RIP4 upregulates CCL20 expression through STAT3 signalling in cultured keratinocytes

Abstract

The receptor-interacting protein kinase 4 (RIP4), a serine/threonine kinase, is an important modulator of epidermal growth and cutaneous inflammation. We found that RIP4 expression was significantly increased in the lesional skin of psoriasis. However, the role and regulatory mechanism of RIP4 in psoriasis have not been characterized. After treatment with IL-17, RIP4 mRNA and protein levels were increased in HaCaT cells. IL-17 also activated the RIP4 promoter. To understand the functional role of RIP4 in keratinocyte and to investigate the genes regulated by RIP4, RNA-based microarray analysis was performed. Among immune response-related genes, CCL20 expression was significantly changed by RIP4. To identify RIP4-interacting protein, an immunoprecipitation assay was performed. As a result, STAT3 was identified as a new protein that interacts with RIP4. The interaction of RIP4 and STAT3 enhanced STAT3 phosphorylation. In addition, the transcriptional activity of STAT3 induced by RIP4 regulated IL-17-mediated CCL20 expression in HaCaT cells. Taken together, these findings indicate that IL-17 increased RIP4-mediated STAT3 phosphorylation by directly interacting with STAT3. Thus, transcriptional activation of STAT3 promotes the expression of CCL20. Thus, activations of these signalling pathways by RIP4 may contribute to epithermal inflammation in psoriatic keratinocytes.

Interleukin-17A and Keratinocytes in Psoriasis

“…Moreover, a STAT3 inhibitor STA-21 inhibits the generation of skin lesion in these psoriatic mice [102]. IL-17A is known to activate STAT3 via receptor-interacting protein 4 (RIP4) activation and upregulates the CCL20 expression [103]. IL-17A also upregulates keratin 17 expression via STAT1 and STAT3 activation [104].…”

Immune Control by TRAF6-Mediated Pathways of Epithelial Cells in the EIME (Epithelial Immune Microenvironment)

“…Despite a characteristic capacity of RIPK family members to bind to TRAF proteins, RIPK2 and RIPK4, but not RIPK1, interact with TRAF6 and get involved in TRAF6-mediated NF-κB and MAPK activation (174–177). Only a few reports have suggested a link between psoriasis and keratinocyte RIPK4 (178, 179) whereas RIPK2 might be involved in gut mucosal innate responses (31).…”

“…Consistently, the PMA-induced expression of proinflammatory mediators is inhibited by RIPK4 siRNA treatment in human keratinocytes (183). RIPK4 expression levels are higher in keratinocytes in psoriasis lesions than in healthy control skin, and stimulation with IL-17 induces RIPK4 expression in keratinocytes (178, 179). In addition, RIPK4 interacts with STAT3 and enhances IL-17-mediated STAT3 phosphorylation and CCL20 expression in HaCaT cells.…”

Rola białka RIPK4 w fizjologii naskórka.

“…Kinaza RIPK4 prawdopodobnie jest zaangażowana w akty-wację kinazy JNK [18]. Badania na keratynocytach wykazały, że stymulowanie komórek interleukiną 17 (IL17) powoduje wzrost ekspresji RIPK4, który z kolei prowadzi do aktywacji czynnika transkrypcyjnego STAT3 indukującego ekspresje chemokin takich jak CCL20, CXCL1, CXCL2, CXCL8, CXCL10, przy czym najwyższy wzrost obserwuje się dla CCL20 [28,29]. Prawdopodobnie kinaza RIPK4 może fizycznie i funkcjonalnie oddziaływać rodziną białek adaptorowych zależnych od TNF (TRAF), które również prowadzą do aktywacji ścieżki sygnalnej NFκB czy JNK.…”