Cai Pengfei, Mu Yi, Piao Xianyu, Hou Nan, Liu Shuai, Gao Youhe, Wang Heng, Chen Qijun
MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, The Peoples Republic of China; Department of Microbiology and Parasitology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, The Peoples Republic of China.
National Key Laboratory of Medical Molecular Biology, Department of Physiology and Pathophysiology, School of Basic Medicine, Peking Union Medical College, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing, The Peoples Republic of China.
PLoS Negl Trop Dis. 2014 May 1;8(5):e2837. doi: 10.1371/journal.pntd.0002837. eCollection 2014 May.
Schistosomiasis is a chronic debilitating parasitic disease that afflicts more than 200 million individuals worldwide. Long-term administration of chemotherapy with the single available drug, praziquantel, has led to growing concerns about drug resistance. The PSD-95/Dlg/ZO-1 (PDZ) domain is an important module found in many scaffolding proteins, which has been recognized as promising targets for the development of novel drugs. However, the parasite-derived PDZ domains and their associated functions are still largely unknown.
METHODOLOGY/PRINCIPAL FINDINGS: The gene encoding the Schistosoma japonicum Scribble protein (SjScrib) was identified by homologous search with the S. mansoni Scrib sequence. By screening an arbitrary peptide library in yeast two-hybrid (Y2H) assays, we identified and confirmed the ligand binding specificity for each of the four PDZ domains of SjScrib. Both SjScrib-PDZ1 and SjScrib-PDZ3 recognize type I C-terminal PDZ-domain binding motifs (PBMs), which can be deduced as consensus sequences of -[Φ][x][E][TS][x][ILF] and -[x][RKx][ETS][T][WΦ][ILV], respectively. SjScrib-PDZ2 prefers stringent type II C-terminal PBMs, which significantly differs from that of its human ortholog. SjScrib-PDZ4 binds to typical II C-terminal PBMs with a consensus sequence -[x][FW][x][LI][x][LIV], in which the aromatic residue Phe is predominantly selected at position -4. The irregular and unconventional internal ligand binding specificities for the PDZ domains of SjScrib were confirmed by point mutations of the key amino acids within the ligand binding motifs. We also compared the differences in ligand specificities between SjScrib-PDZs and hScrib-PDZs, and explored the structural basis for the ligand binding properties of SjScrib-PDZs.
CONCLUSIONS/SIGNIFICANCE: In this study, we characterized and confirmed the ligand binding specificities of all four PDZ domains of SjScrib for the first time. We denoted the differential ligand binding specificities between SjScrib-PDZs and hScrib-PDZs as well as the structural basis for these properties. This work may provide a fundamental basis for the rational design of novel anti-schistosomal drugs.
血吸虫病是一种慢性衰弱性寄生虫病，全球有超过2亿人受其折磨。长期使用单一可用药物吡喹酮进行化疗，已引发对耐药性的日益担忧。PSD-95/Dlg/ZO-1（PDZ）结构域是许多支架蛋白中发现的重要模块，已被认为是新型药物开发的有前景靶点。然而，寄生虫来源的PDZ结构域及其相关功能仍 largely未知。
方法/主要发现：通过与曼氏血吸虫Scrib序列进行同源搜索，鉴定出编码日本血吸虫Scribble蛋白（SjScrib）的基因。通过在酵母双杂交（Y2H）实验中筛选随机肽库，我们鉴定并确认了SjScrib四个PDZ结构域各自的配体结合特异性。SjScrib-PDZ1和SjScrib-PDZ3都识别I型C末端PDZ结构域结合基序（PBMs），可分别推导为-[Φ][x][E][TS][x][ILF]和-[x][RKx][ETS][T][WΦ][ILV]的共有序列。SjScrib-PDZ2更喜欢严格的II型C末端PBMs，这与其人类同源物有显著差异。SjScrib-PDZ4结合具有共有序列-[x][FW][x][LI][x][LIV]的典型II型C末端PBMs，其中在-4位主要选择芳香族残基苯丙氨酸。通过配体结合基序内关键氨基酸的点突变，证实了SjScrib的PDZ结构域不规则和非常规的内部配体结合特异性。我们还比较了SjScrib-PDZs和hScrib-PDZs之间配体特异性的差异，并探索了SjScrib-PDZs配体结合特性的结构基础。
结论/意义：在本研究中，我们首次表征并确认了SjScrib所有四个PDZ结构域的配体结合特异性。我们指出了SjScrib-PDZs和hScrib-PDZs之间不同的配体结合特异性以及这些特性的结构基础。这项工作可能为新型抗血吸虫药物的合理设计提供基础依据。
