MLCK细胞内转运及其调控肠上皮紧密连接通透性的机制研究

肌球蛋白轻链激酶（MLCK）调节紧密连接通透性和肠黏膜屏障功能，是炎症性肠病（IBD）发生的关键分子。抑制MLCK激酶活性可以保护肠黏膜屏障功能，抵抗IBD发生。然而，MLCK还具有维持平滑肌正常收缩等其他重要功能。MLCK活性抑制剂会产生肠麻痹、低血压等全身性不良反应，并不能用于临床上治疗IBD。我们前期研究发现，上皮MLCK的一个剪切异构体MLCK1，主要分布在紧密连接周围的肌动球蛋白环（PAMR），是行使MLCK依赖的紧密连接调控功能的主要分子。肿瘤坏死因子可诱导MLCK1从胞质向PAMR转运，增加紧密连接通透性。我们筛选到一种特异性结合MLCK1的小分子，它能够可阻遏MLCK1在细胞内的转运。本研究将进一步研究分子伴侣FKBP8协助MLCK1在细胞中转运的分子机制，探讨利用MLCK1转运阻遏剂治疗IBD的潜在能力。本研究有助于开发非免疫抑制类型的治疗炎症性肠病的药物。

Myosin light chain kinase (MLCK), which regulates intestinal epithelial tight junction barrier function, is the key molecule for the occurrence of inflammatory bowel disease (IBD). Inhibition of MLCK kinase activity protects intestinal barrier function and reduces progression of experimental inflammatory bowel disease. However, MLCK have other important biological functions such as maintaining normal smooth muscle contraction. MLCK inhibitors cannot be used for treatment of IBD, because inhibition of MLCK kinase activity causes systemic toxicities such as intestinal paralysis and hypotension. We have found that a splicing isoform of epithelial MLCK, MLCK1, which mainly distributes at the perijunctional actomyosin ring (PAMR), is responsible for the regulation of tight junction functions. Tumor necrosis factor induces the trafficking of MLCK1 to PAMR, thereby increasing the permeability of tight junctions. We identify a small molecule inhibitor which specifically binds to MLCK1, disrupts the trafficking of MLCK1 to PAMR. In this study, we will further investigate the molecular mechanism how a chaperone protein FKBP8 helps the trafficking of MLCK1 to PAMR in epithelial cells. We will also explore the potential use of MLCK1 trafficking inhibitors for the treatment of IBD. This study will provide fundamental knowledge for the development of new non-immune suppression drugs for IBD therapy.