Regulation and function of cytoskeleton reorganization by signaling molecules in hematopoietic cells.

细胞骨架重组在多种细胞中调节细胞极性、迁移和信号转导，但其在造血细胞中的确切作用尚不清楚。在本研究中，我们重点研究了细胞骨架重组分子，如DOCK2、Vavl和SLAT在造血细胞活化中的调控和功能。我们发现DOCK2缺乏导致胸腺、肝脏和脾脏中Val4 NKT细胞的显著减少。利用骨髓嵌合体的研究表明，Val4 NKT细胞的发育需要在T细胞前体中表达DOCK2，而在apc中不需要。我们还报道了DOCK2调节中性粒细胞趋化过程中的运动性和极性。在缺乏dock2的中性粒细胞中，化学引诱剂诱导的Rac1和Rac2的激活严重受损，导致前沿F-actin和磷脂酰肌醇3,4,5-三磷酸（pip3）的极化积累丧失。这些结果表明，在中性粒细胞趋化过程中，DOCK2通过pip3依赖的膜易位和Rac激活来调节前缘的形成。此外，我们发现IL-4和c-Maf表达选择性地需要Vavl，这一要求至少部分反映了c-Maf表达对Ca^<2+>/NFAT信号的依赖性。最后，我们发现SLAT通过控制Ca^<2+>/NFAT信号通路调节Th1和Th2肺部炎症反应。因此，我们展示了几个关键方面的细胞骨架重组造血细胞使用生化和遗传方法的组合。未来的工作应该旨在确定这些分子调节细胞骨架重组功能的确切机制。

Cytoskeleton reorganization regulates cell polarity, migration and signal transduction in various cells, but the precise role in hematopoietic cells is still unclear. In this study, we focused on several aspects of the regulation and function of cytoskeleton reorganization molecules, such as DOCK2,Vavl, and SLAT, in hematopoietic cell activation. We found that DOCK2 deficiency causes marked reduction of Val4 NKT cells in the thymus, liver, and spleen. Studies using bone marrow chimeras indicated that development of Val4 NKT cell requires DOCK2 expression in T cell precursors, but not in APCs. We also reported that DOCK2 regulates motility and polarity during neutrophil chemotaxis. In DOCK2-deficient neutrophils, chemoattractant-induced activation of both Rac1 and Rac2 were severely impaired, resulting in the loss of polarized accumulation of F-actin and phosphatidylinositol 3,4,5-triphosphate (PIP_3) at the leading edge. These results indicate that during neutrophil chemotaxis DOCK2 regulates leading edge formation through PIP_3-dependent membrane translocation and Rac activation. In addition, we showed that Vavl is selectively required for IL-4 and c-Maf expression, a requirement reflecting, at least in part, the dependence of c-Maf expression of Ca^<2+>/NFAT signaling. Finally, we found that SLAT regulates Th1 and Th2 lung inflammatory responses by controlling Ca^<2+>/NFAT signaling. Thus, we demonstrated several critical aspects for cytoskeleton reorganization in hematopoietic cells using a combination of biochemical and genetic approaches. Future work should be aimed at defining the precise mechanisms through which these molecules regulate the function of cytoskeleton reorganization.