Analysis of signal transduction pathway in blistering mechanism of pemphigus vulgaris

在这项研究中，我们研究了AK23单抗是否增强了人鳞状细胞系DJM-1细胞中Dsg3和p38丝裂原激活蛋白激酶(MAPK)的磷酸化。接下来，我们研究了p120ctn与桥粒芯糖蛋白(Dsg)1和3的结合。不含细胞内锚定(IA)区域的无尾Dsg3结构IA：AA1-641Dsg3和641-714Dsg3不与p120cn共沉淀，也不在质膜上共定位。免疫细胞化学分析表明，p120ctn不定位于桥粒，但与Dsg3共定位于细胞表面。Dsg3的生物素化实验表明，生物素标记的641-714Dsg3的翻转速度比野生型Dsg3快。这些结果表明，Dsg3 IA区的膜近端区域(对应于残基641-714)是与p120ctn形成复合体所必需的，也是在细胞表面保持游离Dsg3才能整合到桥粒中所必需的。综上所述，我们发现p120ctn是DSG蛋白的一个新的相互作用因子，并可能在桥粒重塑中发挥作用。

In this study, we examined whether AK23 mAb augments phosphorylation of Dsg3 and p38 mitogen-activating protein kinase (MAPK) in a human squamous cell line, DJM-1 cells.AK23 mAb increased serine phosphorylation of Dsg3 and augmented activation levels of p38 MAPK. These results indicate that antibodies bind to Dsg3, but not other antigens, in the IgG fraction and can induce activation of signal transduction.Next, we investigated that p120ctn binds to desmoglein (Dsg) 1 and 3. The tailless Dsg3 constructs △IA:AA1-641Dsg3 and △641-714Dsg3, which do not contain the intracellular anchor (IA) region, did not coprecipitate with p120cn, nor did they colocalize at the plasma membrane. Immunocytochemical analysis revealed that p120ctn does not localize to desmosomes, but co-localizes with Dsg3 at the cell surface. A biotinylation assay for Dsg3 showed that biotinylated △ 641-714Dsg3 was turned over more rapidly than wild-type Dsg3. These results indicate that the membrane proximal region (corresponding to residues 641-714) in the IA region of Dsg3 is necessary for complex formation with p120ctn, and to maintain free Dsg3 at the cell surface before it is integrated into desmosomes. In summary, we show that p120ctn is a novel interactor of the Dsg proteins, and may play a role in desmosome remodeling.