Regulation of immune cell trafficking by adhesion molecules and immune responses

免疫细胞运输的动态调节是免疫监测的核心。运动淋巴细胞是调节这一过程的基本成分。通过鉴定趋化因子和粘附分子，如LFA-1和a4整合素，我们对淋巴细胞运输的理解得到了促进，它们在通过内皮细胞和抗原识别介导转运中起重要作用。我们已经证明小的GTPase Rap1调节整合素介导的粘附并促进淋巴细胞的粘附反应和迁移。在这项研究中，我们发现一种新的Rap1效应物RAPL正调节由趋化因子和特异性抗原触发的整合素介导的粘附，依赖于RAPL。Rap1/RAPL信号协调调节整合素分布和细胞极性，从而产生淋巴细胞稳健迁移。我们进一步鉴定出Mstl （STK4）属于ste20相关的丝氨酸/苏氨酸激酶家族。RAPL与Rap1-GTP结合后，通过RAPL的…More coil -coil结构域与Mstl物理结合，增加Mstl激酶活性。趋化因子和TCR交联诱导活化Mstl介导的LFA-1表面聚集。RAPL和Mstl在蔗糖密度离心富集LFA-1和Rap1囊泡成分的轻密度室中单独共分离，提示RAPL和Mstl调节LFA-1胞内囊泡运输。为了研究RAPL信号在体内的生理作用，我们制造了RAPL缺陷小鼠。rapl缺陷淋巴细胞与高内皮细胞的稳定粘附缺陷，导致进入组织效率低下，导致继发淋巴结细胞增多。此外，我们发现树突状抗原呈递细胞大量表达RAPL。rapl缺陷皮肤树突状细胞在炎症时向引流淋巴结的迁移过程中受损。总之，我们证明RAPL信号在淋巴细胞和树突状细胞的体内运输中发挥关键作用，通过调节整合素介导的粘附行为来进行免疫监视。少

Dynamic regulation of immune cell trafficking is central to immuno-surveillance. Motile lymphocyte is a fundamental component regulating this process. Our understanding of lymphocyte trafficking has been facilitated by identification of chemokines and adhesion molecules such as LFA-1 and a4 integrins, which play important roles in mediating transmigration through endothelium and antigen recognition. We have shown that small GTPase Rap1 regulates integrin-mediated adhesion and promotes lymphocyte adhesive responses and migration. In this study, we showed that a novel Rap1 effector RAPL positively regulated integrin-mediated adhesion triggered by chemokines and specific antigen, depending on Rapl. Rap1/RAPL signaling coordinately regulates integrin distribution and cell polarity, thereby generates lymphocyte robust migration. We further identified Mstl (STK4) belonging to the Ste20-related serine/threonine kinase family. Upon binding to Rap1-GTP, RAPL physically bound to Mstl through the … More coiled-coil domain of RAPL, and increased Mstl kinase activities. Activated Mstl mediated LFA-1 surface clustering induced by chemokine and TCR crosslinking. RAPL and Mstl were exclusively co-fractionated in light-density compartments enrich for vesicle components containing LFA-1 and Rap1 by sucrose-density centrifugation, suggesting RAPL and Mstl regulate intracellular vesicle transport of LFA-1. In order to investigate physiological roles of RAPL signaling in vivo, we generated RAPL-deficient mice. RAPL-deficient lymphocytes were defective in stable adhesion to the high endothelium, leading to inefficient entry into tissues, resulting hypocellularity of secondary lymph nodes. In addition, we found that dendritic antigen-presenting cells abundantly expressed RAPL. RAPL-deficient skin dendritic cells were impaired in migration to draining lymph nodes upon inflammation. Collectively, we demonstrate that RAPL signaling plays critical roles in in vivo trafficking of lymphocytes and dendritic cells essential for immunosurveillance through regulating integrin-mediated adhesive behaviors. Less