Casaravilla Cecilia, Freire Teresa, Malgor Ramiro, Medeiros Andrea, Osinaga Eduardo, Carmona Carlos
Unidad de Biología Parasitaria, Departamento de Biología Celular y Molecular, Facultad de Ciencias, Instituto de Higiene, Av. A. Navarro 3051 CP11600, Montevideo, Uruguay.
J Parasitol. 2003 Aug;89(4):709-14. doi: 10.1645/GE-2970.
This article focuses on the initiation pathway of mucin-type O-glycosylation in helminth parasites. The presence of the GalNAc-O-Ser/Thr structure, also known as Tn antigen, a truncated determinant related to aberrant glycosylation in mammal cells, and the activity of the UDP-GalNAc:polypeptide N-acetyl-galactosaminyltransferase (ppGaNTase), the enzyme responsible for its synthesis, were studied in species from major taxonomic groups. Tn reactivity was determined in extracts from Taenia hydatigena, Mesocestoides corti, Fasciola hepatica, Nippostrongylus brasiliensis, and Toxocara canis using the monoclonal antibody 83D4. The Tn determinant was revealed in all preparations, and multiple patterns of Tn-bearing glycoproteins were observed by immunoblotting. Additionally, the first evidence that helminth parasites express ppGaNTase activity was obtained. This enzyme was studied in extracts from Echinococcus granulosus, F. hepatica, and T. canis by measuring the incorporation of UDP-(3H)GalNAc to both deglycosylated ovine syalomucin (dOSM) and synthetic peptide sequences derived from tandem repeats of human mucins. Whereas significant levels of ppGaNTase activity were detected in all the extracts when dOSM was used as a multisite acceptor, it was only observed in F. hepatica and E. granulosus extracts when mucin-derived peptides were used, suggesting that T. canis ppGaNTase enzyme(s) may represent a member of the gene family with a more restricted specificity for worm O-glycosylation motifs. The widespread expression of Tn antigen, capable of evoking both humoral and cellular immunity, strongly suggests that simple mucin-type O-glycosylation does not constitute an aberrant phenomenon in helminth parasites.
本文聚焦于蠕虫寄生虫中粘蛋白型O-糖基化的起始途径。研究了主要分类群物种中GalNAc-O-Ser/Thr结构（也称为Tn抗原，一种与哺乳动物细胞异常糖基化相关的截短决定簇）的存在情况，以及负责其合成的UDP-GalNAc：多肽N-乙酰半乳糖胺基转移酶（ppGaNTase）的活性。使用单克隆抗体83D4测定了来自泡状带绦虫、犬复孔绦虫、肝片吸虫、巴西日圆线虫和犬弓首蛔虫提取物中的Tn反应性。在所有制剂中均检测到Tn决定簇，通过免疫印迹观察到多种含Tn糖蛋白的模式。此外，还获得了蠕虫寄生虫表达ppGaNTase活性的首个证据。通过测量UDP-(3H)GalNAc掺入去糖基化的绵羊唾液粘蛋白（dOSM）和源自人粘蛋白串联重复序列的合成肽序列，对来自细粒棘球绦虫、肝片吸虫和犬弓首蛔虫提取物中的这种酶进行了研究。当使用dOSM作为多位点受体时，在所有提取物中均检测到显著水平的ppGaNTase活性，但当使用粘蛋白衍生肽时，仅在肝片吸虫和细粒棘球绦虫提取物中观察到，这表明犬弓首蛔虫的ppGaNTase酶可能代表基因家族的一个成员，对蠕虫O-糖基化基序具有更受限的特异性。能够引发体液免疫和细胞免疫的Tn抗原的广泛表达，强烈表明简单的粘蛋白型O-糖基化在蠕虫寄生虫中并非异常现象。
