Peña Janeth J, Adema Coen M
Center for Evolutionary and Theoretical Immunology, Department of Biology, University of New Mexico, MSCO3 2020, Albuquerque, NM, United States of America.
PLoS One. 2016 Dec 30;11(12):e0168665. doi: 10.1371/journal.pone.0168665. eCollection 2016.
The parasitic flatworm Schistosoma mansoni, causative agent of human intestinal schistosomiasis in South America, relies importantly on the freshwater snail Biomphalaria glabrata as intermediate host to achieve development of cercariae that infect humans. The recommendation from the World Health Organization (WHO) to integrate snail control in efforts to counter schistosomiasis transmission provides impetus for in depth study of B. glabrata biology. Our analysis indicates that two distinct hemocyanin-like genes (hcl-1 and hcl-2) are present in B. glabrata, a snail that uses hemoglobin for oxygen transport. Characterization of BAC clones yielded the full length hcl-1 gene, which is comprised of three functional unit (FU) domains at the amino acid level. Database searches and in silico analyses identified the second hcl gene (hcl-2), composed of six FU domains. Both genes are unusual for lacking canonical residues and having fewer FU domains than typical molluscan hemocyanins that contain 7-8 FUs. Reverse transcription PCR demonstrated that Hcl-1 is expressed in a manner that correlates with reproductive maturity in the albumen gland (AG), an immune- and reproduction-relevant organ. Immune cross-reactivity with anti-keyhole limpet hemocyanin (α-KLH) antiserum and tandem-mass spectrometry validated the presence of Hcl-1 protein in the AG and egg mass fluid (EMF). The evolutionary conservation of hemocyanin-like sequences in B. glabrata in the presence of the oxygen carrier hemoglobin, combined with our results, suggest that the Hcl-1protein has a functional role in general and/or reproductive biology. Further investigations are needed to explore Hcl-1 as a potential target for snail control.
寄生扁虫曼氏血吸虫是南美洲人类肠道血吸虫病的病原体，它严重依赖淡水螺类光滑双脐螺作为中间宿主来完成尾蚴的发育，尾蚴可感染人类。世界卫生组织（WHO）建议将控制螺类纳入防治血吸虫病传播的工作中，这为深入研究光滑双脐螺的生物学特性提供了动力。我们的分析表明，在以血红蛋白进行氧气运输的光滑双脐螺中存在两个不同的类血蓝蛋白基因（hcl-1和hcl-2）。BAC克隆的特征分析得到了全长的hcl-1基因，该基因在氨基酸水平上由三个功能单元（FU）结构域组成。数据库搜索和计算机分析确定了第二个hcl基因（hcl-2），它由六个FU结构域组成。这两个基因都不寻常，因为它们缺乏典型残基，且FU结构域比含有7-8个FU的典型软体动物血蓝蛋白少。逆转录PCR表明，Hcl-1在蛋白腺（AG）中以与生殖成熟相关的方式表达，蛋白腺是一个与免疫和生殖相关的器官。与抗钥孔血蓝蛋白（α-KLH）抗血清的免疫交叉反应和串联质谱验证了AG和卵团液（EMF）中存在Hcl-1蛋白。在存在氧气载体血红蛋白的情况下，光滑双脐螺中类血蓝蛋白序列的进化保守性，结合我们的研究结果，表明Hcl-1蛋白在一般生物学和/或生殖生物学中具有功能作用。需要进一步研究以探索Hcl-1作为控制螺类的潜在靶点。
