Adrenomedullin promotes cell cycle transit and up-regulates cyclin D1 protein level in human glioblastoma cells through the activation of c-Jun/JNK/AP-1 signal transduction pathway.
Adrenomedullin is a secreted peptide hormone with multiple functions. Although a number of reports have indicated that adrenomedullin may be involved in tumor progression, its mechanism of action remains obscure. In this study, we have analysed the signal transduction pathway activated by adrenomedullin in human glioma cells. Our results revealed that adrenomedullin induced the phosphorylation of both c-Jun and JNK in glioblastoma cells. Silencing JNK expression with siRNA reversed the phosphorylation of c-Jun induced by adrenomedullin, indicating that JNK is responsible of c-Jun activation. In addition, electrophoretic mobility-shift assays showed that the increase in phosphorylation of c-Jun was associated with increased AP-1 DNA binding activity. Supershift assays and co-immunoprecipitation demonstrated that c-Jun and JunD are part of the AP-1 complex, indicating that activated c-Jun is dimerized with JunD in response to adrenomedullin. Furthermore, adrenomedullin was shown to promote cell transit beyond cell cycle phases with a concomittant increase in cyclin D1 protein level, suggesting that adrenomedullin effects cell proliferation through up-regulation of cyclin D1. The inhibition of JNK activation or the suppression of c-Jun or JunD expression with siRNA impaired the effects of adrenomedullin on cell proliferation and on cyclin D1. Taken together, these data demonstrate that activation of cJun/JNK pathway is involved in the growth regulatory activity of adrenomedullin in glioblastoma cells.
Ouafik
L'Houcine
L
INSERM UMR 911 CRO2, Angiogénèse, invasivité et micro-environnement tumoral, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, 13916 Marseille Cédex 20, France.
Berenguer-Daize
Caroline
C
Berthois
Yolande
Y
D053607:Adrenomedullin / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology*; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000502:physiology; D019938:Cyclin D1 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D019281:Dimerization; D004789:Enzyme Activation; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005909:Glioblastoma / Q000473:pathology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D009363:Neoplasm Proteins / Q000502:physiology; D011480:Protease Inhibitors / Q000494:pharmacology; D016755:Proto-Oncogene Proteins c-jun / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000502:physiology
D051017:Apoptosis Regulatory Proteins; C530104:CCND1 protein, human; D009363:Neoplasm Proteins; D011480:Protease Inhibitors; D016755:Proto-Oncogene Proteins c-jun; D034741:RNA, Small Interfering; D018808:Transcription Factor AP-1; D019938:Cyclin D1; D053607:Adrenomedullin; D000242:Cyclic AMP; D048031:JNK Mitogen-Activated Protein Kinases