Destabilization of CARP mRNAs by aloe-emodin contributes to caspase-8-mediated p53-independent apoptosis of human carcinoma cells.
Using short hairpin RNA against p53, transient ectopic expression of wild-type p53 or mutant p53 (R248W or R175H), and a p53- and p21-dependent luciferase reporter assay, we demonstrated that growth arrest and apoptosis of FaDu (human pharyngeal squamous cell carcinoma), Hep3B (hepatoma), and MG-63 (osteosarcoma) cells induced by aloe-emodin (AE) ... are p53-independent. Co-immunoprecipitation and small interfering RNA (siRNA) studies demonstrated that AE caused S-phase cell cycle arrest by inducing the formation of cyclin A-Cdk2-p21 complexes through extracellular signal-regulated kinase (ERK) activation. Ectopic expression of Bcl-X(L) and siRNA-mediated Bax attenuation significantly inhibited apoptosis induced by AE. Cyclosporin A or the caspase-8 inhibitor Z-IETD-FMK blocked AE-induced loss of mitochondrial membrane potential and prevented increases in reactive oxygen species and Ca(++). Z-IETD-FMK inhibited AE-induced apoptosis, Bax expression, Bid cleavage, translocation of tBid to mitochondria, ERK phosphorylation, caspase-9 activation, and the release of cytochrome c, apoptosis-inducing factor (AIF), and endonuclease G from mitochondria. The stability of the mRNAs encoding caspase-8 and -10-associated RING proteins (CARPs) 1 and 2 was affected by AE, whereas CARP1 or 2 overexpression inhibited caspase-8 activation and apoptosis induced by AE. Collectively, our data indicate AE induces caspase-8-mediated activation of mitochondrial death pathways by decreasing the stability of CARP mRNAs in a p53-independent manner.
Mesh Terms:
Animals, Apoptosis, Blotting, Western, Carrier Proteins, Caspase 8, Cell Cycle, Cell Line, Cell Line, Tumor, Cyclin A, Cyclin-Dependent Kinase 2, Cyclin-Dependent Kinase Inhibitor p21, Emodin, Extracellular Signal-Regulated MAP Kinases, HEK293 Cells, Humans, Neoplasms, Nerve Tissue Proteins, Phosphorylation, Protein Binding, Protein Kinase Inhibitors, RNA Interference, RNA Stability, RNA, Messenger, Reverse Transcriptase Polymerase Chain Reaction, Tumor Suppressor Protein p53
Animals, Apoptosis, Blotting, Western, Carrier Proteins, Caspase 8, Cell Cycle, Cell Line, Cell Line, Tumor, Cyclin A, Cyclin-Dependent Kinase 2, Cyclin-Dependent Kinase Inhibitor p21, Emodin, Extracellular Signal-Regulated MAP Kinases, HEK293 Cells, Humans, Neoplasms, Nerve Tissue Proteins, Phosphorylation, Protein Binding, Protein Kinase Inhibitors, RNA Interference, RNA Stability, RNA, Messenger, Reverse Transcriptase Polymerase Chain Reaction, Tumor Suppressor Protein p53
J. Cell. Biochem.
Date: Apr. 01, 2011
PubMed ID: 21308745
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