The mycotoxin penicillic acid inhibits Fas ligand-induced apoptosis by blocking self-processing of caspase-8 in death-inducing signaling complex.
Upon engagement with Fas ligand (FasL), Fas rapidly induces recruitment and self-processing of caspase-8 via the adaptor protein Fas-associated death domain (FADD), and activated caspase-8 cleaves downstream substrates such as caspase-3. We have found that penicillic acid (PCA) inhibits FasL-induced apoptosis and concomitant loss of cell viability in Burkitt's lymphoma Raji cells. PCA prevented activation of caspase-8 and caspase-3 upon treatment with FasL. However, PCA did not affect active caspase-3 in FasL-treated cells, suggesting that PCA primarily blocks early signaling events upstream of caspase-8 activation. FasL-induced processing of caspase-8 was severely impaired in the death-inducing signaling complex, although FasL-induced recruitment of FADD and caspase-8 occurred normally in PCA-treated cells. Although PCA inhibited the enzymatic activities of active recombinant caspase-3, caspase-8, and caspase-9 at similar concentrations, PCA exerted weak inhibitory effects on activation of caspase-9 and caspase-3 in staurosporine-treated cells but strongly inhibited caspase-8 activation in FasL-treated cells. Glutathione and cysteine neutralized an inhibitory effect of PCA on caspase-8, and PCA bound directly to the active center cysteine in the large subunit of caspase-8. Thus, our present results demonstrate that PCA inhibits FasL-induced apoptosis by targeting self-processing of caspase-8.
Bando
Masashige
M
Research Center for Experimental Biology and Department of Bioengineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
Hasegawa
Makoto
M
Tsuboi
Yasunori
Y
Miyake
Yasunobu
Y
Shiina
Masashi
M
Ito
Mika
M
Handa
Hiroshi
H
Nagai
Kazuo
K
Kataoka
Takao
T
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001483:Base Sequence; D002352:Carrier Proteins / Q000502:physiology; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D003545:Cysteine / Q000494:pharmacology; D017931:DNA Primers; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D005978:Glutathione / Q000494:pharmacology; D007700:Kinetics; D016393:Lymphoma, B-Cell; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D009183:Mycotoxins / Q000633:toxicity; D010398:Penicillic Acid / Q000633:toxicity*; D016133:Polymerase Chain Reaction; D012694:Serine / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014407:Tumor Cells, Cultured
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D017931:DNA Primers; C505534:Fadd protein, mouse; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D009183:Mycotoxins; D012694:Serine; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D005978:Glutathione; D003545:Cysteine; D010398:Penicillic Acid