期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 279, 期 34, 页码 35564-35572出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M401037200
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资金
- NEI NIH HHS [EY014793, EY13520] Funding Source: Medline
The rd mouse, an accepted animal model for photoreceptor degeneration in retinitis pigmentosa, has a recessive mutation for the gene encoding the beta-subunit of the cGMP phosphodiesterase. This mutation results in high levels of cGMP, which leaves an increased number of the cGMP-gated channels in the open state, thus allowing intracellular calcium (Ca2+) to rise to toxic levels, and rapid photoreceptor degeneration follows. To delineate the events in rd photoreceptor degeneration, we demonstrated an increase in calpain and caspase-3 activity, hypothesizing that Ca2+-mediated apoptosis in photoreceptors is mediated by calpain, involving mitochondrial depolarization and caspase-3 activation. To examine this hypothesis further, a murine photoreceptor-derived cell line (661W) was treated with the Ca2+ ionophore A23187, cGMP-gated channel agonist 8-bromoc-GMP, or phosphodiesterase inhibitor isobutylmethylxanthine to mimic the increased Ca2+ influx seen in the rd photoreceptors. Ca2+-induced cell death in 661W cells was found to be mediated by calpain and caspase-3 and could be completely inhibited by the calpain inhibitor SJA6017, implicating both calpain and caspases in the apoptotic process. The apoptotic events correlated in an SJA6017-inhibitable manner with bid cleavage, mitochondrial depolarization, cytochrome c release, and caspase-3 and -9 activation. We concluded that Ca2+ influx in the rd model of photoreceptor degeneration leads to the activation of the cysteine protease calpain, which executes apoptosis via modulation of caspase-3 activity.
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