A γ-glutamyl transpeptidase of Aphidius ervi venom induces apoptosis in the ovaries of host aphids
A γ-glutamyl transpeptidase of Aphidius ervi venom induces apoptosis in the ovaries of host aphids
复制标题
DOI：
10.1016/j.ibmb.2007.02.005
复制
发表时间：
2007-05-01
影响因子：
3.8
通讯作者：
Pennacchio, Francesco
中科院分区：
文献类型：
--
作者：
Falabella, Patrizia;Riviello, Lea;Pennacchio, Francesco
内食茧蜂Aphidius ervi（Hypltera，Braconidae）的寄生对其寄主Acyrthosiphon pisitin（Homoptera，Aphididae）的生殖活动有负面影响。宿主去势是由寄生蜂毒液诱导的，并通过注射高度富集有两种蛋白质的色谱组分来复制，这两种蛋白质的大小分别为18（p18）和36 kDa（p36）。在这里，我们证明了这些生物活性蛋白触发宿主蚜虫生殖器和卵巢管鞘中的细胞凋亡。对p18和p36进行内部测序，并将收集的信息与从cDNA文库中随机选择的cDNA克隆编码的推定蛋白质的推导氨基酸序列进行匹配，所述cDNA文库使用从A. ervi毒腺鉴定的cDNA克隆含有一个插入片段，对应于一个中断基因的RNA产物，由6个外显子和5个内含子组成，发现该插入片段在A.比在mates。该基因编码由541个氨基酸组成的推定蛋白质，计算分子量为56.9 kDa，其中包含p18和p36实验确定的氨基酸序列。这种推定的蛋白质显示出与γ-谷氨酰转肽酶（γ-GT）的显著水平的序列同一性，并且它被命名为Ae-γ-GT。γ-GT是在谷胱甘肽（GSH）的代谢中起关键作用的酶，并且如在大多数生物体中观察到的，它们是由大小亚基形成的膜结合异二聚体，其起源于单链前体的翻译后加工。Ae-γ-GT在昆虫细胞中的表达证实了预期的翻译后加工的发生，并证明，与其他γ-GT不同，该蛋白质在细胞外环境中分泌。结果表明，在中华绒螯蟹毒液中检测到γ-GT活性。ervi和含有Ae-γ-GT的色谱组分中。因此，我们认为，这种毒液蛋白可能通过产生GSH代谢的改变和随之而来的氧化应激来诱导宿主卵巢细胞凋亡。(C)2007爱思唯尔有限公司版权所有。
Parasitism by the endophagous braconid Aphidius ervi (Hymenoptera, Braconidae) has a negative impact on the reproductive activity of its host, Acyrthosiphon pisitin (Homoptera, Aphididae). The host castration is induced by the parasitoid venom and is reproduced by the injection of chromatographic fractions highly enriched with two proteins, of 18 (p18) and 36 kDa (p36) in size, respectively. Here we demonstrate that these bioactive proteins trigger apoptosis of the cells in the germaria and ovariole sheath of the host aphid. Both p18 and p36 were internally sequenced and the gathered information was matched against the deduced amino acid sequence of the putative proteins encoded by cDNA clones, randomly selected from a cDNA library, which was raised using mRNA extracted from A. ervi venom glands. The identified cDNA clones contained an insert corresponding to the RNA product of an interrupted gene, made of six exons and five introns, which was found to be transcribed at higher levels in adult females of A. ervi than in mates. This gene codes for a putative protein composed of 541 amino acids, with a calculated molecular mass of 56.9 kDa, which contained the amino acid sequences experimentally determined for both p18 and p36. This putative protein showed a significant level of sequence identity with gamma-glutamyl transpeptidases (gamma-GT), and it was named Ae-gamma-GT. The gamma-GTs are enzymes which play a key role in the metabolism of glutathione (GSH) and, as observed in most organisms, they are membrane-bound heterodimers formed by a large and a small subunit, which originate by post-translational processing of a single-chain precursor. The expression in insect cells of Ae-gamma-GT confirmed the occurrence of the expected post-translational processing, and demonstrated that, unlike other gamma-GTs, this protein is secreted in the extracellular environment. A measurable gamma-GT activity was detected in the venom of A. ervi and in the chromatographic fractions containing Ae-gamma-GT. Thus, we suggest that this venom protein may induce apoptosis in the host ovarioles by generating an alteration of the GSH metabolism and a consequent oxidative stress. (C) 2007 Elsevier Ltd. All rights reserved.