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Protein Kinase Cβ Modulates Ligand-induced Cell Surface Death Receptor Accumulation: A MECHANISTIC BASIS FOR ENZASTAURIN-DEATH LIGAND SYNERGY.
- Source :
-
Journal of Biological Chemistry . 1/8/2010, Vol. 285 Issue 2, p888-902. 5p. - Publication Year :
- 2010
-
Abstract
- Although treatment with the protein kinase C (P1(C) activator phorbol 12-myristate 13-acetate (PMA) is known to protect a subset of cells from induction of apoptosis by death ligands such as Fas ligand and tumor necrosis factor-α-related apoptosis-inducing ligand, the mechanism of this protection is unknown. This study demonstrated that protection in short term apoptosis assays and long term proliferation assays was maximal when Jurkat or HL-60 human leukemia cells were treated with 2-5 flM PMA. Immunoblotting demonstrated that multiple PKC isoforms, including PKCα, PKCβ, PKCϵ, and PKCO, translocated from the cytosol to a membrane-bound fraction at these PMA concentrations. When the ability of short hairpin RNA (shRNA) constructs that specifically down-regulated each of these isoforms was examined, PKCβ shRNA uniquely reversed PMAinduced protection against cell death, The PKCβ-selective small molecule inhibitor enzastaurin had a similar effect. Although mass spectrometry suggested that Fas is phosphorylated on a number of serines and threonines, mutation of these sites individually or collectively had no effect on Fas-mediated death signaling or PMA protection. Further experiments demonstrated that PMA diminished ligand-induced cell surface accumulation of Fas and DR5, and PKCβ shRNA or enzastaurin reversed this effect. Moreover, enzastaurin sensitized a variety of human tumor cell lines and clinical acute myelogenous leukemia isolates, which express abundant PKCβ, to tumor necrosis factor-a related apoptosis-inducing ligand-induced death in the absence of PMA. Collectively, these results identify a specific PKC isoform that modulates death receptor-mediated cytotoxicity as well as a small molecule inhibitor that mitigates the inhibitory effects of PKC activation on ligand-induced death receptor trafficking and cell death. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00219258
- Volume :
- 285
- Issue :
- 2
- Database :
- Academic Search Index
- Journal :
- Journal of Biological Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 70702257
- Full Text :
- https://doi.org/10.1074/jbc.M109.057638