Molecular Helminthology Laboratory, Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536, USA
Molecular Helminthology Laboratory, Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536, USA.
Biol Open. 2020 Mar 24;9(3):bio050385. doi: 10.1242/bio.050385.
Schistosomes are intravascular blood flukes that cause the parasitic disease schistosomiasis. In agreement with (Sm) proteomic analysis, we show here that the normally intracellular glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is also found at the parasite surface; live worms from all intravascular life stages display GAPDH activity. Suppressing GAPDH gene expression using RNA interference significantly lowers this live worm surface activity. Medium in which the worms are cultured overnight displays essentially no activity, showing that the enzyme is not shed or excreted but remains associated with the worm surface. Immunolocalization experiments confirm that the enzyme is highly expressed in the parasite tegument (skin). Surface activity in schistosomula amounts to ∼8% of that displayed by equivalent parasite lysates. To address the functional role of SmGAPDH, we purified the protein following its expression in strain DS113. The recombinant protein displays optimal enzymatic activity at pH 9.2, shows robust activity at the temperature of the parasite's hosts, and has a Michaelis-Menten constant for glyceraldehyde-3-phosphate (GAP) of 1.4 mM±0.24. We show that recombinant SmGAPDH binds plasminogen (PLMG) and promotes PLMG conversion to its active form (plasmin) in a dose response in the presence of tissue plasminogen activator. Since plasmin is a key mediator of thrombolysis, our results support the hypothesis that SmGAPDH, a host-interactive tegumental protein that can enhance PLMG activation, could help degrade blood clots around the worms in the vascular microenvironment and thus promote parasite survival This article has an associated First Person interview with the first author of the paper.
血吸虫是一种血管内血吸虫，会引起寄生虫病血吸虫病。与 (Sm) 蛋白质组学分析一致，我们在这里表明，通常存在于细胞内的糖酵解酶甘油醛-3-磷酸脱氢酶 (GAPDH) 也存在于寄生虫表面；所有血管内生命阶段的活虫都显示出 GAPDH 活性。使用 RNA 干扰抑制 GAPDH 基因表达会显著降低这种活虫表面活性。在寄生虫培养过夜的培养基中，基本上没有活性，表明该酶不会脱落或排泄，而是仍然与虫体表面相关。免疫定位实验证实该酶在寄生虫体被膜（皮肤）中高度表达。在尾蚴中显示的表面活性约为相应寄生虫裂解物的 8%。为了解决 SmGAPDH 的功能作用，我们在 株 DS113 中表达后对其进行了纯化。该重组蛋白在 pH 9.2 时显示出最佳的酶活性，在宿主寄生虫的温度下具有强大的活性，并且对甘油醛-3-磷酸 (GAP) 的米氏常数为 1.4 mM±0.24。我们表明重组 SmGAPDH 与纤溶酶原 (PLMG) 结合，并在组织纤溶酶原激活剂存在下以剂量反应的方式促进 PLMG 转化为其活性形式（纤溶酶）。由于纤溶酶是血栓溶解的关键介质，我们的结果支持这样的假设，即 SmGAPDH 是一种与宿主相互作用的体被蛋白，可增强 PLMG 的激活，有助于降解血管微环境中围绕蠕虫的血栓，从而促进寄生虫的生存。本文附有该论文第一作者的第一人称采访。
