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V Duronio

Publications and source records attributed to V Duronio.

At least 37 records · Page 2Linked to original sources
PubMed1999

The B cell antigen receptor activates the Akt (protein kinase B)/glycogen synthase kinase-3 signaling pathway via phosphatidylinositol 3-kinase.

We have previously shown that the B cell Ag receptor (BCR) activates phosphatidylinositol (PI) 3-kinase. We now show that a serine/threonine kinase called Akt or protein kinase B is a downstream target of PI 3-kinase in B cells. Akt has been shown to promote cell survival as well as the transcription and translation of proteins involved in cell cycle progression. Using an Ab that specifically recognizes the activated form of Akt that is phosphorylated on serine 473, we show that BCR engagement activates Akt in a PI 3-kinase-dependent manner. These results were confirmed using in vitro kinase assays. Moreover, BCR ligation also induced phosphorylation of Akt of threonine 308, another modification that is required for activation of Akt. In the DT40 chicken B cell line, phosphorylation of Akt on serine 473 was completely dependent on the Lyn tyrosine kinase, while the Syk tyrosine kinase was required for sustained phosphorylation of Akt. Complementary experiments in BCR-expressing AtT20 endocrine cells confirmed that Src kinases are sufficient for BCR-induced Akt phosphorylation, but that Syk is required for sustained phosphorylation of Akt on both serine 473 and threonine 308. In insulin-responsive cells, Akt phosphorylates and inactivates the serine/threonine kinase glycogen synthase kinase-3 (GSK-3). Inactivation of GSK-3 may promote nuclear accumulation of several transcription factors, including NF-ATc. We found that BCR engagement induced GSK-3 phosphorylation and decreased GSK-3 enzyme activity. Thus, BCR ligation initiates a PI 3-kinase/Akt/GSK-3 signaling pathway.

Animals↗
PubMed1999

Ceramide and cyclic adenosine monophosphate (cAMP) induce cAMP response element binding protein phosphorylation via distinct signaling pathways while having opposite effects on myeloid cell survival.

The role of ceramide as a second messenger is a subject of great interest, particularly since it is implicated in signaling in response to inflammatory cytokines. Ceramide induces apoptosis in both cytokine-dependent MC/9 cells and factor-independent U937 cells. Elevation of cyclic adenosine monophosphate (cAMP) levels inhibits apoptosis induced by ceramide and several other treatments. One target of cAMP-mediated signaling is the transcription factor CREB (cAMP response element binding protein), and recently CREB phosphorylation at an activating site has been shown to also be mediated by a cascade involving p38 mitogen-activated protein kinase (MAPK), one of the stress-activated MAP kinases. Because no role for p38 MAPK in apoptosis has been firmly established, we examined the relationship between p38 MAPK and CREB phosphorylation under various conditions. Ceramide, or sphingomyelinase, like tumor necrosis factor- (TNF-) or the hematopoietic growth factor, interleukin-3 (IL-3), was shown to activate p38 MAPK, which in turn activated MAPKAP kinase-2. Each of these treatments led to phosphorylation of CREB (and the related factor ATF-1). A selective p38 MAPK inhibitor, SB203580, blocked TNF-- or ceramide-induced CREB phosphorylation, but had no effect on the induction of apoptosis mediated by these agents. The protective agents cAMP and IL-3 also led to CREB phosphorylation, but this effect was independent of p38 MAPK, even though IL-3 was shown to activate both p38 MAPK and MAPKAP kinase-2. Therefore, the opposing effects on apoptosis observed with cAMP and IL-3, compared with ceramide and TNF-, could not be explained on the basis of phosphorylation of CREB. In addition, because SB203580 had no effect of TNF- or ceramide-induced apoptosis, our results strongly argue against a role for p38 MAPK in the induction of TNF-- or ceramide-induced apoptosis.

Animals↗
PubMed1999

The role of SHIP in growth factor induced signalling.

The recently cloned, hemopoietic-specific, src homology 2 (SH2)-containing inositol phosphatase, SHIP, is rapidly gaining prominence as a potential regulator of all phosphatidylinositol (PI)-3 kinase mediated events since it has been shown both in vitro and in vivo to hydrolyze the 5' phosphate from phosphatidylinositol-3,4,5-trisphosphate (PI-3,4,5-P3). Thus SHIP, and its more widely expressed counterpart, SHIP2, could play a central role in determining PI-3,4,5-P3 and PI-3,4-P2 levels in many cell types. To explore the in vivo function of SHIP further we recently generated a SHIP knock out mouse and in this review we discuss experiments carried out with bone marrow derived mast cells (BMMCs) from these animals.

Animals↗
PubMed1999

The increase in the steady-state level of major histocompatibility complex mRNA in the host peripheral T lymphocytes due to ischaemia-reperfusion injury.

In our previous study, using a swine model of single lung transplantation, a relationship between the level of major histocompatibility complex (MHC II) expression on host T lymphocytes and the extent of the ex vivo preservation time was observed. Furthermore, a model of ischaemia by simple cross-clamping proved MHC II up-regulation to be independent of tissue incompatibility. The mechanism through which ischaemia-reperfusion injury (IRI) induces MHC up-regulation in host peripheral T cells has not been reported. The objective of this study was to determine whether IRI induces MHC II up-regulation in T cells by altering the intracellular steady-state level of MHC II mRNA. Group A (seven donors, seven recipients) was an allotransplantation model of 15 h of cold storage (4 degrees C) while in group B (n = 6) animals underwent 2 h of warm ischaemia. Group C (n = 6) underwent sham operation. For quantification of mRNA extracted from peripheral T lymphocytes isolated before and after surgery, semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) was used to determine the time at which mRNA levels reached its peak. The mRNA at pre-reperfusion and the time, at which mRNA peaked, was used for competitive RT-PCR. The results of RT-PCR analyses demonstrated that IRI induced an increase in the steady-state level of MHC II mRNA (p < 0.02) within 2 h post-reperfusion, irrespective of type of ischaemia and tissue incompatibility. In conclusion, this study suggested that IRI up-regulates the MHC II expression in peripheral T cells by altering the intracellular steady-state level of MHC II-DR-beta.

Animals↗
PubMed1999

Platelet-activating factor plays a role in the mechanism of major histocompatibility complex in T lymphocytes.

In recent studies, using a swine model of single lung transplantation, we demonstrated that IRI alone increased MHC II expression in the host's peripheral T lymphocytes. The inhibition of increased MHC II expression with TCV-309, a specific platelet-activating factor (PAF) antagonist suggested that PAF might play a role in the mechanism of increased MHC II expression. The purpose of the current study was two fold: 1) to investigate the mechanism of PAF-induced increased expression of MHC II in T lymphocytes, 2) to determine whether a specific PAF-antagonist, TCV-309, is capable of inhibiting the increased expression in an in vitro system. This study was subdivided, using four in vitro conditions: 1) purified resting T cells, 2) purified proliferating T cells, 3) PBL treated with PAF, and 4) PBL preincubated with TCV-309 and treated with PAF. The level of MHC II on T cells were measured by two color flow cytometry analysis (swine anti-CD3, MHC II-DR-(beta)antibodies). Both MHC II intensity and the number of CD3+MHC+ T cells did not change in resting purified T cells once treated with PAF, Furthermore, MHC II intensity did not change in purified proliferating T cells treated with PAF. The number of CD3+MHC+ T cells, however, increased significantly (p<0.05) from day 1 to day 4 as compared with pre-treatment value (day 0) for purified proliferating T cells. Treatment of PBL with PAF (10(-7)M) resulted in a significant (p<0.05) increase in MHC II expression from day 2 to day 4 post-treatment. The number of CD3+MHC+ T cells in PBL, however, did not change significantly upon treatment with PAF. The results of this study indicated that PAF did not have a direct effect on increased MHC II expression in resting or proliferating purified T lymphocytes. However, the mechanism of PAF-induced increased expression of MHC II in T cells may be via an indirect pathway involving accessory cells. TCV-309, a specific PAF receptor antagonist, is capable of inhibiting this PAF-induced increased expression of MHC II in T cells.

Animals↗
PubMed1998

Targeted disruption of SHIP leads to Steel factor-induced degranulation of mast cells.

To investigate the role of the src homology 2 (SH2)-containing inositol 5' phosphatase (SHIP) in growth factor-mediated signalling, we compared Steel factor (SF)-induced events in bone marrow-derived mast cells (BMMCs) from SHIP-/- and SHIP+/+ littermates. We found SF alone stimulated massive degranulation from SHIP-/- but none from SHIP+/+ BMMCs. This SF-induced degranulation, which was not due to higher c-kit levels in SHIP-/- cells, correlated with higher intracellular calcium than that in SHIP+/+ cells and was dependent on the influx of extracellular calcium. Both this influx and subsequent degranulation were completely inhibited by PI-3-kinase inhibitors, indicating that SF-induced activation of PI-3-kinase was upstream of extracellular calcium entry. A comparison of phosphatidylinositol-3,4,5-trisphosphate (PIP3) levels following SF stimulation of SHIP+/+ and SHIP-/- BMMCs suggested that SHIP restricted this entry by hydrolyzing PIP3. Although PI-3-kinase inhibitors blocked the release of intracellular calcium, implicating PIP3, and PLCgamma-2 was slightly more tyrosine phosphorylated in SHIP-/- cells, the increase in inositol-1,4,5-trisphosphate (IP3) and intracellular calcium levels were identical in SHIP-/- and SHIP+/+ BMMCs. These results suggest that SHIP prevents SF from triggering degranulation of normal BMMCs, and does so by hydrolyzing PIP3, which in turn limits extracellular calcium entry at a step after the release of intracellular calcium.

Animals↗
PubMed1998

Dissociation of cytokine-induced phosphorylation of Bad and activation of PKB/akt: involvement of MEK upstream of Bad phosphorylation.

The phosphatidylinositol 3-kinase (PI3K)-signaling pathway has emerged as an important component of cytokine-mediated survival of hemopoietic cells. Recently, the protein kinase PKB/akt (referred to here as PKB) has been identified as a downstream target of PI3K necessary for survival. PKB has also been implicated in the phosphorylation of Bad, potentially linking the survival effects of cytokines with the Bcl-2 family. We have shown that granulocyte/macrophage colony-stimulating factor (GM-CSF) maintains survival in the absence of PI3K activity, and we now show that when PKB activation is also completely blocked, GM-CSF is still able to stimulate phosphorylation of Bad. Interleukin 3 (IL-3), on the other hand, requires PI3K for survival, and blocking PI3K partially inhibited Bad phosphorylation. IL-4, unique among the cytokines in that it lacks the ability to activate the p21ras-mitogen-activated protein kinase (MAPK) cascade, was found to activate PKB and promote cell survival, but it did not stimulate Bad phosphorylation. Finally, although our data suggest that the MAPK pathway is not required for inhibition of apoptosis, we provide evidence that phosphorylation of Bad may be occurring via a MAPK/ERK kinase (MEK)-dependent pathway. Together, these results demonstrate that although PI3K may contribute to phosphorylation of Bad in some instances, there is at least one other PI3K-independent pathway involved, possibly via activation of MEK. Our data also suggest that although phosphorylation of Bad may be one means by which cytokines can inhibit apoptosis, it may be neither sufficient nor necessary for the survival effect.

Apoptosis↗
PubMed1998

The antineoplastic ether lipid, s-phosphonate, selectively induces apoptosis in human leukemic cells and exhibits antiangiogenic and apoptotic activity on the chorioallantoic membrane of the chick embryo.

INTRODUCTION: We investigated the cytotoxic and antiangiogenic activity of the ether lipid, 2'-(trimethylammonio)ethyl 4-(hexadecyloxy)-3(S)-methoxybutane-phosphonate (termed s-phosphonate). METHOD: Cytotoxicity was determined using an XTT bioassay. Apoptosis was measured by either DNA fragmentation or immunolabelling techniques. Angiogenesis was measured using the in vivo chorioallantoic membrane (CAM) of the chick embryo. RESULTS: S-phosphonate was selectively cytotoxic towards the human leukemic cell lines, HL-60 and AML-14, whereas leukemic K-562 cells and the murine mast cell line, MC-9, were resistant to this agent at concentrations as high as 50 microM. This selectivity resulted from the induction of apoptosis (or programmed cell death) by s-phosphonate in HL-60 and AML-14 cells but not in resistant K-562 or MC-9 cells. S-phosphonate induced localized antiangiogenic effects and membrane thinning in the CAM. This concentration-dependent antiangiogenic effect was associated with apoptosis in the CAM as measured by DNA fragmentation in extracted CAM tissue. The localized areas of membrane thinning and antiangiogenesis on the CAM caused by s-phosphonate were also the only areas of the membrane in which apoptosis occurred. CONCLUSION: We conclude that s-phosphonate selectively induces apoptosis in human leukemic cells and exhibits antiangiogenic and apoptotic activity on the CAM.

Animals↗
PubMed1998

Downstream signalling events regulated by phosphatidylinositol 3-kinase activity.

The phosphatidylinositol (PI) 3-kinase family of enzymes is now known to be regulated by several different upstream pathways in response to virtually all growth factors and cytokines. In the past few years, the phosphoinositides phosphorylated at the 3-OH position of the inositol ring have been shown to be lipid second messengers that may directly or indirectly regulate the activity of several different serine/threonine kinases. Consistent with the many different cellular events in which PI 3-kinase plays an important role, a diverse group of serine/threonine kinases are regulated downstream of PI 3-kinases, including protein kinase C (PKC) isoforms, p70 S6 kinase, and PKB/Akt. This review summarises studies done primarily in the past few years that have begun to unravel these targets of PI 3-kinase activity.

Animals↗
PubMed1998

Phosphatidylinositol 3-kinase: increased activity and protein level in amyotrophic lateral sclerosis.

Enzyme activities and protein levels of several protein and lipid kinases were measured in postmortem tissue from patients who died with amyotrophic lateral sclerosis (ALS) as well as from control subjects. Patients who died with ALS had increased activities and protein levels of phosphatidylinositol 3-kinase (PI 3-K) in particulate fractions of spinal cord tissue compared with control subjects. The PI 3-K activity increased with PI 3-K protein level, indicating no change in specific PI 3-K activity in ALS. No differences in PI 3-K activities were found in cytosolic fractions of spinal cord, or in motor and visual cortices, from ALS patients compared with those from controls. PI 3-K activities and protein levels were unchanged in brain tissue from patients who died with Alzheimer's disease compared with those from controls. PI 3-K is a lipid kinase that is important for cell survival and is activated in response to many growth factors. Increased PI 3-K activities in particulate fractions of spinal cord from ALS patients may be related to the increase of PI 3-K protein levels found in this tissue. The protein kinases Erk2, protein kinase B (PKB), and p70 ribosomal S6 kinase (S6K) showed no differences in activities in spinal cord tissue between ALS patients and controls. However, the amounts of PKB and S6K protein were significantly higher in ALS patients, whereas Erk2 protein amount was unchanged compared with controls. Protein kinase C activity was increased in spinal cord tissue from ALS patients, which is consistent with our previous report. The increased activity of PI 3-K in spinal cord tissue from patients with ALS implicates the involvement or activation of PI 3-K in ALS, as either a cause or a consequence of the neuron loss. The lack of up-regulation in the activities of PKB and S6K in ALS tissue supports an impairment in signal transduction cascades mediated by PI 3-K in this neurodegenerative disease.

Aged↗
PubMed1997

Lack of correlation between growth of TF-1 cells and tyrosine phosphorylation signals in response to IL-3, IL-5 and GM-CSF.

The human cell line, TF-1, was used to compare responses to interleukin 3 (IL-3), IL-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF). TF-1 cells grew well in the presence of any one of the cytokines in early passages. However, the level of tyrosine phosphorylation was minimal in response to IL-5, and detection of a tyrosine phosphorylation signal required high concentrations of IL-5. When grown for longer periods of time in the presence of one of the cytokines, there were dramatic difference in the cells' responses. IL-3 or GM-CSF-grown cells showed only half of the original bioassay response to IL-5. However, cells grown in IL-5 alone kept the same response, and all cells showed the same response to IL-3 and GM-CSF. IL-5-grown cells also had an increased tyrosine phosphorylation signal, along with increased sensitivity to IL-5, yet there was no difference in an IL-5 bioassay. The relative level of detection of tyrosine phosphorylated JAK-2, STAT-5, SHC, and other substrates corresponded to the overall tyrosine phosphorylation signal. IL-5-grown cells had approximately 10-fold more IL-5 receptor alpha subunit message compared to IL-3-grown. These results suggest that response of TF-1 cells to IL-5 may be deceiving in that a good response in a bioassay can be observed with relatively little tyrosine phosphorylation, but an increase in tyrosine phosphorylation can be correlated with an increase in the expression of IL-5 receptor alpha subunit.

Cell Division↗
PubMed1997

The involvement of phosphatidylinositol 3-kinase in crystal induced human neutrophil activation.

OBJECTIVE: We investigated whether phosphatidylinositol (PI) 3-kinase is involved in the signal transduction pathway leading to neutrophil activation by inflammatory microcrystals. METHODS: Neutrophil chemiluminescence and degranulation responses to opsonized crystals were measured in the presence of selective inhibitors known to inhibit PI 3-kinase activity in neutrophils. RESULTS: Wortmannin and LY 294002, 2 selective inhibitors of PI 3-kinase, were shown to inhibit neutrophil activation induced by plasma opsonized crystals of calcium pyrophosphate dihydrate (CPPD) [both monoclinic (M) and triclinic (T) forms] and monosodium urate monohydrate (MSUM). IC50 for wortmannin or LY 294002 inhibition of crystal induced respiratory burst (measured by chemiluminescence) was about 3 nM and 0.3 microM, respectively, proving the pivotal role of PI 3-kinase in neutrophil respiratory burst activation by all 3 crystals. Degranulation responses of neutrophils to CPPD(M) and CPPD(T) crystals were also inhibited by about 50% by wortmannin in the 10 to 20 nM concentration range, supporting the direct involvement of PI 3-kinase in signal transduction pathways leading to crystal induced neutrophil degranulation. All 3 crystals induced the activation of PI 3-kinase in neutrophils as measured by the increased PI 3-kinase activity associated with immunoprecipitated tyrosine phosphorylated proteins from 1 min crystal-neutrophil incubations. Neutrophils pretreated with wortmannin at 10 nM showed sub-basal levels of PI 3-kinase activity at all time points measured. CONCLUSION: PI 3-kinase plays a central role in the signal transduction pathways leading to respiratory burst and degranulation responses in neutrophils activated by inflammatory microcrystals.

Androstadienes↗
PubMed1996

Phosphatidylinositol 3-OH kinase activity is not required for activation of mitogen-activated protein kinase by cytokines.

Hemopoietic cells respond to cytokines by initiating tyrosine phosphorylation of receptors and receptor-associated proteins, leading to the activation of numerous cytosolic and membrane associated enzymes, including phosphatidylinositol 3-OH kinase (PI 3-kinase). Recent reports have suggested that PI 3-kinase may serve as an upstream activator of mitogen-activated protein (MAP) kinase. After stimulation with interleukin-3 and granulocyte-macrophage colony-stimulating factor, we show here that inhibition of MAP kinase activity by two inhibitors of PI 3-kinase, wortmannin and LY-294002, does not correlate with their ability to inhibit PI 3-kinase or p70 S6 kinase phosphorylation. Complete inhibition of phosphatidylinositol 3,4,5-trisphosphate production occurred at approximately 100 nM WM or 25 microM LY-294002, but at these concentrations, WM significantly inhibited MAP kinase activation, while LY-294002 had virtually no effect on MAP kinase activity. Furthermore, WM does not inhibit phorbol ester-mediated MAP kinase activation, but LY-294002 does. Together these results suggest WM and LY-294002 are differentially inhibiting enzymes other than PI 3-kinase that function upstream of MAP kinase.

Androstadienes↗
PubMed1996

Protein kinase C delta specifically associates with phosphatidylinositol 3-kinase following cytokine stimulation.

Phosphatidylinositol (PI) 3-kinase is activated as a result of cytokine-induced association of the enzyme with specific tyrosine-phosphorylated proteins. PI 3-kinase lipid products, PI 3, 4-P2 and PI 3,4,5-P3, have been shown, in vitro, to directly activate novel and atypical protein kinase C (PKC) isozymes. However, the mechanism by which PI 3-kinase may be involved in regulation of PKC isoforms in vivo is presently unknown. We investigated a possible relationship by looking for associations between these enzymes. We found that in a human erythroleukemia cell line, as well as in rabbit platelets, PI 3-kinase and PKCdelta associate in a specific manner that is modulated by cell activation. Granulocyte-macrophage colony-stimulating factor treatment of cells caused increased association of PKCdelta and PI 3-kinase as did treatment of platelets with platelet-activating factor. Results using two PI 3-kinase inhibitors, wortmannin and LY-294002, showed that the former inhibited this association, while the latter did not, suggesting that PI 3-kinase lipid products may not be a prerequisite for the PI 3-kinase/PKCdelta association. Our results also suggest that tyrosine phosphorylation of PKCdelta is not involved in its association with PI 3-kinase.

Androstadienes↗
PubMed1996

Genetic basis of hypo-responsiveness of A/J mice to interleukin-3.

Hematopoietic progenitor cells of the A/J strain of mice show a pronounced defect in the ability to form colonies or proliferate in response to interleukin-3 (IL-3). Comparison of immunoblots of A/J mast cells and of mast cells from the C57BL/6 strain that respond normally to IL-3 showed that, in both strains, a 125-kD band of the expected size was recognized by an antibody against the beta chain of the IL-3 receptor, the AIC2A molecule. However, in the C57BL/6 cells, there was an additional 110-kD species not seen in cells of the A/J strain. Analyses using bone marrow-derived mast cells from a panel of A/J x C57BL/6 and A/J x C57BL/6 recombinant inbred (RI) mice showed that the hypo-responsiveness to IL-3 is governed by a single gene. However, the absence of this 110-kD species in the A/J strain did not co-map with IL-3 hypo-responsiveness but did indeed map to the AIC2A genetic locus. These data show that this trait in the A/J strain was due to a polymorphism of the AIC2A gene unrelated to IL-3 hypo-responsiveness. Typing of the RI strains for the markers D14Mit98, D14Mitl4, and D14Mit133 mapped the locus determining hypo-responsiveness to IL-3 to the subtelomeric region of chromosome 14, the region that also bears the gene encoding the alpha chain of the IL-3 receptor (lL-3Ralpha). Immunofluorescence analyses indicated that IL-3Ralpha protein was undetectable on fresh bone marrow cells from A/J mice, although clearly detectable on cells from the responder C57BL/6 strain. However, IL-3Ralpha was readily detectable at normal levels on A/J mast cells generated by culture of A/J bone marrow cells in a combination of IL-3 and steel factor. Moreover, IL-3Ralpha on these A/J mast cells appears to be functional in that IL-3 stimulation of these cells results in tyrosine phosphorylation events characteristic of IL-3 signaling, including tyrosine phosphorylation of the beta chain of the IL-3 receptor, Jak-2 kinase, and SHPTP2. Collectively, these data indicate that the hypo-responsiveness of A/J mice to IL-3 is due to a defect in the gene encoding IL-3Ralpha and that, although this defect gives rise to reduced expression of alpha chain on primary bone marrow cells, this defect is not absolute and that, under certain circumstances, A/J cells can express functional receptors.

Animals↗
PubMed1996

Role of p70 S6 kinase in cytokine-regulated hemopoietic cell survival.

The signalling mechanisms required for cell survival remain relatively undefined. We and others have shown that phosphatidylinositol 3-kinase (PI 3-kinase) is an important enzyme in the prevention of apoptosis, and this property is independent of p21ras-MAP kinase activation. It is therefore important to define the downstream targets of this enzyme mediating the inhibition of apoptosis. We report here than p70 S6 kinase, a protein critical for progression through the cell cycle and a downstream effector of PI 3-kinase, is not required for the survival of cytokine-stimulated human T-cells or murine mast cells. The potent inhibitor of p70 S6 kinase activation, rapamycin, was unable to induce apoptosis in cells stimulated with cytokines. As well, PI 3-kinase inhibitors that also blocked the activation of p70 S6 kinase were able to induce apoptosis. These studies, therefore, describe a bifurcation of signalling pathways from PI 3-kinase leading to different physiological outcomes.

Animals↗
PubMed1995

Role of phosphatidylinositol 3-OH-kinase activity in the inhibition of apoptosis in haemopoietic cells: phosphatidylinositol 3-OH-kinase inhibitors reveal a difference in signalling between interleukin-3 and granulocyte-macrophage colony stimulating factor.

Apoptosis of haemopoietic cells can be inhibited by various cytokines, but the specific signalling pathways involved are not well defined. Interleukin (IL)-4 has unique actions since it is unable to activate p21ras or mitogen-activated protein kinase, but can activate PtdIns 3-OH-kinase (PtdIns 3-kinase), the latter effect being shared with most other cytokines. In many cases, IL-4 is able to maintain cell viability by inhibiting apoptosis, but is unable to stimulate continuous proliferation of cells. This led us to investigate the role of PtdIns 3-kinase in inhibition of apoptosis. Two potent inhibitors of PtdIns 3-kinase, wortmannin and LY294002, rapidly induced apoptosis in cells incubated in the presence of IL-4, at concentrations consistent with their ability to inhibit PtdIns 3-kinase activity in whole cells. Interestingly, the same effect was seen in cells in the presence of IL-3 and Steel factor, while cells incubated in the presence of granulocyte-macrophage colony stimulating factor, and to a lesser extent, IL-5 could bypass the effect of wortmannin or LY294002. Therefore, this study suggests that PtdIns 3-kinase activity provides an important, although not a unique signal, required to inhibit apoptosis in haemopoietic cells.

Androstadienes↗