Abstract
Mouse 3T3 fibroblasts derived from fetuses lacking c-Jun were used to define an essential role of c-Jun, a main component of the transcription factor AP-1, in the cellular response to the alkylating agent methyl methanesulfonate (MMS). MMS represents the most potent and selective activator of the stress-induced kinases JNK/SAPK and p38, resulting in very efficient induction of c-Jun hyperphosphorylation and c-jun transcription. This agent induced apoptosis with high efficiency in wild-type cells but not in c-jun(-/-) cells. Resistance to apoptosis was accompanied by impaired expression of CD95 ligand (CD95-L), a well-known inducer of apoptosis. The addition of recombinant CD95-L restored apoptosis sensitivity in c-jun(-/-) fibroblasts. MMS-induced apoptosis in wild-type fibroblasts or human lymphocytes was strongly reduced by neutralizing CD95-L antibodies or transdominant negative FADD, confirming the importance of CD95 signalling in MMS-induced apoptosis. The loss-of-function approach in fibroblasts allowed the identification and dissection of c-Jun-dependent and -independent processes upstream or downstream of CD95 activation. We have found that c-Jun can act as a proapoptotic regulator in cells exposed to DNA damage via induction of CD95-L. Once activated, CD95-induced death signalling is not affected by the loss of c-Jun, demonstrating that only the initiation and not the execution of stress-induced apoptosis depends on c-Jun.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Activating Transcription Factor 2
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Adaptor Proteins, Signal Transducing*
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Alkylating Agents / pharmacology*
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Animals
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Antibodies / pharmacology
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Apoptosis / drug effects*
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Carrier Proteins / genetics
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Carrier Proteins / physiology
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Cell Line
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Cyclic AMP Response Element-Binding Protein / metabolism
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Fas Ligand Protein
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Fas-Associated Death Domain Protein
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Fibroblasts / cytology
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Fibroblasts / drug effects
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Fibroblasts / metabolism
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Gene Deletion
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Gene Expression / drug effects
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Humans
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Kinetics
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Membrane Glycoproteins / antagonists & inhibitors
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Membrane Glycoproteins / genetics
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Membrane Glycoproteins / metabolism*
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Membrane Glycoproteins / pharmacology
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Methyl Methanesulfonate / pharmacology
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Mice
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Proto-Oncogene Proteins c-jun / deficiency
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Proto-Oncogene Proteins c-jun / genetics
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Proto-Oncogene Proteins c-jun / metabolism*
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
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Recombinant Proteins / metabolism
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Recombinant Proteins / pharmacology
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Signal Transduction / drug effects
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Transcription Factor AP-1 / physiology
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Transcription Factors / metabolism
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Transcriptional Activation / drug effects*
Substances
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Activating Transcription Factor 2
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Adaptor Proteins, Signal Transducing
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Alkylating Agents
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Antibodies
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Carrier Proteins
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Cyclic AMP Response Element-Binding Protein
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FADD protein, human
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FASLG protein, human
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Fadd protein, mouse
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Fas Ligand Protein
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Fas-Associated Death Domain Protein
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Fasl protein, mouse
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Membrane Glycoproteins
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Proto-Oncogene Proteins c-jun
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RNA, Messenger
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Recombinant Proteins
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Transcription Factor AP-1
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Transcription Factors
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Methyl Methanesulfonate