Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Fas receptor (APO-1/CD95) is expressed on hepatocytes and is thought to be important in triggering apoptosis after ligation by the Fas ligand carried on cytotoxic T cells. Recent evidence has shown that several splice variants of Fas exist, the major one of which (FasTMDel) may produce a soluble protein which can modulate apoptosis by interacting with ligand. There are no data on the expression of splice variants of Fas in liver disease. RNA was extracted from needle biopsies from 13 patients with hepatitis C virus (HCV) infection and six normal liver samples. By reverse transcriptase polymerase chain reaction (RT-PCR) FasTMDel expression was demonstrated at the mRNA level, in both normal and HCV-infected liver. Quantitative PCR demonstrated an increase in Fas transcript relative to FasTMDel in HCV infection. This difference is due to an induction of Fas, with FasTMDel remaining at constant levels in the two groups. If translated into protein, liver cells may express more Fas and thus be susceptible to apoptosis inducible by ligand-bearing cytotoxic T cells. These findings suggest that mechanisms exist to regulate the differential splicing of Fas and FasTMDel dependent on the cell's environment. The degree of alteration in the levels of Fas relative to FasTMDel occurred independently of the ALT levels and histological grading of the HCV-infected cases. However, an association was noted between increasing Fas:FasTMDel ratio and log viral load in the liver, measured by competitive PCR.
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PMID:Alteration in mRNA levels of Fas splice variants in hepatitis C-infected liver. 942 85

Interferon gamma (IFNgamma) inhibits the growth and differentiation of highly purified human erythroid colony-forming cells (ECFCs) and induces erythroblast apoptosis. These effects are dose- and time-dependent. Because the cell surface receptor known as Fas (APO-1; CD95) triggers programmed cell death after activation by its ligand and because incubation of human ECFCs with IFNgamma produces apoptosis, we have investigated the expression and function of Fas and Fas ligand (FasL) in highly purified human ECFCs before and after incubation with IFNgamma in vitro. Only a small percentage of normal human ECFCs express Fas and this is present at a low level as detected by Northern blotting for the Fas mRNA and flow cytometric analysis of Fas protein using a specific mouse monoclonal antibody. The addition of IFNgamma markedly increased the percentage of cells expressing Fas on the surface of the ECFCs as well as the intensity of Fas expression. Fas mRNA was increased by 6 hours, whereas Fas antigen on the cell surface increased by 24 hours, with a plateau at 72 hours. This increase correlated with the inhibitory effect of IFNgamma on ECFC proliferation. CH-11 anti-Fas antibody, which mimics the action of the natural FasL, greatly enhanced IFNgamma-mediated suppression of cell growth and production of apoptosis, indicating that Fas is functional. Expression of FasL was also demonstrated in normal ECFCs by reverse transcriptase-polymerase chain reaction and flow cytometric analysis with specific monoclonal antibody. FasL was constitutively expressed among erythroid progenitors as they matured from day 5 to day 8 and IFNgamma treatment did not change this expression. Apoptosis induced by IFNgamma was greatly reduced by the NOK-2 antihuman FasL antibody and an engineered soluble FasL receptor, Fas-Fc, suggesting that Fas-FasL interactions among the ECFCs produce the erythroid inhibitory effects and apoptosis initiated by IFNgamma.
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PMID:Fas ligand is present in human erythroid colony-forming cells and interacts with Fas induced by interferon gamma to produce erythroid cell apoptosis. 945 53

Renal cell carcinoma (RCC) is the most common renal neoplasm. Despite being infiltrated by tumour infiltrating lymphocytes (TIL), these TIL are unable to control tumour growth in vivo, suggesting that the cytotoxic capacity of TIL against RCC is impaired, or that the tumour cells are resistant to killing and therefore escape detection by the immune system. It is postulated that the expression of apoptotic regulatory molecules in RCC favours tumour cell survival. The present study has therefore determined the expression of Fas (APO-1/CD95), Fas ligand (Fas L) and bcl-2 in these tumours. The expression of Fas, Fas L and bcl-2 mRNA transcripts was determined in RCC, normal kidney and peripheral blood by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR), following RNA extraction and cDNA synthesis from tissues and cell samples. Transcript levels were measured by densitometry after Southern blot hybridization of PCR products with internal radio-labelled oligonucleotide probes; a densitometry score was assigned to each hybridizing DNA band and expressed as a ratio of the glyceraldehyde-3-phosphate dehydrogenase content. In peripheral blood, the expression of Fas L and bcl-2 transcripts was similar between patients and normal healthy individuals; however, Fas transcript expression was significantly down-regulated in the patients' versus normal peripheral blood (P = 0.026). Most interestingly, significantly up-regulated Fas L expression was observed in RCC compared to normal kidney (P = 0.041). In contrast, bcl-2 transcripts were well represented in normal kidney but markedly decreased in RCC (P = 0.021). The expression of Fas transcripts in normal kidney and RCC was variable. These data demonstrate elevated expression of Fas L transcripts in RCC, but the functional relevance of this remains to be investigated.
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PMID:Expression of apoptotic regulatory molecules in renal cell carcinoma: elevated expression of Fas ligand. 1010 81

Intestinal intraepithelial lymphocytes (IEL) constitute the first lymphoid compartment to encounter dietary antigens and intestinal pathogens. IEL are proposed to be involved in the defence against bacterial and viral invasion and to play an important role in mucosal immunity. Fas (CD95/APO-1) is a surface receptor that induces apoptotic cell death upon ligation with Fas ligand (FasL). The aim of this study was to examine the expression and function of Fas and FasL on freshly isolated normal human colonic IEL. The expression and function of Fas and FasL on IEL isolated from 40 normal colonic specimens were examined by flow cytometry, reverse transcriptase-polymerase chain reaction, immunohistochemistry, and DNA-release cytotoxicity assay. Virtually all CD3+ IEL (95.2 +/- 4.3%) expressed Fas and were sensitive to agonistic anti-Fas antibody, whereas only 56.6 +/- 8.4% of peripheral T lymphocytes expressed Fas and were resistant to the antibody. We also detected FasL mRNA and protein (40.1 +/- 4.2%) on IEL, and found that IEL exerted FasL-mediated cytotoxicity against Fas-expressing target cells. These findings suggest that human IEL are activated in situ but are tightly regulated by the constitutive expression of functional Fas and FasL to maintain homeostasis of the mucosal immune system.
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PMID:Functional expression of Fas and Fas ligand on human intestinal intraepithelial lymphocytes. 1020 9

Sarcoidosis is a chronic inflammatory disease of unknown aetiology characterized by the formation of non-necrotizing granulomas. The course of disease is usually self-limiting with the spontaneous resolution of granuloma. In the immune system, Fas antigen (Fas) and Fas ligand (FasL) are involved in the down regulation of immune reactions by inducing apoptosis. Therefore, it was hypothesized that the Fas/FasL pathway and apoptosis may be associated with the course of granulomatous inflammation in sarcoidosis. Terminal deoxynucleotidyl transferase-mediated biotin nick end-labelling (TUNEL) was performed to assess deoxyribonucleic acid strand breakages as a characteristic of apoptosis. Immunohistochemistry was also performed to detect Fas and FasL protein, and reverse transcriptase polymerase chain reaction (RT-PCR) and RT in situ PCR to detect FasL messenger ribonucleic acid (mRNA). Positive signals for TUNEL were detected in epithelioid histiocytes and lymphocytes within granulomas and in bronchoalveolar lavage (BAL) lymphocytes from patients with sarcoidosis. Positive signals for Fas were also detected in these cells. FasL mRNA was expressed in BAL lymphocytes from 15 of 20 patients with sarcoidosis, but from only one of 10 patients with normal lung parenchyma. FasL protein was expressed in lymphocytes surrounding and within the granuloma. There was a significant correlation between the result of TUNEL and clinical course in patients with sarcoidosis. Apoptosis in epithelioid histiocytes and inflammatory cells seems to participate in the course of granulomatous inflammation. Further studies are needed to determine the role of Fas, FasL and other regulatory factors in apoptosis in the granulomatous inflammation in pulmonary sarcoidosis.
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PMID:Apoptosis in the course of granulomatous inflammation in pulmonary sarcoidosis. 1044 8

Ligation of the Fas receptor induces death-inducing signaling complex (DISC) formation, caspase activation, and subsequent apoptotic death of several cell types. Epstein-Barr virus (EBV)-positive group III Burkitt's lymphoma (BL) cell lines have a marked resistance to Fas-mediated apoptosis, although expressing each of the DISC components, Fas/ APO-1-associated death domain protein (FADD), and caspase-8 (FLICE/MACH/Mch5). The apoptotic pathway distal to the DISC is intact because ceramide analogs, staurosporine, and granzyme B activate caspase-3 and induce apoptosis. Fas resistance was not explained by the putative death-attenuating caspase-8 isoforms. However, while Fas-activated cytosolic extracts from sensitive cells were capable of processing both procaspase-8 and procaspase-3 into active subunit forms, resistant cell extracts did not possess either of these activities. Accordingly, reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed higher transcript levels for the FLICE-inhibitory protein (FLIP(L)) in resistant cells and the ratio of caspase-8 to FLIP(L) measured by competition RT-PCR analysis directly correlated with susceptibility to Fas-mediated apoptosis of all cell lines. In addition, modification of the caspase-8/FLIP(L) ratio by caspase-8 or FLIP(L) overexpression was able to alter the susceptibility status of the cell lines tested. Our results imply that the relative levels of caspase-8 and FLIP(L) are an important determinant of susceptibility to Fas-mediated apoptosis.
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PMID:Modulation of caspase-8 and FLICE-inhibitory protein expression as a potential mechanism of Epstein-Barr virus tumorigenesis in Burkitt's lymphoma. 1047 98

Cholangiocarcinoma continues to have a dismal prognosis with an overall survival rate of less than 10%. An increased understanding of the molecular oncogenesis of this tumor is needed. Fas/APO-1 (CD95) receptor and Fas ligand have been implicated as key factors in apoptosis. In this study we have examined the role of the Fas receptor in the growth of cholangiocarcinoma. The purpose of this study was to evaluate the role of the Fas receptor in the induction of apoptosis in cholangiocarcinoma and to assess the role of the Fas receptor in cholangiocarcinoma tumorigenesis. Human cholangiocarcinoma cells, SK-ChA-1, were evaluated for Fas receptor expression using fluorescence-activated cell sorting (FACS). Distinct cell populations (Fas-positive and Fas-negative) were isolated by FACS and cloned from single cell dilutions. Fas expression was assessed by FACS and reverse transcriptase-polymerase chain reaction (RT-PCR). Cell populations were further characterized by their sensitivity to anti-Fas monoclonal antibody at 72 hours. Cell viability and apoptotic index were evaluated by trypan blue cell count and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL) assay, respectively. Distinct cell populations were evaluated for their ability to form tumors in BALB/c nude mice (2.5 x 10(6) cells per subcutaneous injection). After 4 weeks, tumors were evaluated for tumor area by caliper measurement and Fas expression by RT-PCR. Maintenance of biliary phenotype was assured by means of AE-1 (cytokeratin) immunohistochemistry. Populations of Fas-positive and Fas-negative cells were identified, isolated, and confirmed by FACS and RT-PCR. Treatment of Fas-positive cells with anti-Fas monoclonal antibody produced an 80% reduction in cell viability compared to no decrease in viability in Fas-negative cells by trypan blue cell count. TUNEL staining showed an apoptotic index of 75% for Fas-positive cells incubated with anti-Fas monoclonal antibody and no significant evidence of apoptosis in the Fas-negative cells. When cholangiocarcinoma cells were subcutaneously injected into nude mice, only Fas-negative cells formed tumor nodules; Fas-positive cells failed to form tumor nodules. The analyzed tumors lacked Fas messenger RNA by RT-PCR but maintained the biliary cytokeratin AE-1 by immunohistochemistry. Fas receptor expression is an important mediator of apoptosis in cultured human cholangiocarcinoma cells and appears to be a critical determinant of cholangiocarcinoma tumor growth in nude mice.
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PMID:Fas expression prevents cholangiocarcinoma tumor growth. 1048 89

Fas antigen is a cell surface protein that mediates apoptosis via signal transduction from the plasma membrane. Using reverse transcriptase-polymerase chain reaction (RT-PCR), messenger RNA for Fas antigen was detected in the human oral squamous cell carcinoma cell line, SCC-25. In serum-free medium, a monoclonal anti-Fas antibody (CH-11) induced Fas antigen expression in SCC-25 cells, as determined by immunocytochemistry and Western blotting, using an anti-Fas polyclonal antibody (Fas D) as primary antibody. Fas antigen was localized to the cytoplasm and the cell membrane. The molecular weight of the protein recognized by Western blot analysis was 35,000, consistent with the value reported for the Fas antigen. The CH-11 antibody did not induce Fas antigen expression in serum-containing medium. To determine whether CH-11 could induce apoptosis in oral squamous cell carcinoma, we examined its effects on the survival of cultured SCC-25 cells. Anti-Fas monoclonal antibody in serum-free medium induced cytotoxicity in SCC-25 cells in a time-dependent manner up to 8 h, as determined by phase-contrast microscopy and WST-1 assay. Marked nuclear condensation and fragmentation of chromatin were observed in the CH-11-treated cells using Hoechst 33342 staining. This anti-Fas monoclonal antibody also induced DNA ladder formation in SCC-25 cells in a time-dependent manner. The present results indicate that the anti-Fas monoclonal antibody (CH-11) may mediate apoptosis by binding to the Fas antigen expressed in SCC-25 cells.
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PMID:Fas expression and Fas monoclonal antibody-induced apoptosis in a human squamous cell carcinoma cell line, SCC-25. 1089 May 58

Ovarian follicular atresia occurs by apoptosis of granulosa and theca cells. The Fas antigen (Fas), a cell surface receptor that triggers apoptosis when activated by Fas ligand (FasL), may be involved in this process. A possible role of the Fas pathway in mediating serum withdrawal-induced apoptosis of granulosa cells was examined. Granulosa cells collected from 5- to 10-mm bovine follicles were cultured in DMEM-F12 containing serum for 3 days, deprived of serum, and live cells were counted at various times after serum withdrawal. Cell death increased significantly 6 h after serum withdrawal (21% +/- 7%; P: < 0.05 vs. 0 h) and continued to increase until 24 h (43% +/- 6%). No further increases in cell death were observed through 72 h. Detection of the translocation of phosphatidylserine to the outer surface of the cell membrane by annexin V binding indicated that cells died by apoptosis. Quantitative reverse transcriptase-polymerase chain reaction assays showed no changes in Fas mRNA levels but a 4.7-fold increase in FasL mRNA 3 h after serum withdrawal (P: < 0.05 vs. 0 h). FasL mRNA remained elevated through 24 h and returned to basal levels at 48 h. Immunohistochemical staining showed that both Fas and FasL protein increased on the cell surface within 3 h and remained elevated through 12 h (the last time point tested). Binding of FasL to Fas was blocked with two reagents that bind to the extracellular domain of FasL: an anti-FasL antibody and Fas:Fc, a chimeric protein consisting of the Fc portion of human immunoglobulin G and the extracellular domain of human Fas. Cell death 24 h after serum withdrawal was reduced 55% +/- 10% and 34% +/- 12% by anti-FasL antibody and Fas:Fc, respectively (P: < 0.05 vs. no blocking protein). In conclusion, serum withdrawal-induced apoptosis of bovine granulosa cells is mediated at least partially by Fas/FasL interactions. These results are consistent with a potential role of Fas in an autocrine or paracrine pathway to trigger ovarian follicular atresia.
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PMID:Apoptosis of bovine granulosa cells after serum withdrawal is mediated by Fas antigen (CD95) and Fas ligand. 1115 54

Proteasome inhibitors were shown previously to induce mitochondria-independent and caspase-3-dependent apoptosis in human glioma cell lines by unknown mechanisms. Here, we showed that treatment with proteasome inhibitors, lactacystin or acetyl-leucinyl-leucinyl-norleucinal, led to elevation of the steady-state c-Myc protein but not c-myc mRNA, suggesting the accumulation of c-Myc protein by proteasome inhibitors. In addition, the marked association of c-Myc protein with ubiquitin by treatment with proteasome inhibitors indicated the involvement of proteasome in c-Myc proteolysis and the stabilization of c-Myc protein by proteasome inhibitors in vivo. The expression of Fas (also termed CD95 or APO-1) mRNA, if analyzed by reverse transcriptase polymerase chain reaction assay, was found to occur constitutively, and increased slightly by the treatment with proteasome inhibitors. In contrast, the expression of Fas ligand (FasL) mRNA was markedly induced temporarily before the activation of caspase-3 by the treatment. Agonistic anti-Fas antibody (CH11) induced apoptotic cell death, suggesting the presence of a functional Fas receptor. In addition, proteasome inhibitor-induced apoptosis was prevented by the addition of antagonistic anti-FasL antibody (4A5) or z-IETD.fmk, a potent inhibitor of caspase-8, indicating the involvement of the Fas receptor-ligand apoptotic signaling system in proteasome inhibitor-mediated apoptosis. Thus, it is suggested that proteasome inhibitors cause the accumulation of c-Myc protein which induces transiently FasL message to stimulate the Fas receptor-ligand apoptotic signaling pathway.
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PMID:Proteasome inhibitors induce Fas-mediated apoptosis by c-Myc accumulation and subsequent induction of FasL message in human glioma cells. 1152 96


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