Cloning and chromosomal assignment of a human cDNA encoding a T cell- and natural killer cell-specific trypsin-like serine protease

Dynamic Proteomic Changes in Tumor and Immune Organs Reveal Systemic Immune Response to Tumor Development

In orthotopic mouse tumor models, tumor progression is a complex process, involving interactions among tumor cells, host cell-derived stromal cells, and immune cells. Much attention has been focused on the tumor and its tumor microenvironment, while the host's macroenvironment including immune organs in response to tumorigenesis is poorly understood. Here, we report a temporal proteomic analysis on a subcutaneous tumor and three immune organs (LN, MLN, and spleen) collected on Days 0, 3, 7, 10, 14, and 21 after inoculation of mouse forestomach cancer cells in a syngeneic mouse model. Bioinformatics analysis identified key biological processes during distinct tumor development phases, including an initial acute immune response, the attack by the host immune system, followed by the adaptive immune activation, and the build-up of extracellular matrix. Proteomic changes in LN and spleen largely recapitulated the dynamics of the immune response in the tumor, consistent with an acute defense response on D3, adaptive immune response on D10, and immune evasion by D21. In contrast, the immune response in MLN showed a gradual and sustained activation, suggesting a delayed response from a distal immune organ. Combined analyses of tumors and host immune organs allowed the identification of potential therapeutic targets. A proof-of-concept experiment demonstrated that significant growth reduction can be achieved by dual inhibition of MEK and DDR2. Together, our temporal proteomic dataset of tumors and immune organs provides a useful resource for understanding the interaction between tumors and the immune system and has the potential for identifying new therapeutic targets for cancer treatment.

Cross-species single-cell transcriptomic analysis of animal gastric antrum reveals intense porcine mucosal immunity

As an important part of the stomach, gastric antrum secretes gastrin which can regulate acid secretion and gastric emptying. Although most cell types in the gastric antrum are identified, the comparison of cell composition and gene expression in the gastric antrum among different species are not explored. In this study, we collected antrum epithelial tissues from human, pig, rat and mouse for scRNA-seq and compared cell types and gene expression among species. In pig antral epithelium, we identified a novel cell cluster, which is marked by high expression of AQP5, F3, CLCA1 and RRAD. We also discovered that the porcine antral epithelium has stronger immune function than the other species. Further analysis revealed that this may be due to the insufficient function of porcine immune cells. Together, our results replenish the information of multiple species of gastric antral epithelium at the single cell level and provide resources for understanding the homeostasis maintenance and regeneration of gastric antrum epithelium.

Tryptase and Exogenous Trypsin: Mechanisms and Ophthalmic Applications

Ocular injuries caused by inflammation, surgery or accidents are subject to a physiological healing process that ultimately restores the structure and function of the damaged tissue. Tryptase and trypsin are essential component of this process and they play a role in promoting and reducing the inflammatory response of tissues, respectively. Following injury, tryptase is endogenously produced by mast cells and can exacerbate the inflammatory response both by stimulating neutrophil secretion, and through its agonist action on proteinase-activated receptor 2 (PAR2). In contrast, exogenously introduced trypsin promotes wound healing by attenuating inflammatory responses, reducing oedema and protecting against infection. Thus, trypsin may help resolve ocular inflammatory symptoms and promote faster recovery from acute tissue injury associated with ophthalmic diseases. This article describes the roles of tryptase and exogenous trypsin in affected tissues after onset of ocular injury, and the clinical applications of trypsin injection.

Proteolysis by Granzyme B Enhances Presentation of Autoantigenic Peptidylarginine Deiminase 4 Epitopes in Rheumatoid Arthritis

Proteolysis of autoantigens can alter normal MHC class II antigen processing and has been implicated in the induction of autoimmune diseases. Many autoantigens are substrates for the protease granzyme B (GrB), but the mechanistic significance of this association is unknown. Peptidylarginine deiminase 4 (PAD4) is a frequent target of autoantibodies in patients with rheumatoid arthritis (RA) and a substrate for GrB. RA is strongly associated with specific MHC class II alleles, and elevated levels of GrB and PAD4 are found in the joints of RA patients, suggesting that GrB may alter the presentation of PAD4 by RA-associated class II alleles. In this study, complementary proteomic and immunologic approaches were utilized to define the effects of GrB cleavage on the structure, processing, and immunogenicity of PAD4. Hydrogen-deuterium exchange and a cell-free MHC class II antigen processing system revealed that proteolysis of PAD4 by GrB induced discrete structural changes in PAD4 that promoted enhanced presentation of several immunogenic peptides capable of stimulating PAD4-specific CD4+ T cells from patients with RA. This work demonstrates the existence of PAD4-specific T cells in patients with RA and supports a mechanistic role for GrB in enhancing the presentation of autoantigenic CD4+ T cell epitopes.

New mechanism of organophosphorus pesticide-induced immunotoxicity

Organophosphorus pesticides (OPs) are widely used throughout the world as insecticides in agriculture and as eradicating agents for termites around homes. The main toxicity of OPs is neurotoxicity, which is caused by the inhibition of acetylcholinesterase. OPs also affect the immune response, including effects on antibody production, interleukin-2 production, T cell proliferation, decrease of CD5 cells, and increases of CD26 cells and autoantibodies, Th1/Th2 cytokine profiles, and the inhibition of natural killer (NK) cell, lymphokine-activated killer (LAK) cell, and cytotoxic T lymphocyte (CTL) activities. However, there have been few studies of the mechanism of OP-induced immunotoxicity, especially the mechanism of OP-induced inhibition of cytolytic activity of killer cells. This study reviews new mechanisms of OP-induced inhibition of the activities of NK cells, LAK cells, and CTLs. It has been reported that NK cells, LAK cells, and CTLs induce cell death in tumors or virus-infected target cells by two main mechanisms. The first mechanism is direct release of cytolytic granules that contain the pore-forming protein perforin, several serine proteases termed granzymes, and granulysin by exocytosis to kill target cells, which is called the granule exocytosis pathway. The second mechanism is mediated by the Fas ligand (Fas-L)/Fas pathway, in which FasL (CD95 L), a surface membrane ligand of the killer cell cross links with the target cell's surface death receptor Fas (CD95) to induce apoptosis of the target cells. To date, it has been reported that OPs inhibit NK cell, LAK cell, and CTL activities by at least the following three mechanisms: 1) OPs impair the granule exocytosis pathway of NK cells, LAK cells, and CTLs by inhibiting the activity of granzymes, and by decreasing the intracellular levels of perforin, granzyme A, and granulysin, which were mediated by inducing degranulation of NK cells and by inhibiting the transcription of the mRNAs of perforin, granzyme A, and granulysin. 2) OPs impair the FasL/Fas pathway of NK cells, LAK cells, and CTLs, as investigated by using perforin-knockout mice, in which the granule exocytosis pathway of NK cells does not function and only the FasL/Fas pathway remains functional. 3) OPs induce apoptosis of immune cells.

Glucocorticoid-induced alternative promoter usage for a novel 5' variant of granzyme A

Glucocorticoids exert diverse physiological functions through transcriptional regulation of genes including granzyme A (GZMA). GZMA is one of the apoptotic effectors localized in cytotoxic T lymphocytes and is considered to mediate glucocorticoid-induced apoptosis of human leukemia 697 cells. In the present study, we identified a novel 5' variant transcript of GZMA in dexamethasone (DEX)-treated 697 cells. We designated this novel transcript as GZMAbeta. The transcription of GZMAbeta starts at 290 bp downstream of the first intronic glucocorticoid response element (GRE). Chromatin immunoprecipitation assay showed that glucocorticoid receptor (GR) binds to the intronic GRE in a DEX-dependent manner. Luciferase assay and RT-PCR also showed that DEX induces GZMAbeta transcription mediated by GR binding to the intronic GRE. Our results show that there exist at least two transcripts in human GZMA, whose expression is differentially regulated by glucocorticoid.

Dibutyltin exposure decreases granzyme B and perforin in human natural killer cells

Natural killer (NK) cells are a subset of lymphocytes that are capable of killing tumor and virally-infected cells. Dibutyltin (DBT) is a catalyst in the production of PVC plastics and a breakdown product of tributyltin (TBT). DBT is a significant environmental contaminant. This study investigates the mechanism by which DBT exposure decreases the immune function of human NK cells. NK cells destroy their target cells by releasing cytotoxic proteins, perforin, and granzyme B. We examined the effect of DBT exposures on the levels of cytotoxic proteins and their mRNAs. Exposure of NK cells to DBT for 1h caused significant decreases in the mRNAs for granzyme B and perforin but not in protein levels. A 24h exposure to DBT decreased mRNAs as well as protein levels for both granzyme B and perforin. Exposure to DBT for 1h followed by either a 24 or 48h period in DBT-free media, decreased levels of granzyme B and perforin. The results indicate that decreases in granzyme B and perforin levels in NK cells are consequences of DBT exposure. Additionally, DBT causes rapid decreases in mRNAs for perforin and granzyme B, suggesting decreases in transcription and/or increases in mRNA degradation.

Dimethyl 2,2-dichlorovinyl phosphate (DDVP) markedly decreases the expression of perforin, granzyme A and granulysin in human NK-92CI cell line

Natural killer (NK), lymphokine-activated killer (LAK) and cytotoxic T lymphocyte (CTL) cells kill target cells by the directed release of cytolytic granules that contain perforin, granzymes and granulysin. We previously have found that dimethyl 2,2-dichlorovinyl phosphate (DDVP), an organophosphorus pesticide significantly inhibited NK, LAK and CTL activities via the inhibition of granzyme activity. To further explore the mechanism of organophosphorus pesticide-induced inhibition of cell-mediated cytolysis, we asked here whether organophosphorus pesticides affect the expression of perforin, granzyme and granulysin in NK cells. We used NK-92CI cell, an interleukin-2 (IL-2) independent human NK cell line. We confirmed that NK-92CI cells express CD56 surface marker, perforin, granzyme A and granulysin by flow cytometry and immunofluorescence microscope, and that it is highly cytotoxic to K562 cells in chromium release assay. We found that DDVP significantly decreases the expression of perforin, granzyme A and granulysin in NK-92CI cells in a dose-dependent manner. Immunocytochemical results showed that DDVP significantly decreases perforin, granzyme A and granulysin positive granules in NK-92CI cell, which may be due to the degranulation. We also found that DDVP have a modest, but a significant inhibitory effect on the transcription of mRNA of perforin, granzyme A and granulysin.

Effects of interleukins 2 and 12 on the levels of granzyme B and perforin and their mRNAs in tributyltin-exposed human natural killer cells

Natural killer (NK) cells are a subset of lymphocytes that are capable of killing tumor cells, virally infected cells and antibody coated cells. Tributyltin (TBT) is a toxic chemical used for various industrial purposes such as: slime control in paper mills, disinfection of circulating industrial cooling waters, anti-fouling agents, and the preservation of wood. TBT can be found in edible items such as fish. A previous study showed that a 1 h exposure of NK cells to TBT caused persistent inhibition of NK-cell ability to destroy tumor cells in the 24 and 48 h periods following exposure and that this loss of function could be significantly prevented and/or reversed if the NK-stimulatory interleukins (IL) 2 or 12 were present during the 24 and 48 h periods. We had also shown that TBT exposure was able to significantly decrease the protein and mRNA levels of the cytotoxic proteins, granzyme B and perforin, and the phosphorylation of cAMP-response-element-binding protein (CREB) under these conditions. In this study we address the effects of IL-2 and IL-12 on the TBT-induced decreases in NK-cell levels of the cytotoxic proteins, their mRNAs, and CREB phosphorylation. IL-2 appeared to prevent/reverse TBT-induced declines in perforin protein levels and the mRNA for perforin seen in the 24 h period following a 1 h exposure to 300 nM TBT. However, the TBT-induced decreases in the levels of perforin and perforin mRNA seen in the 48 h period following a 1 h exposure to TBT were not statistically significantly prevented/reversed by IL-2. Additionally, the TBT-induced decreases in granzyme B, granzyme B mRNA, and CREB phosphorylation were not statistically significantly reversed by either IL-2 or IL-12 after 24 or 48 h.

Tributyltin exposure causes decreased granzyme B and perforin levels in human natural killer cells

Natural Killer (NK) cells are a subset of lymphocytes that are capable of killing tumor cells, virally infected cells and antibody coated cells. Tributyltin (TBT) is a toxic chemical used for various industrial purposes such as: slime control in paper mills, disinfection of circulating industrial cooling waters, anti-fouling agents in shower curtains and the preservation of wood. TBT can be found in edible items such as dairy products and fish. This study investigates the mechanism by which TBT exposure decreases the immune function of human NK cells, in vitro. Cytotoxic function, the expression of the cytotoxic proteins (granzyme B and perforin), and cAMP response element binding protein (CREB) phosphorylation were examined. NK cells exposed to 300 nM TBT for 1 h showed no significant decrease in cytotoxic function, levels of granzyme B and perforin, or phosphorylation of CREB. However, mRNA levels for the cytotoxic proteins were significantly decreased. A 24 h exposure to 200 nM TBT caused significant decreases in cytotoxic function, levels of granzyme B and perforin, and levels of granzyme B and perforin mRNA. When NK cells were exposed to 300 nM TBT for 1h followed by a 24 h period in TBT-free media, again there were significant decreases in NK cell cytotoxic function, levels of granzyme B and perforin and their mRNA. A 1h exposure to 300 nM TBT followed by a 48 h period in TBT-free media showed similar changes in cytotoxic function and levels of granzyme B and perforin as seen after 24 h in TBT-free media. Additionally, both of these exposures showed significant decreases in phosphorylation of CREB. These results indicate that TBT exposures can disrupt the transcription of granzyme B and perforin and that this disruption cannot be entirely accounted for by a decrease in phosphorylated CREB (phosphoCREB) levels.

Characterization of a trypsin-like serine protease of activated B cells mediating the cleavage of surface proteins

Activated B cells may cleave their surface receptors due to the proteolytic activity on the cell membrane or in its vicinity. We attempted to isolate and characterize the protease(s) responsible for this cleavage. Zymograms prepared from the supernatant and the plasma membrane fraction of activated human B cells and BL41/95 cell line exhibited a 85-90 kDa doublet band with protease activity, while that of resting B cells did not. Soybean trypsin inhibitor (STI), Nalpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) and EDTA treatment abolished the activity of this protease. The excess of Zn(2+) ions in EDTA did not restore the enzymatic activity, while it was completely recovered in the presence of Ca(2+). We affinity-purified a 85-90 kDa protease from the supernatant of BL41/95 cells using STI coupled to Sepharose 4B beads, and measured its kinetic parameters. For the arginyl substrate K(M) was 358+/-59 microM and for the lysyl substrate 582+/-103 microM. TLCK and benzamidine inhibited the protease at micromolar, while STI at nanomolar concentrations. Both the inhibition profile and the substrate specificity suggest that it is a trypsin-like serine protease. We assume that the 85-90 kDa serine protease expressed on and secreted by activated B cells and BL41/95 cell line is responsible for the cleavage of various membrane proteins, including Fcgamma receptors; thus it may play a crucial role in regulating B cell's function.

The orphan granzymes of humans and mice

The granzyme/perforin pathway is a central pathway for lymphocyte-mediated killing in both the innate and adaptive immune systems. This pathway is important in a variety of host defenses, including viral clearance and tumor cell killing, and its dysregulation results in several human and rodent diseases. To date, the majority of reports in this field have concentrated on the functions of granzymes A and B. Recent reports, however, suggest that the non-A/non-B 'orphan' granzymes found in both humans and mice are potentially significant. Although the functions of these orphan granzymes have yet to be fully established, initial data suggests their importance in both immune and nonimmune cells.

Crystal structure of the apoptosis-inducing human granzyme A dimer

Granzyme A (GzmA) belongs to a family of trypsin-like serine proteases localized in cytoplasmic granules of activated lymphocytes and natural killer (NK) cells. In contrast to the related granzyme B (GzmB), GzmA forms a stable disulfide-linked homodimer and triggers target-cell death in a caspase-independent way. Limited proteolysis of a high-molecular-mass complex containing SET (also named putative HLA-associated protein II or PHAPII), PHAPI (pp32, leucine-rich acidic nuclear protein) and HMG2 by GzmA liberates NM23-H1, a Mg2+-dependent DNase that causes single-stranded breaks in nuclear DNA. By analyzing the dimeric GzmA structure at a resolution of 2.5 A, we determined the substrate-binding constraints and selective advantages of the two domains arranged as a unique functional tandem. The active sites of the two subunits point in opposite directions and the nearby noncatalytic surfaces can function as exosites, presenting substrates to the active site region of the adjacent partner in a manner analogous to staphylokinase or streptokinase, which present plasminogen to the cofactor-plasmin and cofactor-plasminogen complexes.

Dipeptidyl peptidase I: importance of progranzyme activation sequences, other dipeptide sequences, and the N-terminal amino group of synthetic substrates for enzyme activity

The broadly reactive cysteine protease dipeptidyl peptidase I (DPPI, cathepsin C) is thought to activate all progranzymes (zymogens of lymphocyte serine proteases) to form mature granzymes. We synthesized dipeptide 7-amino-4-methylcoumarin (AMC) substrates containing progranzyme activation sequences and showed that they were efficiently hydrolyzed by DPPI. However, DPPI will not hydrolyze Ile-Ile-AMC, the N-terminal dipeptide sequence found in mature granzymes. Introduction of the nonphysiological homophenylalanine (Hph) residue at P1 resulted in the best substrate Ala-Hph-AMC for DPPI (k(cat)/K(m)=9,000,000M(-1)s(-1)). The charged N-terminal amino group of the substrate was essential and replacement of the NH(2) group with OH or NH(CH(3)) in Gly-Phe-AMC reduced the k(cat)/K(m) value by two to three orders of magnitude. A hydrazide azaglycine analog, NH(2)NHCO-Phe-AMC, was not hydrolyzed at pH 5.5, but underwent slow hydrolysis at lower pHs where the amino group is partially protonated. DPPI also failed to hydrolyze NH(2)COCH(2)-Phe-AMC, where the NH(2) group is unprotonated. The results reported in this paper should be useful in the design of better DPPI inhibitors to block granzyme maturation and granzyme-dependent apoptosis.

Cloning and structural analysis of leydin, a novel human serine protease expressed by the Leydig cells of the testis

We present the cloning and structural analysis of a novel member of the large family of trypsin-related serine proteases. Northern blot analysis shows that this protease, in adult tissues, is expressed almost exclusively in the human testis. In addition, a larger transcript was detected in relatively high abundance in several embryonic tissues, indicating different functions during embryonic and adult life. Sera raised against this protease was used to locate the expression in adult tissues to the testosterone producing cells of the testis, the interstitial Leydig cells. We therefore propose the name leydin for this novel protease. Leydin is clearly distinct from acrosin, the other testis-specific serine protease which is expressed by the spermatocytes. Leydin is probably a two-chain protease such as acrosin, prostasin, and coagulation factor XI. The heavy chain consists of 246 amino acids, corresponding to a molecular mass of 27384 Da and a net charge of +10.76. The size of the light chain is between 9 and 18 amino acids depending on the site of proteolytic cleavage, which remains to be determined. The amino-acid residues surrounding the active site indicate a trypsin-like cleavage specificity. The presence of two dibasic sequences Arg-Arg and Lys-Arg at the N-terminus of the heavy chain indicate that one or more subtilisin-like endopeptidases are responsible for the processing of leydin. However, leydin may also be activated by a trypsin-like enzyme, possibly by auto catalysis.

Activation of human monocytes induces differential resistance to apoptosis with rapid down regulation of caspase-8/FLICE

Cells of the monocyte/macrophage lineage play a central role in both innate and acquired immunity of the host. However, the acquisition of functional competence and the ability to respond to a variety of activating or modulating signals require maturation and differentiation of circulating monocytes and entail alterations in both biochemical and phenotypic profiles of the cells. The process of activation also confers survival signals essential for the functional integrity of monocytes enabling the cells to remain viable in microenvironments of immune or inflammatory lesions that are rich in cytotoxic inflammatory mediators and reactive free-radical species. However, the molecular mechanisms of activation-induced survival signals in monocytes remain obscure. To define the mechanistic basis of activation-induced resistance to apoptosis in human monocytes at the molecular level, we evaluated the modulation of expression profiles of genes associated with the cellular apoptotic pathways upon activation and demonstrate the following: (i) activation results in selective resistance to apoptosis particularly to that induced by signaling via death receptors and DNA damage; (ii) concurrent with activation, the most apical protease in the death receptor pathway, caspase-8/FLICE is rapidly down-regulated at the mRNA level representing a novel regulatory mechanism; and (iii) activation of monocytes also leads to dramatic induction of the Bfl-1 gene, an anti apoptotic member of the Bcl-2 family. Our findings thus provide a potential mechanistic basis for the activation-induced resistance to apoptosis in human monocytes.

Molecular Mechanisms of Immune-Mediated Lysis of Murine Renal Cancer: Differential Contributions of Perforin-Dependent Versus Fas-Mediated Pathways in Lysis by NK and T Cells

Mice bearing the experimental murine renal cancer Renca can be successfully treated with some forms of immunotherapy. In the present study, we have investigated the molecular pathways used by NK and T cells to lyse Renca cells. Renca cells normally express low levels of Fas that can be substantially enhanced by either IFN-γ or TNF-α, and the combination of IFN-γ + TNF-α synergistically enhances cell-surface Fas expression. In addition, cells pretreated with IFN-γ and TNF-α are sensitive to lysis mediated by Fas ligand (FasL)-expressing hybridomas (dllS), cross-linking of anti-Fas Abs or soluble Fas (FasL). Lysis via Fas occurs by apoptosis, since Renca shows all the typical characteristics of apoptosis. No changes in levels of bcl-2 were observed after cytokine treatments. We also examined cell-mediated cytotoxic effects using activated NK cells and T cells from gld FasL-deficient mice, and perforin-deficient mice, as well as wild-type C57BL/6 and BALB/c mice. Interestingly, the granule-mediated pathway predominated in killing of Renca by activated NK cells, while the Fas/FasL pathway contributed significantly to cell-mediated killing of Renca by activated T cells. These results suggest that killing of Renca tumor cells by immune effector cells can occur by both granule and Fas-mediated cytotoxicity. However, for the Fas-mediated pathway to function, cell surface levels of Fas need to be increased beyond a critical threshold level by proinflammatory cytokines such as IFN-γ and TNF-α.

Cloning of the gene and cDNA for hamster chymase 2, and expression of chymase 1, chymase 2 and angiotensin-converting enzyme in the terminal stage of cardiomyopathic hearts

Chymase is responsible for the formation of angiotensin II, which plays crucial roles in the pathogenesis of cardiovascular diseases. In the present study we determined the gene organization of a novel hamster chymase (hamster chymase 2) and analysed the expression of chymase 1, chymase 2 and angiotensin-converting enzyme (ACE) in hamster hearts at the terminal stage of cardiomyopathy. The gene encoding hamster chymase 2 is 3.2 kb in length and has five exons and four intervening sequences. The overall organization of this gene is similar to that of several other serine proteases. The deduced amino acid sequence revealed the existence of a preproenzyme composed of a signal peptide with 19 amino acids, a propeptide with two amino acids and a catalytic domain with 226 amino acids. The predicted full sequence of the catalytic domain was revealed to be very similar to the sequences of mouse mast-cell protease 5 (86%), rat mast-cell protease III (85%) and human chymase (70%) and less similar to hamster chymase 1 (56%). The expression of chymase 1 in heart was higher than that of chymase 2. The cardiac chymase-like activity, as well as the mRNA levels of chymase 1 and 2 of BIO 14.6 cardiomyopathic hamsters at the age of 60 weeks were increased 3.4-, 2.8- and 5.1-fold respectively compared with age-matched BIO F1B control hamsters. The cardiac ACE activity and the ACE mRNA level of cardiomyopathic hamsters were also increased 4.1- and 2.4-fold compared with those of age-matched controls. These results suggest that up-regulation of both ACE and chymases participates in the pathophysiology of the terminal stage of cardiomyopathy.

Synthesis and evaluation of diphenyl phosphonate esters as inhibitors of the trypsin-like granzymes A and K and mast cell tryptase

Thirty-six new amino acid and peptidyl diphenyl phosphonate esters were synthesized and evaluated to identify potent and selective inhibitors for four trypsin-like proteases: lymphocyte granzymes A and K, human mast cell tryptase, and pancreatic trypsin. Among five Cbz derivatives of Lys and Arg homologues, Z-(4-AmPhe)P(OPh)2 is the most potent inhibitor for granzyme A, and Z-LysP(OPh)2 is the best inhibitor for granzyme K, mast tryptase, and trypsin. The amidino P1 residue D,L-(4-AmPhGly)P(OPh)2 was utilized in a series of compounds with several different N-protecting groups and systematic substitutions at P2 in Cbz-AA derivatives and at P3 in Cbz-AA-Ala derivatives. Generally, these phosphonates inhibit granzyme A and trypsin more potently than granzyme K and tryptase. The P2 Thr and Ala dipeptide phosphonates, Cbz-AA-(4-AmPhGly)P(OPh)2, are the most potent inhibitors for granzyme A, and Cbz-Thr-(4-AmPhGly)P(OPh)2 (kobs/[I] = 2220 M-1 s-1) was quite specific with much lower inhibition rates for granzyme K and trypsin (kobs/[I] = 3 and 97 M-1 s-1, respectively) and no inhibition with tryptase. The most effective inhibitor of granzyme A was Ph-SO2-Gly-Pro-(4-AmPhGly)P(OPh)2 with a second-order rate constant of 3650 M-1 s-1. The most potent inhibitor for granzyme K was 3, 3-diphenylpropanoyl-Pro-(4-AmPhGly)P(OPh)2 with a kobs/[I] = 1830 M-1 s-1; all other phosphonates inhibited granzyme K weakly (kobs/[I] < 60 M-1 s-1). Human mast cell tryptase was inhibited slowly by these phosphonates with Cbz-LysP(OPh)2 as the best inhibitor (kobs/[I] = 89 M-1 s-1). The overall results suggest that scaffolds of Phe-Thr-(4-AmPhe) and Phe-Pro-Lys will be useful to create selective phosphonate inhibitors for granzymes A and K, respectively, and that P4 substituents offer opportunities to further enhance selectivity and reactivity.

Dual mechanisms of apoptosis induction by cytotoxic lymphocytes

Cytotoxic T lymphocytes and natural killer cells together comprise the means by which the immune system detects and rids higher organisms of virus-infected or transformed cells. Although differing considerably in the way they detect foreign or mutated antigens, these cells utilize highly analogous mechanisms for inducing target cell death. Both types of effector lymphocytes utilize two principal contact-dependent cytolytic mechanisms. The first of these, the granule exocytosis mechanism, depends on the synergy of a calcium-dependent pore-forming protein, perforin, and a battery of proteases (granzymes), and it results in penetration by effector molecules into the target cell cytoplasm and nucleus. The second, which requires binding of FasL (CD95L) on the effector cell with trimeric Fas (CD95) molecules on receptive target cells, is calcium independent and functions by generating a death signal at the inner leaflet of the target cell membrane. Exciting recent developments have indicated that both cytolytic mechanisms impinge on an endogenous signaling pathway that is strongly conserved in species as diverse as helminths and humans and dictates the death or survival of all cells.

IFN-beta partially counteracts inhibition of natural killer activity induced by some antitumor agents

We investigated whether recombinant human (rHu-IFN-beta) (IFN-beta) could counteract the inhibition of natural killer (NK) activity caused by antitumor agents. Peripheral blood lymphocytes (PBL) were incubated with different antitumor agents alone or in combination with IFN-beta for 3 days and then tested in a cytotoxicity assay against the K562 cell line. The following drugs were used, all of which caused a dose-dependent inhibition of NK activity: etoposide, camptothecin, doxorubicin, cis-DDP, tallimustine, and L-PAM. Concomitant treatment with (1000 U/ml) IFN-beta counteracted the inhibitory effect of etoposide and camptothecin but had no consistent effect on the inhibition mediated by the other drugs. Mean values of inhibition of NK activity at 1 microM camptothecin was 48%+/-3.4% and with IFN-beta was 10%+/-4.9%. With 100 microM etoposide, mean value of inhibition was 78%+/-3.3%, and with IFN-beta, it was 18%+/-1.5%. Cell viability, assessed by vital dye exclusion, and drug uptake, assessed with radiolabeled etoposide, were similar in cells treated with or without IFN-beta. The protective effect of IFN-beta on NK function was rather selective, as IFN-beta did not counteract the drug-mediated inhibition of PBL proliferation when stimulated by phytohemagglutinin (PHA). Other cytokines, IFN-alpha, IFN-gamma, and interleukin-2 (IL-2), had similar protective effect, although IFN-beta, was slightly more potent. On the other hand, IL-6, a cytokine sharing some properties with IFNs was ineffective. Camptothecin inhibited the expression of mRNA for granzyme B, a lytic protein involved in lymphoid-mediated cytotoxicity. Combined treatment with IFN-beta restored-at least in part-the transcription of granzyme B mRNA. These results show that the immunosuppressive effect of some antitumor agents could be partly counteracted by treatment with IFN-beta.

Activated CD4+ and CD8+ cytotoxic cells are present in increased numbers in the intestinal mucosa from patients with active inflammatory bowel disease

The contribution of cell-mediated cytotoxicity to the pathogenesis of inflammatory bowel disease (IBD) is controversial, and results of in vitro assays vary according to experimental procedures. Therefore, we compared the frequency of cytotoxic effector cells in situ. On tissue sections of controls (n = 11), low frequencies of granzyme A and perforin mRNA-expressing cells are found in the lamina propria (1.77 +/- 0.15% and 1.46 +/- 0.12%, respectively) and in the epithelial cell layer (0.76 +/- 0.12% and 0.66 +/- 0.10%, respectively). In patients with IBD (n = 33), corresponding values were significantly (P < 0.02) higher, 6.1 +/- 0.40% and 5.92 +/- 0.57% for granzyme A and perforin expression in the lamina propria and 2.50 +/- 0.19% and 2.59 +/- 0.28%, respectively, in the epithelial compartment. Differences between ulcerative colitis and Crohn's disease are statistically not significant (P > 0.33). Activated cytotoxic cells are preferentially found at sites facing the intestinal lumen. Perforin mRNA-expressing cells are mainly CD8+ T cells. CD4+ T cells expressing perforin mRNA are mainly isolated from affected areas of patients with Crohn's disease. Immunostaining for perforin protein generally coincides with perforin mRNA in situ. These data demonstrate that cytotoxic cells are vigorously activated in situ in the intestinal mucosa of patients with active IBD.

Lysine 156 promotes the anomalous proenzyme activity of tPA: X-ray crystal structure of single-chain human tPA

Tissue type plasminogen activator (tPA) is the physiological initiator of fibrinolysis, activating plasminogen via highly specific proteolysis; plasmin then degrades fibrin with relatively broad specificity. Unlike other chymotrypsin family serine proteinases, tPA is proteolytically active in a single-chain form. This form is also preferred for therapeutic administration of tPA in cases of acute myocardial infarction. The proteolytic cleavage which activates most other chymotrypsin family serine proteinases increases the catalytic efficiency of tPA only 5- to 10-fold. The X-ray crystal structure of the catalytic domain of recombinant human single-chain tPA shows that Lys156 forms a salt bridge with Asp194, promoting an active conformation in the single-chain form. Comparisons with the structures of other serine proteinases that also possess Lys156, such as trypsin, factor Xa and human urokinase plasminogen activator (uPA), identify a set of secondary interactions which are required for Lys156 to fulfil this activating role. These findings help explain the anomalous single-chain activity of tPA and may suggest strategies for design of new therapeutic plasminogen activators.

Residual cytotoxicity and granzyme K expression in granzyme A-deficient cytotoxic lymphocytes

Cytotoxic lymphocytes contain granules that have the ability to induce apoptosis in susceptible target cells. The granule contents include perforin, a pore-forming molecule, and several granzymes, including A and B, which are the most abundant serine proteases in these granules. Granzyme B-deficient cytotoxic T lymphocytes (CTL) have a severe defect in their ability to rapidly induce apoptosis in their targets, but have an intact late cytotoxicity pathway that is in part perforin-dependent. In this report, we have created mice that are deficient for granzyme A and characterized their phenotype. These mice have normal growth and development and normal lymphocyte development, activation, and proliferation. Granzyme A-deficient CTL have a small but reproducible defect in their ability to induce 51Cr and 125I-UdR release from susceptible allogeneic target cells. Since other granzyme A-like tryptases could potentially account for the residual cytotoxicity in granzyme A-deficient CTL, we cloned the murine granzyme K gene, which is linked to granzyme A in humans, and proved that it is also tightly linked with murine granzyme A. The murine granzyme K gene (which encodes a tryptase similar to granzyme A) is expressed at much lower levels than granzyme A in CTL and LAK cells, but its expression is unaltered in granzyme A-/- mice. The minimal cytotoxic defect in granzyme A-/- CTL could be due to the existence of an intact, functional early killing pathway (granzyme B dependent), or to the persistent expression of additional granzyme tryptases like granzyme K.

Sheep mast cell proteinase-1: characterization as a member of a new class of dual-specific ruminant chymases

Sheep mast cell proteinase 1 (SMCP-1), which is abundantly expressed in gastrointestinal but not skin mast cells, was isolated and its substrate specificity was investigated. Peptide substrates, including angiotensin I, substance P, bradykinin and oxidized insulin B chain were hydrolysed at P1 Phe, Leu or Tyr residues, conforming to the known chymotrypsin-like properties of the enzyme. However, SMCP-1 was found to hydrolyse some chromogenic substrates with P1 Lys and Arg residues. The enzyme also demonstrated trypsin-like activity against protein substrates, cleaving BSA at Lys114-Leu115, Lys238-Val239, Lys260-Tyr261 and Lys376-His377. Bovine fibrinogen beta-chain was cleaved at Lys28-Lys29. To ensure homogeneity of the enzyme, the ratio of chymotrypsin-like to trypsin-like activity was observed; it was found to be constant during purification and between different preparations of SMCP-1. Treatment of SMCP-1 with a range of inhibitors decreased chymotrypsin-like and trypsin-like activities by similar extents, supporting the assertion that both activities are the property of a single enzyme. In terms of activity, and by N-terminal amino acid sequencing, SMCP-1 strongly resembles the similarly dual-specific bovine duodenal proteinase, duodenase. It is proposed that SMCP-1 and duodenase represent a new class of ruminant chymases with unusual dual specificities.

Secretory granule proteases in rat mast cells. Cloning of 10 different serine proteases and a carboxypeptidase A from various rat mast cell populations

Two of the major rat mast cell proteases, rat mast cell protease 1 (RMCP-1) and RMCP-2, have for many years served as important phenotypic markers for studies of various aspects of mast cell (MC) biology. However, except for these proteases only fragmentary information has been available on the structure and complexity of proteases expressed by different subpopulations of rat MCs. To address these questions, cDNA libraries were constructed from freshly isolated rat peritoneal MCs and from the rat mucosal MC line RBL-1. cDNA clones for 10 different serine proteases (RMCP-1-10), and the MC carboxypeptidase A were isolated and characterized. Six of these proteases have not been isolated previously. Based on their protease content, three separate subpopulations of MCs were identified. Connective tissue MCs (CTMCs) from the ear and peritoneum express the chymases RMCP-1 and -5, the tryptases RMCP-6, and -7 and the carboxypeptidase A. However, based on a large difference in the level of expression of RMCP-7, CTMCs of these two organs may be regarded as two separate subpopulations. RMCP-2 and the three closely related proteases of the RMCP-8 subfamily were identified as the major mucosal MC proteases in rat. In contrast to what has been reported for human MCs, no expression of cathepsin G or cathepsin G-like proteases was detected in any of the rat MC populations. To determine mRNA frequencies for the various proteases expressed by normal tissue MCs, an unamplified peritoneal MC cDNA library was screened with a panel of mono-specific cDNA probes. These results showed that peritoneal MCs are highly specialized effector cells with mRNA frequencies for the major proteases in the range of several percent of the total mRNA pool.

Anti-CD3-activated killer T cells: interferon-gamma and interleukin-10 cross-regulate granzyme B expression and the induction of major histocompatibility complex-unrestricted cytotoxicity

We have investigated the effect of interferon-gamma (IFN-gamma) and interleukin (IL)-10 on granzyme B expression and the induction of major histocompatibility complex (MHC)-unrestricted cytotoxic activity in mouse T cell cultures following activation with anti-CD3 monoclonal antibody (mAb). First, metabolic inhibitors of granule-dependent and granule-independent cytolytic pathways were used to show that anti-CD3-activated killer T (AK-T) cells kill allogeneic P815 mastocytoma target cells primarily by the granule-dependent granzyme/perforin pathway. In comparison to control AK-T cells, lower levels of cytolytic activity were evident when AK-T cells were generated in the presence of anti-IFN-gamma neutralizing mAb or exogenous IL-10, whereas enhanced cytotoxicity was observed when AK-T cell cultures contained anti-IL-10 neutralizing mAb or exogenous IFN-gamma. In addition, granzyme B mRNA expression by AK-T cells was diminished when IFN-gamma bioactivity was neutralized or exogenous IL-10 was present in AK-T cell-cultures, whereas neutralization of IL-10 bioactivity or the addition of exogenous IFN-gamma resulted in increased expression of granzyme B mRNA. Similar results were obtained when granzyme B enzymatic activity in AK-T cell lysates was quantified using a colorimetric granzyme B assay. Altered cytotoxic potential, granzyme B mRNA expression, and granzyme B enzymatic activity following T cell activation in the presence of anti-IFN-gamma or anti-IL-10 neutralizing mAb or exogenous IFN-gamma or IL-10 could not be attributed to gross changes in T cell activation status or to altered percentages of CD4+ and CD8+ T cells in AK-T cell cultures. We conclude that IFN-gamma and IL-10 cross-regulate the induction of the granule-dependent cytolytic machinery of AK-T cells.

Expression of human recombinant granzyme A zymogen and its activation by the cysteine proteinase cathepsin C

Human granzyme A is one of the serine proteinases present in the granules of cytotoxic T lymphocytes and natural killer cells. Granzymes are synthesized as inactive proenzymes with an amino-terminal prodipeptide, which is processed during transport of granzymes to the cytotoxic granules, where they are stored as active proteinases. In this study, we explored the possibility of producing recombinant granzymes. Recombinant human granzyme A zymogen was expressed in several eukaryotic cell lines (HepG2, Jurkat, and COS-1) after infection with a recombinant vaccinia virus containing full-length granzyme A cDNA. Immunoblot analysis of cell lysates showed that all infected cells produced a disulfide-linked homodimer of identical molecular weight as natural granzyme A. Infected HepG2 cells produced the largest amount of this protease (approximately 160 times more than lymphokine activated killer (LAK) cells). The recombinant protein only had high mannose type oligosaccharides as did the natural protein. Although infected HepG2 and COS cells contained high granzyme A antigen levels, lysates from these cells did not show any granzyme A proteolytic activity. However, the inactive proenzyme could be converted into active granzyme A by incubation with the thiol proteinase cathepsin C (dipeptidyl peptidase I). This study is the first to demonstrate expression of an active recombinant human cytotoxic lymphocyte proteinase and conversion of inactive progranzyme A into an active enzyme by cathepsin C. We suggest that a similar approach can be used for the production of other granzymes and related proteinases.

Specific inhibition of granzyme B by parainfluenza virus type 3

T-cell-mediated cytotoxicity is an important means of defense against viral pathogens; however, several viruses possess mechanisms to disrupt cytotoxicity, thereby allowing them to avoid immune clearance. These viruses have been shown to inhibit cytotoxicity by interfering with the capacity of T lymphocytes to specifically recognize infected cells. An alternative mechanism for virally induced cytotoxic dysfunction is identified in this report. We show that parainfluenza virus type 3, a negative-stranded RNA virus, can inhibit cytotoxicity by causing a defect in the cytotoxic effector apparatus. This defect is identified as a selective inhibition of granzyme B mRNA.

Localization and identification of granzymes A and B-expressing cells in normal human lymphoid tissue and peripheral blood

Cytoplasmic granules from activated natural killer (NK) and cytotoxic T lymphocytes (CTL) contain a pore-forming protein, perforin, and several homologous serine proteinases called granzymes. Expression of these proteins correlates with the cytolytic potential of cytotoxic lymphocytes. Using a panel of MoAbs specific for human granzyme A and B, respectively, expression of these proteinases in non-pathological lymphoid tissue and peripheral blood lymphocyte (PBL) subpopulations was investigated. Using immunohistochemistry and double stainings, the phenotype of granzyme-expressing cells in lymphoid tissue was investigated. Granzyme-positive cells were detected in all lymphoid tissues tested. No large differences in the number and distribution between granzyme A- and granzyme B-positive cells were observed. The highest number of positive cells was located in the red pulp of the spleen. Significant numbers were detected in tonsil, lymph nodes, liver and thymus. Low numbers were present in the lamina propria of non-inflamed stomach, small intestine and colon. Phenotypic analysis and cell sorting showed that most of the granzyme-positive cells in lymphoid tissue and PBL consisted of CD3-CD16+CD56+ lymphocytes. Hardly any granzyme-positive CD3+CD8+ CTL were present in peripheral blood. The synthesis of granzyme A as well as B by both CD3+CD16+CD56+ and CD3+CD8+ cells in peripheral blood was increased upon IL-2 stimulation. These results indicate that in normal lymphoid tissue the predominant cytolytic cell population is formed by the NK cells, and activated CTL are rare.

Effects of lethal irradiation and cyclosporin A treatment on the growth and tumoricidal activity of a T cell clone potentially useful in cancer therapy

The TALL-104 cell line, originally derived from a patient with T cell leukemia, can be maintained indefinitely in culture in the presence of interleukin-2 (IL-2) and is endowed with a highly potent major-histocompatibility-complex (MHC)-non-restricted tumoricidal activity both in vitro and in animal models. The present study analyzes in detail the short- and long-term effects of irradiation and cyclosporin A (CsA) treatment on the growth and tumoricidal function of this T cell clone as compared to polyclonal lymphokine-activated killer (LAK) cell preparations from healthy donors. DNA and RNA syntheses by both TALL-104 and LAK cells were irreversibly arrested a few hours after irradiation with 40 Gy. However, 4-h 51Cr-release assays, performed on different days (day 1 to day 7) after irradiation, showed that the cytotoxic efficiency of TALL-104 cells against hematopoietic and solid tumor targets was only modestly reduced, whereas that of LAK cells was severely inhibited. Moreover, the cytotoxic responses to recombinant human IL-2 and IL-12, measured 18 h after irradiation and cytokine addition, were normal in the case of TALL-104 cells but were abolished in the case of LAK cells. Co-culture of IL-2- or IL-12-preactivated TALL-104 cells with a tumor target for 5 days in the absence of cytokines resulted in a lower efficiency of lysis, as compared to the non-irradiated effectors, especially if the initial stimulus was IL-12. These findings suggest the requirement of multiple cytokine stimulation for optimal expression of tumoricidal activity by lethally irradiated TALL-104 cells. CsA, while abrogating TALL-104 cell proliferation at the low dose of 0.5 microgram/ml, inhibited their cytotoxic function marginally only at high doses (100 micrograms/ml). By contrast, CsA reduced dose-dependently the cytotoxicity of LAK cells starting at very low doses (0.5 microgram/ml). CsA did not impair the ability of TALL-104 and LAK cells to produce interferon (IFN) gamma, tumor necrosis factor (TNF) alpha, and granulocyte/macrophage-colony-stimulatory factor (GM-CSF) in response to IL-2, IL-12, or tumor targets. Irradiation reduced drastically IFN gamma production by LAK, but not TALL-104 cells; release of TNF alpha and GM-CSF by either type of effector was inhibited by 10%-50%, depending on the stimulus. The high resistance and immunosuppressive drugs renders tis immortal T cell clone a potentially safe and effective reagent for new adoptive-transfer approaches to cancer in MHC-incompatible recipients.

Synergistic roles of granzymes A and B in mediating target cell death by rat basophilic leukemia mast cell tumors also expressing cytolysin/perforin

We have studied the cytotoxic activity of rat basophilic leukemia (RBL) cells transfected with cDNAs for the cytotoxic T lymphocyte (CTL) granule components, cytolysin (perforin), granzyme A, and granzyme B. With red cell targets, cytolysin expression conferred potent hemolytic activity, which was not influenced by coexpression of granzymes. With tumor targets, RBL cells expressing cytolysin alone were weakly cytotoxic, but both cytolytic and nucleolytic activity were enhanced by coexpression of granzyme B. RBL cells expressing all three CTL granule components showed still higher cytotoxic activities, with apoptotic target death. Analysis of the cytotoxic activity of individual transfectant clones showed that cytolytic and nucleolytic activity correlated with granzyme expression but was independent of cytolysin expression within the range examined. A synergism between granzymes A and B was apparent when the triple transfectant was compared with RBL cells expressing cytolysin and one granzyme. These data implicate granzymes as the major mediators of tumor target damage by cytotoxic lymphocytes.

Expression of granzyme A and B proteins by cytotoxic lymphocytes involved in acute renal allograft rejection

Granzymes A and B are serine-proteinases stored in the granules of activated cytotoxic T-lymphocytes and natural killer (NK) cells. Expression of granzymes in tissues can be used as an activation marker for cytotoxic cells. Using mAbs specific for human granzyme A or B in immunohistochemical staining techniques we investigated expression of granzyme A and B by lymphocytes infiltrating acutely rejected renal allografts. Twelve core needle biopsies were taken from ten different patients during an episode of acute rejection. Eleven biopsies contained high numbers of granzyme A and B positive lymphocytes infiltrating tubular epithelium, and vascular and glomerular structures. In one patient infiltrating lymphocytes did not express granzyme A and only low amounts of granzyme B. No correlation was found between the number of granzyme positive cells and the severity of the rejection as classified by conventional histological criteria. In one tissue specimen from a patient with a renal allograft without signs of rejection, the number of granzyme positive cells was much lower compared to that of the transplant group. In spite of the presence of a marked inflammatory infiltrate, no granzyme positive cells were detected in renal biopsies from patients with various inflammatory, not transplant-related, renal diseases. Phenotypic analysis showed that granzymes A and B were expressed by CD56+ NK cells and CD3+ cells, representing cytotoxic T-lymphocytes. Thus, this study demonstrates that granzyme A and B protein-expressing lymphocytes infiltrate the kidney allografts during an acute cellular rejection but not in several other inflammatory renal diseases.(ABSTRACT TRUNCATED AT 250 WORDS)

Serine proteinases of mast cell and leukocyte granules. A league of their own

Serine proteinases are hydrolases that use serine's side chain hydroxyl group to attack and cleave internal peptide bonds in peptides and proteins. They reside in all mammalian tissues, including the lung and airway. As a group, they vary tremendously in form and target specificity and have a vast repertoire of functions, many of which are critical for life. A subset of these proteinases is expressed primarily in the cytosolic granules of leukocytes from bone marrow, including mast cells. Examples are elastase-related proteinases and cathepsin G of monocytes and neutrophils, the many "granzymes" of cytotoxic T lymphocytes and natural killer (NK) cells, and the tryptases and chymases of mast cells. The pace of discovery and characterization of these granule-associated serine proteinases, fueled by technical advances in molecular biology, has accelerated rapidly in the past few years. Progress has been made in assigning possible functions to individual proteinases. However, the burgeoning numbers of these enzymes; their cell, tissue and species-dependent differences in expression; and their variety of action in vitro (despite, in many cases, shared modes of activation and recent divergence in protein evolution) have vexed and challenged those of us who are anxious to establish their roles in mammalian biology. Certainly, much remains to be discovered and clarified. The purpose of this overview is to capture the state of the art in this field, stressing the similarities as well as the differences among individual granule-associated proteinases and focusing particularly on those enzymes likely to be important in the human lung and airways.

Genes for mast-cell serine protease and their molecular evolution

Trypsin-related serine proteases are encoded by a very large gene family in mammals. We describe here a comparative analysis of the genomic DNA sequences of mouse, rat, and human mast-cell-specific serine protease genes. Strong evidence was found for multiple exchanges of genetic information between closely related members of this gene family. The 5' regulatory regions of MMCP-1 and MMCP-L share a remarkably high degree of sequence identity (98%), starting 10 base pairs downstream of exon 1 and extending to the end of the presently sequenced region at position -1347 of the MMCP-1 gene. The remaining parts of the two genes share approximately 80% sequence identity. Evidence for at least two additional, but not so recent, exchanges was found in the 3' regions of the MMCP-4 and MMCP-L genes and in the 5' regions of the genes for MMCP-1 and MMCP-2. The 5' regulatory regions of all presently characterized mouse mast-cell-specific chymotrypsin-like serine protease genes exhibit over 88% sequence identity in the region from the transcription initiation site to approximately position -600. An exception is MMCP-5 which is the most distantly related member of this subfamily. The high degree of sequence similarities indicates a strong evolutionary homogenization of the 5' regulatory region, possibly by several gene conversion events. In addition, several insertions of genetic information have been identified in genes for mast-cell chymases and genes for T-cell granzymes. A number of these have been found to represent repetitive sequences, such as L1. The previously characterized tissue-specific enhancer element of the RMCP II gene was identified as a member of a middle repetitive sequence. A cDNA for a newly discovered pseudogene, closely related to the mouse mast cell chymases was isolated by polymerase chain reaction amplification from a mouse connective tissue-like mast cell line. The structure of this cDNA is presented. We also present the characterization of a novel spliced variant of MMCP-6 that contains an alternative 3' terminal exon (exon 6). The function of this variant, if any, is still unknown. A comparative analysis of amino acid sequence identities between different hematopoietic serine proteases shows that a high degree of sequence similarity does not always correlate with relateness in cleavage specificity. This indicates that the substrate specificity evolved with a higher evolutionary rate than the degree of overall amino acid sequence identity of these proteases.

Expression of granzyme A in salivary gland biopsies from patients with primary Sjögren's syndrome

OBJECTIVE

To determine whether the destruction of salivary gland epithelial cells in Sjögren's syndrome (SS) could be mediated by granzyme A, a serine protease that is contained in the granules of activated lymphocytes.

METHODS

We used in situ hybridization and polymerase chain reaction amplification to determine the expression of granzyme A messenger RNA (mRNA) in salivary gland biopsy samples.

RESULTS

Granzyme A mRNA expression was detected in salivary glands from SS patients, but not in those from normal controls. Granzyme A mRNA content was significantly correlated (P < 0.001) with the size of lymphocytic infiltrates in the salivary glands and with the clinical activity of the disease.

CONCLUSION

Cells that express granzyme A mRNA may play a role in the destruction of the target organ (i.e., the salivary gland) in patients with SS. The strong association of granzyme A mRNA expression and larger lymphoid infiltrates in the patients' salivary glands suggests that granzyme A mRNA is expressed at a relatively late stage of the local inflammatory process. Therapies designed to modulate or block granzyme A induction and action should be investigated in SS patients.

Phenotypic characterization of the human mast-cell line HMC-1

The cell line HMC-1, derived from a patient with mast cell leukaemia, is the only established cell line exhibiting a phenotype similar to that of human mast cells. This paper reports on a detailed characterization of the expression of a panel of markers for various types of immature and mature haematopoietic cells in the HMC-1. We also studied the potential of HMC-1 to differentiate upon treatment with conditioned media from the human T-cell line Mo, retinoic acid or DMSO. HMC-1 was found to express several mast cell-related markers. A high expression of Kit, the receptor for stem-cell factor, was detected. The majority of the cells were stained with a MoAb against the mast cell-specific serine protease tryptase. Of particular interest was the finding that beta-tryptase mRNA, but not alpha-tryptase mRNA, was expressed in HMC-1. Using enzyme-histochemistry we were able to show that the beta-tryptase was enzymatically active, indicating that tryptase can form active homotetramers. Both heparin and chondroitin sulfate were found to be present in approximately equal amounts. HMC-1 lacked surface expression of the high-affinity IgE receptor, which was confirmed by the absence of mRNA of the alpha- and beta-chains of the IgE-receptor complex. However, a strong expression of the gamma-chain of the IgE-receptor complex was detected. A positive staining of the monocyte/macrophage marker CD68 was obtained, as well as a strong hybridization signal for the eosinophilic/basophilic-related differentiation marker the Charcot-Leyden crystal. Treatment of HMC-1 with conditioned media from the human T-cell line Mo, retinoic acid or DMSO induced only moderate changes in the surface or intracellular expression of the studied markers. The agents tested neither induced any of the monocyte/granulocyte markers examined, nor expression of the Fc epsilon RI alpha-chain.

In situ cDNA polymerase chain reaction. A novel technique for detecting mRNA expression

We report a novel method for detecting intracellular messenger RNA by combining the techniques of in situ hybridization and polymerase chain reaction (PCR) (in situ cDNA PCR). The technique could detect low abundancy signals and distinguish different levels of gene expression. We examined the expression of the functional markers of activated cytotoxic T lymphocytes, granzyme A, and perforin in human lymphocytes from in vitro cultures. The amplification products were found in the cells and the supernatants, with the distribution critically affected by the protease digestion conditions. The specificity of amplification was confirmed by electrophoretic analysis and Southern blotting. We conclude that the in situ cDNA PCR technique offers a sensitive method of measuring the frequency of signal-expressing cells and has significant research and clinical applications.

A novel chymotrypsin-like serine proteinase from human lung

A novel chymotrypsin-like serine proteinase with an M(r) of 30,000 has been isolated from human lung tissue. The enzyme was active on both the synthetic substrate Suc-Ala-Ala-Pro-Phe-SBzl and azocasein, with a pH optimum of 8.0 and a preference for high concentrations of NaCl for maximum activity. The proteinase was inhibited by diisopropylfluorophosphate, tosyl-phenylalanyl-chloromethane, chymostatin, soybean trypsin inhibitor, alpha-1-antichymotrypsin, and alpha-2-macroglobulin. It was not inhibited by C-1 inhibitor or aprotinin. An N-terminal sequence of IIGGTESKPDSRPYMALLQIVEPAVH indicated that this enzyme is a member of a superfamily of serine proteinases comprising cathepsin G, chymase, and the granzymes; however, it is clearly distinct from these enzymes on the basis of both physical and chemical properties.

Separation and partial characterization of proteinases with substrate specificity for basic amino acids from human MOLT-4 T lymphocytes: identification of those inhibited by variable-loop-V3 peptides of HIV-1 (human immunodeficiency virus-1) envelope glycoprotein

The V3 loop of the HIV (human immunodeficiency virus)-1 envelope glycoprotein gp120 likely plays a role in HIV-1 infectivity. Although the amino acid sequence of the V3 loop is hypervariable, it contains a conserved region, Gly-Pro-Gly-Arg, that shows similarity to the active-site Gly-Pro-Cys-Arg sequence of inter-alpha-trypsin and trypstatin proteinase inhibitors. The purpose of the present work was to identify proteinases recognizing substrates with basic amino acids in the P1 substrate site that are present in MOLT-4 cells, a human CD4-positive T helper lymphocyte cell line, and to characterize these enzymes in terms of substrate, pH and ionic-strength preferences, size and susceptibility to various inhibitors, including 24- and 36-amino-acid-long V3 loop peptides. Extraction of MOLT-4 cells at low ionic strength solubilized nearly all of the trypsin-like activity, which was separable into five peaks of activity by chromatography on Mono-Q: Peaks 1, 2a, 2b, 3 and 4. All showed a neutral pH optimum, and all except Peak 4 showed optimal activity at high ionic strength. Peak 1 preferred Tos-Gly-Pro-Arg, p-nitroanilide (-pNA) substrate; Peaks 2-4 preferred benzyloxycarbonyl-Val-Leu-Gly-Arg-pNA. Peak 1, a zinc-dependent enzyme with serine and histidine in the active site, exhibited an M(r) of 75,000 on Superose 12 and was poorly inhibited by V3 loop peptides. Peak 2 contained two overlapping peaks, called 2a and 2b, that exhibited properties of zinc-dependent metalloproteinases. Gel filtration of Peak 2 activities revealed a major peak of activity at 81 kDa and a shoulder centred at 240 kDa. Each was modestly inhibited by V3 loop peptides. Peak 3, a zinc-dependent proteinase, exhibited a molecular mass of 100 kDa by gel filtration and was particularly sensitive to inhibition by V3 loop peptides. Peak 4 exhibited a molecular mass of 1100 kDa by gel filtration and was not inhibited by V3 loop peptides. None of these enzymes could be classified as mast-cell tryptase, and material in MOLT-4 cells cross-reactive with anti-(human tryptase) antibodies was not detected. Whether any of the MOLT-4 proteinases described in this study play a role in HIV-1 infectivity remains to be examined.

The assembly of H2-Kb class I molecules translated in vitro requires oxidized glutathione and peptide

Association of the mouse major histocompatibility complex (MHC) class I heavy chain H2-Kb with mouse beta 2-microglobulin (beta 2m) was studied in an in vitro translation system. Formation of stable class I complexes was found to be dependent on the presence of presentable peptides and oxidized glutathione, which promotes the formation of disulfide bridges. Translocation of peptides into microsomes was demonstrated by showing that a radioiodinated peptide containing an N-glycosylation acceptor site became glycosylated. Class I complex formation was observed only when heavy chains and beta 2m were translated simultaneously, and thus occurs in the microsomes and not after their solubilization. However, peptide binding takes place only after solubilization of the microsomes. The class I complexes translated in vitro show the same specificity and length preference for peptides as their counterparts in RMA-S cells. Assembly of in vitro translated class I complexes was found to occur also in the absence of peptides, resulting in the formation of unstable molecules that are stabilized by incubation with peptides.

Granzymes A and B are targeted to the lytic granules of lymphocytes by the mannose-6-phosphate receptor

To investigate the question of whether lytic granules share a common biogenesis with lysosomes, cloned cytolytic T cell lines were derived from a patient with I-cell disease. The targeting of two soluble lytic granule components, granzymes A and B, was studied in these cells which lack a functional mannose-6-phosphate (Man-6-P) receptor-mediated pathway to lysosomes. Using antibodies and enzymatic substrates to detect the lytic proteins, I-cells were found to constitutively secrete granzymes A and B in contrast to normal cells in which these proteins were stored for regulated secretion. These results suggest that granzymes A and B are normally targeted to the lytic granules of activated lymphocytes by the Man-6-P receptor. In normal cells, the granzymes bear Man-6-P residues, since the oligosaccharide side chains of granzymes A and B, as well as radioactive phosphate on granzyme A from labeled cells, were removed by endoglycosidase H (Endo H). However, in I-cells, granzymes cannot bear Man-6-P and granzyme B acquires complex glycans, becoming Endo H resistant. Although the levels of granzymes A and B in cytolytic I-cell lymphocytes are < 30% of the normal levels, immunolocalization and cell fractionation of granzyme A demonstrated that this reduced amount is correctly localized in the lytic granules. Therefore, a Man-6-P receptor-independent pathway to the lytic granules must also exist. Cathepsin B colocalizes with granzyme A in both normal and I-cells indicating that lysosomal proteins can also use the Man-6-P receptor-independent pathway in these cells. The complete overlap of these lysosomal and lytic markers implies that the lytic granules perform both lysosomal and secretory roles in cytolytic lymphocytes. The secretory role of lytic granules formed by the Man-6-P receptor-independent pathway is intact as assessed by the ability of I-cell lymphocytes to lyse target cells by regulated secretion.