title: Mitogen activated protein kinase-dependent activation of c-Jun and c-Fos is required for neuronal differentiation but not for growth and stress response in PC12 cells.
abstract: MAPK-dependent activation of AP-1 protein c-Jun is involved in PC12 cell differentiation and apoptosis. However, the role of other AP-1 proteins and their connection to MAPKs during growth, differentiation and apoptosis has remained elusive. Here we studied the activation of AP-1 proteins in response to ERK, JNK, and p38 signaling upon NGF, EGF and anisomycin exposures. All treatments caused different kinetics and strength of MAPK and AP-1 activities. NGF induced persistent ERK and AP-1 activities, whereas upon EGF and anisomycin exposures, their activities were only weakly and transiently induced. The sustained AP-1 activity was associated with concomitant c-Fos and c-Jun expression and phoshorylation, which were JNK and ERK dependent. While inhibition of the ERK, JNK, and p38 activities partially prevented AP-1 activity and suppressed differentiation, none of them was required for anisomycin-induced apoptosis. The importance of c-Fos and c-Jun as mediators of differentiation was demonstrated by the findings that the corresponding siRNAs suppressed NGF-induced neurite outgrowth. However, the capacity of c-Fos to promote differentiation required cooperation with Jun proteins. In contrast, Fra-2 expression was not required for the differentiation response. Together, the results show that sustained c-Jun and c-Fos activities mediate MAPK signaling and are essential for differentiation of PC12 cells.
authors.affiliation: Department of Oncology, Helsinki University Central Hospital, HUCH, Finland.
authors.forename: Minna
authors.initials: M
authors.lastname: Eriksson
authors.forename: Minna
authors.initials: M
authors.lastname: Taskinen
authors.forename: Sirpa
authors.initials: S
authors.lastname: Leppä
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D049108:Cell Enlargement / Q000187:drug effects; D015536:Down-Regulation / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects / Q000378:metabolism; D051921:Fos-Related Antigen-2 / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016716:PC12 Cells; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference / Q000502:physiology; D051381:Rats; D013312:Stress, Physiological / Q000378:metabolism* / Q000503:physiopathology; D018808:Transcription Factor AP-1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism
chemical_list: D051921:Fos-Related Antigen-2; C497874:Fosl2 protein, rat; D036341:Intercellular Signaling Peptides and Proteins; D011500:Protein Synthesis Inhibitors; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases