Regulation of pro-apoptotic leucocyte granule serine proteinases by intracellular serpins

Serpina3n/serpina3 alleviates cyclophosphamide-induced interstitial cystitis by activating the Wnt/β-catenin signal

BACKGROUND/OBJECTIVE

Serpina3n/Serpina3 has been identified to be implicated in inflammatory diseases, but its role in interstitial cystitis/bladder pain syndrome (IC/BPS) remains unknown. Here, we aimed to reveal serpina3n/serpina3 role in IC/BPS in vivo and in vitro.

METHODS

The IC/BPS model in mice was induced by intraperitoneal injection of 150 mg/kg of cyclophosphamide (CYP). HE and toluidine blue staining were used for histology assessment. Serpina3n/serpina3 expression in the bladder tissues from IC/BPS patients and mouse models were determined by qPCR, immunohistochemistry and western blotting. XAV-939 treatment was applied to inhibit β-catenin activation. Serpina3 role in modulating the growth and apoptosis of HBlEpCs, a human primary bladder epithelial cell line, was assessed by CCK-8 and flow cytometry assays.

RESULTS

Serpina3n/serpina3 expression was decreased in both human and mice bladder tissues with IC/BPS. Upregulation of serpina3n significantly alleviated CYP-induced bladder injury, with decreased mast cells and pro-inflammatory factor levels, including IL-1β, IL-6, and TNF-α, while increased IL-10 level. In addition, serpina3 overexpression inhibited the apoptosis of HBlEpCs, and increased cell growth. In mechanism, we found that serpina3 overexpression promoted the activation of wnt/β-catenin signaling. And, the inhibition of wnt/β-catenin signaling with XAV-939 abolished serpina3n/serpina3 role in protecting bladder tissues from CYP-induced cystitis, as well as inhibiting HBlEpC apoptosis.

CONCLUSION

Serpina3n/serpina3 expression was decreased in IC/BPS. Overexpression of serpina3n could alleviate CYP-induced IC/BPS by activating the Wnt/β-catenin signal. This study may provide a new therapeutic strategy for IC/BPS.

Proteolytic Biosensors with Functional Nanomaterials: Current Approaches and Future Challenges

Proteolytic enzymes are one of the important biomarkers that enable the early diagnosis of several diseases, such as cancers. A specific proteolytic enzyme selectively degrades a certain sequence of a polypeptide. Therefore, a particular proteolytic enzyme can be selectively quantified by changing detectable signals causing degradation of the peptide chain. In addition, by combining polypeptides with various functional nanomaterials, proteolytic enzymes can be measured more sensitively and rapidly. In this paper, proteolytic enzymes that can be measured using a polypeptide degradation method are reviewed and recently studied functional nanomaterials-based proteolytic biosensors are discussed. We anticipate that the proteolytic nanobiosensors addressed in this review will provide valuable information on physiological changes from a cellular level for individual and early diagnosis.

The Role of Proteases and Serpin Protease Inhibitors in β-Cell Biology and Diabetes

Regulation of the equilibrium between proteases and their inhibitors is fundamental to health maintenance. Consequently, developing a means of targeting protease activity to promote tissue regeneration and inhibit inflammation may offer a new strategy in therapy development for diabetes and other diseases. Specifically, recent efforts have focused on serine protease inhibitors, known as serpins, as potential therapeutic targets. The serpin protein family comprises a broad range of protease inhibitors, which are categorized into 16 clades that are all extracellular, with the exception of Clade B, which controls mostly intracellular proteases, including both serine- and papain-like cysteine proteases. This review discusses the most salient, and sometimes opposing, views that either inhibition or augmentation of protease activity can bring about positive outcomes in pancreatic islet biology and inflammation. These potential discrepancies can be reconciled at the molecular level as specific proteases and serpins regulate distinct signaling pathways, thereby playing equally distinct roles in health and disease development.

Molecular network, pathway, and functional analysis of time-dependent gene changes related to cathepsin G exposure in neonatal rat cardiomyocytes

The molecular pathways activated in response to acute cathepsin G (CG) exposure, as well as the mechanisms involved in activation of signaling pathways that culminate in myocyte detachment and apoptosis remain unclear. This study aimed to determine the changes in gene expression patterns associated with time dependent CG exposure to neonatal rat cardiomyocytes (NRCMs). Microarray analysis revealed a total of 451, 572 and 1127 differentially expressed genes after CG exposure at 1, 4 and 8 h respectively. A total of 54 overlapped genes at each time point were mapped by Ingenuity Pathway Analysis (IPA). The top up-regulated genes included Hamp, SMAD6, NR4A1, FOSL2, ID3 and SLAMF7, and down-regulated genes included CYR61, GDF6, Olr640, Vom2r36, DUSP6 and MMP20. Our data suggest that there are multiple deregulated pathways associated with cardiomyocyte death after CG exposure, including JAK/Stat signaling, IL-9 signaling and Nur77 signaling. In addition, we also generated the molecular network of expressed gene and found most of the molecules were connected to ERK1/2, caspase, BCR (complex) and Cyclins. Our study reveals the ability to assess time-dependent changes in gene expression patterns in NRCMs associated with CG exposure. The global gene expression profiles may provide insight into the cellular mechanism that regulates CG dependent myocyte apoptosis. In future, the pathways important in CG response, as well as the genes found to be differentially expressed might represent the therapeutic targets for myocyte survival in heart failure.

Involvement of cystatin C in immunity and apoptosis

As an abundantly expressed cysteine protease inhibitor widely distributed in the organisms, cystatin C is involved in various physiological processes. Due to its relatively small molecular weight and easy detection, cystatin C is commonly used as a measure for glomerular filtration rate. In pathological conditions, however, growing evidences suggest that cystatin C is associated with various immune responses against either exogenous or endogenous antigens, which ultimately result in inflammatory autoimmune diseases or tumor development if not properly controlled. Thus the fluctuation of cystatin C levels might have more clinical implications than a reflection of kidney functions. Here, we summarize the latest development of studies on the pathophysiological functions of cystatin C, with focus on its immune regulatory roles at both cellular and molecular levels including antigen presentation, secretion of cytokines, synthesis of nitric oxide, as well as apoptosis. Finally, we discuss the clinical implications and therapeutic potentials of what this predominantly expressed protease inhibitor can bring to us.

A pro-survival role for the intracellular granzyme B inhibitor Serpinb9 in natural killer cells during poxvirus infection

Intracellular serpins are proposed to inactivate proteases released from lysosome-related organelles into the host cell interior, preventing cell death. Serpinb9 opposes the immune cytotoxic protease, granzyme B, and in a number of settings protects cells against granzyme B-mediated cell death. Using a knockout mouse line engineered to express green fluorescent protein under the serpbinb9 promoter, we demonstrate that serpinb9 is vital for host survival during Ectromelia virus infection by maintaining both mature natural killer NK) cells, and activated CD8⁺ T cells. Serpinb9 expression parallels granzyme B expression within both populations during infection. Maturing serpinb9-null NK cells exhibit higher levels of granzyme B-mediated apoptosis during infection; hence there are fewer mature NK cells, and these cells also have lower cytotoxic potential. Thus the serpinb9-granzyme B axis is important for homeostasis of both major cytotoxic effector cell populations.

Myeloid conditional deletion and transgenic models reveal a threshold for the neutrophil survival factor Serpinb1

Serpinb1 is an inhibitor of neutrophil granule serine proteases cathepsin G, proteinase-3 and elastase. One of its core physiological functions is to protect neutrophils from granule protease-mediated cell death. Mice lacking Serpinb1a (Sb1a-/-), its mouse ortholog, have reduced bone marrow neutrophil numbers due to cell death mediated by cathepsin G and the mice show increased susceptibility to lung infections. Here, we show that conditional deletion of Serpinb1a using the Lyz2-cre and Cebpa-cre knock-in mice effectively leads to recombination-mediated deletion in neutrophils but protein-null neutrophils were only obtained using the latter recombinase-expressing strain. Absence of Serpinb1a protein in neutrophils caused neutropenia and increased granule permeabilization-induced cell death. We then generated transgenic mice expressing human Serpinb1 in neutrophils under the human MRP8 (S100A8) promoter. Serpinb1a expression levels in founder lines correlated positively with increased neutrophil survival when crossed with Sb1a-/- mice, which had their defective neutrophil phenotype rescued in the higher expressing transgenic line. Using new conditional and transgenic mouse models, our study demonstrates the presence of a relatively low Serpinb1a protein threshold in neutrophils that is required for sustained survival. These models will also be helpful in delineating recently described functions of Serpinb1 in metabolism and cancer.

Neutrophil-Derived Proteases in the Microenvironment of Pancreatic Cancer -Active Players in Tumor Progression

A hallmark of pancreatic ductal adenocarcinoma (PDAC) is the fibro-inflammatory microenvironment, consisting of activated pancreatic stellate cells, extracellular matrix proteins, and a variety of inflammatory cells, such as T cells, macrophages, or neutrophils. Tumor-infiltrating immune cells, which are found in nearly all cancers, including PDAC, often fail to eliminate the tumor, but conversely can promote its progression by altering the tumor microenvironment. Pancreatic cancer cells are able to attract polymorphonuclear neutrophils (PMN) via tumor secreted chemokines and in human PDAC, PMN infiltrates can be observed in the vicinity of tumor cells and in the desmoplastic tumor stroma, which correlate with undifferentiated tumor growth and poor prognosis. The behavior of tumor-infiltrating neutrophils in the tumor micromilieu is not yet understood at a mechanistic level. It has been shown that PMN have the potential to kill tumor cells, either directly or by antibody-dependent cell-mediated cytotoxicity, but on the other side various adverse effects of PMN, such as promotion of aggressive tumor growth with epithelial-to-mesenchymal transition and increased metastatic potential, have been described. Recent therapeutic approaches for PDAC focus not only the tumor cell itself, but also elements of the tumor microenvironment. Therefore, the role of PMN and their derived products (e.g. cytokines, proteases) as a new vein for a therapeutic target should be critically evaluated in this context. This review summarizes the current understanding of the interplay between proteases of tumor-infiltrating neutrophils and pancreatic tumor cells and elements of the desmoplastic stroma.

Skin mucus proteome map of European sea bass (Dicentrarchus labrax)

Skin mucus is the first barrier of fish defence. Proteins from skin mucus of European sea bass (Dicentrarchus labrax) were identified by 2DE followed by LC-MS/MS. From all the identified proteins in the proteome map, we focus on the proteins associated with several immune pathways in fish. Furthermore, the real-time PCR transcript levels in skin are shown. Proteins found include apolipoprotein A1, calmodulin, complement C3, fucose-binding lectin, lysozyme and several caspases. To our knowledge, this is the first skin mucus proteome study and further transcriptional profiling of the identified proteins done on this bony fish species. This not only contributes knowledge on the routes involved in mucosal innate immunity, but also establishes a non-invasive technique based on locating immune markers with a potential use for prevention and/or diagnosis of fish diseases.

Regulation of Neutrophil Serine Proteases by Intracellular Serpins

Neutrophil granules contain serine proteases that are central components of the antimicrobial weapons of the innate immune system. Neutrophil proteases also contribute to the amplification and resolution of inflammatory responses through defined proteolytic cleavage of mediators, cell surface receptors, and extracellular matrix proteins. In the blood and at mucosal surfaces, neutrophil serine proteases are regulated by serpins found in plasma and by non-serpin secreted inhibitors. Distinct mechanisms leading to neutrophil cell death have been described for the granule serine proteases, neutrophil elastase, cathepsin G, and proteinase-3. Granule leakage in neutrophils triggers death pathways mediated by cathepsin G and proteinase-3, and both proteases are tightly regulated by their inhibitor SERPINB1 in a cell intrinsic manner. Although stored in the same types of granules, neutrophil elastase does not significantly contribute to cell death following intracellular release from granules into the cytoplasm. However, heterozygous mutations in ELANE, the gene encoding elastase, are the cause of severe congenital neutropenia, a life-threatening condition characterized by the death of neutrophils at an early precursor stage in the bone marrow. This chapter focuses on recent work exploring the biology of clade B intracellular serpins that inhibit neutrophil serine proteases and their functions in neutrophil homeostasis and serine protease control at sites of inflammation.

Proteinase 3-dependent caspase-3 cleavage modulates neutrophil death and inflammation

Caspase-3-mediated spontaneous death in neutrophils is a prototype of programmed cell death and is critical for modulating physiopathological inflammatory responses; however, the underlying regulatory pathways remain ill defined. Here we determined that in aging neutrophils, the cleavage and activation of caspase-3 is independent of the canonical caspase-8- or caspase-9-mediated pathway. Instead, caspase-3 activation was mediated by serine protease proteinase 3 (PR3), which is present in the cytosol of aging neutrophils. Specifically, PR3 cleaved procaspase-3 at a site upstream of the canonical caspase-9 cleavage site. In mature neutrophils, PR3 was sequestered in granules and released during aging via lysosomal membrane permeabilization (LMP), leading to procaspase-3 cleavage and apoptosis. Pharmacological inhibition or knockdown of PR3 delayed neutrophil death in vitro and consistently delayed neutrophil death and augmented neutrophil accumulation at sites of inflammation in a murine model of peritonitis. Adoptive transfer of both WT and PR3-deficient neutrophils revealed that the delayed death of neutrophils lacking PR3 is due to an altered intrinsic apoptosis/survival pathway, rather than the inflammatory microenvironment. The presence of the suicide protease inhibitor SERPINB1 counterbalanced the protease activity of PR3 in aging neutrophils, and deletion of Serpinb1 accelerated neutrophil death. Taken together, our results reveal that PR3-mediated caspase-3 activation controls neutrophil spontaneous death.

Adaptive evolution and divergence of SERPINB3: a young duplicate in great Apes

A series of duplication events led to an expansion of clade B Serine Protease Inhibitors (SERPIN), currently displaying a large repertoire of functions in vertebrates. Accordingly, the recent duplicates SERPINB3 and B4 located in human 18q21.3 SERPIN cluster control the activity of different cysteine and serine proteases, respectively. Here, we aim to assess SERPINB3 and B4 coevolution with their target proteases in order to understand the evolutionary forces shaping the accelerated divergence of these duplicates. Phylogenetic analysis of primate sequences placed the duplication event in a Hominoidae ancestor (∼30 Mya) and the emergence of SERPINB3 in Homininae (∼9 Mya). We detected evidence of strong positive selection throughout SERPINB4/B3 primate tree and target proteases, cathepsin L2 (CTSL2) and G (CTSG) and chymase (CMA1). Specifically, in the Homininae clade a perfect match was observed between the adaptive evolution of SERPINB3 and cathepsin S (CTSS) and most of sites under positive selection were located at the inhibitor/protease interface. Altogether our results seem to favour a coevolution hypothesis for SERPINB3, CTSS and CTSL2 and for SERPINB4 and CTSG and CMA1. A scenario of an accelerated evolution driven by host-pathogen interactions is also possible since SERPINB3/B4 are potent inhibitors of exogenous proteases, released by infectious agents. Finally, similar patterns of expression and the sharing of many regulatory motifs suggest neofunctionalization as the best fitted model of the functional divergence of SERPINB3 and B4 duplicates.

Serpins, immunity and autoimmunity: old molecules, new functions

Serine protease inhibitors (serpins) are evolutionary old, structurally conserved molecules which encompass nearly all branches of life. More than 1,000 serpins were characterized to date which are subdivided into 16 subgroups (A-P) according to their common ancestry; among them, 37 are found in humans. Serpins were termed after their capability to inhibit serine proteases, but mounting evidence suggests that they may achieve a greater deal of functions, ranging from embryological growth to synaptic plasticity, development of both myeloid and lymphoid immune cells, and modulation of apoptosis. Serpins are mainly extracellular molecules, although some of them (namely, ov-serpins or clade B serpins) mostly act inside the cells, being either ubiquitously or tissue-specifically expressed. Among newly characterized serpin functions, regulation of cellular proliferation through apoptosis modulation and proteasome disturbance seems to play a major role. Accordingly, several serpins were found to be hyperexpressed in tumor cells. Indeed, apoptosis dysregulation is likely to be a cornerstone in both tumorigenesis and autoimmunity, since uncontrolled cellular viability results in tumor proliferation, while inefficient disposal of apoptotic debris may favor the rescue of autoreactive immune cells. Such a process was widely documented in systemic lupus erythematosus (SLE). Interestingly, alterations in the expression of some serpins, e.g., the ov-serpin SERPINB3, are being unraveled in patients affected with SLE and other autoimmune disorders, suggesting that a failure in serpin function might affect immune homeostasis and self-tolerance, thereby contributing to autoimmunity. Here, we provide an overview of serpin origin, function, and dysfunction, focusing on human serpins and ov-serpins, with a hub on SERPINB3.

SerpinB1 regulates homeostatic expansion of IL-17+ γδ and CD4+ Th17 cells

SerpinB1 is an endogenous inhibitor of serine proteases recognized for its anti-inflammatory and host-protective properties. Although loss of serpinB1 in mice does not result in gross immune deregulation, serpinb1a(-/-) mice display increased mortality and inflammation-associated morbidity upon challenge with influenza virus. Here, we show that IL-17A(+) γδ and CD4(+) Th17 cells are already expanded in the lungs of serpinb1a(-/-) mice at steady-state. Both γδ and αβ(+) CD4(+) CCR6(+) T cells isolated from the lungs of naive serpinb1a(-/-) mice displayed a skewed transcriptional profile relative to WT cells, including increased Th17 signature transcripts [Il17a, l17f, and Rorc (RORγt)] and decreased Th1 signature transcripts [Ifng, Cxcr3, and Tbx21 (T-bet)] in γδ T cells. In addition to the lung, IL-17A(+) γδ and CD4(+) Th17 cells were increased in the spleen of naive serpinb1a(-/-) mice, despite normal αβ and γδ T cell development in the thymus. Within the γδ T cell compartment, loss of serpinb1a prompted selective expansion of Vγ4(+) and Vγ6/Vδ1(+) cells, which also displayed elevated expression of the proliferating cell nuclear antigen, Ki-67, and IL-17A. Given that serpinb1a is preferentially expressed in WT IL-17A(+) γδ and CD4(+) Th17 cell subsets vis-à-vis other T cell lineages, our findings reveal a novel function of serpinB1 in limiting untoward expansion of lymphocytes with a Th17 phenotype.

Serum peptidomic profiling identifies a minimal residual disease detection and prognostic biomarker for patients with acute leukemia

The evaluation of minimal residual disease (MRD) in acute leukemia (AL) is currently recognized as a potential critical tool to assess the response and relapse rate of treatments. The present study investigated serum peptides from patients with AL to identify biomarkers that would be useful in providing clinical evaluations and independent prognostic information. The patterns of serum peptides from 123 patients with AL and 49 healthy controls were analyzed using matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Furthermore, diagnostic models of differential peptides were established using the support vector machine (SVM) algorithm to discriminate between the AL patients and healthy controls or between the AL patients with various degrees of remission. Finally, the peptides were applied to evaluate the prognosis of the affected patients. The area under the receiver operating characteristic (ROC) curve (AUC), analyzed using the SVM algorithm to distinguish between the AL patients and healthy controls, was 0.921. The AUC of the models for distinguishing between the newly-diagnosed AL patients and those in AL-hematological complete remission (HCR) and between the AL-HCR patients from those in AL-molecular remission (MR), was 0.824 and 0.919, respectively. A short serum peptide of m/z 4625 was identified to decrease in density in parallel with an increase in the degree of remission, which was used to monitor the MRD level. The intensity of the m/z 4625 peptide was significantly correlated with a poor overall survival (OS). The m/z 4625 peptide was identified to be a partial fragment of SERPINA3. The serum peptide pattern is high in sensitivity and specificity and may be used to discriminate between AL patients with various degrees of remission. The m/z 4625 peptide may be used to monitor the MRD levels and provide independent prognostic information in patients with AL.

Suppression of granzyme B activity and caspase-3 activation in leukaemia cells constitutively expressing the protease inhibitor 9

Immune surveillance against malignant cells is mediated by cytotoxic T-lymphocytes and NK-cells (CTL/NK) that induce apoptosis through the granzyme-B-dependent pathway. The serine protease inhibitor serpinB9/protease inhibitor-9 (PI-9) is a known inhibitor of granzyme B. Ectopic expression of PI-9 in tumour cells has been reported. However, the impact of PI-9 on granzyme-B-induced apoptosis in tumour cells remains unclear. The aim of this study was to investigate the influence of constitutive PI-9 expression in leukaemia cell lines on the activity of granzyme B and apoptosis induction. PI-9 negative (lymphoblastic Jurkat cells; myeloblastic U937 cells) and PI-9-expressing cell lines (myeloblastic K562 cells, EBV-transformed LCL-1 and LCL-2 B-cells, lymphoblastic Daudi cells, AML-R cells f leukaemia and the U937 subclone U937PI-9(+)). For accurate granzyme B activity determination a quantitative substrate (Ac-IEPD-pNA) cleavage assay was established and caspase-3 activation measured for apoptosis assessment. Cells were treated with a cytotoxic granule isolate that has previously been shown to induce apoptosis through granzyme B signalling. We found a robust correlation between constitutive PI-9 expression levels and the suppression of granzyme B activity. Further, inhibition of granzyme B translated into reduced caspase-3 activation. We conclude, suppression of granzyme B initiated apoptosis in PI-9-expressing cells could contribute to immune evasion and the measurement of granzyme B activity with our assay might be a useful predictive marker in immune-therapeutic approaches against cancer.

SerpinB1 is critical for neutrophil survival through cell-autonomous inhibition of cathepsin G

Bone marrow (BM) holds a large reserve of polymorphonuclear neutrophils (PMNs) that are rapidly mobilized to the circulation and tissues in response to danger signals. SerpinB1 is a potent inhibitor of neutrophil serine proteases neutrophil elastase (NE) and cathepsin G (CG). SerpinB1 deficiency (sB1(-/-)) results in a severe reduction of the BM PMN reserve and failure to clear bacterial infection. Using BM chimera, we found that serpinB1 deficiency in BM cells was necessary and sufficient to reproduce the BM neutropenia of sB1(-/-) mice. Moreover, we showed that genetic deletion of CG, but not NE, fully rescued the BM neutropenia in sB1(-/-) mice. In mixed BM chimera and in vitro survival studies, we showed that CG modulates sB1(-/-) PMN survival through a cell-intrinsic pathway. In addition, membrane permeabilization by lysosomotropic agent l-leucyl-l-leucine methyl ester that allows cytosolic release of granule contents was sufficient to induce rapid PMN death through a CG-dependent pathway. CG-mediated PMN cytotoxicity was only partly blocked by caspase inhibition, suggesting that CG cleaves a distinct set of targets during apoptosis. In conclusion, we have unveiled a new cytotoxic function for the serine protease CG and showed that serpinB1 is critical for maintaining PMN survival by antagonizing intracellular CG activity.

Genetic and epigenetic mechanisms collaborate to control SERPINA3 expression and its association with placental diseases

SERPINA3 (Serpin peptidase inhibitor clade A member 3), also known as a1-antichymotrypsin, is a serine protease inhibitor involved in a wide range of biological processes. Recently, it has been shown to be up-regulated in human placental diseases in association with a hypomethylation of the 5' region of the gene. In the present study, we show that the promoter of SERPINA3 is transcriptionally activated by three transcription factors (TFs) (SP1, MZF1 and ZBTB7B), the level of induction being dependent on the rs1884082 single nucleotide polymorphism (SNP) located inside the promoter, the T allele being consistently induced to a higher level than the G, with or without added TFs. When the promoter was methylated, the response to ZBTB7B was allele specific (the G allele was strongly induced, while the T allele was strongly down-regulated). We propose an adaptive model to explain the interest of such a regulation for placental function and homeostasis. Overexpression of SERPINA3 in JEG-3 cells, a trophoblast cell model, decreased cell adhesion to the extracellular matrix and to neighboring cells, but protects them from apoptosis, suggesting a way by which this factor could be deleterious at high doses. In addition, we show in different human populations that the T allele appears to predispose to Intra Uterine Growth Restriction (IUGR), while a G allele at a second SNP located in the second exon (rs4634) increases the risk of preeclampsia. Our results provide mechanistic views inside the involvement of SERPINA3 in placental diseases, through its regulation by a combination of epigenetic, genetic and TF-mediated regulations.

SerpinB1 protects the mature neutrophil reserve in the bone marrow

SerpinB1 is among the most efficient inhibitors of neutrophil serine proteases--NE, CG, and PR-3--and we investigated here its role in neutrophil development and homeostasis. We found that serpinB1 is expressed in all human bone marrow leukocytes, including stem and progenitor cells. Expression levels were highest in the neutrophil lineage and peaked at the promyelocyte stage, coincident with the production and packaging of the target proteases. Neutrophil numbers were decreased substantially in the bone marrow of serpinB1(-/-) mice. This cellular deficit was associated with an increase in serum G-CSF levels. On induction of acute pulmonary injury, neutrophils were recruited to the lungs, causing the bone marrow reserve pool to be completely exhausted in serpinB1(-/-) mice. Numbers of myeloid progenitors were normal in serpinB1(-/-) bone marrow, coincident with the absence of target protease expression at these developmental stages. Maturation arrest of serpinB1(-/-) neutrophils was excluded by the normal CFU-G growth in vitro and the normal expression in mature neutrophils of early and late differentiation markers. Normal absolute numbers of proliferating neutrophils and pulse-chase kinetic studies in vivo showed that the bone marrow deficit in serpinB1(-/-) mice was largely restricted to mature, postmitotic neutrophils. Finally, upon overnight culture, apoptosis and necrosis were greater in purified bone marrow neutrophils from serpinB1(-/-) compared with WT mice. Collectively, these findings demonstrate that serpinB1 sustains a healthy neutrophil reserve that is required in acute immune responses.

Serpins flex their muscle: I. Putting the clamps on proteolysis in diverse biological systems

Serpins compose the largest superfamily of peptidase inhibitors and are well known as regulators of hemostasis and thrombolysis. Studies using model organisms, from plants to vertebrates, now show that serpins and their unique inhibitory mechanism and conformational flexibility are exploited to control proteolysis in molecular pathways associated with cell survival, development, and host defense. In addition, an increasing number of non-inhibitory serpins are emerging as important elements within a diversity of biological systems by serving as chaperones, hormone transporters, or anti-angiogenic factors.

Proteomic studies of nitrated alpha-synuclein microglia regulation by CD4+CD25+ T cells

Microglial inflammatory responses affect Parkinson's disease (PD) associated nigrostriatal degeneration. This is triggered, in measure, by misfolded, nitrated alpha-synuclein (N-alpha-syn) contained within Lewy bodies that are released from dying or dead dopaminergic neurons into the extravascular space. N-alpha-syn-stimulated microglial immunity is regulated by CD4+ T cell subset. Indeed, CD4+CD25+ regulatory T cells (Treg) induce neuroprotective immune responses. This is seen in rodent models of stroke, amyotrophic lateral sclerosis, human immunodeficiency virus associated neurocognitive disorders, and PD. To elucidate the mechanism for Treg-mediated microglial neuroregulatory responses, we used a proteomic platform integrating difference gel electrophoresis and tandem mass spectrometry peptide sequencing. These tests served to determine consequences of Treg on the N-alpha-syn stimulated microglia. The data demonstrated that Treg substantially alter the microglial proteome in response to N-alpha-syn. This is seen through Treg abilities to suppress microglial proteins linked to cell metabolism, migration, protein transport and degradation, redox biology, cytoskeletal, and bioenergetic activities. We conclude that Treg modulate the N-alpha-syn microglial proteome and, in this way, can slow the tempo and course of PD.

Serine protease inhibitor 8 is a novel immunohistochemical marker for neuroendocrine tumors of the pancreas

OBJECTIVES/METHODS

The intracellular serine protease inhibitor 8 (SERPINB8) is expressed by squamous epithelium, monocytes, and a subset of neuroendocrine cells. Using immunohistochemistry, we now have further investigated the expression of SERPINB8 in normal neuroendocrine cells and its potential use as a marker to identify neuroendocrine tumors of the pancreas.

RESULTS

In normal neuroendocrine tissues, strongest SERPINB8 expression was detected in islets of Langerhans of the pancreas. Moderate SERPINB8 expression was observed in neuroendocrine cells of the thyroid, adrenal cortex, colon, and pituitary gland. Fluorescent double staining revealed that in the pancreas, SERPINB8 is specifically expressed by insulin-producing beta cells. In a panel of 20 patients with pancreatic islet cell tumors, however, SERPINB8 was broadly expressed and not restricted to insulinomas. In islet cell tumors, SERPINB8 had a similar diagnostic sensitivity as compared with the widely used neuroendocrine markers chromogranin A and synaptophysin. When SERPINB8 was combined with these 2 markers, an even higher diagnostic sensitivity was reached. In contrast, exocrine adenocarcinomas of the pancreas showed no SERPINB8 expression.

CONCLUSIONS

The SERPINB8 is expressed in normal neuroendocrine cells of several organs as well as in neuroendocrine tumors of the pancreas, where it can be used as an additional diagnostic immunohistochemical marker.

Nitrated {alpha}-synuclein-induced alterations in microglial immunity are regulated by CD4+ T cell subsets

Microglial inflammatory neuroregulatory activities affect the tempo of nigrostriatal degeneration during Parkinson's disease (PD). Such activities are induced, in part, by misfolded, nitrated alpha-synuclein (N-alpha-syn) within Lewy bodies released from dying or dead dopaminergic neurons. Such pathobiological events initiate innate and adaptive immune responses affecting neurodegeneration. We posit that the neurobiological activities of activated microglia are affected by cell-protein and cell-cell contacts, in that microglial interactions with N-alpha-syn and CD4(+) T cells substantively alter the microglial proteome. This leads to alterations in cell homeostatic functions and disease. CD4(+)CD25(+) regulatory T cells suppress N-alpha-syn microglial-induced reactive oxygen species and NF-kappaB activation by modulating redox-active enzymes, cell migration, phagocytosis, and bioenergetic protein expression and cell function. In contrast, CD4(+)CD25(-) effector T cells exacerbate microglial inflammation and induce putative neurotoxic responses. These data support the importance of adaptive immunity in the regulation of Parkinson's disease-associated microglial inflammation.

High levels of granzyme B expression in invasive cervical carcinoma correlates to poor response to treatment

The present study assessed, in cervical carcinoma, expression levels of seven immune response genes and sought correlation to response to treatment. The expression levels of CD28, CTLA4, ICOS, ICOSL, CD80 and CD86 and granzyme B genes were assessed by real-time RT-PCR in pre-treatment tumor fragments. During the six-month follow-up after treatment, 8 patients presented tumor and 10 survived free of tumor. The only gene whose expression levels were higher in patients with poor outcome (p = 0.03) was granzyme B. Further evaluation, in adequately powered prospective studies is warranted to confirm the data and to translate this observation to the clinical setting.

Granzyme B and natural killer (NK) cell death

Granzyme B is a unique serine protease, which plays a crucial role for target cell death. Several mechanisms of delivery of granzyme B to target cells have been recently identified. Granzyme B directly activates Bid, a specific substrate for granzyme B, resulting in caspase activation. Granzyme B efficiently cleaves many prominent autoantigens, and the hypothesis that autoantibodies arise when cryptic determinants are revealed to the immune system has been proposed. Some autoantibodies directed against granzyme B-specific neoepitopes are present in serum from patients with autoimmune diseases. In the tissues from autoimmune diseases, granzyme B might play an important role for disease progression (i.e., rheumatoid arthritis synovium) or inhibition (i.e., regulatory T cells). We have identified a novel type of activation-induced cell death (granzyme B leakage-induced cell death). Activation-induced natural killer (NK) cell death is accompanied by the leakage of granzyme B from intracellular granules into the cytoplasm, and it triggers apoptosis by directing Bid to mitochondrial membranes. An excess of "leaked" granzyme B over its inhibitor, serpin proteinase inhibitor 9, is a major determinant of cell death. The role of granzyme B in autoimmunity and its influence on NK cell death are discussed.

Conformational modification of serpins transforms leukocyte elastase inhibitor into an endonuclease involved in apoptosis

The best-characterized biochemical feature of apoptosis is degradation of genomic DNA into oligonucleosomes. The endonuclease responsible for DNA degradation in caspase-dependent apoptosis is caspase-activated DNase. In caspase-independent apoptosis, different endonucleases may be activated according to the cell line and the original insult. Among the known effectors of caspase-independent cell death, L-DNase II (LEI [leukocyte elastase inhibitor]-derived DNase II) has been previously characterized by our laboratory. We have thus shown that this endonuclease derives from the serpin superfamily member LEI by posttranslational modification (A. Torriglia, P. Perani, J. Y. Brossas, E. Chaudun, J. Treton, Y. Courtois, and M. F. Counis, Mol. Cell. Biol. 18:3612-3619, 1998). In this work, we assessed the molecular mechanism involved in the change in the enzymatic activity of this molecule from an antiprotease to an endonuclease. We report that the cleavage of LEI by elastase at its reactive center loop abolishes its antiprotease activity and leads to a conformational modification that exposes an endonuclease active site and a nuclear localization signal. This represents a novel molecular mechanism for a complete functional conversion induced by changing the conformation of a serpin. We also show that this molecular transformation affects cellular fate and that both endonuclease activity and nuclear translocation of L-DNase II are needed to induce cell death.

Analysis of gene expression identifies candidate molecular markers in nasopharyngeal carcinoma using microdissection and cDNA microarray

PURPOSE

Microarray analysis was used to bring a comprehensive insight into underlying molecular mechanisms and obtain a whole assessment of aberrant gene expression in nasopharyngeal carcinoma (NPC).

METHODS

Combined with microdissection, gene expression profiles in 23 NPCs and 10 nontumor nasopharyngeal epithelial tissue samples were analyzed.

RESULTS

Gene expression patterns suggested the dysregulation of the GTP/GDP-bound Ras cycle and an abnormal hyperactivity of cell cycle in NPC. Alterations in the WNT pathway suggest that this pathway may be activated in NPC. A 6-feature weighted-voting model was chosen because it represented the main characteristics of NPCs and predicted NPCs most accurately from the nontumor tissues (33 of 34 correct calls; 97.1% accuracy, Fisher's exact test, P value = 8.389 x 10(-8)).

CONCLUSIONS

The data generated in this study represent a comprehensive list of genes aberrantly regulated in NPC. The 6-feature weighted-voting model may provide an extensive list of potential molecular markers for early diagnosis.

Modulation and redistribution of proteinase inhibitor 8 (Serpinb8) during kidney regeneration

BACKGROUND

The intracellular serpin, proteinase inhibitor 8 (PI8/Serpinb8), can inhibit furin, a prohormone convertase involved in inflammation, prohormone processing and extracellular matrix remodeling. Unilateral ureteral obstruction (UUO) is a well-characterized model of kidney disease associated with interstitial fibrosis, where recovery involves cellular proliferation and extracellular matrix remodeling. Given the presence of mouse PI8 (mPI8) in kidney, the UUO technique was used to investigate its potential role in kidney disease and regeneration.

METHODS

RT-PCR and in situ hybridization was used to assess PI8 mRNA in kidney sections. Immunohistochemistry was used to examine mPI8 distribution in normal kidney, and following reversal of UUO.

RESULTS

mPI8 mRNA was detected in whole kidney by RT-PCR, and by in situ hybridization in convoluted tubules of the renal cortex and medulla. In normal and control contralateral unobstructed kidneys, mPI8 was within the ascending limb and convoluted section of the distal tubules. PI8 distribution did not change in UUO kidney, but was significantly altered in reversed UUO kidney, appearing in regions containing nephrons undergoing remodeling. These included regenerating proximal and distal tubules and glomeruli.

CONCLUSIONS

mPI8 distribution alters during kidney regeneration, possibly to control a prohormone convertase involved in inflammation or tissue repair.

Targeted disruption of SPI3/Serpinb6 does not result in developmental or growth defects, leukocyte dysfunction, or susceptibility to stroke

Protease inhibitor 6 (PI-6/SERPINB6) is a widely expressed nucleocytoplasmic serpin. It inhibits granulocyte cathepsin G and neuronal neuropsin, and it is thought to protect cells from death caused by ectopic release or internalization of protease during stress such as infection or cerebral ischemia. To probe the biological functions of PI-6, we generated mice lacking its ortholog (SPI3/Serpinb6). SPI3-deficient mice developed normally and were fertile, and no abnormal pathology or increased sensitivity to cerebral ischemia was observed. There were no perturbations in leukocyte development or numbers, and recruitment of leukocytes to the peritoneal cavity was normal. SPI3-deficient mice were equally susceptible as wild-type mice to systemic Candida albicans infection, although there was a slight decrease in the ability of neutrophils from SPI3-deficient mice to kill C. albicans in vitro. Increased levels of a related inhibitor Serpinb1 (monocyte/neutrophil elastase inhibitor) in the tissues of targeted mice suggests that compensation by other serpins reduces the impact of SPI3 deficiency in these animals and may explain the lack of a more obvious phenotype.

Enhancement of DNA vaccine potency by coadministration of a tumor antigen gene and DNA encoding serine protease inhibitor-6

Serine protease inhibitor 6 (SPI-6), also called Serpinb9, inhibits granzyme B and thus may provide a method for delaying apoptotic cell death in dendritic cells. We have previously enhanced DNA vaccine potency by targeting antigen to MHC antigen presentation pathways, using proteins such as Mycobacterium tuberculosis heat shock protein 70, calreticulin, domain II of Pseudomonas aeruginosa exotoxin A, or the sorting signal of the lysosome-associated membrane protein type 1. In this study, we explored intradermal coadministration of DNA encoding SPI-6 with DNA constructs encoding human papillomavirus type 16 E7 linked to these intracellular targeting molecules for its ability to generate E7-specific CD8+ T-cell immune responses and E7-specific antitumor effects. This combination of strategies resulted in significantly increased E7-specific CD8+ T-cell and CD4+ Th1-cell responses, enhanced tumor treatment ability, and stronger tumor protection when compared with vaccination without SPI-6. Among these targeting strategies tested, mice vaccinated with Sig/E7/lysosome-associated membrane protein type 1 mixed with SPI-6 showed the greatest fold increase in E7-specific CD8+ T cells ( approximately 5-fold). Vaccination with a nonfunctional mutant of SPI-6 did not result in immune enhancement, indicating that enhancement was dependent on the antiapoptotic function of SPI-6. Our results suggest that DNA vaccines combining strategies that enhance MHC class I and II antigen processing with SPI-6 have potential clinical implications for control of viral infection and neoplasia.

Intracellular serpin SERPINB6 (PI6) is abundantly expressed by human mast cells and forms complexes with beta-tryptase monomers

SERPINB6 (PI6) is a member of the intracellular serine protease inhibitors (serpins). Previous studies showed that SERPINB6 is localized mainly in the cytoplasm of endothelial cells, some epithelial cells, monocytes, and neutrophils. In these cells SERPINB6 is thought to prevent cellular damage by scavenging leaking lysosomal proteases. We show here, using novel, well-defined monoclonal antibodies, that SERPINB6 is abundantly expressed by mast cells in all organs and by the human mast cell line HMC-1. Gel filtration experiments revealed that the latter cells contain a high-molecular-weight form of SERPINB6, which consists of sodium dodecyl sulfate (SDS)-stable complexes of this inhibitor with monomeric beta-tryptase. Expression of SERPINB6 by mast cells was compared with those of tryptase and CD117 (c-kit) in biopsies from patients with different forms of mast cell disease. In all cases the lesional mast cells expressed SERPINB6, and, in diffuse cutaneous mastocytosis and mastocytoma, SERPINB6 was expressed by a substantially higher number of mast cells when compared with tryptase. In conclusion, SERPINB6 is abundantly expressed by normal mast cells and by mast cells in mastocytoma lesions. We suggest that in mast cells, SERPINB6 serves to regulate the activity of endogenous beta-tryptase in the cytoplasm.

Monoclonal LYM-1 antibody-dependent cytolysis by human neutrophils exposed to GM-CSF: auto-regulation of target cell attack by cathepsin G

Murine monoclonal antibody (mAb) Lym-1 is an immunoglobulin G2a specific for certain human leukocyte antigen-DR variants expressed on the surface of malignant B cells. It has been proposed for serotherapy in patients with B lymphomas. We have previously shown that mAb Lym-1 synergizes with granulocyte macrophage-colony stimulating factor to promote Raji B-lymphoid cell lysis by human neutrophils via the intervention of neutrophil Fc receptors type II and D-mannose-inhibitable interactions between CD11b-CD18 integrins and CD66b glycoproteins. Here, we provide evidence that the process is oxygen-independent by inference related to the release of primary granules and is regulated by cathepsin G activity. The lysis was indeed reproduced by replacing normal neutrophils with cells from three patients suffering from chronic granulomatous disease, i.e., neutrophils genetically incapable of generating oxidants. Moreover, the lysis was inhibited by the serine protease inhibitor 3,4-dichloroisocoumarin and by Z-glycyl-leucyl-phenyl-chloromethyl ketone (Z-Gly-Leu-Phe-CMK), which blocks cathepsin G. Conversely, the lysis was unaffected by N-methoxysuccinyl-alanyl-alanyl-prolyl-alanyl-CMK (MeOSuc-Ala-Ala-Pro-Ala-CMK; elastase inhibitor) and MeOSuc-Ala-Ala-Pro-valine (Val)-CMK, which inhibits elastase and proteinase 3. The ability of neutrophils, engaged in cytolysis, to release cathepsin G was proved by detecting this enzymatic activity spectrophotometrically and immunocytochemically. Moreover, inhibition of cathepsin G activity by concentrations of Z-Gly-Leu-Phe-CMK, incapable of affecting elastase activity, was found to reduce the release of elastase and myeloperoxidase from neutrophils under conditions similar to those used for cytolytic assays. These findings suggest that neutrophils auto-regulate their lytic efficiency by controlling the exocytosis of primary granules via their cathepsin G activity.

Neutrophil cathepsin G promotes detachment-induced cardiomyocyte apoptosis via a protease-activated receptor-independent mechanism

Cathepsin G is a neutrophil-derived serine protease that contributes to tissue damage at sites of inflammation. The actions of cathepsin G are reported to be mediated by protease-activated receptor (PAR)-4 (a thrombin receptor) in human platelets. This study provides the first evidence that cathepsin G promotes inositol 1,4,5-trisphosphate accumulation, activates ERK, p38 MAPK, and AKT, and decreases contractile function in cardiomyocytes. Because some cathepsin G responses mimic cardiomyocyte activation by thrombin, a role for PARs was considered. Cathepsin G markedly activates phospholipase C and p38 MAPK in cardiomyocytes from PAR-1-/- mice, but it fails to activate phospholipase C, ERK, p38 MAPK, or AKT in PAR-1- or PAR-4-expressing PAR-1-/- fibroblasts (which display robust responses to thrombin). These results argue that PAR-1 does not mediate the actions of cathepsin G in cardiomyocytes, and neither PAR-1 nor PAR-4 mediates the actions of cathepsin G in fibroblasts. Of note, prolonged incubation of cardiomyocytes with cathepsin G results in the activation of caspase-3, cleavage of FAK and AKT, sarcomeric disassembly, cell rounding, cell detachment from underlying matrix, and morphologic features of apoptosis. Inhibition of Src family kinases or caspases (with PP1 or benzyloxycarbonyl-VAD-fluoromethyl ketone, respectively) delays FAK and AKT cleavage and cardiomyocyte detachment from substrate. Collectively, these studies describe novel cardiac actions of cathepsin G that do not require PARs and are predicted to assume functional importance at sites of interstitial inflammation in the heart.

Proteinases and their inhibitors in the immune system

The most important roles of proteinases in the immune system are found in apoptosis and major histocompatibility complex (MHC) class II-mediated antigen presentation. A variety of cysteine proteinases, serine proteinases, and aspartic proteinases as well as their inhibitors are involved in the regulation of apoptosis in neutrophils, monocytes, and dendritic cells, in selection of specific B and T lymphocytes, and in killing of target cells by cytotoxic T cells and natural killer cells. In antigen presentation, endocytosed antigens are digested into antigenic peptides by both aspartic and cysteine proteinases. In parallel, MHC class II molecules are processed by aspartic and cysteine proteinases to degrade the invariant chain that occupies the peptide-binding site. Proteinase activity in these processes is highly regulated, particularly by posttranslational activation and the balance between active proteinases and specific endogenous inhibitors such as cystatins, thyropins, and serpins. This article discusses the regulation of proteolytic processes in apoptosis and antigen presentation in immune cells and the consequences of therapeutic interference in the balance of proteinases and their inhibitors.

Apoptosis induced by Na+/H+ antiport inhibition activates the LEI/L-DNase II pathway

L-DNase II is derived from its precursor leucocyte elastase inhibitor (LEI) by post-translational modification. In vitro, the conversion of LEI into L-DNase II can be induced by incubation of LEI at an acidic pH. In this study, we proposed to analyze the effects of intracellular acidification on this transformation. Amiloride derivatives, like hexamethylene amiloride (HMA), are known to provoke a decrease of cytosolic pH by inhibiting the Na(+)/H(+) antiport. In BHK cells, treatment with HMA-induced apoptosis accompanied by an increase in L-DNase II immunoreactivity and L-DNase II enzymatic activity. Overexpression of L-DNase II precursor led to a significant increase of apoptosis in these cells supporting the involvement of L-DNase II in HMA induced apoptosis. As previously shown in other cells, etoposide-induced apoptosis did not activate L-DNase. On the contrary, LEI overexpression significantly increased cell survival in etoposide-induced apoptosis. Together these results suggest differential roles of LEI and L-DNase II in response to different types of apoptotic inducers.

Cloning and characterization of four Anopheles gambiae serpin isoforms, differentially induced in the midgut by Plasmodium berghei invasion

The genomic locus SRPN10 of the malaria vector Anopheles gambiae codes for four alternatively spliced serine protease inhibitors of the serpin superfamily. The four 40- to 42-kDa isoforms differ only at their C terminus, which bears the reactive site loop, and exhibit protein sequence similarity with other insect serpins and mammalian serpins of the ovalbumin family. Inhibition experiments with recombinant purified SRPN10 serpins reveal distinct and specific inhibitory activity of three isoforms toward different proteases. All isoforms are mainly expressed in the midgut but also in pericardial cells and hemocytes of the mosquito. The cellular localization of SRPN10 serpins is nucleocytoplasmic in pericardial cells, in hemocytes and in a hemocyte-like mosquito cell line, but in the gut the proteins are mostly localized in the nucleus. Although the transcript levels of all SRPN10 isoforms are marginally affected by bacterial challenge, the transcripts of two isoforms (KRAL and RCM) are induced in female mosquitoes in response to midgut invasion by Plasmodium berghei ookinetes. The KRAL and RCM SRPN10 isoforms represent new potential markers to study the ookinete midgut invasion process in anopheline mosquitoes.

The intracellular granzyme B inhibitor, proteinase inhibitor 9, is up-regulated during accessory cell maturation and effector cell degranulation, and its overexpression enhances CTL potency

Granzyme B (grB) is a serine proteinase released by cytotoxic lymphocytes (CLs) to kill abnormal cells. GrB-mediated apoptotic pathways are conserved in nucleated cells; hence, CLs require mechanisms to protect against ectopic or misdirected grB. The nucleocytoplasmic serpin, proteinase inhibitor 9 (PI-9), is a potent inhibitor of grB that protects cells from grB-mediated apoptosis in model systems. Here we show that PI-9 is present in CD4(+) cells, CD8(+) T cells, NK cells, and at lower levels in B cells and myeloid cells. PI-9 is up-regulated in response to grB production and degranulation, and associates with grB-containing granules in activated CTLs and NK cells. Intracellular complexes of PI-9 and grB are evident in NK cells, and overexpression of PI-9 enhances CTL potency, suggesting that cytoplasmic grB, which may threaten CL viability, is rapidly inactivated by PI-9. Because dendritic cells (DCs) acquire characteristics similar to those of target cells to activate naive CD8(+) T cells and therefore may also require protection against grB, we investigated the expression of PI-9 in DCs. PI-9 is evident in thymic DCs (CD3(-), CD4(+), CD8(-), CD45(+)), tonsillar DCs, and DC subsets purified from peripheral blood (CD16(+) monocytes and CD123(+) plasmacytoid DCs). Furthermore, PI-9 is expressed in monocyte-derived DCs and is up-regulated upon TNF-alpha-induced maturation of monocyte-derived DCs. In conclusion, the presence and subcellular localization of PI-9 in leukocytes and DCs are consistent with a protective role against ectopic or misdirected grB during an immune response.

Functional significance of the perforin/granzyme cell death pathway

Perforin/granzyme-induced apoptosis is the main pathway used by cytotoxic lymphocytes to eliminate virus-infected or transformed cells. Studies in gene-disrupted mice indicate that perforin is vital for cytotoxic effector function; it has an indispensable, but undefined, role in granzyme-mediated apoptosis. Despite its vital importance, the molecular and cellular functions of perforin and the basis of perforin and granzyme synergy remain poorly understood. The purpose of this review is to evaluate critically recent findings on cytotoxic granule-mediated cell death and to assess the functional significance of postulated cell-death pathways in appropriate pathophysiological contexts, including virus infection and susceptibility to experimental or spontaneous tumorigenesis.

Host defense responses to infection by Mycobacterium tuberculosis. Induction of IRF-1 and a serine protease inhibitor

Alveolar macrophages and newly recruited monocytes are targets of infection by Mycobacterium tuberculosis. Therefore, we examined the expression of interferon regulatory factor 1 (IRF-1), which plays an important role in host defense against M. tuberculosis, in undifferentiated and differentiated cells. Infection induced IRF-1 in both. IRF-1 from undifferentiated, uninfected monocytic cell lines was modified during extraction to produce specific species that were apparently smaller than intact IRF-1. After infection by M. tuberculosis or differentiation, intact IRF-1 was recovered. Subcellular fractions were assayed for the ability to modify IRF-1 or inhibit its modification. A serine protease on the cytoplasmic surface of an organelle or vesicle in the "lysosomal/mitochondrial" fraction from undifferentiated cells was responsible for the modification of IRF-1. Thus, the simplest explanation of the modification is cleavage of IRF-1 by the serine protease. Recovery of intact IRF-1 correlated with induction of a serine protease inhibitor that was able to significantly reduce the modification of IRF-1. The inhibitor was present in the cytoplasm of M. tuberculosis-infected or -differentiated cells. It is likely that induction of both IRF-1 and the serine protease inhibitor in response to infection by M. tuberculosis represent host defense mechanisms.

Influence of effector molecules on the CD8(+) T cell response to infection

Expansion and contraction of antigen-specific CD8(+) T cells after infection or vaccination results in stable memory. Recent evidence demonstrates that anti-microbial effector molecules such as perforin and IFN-gamma regulate specific aspects of CD8(+) T cell homeostasis by mechanisms that may be dependent or independent of pathogen clearance.

Comparison of human chromosome 6p25 with mouse chromosome 13 reveals a greatly expanded ov-serpin gene repertoire in the mouse

Ov-serpins are intracellular proteinase inhibitors implicated in the regulation of tumor progression, inflammation, and cell death. The 13 human ov-serpin genes are clustered at 6p25 (3 genes) and 18q21 (10 genes), and share common structures. We show here that a 1-Mb region on mouse chromosome 13 contains at least 15 ov-serpin genes compared with the three ov-serpin genes within 0.35 Mb at human 6p25 (SERPINB1 (MNEI), SERPINB6 (PI-6), SER-PINB9 (PI-9)). The mouse serpins have characteristics of functional inhibitors and fall into three groups on the basis of similarity to MNEI, PI-6, or PI-9. The genes map between the mouse orthologs of the Werner helicase interacting protein and NAD(P)H menadioine oxidoreductase 2 genes, in a region that contains the markers D13Mit136 and D13Mit116. They have the seven-exon structure typical of human 6p25 ov-serpin genes, with identical intron phasing. Most show restricted patterns of expression, with common sites of synthesis being the placenta and immune tissue. Compared with human, this larger mouse serpin repertoire probably reflects the need to regulate a larger proteinase repertoire arising from differing evolutionary pressures on the reproductive and immune systems.

SERPINB12 is a novel member of the human ov-serpin family that is widely expressed and inhibits trypsin-like serine proteinases

Members of the human serpin family regulate a diverse array of serine and cysteine proteinases associated with essential biological processes such as fibrinolysis, coagulation, inflammation, cell mobility, cellular differentiation, and apoptosis. Most serpins are secreted and attain physiologic concentrations in the blood and extracellular fluids. However, a subset of the serpin superfamily, the ov-serpins, also resides intracellularly. Using high throughput genomic sequence, we identified a novel member of the human ov-serpin gene family, SERPINB12. The gene mapped to the ov-serpin cluster at 18q21 and resided between SERPINB5 (maspin) and SERPINB13 (headpin). The presence of SERPINB12 in silico was confirmed by cDNA cloning. Expression studies showed that SERPINB12 was expressed in many tissues, including brain, bone marrow, lymph node, heart, lung, liver, pancreas, testis, ovary, and intestines. Based on the presence of Arg and Ser at the reactive center of the RSL, SERPINB12 appeared to be an inhibitor of trypsin-like serine proteinases. This hypothesis was confirmed because recombinant SERPINB12 inhibited human trypsin and plasmin but not thrombin, coagulation factor Xa, or urokinase-type plasminogen activator. The second-order rate constants for the inhibitory reactions were 2.5 +/- 1.6 x 10(5) and 1.6 +/- 0.2 x 10(4) M(-1) S(-1), respectively. These data show that SERPINB12 encodes for a new functional member of the human ov-serpin family.

Nucleocytoplasmic distribution of the ovalbumin serpin PI-9 requires a nonconventional nuclear import pathway and the export factor Crm1

Proteinase inhibitor 9 (PI-9) is a human serpin present in the cytoplasm of cytotoxic lymphocytes and epithelial cells. It inhibits the cytotoxic lymphocyte granule proteinase granzyme B (graB) and is thought to protect cytotoxic lymphocytes and bystander cells from graB-mediated apoptosis. Following uptake into cells, graB promotes DNA degradation, rapidly translocating to the nucleus, where it binds a nuclear component. PI-9 should therefore be found in cytotoxic lymphocyte and bystander cell nuclei to ensure complete protection against graB. Here we demonstrate by microscopy and subcellular fractionation experiments that PI-9 is present in the nuclei of human cytotoxic cells, endothelial cells, and epithelial cells. We also show that the related serpins, PI-6, monocyte neutrophil elastase inhibitor (MNEI), PI-8, plasminogen activator inhibitor 2 (PAI-2), and the viral serpin CrmA exhibit similar nucleocytoplasmic distributions. Because these serpins lack classical nuclear localization signals and are small enough to diffuse through nuclear pores, we investigated whether import occurs actively or passively. Large (approximately 70 kDa) chimeric proteins comprising PI-9, PI-6, PI-8, MNEI, or PAI-2 fused to green fluorescent protein (GFP) show similar nucleocytoplasmic distributions to the parent proteins, indicating that nuclear import is active. By contrast, CrmA-GFP is excluded from nuclei, indicating that CrmA is not actively imported. In vitro nuclear transport assays show that PI-9 accumulates at a rate above that of passive diffusion, that it requires cytosolic factors but not ATP, and that it does not bind an intranuclear component. Furthermore, PI-9 is exported from nuclei via a leptomycin B-sensitive pathway, implying involvement of the export factor Crm1p. We conclude that the nucleocytoplasmic distribution of PI-9 and related serpins involves a nonconventional nuclear import pathway and Crm1p.

Squamous cell carcinoma antigen suppresses radiation-induced cell death

Previous study has demonstrated that squamous cell carcinoma antigen (SCCA) 1 attenuates apoptosis induced by TNF alpha, NK cell or anticancer drug. In this study, we have examined the effect of SCCA2, which is highly homologous to SCCA1, but has different target specificity, against radiation-induced apoptosis, together with that of SCCA1. We demonstrated that cell death induced by radiation treatment was remarkably suppressed not only in SCCA1 cDNA-transfected cells, but also in SCCA2 cDNA-transfected cells. In these transfectants, caspase 3 activity and the expression of activated caspase 9 after radiation treatment were suppressed. Furthermore, the expression level of phosphorylated p38 mitogen-activated protein kinase (p38 MAPK) was suppressed compared to that of the control cells. The expression level of upstream stimulator of p38 MAPK, phosphorylated MKK3/MKK6, was also suppressed in the radiation-treated cells. Thus, both SCCA1 and SCCA2 may contribute to survival of the squamous cells from radiation-induced apoptosis by regulating p38 MAPK pathway.