Nombela-Arrieta César, Mempel Thorsten R, Soriano Silvia F, Mazo Irina, Wymann Matthias P, Hirsch Emilio, Martínez-A Carlos, Fukui Yoshinori, von Andrian Ulrich H, Stein Jens V
Theodor Kocher Institute, University of Bern, CH-3012 Bern, Switzerland.
J Exp Med. 2007 Mar 19;204(3):497-510. doi: 10.1084/jem.20061780. Epub 2007 Feb 26.
Recent observations using multiphoton intravital microscopy (MP-IVM) have uncovered an unexpectedly high lymphocyte motility within peripheral lymph nodes (PLNs). Lymphocyte-expressed intracellular signaling molecules governing interstitial movement remain largely unknown. Here, we used MP-IVM of murine PLNs to examine interstitial motility of lymphocytes lacking the Rac guanine exchange factor DOCK2 and phosphoinositide-3-kinase (PI3K)gamma, signaling molecules that act downstream of G protein-coupled receptors, including chemokine receptors (CKRs). T and B cells lacking DOCK2 alone or DOCK2 and PI3Kgamma displayed markedly reduced motility inside T cell area and B cell follicle, respectively. Lack of PI3Kgamma alone had no effect on migration velocity but resulted in increased turning angles of T cells. As lymphocyte egress from PLNs requires the sphingosine-1-phosphate (S1P) receptor 1, a G(alphai) protein-coupled receptor similar to CKR, we further analyzed whether DOCK2 and PI3Kgamma contributed to S1P-triggered signaling events. S1P-induced cell migration was significantly reduced in T and B cells lacking DOCK2, whereas T cell-expressed PI3Kgamma contributed to F-actin polymerization and protein kinase B phosphorylation but not migration. These findings correlated with delayed lymphocyte egress from PLNs in the absence of DOCK2 but not PI3Kgamma, and a markedly reduced cell motility of DOCK2-deficient T cells in close proximity to efferent lymphatic vessels. In summary, our data support a central role for DOCK2, and to a lesser extent T cell-expressed PI3Kgamma, for signal transduction during interstitial lymphocyte migration and S1P-mediated egress.
最近利用多光子活体显微镜（MP-IVM）进行的观察发现，外周淋巴结（PLN）内淋巴细胞的运动性出人意料地高。而调控淋巴细胞间质运动的细胞内信号分子仍 largely未知。在这里，我们利用小鼠PLN的MP-IVM来研究缺乏Rac鸟嘌呤交换因子DOCK2和磷酸肌醇-3-激酶（PI3K）γ的淋巴细胞的间质运动性，这些信号分子在G蛋白偶联受体（包括趋化因子受体（CKR））的下游起作用。单独缺乏DOCK2或同时缺乏DOCK2和PI3Kγ的T细胞和B细胞分别在T细胞区和B细胞滤泡内显示出明显降低的运动性。单独缺乏PI3Kγ对迁移速度没有影响，但导致T细胞的转向角度增加。由于淋巴细胞从PLN流出需要1-磷酸鞘氨醇（S1P）受体1，这是一种与CKR类似的G（αi）蛋白偶联受体，我们进一步分析了DOCK2和PI3Kγ是否参与S1P触发的信号事件。在缺乏DOCK2的T细胞和B细胞中，S1P诱导的细胞迁移显著减少，而T细胞表达的PI3Kγ有助于F-肌动蛋白聚合和蛋白激酶B磷酸化，但不参与迁移。这些发现与在缺乏DOCK2但不缺乏PI3Kγ的情况下淋巴细胞从PLN流出延迟以及靠近输出淋巴管的DOCK2缺陷型T细胞的细胞运动性显著降低相关。总之,我们的数据支持DOCK2在间质淋巴细胞迁移和S1P介导的流出过程中的信号转导中起核心作用，而T细胞表达的PI3Kγ在较小程度上也起作用。
