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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Adaptor protein is essential for insect cytokine signaling in hemocytes
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Adaptor protein is essential for insect cytokine signaling in hemocytes

机译：衔接蛋白对于血细胞中昆虫细胞因子的信号传导至关重要

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摘要

Growth-blocking peptide (GBP) is an insect cytokine that stimulates a class of immune cells called plasmatocytes to adhere to one another and to foreign surfaces. Although extensive structure-activity studies have been performed on the GBP and its mutants in Lepidoptera Pseudaletia separata, the signaling pathway of GBP-dependent activation of plasmatocytes remains unknown. We identified an adaptor protein (P77) with a molecular mass of 77 kDa containing SH2/SH3 domain binding motifs and an immunoreceptor tyrosine-based activation motif (ITAM)-like domain in the cytoplas-mic region of the C terminus. Although P77 showed no capacity for direct binding with GBP, its cytoplasmic tyrosine residues were specifically phosphorylated within seconds after GBP was added to a plasmatocyte suspension. Tyrosine phosphorylation of P77 also was observed when hemocytes were incubated with Enterobactor cloacae or Micrococcus luteus, but this phosphorylation was found to be induced by GBP released from hemocytes stimulated by the pathogens. Tyrosine phosphorylation of the integrin β subunit also was detected in plasmatocytes stimulated by GBP. Double-stranded RNAs targeting P77 not only decreased GBP-dependent tyrosine phosphorylation of the integrin β subunit, but also abolished GBP-induced spreading of plasmatocytes on foreign surfaces. P77 RNAi larvae also showed significantly higher mortality than control larvae after infection with Serratia marcescens, indicating that P77 is essential for GBP to mediate a normal innate cellular immunity in insects. These results demonstrate that GBP signaling in plasmatocytes requires the adaptor protein P77, and that active P77-assisted tyrosine phosphorylation of integrins is critical for the activation of plasmatocytes.
机译：生长阻断肽（GBP）是一种昆虫细胞因子，可刺激一类称为浆细胞的免疫细胞相互粘附并粘附至异物表面。尽管已经对鳞翅目鳞翅目中的GBP及其突变体进行了广泛的结构活性研究，但是GBP依赖的浆细胞激活的信号传导途径仍然未知。我们确定了一个接头蛋白（P77），其分子量为77 kDa，在C端的胞质区域中包含SH2 / SH3域结合基序和一个基于免疫受体酪氨酸的活化基序（ITAM）样结构域。尽管P77没有显示出与GBP直接结合的能力，但是在将GBP加入浆细胞悬浮液后的数秒内，其细胞质酪氨酸残基被特异性磷酸化。当将血细胞与阴沟肠杆菌或黄斑微球菌一起孵育时，也观察到P77的酪氨酸磷酸化，但是发现这种磷酸化是由病原体刺激的血细胞释放的GBP诱导的。在GBP刺激的浆细胞中也检测到整联蛋白β亚基的酪氨酸磷酸化。靶向P77的双链RNA不仅降低了整联蛋白β亚基的GBP依赖性酪氨酸磷酸化，而且消除了GBP诱导的异质表面浆细胞的扩散。粘质沙雷氏菌感染后，P77 RNAi幼虫的死亡率也显着高于对照幼虫，这表明P77对于GBP介导昆虫的正常先天细胞免疫至关重要。这些结果表明，浆细胞中的GBP信号传导需要衔接蛋白P77，而整联蛋白的活性P77辅助酪氨酸磷酸化对于浆细胞的激活至关重要。

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