角蛋白17的新功能：调控角质形成细胞的免疫活性

Keratinocytes(KCs), the predominant cell type in the epidermis, not only contribute to the physical barrier but also are involved in the "skin immune system" and modulate the local immune reaction. KC is one of immunocompetent cells. Many immune-related molecules, expressed by activated KCs, play a role in the local immune reaction in injury or psoriasis and so on. Keratin 17(K17), a Mr 46000 type I epithelial keratin, is overexpressed in activated KCs and is closely associated with the proliferation and migration of activated KCs. However, the relationship between K17 and the immunocompetent activity of KC is still unclear. Our previous studies demonstrate that K17 can up-regulate the expression of CXCL1 and CCL3 in the KCs, which suggests that K17 can modulate the immunocompetent activity of KC. In this study, we will investigate the function of K17 on modulating the immunocompetent activity of KC, observe the influence of K17 on CXCL1 and CCL3 expression，study the mechanism and inspect the effect of regulation on T cell chemotaxis and transformation through Real time PCR, ELISA, FCM, transwell co-culture model and SCID xenograft model. We suggest for the first time that K17 can indirectly regulate the local immune reaction types via modulating the immunocompetent activity of KCs basing on the immuno-modulation of cytoskeletal protein. It is very important for deeply understanding the function of keratins to observe the modulation of K17 on KCs and related signal transduction mechanisms and investigate the pathological significance of relationship between KCs and K17, which may provide a new direction for the research of keratins.

角蛋白一直被定义为上皮细胞的骨架蛋白，主要发挥维持细胞形态、参与细胞移行、保持细胞稳定的作用。然而，近年研究发现角蛋白可能具有其他重要生理功能，包括参与细胞信号转导、调控细胞增生分化等。我们近期研究发现，角蛋白家族成员之一的角蛋白17(K17)具有免疫调节活性，角质形成细胞表达K17水平的高低直接影响自身趋化因子产生、介导T细胞增殖活化等作用。本项目拟在此基础上进一步深入探讨K17的免疫调控作用，利用细胞和分子免疫学技术以及体外实验和动物实验手段，系统分析K17对角质形成细胞分泌细胞因子和趋化因子、表达免疫表型、发挥抗原提呈功能等的影响及其机制，从而揭示作为细胞骨架蛋白的K17在调节角质形成细胞免疫学活性中的地位和作用，为全面了解角质形成细胞的生物学特性及其病理生理学意义奠定基础。

角蛋白17（K17）是表达于复层上皮（包括甲、毛囊、皮脂腺和外泌汗腺）细胞的一类角蛋白。除了作为细胞骨架蛋白维持细胞的正常形态和功能外，越来越多的研究证明K17还具有调节细胞凋亡、增殖和蛋白合成等多种生物学行为的功能。前期在对银屑病的研究中发现，正常表皮不表达的K17分子在银屑病皮损的基底层以上的棘层细胞中特异性高表达，提示K17可能与银屑病的发生发展相关。同时，角质形成细胞表达K17水平的高低直接影响自身趋化因子产生、介导T细胞增殖活化等作用。本项目在前期基础上进一步探讨K17对KC的免疫调控作用，发现K17直接参与调节角质形成细胞的免疫活性，尤其是对免疫细胞的趋化作用；基因表达谱芯片结果发现IL-1β、CCL3、CCL4、CCL5、CXCL1、CXCL8、CXCL10及CXCL11等可能是K17调控的下游分子，其中对趋化因子CXCL1调控作用更为显著；组织和细胞学观察发现K17与CXCL1在银屑病患者皮损和细胞模型中的表达水平存在正相关性；进一步信号通路研究明确K17主要通过PI3K/AKT/NF-κB信号转导通路调控角质形成细胞中CXCL1的表达；Transwell小室趋化模型和银屑病异体移植模型明确K17可通过调节KC细胞CXCL1的表达继而影响中性粒细胞向皮肤局部的趋化作用。本项目揭示了作为细胞骨架蛋白的K17在调节角质形成细胞免疫学活性的重要作用，补充了银屑病发病早期中性粒细胞向表皮的趋化及微脓疡的形成的病理机制，有望为银屑病的治疗提供了新的靶点。