Apoptotic Events (apoptotic + event)

Distribution by Scientific Domains


Selected Abstracts


The glycoprotein Ib,,von Willebrand factor interaction induces platelet apoptosis

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2 2010
S. LI
Summary.,Background: The interaction of glycoprotein (GP) Ib, with von Willebrand factor (VWF) initiates platelet adhesion, and simultaneously triggers intracellular signaling cascades leading to platelet aggregation and thrombus formation. Some of the signaling events are similar to those occurring during apoptosis, however, it is still unclear whether platelet apoptosis is induced by the GPIb,,VWF interaction. Objectives: To investigate whether the GPIb,,VWF interaction induces platelet apoptosis and the role of 14-3-3, in apoptotic signaling. Methods: Apoptotic events were assessed in platelets or Chinese hamster ovary (CHO) cells expressing wild-type (1b9) or mutant GPIb,IX interacting with VWF by flow cytometry or western blotting. Results: Ristocetin-induced GPIb,,VWF interaction elicited apoptotic events in platelets, including phosphatidylserine exposure, elevations of Bax and Bak, gelsolin cleavage, and depolarization of mitochondrial inner transmembrane potential. Apoptotic events were also elicited in platelets exposed to pathologic shear stresses in the presence of VWF; however, the shear-induced apoptosis was eliminated by the anti-GPIb, antibody AK2. Furthermore, apoptotic events occurred in 1b9 cells stimulated with VWF and ristocetin, but were significantly diminished in two CHO cell lines expressing mutant GPIb,IX with GPIb, truncated at residue 551 or a serine-to-alanine mutation at the 14-3-3,-binding site in GPIb,. Conclusions: This study demonstrates that the GPIb,,VWF interaction induces apoptotic events in platelets, and that the association of 14-3-3, with the cytoplasmic domain of GPIb, is essential for apoptotic signaling. This finding may suggest a novel mechanism for platelet clearance or some thrombocytopenic diseases. [source]


Role of ceramide kinase in peroxisome proliferator-activated receptor beta-induced cell survival of mouse keratinocytes

FEBS JOURNAL, Issue 15 2008
Kiyomi Tsuji
Ceramide (Cer) is known to be a lipid mediator in apoptosis and to have an important role in cell fate, via control of intracellular Cer levels. Recently, ceramide kinase (CerK) was identified as an enzyme that converts Cer to ceramide 1-phosphate (C1P). We examined potential functions of CerK in the regulation of keratinocyte survival, and the possible involvement of peroxisome proliferator-activated receptor beta (PPAR,). PPAR, is known to be a nuclear receptor acting as a ligand-inducible transcription factor and has been implicated in the control of keratinocyte survival. In the mouse keratinocyte cell line SP1, serum starvation induced cell death and the accumulation of intracellular Cer, an apoptotic event. However, apoptosis was inhibited by activation of PPAR,. Interestingly, activation of PPAR, enhanced the mRNA expression of CerK and CerK activity. Furthermore, the cell survival effect of PPAR, was greatly diminished in keratinocytes isolated from CerK-null mice. Chromatin immunoprecipitation revealed that, in vivo, PPAR, binds to the CerK gene via a sequence located in the first intron. Electrophoretic mobility-shift assays confirmed that PPAR, associates with this sequence in vitro. These findings indicated that CerK gene expression was directly regulated by PPAR,. In conclusion, our results demonstrate that PPAR,-mediated upregulation of CerK gene expression is necessary for keratinocyte survival against serum starvation-induced apoptosis. [source]


The role of mitochondria, cytochrome c and caspase-9 in embryonic lens fibre cell denucleation

JOURNAL OF ANATOMY, Issue 2 2002
E. J. Sanders
Abstract During the differentiation of secondary lens fibre cells from the lens epithelium, the fibre cells lose all of their cytoplasmic organelles as well as their nuclei. The fibre cells, containing crystallins, which confer optical clarity, then persist in the adult lens. The process of denucleation of these cells has been likened to an apoptotic event which is not followed by the plasma membrane changes that are characteristic of apoptosis. We have examined the expression and subcellular translocation of molecules of the apoptotic cascade in differentiating lens epithelial cells in culture. In this culture system, the epithelial cells differentiate into lentoids composed of lens fibre cells. We find that caspase-9, which is expressed and activated before embryonic day 12 in intact lenses, is localized in the cytosol outside mitochondria in non-differentiating cultured cells. In lentoid cells, caspase-9 migrates into mitochondria after the latter undergo a membrane permeability transition that is characteristic of apoptotic cells. At the same time, caspase-9 co-localizes with cytochrome c in the cytosol. The cytochrome c is apparently released from the mitochondria in lentoid cells after the mitochondrial membrane permeability transition and during the period of nuclear shrinkage. Also during this time, the mitochondria aggregate around the degenerating nuclei. Cytochrome c disappears rapidly, while mitochondrial breakdown occurs approximately coincident with the disappearance of the nuclei, but mitochondrial remnants persist together with cytochrome c oxidase, which is a mitochondrial marker protein. Apaf-1, another cytosolic protein of the apoptotic cascade, also migrates to the permeabilized mitochondria and also co-localizes with caspase-9 and cytochrome c in the cytosol or mitochondria of denucleating cells, thus providing evidence for the formation of an ,apoptosome' in these cells, as in apoptotic cells. At no time did we observe the translocation of molecules between cytoplasmic compartments and the nucleus in differentiating lentoid cells. We suggest that the uncoupling of nuclear and membrane apoptotic events in these cells may be due to the early permeability changes in the mitochondria, resulting in the loss of mitochondrial signalling molecules, or to the failure of molecules to migrate to the nucleus in these cells, thus failing to activate nuclear-plasma membrane signalling pathways. [source]


Hydroxychloroquine potentiates Fas-mediated apoptosis of rheumatoid synoviocytes

CLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 3 2006
W.-U. Kim
Summary Inadequate apoptosis may contribute to the synovial hyperplasia associated with rheumatoid arthritis (RA). The Fas-associated death domain protein (FADD)-like interleukin (IL)-1,-converting enzyme (FLICE)-inhibitory protein (FLIP), which is an apoptotic inhibitor, has been implicated in the resistance to Fas-mediated apoptosis of synoviocytes. This study investigated whether hydroxychloroquine (HCQ), an anti-rheumatic drug, induces the apoptosis of rheumatoid synoviocytes, and modulates the expression of FLIP. Fibroblast-like synoviocytes (FLS) were prepared from the synovial tissues of RA patients, and were cultured with various concentrations of HCQ in the presence or absence of the IgM anti-Fas monoclonal antibodies (mAb) (CH11). Treatment with HCQ, ranging from 1 to 100 µM, induced the apoptosis of FLS in a dose- and time-dependent manner. The increase in synoviocytes apoptosis by HCQ was associated with caspase-3 activation. A combined treatment of HCQ and anti-Fas mAb increased FLS apoptosis and caspase-3 activity synergistically, compared with either anti-Fas mAb or HCQ alone. The Fas expression level in the FLS was not increased by the HCQ treatment, while the FLIP mRNA and protein levels were decreased rapidly by the HCQ treatment. Moreover, time kinetics analysis revealed that the decreased expression of FLIP by HCQ preceded the apoptotic event that was triggered by HCQ plus anti-Fas mAb. Taken together, HCQ increases the apoptosis of rheumatoid synoviocytes by activating caspase-3, and also sensitizes rheumatoid synoviocytes to Fas-mediated apoptosis. Our data suggest that HCQ may exert its anti-rheumatic effect in rheumatoid joints through these mechanisms. [source]


Gli3 null mice display glandular overgrowth of the developing stomach

DEVELOPMENTAL DYNAMICS, Issue 4 2005
Jae H. Kim
Abstract The role of the Hedgehog signaling pathway in various aspects of gut development is still poorly understood. In the developing stomach, Sonic (Shh) and Indian (Ihh) hedgehog are expressed in both distinct and overlapping regions. Loss of Sonic hedgehog function in the stomach results in a glandular phenotype of intestinal transformation and overgrowth. These changes are reminiscent of the pre-malignant lesion, intestinal metaplasia. To determine the role of Hedgehog-related transcription factors, Gli2 and Gli3, in Shh signaling during stomach development, we conducted a mutant analysis of glandular stomach from Shh, Gli2, and Gli3 mutant mice. Although Gli2 principally mediates the activator function of Shh, surprisingly we observed minimal changes in glandular development in the Gli2 mutant stomach. Furthermore, Gli3, which typically functions as a repressor of Hedgehog signal, showed a striking phenocopy of the glandular expansion and intestinal transformation found in Shh mutant stomach. A reduction in apoptotic events was seen in all mutant stomachs with no appreciable changes in proliferation. Both Shh and Gli3 mutant stomachs displayed early changes of intestinal transformation but these did not impact on the overall differentiation of the gastric epithelium. Interestingly, the observation that Gli3 shares a similar glandular phenotype to Shh mutant stomach reveals a possible novel role of Gli3 activator in the developing stomach. The embryonic stomach is a unique model of the Hedgehog pathway function and one that may help to uncover some of the mechanisms underlying the development of intestinal metaplasia. Developmental Dynamics 234:984,991, 2005. © 2005 Wiley-Liss, Inc. [source]


,-Arrestin 2 regulates toll-like receptor 4-mediated apoptotic signalling through glycogen synthase kinase-3,

IMMUNOLOGY, Issue 4 2010
Hui Li
Summary Toll-like receptor 4 (TLR4), a key member of the TLR family, has been well characterized by its function in the induction of inflammatory products of innate immunity. However, the involvement of TLR4 in a variety of apoptotic events by an unknown mechanism has been the focus of great interest. Our investigation found that TLR4 promoted apoptotic signalling by affecting the glycogen synthase kinase-3, (GSK-3,) pathway in a serum-deprivation-induced apoptotic paradigm. Serum deprivation induces GSK-3, activation in a pathway that leads to subsequent cell apoptosis. Intriguingly, this apoptotic cascade is amplified in presence of TLR4 but greatly attenuated by ,-arrestin 2, another critical molecule implicated in TLR4-mediated immune responses. Our data suggest that the association of ,-arrestin 2 with GSK-3, contributes to the stabilization of phospho-GSK-3,, an inactive form of GSK-3,. It becomes a critical determinant for the attenuation of TLR4-initiated apoptosis by ,-arrestin 2. Taken together, we demonstrate that the TLR4 possesses the capability of accelerating GSK-3, activation thereby deteriorating serum-deprivation-induced apoptosis; ,-arrestin 2 represents an inhibitory effect on the TLR4-mediated apoptotic cascade, through controlling the homeostasis of activation and inactivation of GSK-3,. [source]


The role of mitochondria, cytochrome c and caspase-9 in embryonic lens fibre cell denucleation

JOURNAL OF ANATOMY, Issue 2 2002
E. J. Sanders
Abstract During the differentiation of secondary lens fibre cells from the lens epithelium, the fibre cells lose all of their cytoplasmic organelles as well as their nuclei. The fibre cells, containing crystallins, which confer optical clarity, then persist in the adult lens. The process of denucleation of these cells has been likened to an apoptotic event which is not followed by the plasma membrane changes that are characteristic of apoptosis. We have examined the expression and subcellular translocation of molecules of the apoptotic cascade in differentiating lens epithelial cells in culture. In this culture system, the epithelial cells differentiate into lentoids composed of lens fibre cells. We find that caspase-9, which is expressed and activated before embryonic day 12 in intact lenses, is localized in the cytosol outside mitochondria in non-differentiating cultured cells. In lentoid cells, caspase-9 migrates into mitochondria after the latter undergo a membrane permeability transition that is characteristic of apoptotic cells. At the same time, caspase-9 co-localizes with cytochrome c in the cytosol. The cytochrome c is apparently released from the mitochondria in lentoid cells after the mitochondrial membrane permeability transition and during the period of nuclear shrinkage. Also during this time, the mitochondria aggregate around the degenerating nuclei. Cytochrome c disappears rapidly, while mitochondrial breakdown occurs approximately coincident with the disappearance of the nuclei, but mitochondrial remnants persist together with cytochrome c oxidase, which is a mitochondrial marker protein. Apaf-1, another cytosolic protein of the apoptotic cascade, also migrates to the permeabilized mitochondria and also co-localizes with caspase-9 and cytochrome c in the cytosol or mitochondria of denucleating cells, thus providing evidence for the formation of an ,apoptosome' in these cells, as in apoptotic cells. At no time did we observe the translocation of molecules between cytoplasmic compartments and the nucleus in differentiating lentoid cells. We suggest that the uncoupling of nuclear and membrane apoptotic events in these cells may be due to the early permeability changes in the mitochondria, resulting in the loss of mitochondrial signalling molecules, or to the failure of molecules to migrate to the nucleus in these cells, thus failing to activate nuclear-plasma membrane signalling pathways. [source]


Nerve growth factor blocks thapsigargin-induced apoptosis at the level of the mitochondrion viaregulation of Bim

JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 6a 2008
E. Szegezdi
Abstract This study examined how the neurotrophin, nerve growth factor (NGF), protects PC12 cells against endoplasmic reticulum (ER) stress-induced apoptosis. ER stress was induced using thapsigargin (TG) that inhibits the sarcoplasmic/ER Ca2+ -ATPase pump (SERCA) and depletes ER Ca2+ stores. NGF pre-treatment inhibited translocation of Bax to the mitochondria, loss of mitochondrial transmembrane potential, cytochrome c release, activation of caspases (,3, ,7 and ,9) and apoptosis induction by TG. Notably, TG also caused a marked induction of Bimel mRNA and protein, and knockdown of Bim with siRNA protected cells against TG-induced apoptosis. NGF delayed the induction and increased the phosphorylation of Bimel. NGF-mediated protection was dependent on phosphatidylinositol-3 kinase (PI3K) signalling since all above apoptotic events, including expression and phosphorylation status of Bimel protein, could be reverted by the PI3K inhibitor LY294002. In contrast, NGF had no effect on the TG-mediated induction of the unfolded protein response (increased expression of Grp78, GADD34, splicing of XBP1 mRNA) or ER stress-associated pro-apoptotic responses (induction of C/EBP homologous protein [CHOP], induction and processing of caspase-12). These data indicate that NGF-mediated protection against ER stress-induced apoptosis occurs at the level of the mitochondria by regulating induction and activation of Bim and mitochondrial translocation of Bax. [source]


Hydrogen peroxide overproduced in breast cancer cells can serve as an anticancer prodrug generating apoptosis-stimulating hydroxyl radicals under the effect of tamoxifen-ferrocene conjugate

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 11 2007
Wjatschesslaw A. Wlassoff
A new approach to the treatment of cancer is suggested, based on the innate overproduction of hydrogen peroxide in cancer cells. Hydrogen peroxide serves as a prodrug in the presence of transition metal ions, such as iron delivered by ferrocene. Under the effect of ferrocene, hydrogen peroxide is split into hydroxyl anions and highly reactive hydroxyl radicals. The latter cause oxidative DNA damage, which induces apoptosis, leading to elimination of cancer cells. Tamoxifen, a drug that interacts with oestrogen receptors, was used as a carrier to deliver ferrocene to breast cancer cells. For this aim tamoxifen conjugated to ferrocene (Tam-Fer) was synthesized. We have shown that the frequency of apoptotic events in MCF-7 breast cancer cells treated with Tam-Fer is significantly higher than in cells treated with tamoxifen or ferrocene separately. The increase of apoptosis correlates well with the rise in generation of reactive oxygen species in cancer cells. These results show that the hydrogen peroxide overproduced in tumour cells can serve as a prodrug for the treatment of cancer. [source]


Effect of Chronic Ethanol Ingestion on Alveolar Type II Cell: Glutathione and Inflammatory Mediator-Induced Apoptosis

ALCOHOLISM, Issue 7 2001
Lou Ann S. Brown
Background : In septic patients, chronic alcohol abuse increases the incidence of the acute respiratory distress syndrome, a syndrome that requires alveolar type II cell proliferation and differentiation for repair of the damaged alveolar epithelium. We previously showed in a rat model that chronic ethanol ingestion decreased the antioxidant glutathione (GSH) in type II cells and exacerbated endotoxin-mediated acute lung injury. We hypothesized that this GSH depletion by ethanol, particularly mitochondrial GSH, predisposed type II cells to inflammatory mediator-induced apoptosis. Methods: Adult male rats were fed the Lieber-DeCarli diet for 2, 6, or 16 weeks. Alveolar type II cells were then isolated and treated with hydrogen peroxide or TNF-,. The effect on glutathione (cytosolic and mitochondrial), apoptotic events, and necrosis were determined. In other studies, rats were fed ethanol for 6 weeks and were treated with endotoxin and apoptosis of type II cells determined by the TUNEL method. Results: Chronic ethanol ingestion alone resulted in a progressive decrease in mitochondrial GSH and a progressive increase in the basal apoptosis and necrosis rate (p, 0.05). Furthermore, there was a progressive increase in the sensitivity of the cells to H2O2 or TNF-, induced cytochrome c release, caspase 3 activation, apoptosis, and necrosis (p, 0.05). Finally, there was a 2-fold increase in apoptotic type II cells in vivo when chronic ethanol ingestion was superimposed on endotoxemia. Conclusions: These results suggested that chronic ethanol ingestion resulted in a progressive depletion of mitochondrial GSH and sensitization of type II cells to inflammatory mediator-induced apoptosis and necrosis. These effects may be particularly relevant during acute stress when proliferation and differentiation of these cells are critical to repair of the damaged alveolar epithelium and may have important ramifications for the treatment of acute respiratory distress syndrome in patients with a history of alcohol abuse. [source]


The glycoprotein Ib,,von Willebrand factor interaction induces platelet apoptosis

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2 2010
S. LI
Summary.,Background: The interaction of glycoprotein (GP) Ib, with von Willebrand factor (VWF) initiates platelet adhesion, and simultaneously triggers intracellular signaling cascades leading to platelet aggregation and thrombus formation. Some of the signaling events are similar to those occurring during apoptosis, however, it is still unclear whether platelet apoptosis is induced by the GPIb,,VWF interaction. Objectives: To investigate whether the GPIb,,VWF interaction induces platelet apoptosis and the role of 14-3-3, in apoptotic signaling. Methods: Apoptotic events were assessed in platelets or Chinese hamster ovary (CHO) cells expressing wild-type (1b9) or mutant GPIb,IX interacting with VWF by flow cytometry or western blotting. Results: Ristocetin-induced GPIb,,VWF interaction elicited apoptotic events in platelets, including phosphatidylserine exposure, elevations of Bax and Bak, gelsolin cleavage, and depolarization of mitochondrial inner transmembrane potential. Apoptotic events were also elicited in platelets exposed to pathologic shear stresses in the presence of VWF; however, the shear-induced apoptosis was eliminated by the anti-GPIb, antibody AK2. Furthermore, apoptotic events occurred in 1b9 cells stimulated with VWF and ristocetin, but were significantly diminished in two CHO cell lines expressing mutant GPIb,IX with GPIb, truncated at residue 551 or a serine-to-alanine mutation at the 14-3-3,-binding site in GPIb,. Conclusions: This study demonstrates that the GPIb,,VWF interaction induces apoptotic events in platelets, and that the association of 14-3-3, with the cytoplasmic domain of GPIb, is essential for apoptotic signaling. This finding may suggest a novel mechanism for platelet clearance or some thrombocytopenic diseases. [source]


Ischemic preconditioning attenuates the oxidant-dependent mechanisms of reperfusion cell damage and death in rat liver

LIVER TRANSPLANTATION, Issue 11 2002
Barbara Cavalieri
In an in vivo rat model of liver ischemia followed by reperfusion a consistent appearance of necrosis and activation of biochemical pathways of apoptosis was reproduced and monitored after 30 minutes reperfusion. Preconditioning by application of a short cycle of ischemia-reperfusion (10 minutes + 10 minutes) positively conditioned recovery of the organ at reperfusion, attenuating both necrotic and apoptotic events. Preconditioning at least halved cell oxidative damage occurring early at reperfusion, and as a major consequence, the increase of cytolysis and apoptosis occurring at reperfusion was about 50% less. The attenuation of both pathways of cell death by preconditioning appeared at least partly related to its modulate action on H2O2 and 4-hydroxy-2,3-trans-nonenal production. The overall data point to a marked diminished oxidant generation and oxidative reactions as one major possible mechanism through which ischemic preconditioning exerts protection against necrotic and apoptotic insult to the postischemic liver. [source]


In vitro targeted photodynamic therapy with a pyropheophorbide-a conjugated inhibitor of prostate-specific membrane antigen

THE PROSTATE, Issue 6 2009
Tiancheng Liu
Abstract BACKGROUND The lack of specific delivery of photosensitizers (PSs), represents a significant limitation of photodynamic therapy (PDT) of cancer. The biomarker prostate-specific membrane antigen (PSMA) has attracted considerable attention as a target for imaging and therapeutic applications for prostate cancer. Although recent efforts have been made to conjugate inhibitors of PSMA with imaging agents, there have been no reports on PS-conjugated PSMA inhibitors for targeted PDT of prostate cancer. The present study focuses on the use of a PSMA inhibitor-conjugate of pyropheophorbide-a (Ppa-conjugate 2) for targeted PDT to achieve apoptosis in PSMA+ LNCaP cells. METHODS Confocal laser scanning microscopy with a combination of nuclear staining and immunofluorescence methods were employed to monitor the specific imaging and PDT-mediated apoptotic effects on PSMA-positive LNCaP and PSMA-negative (PC-3) cells. RESULTS Our results demonstrated that PDT-mediated effects by Ppa-conjugate 2 were specific to LNCaP cells, but not PC-3 cells. Cell permeability was detected as early as 2 hr by HOE33342/PI double staining, becoming more intense by 4 hr. Evidence for the apoptotic caspase cascade being activated was based on the appearance of poly-ADP-ribose polymerase (PARP) p85 fragment. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay detected DNA fragmentation 16 hr post-PDT, confirming apoptotic events. CONCLUSIONS Cell permeability by HOE33342/PI double staining as well as PARP p85 fragment and TUNEL assays confirm cellular apoptosis in PSMA+ cells when treated with PS-inhibitor conjugate 2 and subsequently irradiated. It is expected that the PSMA targeting small-molecule of this conjugate can serve as a delivery vehicle for PDT and other therapeutic applications for prostate cancer. Prostate 69:585,594, 2009. © 2009 Wiley-Liss, Inc. [source]


Comparison of apoptosis and mortality measurements in peripheral blood mononuclear cells (PBMCs) using multiple methods

CELL PROLIFERATION, Issue 5 2005
S. Glisic-Milosavljevic
Death through apoptosis is the main process by which aged cells that have lost their function are eliminated. Apoptotic cells are usually detected microscopically by changes in their morphology. However, determination of early apoptotic events is important for in vitro (and ex vivo) studies. The main objective of the present study is to find the most sensitive method for apoptosis detection in human peripheral blood mononuclear cells (PBMCs) by comparing six different methods following five different means of immunological stimulation at 3 and 5 days. Each of six apoptosis quantification methods, except the trypan blue exclusion test, is a combination of two stains, one for the specific detection of apoptotic cells and the other for the unspecific detection of dead cells. Values for apoptosis and mortality were compared with a reference method. The choice of apoptosis detection method is more important following 3 days of stimulation than after 5 days of stimulation (P = 2 × 10,6 versus P = 1 × 10,2). In contrast, we find mortality measurements following the different means of stimulation highly significant at both 3 and 5 days (F2.28 = 7.9, P = 1.4 × 10,6 at 3 days and F2.28 = 8.5, P = 4.5 × 10,7 at 5 days). Variation as a result of the combination of specific PBMC stimulation and the method used to detect apoptosis is reduced considerably with time (F1.58 + 3.7, P + 3 × 10,7 at 3 days to F = (1.58) = 0.97, P = 0.5 at 5 days). Based on Tukey's test, YO-PRO-1 is the most sensitive stain for apoptosis and, when combined with 7-AAD, provides an accurate measure of apoptosis and mortality. In conclusion, we propose YO-PRO-1/7-AAD as a new combination and low-cost alternative for the sensitive detection of early apoptosis. [source]


Ringing the alarm bells: signalling and apoptosis in influenza virus infected cells

CELLULAR MICROBIOLOGY, Issue 3 2006
Stephan Ludwig
Summary Small RNA viruses such as influenza viruses extensively manipulate host-cell functions to support their replication. At the same time the infected cell induces an array of defence mechanisms to fight the invader. These processes are mediated by a variety of intracellular signalling cascades. Here we will review the current knowledge of functional kinase signalling and apoptotic events in influenza virus infected cells and how these viruses have learned to misuse these cellular responses for efficient replication. [source]