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)

Sphingolipids are putative intracellular signal mediators in cell differentiation, growth inhibition, and apoptosis. Sphingosine, sphinganine, and phytosphingosine are structural analogs of sphingolipids and are classified as long-chain sphingoid bases. Sphingosine and sphinganine are known to play important roles in apoptosis. In the present study, we examined the phytosphingosine-induced apoptosis mechanism, focusing on mitochondria in human T-cell lymphoma Jurkat cells. Phytosphingosine significantly induced chromatin DNA fragmentation, which is a hallmark of apoptosis. Enzymatic activity measurements of caspases revealed that caspase-3 and caspase-9 are activated in phytosphingosine-induced apoptosis, but there is little activation of caspase-8 suggesting that phytosphingosine influences mitochondrial functions. In agreement with this hypothesis, a decrease in DeltaPsi(m) and the release of cytochrome c to the cytosol were observed upon phytosphingosine treatment. Furthermore, overexpression of mitochondria-localized anti-apoptotic protein Bcl-2 prevented phytosphingosine apoptotic stimuli. Western blot assays revealed that phytosphingosine decreases phosphorylated Akt and p70S6k. Dephosphorylation of Akt was partially inhibited by protein phosphatase inhibitor OA and OA attenuated phytosphingosine-induced apoptosis. Moreover, using a cell-free system, phytosphingosine directly reduced DeltaPsi(m). These results indicate that phytosphingosine perturbs mitochondria both directly and indirectly to induce apoptosis.
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PMID:Phytosphingosine induced mitochondria-involved apoptosis. 1572 52

The microbial peptidomacrolide FK506 affects many eukaryotic developmental and cell signaling programs via calcineurin inhibition. Prior formation of a complex between FK506 and intracellular FK506-binding proteins (FKBPs) is the precondition for the interaction with calcineurin. A puzzling difference has emerged between the mammalian multidomain protein hFKBP38 and other FKBPs. It was shown that hFKBP38 not only binds to calcineurin but also inhibits the protein phosphatase activity of calcineurin on its own [Shirane, M. and Nakayama, K.I. (2003) Nature Cell Biol. 5, 28-37]. Inherent calcineurin inhibition by hFKBP38 would completely eliminate the need for FK506 in controlling many signal transduction pathways. To address this issue, we have characterized the functional and physical interactions between calcineurin and hFKBP38. A recombinant hFKBP38 variant and endogenous hFKBP38 were tested both in vitro and in vivo. The proteins neither directly inhibited calcineurin activity nor affected NFAT reporter gene activity in SH-SY5Y and Jurkat cells. In addition, a direct physical interaction between calcineurin and hFKBP38 was not detected in co-immunoprecipitation experiments. However, hFKBP38 indirectly affected the subcellular distribution of calcineurin by interaction with typical calcineurin ligands, as exemplified by the anti-apoptotic protein Bcl-2. Our data suggest that hFKBP38 cannot substitute for the FKBP/FK506 complex in signaling pathways controlled by the protein phosphatase activity of calcineurin.
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PMID:A reassessment of the inhibitory capacity of human FKBP38 on calcineurin. 1575 46

Recent studies indicate that caspase-2 is involved in the early stage of apoptosis before mitochondrial damage. Although the activation of caspase-2 has been shown to occur in a large protein complex, the mechanisms of caspase-2 activation remain unclear. Here we report a regulatory role of Bcl-2 on caspase-2 upstream of mitochondria. Stress stimuli, including ceramide and etoposide, caused caspase-2 activation, mitochondrial damage followed by downstream caspase-9 and -3 activation, and cell apoptosis in human lung epithelial cell line A549. When A549 cells were pretreated with the caspase-2 inhibitor benzyloxycarbonyl-Val-Asp(-OMe)-Val-Ala-Asp(-OMe)-fluoromethyl ketone or transfected with caspase-2 short interfering RNA, both ceramide- and etoposide-induced mitochondrial damage and apoptosis were blocked. Overexpression of Bcl-2 prevented ceramide- and etoposide-induced caspase-2 activation and mitochondrial apoptosis. Furthermore, caspase-2 was activated when A549 cells were introduced with Bcl-2 short interfering RNA or were treated with Bcl-2 inhibitor, which provided direct evidence of a negative regulatory effect of Bcl-2 on caspase-2. Cell survival was observed when caspase-2 was inhibited in Bcl-2-silencing cells. Blockage of the mitochondrial permeability transition pore and caspase-9 demonstrated that Bcl-2-modulated caspase-2 activity occurred upstream of mitochondria. Further studies showed that Bcl-2 was dephosphorylated at serine 70 after ceramide and etoposide treatment. A protein phosphatase inhibitor, okadaic acid, rescued Bcl-2 dephosphorylation and blocked caspase-2 activation, mitochondrial damage, and cell death. Taken together, ceramide and etoposide induced mitochondria-mediated apoptosis by initiating caspase-2 activation, which was, at least in part, regulated by Bcl-2.
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PMID:Bcl-2 rescues ceramide- and etoposide-induced mitochondrial apoptosis through blockage of caspase-2 activation. 1581 79

Protein phosphorylation constitutes one of the key signaling steps in physiological insulin secretion. The phosphorylation status of a given protein represents the balance of the activities of protein kinases and phosphatases, which induce the addition and removal of phosphate from that protein, respectively. Although several extant studies were focused on the identification and characterization of protein kinases in islets, relatively little information is available on the localization and regulation of protein phosphatases in beta cells. Emerging evidence implicates protein phosphatase 2A (PP2A) in the phenomenon of insulin secretion. The three principal objectives of this commentary are to: (i) review the existing evidence, which suggests regulation, by glucose and other insulin secretagogues, of PP2A in the beta cell; (ii) discuss the experimental evidence, which implicates PP2A-like enzymes in the dephosphorylation and inactivation of key beta cell phosphoprotein substrates (e.g., Akt and Bcl-2), which may be necessary for beta cell proliferation and survival, culminating in the loss of the beta cell mass; and (iii) highlight potential avenues for future research, including the development of specific pharmacological and therapeutic interventional modalities for the inhibition of specific PP2A-like phosphatases for the prevention of loss of beta cell mass leading to the onset of diabetes.
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PMID:Novel regulatory roles for protein phosphatase-2A in the islet beta cell. 1593 44

Oxysterols, and particularly 7-ketocholesterol, appear to be strongly involved in the physiopathology of atherosclerosis. These molecules are suspected to be cytotoxic to the cells of the vascular wall and monocytes/macrophages, particularly by inducing apoptosis. Previous studies have demonstrated that 7-ketocholesterol-induced apoptosis is triggered by a sustained increase of cytosolic-free Ca2+, which elicits the mitochondrial pathway of apoptosis by activation of the calcium-dependent phosphatase calcineurin, leading to dephosphorylation of the 'BH3 only' protein BAD. However, thorough study of the results suggests that other pathways are implicated in 7-ketocholesterol-induced cytotoxicity. In this study, we demonstrate the involvement of two other calcium-dependent pathways during 7-ketocholesterol-induced apoptosis. The activation of the MEK-->ERK pathway by the calcium-dependent tyrosine kinase PYK 2, a survival pathway which delays apoptosis as shown by the use of the MEK inhibitor U0126, and a pathway involving another pro-apoptotic BH3 only protein, Bim. Indeed, 7-ketocholesterol treatment of human monocytic THP-1 cells induces the release of Bim-LC8 from the microtubule-associated dynein motor complex, and its association with Bcl-2. Therefore, it appears that 7-ketocholesterol-induced apoptosis is a complex phenomenon resulting from calcium-dependent activation of several pro-apoptotic pathways and also one survival pathway.
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PMID:7-Ketocholesterol-induced apoptosis. Involvement of several pro-apoptotic but also anti-apoptotic calcium-dependent transduction pathways. 1595 68

Depletion of mitochondrial DNA (mtDNA) or treatment with mitochondrial poison CCCP initiates mitochondrial stress signaling, which operates through altered Ca2+ homeostasis. In C2C12 rhabdomyoblasts and A549 human lung carcinoma cells mitochondrial stress signaling activates calcineurin and a number of Ca2+ responsive factors including ATF, NFAT, CEBP/delta and CREB. Additionally, PKC and MAP kinase are also activated. A number of nuclear gene targets including those involved in Ca2+ storage/release (RyR1, calreticulin, calsequestrin), glucose metabolism (hexokinase, pyruvate kinase, Glut4), oncogenesis (TGFbeta1, cathepsin L, IGFR1, melanoma antigen) and apoptosis (Bcl-2, Bid, Bad, p53) are upregulated. Mitochondrial stress in both C2C12 myoblasts and A549 cells induced morphological changes and invasive phenotypes. These cells also showed markedly increased resistance to etoposide-induced apoptosis that is a hallmark of highly invasive tumors. Our results describe a new mechanism of altered nuclear gene expression and phenotypic changes triggered by mitochondrial dysfunction and mtDNA damage.
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PMID:Mitochondria-to-nucleus stress signaling in mammalian cells: nature of nuclear gene targets, transcription regulation, and induced resistance to apoptosis. 1597 49

Polyamine depletion prevents apoptosis by increasing serine/threonine phosphorylation leading to either inactivation or activation of pro- and anti-apoptotic proteins, respectively. Despite evidence that protein kinases are regulators of apoptosis, a specific role for protein phosphatases in regulating cell survival has not been established. In this study, we show that polyamine depletion inhibits serine/threonine phosphatase 2A (PP2A). Inhibition of PP2A in cells depleted of polyamines correlated well with increased phosphorylation of Bad at Ser112. Bad Ser112 phosphorylation in response to tumor necrosis factor (TNF)-alpha treatment decreased with time in cells grown in control as well as those grown in the presence of alpha-difluoromethylornithine plus putrescine. However, a sustained increase in the levels of Bad Ser112 phosphorylation was maintained in response to TNF-alpha treatment in cells grown in the presence of alpha-difluoromethylornithine. Inhibition of PP2A by okadaic acid and fostriecin or PP2A small interfering RNA transfection significantly decreased TNF-alpha-induced apoptosis in control and polyamine-depleted cells. Inhibition of PP2A by okadaic acid: 1) increased Bad and Bcl-2 phosphorylation at Ser112 and Ser70, respectively; 2) increased ERK activity; 3) prevented JNK activation; 4) prevented cytochrome c release, and activation of caspases-9 and -3 in response to TNF-alpha. Inhibition of MEK1 by U0126 prevented phosphorylation of Bad at Ser112. These results indicate that polyamines regulate PP2A activity, and inhibition of PP2A in response to polyamine depletion increases steady state levels of Bad and Bcl-2 proteins and their phosphorylation and thereby prevents cytochrome c release, caspase-9, and caspase-3 activation.
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PMID:Protein phosphatase 2A regulates apoptosis in intestinal epithelial cells. 1599 15

Protein tyrosine phosphatase predominantly determines the status of protein tyrosine kinase-dependent phosphorylation of specific proteins and controls the survival and death of neurons. Previous studies have shown that protein tyrosine phosphatase activity is decreased during hypoxia in cortical membranes of the newborn piglet. We have also shown that nitric oxide (NO) free radicals are generated during hypoxia, and may result in modification of protein tyrosine phosphatase via peroxynitrite-mediated modification. The present study tests the hypothesis that the hypoxia-induced decrease in protein tyrosine phosphatase activity is NO-mediated. To test this hypothesis, in vitro experiments were conducted by measuring protein tyrosine phosphatase activity in the presence of an NO donor, sodium nitroprusside (SNP), or peroxynitrite. Since 3-nitrotyrosine is produced as a consequence of peroxynitrite reactions, we have also examined the effect of 3-nitrotyrosine on protein phophatase activity. Cerebral cortical P(2) membranes were prepared from seven normoxic newborn piglets and each sample was divided into three aliquots: a control group, a SNP group (exposed to 200 microM SNP), and a peroxynitrite group (exposed to 100 microM peroxynitrite). Protein tyrosine phosphatase activity was determined spectrophotometrically in the presence or absence of 2 microM bpV(phen), a highly selective inhibitor of protein tyrosine phosphatase. The protein tyrosine phosphatase activity was 198+/-25 nmol/mg protein/h in the normoxic group, 177+/-30 nmol/mg protein/h in the SNP group (p=NS versus normoxic) and 77+/-20 nmol/mg protein/h in the peroxynitrite group (p<0.001 versus normoxic). The results show that peroxynitrite but not SNP exposure results in decreased protein tyrosine phosphatase activity in vitro. Furthermore 3-nitrotyrosine (100 microm), a product of peroxynitrite, decreased the enzyme activity from 926+/-102 to 200+/-77 (p<0.001). We conclude that protein tyrosine phosphatase regulation is mediated by peroxynitrite. We propose that hypoxia-induced NO production leading to peroxynitrite formation is a potential mechanism of protein tyrosine phosphatase inactivation in vivo. The NO-induced decrease in protein tyrosine phosphatase and protein phosphatase activity, leading to Bcl-2 protein phosphorylation and loss of its antiapoptotic activity may be a NO-mediated mechanism of programmed cell death in the hypoxic brain.
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PMID:Effect of nitration on protein tyrosine phosphatase and protein phosphatase activity in neuronal cell membranes of newborn piglets. 1603 61

Increased intraocular pressure (IOP) leads, by an unknown mechanism, to apoptotic retinal ganglion cell (RGC) death in glaucoma. We now report cleavage of the autoinhibitory domain of the protein phosphatase calcineurin (CaN) in two rodent models of increased IOP. Cleaved CaN was not detected in rat or mouse eyes with normal IOP. In in vitro systems, this constitutively active cleaved form of CaN has been reported to lead to apoptosis via dephosphorylation of the proapoptotic Bcl-2 family member, Bad. In a rat model of glaucoma, we similarly detect increased Bad dephosphorylation, increased cytoplasmic cytochrome c (cyt c), and RGC death. Oral treatment of rats with increased IOP with the CaN inhibitor FK506 led to a reduction in Bad dephosphorylation and cyt c release. In accord with these biochemical results, we observed a marked increase in both RGC survival and optic nerve preservation. These data are consistent with a CaN-mediated mechanism of increased IOP toxicity. CaN cleavage was not observed at any time after optic nerve crush, suggesting that axon damage alone is insufficient to trigger cleavage. These findings implicate this mechanism of CaN activation in a chronic neurodegenerative disease. These data demonstrate that increased IOP leads to the initiation of a CaN-mediated mitochondrial apoptotic pathway in glaucoma and support neuroprotective strategies for this blinding disease.
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PMID:Calcineurin cleavage is triggered by elevated intraocular pressure, and calcineurin inhibition blocks retinal ganglion cell death in experimental glaucoma. 1610 53

The immunosuppressant FK-506 binding protein 38 (FKBP38) is localized at the mitochondrial membrane and appears to play an important role in apoptosis. Recent reports about the potential functions of FKBP38 in apoptosis appear to be controversial. To further understand the biological function of FKBP38, here, we studied its molecular characteristics and a potential regulatory role on the anti-apoptotic protein Bcl-2. Our results suggest that FKBP38 appears to show chaperone activities in the citrate synthase aggregation assays during thermal denaturation and affect solubility of Bcl-2 when they are co-expressed. The FKBP family proteins bind the immunosuppressive drug FK-506 through the FK-506 binding domain and consequently inhibit the activity of calcineurin. In this study, from our NMR studies and calcineurin assays in vitro, we demonstrate that the N-terminal fragment of FKBP38 which contains the FK-506 binding domain does not bind FK-506 at molecular level. Lastly, to investigate the effect of FKBP38 on Bcl-2, we suppressed FKBP38 by RNA interference (RNAi) of FKBP38. Our results suggest that the suppression of FKBP38 appears to make Bcl-2 unstable or unprotected from degradation in an unknown mechanism.
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PMID:Molecular characterization of FK-506 binding protein 38 and its potential regulatory role on the anti-apoptotic protein Bcl-2. 1617 96


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