The keratin-desmosome scaffold as a signaling module during epithelial differentiation and wound healing

角蛋白-桥粒支架除了调节细胞间的黏附和抗力外，还通过与生长因子的串扰来调节表皮分化。分化、伤口愈合和发病机制需要在不同水平上重塑角蛋白桥粒复合体，以调节前者的强黏附和后者的弱黏附。角蛋白亚型在调控桥粒黏附、表皮分化和伤口愈合中的功能意义还不是很清楚。我们最近建立了一系列小鼠和角质形成细胞系，它们都缺乏或重新表达不同的角蛋白。他们的分析揭示了角蛋白在桥粒维持中的积极作用，影响角质形成细胞的迁移和侵袭。我们证明了Rack1 PKCA支架的角蛋白依赖的隔离介导了桥粒蛋白的磷酸化、细胞黏附和调节桥粒蛋白的内化。此外，我们发现Src的角蛋白同型依赖的激活是桥粒粘连的上游调节因子。这强烈地表明角蛋白在由内向外的信号传递中起着作用。我们假设角蛋白-桥粒支架作为信号节点，以角蛋白同种类型依赖的方式接收和调节生长因子信号，以控制细胞黏附、细胞信号传递和维持上皮细胞命运。我们的项目将阐明角蛋白同种类型通过调节桥粒黏附和周转来影响表皮分化和伤口愈合的主要机制。为了理解这一点，我们将剖析IGFR和EGFR信号之间的串扰以及角蛋白桥粒支架。长期目标是了解角蛋白-桥粒复合体在癌症发生和转移中的作用，以及癌基因和EMT激活剂如Snail和ZEB1对其调节。为了了解角蛋白-桥粒复合体在角质形成细胞分化和伤口愈合过程中的相互作用和调控，我们将进行以下主要目标：1.分析表皮分化和伤口愈合与角质形成细胞中角蛋白同种类型的关系以及它们与角质形成细胞中桥粒的相互作用；2.在体分析角蛋白缺陷小鼠的伤口愈合情况。角蛋白同型桥粒相互作用对IGF和EGF受体下游信号的响应4。角蛋白同型依赖的内向外调节Src激酶的剖析我们希望这个项目将对角蛋白同型在细胞黏附中的作用以及IGF和EGF对其的调节做出重大贡献。从长远来看，我们的数据将为伤口愈合和恶性转化/转移过程中角蛋白亚型对上皮细胞行为的各自贡献提供一个机制上的理解。它们将提供机会来影响上皮细胞的黏附、迁移和侵袭，通过在这种环境中靶向选择角蛋白同种类型。

TThe keratin-desmosome scaffold has a dual role in regulating epidermal differentiation through crosstalk with growth factors, in addition to mediating intercellular adhesion and force resistance. Differentiation, wound healing and pathogenesis require remodelling of the keratin desmosome complex at various levels to mediate strong adhesion in the former and weaker adhesion in the latter setting. The functional significance of keratin isotypes for the regulation of desmosomal adhesion, epidermal differentiation and wound healing is not well understood.We have recently established a series of mice and keratinocyte cell lines that lack all or re-express distinct sets of keratins. Their analysis has revealed an active role of keratins in desmosome maintenance impacting on keratinocyte migration and invasion. We demonstrated that keratin-dependent sequestration of a Rack1 PKCa scaffold mediates desmoplakin phosphorylation, cell adhesion and regulates desmosomal protein internalization. Further, we identified a keratin isotype dependent activation of Src as an upstream regulator of desmosomal adhesion. This strongly suggests a role of keratins in inside-out signaling. We hypothesize that the keratin-desmosome scaffold acts as signalling node which receives and modulates growth factor signals in a keratin isotype dependent manner to control cell adhesion, cell signalling and to maintain epithelial cell fate.Our project will elucidate major mechanisms by which keratin isotypes affect epidermal differentiation and wound healing through regulating desmosomal adhesion and turnover. To understand this, we will dissect the crosstalk between IGFR and EGFR signalling and the keratin desmosome scaffold. The long-term aim is to understand the role of the keratin-desmosome complex during carcinogenesis and metastasis and its regulation by oncogenes and EMT activators like snail and ZEB1. To understand the interaction and regulation of the keratin-desmosome complex during keratinocyte differentiation and wound healing, we will pursue the following major objectives:1. Analysis of epidermal differentiation and wound healing as a function of keratin isotypes and their interaction with desmosomes in keratinocytes 2. Wound healing analysis in keratin deficient mice in vivo3. Response of keratin isotype desmosome interactions to signalling downstream of the IGF and EGF receptor4. Dissection of keratin isotype-dependent inside out regulation of Src kinaseWe expect that this project will contribute significantly to the role of keratin isotypes in cell adhesion and its regulation by IGF and EGF. In the long run, our data will provide a mechanistic understanding for the respective contribution of keratin isotypes to epithelial cell behaviour during wound healing and malignant transformation/metastasis. They will provide the opportunity to affect epithelial cell adhesion, migration and invasion by targeting select keratin isotypes in such settings.