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Mol. Cell. Biol., Oct 1995, 5576-5585, Vol 15, No. 10
RP Bissonnette, T Brunner, SB Lazarchik, NJ Yoo, MF Boehm, DR Green and RA Heyman
T-cell hybridomas, thymocytes, and T cells can be induced to undergo
apoptotic cell death by activation through the T-cell receptor. This
process requires macromolecular synthesis and thus gene expression, and it
has been shown to be influenced by factors regulating transcription.
Recently, activation, T-cell hybridomas rapidly express the Fas/CD95
receptor and its ligand, Fas ligand (FasL), which interact to transduce the
death signal in the activated cell. Retinoids, the active metabolites of
vitamin A, modulate expression of specific target genes by binding to two
classes of intracellular receptors, retinoic acid receptors (RARs) and
retinoid X receptors (RXRs). They are potent modulators of apoptosis in a
number of experimental models, and they have been shown to inhibit
activation-induced apoptosis in T-cell hybridomas and thymocytes.
Particularly effective is the prototypic pan- agonist 9-cis retinoic acid
(9-cis RA), which has high affinity for both RARs and RXRs. We report here
that 9-cis RA inhibits T-cell receptor-mediated apoptosis in T-cell
hybridomas by blocking the expression of Fas ligand following activation.
This inhibition appears to be at the level of FasL mRNA, with the
subsequent failure to express cell surface FasL. RAR-selective (TTNPB) or
RXR-selective (LG100268) ligands alone were considerably less potent than
RAR-RXR pan-agonists. However, the addition of both RAR- and RXR-selective
ligands was as effective as the addition of 9-cis RA alone. The
demonstrates that the inhibitory effect requires the ligand-mediated
activation of both retinoid receptor signaling pathways.
Copyright © 1995, American Society for Microbiology
9-cis retinoic acid inhibition of activation-induced apoptosis is mediated via regulation of fas ligand and requires retinoic acid receptor and retinoid X receptor activation
Department of Cell Biology, Ligand Pharmaceuticals, San Diego, California 92121, USA.
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