Institute of Biotechnology, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan 701, Taiwan.
Fish Shellfish Immunol. 2013 Oct;35(4):1272-81. doi: 10.1016/j.fsi.2013.07.045. Epub 2013 Aug 9.
Arthropod Down syndrome cell adhesion molecules (Dscam) may sometimes function as hypervariable pathogen recognition receptors. They consist of an extracellular region and a cytoplasmic tail, both of which are highly variable. In shrimp, tail-less Dscam proteins (Dscams) have recently been identified, and these appear to be unlike other arthropod extracellular Dscams that are released from the cell membrane by proteolytic cleavage. Here we investigate the properties of these unique shrimp proteins and show that they can be directly secreted from transfected cells. We also investigate the diverse cytoplasmic tail variants of membrane-bound shrimp Dscams, and show that elements E1A and E3 seem to be related to Dscam immune function. Challenge with Vibrio harveyi not only enhanced total Dscam and the immune-related cytoplasmic tail variants, but also induced expression of certain Ig2 + Ig3 combinations. A pathogen binding assay with these Ig2 + Ig3 extracellular variants showed that both the V. harveyi-induced Dscams and Dscams induced by buffer injection could be either pathogen-specific or specific only for Gram-negative pathogens, while other "general" Dscam variants were sensitive to a wide range of pathogens. The same assay also suggested that shrimp Dscam isoforms show a stronger response to the host's natural pathogens.
节肢动物 Down 综合征细胞黏附分子 (Dscam) 有时可能作为高变异性病原体识别受体发挥作用。它们由细胞外区和细胞质尾组成，这两个区域都具有高度的可变性。在虾类中，最近已经鉴定出无尾 Dscam 蛋白 (Dscams)，这些蛋白似乎与其他通过蛋白水解切割从细胞膜释放的甲壳动物细胞外 Dscam 不同。在这里，我们研究了这些独特虾类蛋白的特性，并表明它们可以直接从转染细胞中分泌。我们还研究了膜结合虾类 Dscam 的不同细胞质尾变体，并表明 E1A 和 E3 元件似乎与 Dscam 免疫功能有关。哈维弧菌的挑战不仅增强了总 Dscam 和与免疫相关的细胞质尾变体，还诱导了某些 Ig2+Ig3 组合的表达。对这些 Ig2+Ig3 细胞外变体的病原体结合测定表明，V. harveyi 诱导的 Dscam 和缓冲液注射诱导的 Dscam 都可以是病原体特异性的或仅对革兰氏阴性病原体特异性，而其他“通用”Dscam 变体对广泛的病原体敏感。相同的测定还表明，虾类 Dscam 同工型对宿主的天然病原体表现出更强的反应。
