A Novel Desmosomal COP9 Signalosome Complex in Epidermal Differentiation

表皮分化中的新型桥粒 COP9 信号体复合物

• 批准号: 8833750
• 负责人: Nicole Ann Najor
• 金额: $ 5.8万
• 依托单位: NORTHWESTERN UNIVERSITY AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2016-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8833750
• 关键词: Adherens Junction; Adhesions; Adhesives; Affect; Autoantibodies; Bacterial Toxins; Basal Cell; Binding; Biochemical; Biological; Biological Assay; Bulla; Cadherins; Cell Cycle; Cells; Code; Communication; Complex; Cullin Proteins; Cytoplasmic Protein; Cytoplasmic Tail; Cytoskeleton; Data; Dehydration; Desmosomes; Disease; EGFR inhibition; Ectopic Expression; Epidermal Growth Factor Receptor; Epidermis; Excision; Family; Family Dasypodidae; Family member; Gene Mutation; Genes; Immunoprecipitation; Impairment; Intermediate Filaments; Keratoderma; Ligase; MAP Kinase Gene; Maps; Measures; Mechanical Stress; Mechanics; Mediating; Membrane; Modification; Mutation; Organism; Pathogenesis; Pathway interactions; Phosphorylation; Post-Translational Protein Processing; Process; Proliferating; Proteins; Recruitment Activity; Role; Signal Transduction; Skin; Structure; Tail; Testing; Therapeutic; Tissues; Ubiquitin; Ubiquitination; Yeasts; attenuation; base; desmoglein 1; desmoplakin; experience; innovation; insight; interest; isopeptidase; keratinocyte; keratinocyte differentiation; knock-down; loss of function; member; microorganism; mutant; novel; programs; protein complex; protein degradation; public health relevance; receptor; scaffold; signalosome subunit 3; skin disorder; targeted treatment; therapeutic target; therapy design; trafficking; ubiquitin-protein ligase; yeast two hybrid system

 DESCRIPTION (provided by applicant): Desmosomes are intercellular adhesive junctions, which are required for integrity of tissues that experience mechanical stress, such as the epidermis. Their mechanical functions are facilitated by the linkage of the intermediate filament cytoskeleton to transmembrane desmosomal cadherins through a complex of cytoplasmic proteins in the armadillo and plakin families. It is known that disrupting desmosome structure and function through gene mutations, bacterial toxins or autoantibodies results in severe blistering disorders and keratodermas that have limited treatment options. However, the extent to which impairment of adhesion versus newly emerging signaling functions of desmosomes contributes to disease pathogenesis is unknown. It was recently shown that the cytoplasmic domain of the desmosomal cadherin Desmoglein 1 (Dsg1), which is first expressed as cells commit to differentiate, promotes epidermal differentiation by inhibiting EGFR/MAPK signaling. Towards elucidating the signaling role of the Dsg1 cytoplasmic tail in differentiation, a yeast two hybrid screen was performed. Among the putative binding partners identified by the screen was the COP9 signalosome subunit 3, Cops3. COP9 is complex of proteins, comprising eight subunits (Cops1-Cops8). This complex removes Nedd8 stabilizing protein modifications from cullin-RING ligases, to regulate activation cycles of cullin-RING ligases (which promote ubiquitination and degradation of proteins). The Nedd8 protein has also been shown to modify membrane receptors (e.g. EGFR), which can promote receptor stabilization. Ectopic expression of Dsg1 is known to promote epidermal differentiation through the suppression of EGFR signaling, but it is unable to do so in Cops3-deficient cells. This observation suggests that Dsg1 requires Cops3 to inhibit EGFR/MAPK and promote epidermal differentiation. Further, biochemical analyses revealed that Cops3 associates with both Dsg1 and the desmosomal plakin protein Desmoplakin (Dp), and that cullin family members (Cul3) associate with Dp. These data suggest that there is more than one interface for the desmosome to scaffold the COP9 signalosome for functioning. Based on these observations, it is hypothesized that the desmosome acts as a scaffold for the COP9 signalosome to de-neddylate cullins and EGFR, and promotes epidermal differentiation by inhibition of EGFR signaling. Aim1 will define the association between the COP9 signalosome and the desmosome, and the extent to which desmosome molecules affect COP9-dependent de-neddylation activity. Aim2 will determine how Cops3 assists in Dsg1- dependent differentiation by suppressing EGFR/MAPK signaling in epidermal keratinocytes. This project will provide insight into the functions of a novel desmosome-COP9 signaling complex and its role in epidermal differentiation. Understanding how desmosomes integrate mechanical and intracellular signaling will help identify new biological pathways as potential targets for therapeutics to treat the severe skin disorders associated with desmosomal impairment.

 描述(申请人提供)：桥粒是细胞间的粘连连接，对于承受机械应力的组织(如表皮)的完整性是必需的。它们的机械功能是通过中间丝细胞骨架与跨膜桥粒钙粘附素的连接，通过蝉和斑点蛋白家族的细胞质蛋白复合体来实现的。众所周知，通过基因突变、细菌毒素或自身抗体破坏桥粒结构和功能会导致严重的水泡性疾病和角皮病，治疗选择有限。然而，桥粒的黏附和新出现的信号功能的损害在多大程度上促进了疾病的发病机制尚不清楚。最近的研究表明，桥粒钙粘蛋白Desmoglein 1(DSG1)的胞质结构域通过抑制EGFR/MAPK信号通路促进表皮分化，DSG1首先在细胞承诺分化时表达。为了阐明DSG1胞质尾部在分化中的信号作用，进行了酵母双杂交筛选。在筛选出的可能的结合伙伴中，有COP9信号体亚单位3，Cops3。COP9是由8个亚基(Cops1-Cops8)组成的蛋白质复合体。这个复合体从cullin-环连接酶中去除稳定Nedd8的蛋白质修饰，以调节cullin-环连接酶的激活周期(促进蛋白质的泛素化和降解)。Nedd8蛋白也被证明可以修饰膜上的受体(例如EGFR)，这可以促进受体的稳定。已知DSG1的异位表达通过抑制EGFR信号而促进表皮分化，但在Cops3缺失的细胞中不能做到这一点。这表明DSG1需要Cops3来抑制EGFR/MAPK，促进表皮分化。进一步的生化分析表明，Cops3与DSG1和桥粒蛋白Desmoplakin(DP)相关，cullin家族成员(CUL3)与DP相关。这些数据表明，桥粒为COP9信号小体的功能搭建了不止一个界面。基于这些观察结果，推测桥粒作为COP9信号体的支架，通过抑制EGFR信号转导促进表皮分化。AIM1将定义COP9信号小体和桥粒之间的联系，以及桥粒分子影响COP9依赖的脱氢活性的程度。AIM2将通过抑制表皮角质形成细胞中的EGFR/MAPK信号来确定Cops3如何协助DSG1依赖的分化。这个项目将提供一个新的桥粒-COP9信号复合体的功能及其在表皮分化中的作用。了解桥粒如何整合机械信号和细胞内信号将有助于确定新的生物通路，作为治疗与桥粒损伤相关的严重皮肤病的潜在靶点。