The 90 kDa ribosomal S6 kinase (RSK) family of proteins is a group of highly conserved Ser/Thr kinases that regulate diverse cellular processes, such as cell growth, cell motility, cell survival and cell proliferation. RSKs are downstream effectors of the Ras-extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) signalling cascade. Significant advances in the field of RSK and ERK/MAPK signalling have occurred in the past few years, including biological insights and the discovery of novel substrates and new RSK regulatory mechanisms. Collectively, these data expand the current models of RSK signalling and highlight potential directions of research in RSK-mediated survival, growth, proliferation and migration.
"result in the subsequent pro-survival signaling cascade, which is the activation of the 90 kDa ribosomal S6 kinase and its downstream pathway . The transcriptional factor cAMP-response element binding protein (CREB) phosphorylation is ribosomal S6 kinase-mediated and facilitates the neuron survival through increased transcription of pro-survival genes, such as Bcl2 family members (Anjum and Blenis, 2008). Indeed, the expression of Bcl-2 was reduced when TrkB was knocked down in this study (Fig. 1). "
"In addition to the aforementioned increase in the K17–hnRNP K interaction, TPA also activates RSK (Fig. S3 C), a regulator of various cellular processes including cell growth, proliferation , and motility (Anjum and Blenis, 2008). As we previously showed that K17 is phosphorylated by RSK (Pan et al., 2011), we next investigated whether RSK modulates the K17–hnRNP K interaction and CXCR3 ligand expression. "
"RSK2 acts as a protection against TNF-a-mediated inhibition of bone formation. RSK2 is a growth-factor-regulated kinase that was reported to mediate cell cycle progression and cell proliferation in numerous cell types and organisms (Anjum and Blenis, 2008; Cho et al., 2005; David et al., 2005; Eisinger-Mathason et al., 2008; Lin et al., 2008; Romeo and Roux, 2011; Wang et al., 2010). We now report the reduced in vitro growth ability of osteoblast lacking RSK2. "
[Show abstract][Hide abstract] ABSTRACT: Objective Arthritis is a chronic inflammatory disease characterised by immune cell infiltration and mesenchymal cell expansion in the joints. Although the role of immune cells in arthritis is well characterised, the development of mesenchymal cell hyperplasia needs to be better defined. Here, we analysed the role of the ribosomal S6 kinase Rsk2, which we found to be highly activated in joints of patients with arthritis, in the development of mesenchymal cell hyperplasia.
Methods We genetically inactivated Rsk2 in the tumour necrosis factor (TNF)-α transgenic (TNFtg) mice, an animal model for human inflammatory arthritis. Clinical and histological signs of arthritis as well as molecular markers of inflammation and joint destruction were quantified. Fibroblast-like synoviocytes (FLS) were characterised in vitro and the effect of Rsk2 deletion on the pattern of gene expression was determined.
Results Rsk2 deficiency in TNFtg mice results in earlier and exacerbated inflammation as well as increased bone and cartilage destruction. The production of inflammatory cytokines, matrix metalloproteinases and osteoclastogenic molecules was significantly increased in vivo upon Rsk2 inactivation. Bone marrow deficient in Rsk2 could not transfer this phenotype, indicating that Rsk2 expression in mesenchymal cells controls the course of arthritis. Indeed, Rsk2 deficiency was associated with a more activated phenotype and higher proliferative capacity of FLS, thereby increasing cytokines and production of matrix proteinases.
Conclusions Rsk2 emerges as a key regulator of mesenchymal cell numbers in the joint and thereby could be targeted to control the inflammatory and tissue-destructive feature of joints in arthritis.
Annals of the Rheumatic Diseases 11/2014; DOI:10.1136/annrheumdis-2014-205618 · 10.38 Impact Factor
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