c-FLIPL regulates PKC via AP-2 to inhibit Bax-mediated apoptosis induced by HIV-1 gp120 in Jurkat cells
Laboratory of Molecular Virology, Division of Emerging and Transfusion Transmitted Diseases, Center for Biologics Evaluation and Research, Food and Drug Administration, Building 29B, Rm 4NN16, 8800 Rockville Pike, Bethesda, MD, 20892, USA. Molecular and Cellular Biochemistry
(Impact Factor: 2.39).
05/2009; 330(1-2):23-9. DOI: 10.1007/s11010-009-0096-3
c-FLIPL, an inhibitor of caspase 8, is known to inhibit the Fas/caspase 8 apoptotic pathway; however, its involvement of Bax/mitochondrial apoptosis is not well understood. Using human cells, Jurkat cell line, induced with HIV-1 gp120, we studied the effects of c-FLIPL on Bax/mitochondrial apoptosis. We found that the induction of apoptosis by HIV-1 envelope protein, gp120, involved the activation of both Bax-dependent and death receptor-mediated pathways, and HIV-1 infection deceased c-FLIPL expression. Interestingly, c-FLIPL expression downregulated protein kinase C (PKC) expression at the transcript level involving activated protein-2 (AP-2). c-FLIPL expression reduced AP-2 protein levels required to promote PKC protein expression and PKC-associated inactive form of Bax, and inhibited Bax activation, suggesting that c-FLIPL inhibits Bax activation via modulating PKC expression at the transcriptional level involving AP-2 during gp120 treatment. Collectively, these findings further corroborate the concept that gp120 plays an important role, via involvement of molecules such as c-FLIPL, in apoptotic cell death due to HIV-1 infection.
Available from: Ji Ying Tan
- "Caspase-8 is a critical component of DISC where caspase-8 cleavage from its trimer to become the active form of caspase-8 necessary to activate the effector caspases, such as caspase-3, in the downstream of Fas signaling . 1 MOI of virus H1N1pdm- infected A549 cells displayed more caspase-8 cleavage from day 2 (Fig. 3A) which suggests that H1N1pdm infection is able to induce apoptosis in A549 cells through Fas signaling. FLIP, for example, is an inhibitor of caspase-8, and increased recruitment of FLIP into DISC results in blockage of caspase-8 activity  , which inhibits Fas-mediated apoptotic signaling and virus replication (Fig. 2B). To test the effect of caspase-8 inhibition on H1N1pdm production, A549 cells were infected with 1 MOI of virus for 2 h, and then incubated in Fig. 2. Virus infection modulated molecules of components in DISC formation and expression of them impacts viral replication. "
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ABSTRACT: It is not well-known whether apoptosis signaling affects influenza virus infection and reproduction in human lung epithelial cells. Using A549 cell line, we studied the relationship of some apoptosis-associated molecules with novel pandemic influenza A (H1N1) virus, A/California/04/2009. Infected cells displayed upregulated Fas ligand, activated FADD and caspase-8, and downregulated FLIP in the extrinsic apoptotic pathway. p53 expression increased and Bcl-XL expression decreased in the intrinsic pathway. Expression of pre-apoptotic molecules (FasL, FADD, and p53) increased virus replication, while inhibition of activity of FADD, caspase-8 and caspase-3, and expression of anti-apoptotic proteins (FLIP and Bcl-XL) decreased virus replication. p38, ERK and JNK from MAPK pathways were activated in infected cells, and inhibition with their inhibitors diminished virus replication. In the p38 superfamily, p38α expression increased viral RNA production, while expression of p38β and p38γ decreased. These data indicated that influenza virus induces apoptotic signaling pathways, which benefit virus replication.
Available from: synapse.koreamed.org
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ABSTRACT: Background: It is known that cigarette smoke (CS) causes cell death. Apoptotic cell death is involved in the pathogenesis of CS-related lung diseases. Some members of the protein kinase C (PKC) family have roles in cigarette smoke extract (CSE)-induced apoptosis. This study was conducted to investigate the role of PKC epsilon in CSE-induced apoptosis in human lung fibroblast cell line, MRC-5. Methods: Lactate dehydrogenase release was measured using a cytotoxicity detection kit. The MTT assay was used to measure cell viability. Western immunoblot, Hoechst 33342 staining and flow cytometry were used to demonstrate the effect of PKC ε.. Caspase-3 and caspase-8 activities were determined using a colorimetric assay. To examine PKC ε activation, Western blotting was performed using both fractions of membrane and cytosol. Results: We showed that CSE activated PKC ε by demonstrating increased expression of PKC ε in the plasma membrane fraction. Pre-treatment of PKC ε peptide inhibitor attenuated CSE-induced apoptotic cell death, as demonstrated by the MTT assay (13.03% of control, 85.66% of CSE-treatment, and 53.73% of PKC ε peptide inhibitor-pre-treatment, respectively), Hoechst 33342 staining, and flow cytometry (85.64% of CSE-treatment, 53.73% of PKC ε peptide inhibitor-pre-treatment). Pre-treatment of PKC ε peptide inhibitor reduced caspase-3 expression and attenuated caspase-3, caspase-8 activity compared with CSE treatment alone. Conclusion: PKC ε seem to have pro-apoptotic function and exerts its function through the extrinsic apoptotic pathway in CSE-exposed MRC-5 cells. This study suggests that PKC ε inhibition may be a therapeutic strategy in CS-related lung disease such as chronic obstructive pulmonary disease. Copyright©2011. The Korean Academy of Tuberculosis and Respiratory Diseases. All rights reserved.
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