Receptor-interacting Protein Kinase 4 and Interferon Regulatory Factor 6 Function as a Signaling Axis to Regulate Keratinocyte Differentiation
Receptor-interacting Protein Kinase 4 and Interferon Regulatory Factor 6 Function as a Signaling Axis to Regulate Keratinocyte Differentiation
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DOI：
10.1074/jbc.m114.589382
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发表时间：
2014-11-07
影响因子：
4.8
通讯作者：
Scholz, Glen M.
中科院分区：
文献类型：
--
作者：
Kwa, Mei Qi;Huynh, Jennifer;Scholz, Glen M.
受体相互作用蛋白激酶4（RIPK 4）和干扰素调节因子6（IRF 6）是角质形成细胞分化的关键调节因子，它们的突变分别导致相关的发育性表皮疾病Bartsocas-Papas综合征和腘翼状胬肉综合征。然而，RIPK 4和IRF 6调节角质形成细胞分化的信号传导途径尚不清楚。在这里，我们确定和机械定义RIPK 4和IRF 6之间的直接功能关系。基因启动子报告和体外激酶测定，共免疫沉淀实验，共聚焦显微镜表明，RIPK 4直接调节IRF 6反式激活剂活性和核转位。基因敲低和过表达研究表明，RIPK 4-IRF 6信号轴控制角质形成细胞分化的关键转录调节因子的表达，包括Grainyhead样3和OVO样1。此外，我们证明了最近在Bartsocas-Papas综合征中发现的RIPK 4中的p.Ile121Asn错义突变抑制了其激酶活性，从而阻止了RIPK 4介导的IRF 6激活和核转位。我们通过基于诱变的实验表明，IRF 6中的Ser-413和Ser-424对其被RIPK 4激活很重要。RIPK 4对于通过蛋白激酶C途径调节IRF 6表达也很重要。因此，我们的研究结果不仅提供了重要的角质形成细胞分化的RIPK 4和IRF 6的调节机制的见解，但他们也提出了一种机制，其中RIPK 4的突变可能会导致表皮疾病（如Bartsocas-Papas综合征），即通过受损的RIPK 4激活IRF 6。
Receptor-interacting protein kinase 4 (RIPK4) and interferon regulatory factor 6 (IRF6) are critical regulators of keratinocyte differentiation, and their mutation causes the related developmental epidermal disorders Bartsocas-Papas syndrome and popliteal pterygium syndrome, respectively. However, the signaling pathways in which RIPK4 and IRF6 operate to regulate keratinocyte differentiation are poorly defined. Here we identify and mechanistically define a direct functional relationship between RIPK4 and IRF6. Gene promoter reporter and in vitro kinase assays, coimmunoprecipitation experiments, and confocal microscopy demonstrated that RIPK4 directly regulates IRF6 trans-activator activity and nuclear translocation. Gene knockdown and overexpression studies indicated that the RIPK4-IRF6 signaling axis controls the expression of key transcriptional regulators of keratinocyte differentiation, including Grainyhead-like 3 and OVO-like 1. Additionally, we demonstrate that the p.Ile121Asn missense mutation in RIPK4, which has been identified recently in Bartsocas-Papas syndrome, inhibits its kinase activity, thereby preventing RIPK4-mediated IRF6 activation and nuclear translocation. We show, through mutagenesis-based experiments, that Ser-413 and Ser-424 in IRF6 are important for its activation by RIPK4. RIPK4 is also important for the regulation of IRF6 expression by the protein kinase C pathway. Therefore, our findings not only provide important mechanistic insights into the regulation of keratinocyte differentiation by RIPK4 and IRF6, but they also suggest one mechanism by which mutations in RIPK4 may cause epidermal disorders (e.g. Bartsocas-Papas syndrome), namely by the impaired activation of IRF6 by RIPK4.