrupt respiratory chain complex I and induce mitochondrial reactive oxygen species (ROS)-dependent cell death. We found that granzyme mitochondrial entry requires SAM50 and the translocase of the inner membrane 22 (TIM22). Preventing granzymes' mitochondrial entry compromises their cytotoxicity, indicating that this event is unexpectedly an important step for cell death. Although mitochondria are best known for their roles in cell metabolism and energy conversion, these double-membrane organelles are also involved in Ca²⁺ homeostasis, metabolite transport, cell cycle regulation, cell signaling, differentiation, stress response, redox homeostasis, aging, and cell death. This multiplicity of functions is matched with the complexity and plasticity of the mitochondrial proteome as well as the organelle's morphological and structural versatility. Indeed, mitochondria are extremely dynamic and undergo fusion and fission events in response to diverse cellular cues. In humans, there are 1500 different mitochondrial proteins, the vast majority of which are encoded in the nuclear genome and translated by cytosolic ribosomes, after which they must be imported and properly addressed to the right mitochondrial compartment. To this end, mitochondria are equipped with a very sophisticated and highly specific protein import machinery. The latter is centered on translocase complexes embedded in the outer and inner mitochondrial membranes working along five different import pathways. We will briefly describe these import pathways to put into perspective our finding regarding the ability of granzymes to enter the mitochondria.

Tumor necrosis factor alpha (TNF-α) blockade improves natural killer cell (NK) activation, hypertension, and mitochondrial oxidative stress in a preclinical rat model of preeclampsia

The RUPP rat model of Preeclampsia exhibits hypertension (MAP), cytolytic natural killer (cNK) cells, tumor necrosis factor alpha (TNF-α) and mitochondrial Reactive Oxygen Species (mt ROS).  Objective: Does TNF-α blockade with ETAN (Etanercept) decrease cNK cell and mt ROS in RUPP rats.

METHODS

On gestational day 14, RUPP surgery was performed, ETAN (0.4 mg/kg) was administered on day 18, MAP, blood and tissues collected on 19.

RESULTS

MAP, cytolytic NK cells and mt ROS were elevated in RUPP vs. NP and normalized with ETAN.

CONCLUSION

TNF-α blockade lowered blood pressure and improve inflammation and organ function in response to placental ischemia.

Granzymes and Mitochondria

Cytotoxic T lymphocytes and natural killer cells eliminate infected cells from the organism by triggering programmed cell death (apoptosis). The contents of the lytic granules of killer cells, including pore-forming proteins perforins and proteolytic enzymes granzymes, are released with the following penetration of the released proteins into the target cells. Granzyme B initiates mitochondria-dependent apoptosis via (i) proapoptotic Bid protein, (ii) Mcl-1 and Bim proteins, or (iii) p53 protein. As a result, cytochrome c is released from the mitochondria into the cytoplasm, causing formation of apoptosomes that initiate the proteolytic cascade of caspase activation. Granzymes M, H, and F cause cell death accompanied by the cytochrome c release from the mitochondria. Granzyme A induces generation of reactive oxygen species (ROS), which promotes translocation of the endoplasmic reticulum-associated SET complex to the nucleus where it is cleaved by granzyme A, leading to the activation of nucleases that catalyze single-strand DNA breaks. Granzymes A and B penetrate into the mitochondria and cleave subunits of the respiratory chain complex I. One of the complex I subunits is also a target for caspase-3. Granzyme-dependent damage to complex I leads to the ROS generation and cell death.

Granzyme B Attenuates Bacterial Virulence by Targeting Secreted Factors

Pathogenic bacteria secrete virulence factors that interact with the human host to establish infections. The human immune system evolved multiple mechanisms to fight bacterial invaders, including immune proteases that were demonstrated to contribute crucially to antibacterial defense. Here we show that granzyme B degrades multiple secreted virulence mediators from Listeria monocytogenes, Salmonella typhimurium, and Mycobacteria tuberculosis. Pathogenic bacteria, when infected in the presence of granzyme B or granzyme-secreting killer cells, fail to grow in human macrophages and epithelial cells owing to their crippled virulence. A granzyme B-uncleavable mutant form of the major Listeria virulence factor, listeriolysin O, rescued the virulence defect in response to granzyme treatment. Hence, we link the degradation of a single factor with the observed decrease in virulent bacteria growth. Overall, we reveal here an innate immune barrier function of granzyme B by disrupting bacterial virulence to facilitate bacteria clearance by bystander immune and non-immune cells.

Granzyme B and miR-378a Interaction in Acetaminophen Toxicity in Children

BACKGROUND AND AIM

Hepatic phase I drug-metabolizing enzymes CYP2E1, CYP1A2 and CYP3A4 catalyze the biotransformation of Acetaminophen (APAP) and are important in the mediation of toxicity. The potential role of other hepatic and non-hepatic Phase I enzymes in APAP toxicity has not been established.

METHODS

PCR array containing 84 genes involved in phase I drug metabolism was examined in subgroups of hospitalized children for APAP overdose, categorized as no toxicity (ALT ≤ 45 IU/L, n=5) and moderate toxicity (ALT ≥ 500 IU/L, n=5).

RESULTS

Significant downregulation was observed for ALDH6A1, CYP4F12 and GZMB in the no toxicity subgroup and ALDH1A1, CYP27A1 and GZMB in the moderate toxicity subgroup. qRTPCR confirmed significant downregulation for ALDH1A1, CYP4F12, and GZMB. In-silico analysis identified GZMB 3'UTR to be a target of miR-378a-5p. Overexpression of miR-378a-5p reduced the luciferase activity of GZMB 3'UTR reporter plasmid reportedly by 50%. NK-92 cells transfected with the miR-378a-5p mimic extended the effect of APAP on GZMB protein expression compared to mimic controls. In addition, miR-378a-5p was significantly upregulated in blood samples of children with APAP overdose undergoing NAC treatment.

CONCLUSION

Overall, our study suggests the presence of a novel signaling pathway, whereby miR- 378a-5p inhibits GZMB expression in children with APAP overdose.

Myoblasts rely on TAp63 to control basal mitochondria respiration

p53, with its family members p63 and p73, have been shown to promote myoblast differentiation by regulation of the function of the retinoblastoma protein and by direct activation of p21^Cip/Waf1 and p57^Kip2, promoting cell cycle exit. In previous studies, we have demonstrated that the TAp63γ isoform is the only member of the p53 family that accumulates during in vitro myoblasts differentiation, and that its silencing led to delay in myotube fusion. To better dissect the role of TAp63γ in myoblast physiology, we have generated both sh-p63 and Tet-On inducible TAp63γ clones. Gene array analysis of sh-p63 C2C7 clones showed a significant modulation of genes involved in proliferation and cellular metabolism. Indeed, we found that sh-p63 C2C7 myoblasts present a higher proliferation rate and that, conversely, TAp63γ ectopic expression decreases myoblasts proliferation, indicating that TAp63γ specifically contributes to myoblasts proliferation, independently of p53 and p73. In addition, sh-p63 cells have a defect in mitochondria respiration highlighted by a reduction in spare respiratory capacity and a decrease in complex I, IV protein levels. These results demonstrated that, beside contributing to cell cycle exit, TAp63γ participates to myoblasts metabolism control.

Effects of Pseudomonas aeruginosa on Microglial-Derived Extracellular Vesicle Biogenesis and Composition

The packaging of molecular constituents inside extracellular vesicles (EVs) allows them to participate in intercellular communication and the transfer of biological molecules, however the role of EVs during bacterial infection is poorly understood. The goal of this study was to examine the effects of Pseudomonas aeruginosa (P. aeruginosa) infection on the biogenesis and composition of EVs derived from the mouse microglia cell line, BV-2. BV-2 cells were cultured in exosome-free media and infected with 0, 1.3 × 10⁴, or 2.6 × 10⁴ colony forming units per milliliter P. aeruginosa for 72 h. The results indicated that compared with the control group, BV-2 cell viability significantly decreased after P. aeruginosa infection and BV-2-derived EVs concentration decreased significantly in the P. aeruginosa-infected group. P. aeruginosa infection significantly decreased chemokine ligand 4 messenger RNA in BV-2-derived infected EVs, compared with the control group (p ≤ 0.05). This study also revealed that heat shock protein 70 (p ≤ 0.05) and heat shock protein 90β (p ≤ 0.001) levels of expression within EVs increased after P. aeruginosa infection. EV treatment with EVs derived from P. aeruginosa infection reduced cell viability of BV-2 cells. P. aeruginosa infection alters the expression of specific proteins and mRNA in EVs. Our study suggests that P. aeruginosa infection modulates EV biogenesis and composition, which may influence bacterial pathogenesis and infection.

DNA methylation and hydroxymethylation patterns in acute myeloid leukemia patients with mutations in DNMT3A and IDH1/2 and their combinations

BACKGROUND

Aberrant epigenetic patterns are a hallmark of acute myeloid leukemia (AML). Mutations in profound epigenetic regulators DNMT3A and IDH1/2 often occur concurrently in AML.

OBJECTIVES

The aim was to analyze DNA methylation, hydroxymethylation and mRNA expression profiles in AML with mutations in DNMT3A and IDH1/2 (individually and in combinations).

METHODS

Infinium MethylationEPIC BeadChip (Illumina) covering 850,000 CpGs was utilized. The validation of hydroxy-/methylation data was done by pyrosequencing. HumanHT-12 v4 Expression BeadChip (Illumina) was used for expression examination.

RESULTS

Hierarchical clustering analysis of DNA hydroxy-/methylation data revealed clusters corresponding to DNMT3A and IDH1/2 mutations and CD34+ healthy controls. Samples with concurrent presence of DNMT3A and IDH1/2 mutations displayed mixed DNA hydroxy-/methylation profile with preferential clustering to healthy controls. Numbers and levels of DNA hydroxymethylation were low. Uniformly hypermethylated loci in AML patients with IDH1/2 mutations were enriched for immune response and apoptosis related genes, among which hypermethylation of granzyme B (GZMB) was found to be associated with inferior overall survival of AML patients (P= 0.035).

CONCLUSIONS

Distinct molecular background results in specific DNA hydroxy-/methylation profiles in AML. Site-specific DNA hydroxymethylation changes are much less frequent in AML pathogenesis compared to DNA methylation. Methylation levels of enhancer located upstream GZMB gene might contribute to AML prognostication models.

Fundamental Mechanisms of Regulated Cell Death and Implications for Heart Disease

Twelve regulated cell death programs have been described. We review in detail the basic biology of nine including death receptor-mediated apoptosis, death receptor-mediated necrosis (necroptosis), mitochondrial-mediated apoptosis, mitochondrial-mediated necrosis, autophagy-dependent cell death, ferroptosis, pyroptosis, parthanatos, and immunogenic cell death. This is followed by a dissection of the roles of these cell death programs in the major cardiac syndromes: myocardial infarction and heart failure. The most important conclusion relevant to heart disease is that regulated forms of cardiomyocyte death play important roles in both myocardial infarction with reperfusion (ischemia/reperfusion) and heart failure. While a role for apoptosis in ischemia/reperfusion cannot be excluded, regulated forms of necrosis, through both death receptor and mitochondrial pathways, are critical. Ferroptosis and parthanatos are also likely important in ischemia/reperfusion, although it is unclear if these entities are functioning as independent death programs or as amplification mechanisms for necrotic cell death. Pyroptosis may also contribute to ischemia/reperfusion injury, but potentially through effects in non-cardiomyocytes. Cardiomyocyte loss through apoptosis and necrosis is also an important component in the pathogenesis of heart failure and is mediated by both death receptor and mitochondrial signaling. Roles for immunogenic cell death in cardiac disease remain to be defined but merit study in this era of immune checkpoint cancer therapy. Biology-based approaches to inhibit cell death in the various cardiac syndromes are also discussed.

Subcellular NAMPT-mediated NAD+ salvage pathways and their roles in bioenergetics and neuronal protection after ischemic injury

NAD⁺ is a cofactor required for glycolysis, tricarboxylic acid cycle, and complex I enzymatic reaction. In mammalian cells, NAD⁺ is predominantly synthesized through the salvage pathway, where nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme. Previously, we demonstrated that NAMPT exerts a neuroprotective effect in ischemia through the suppression of mitochondrial dysfunction. Mammalian cells maintain distinct NAD⁺ pools in the cytosol, mitochondria, and nuclei. However, it is unknown whether mitochondria have an intact machinery for NAD⁺ salvage, and if so, whether it plays a dominant role in bioenergetics, mitochondrial function, and neuronal protection after ischemia. Here, using mouse primary cortical neuron and cortical tissue preparations, and multiple technologies including cytosolic and mitochondrial subfractionation, viral over-expression of transgenes, molecular biology, and confocal microscopy, we provided compelling evidence that neuronal mitochondria possess an intact machinery of NAMPT-mediated NAD⁺ salvage pathway, and that NAMPT and nicotinamide mononucleotide adenylyltransferase 3 (NMNAT3) are localized in the mitochondrial matrix. By knocking down NMNAT1-3 and NAMPT with siRNA, we found that NMNAT3 has a larger effect on basal and ATP production-related mitochondrial respiration than NMNAT1-2 in primary cultured neurons, while NMNAT1-2 have a larger effect on glycolytic flux than NMNAT3. Using an oxygen glucose deprivation model, we found that mitochondrial, cytoplasmic, and non-subcellular compartmental over-expressions of NAMPT have a comparable effect on neuronal protection and suppression of apoptosis-inducing factor translocation. The current study provides novel insights into the roles of subcellular compartmental NAD⁺ salvage pathways in NAD⁺ homeostasis, bioenergetics, and neuronal protection in ischemic conditions.

Deciphering targets of Th17 cells fate: From metabolism to nuclear receptors

Evidence indicates that reprogramming of metabolism is critically important for the differentiation of CD4 + T lymphocytes, and the manipulation of metabolic pathways in these cells may shape their fate and function. Distinct subgroups from T lymphocytes, such as Th17, adopt specific metabolic programmes to support their needs. Some important metabolic reactions, such as glycolysis, oxidative phosphorylation, are considered important for the differentiation of these lymphocytes. Since their discovery nearly a decade ago, Th17 lymphocytes have received significant attention because of their role in the pathology of several immune-mediated inflammatory diseases such as multiple sclerosis. In this review, it will be discussed as the involvement of T cell metabolism and as metabolic reprogramming in activated T cells dictates fate decisions to Th17. The involvement of nuclear receptors such as RORyt e PPARs in the induction of Th17 cells was also discussed. Understanding the metabolic pathways involved in the differentiation of the distinct subgroups of T lymphocytes helps in the design of promising therapeutic proposals.

Mitochondrial Entry of Cytotoxic Proteases: A New Insight into the Granzyme B Cell Death Pathway

The mitochondria represent an integration and amplification hub for various death pathways including that mediated by granzyme B (GB), a granule enzyme expressed by cytotoxic lymphocytes. GB activates the proapoptotic B cell CLL/lymphoma 2 (Bcl-2) family member BH3-interacting domain death agonist (BID) to switch on the intrinsic mitochondrial death pathway, leading to Bcl-2-associated X protein (Bax)/Bcl-2 homologous antagonist/killer- (Bak-) dependent mitochondrial outer membrane permeabilization (MOMP), the dissipation of mitochondrial transmembrane potential (ΔΨm), and the production of reactive oxygen species (ROS). GB can also induce mitochondrial damage in the absence of BID, Bax, and Bak, critical for MOMP, indicating that GB targets the mitochondria in other ways. Interestingly, granzyme A (GA), GB, and caspase 3 can all directly target the mitochondrial respiratory chain complex I for ROS-dependent cell death. Studies of ROS biogenesis have revealed that GB must enter the mitochondria for ROS production, making the mitochondrial entry of cytotoxic proteases (MECP) an unexpected critical step in the granzyme death pathway. MECP requires an intact ΔΨm and is mediated though Sam50 and Tim22 channels in a mtHSP70-dependent manner. Preventing MECP severely compromises GB cytotoxicity. In this review, we provide a brief overview of the canonical mitochondrial death pathway in order to put into perspective this new insight into the GB action on the mitochondria to trigger ROS-dependent cell death.

Global Identification of HIF-1α Target Genes in Benzene Poisoning Mouse Bone Marrow Cells

Benzene is a hematopoietic toxicant, and hematopoietic cells in bone marrow (BM) are one of the main targets for its action, especially hematopoietic stem cells (HSCs). Hypoxia-inducible factor-1α (HIF-1α) is associated with the metabolism and physiological functions of HSCs. We previously found that the mechanism of regulation of HIF-1α is involved in benzene-induced hematopoietic toxicity. In this study, chromatin immunoprecipitation sequencing (ChIP-Seq) technologies were used to analyze the genome-wide binding spectrum of HIF-1α in mouse BM cells, and specific HIF-1α target genes and pathways associated with benzene toxicity were screened and validated. By application of the ChIP-Seq technique, we identified target genes HIF-1α directly binds to and regulates. Forty-two differentially down-regulated genes containing the HIF-1α specific binding site hypoxia response element (HRE) were found, of which 25 genes were with biological function. Moreover, the enrichment analysis of signal pathways indicated that these genes were significantly enriched in the Jak-STAT signaling pathway, Natural killer cell mediated cytotoxicity, the Fc epsilon RI signaling pathway, Pyrimidine metabolism, the T cell receptor signaling pathway, and Transcriptional misregulation in cancer. After verification, 11 genes involved in HSC self-renewal, cell cycle, differentiation, and apoptosis pathways were found to be significantly reduced, and may participate in benzene-induced hematotoxicity. Our study provides a new academic clue for the mechanism of benzene hematotoxicity.

The role of the mitochondria and the endoplasmic reticulum contact sites in the development of the immune responses

Mitochondria and endoplasmic reticulum (ER) contact sites (MERCs) are dynamic modules enriched in subset of lipids and specialized proteins that determine their structure and functions. The MERCs regulate lipid transfer, autophagosome formation, mitochondrial fission, Ca2+ homeostasis and apoptosis. Since these functions are essential for cell biology, it is therefore not surprising that MERCs also play a critical role in organ physiology among which the immune system stands by its critical host defense function. This defense system must discriminate and tolerate host cells and beneficial commensal microorganisms while eliminating pathogenic ones in order to preserve normal homeostasis. To meet this goal, the immune system has two lines of defense. First, the fast acting but unspecific innate immune system relies on anatomical physical barriers and subsets of hematopoietically derived cells expressing germline-encoded receptors called pattern recognition receptors (PRR) recognizing conserved motifs on the pathogens. Second, the slower but very specific adaptive immune response is added to complement innate immunity. Adaptive immunity relies on another set of specialized cells, the lymphocytes, harboring receptors requiring somatic recombination to be expressed. Both innate and adaptive immune cells must be activated to phagocytose and process pathogens, migrate, proliferate, release soluble factors and destroy infected cells. Some of these functions are strongly dependent on lipid transfer, autophagosome formation, mitochondrial fission, and Ca2+ flux; this indicates that MERCs could regulate immunity.