The role of microsporidian polar tube protein 4 (PTP4) in host cell infection.
The role of microsporidian polar tube protein 4 (PTP4) in host cell infection.
复制标题
微孢子虫极管蛋白4（PTP4）在宿主细胞感染中的作用
DOI：
10.1371/journal.ppat.1006341
复制
发表时间：
2017-04
期刊：
影响因子：
6.7
通讯作者：
Weiss LM
中科院分区：
文献类型：
--
作者：
Han B;Polonais V;Sugi T;Yakubu R;Takvorian PM;Cali A;Maier K;Long M;Levy M;Tanowitz HB;Pan G;Delbac F;Zhou Z;Weiss LM
微孢子虫已被确认为对我们的健康、食品安全和经济具有重要影响的病原体。这些专性细胞内病原体成功的关键在于其独特的入侵细胞器——极管，它在入侵过程中将含有孢原质的细胞核输送到宿主细胞中。由于极管的大小、极管射出和孢原质通过的速度，以及缺乏用于操作微孢子虫的基因技术，对这种细胞器的研究一直很困难，并且对于极管的形成以及构成这种结构的蛋白质的功能知之甚少。在此，我们对来自微孢子虫海伦脑炎微孢子虫（Encephalitozoon hellem）的极管蛋白4（PTP4）进行了特性分析，发现一种针对PTP4的单克隆抗体标记在极管的顶端，这表明PTP4可能在入侵过程中参与与宿主细胞蛋白质的直接相互作用。进一步采用间接免疫荧光（IFA）、酶联免疫吸附测定（ELISA）和荧光激活细胞分选（FACS）分析证实PTP4与哺乳动物细胞结合。添加重组PTP4蛋白或抗PTP4抗体可降低其宿主细胞在体外的微孢子虫感染。通过免疫沉淀纯化的与宿主细胞膜结合的PTP4的蛋白质组学分析确定转铁蛋白受体1（TfR1）是PTP4潜在的宿主细胞相互作用伙伴。额外的实验表明，敲除TfR1、向细胞培养物中添加TfR1重组蛋白或向细胞培养物中添加抗TfR1抗体可显著降低微孢子虫感染率。这些结果表明PTP4是极管的一种重要蛋白质，参与这些病原体利用的宿主细胞感染机制。
微孢子虫是专性细胞内寄生虫，会在免疫抑制个体（如艾滋病患者和器官移植受者）中引发疾病。微孢子虫由一种独特的入侵细胞器——极管来界定。这种细胞器的形成及其在感染机制中的作用仍然未知。在此，我们确定了海伦脑炎微孢子虫极管蛋白4（PTP4）在感染中的作用，证明PTP4可通过宿主转铁蛋白受体1（TfR1）蛋白与宿主细胞表面结合。干扰PTP4和TfR1的相互作用会导致宿主细胞的微孢子虫感染显著减少。这些数据表明PTP4在这种病原体感染宿主细胞过程中是一种重要的微孢子虫蛋白质。
Microsporidia have been identified as pathogens that have important effects on our health, food security and economy. A key to the success of these obligate intracellular pathogens is their unique invasion organelle, the polar tube, which delivers the nucleus containing sporoplasm into host cells during invasion. Due to the size of the polar tube, the rapidity of polar tube discharge and sporoplasm passage, and the absence of genetic techniques for the manipulation of microsporidia, study of this organelle has been difficult and there is relatively little known regarding polar tube formation and the function of the proteins making up this structure. Herein, we have characterized polar tube protein 4 (PTP4) from the microsporidium Encephalitozoon hellem and found that a monoclonal antibody to PTP4 labels the tip of the polar tube suggesting that PTP4 might be involved in a direct interaction with host cell proteins during invasion. Further analyses employing indirect immunofluorescence (IFA), enzyme-linked immunosorbent (ELISA) and fluorescence-activated cell sorting (FACS) assays confirmed that PTP4 binds to mammalian cells. The addition of either recombinant PTP4 protein or anti-PTP4 antibody reduced microsporidian infection of its host cells in vitro. Proteomic analysis of PTP4 bound to host cell membranes purified by immunoprecipitation identified transferrin receptor 1 (TfR1) as a potential host cell interacting partner for PTP4. Additional experiments revealed that knocking out TfR1, adding TfR1 recombinant protein into cell culture, or adding anti-TfR1 antibody into cell culture significantly reduced microsporidian infection rates. These results indicate that PTP4 is an important protein competent of the polar tube involved in the mechanism of host cell infection utilized by these pathogens.