Li Zhi, Pan Guoqing, Li Tian, Huang Wei, Chen Jie, Geng Lina, Yang Donglin, Wang Linling, Zhou Zeyang
State Key Laboratory of Silkworm Genome Biology, Southwest University, Beibei, Chongqing, People’s Republic of China.
Eukaryot Cell. 2012 Feb;11(2):229-37. doi: 10.1128/EC.05127-11. Epub 2011 Dec 2.
Microsporidia are a group of eukaryotic intracellular parasites that infect almost all vertebrates and invertebrates. The microsporidian invasion process involves the extrusion of a unique polar tube into host cells. Both the spore wall and the polar tube play an important role in microsporidian pathogenesis. So far, five spore wall proteins (SWP1, SWP2, Enp1, Enp2, and EcCDA) from Encephalitozoon intestinalis and Encephalitozoon cuniculi and five spore wall proteins (SWP32, SWP30, SWP26, SWP25, and NbSWP5) from the silkworm pathogen Nosema bombycis have been identified. Here we report the identification and characterization of a spore wall protein (SWP5) with a molecular mass of 20.3 kDa in N. bombycis. This protein has low sequence similarity to other eukaryotic proteins. Immunolocalization analysis showed SWP5 localized to the exospore and the region of the polar tube in mature spores. Immunoprecipitation, mass spectrometry, and immunofluorescence analyses revealed that SWP5 interacts with the polar tube proteins PTP2 and PTP3. Anti-SWP5 serum pretreatment of mature spores significantly decreased their polar tube extrusion rate. Taken together, our results show that SWP5 is a spore wall protein localized to the spore wall and that it interacts with the polar tube, may play an important role in supporting the structural integrity of the spore wall, and potentially modulates the course of infection of N. bombycis.
微孢子虫是一类真核细胞内寄生虫，可感染几乎所有的脊椎动物和无脊椎动物。微孢子虫的入侵过程涉及将一根独特的极管挤压到宿主细胞中。孢子壁和极管在微孢子虫的致病机制中都起着重要作用。到目前为止，已鉴定出来自肠道脑炎微孢子虫和兔脑炎微孢子虫的五种孢子壁蛋白（SWP1、SWP2、Enp1、Enp2和EcCDA），以及来自家蚕病原体家蚕微孢子虫的五种孢子壁蛋白（SWP32、SWP30、SWP26、SWP25和NbSWP5）。在此，我们报告在家蚕微孢子虫中鉴定和表征了一种分子量为20.3 kDa的孢子壁蛋白（SWP5）。该蛋白与其他真核蛋白的序列相似性较低。免疫定位分析表明，SWP5定位于成熟孢子的外孢子和极管区域。免疫沉淀、质谱和免疫荧光分析显示，SWP5与极管蛋白PTP2和PTP3相互作用。用抗SWP5血清预处理成熟孢子可显著降低其极管挤压率。综上所述，我们的结果表明，SWP5是一种定位于孢子壁的孢子壁蛋白，它与极管相互作用，可能在维持孢子壁的结构完整性方面发挥重要作用，并可能调节家蚕微孢子虫的感染过程。
