Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of Taxol-induced apoptosis was investigated in MCF-7 human breast carcinoma cells. Taxol-induced apoptosis was associated with phosphorylation of both c-Raf-1 and Bcl-2 and activation of ERK and JNK MAP kinases. The serine protease inhibitor N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) effectively blocked apoptosis, but N-p-tosyl-L-lysine chloromethyl ketone (TLCK), another serine protease inhibitor, was without effect. TPCK treatment also prevented phosphorylation of c-Raf-1 and Bcl-2 in response to Taxol treatment. The serine protease inhibitor did not alter JNK activity, but it enhanced Taxol-induced activation of ERK1/2. Treatment of cells with the inhibitor of MEK activation, PD98059, prevented Taxol-induced ERK activation both in the presence and absence of TPCK, but did not influence survival of either Taxol- or Taxol plus TPCK-treated cells. In addition, PD98059 had no effect on c-Raf-1 or Bcl-2 phosphorylation. Thus, while the Taxol-induced phosphorylations of c-Raf-1 and Bcl-2 proteins appear to be coupled, these events can be disassociated from ERK1/2 activation. In summary, these findings suggest that phosphorylation of c-Raf-1 and Bcl-2, but not ERK1/2, are important signaling events in Taxol-induced apoptosis of MCF-7 breast cancer cells and that a TPCK inhibitable protease(s) is required for these processes.
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PMID:Serine protease inhibitor TPCK prevents Taxol-induced cell death and blocks c-Raf-1 and Bcl-2 phosphorylation in human breast carcinoma cells. 1037 21

Raf-1 activation and Bcl-2 hyperphosphorylation following treatment with paclitaxel (Taxol) or other microtubule-active drugs is associated with mitotic arrest. Here we show that microtubule-active drugs do not activate the mitogen-activated protein kinase (MAPK) pathway in leukemia cells. PD98059, a MEK inhibitor, and SB202190, a p38 MAP kinase inhibitor, do not abrogate Bcl-2 phosphorylation nor apoptosis. Simultaneously with PARP cleavage, paclitaxel induces cleavage of Bcl-2 protein yielding a potentially pro-apoptotic 22 kDa product. In comparison, the stimulation of Raf-1 by phorbol ester (TPA) activates the MAPK pathway, causes MAPK-dependent p21WAF1/CIP1 induction, Rb dephosphorylation and growth arrest without Bcl-2 phosphorylation or apoptosis. Like TPA, cAMP induces p21WAF1/CIP1 but does not cause Bcl-2 phosphorylation. MEKK1 and Ras, upstream activators of JNK and ERK MAPK, also fail to induce Bcl-2 hyperphosphorylation. Although Lck tyrosine kinase has been recently implicated in Raf-1 activation during mitotic arrest, microtubule-active drugs induce Raf-1/Bcl-2 hyperphosphorylation and apoptosis in a Lck-deficient Jurkat cells. Therefore, microtubule-active drugs induce apoptosis which is associated with Raf-1 and Bcl-2 phosphorylation and Bcl-2 cleavage but is independent of the MAPK pathway. In contrast, TPA-activated MAPK pathway causes p21WAF1/CIP1-dependent growth arrest without apoptosis.
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PMID:Mitogen-activated protein kinase pathway is dispensable for microtubule-active drug-induced Raf-1/Bcl-2 phosphorylation and apoptosis in leukemia cells. 1040 Apr 18

Gas6 is a growth factor membrane of the vitamin K-dependent family of proteins which is preferentially expressed in quiescent cells. Gas6 was identified as the ligand for Axl tyrosine kinase receptor family. Consistent with this, Gas6 was previously reported to induce cell cycle re-entry of serum-starved NIH3T3 cells and to prevent cell death after complete growth factor withdrawal, the survival effect being uncoupled from Gas6-induced mitogenesis. We have previously demonstrated that both Gas6 mitogenic and survival effects are mediated by Src and the phosphatidylinositol3-OH kinase (PI3K). Here we report that Ras is required for Gas6 mitogenesis but is dispensable for its survival effect. Gas6-induced survival requires the activity of the small GTPases of the Rho family, Rac and Rho, together with the downstream kinase Pak. Overexpression of the respective dominant negative constructs abrogates Gas6-mediated survival functions. Addition of Gas6 to serum starved cells results in the activation of AKT/PKB and in the phosphorylation of the Bcl-2 family member, Bad. By ectopic expression of a catalytically inactive form of AKT/PKB, we demonstrate that AKT/PKB is necessary for Gas6-mediated survival functions. We further show evidence that Gas6 stimulation of serum starved NIH3T3 cells results in a transient ERK, JNK/SAPK and p38 MAPK activation. Blocking ERK activation did not influence Gas6-induced survival, suggesting that such pathway is not involved in Gas6 protection from cell death. On the contrary we found that the late constitutive increase of p38 MAPK activity associated with cell death was downregulated in Gas6-treated NIH3T3 cells thus suggesting that Gas6 might promote survival by interfering with this pathway. Taken together the evidence here provided identity elements involved in Gas6 signalling more specifically elucidating the pathway responsible for Gas6-induced cell survival under conditions that do not allow cell proliferation.
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PMID:Gas6-mediated survival in NIH3T3 cells activates stress signalling cascade and is independent of Ras. 1043 35

Over the past decade, the involvement of tyrosine kinases in signal transduction pathways evoked by cytokines has been intensively investigated. Only relatively recently have the roles of serine/threonine kinases in cytokine-induced signal transduction and anti-apoptotic pathways been examined. Cytokine receptors without intrinsic kinase activity such as interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF) and the interferons were thought to transmit their regulatory signals primarily by the receptor-associated Jak family of tyrosine kinases. This family of tyrosine kinases activates STAT transcription factors, which subsequently transduced their signals into the nucleus to modulate gene expression. Cytokine receptors with intrinsic tyrosine kinase activity such as c-Kit were initially thought to transduce their signals independently of serine/threonine kinase cascades. Recently, both of these types of receptor signaling pathways have been shown to interact with serine/threonine kinase pathways as maximal activation of these tyrosine kinase regulated cascades involve serine/threonine phosphorylation modulated by, for example MAP kinases. A common intermediate pathway initiating from cytokine receptors is the Ras/Raf/MEK/ERK (MAPK) cascade, which can result in the phosphorylation and activation of additional downstream kinases and transcription factors such as p90Rsk, CREB, Elk and Egr-1. Serine/threonine phosphorylation is also involved in the regulation of the apoptosis-controlling Bcl-2 protein, as certain phosphorylation events induced by cytokines such as IL-3 are anti-apoptotic, whereas other phosphorylation events triggered by chemotherapeutic drugs such as Paclitaxel are associated with cell death. Serine/threonine phosphorylation is implicated in the etiology of certain human cancers as constitutive serine phosphorylation of STATs 1 and 3 is observed in chronic lymphocytic leukemia and can be inhibited by the chemotherapeutic drug fludarabine. Serine/threonine phosphorylation also plays a role in the etiology of immunodeficiencies. Activated STAT5 proteins are detected in reduced levels in lymphocytes recovered from HIV-infected individuals and immunocompromised mice. Serine/threonine phosphorylation may be an important target of certain chemotherapeutic drugs which recognize the activated proteins. This meeting report and mini-review will discuss the interactions of serine/threonine kinases with signal transduction and apoptotic molecules and how some of these pathways can be controlled by chemotherapeutic drugs. Leukemia (2000) 14, 9-21.
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PMID:Serine/threonine phosphorylation in cytokine signal transduction. 1063 71

Motoneurons require neurotrophic factors for their survival and axonal projection during development, as well as nerve regeneration. By using the axotomy-induced neuronal death paradigm and adenovirus-mediated gene transfer, we attempted to gain insight into the functional significances of major growth factor receptor downstream cascades, Ras-extracellular signal-regulated kinase (Ras-ERK) pathway and phosphatidylinositol-3 kinase-Akt (PI3K-Akt) pathway. After neonatal hypoglossal nerve transection, the constitutively active Akt-overexpressing neurons could survive as well as those overexpressing Bcl-2, whereas the constitutively active ERK kinase (MEK)-overexpressing ones failed to survive. A dominant negative Akt experiment demonstrated that inhibition of Akt pathway hastened axotomy-induced neuronal death in the neonate. In addition, the dominant active Akt-overexpressing adult hypoglossal neurons showed accelerated axonal regeneration after axotomy. These results suggest that Akt plays dual roles in motoneuronal survival and nerve regeneration in vivo and that PI3K-Akt pathway is probably more vital in neuronal survival after injury than Ras-ERK pathway.
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PMID:Akt/protein kinase B prevents injury-induced motoneuron death and accelerates axonal regeneration. 1075 40

Drug resistance remains a serious limiting factor in the treatment of acute myeloid leukaemia (AML) either at initial presentation or following primary or subsequent relapses. Using specific kinase inhibitors, this study has investigated the contribution of the Ras/PI3-kinase regulated survival pathways to drug resistance and suppression of apoptosis in a cell line derived from AML (HL60). Inhibition of the Raf/MAP-kinase (ERK) pathway with a specific MAP-kinase inhibitor, apigenin did not sensitise HL60 cells to drug-induced apoptosis, indicating a lack of involvement in chemoresistance. In contrast, the PI3-kinase inhibitors, LY294002 and wortmannin, did induce a significant increase in apoptosis in combination with cytotoxic drugs. The contribution of downstream mediators of PI3-kinase, p70S6-kinase and PKB/Akt were then investigated. While inhibition of p70S6-kinase with rapamycin did not increase drug-induced apoptosis, PI3-kinase inhibition resulted in notable dephosphorylation of PKB, suggesting that the PI3-kinase/PKB survival pathway may play a major role in chemoresistance in AML. This pathway has been reported to mediate heterodimer interactions with the proapoptotic regulator, Bad. In contrast to previous studies, we found no evidence of Bad binding to anti-apoptotic Bcl-2, Bcl-XL or McI-1, or of alterations in Bax heterodimers. This suggests that alternative targets of PI3-kinase/PKB, distinct from the Bcl-2 family may be responsible for contributing to survival factor-mediated drug resistance in AML.
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PMID:Sensitisation of HL60 human leukaemic cells to cytotoxic drug-induced apoptosis by inhibition of PI3-kinase survival signals. 1076 45

The appearance of blasts in acute myeloid leukemia (AML) reflects a shift from cellular processes inducing maturation and cell death to those favouring survival and accumulation. We have monitored changes in the growth factor signalling molecule MAPKinase, in the cytoprotective protein Bcl-2 and in the cell death protein Bax, during maturation of proliferating and non-proliferating AML blasts in vitro. Eighteen AML samples were cultured for 7 d in serum-free medium with or without a supplement of recombinant cytokines comprising c-kit ligand, IL3 and GMCSF. Maturation of AML blasts, as assessed by morphology on Romanowsky-stained slides of 7/18 samples and by changes in surface CD markers on all 18 leukemias, occurred in both the absence and presence of cytokines. Cell numbers decreased to a mean of 71% after 7 d of cytokine-free culture, but increased to 210% in cytokine-supplemented cultures. The proportion of CD15-positive cells, assessed by flow cytometry, increased over 7 d in 17/18 samples, from a mean of 22% to 68% in cytokine-free cultures and to 72% in cytokine-supplemented cultures (p = < 0.0001 for both). By immunofluorescence/flow cytometry, there was no significant change in Bcl-2 over 7 d of culture, while Bax increased, particularly in cytokine-free cultures (2.2-fold), which led to a significant decrease in the Bcl-2/Bax ratio. Immunoblotting demonstrated that ERK was briefly phosphorylated after seeding AML blasts into culture. PD98059, an inhibitor of MAPKinase kinase (MEK) which activates MAPKinase, inhibited this transient ERK phosphorylation but was unable to block maturation as measured by acquisition of CD15 in samples from 12 patients with low starting numbers of CD15-positive cells. PD98059, however, reduced cell numbers in 7-d liquid culture and, in cytokine-supplemented cultures, this was associated with a 1.3-fold increase in Bcl-2 (p = 0.012) and a 1.4-fold increase in Bax (p = 0.02). Overall, these data demonstrate that most leukemic populations can partially differentiate in vitro without the need for cytokines or inducers. The MAPKinase pathway is not required for this maturation, but it does maintain cell viability in the absence or presence of cytokines. A rise in Bcl-2 may not protect AML blasts in the face of elevated Bax.
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PMID:The MEK inhibitor, PD98059, reduces survival but does not block acute myeloid leukemia blast maturation in vitro. 1077 91

Microtubule-damaging agents arrest cells at G(2)/M and induce apoptosis in association with phosphorylation of the anti-apoptotic proteins Bcl-2 and Bcl-X(L). Because microtubule inhibitors activate JNK, we sought to determine whether JNK was responsible for Bcl-2/Bcl-X(L) phosphorylation in KB-3 cells treated with vinblastine. Two major endogenous forms of JNK, p46(JNK1) and p54(JNK2), were present in KB-3 cells, and both isoforms were activated by vinblastine as determined by Mono Q chromatography. We used antisense oligonucleotides (AS) to specifically inhibit their expression. A combination of AS-JNK1 with AS-JNK2 inhibited by 80% vinblastine-induced phosphorylation of two known JNK substrates, c-Jun and ATF-2. In addition, AS-JNK1/2 inhibited vinblastine-induced phosphorylation of Bcl-2 by 85% and that of Bcl-X(L) by 65%. Stable expression of the JNK scaffold protein JIP-1 blocked vinblastine-induced phosphorylation of c-Jun and ATF-2, but did not affect Bcl-2/Bcl-X(L) phosphorylation, confirming a bifurcation in JNK signaling involving both nuclear and non-nuclear substrates. Vinblastine-induced phosphorylation of Raf-1 was unaffected by AS-JNK1/2 and was associated with loss of activity for MEK substrate in vitro and inactivation of ERK in vivo. These results provide evidence for a direct role of the JNK pathway in apoptotic regulation through Bcl-2/Bcl-X(L) phosphorylation.
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PMID:Vinblastine-induced phosphorylation of Bcl-2 and Bcl-XL is mediated by JNK and occurs in parallel with inactivation of the Raf-1/MEK/ERK cascade. 1091 35

A number of oncogenes alter the regulation of the cell cycle and cell death, contributing to the altered growth of tumours. Expression of the v-Src oncoprotein in Rat-1 fibroblasts prevented cell cycle exit in response to growth factor withdrawal. Here we investigated whether survival of v-Src transformed cells in low serum is dependent on v-Src activity. We used a temperature sensitive v-Src to study the effect inactivating v-Src on transformed cells growing under low serum conditions. We found when we switched off v-Src the cells died by apoptosis characterised by activation of caspases and the stress-activated kinases, JNK (Jun N-terminal kinase) and p38 MAP (mitogen activated protein) kinase. We were able to prevent cell death by addition of serum or overexpression of Bcl-2. Thus v-Src transformed Rat-1 cells can be protected from apoptosis by serum, v-Src, or Bcl-2. We investigated how v-Src protects from apoptosis under these conditions. Amongst other effects, v-Src activates two kinases which have been shown to protect cells from apoptosis, phosphatidylinositol 3-kinase (PI3-K) and extracellular signal-regulated kinase (ERK1/2). We found that switching off v-Src led to a decrease in the activity of both PI3-K and ERK1/2, however, we found that adding a specific inhibitor of PI3-K (LY294002) to v-Src transformed Rat-1 cells grown in low serum induced apoptosis while a specific ERK kinase (MEK1) inhibitor (PD98059) had no effect. This suggests that v-Src protects from apoptosis under low serum conditions by activating PI3-K.
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PMID:Regulation of both apoptosis and cell survival by the v-Src oncoprotein. 1091 42

Bcl-2 overexpression prevents neuronal death after injury or neurotrophic factor-deprivation but the biochemical consequences of survival maintenance by Bcl-2 have hardly been explored. We show that unlike NGF, adenovirally delivered hBcl-2 supports the survival of over 80% of the neurons without activating ERK and Akt phosphorylation, or suppressing JNK phosphorylation, or enhancing cell growth. However, the proapoptotic protein BAD, whose phosphorylation is induced by NGF, is degraded in NGF-deprived neurons expressing hBcl-2, while the level of Bcl-xL remains unaffected. Interestingly, degradation of BAD protein is prevented by the pan-caspase inhibitor Boc.Asp(OMe)fmk. We propose that NGF-deprivation promotes dephosphorylation of BAD while hBcl-2 facilitates its release into the cytoplasm where it is degraded by noncaspase, Boc.Asp(O-Me)fmk-inhibitable proteases. The potential importance of BAD degradation is suggested by our finding that overexpressed BAD kills NGF-maintained sympathetic neurons by apoptosis, while hBcl-2 prevents BAD-induced death.
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PMID:The combination of bcl-2 expression and NGF-deprivation facilitates the selective destruction of BAD protein in living sympathetic neurons. 1092 54


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