Pim-1 controls NF-kappaB signalling by stabilizing RelA/p65.
Post-translational modification and degradation of proteins by the ubiquitin-proteasome system are key regulatory mechanisms in cellular responses to various stimuli. The NF-kappaB signaling pathway is controlled by the ubiquitin-mediated proteolysis. RelA/p65, which is a main subunit of NF-kappaB, is ubiquitinated for degradation by SOCS-1, but the functional mechanism of its ubiquitination remains poorly understood. In this study we show that phosphorylation of RelA/p65 at Ser276 prevents its degradation by ubiquitin-mediated proteolysis. In contrast, impairment of Ser276 phosphorylation affects constitutive degradation of RelA/p65. Importantly, we identify Pim-1 as a further kinase responsible for the phosphorylation of RelA/p65 at Ser276. Depletion of Pim-1 hinders not only Ser276 phosphorylation but also transactivation of RelA/p65 target genes. We also show that Pim-1 contributes to recruitment of RelA/p65 to kappaB-elements to activate NF-kappaB signalling after TNF-alpha stimulation. In concert with these results, the knockdown of Pim-1 impairs IL-6 production and augments apoptosis by interfering RelA/p65 activation. These findings provide a model in which Pim-1 phosphorylation of RelA/p65 at Ser276 allows defense against ubiquitin-mediated degradation and whereby exerts activation of NF-kappaB signalling.
Nihira
K
K
Department of Molecular Genetics, Medical Research Institute, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8510, Japan.
Ando
Y
Y
Yamaguchi
T
T
Kagami
Y
Y
Miki
Y
Y
Yoshida
K
K
D000595:Amino Acid Sequence / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D019556:COS Cells; D002522:Chlorocebus aethiops; D015536:Down-Regulation / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D051573:Proto-Oncogene Proteins c-pim-1 / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051996:Transcription Factor RelA / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology; D025801:Ubiquitin / Q000378:metabolism*
D015850:Interleukin-6; D016328:NF-kappa B; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D025801:Ubiquitin; D012694:Serine; D051573:Proto-Oncogene Proteins c-pim-1