Vav family guanine nucleotide exchange factors (GEFs) are essential regulators of immune function. Despite their structural similarity, Vav1 promotes and Vav2 opposes T cell receptor (TCR)-induced calcium entry. Using a Vav1-deficient Jurkat T cell line, we find that Vav1 facilitates calcium entry via non-catalytic scaffolding functions that are encoded by the catalytic core of Vav1 and flanking linker regions. We implicate in this scaffolding function a previously undescribed polybasic motif that is strictly conserved in Vav1 and absent from Vav2 in tetrapods. Conversely, the catalytic activity of Vav2 contributes to the suppression of TCR-mediated calcium entry. Using an in vivo 'GEF trapping' assay in intact cells, we demonstrate that Cdc42 interacts with the catalytic surface of Vav2 but not Vav1, and that Vav1 discriminates Cdc42 from Rac1 via F56 (W56 in Rac1). Lastly, the Cdc42-specific inhibitor ZCL278 and the shRNA-mediated suppression of Cdc42 each prevent the inhibition of TCR-induced calcium entry by Vav2. These findings define stark differences in the functions of Vav1 and Vav2 and provide an explanation for the differential usage of these Vav isoforms by immune subpopulations.

中文翻译：

---

Vav2 缺乏 Vav1 特有的促进 Ca2+ 进入的支架功能，并通过 Cdc42 抑制 T 细胞激活。

Vav 家族鸟嘌呤核苷酸交换因子 (GEF) 是免疫功能的重要调节因子。尽管结构相似，Vav1 促进 T 细胞受体 (TCR) 诱导的钙进入，而 Vav2 则反对 T 细胞受体 (TCR) 诱导的钙进入。使用 Vav1 缺陷的 Jurkat T 细胞系，我们发现 Vav1 通过非催化支架功能促进钙进入，这些功能由 Vav1 的催化核心和侧翼连接区编码。我们在这种支架功能中暗示了一个先前未描述的多元基序，该基序在四足动物的 Vav1 中严格保守，而在 Vav2 中不存在。相反，Vav2 的催化活性有助于抑制 TCR 介导的钙进入。在完整细胞中使用体内“GEF 捕获”测定，我们证明 Cdc42 与 Vav2 的催化表面相互作用，但不与 Vav1 相互作用，并且 Vav1 通过 F56（Rac1 中的 W56）区分 Cdc42 和 Rac1。最后，Cdc42 特异性抑制剂 ZCL278 和 shRNA 介导的 Cdc42 抑制各自阻止 Vav2 对 TCR 诱导的钙进入的抑制。这些发现明确了 Vav1 和 Vav2 功能的明显差异，并为免疫亚群对这些 Vav 亚型的差异使用提供了解释。