Granzyme b delivery mechanism into the target cell cytoplasm 6. Despite recent advances outlining the mechanisms of action of granzyme b within the target cell, there are still numerous conflicting reports regarding the requirements and dependence of granzyme b mediated apoptosis on caspases and the potential for inhibition by the antiapoptotic protooncogene, bcl2. In particular, it directly cleaves, and activates, several effector and initiator procaspases. The perforin mediated apoptotic pathway in lung injury and fibrosis article pdf available in journal of clinical pathology 5712. Mouse cytotoxic t cellderived granzyme b activates the. Granzyme bmediated apoptosis proceeds predominantly. Multiple protein families are involved in the signaling pathways. Pdf the perforin mediated apoptotic pathway in lung injury. Nk cells switch from granzyme b to death receptormediated. Granzyme bmediated apoptosis proceeds predominantly through. The differential contribution of granzyme a and granzyme b in cytotoxic t lymphocyte mediated apoptosis is determined by the quality of target cells. Studies in perforindeficient mice have demonstrated that perforin is crucial for nk cellmediated cytotoxicity kagi et al. Granzyme binduced mitochondrial ros are required for apoptosis.
Death pathways activated by granzyme b in cancer cells 7. They independently induce death when delivered into the target cell with perforin pfn, a poreforming protein. It is secreted by these cells along with the pore forming protein perforin to mediate apoptosis in target cells. Here we present data supporting the notion that granzyme b mediated cell death is largely dependent on a pathway that is inhibitable by bcl2 or its. We clinically studied whether ctl mediated apoptosis associated with peptic ulcer formation may occur via either or both of these two pathways. This pathway can be inhibited by either granzyme a inhibitor 3,4dci or bcl2. The human cathelicidin, ll37, induces granzymemediated apoptosis in regulatory t cells jamie s. Inhibition of the proteolytic activities of caspases and granzyme b prevented granzyme binduced smc death, whereas attenuation of granzyme b.
Thus, in the early phase of ards, the perforin granzyme pathway may be activated. Thiery j, keefe d, saffarian s, martinvalet d, walch m, boucrot e, et al. Cytotoxic lymphocytes may induce apoptosis in their target cells by the fasl fas ligand pathway or the perforin granzyme b pathway. We show in this report that perforindependent, gzmbindependent cytotoxicity is caused by gzma or tightly linked genes. Wildtype islet cells treated with perforin granzyme b had increased cytochrome c release consistent with mitochondrial damage fig. Jan 26, 2015 in conclusion, after chmp5 inhibition, both granzyme bperforin apoptotic pathway and apoptosis inducing factor mediated necrotic pathway were activated, while autophagic pathway was not activated. When intrinsic apoptosis pathways are blocked by a caspase9 inhibitor, tnf.
Perforingranzyme apoptosis pathway creative diagnostics. In physiological settings it is possible that granzyme b also utilizes caspase8 activation as a means to. We report that the serine protease granzyme b grb, which is crucial for granulemediated cell killing, initiates apoptosis in target cells by first maturing caspase10. The latter pathway has largely been defined by the roles of the poreforming protein perforin and by the serine proteinases granzymes a and b. Perforingranzymeinduced apoptosis is the main pathway used by cytotoxic lymphocytes to. Granzyme b induces smooth muscle cell apoptosis in the. Perforin and granzyme b expression were examined in idiopathic pulmonary fibrosis by means. Despite the ability to engage the death pathway at multiple entry points, the preferred mechanism for rapid induction of apoptosis by granzyme b. Cls themselves resist granule mediated apoptosis but are eventually. Cytotoxic lymphocytes cls induce caspase activation and apoptosis of target cells either through fas activation or through release of granule cytotoxins, particularly granzyme b.
Granzyme gzm bdeficient cytotoxic lymphocytes ctl have a severe defect in the rapid induction of target cell apoptosis that is almost completely corrected by prolonged incubation of. Purified perforin induces lysis of target cells without dna fragmentation, whereas the addition of granzyme a or b to intact cells restores the apoptotic activity. In nk cells and t cells, granzymes are packaged in cytotoxic granules with perforin. Role of granzyme a in glucocorticoidinduced apoptosis in leukemia cells. During granule mediated killing by cytotoxic t lymphocytes or natural killer cells, the serine protease granzyme b enters the target cell by endocytosis and induces apoptosis. In early studies involving bcl2 in ctlmediated apoptosis, it appeared that target cell expression of the protooncogene. Besides the release of perforin and granzymes, ctl and nk cells can also present cd95l or tnfrelated apoptosisinducing ligand trail on their surface. Whereas tumors previously were shown to exhibit mechanisms for blocking the death receptor pathway, we now demonstrate that they also can resist ctl mediated killing through interference with the perforinygrb. Granzyme a initiates an alternative pathway for granulemediated apoptosis receptor engagement leads to activation of the caspases, which ultimately cleave substrates that are critical for the induction of apoptosis enari et al. Despite recent advances outlining the mechanisms of action of granzyme b within the target cell, there are still numerous conflicting reports regarding the requirements and dependence of granzyme b mediated apoptosis on caspases and. Granzyme a initiates an alternative pathway for granule mediated apoptosis receptor engagement leads to activation of the caspases, which ultimately cleave substrates that are critical for the induction of apoptosis enari et al.
At present, at least 2 major pathways of caspase activation have been revealed. Current research emphasis includes the role of granzymemediated apoptosis in diseases. Granulemediated killing by granzyme b and perforin requires. Gzmb activates caspase cell death pathways by initiating effector caspase cleavage and by directly cleaving some key caspase pathway substrates, such as bid. Then, granzyme a together with granzyme b are introduced into the target cell through the pore and activate the caspase family of proteases leading to apoptosis 19, 20. Sep 25, 2001 however, tumors often have managed to escape from the cytolytic machinery of these effector cells. Therefore, in addition to its role in the activation of mitochondria during apoptosis, these results suggest a role for granzyme b in the. We discuss the perforingranzyme apoptosis pathway on how the cytotoxic granule mediates cell death and the functional significance of this pathway. Perforingranzymeinduced apoptosis is the main pathway used by cytotoxic lymphocytes to kill virusinfected and transformed cells. Granzyme b biosynthesis, subcellular localization and activation 4.
Apoptotic pathways are selectively activated by granzyme a andor granzyme b in ctl mediated target cell lysis. Perforin activates clathrin and dynamindependent endocytosis, which is required for plasma membrane repair and delivery of granzyme b for granzyme mediated apoptosis. Granzyme a gzma activates a caspaseindependent cell death pathway with morphological features of apoptosis but has unique substrates and mediators 2. Granzyme bmediated apoptosis proceeds predominantly through a.
The perforin mediated apoptotic pathway in lung injury and. Perforin granzyme apoptosis pathway is the primary signaling pathway used by cytotoxic lymphocytes to eliminate virusinfected andor transformed cells. The granzymes are cell deathinducing enzymes, stored in the cytotoxic granules of cytotoxic t lymphocytes and natural killer cells, that are released during. Perforin and granzyme b expression were examined in idiopathic pulmonary fibrosis by means of immunohistochemistry, and perforin knockout mice were used to examine whether or not perforin mediated. Pdf the perforin mediated apoptotic pathway in lung. Granzyme a mediates glucocorticoidinduced apoptosis in. Pdf dependence of granzyme bmediated cell death on a. The perforin granzyme pathway is a series of immune reactions driven by cytotoxic tcell in infectedcancerous cells with which the target cell is finally eliminated. Ctls involves the induction of apoptosis by two major mechanisms. Pdf ros signaling during granzyme bmediated apoptosis. Following receptor mediated conjugate formation between a granzyme containing cell and an infected or transformed target cell, granzymes enter the target cell via endocytosis and induce apoptosis. However, if caspases are activated first for example, via granzyme b, then parp is cleaved to a dominantnegative form, which can prevent parp mediated energy depletion and allow apoptosis. The data therefore support the existence of a fully. The proapoptotic bh3only protein bid is a substrate for cleavage by granzyme b in hemopoietic cells 18.
Perforin is a poreforming protein and also known as cytoplasmic granule toxins. Perforin and granzymemediated apoptosis is the principle pathway that nk cells use to kill tumors and virusinfected cells. Apoptotic pathways are selectively activated by granzyme a. Granzyme a from cytotoxic lymphocytes cleaves gsdmb to. The extrinsic, intrinsic, and granzyme b pathways converge on the same terminal, or execution pathway. Antibodies produced by b cells can mediate classical. Gzm a may initiate apoptosis by activating an alternate pathway that has many protease components, akin to the complement pathway or the coagulation cascade. The human cathelicidin, ll37, induces granzymemediated. Activated splenocytes from perforinknockout mice induced smc death through a granzyme b mediated pathway. Granzyme a gzma activates a caspaseindependent cell death pathway with morphological features of apoptosis. Granzyme a initiates an alternative pathway for granule. The aim of the present study was to understand the mechanism of apoptosis in an elastaseinduced aneurysm model in.
There is an additional pathway that involves tcell mediated cytotoxicity and perforin granzyme dependent killing of the cell. Also, because granzyme b can activate the effector caspases directly, we sought to determine the necessity for cytochrome c release and its contribution to the efficient death in target cell apoptosis. The aims of this study were to determine whether cc cells are also resistant to perforin granzyme b and whether the fasl resistance lies upstream of. Granzyme a is a homodimer of total size about 60 kda that cleaves peptide bonds after arginine residues. Upregulation of two death pathways of perforingranzyme. We report that the serine protease granzyme b grb, which is crucial for granule mediated cell killing, initiates apoptosis in target cells by first maturing caspase10. Studies in genedisrupted mice indicate that perforin, in combination with granzyme, could induce apoptosis. Granzyme b is the most powerful proapoptotic member of the granzyme family.
Granzymes also kill bacteria and inhibit viral replication. Previous studies suggested a role for the mannose 6phosphate receptor, but further experiments with purified granzyme b indicated this was not essential. Granzyme b plays a pivotal role in the rapid induction of caspasedependent apoptosis. Contrary to original hypotheses, granzyme a does not appear to be particularly important for cytotoxicity. Blockade of the granzyme byperforin pathway through. Granzyme mediated cell death is a critical mechanism for cytotoxic lymphocytes to eliminate malignant cells in antitumor immunity. It has been shown that fasexpressing colon carcinoma cc cells are resistant to fasl mediated apoptosis. Functional significance of the perforingranzyme cell death. Amongst these, granzyme b and perforin have been shown to induce ctl.
Granzyme a gzma is the most abundant serine protease in killer cell cytotoxic granules. Frontiers singlefluorescent protein reporters allow. The pathophysiology of saccular aneurysms is complex and multifactorial. The apoptotic signaling pathways that lead to caspase zymogens processing can be subdivided into two major categories. After entering the cytosol of target cells, gzma is specifically imported into mitochondria through the timtompam import pathway. Upregulation of two death pathways of perforingranzyme and. Examination of cytotoxic t lymphocytemediated apoptosis. Perforin and granzyme b expression were examined in idiopathic. Granzymea gzma, a tryptase, and granzymeb gzmb, a serine protease, are the most abundant granules. Targetcell killing by ctls involves the induction of apoptosis by two major mechanisms. The perforin granzyme pathway can induce apoptosis via either granzyme b or granzyme a. This serine protease is also called granzyme a masson and tschopp, 1987. Granzyme gzm bdeficient cytotoxic lymphocytes ctl have a severe defect in the rapid induction of target cell apoptosis that is almost completely corrected by prolonged incubation of the ctl effectors and their targets.
The mitochondrial apoptotic pathway activated via bim is critically involved in apoptosis induced by mouse granzyme b. It is vital for cytotoxic effector function and has an indispensable, but an undefined role in granzyme mediated apoptosis. Granzyme b also induces caspaseindependent events leading to dna fragmentation in the target cell, and mitochondrial dysfunction involving proapoptotic cytochrome c release. Pdf apoptotic pathways are selectively activated by. Granzyme a can induce target cell apoptosis in vitro, but does so much more slowly than granzyme. Human granzyme b mediated apoptosis is in part mediated by mitochondria. The molecular pathways responsible for apoptosis in response to granzyme b have remained unresolved. Perforingranzyme b pathway during an immune response to viruses and cellular transformation, cytotoxic cells including cytotoxic t lymphocytes ctls and natural killer nk cells identify affected cells and release serine proteases known as. Ll37 is a human cationic host defense peptide antimicrobial peptide belonging to the cathelicidin family of peptides. Therefore, it is very important to chart the mechanisms through which this escape can occur.
Lymphocyte granulemediated cytotoxicity is designed to protect the host from invasion by intracellular pathogens, tumor, and nonself cells. The perforin mediated pathway is the major pathway of cytotoxicity induced by activated t cells and natural killer cells, and may be involved in the development of pulmonary fibrosis. Perforin is the cytotoxic pore forming protein, which mediates target cell lysis by ctls and nk cells, 6, 7 whereas granzyme b is a serine protease released by ctls and nk cells, which triggers a series of biochemical events that lead to apoptosis. In addition, grb has a limited capacity to mature other caspases and to cause cell death independently of the caspases. The main function of the fasfas ligand fasl pathway is to. Perforin granzymeinduced apoptosis is the main pathway used by cytotoxic lymphocytes to. Islet cells deficient in bid are resistant to granzyme b mediated apoptosis.
Perforin granzyme and fasfas ligand fas l pathways are two known major pathways of cytotoxic t lymphocyte ctl mediated apoptosis. Granzyme b grb is a serine protease most commonly found in the granules of natural killer cells nk cells and cytotoxic t cells. Upon entry into target cells, the granzymes cleave substrates that ultimately result in cell death. Initiation of apoptosis by granzyme b requires direct. Blockade of the granzyme bperforin pathway through. Apoptosis is executed by the extrinsic or intrinsic death signaling pathways, or in some cases by the perforin granzyme b pathway and results in the activation of the caspase cascade. They induce programmed cell death apoptosis in the target cell, thus eliminating cells that have become cancerous or are infected with viruses or bacteria. Alternatively, this enzyme may directly cleave critical apoptotic target proteins but at a slow rate. We therefore hypothesized that gzmainduced and gsdmbdependent pyroptosis may have an important function in ctl mediated tumor clearance, particularly given the proinflammatory nature of pyroptosis. So far, little is known regarding the role of perforin mediated apoptosis in lichen planus. A main pathway used by cytotoxic t lymphocytes ctls and natural killer cells to eliminate pathogenic cells is via exocytosis of granule components in the direction of the target cell, delivering a lethal hit of cytolytic molecules. Herein, we show that granzyme b triggers the mitochondrial apoptotic pathway through direct cleavage of bid. Figure 1a is a photomicrograph of a section of exocrine pancreas from a b6c3f1 mouse. Granzyme b is the most extensively studied granzyme and is responsible for the rapid induction of caspasedependent apoptosis trapani and sutton, 2003.
The essential upstream steps in granzyme b mediated apoptosis remain undefined. The role of perforinmediated apoptosis in lichen planus. Granzyme b is a serine protease most commonly found in the granules of natural killer cells nk cells and cytotoxic t cells. Intrinsic pathway mediated apoptosis in elastaseinduced aneurysms in rabbits r. Granzyme binduced apoptosis in cancer cells and its. Thus, in the early phase of ards, the perforin granzyme pathway may be activated to cause lung epithelial and endothelial cell death. The mechanism by which granzyme b activate apoptosis is therefore of significant interest. Receptor and mitochondrialmediated apoptosis in acute. Gzma activates caspaseindependent death morphologically identical to apoptosis. Glucocorticoid increases expression and enzymatic activity of granzyme a leading to apoptosis in 697 leukemia cells. Cytotoxic lymphocytes induce target cell apoptosis via two major pathways. Gzma activates a novel programmed cell death pathway that begins in the mitochondrion, where cleavage of ndufs3 in electron transport complex i disrupts mitochondrial.
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