Williams Michael J, Ando Istvan, Hultmark Dan
Umeå Centre for Molecular Pathogenesis, Umeå University, S-901 87 Umeå, Sweden.
Genes Cells. 2005 Aug;10(8):813-23. doi: 10.1111/j.1365-2443.2005.00883.x.
It has been reported that during Drosophila embryonic development, and in cell culture, that the Rac GTPases are redundant. To better elucidate Rac function in Drosophila, we decided to study the role of Rac2 in larval cellular defense reactions against the parasitiod Leptopilina boulardi. Here we show a dramatic effect in the context of cellular immunity where, unlike embryonic development, Rac2 appears to have a non-redundant function. When an invading parasitoid is recognized as foreign, circulating hemocytes (blood cells) should recognize and attach to the egg chorion. After attachment the hemocytes should then spread to form a multilayered capsule surrounding the invader. In Rac2 mutants this process is disrupted. Immune surveillance cells, known as plasmatocytes, adhere to the parasitoid egg but fail to spread, and septate junctions do not assemble, possibly due to mislocalization of the Protein 4.1 homolog Coracle. Finally, larger cells known as lamellocytes attach to the capsule but also fail to spread, and there is a lack of melanization. From these results it appears that Rac2 is necessary for the larval cellular immune response.
据报道，在果蝇胚胎发育过程中以及细胞培养中，Rac GTPases具有冗余性。为了更好地阐明Rac在果蝇中的功能，我们决定研究Rac2在幼虫针对寄生蜂巴氏丽蝇的细胞防御反应中的作用。在这里，我们展示了在细胞免疫背景下的显著效应，与胚胎发育不同，Rac2似乎具有非冗余功能。当入侵的寄生蜂被识别为外来物时，循环血细胞（血细胞）应识别并附着在卵壳上。附着后，血细胞应扩散形成围绕入侵者的多层胶囊。在Rac2突变体中，这个过程被破坏。被称为浆血细胞的免疫监视细胞附着在寄生蜂卵上但未能扩散，并且隔膜连接未组装，这可能是由于蛋白质4.1同源物Coracle的定位错误。最后，被称为片层细胞的较大细胞附着在胶囊上但也未能扩散，并且缺乏黑化现象。从这些结果看来，Rac2对于幼虫的细胞免疫反应是必需的。
