Abstract：
Epidermolytic palmoplantar keratoderma (EPPK), a highly penetrant autosomal dominant genodermatosis, is characterized by diffuse keratoses on palmplantar epidermis. The keratin 9 gene (KRT9) is responsible for EPPK. To date, phenotypic therapy is the primary treatment for EPPK. Because KRT9 pairs with a type II keratin-binding partner to function in epidermis, identifying the interaction partner is an essential first step in revealing EPPK pathogenesis and its fundamental treatment. In this study, we proved that keratin 6C (KRT6C) is a probable hereterodimer partner for KRT9. In silico model for KRT6C/KRT9 shows a typical coiled-coil structure in their 2B domains. Proteomics analysis shows that KRT6C/KRT9 pair is in a densely connected protein-protein interaction network, where proteins participate jointly in regulating cytoskeleton organization and keratinization. This study shows that co-immunoprecipitation coupled with mass spectroscopy and proteomics analysis provide a sensitive approach, which compensates for inevitable inadequacies of anti-keratin 6C antibody and helps discover the probable hereterodimer partner KRT6C for KRT9. The acknowledgement of KRT6C/KRT9 pairwise relationship may help re-classify EPPK and PC-K6c (a milder form of pachyonychia congenita, caused by KRT6C) as a group of hereditary defects at a molecular-based level, and lay foundation for deciphering the keratin network contributing to EPPK and PC-K6c. SIGNIFICANCE OF THE STUDY: What is already known about this topic? KRT9 and KRT6C are disease-causing factors for epidermolytic palmoplantar keratoderma (EPPK) and a milder form of pachyonychia congenita (PC-K6c), respectively. EPPK and PC-K6c have some symptom similarities. Keratins are the major structural proteins in epithelial cells. Each of the type I keratin is matched by a particular type II keratin to assemble a coiled-coil heterodimer. The hereterodimer partner for KRT9 is unknown. What does this study add? We discovered and proved that KRT6C is a probable hereterodimer partner for KRT9 in palmplantar epidermis in a native endogenous environment by using co-immunoprecipitation coupled with mass spectroscopy and proteomics analysis, etc. The proteomics analysis shows that KRT6C/KRT9 keratin pair is in a densely connected protein-protein interaction network, where proteins participate jointly in regulating intermediate filament-based cytoskeleton organization and keratinization processes. What are the implications of this work? The new understanding of probable KRT6C/KRT9 pairwise correlation may help re-classify the genetic cutaneous disorders EPPK and PC-K6c as a group of hereditary defects at a molecular-based level, and lay foundation for pathogenic mechanism research in EPPK and PC-K6c. The densely related network components derived from the proteomic data using Metascape in the study and pairwise regulation fashion of specific keratin pairs should attract more attention in the further explorations when investigators concern the physiological functions of keratins and the pathogenesis of related skin diseases.
摘要：
表皮松解性掌底角化病(EPPK),一种高度渗透的常染色体显性遗传皮肤病，其特征在于掌底表皮上的弥漫性角化病。角蛋白9基因(KRT9)负责EPPK。迄今为止,表型治疗是EPPK的主要治疗方法。因为KRT9与II型角蛋白结合伴侣配对在表皮中发挥作用，识别相互作用伴侣是揭示EPPK发病机制及其基本治疗的重要第一步。在这项研究中,我们证明角蛋白6C（KRT6C）是KRT9的可能的外二聚体伴侣。KRT6C/KRT9的计算机模拟模型在其2B结构域中显示了典型的卷曲螺旋结构。蛋白质组学分析表明,KRT6C/KRT9对处于紧密相连的蛋白质-蛋白质相互作用网络中,蛋白质共同参与调节细胞骨架组织和角质化。这项研究表明，免疫共沉淀结合质谱和蛋白质组学分析提供了一种灵敏的方法，它弥补了抗角蛋白6C抗体不可避免的不足，并有助于发现KRT9的可能的遗传二聚体伴侣KRT6C。确认KRT6C/KRT9成对关系可能有助于重新分类EPPK和PC-K6c（一种较温和的先天性白甲癣，由KRT6C引起)作为一组基于分子水平的遗传性缺陷，并为破译有助于EPPK和PC-K6c的角蛋白网络奠定基础。KRT9和KRT6C是表皮松解性掌底角化病（EPPK）和一种较温和形式的先天性白质甲癣（PC-K6c）的致病因素，分别。EPPK和PC-K6c有一些症状相似性。角蛋白是上皮细胞中的主要结构蛋白。每种I型角蛋白与特定的II型角蛋白匹配以组装卷曲螺旋异型二聚体。KRT9的eresterdimer伴侣未知。这项研究增加了什么？通过使用免疫共沉淀结合质谱和蛋白质组学分析，我们发现并证明了KRT6C是天然内源性环境中掌底表皮中KRT9的可能的遗传二聚体伴侣，等。蛋白质组学分析表明,KRT6C/KRT9角蛋白对处于紧密相连的蛋白质-蛋白质相互作用网络中,其中蛋白质共同参与调节中间丝的细胞骨架组织和角质化过程。这项工作的意义是什么？对可能的KRT6C/KRT9成对相关性的新理解可能有助于将遗传性皮肤疾病EPPK和PC-K6c重新分类为一组基于分子水平的遗传性缺陷，为EPPK和PC-K6c的致病机制研究奠定基础。当研究人员关注角蛋白的生理功能和相关皮肤病的发病机理时，在研究中使用Metascape和特定角蛋白对的成对调节方式的蛋白质组学数据得出的密集相关网络成分应在进一步的探索中引起更多关注。
