The putative invertebrate adaptive immune protein Litopenaeus vannamei Dscam (LvDscam) is the first reported Dscam to lack a transmembrane domain and cytoplasmic tail
The putative invertebrate adaptive immune protein Litopenaeus vannamei Dscam (LvDscam) is the first reported Dscam to lack a transmembrane domain and cytoplasmic tail
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DOI：
10.1016/j.dci.2009.07.006
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发表时间：
2009-12-01
影响因子：
2.9
通讯作者：
Wang, K. C. Han-Ching
中科院分区：
文献类型：
--
作者：
Chou, Pin-Hsiang;Chang, Hao-Shuo;Wang, K. C. Han-Ching
Dscam（Down syndrome cell adhesion molecule，唐氏综合征细胞粘附分子）是免疫球蛋白超家族（IgSF）的成员，在无脊椎动物的适应性免疫系统中起着重要作用。本研究首次从凡纳滨对虾中分离到一种Dscam，并对其进行了鉴定。LvDscam蛋白具有胞外结构域，但缺乏预期的跨膜结构域和胞质尾区，这两者都存在于Dscam家族的所有其他成员中（也可能存在于其他L.尚未被隔离的vannamei Dscams）。在神经组织中，LvDscam的表达水平出乎意料地低。系统发育分析表明，LvDscam与其他无脊椎动物中发现的Dscams相距甚远。然而，LvDscam的胞外区的结构域结构与其他无脊椎动物Dscams相似，并且它表现出10个免疫球蛋白（IG）结构域、6个纤连蛋白3型结构域（FNIII）和一个细胞附着序列（RGD）的典型构型。从无WSSV、WSSV持续感染和WSSV急性感染的对虾血细胞中共克隆和鉴定了62个cDNA，在Ig 2的N-末端发现了23个替代氨基酸序列，在Ig 3的N-末端发现了30个，在Ig 7结构域发现了13个。这意味着LvDscam可以潜在地编码至少8970种独特的同种型。进一步的分析表明，LvDscam的Ig 2和Ig 3区域在对虾对WSSV的特异性免疫应答中比Ig 7更重要。我们讨论了这种无尾的可溶性Dscam如何在替代适应性免疫反应中发挥积极作用，即使其轴突引导功能可能受损。(C)2009爱思唯尔有限公司保留所有权利。
It has recently been suggested that Dscam (Down syndrome cell adhesion molecule), a member of the immunoglobulin superfamily (IgSF), plays an essential role in the alternative adaptive immune system of invertebrates. Here, we isolated and characterized the first shrimp Dscam from Litopenaeus vannamei. The LvDscam protein had an extracellular domain but lacked the expected transmembrane domain and cytoplasmic tail, both of which are found in all other members of the Dscam family (and may also be found in other L. vannamei Dscams that have not yet been isolated). In nervous tissue, expression levels of LvDscam were unexpectedly low. Phylogenetic analysis suggests that LvDscam is far from the Dscams found in other invertebrates. Nevertheless, the domain architecture of the extracellular region of LvDscam is similar to other invertebrate Dscams, and it exhibits the typical configuration of 10 immunoglobulin (Ig) domains, 6 fibronectin type 3 domains (FNIII) and one cell attachment sequence (RGD). Cloning and characterization of a total of 62 cDNAs from hemocytes collected from WSSV-free, WSSV-persistent and WSSV-acute-infected shrimp revealed 23 alternative amino acid sequences in the N-terminal of Ig2, 30 in the N-terminal of Ig3 and 13 in the Ig7 domain. This implies that LvDscam can potentially encode at least 8970 unique isoforms. Further analysis suggested that the LvDscam Ig2 and Ig3 regions are more functionally important than Ig7 in the shrimp's specific immune response against WSSV. We discuss how this tail-less, soluble Dscam can still play an active role in alternative adaptive immune response even while its axonal guidance functionality may be impaired. (C) 2009 Elsevier Ltd. All rights reserved.