Invasion of insect cells by Spiroplasma citri involves spiralin relocalization and lectin/glycoconjugate-type interactions
Invasion of insect cells by Spiroplasma citri involves spiralin relocalization and lectin/glycoconjugate-type interactions
复制标题
DOI：
10.1111/cmi.12265
复制
发表时间：
2014-07-01
影响因子：
3.4
通讯作者：
Arricau-Bouvery, Nathalie
中科院分区：
文献类型：
--
作者：
Duret, Sybille;Batailler, Brigitte;Arricau-Bouvery, Nathalie
螺原体是螺旋状、无细胞壁的细菌，属于软体纲，是一组在系统发育上与低 G+C 革兰氏阳性细菌相关的微生物。所有螺原体物种均与节肢动物有关，其中包括柑橘螺原体在内的少数螺原体对植物具有致病性。因此，柑橘链霉菌具有定植两种截然不同的宿主（植物和昆虫载体）的细胞的能力。虽然已鉴定出参与叶蝉圆叶蝉传播的螺原体因子，但它们对昆虫细胞入侵的具体贡献却知之甚少。在这项研究中，我们提供的证据表明脂蛋白螺旋蛋白在细胞侵袭的早期阶段发挥着重要作用。共焦激光扫描免疫显微镜显示螺旋蛋白在粘附螺旋原体的接触区重新定位。螺旋蛋白在昆虫细胞粘附中的作用得到了粘附测定的进一步支持，该测定显示无螺旋蛋白的突变体的粘附受损，而重组螺旋蛋白触发了乳胶珠的粘附。我们还表明，从凝集素结合模式推断，细胞松弛素 D 会诱导表面暴露的糖缀合物发生变化，并特别改善 S.citri 野生型的粘附，但不会改善无螺旋蛋白突变体的粘附。这些结果表明，细胞松弛素 D 暴露了螺旋蛋白的昆虫细胞受体，而这些受体在未经处理的细胞中被掩盖。此外，用凝集素进行的竞争性粘附测定强烈表明，螺旋蛋白表现出与蚕豆凝集素 (VVA) 凝集素相似的糖缀合物结合特性。
Spiroplamas are helical, cell wall-less bacteria belonging to the Class Mollicutes, a group of microorganisms phylogenetically related to low G+C, Gram-positive bacteria. Spiroplasma species are all found associated with arthropods and a few, including Spiroplasma citri are pathogenic to plant. Thus S.citri has the ability to colonize cells of two very distinct hosts, the plant and the insect vector. While spiroplasmal factors involved in transmission by the leafhopper Circulifer haematoceps have been identified, their specific contribution to invasion of insect cells is poorly understood. In this study we provide evidence that the lipoprotein spiralin plays a major role in the very early step of cell invasion. Confocal laser scanning immunomicroscopy revealed a relocalization of spiralin at the contact zone of adhering spiroplasmas. The implication of a role for spiralin in adhesion to insect cells was further supported by adhesion assays showing that a spiralin-less mutant was impaired in adhesion and that recombinant spiralin triggered adhesion of latex beads. We also showed that cytochalasin D induced changes in the surface-exposed glycoconjugates, as inferred from the lectin binding patterns, and specifically improved adhesion of S.citri wild-type but not of the spiralin-less mutant. These results indicate that cytochalasin D exposes insect cell receptors of spiralin that are masked in untreated cells. In addition, competitive adhesion assays with lectins strongly suggest spiralin to exhibit glycoconjugate binding properties similar to that of the Vicia villosa agglutinin (VVA) lectin.