title: AP-1 mediated retinal photoreceptor apoptosis is independent of N-terminal phosphorylation of c-Jun.
abstract: Apoptosis is essential for retinal development but it is also a major mode of cell loss in many human retinal dystrophies. High levels of visible light induce retinal apoptosis in mice and rats. This process is dependent on the induction of the transcription factor AP-1, a dimeric complex composed of c-Fos and c-Jun/JunD phosphoproteins. While c-Fos is essential, JunD is dispensable for light-induced photoreceptor apoptosis. Here we show that N-terminal phosphorylation of c-Jun, the other main partner of c-Fos in induced AP-1 complexes is not required for programmed cell death during retinal development in vivo and is also dispensable for photoreceptor apoptosis induced by the exogenous stimuli "excessive light" and N-nitroso-N-methylurea (MNU). Mice expressing a mutant c-Jun protein (JunAA) that cannot be phosphorylated at its N-terminus are apoptosis competent and their retina is not distinguishable from wild-type mice. Accordingly, Jun kinase, responsible for phosphorylation of wild-type c-Jun protein is at best only marginally induced by the apoptotic stimuli "light" and MNU. Complex composition of light-induced AP-1 complexes is similar in wild-type and JunAA mice. This shows that the mutant c-Jun protein can be part of the DNA binding complex AP-1 and demonstrates that induction of the DNA binding activity of AP-1 after light insult does not depend on N-terminal phosphorylation of c-Jun. Our results suggest that transactivation of target genes by phosphorylated c-jun/AP-1 is not required for MNU- or light-induced apoptosis of photoreceptor cells.
authors.affiliation: Department of Ophthalmology, University Hospital, Frauenklinikstrasse 24, 8091 Zurich, Switzerland. cgrimm@opht.unizh.ch
authors.forename: C
authors.initials: C
authors.lastname: Grimm
authors.forename: A
authors.initials: A
authors.lastname: Wenzel
authors.forename: A
authors.initials: A
authors.lastname: Behrens
authors.forename: F
authors.initials: F
authors.lastname: Hafezi
authors.forename: E F
authors.initials: EF
authors.lastname: Wagner
authors.forename: C E
authors.initials: CE
authors.lastname: Remé
mesh_terms: D000477:Alkylating Agents / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D008770:Methylnitrosourea / Q000494:pharmacology; D051379:Mice; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000235:genetics; D016755:Proto-Oncogene Proteins c-jun / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014785:Vision, Ocular / Q000187:drug effects / Q000235:genetics
chemical_list: D000477:Alkylating Agents; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D008770:Methylnitrosourea; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases