Salto Maria Laura, Bertello Laura E, Vieira Mauricio, Docampo Roberto, Moreno Silvia N J, de Lederkremer Rosa M
Laboratory of Molecular Parasitology, Department of Pathobiology and Center for Zoonoses Research, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, 61802, USA.
Eukaryot Cell. 2003 Aug;2(4):756-68. doi: 10.1128/EC.2.4.756-768.2003.
Differentiation of Trypanosoma cruzi trypomastigotes to amastigotes inside myoblasts or in vitro, at low extracellular pH, in the presence of [(3)H]palmitic acid or [(3)H]inositol revealed differential labeling of inositolphosphoceramide and phosphatidylinositol, suggesting that a remodeling process takes place in both lipids. Using (3)H-labeled inositolphosphoceramide and phosphatidylinositol as substrates, we demonstrated the association of at least five enzymatic activities with the membranes of amastigotes and trypomastigotes. These included phospholipase A(1), phospholipase A(2), inositolphosphoceramide-fatty acid hydrolase, acyltransferase, and a phospholipase C releasing either ceramide or a glycerolipid from the inositolphospholipids. These enzymes may be acting in remodeling reactions leading to the anchor of mature glycoproteins or glycoinositolphospholipids and helping in the transformation of the plasma membrane, a necessary step in the differentiation of slender trypomastigotes to round amastigotes. Synthesis of inositolphosphoceramide and particularly of glycoinositolphospholipids was inhibited by aureobasidin A, a known inhibitor of fungal inositolphosphoceramide synthases. The antibiotic impaired the differentiation of trypomastigotes at acidic pH, as indicated by an increased appearance of intermediate forms and a decreased expression of the Ssp4 glycoprotein, a characteristic marker of amastigote forms. Aureobasidin A was also toxic to differentiating trypomastigotes at acidic pH but not to trypomastigotes maintained at neutral pH. Our data suggest that inositolphosphoceramide is implicated in T. cruzi differentiation and that its metabolism could provide important targets for the development of antiparasitic therapies.
在成肌细胞内或体外，在低细胞外pH值条件下，在存在[³H]棕榈酸或[³H]肌醇的情况下，克氏锥虫锥鞭毛体向无鞭毛体的分化显示出肌醇磷酸神经酰胺和磷脂酰肌醇的差异标记，这表明两种脂质都发生了重塑过程。使用³H标记的肌醇磷酸神经酰胺和磷脂酰肌醇作为底物，我们证明了至少五种酶活性与无鞭毛体和锥鞭毛体的膜相关联。这些酶包括磷脂酶A(1)、磷脂酶A(2)、肌醇磷酸神经酰胺-脂肪酸水解酶、酰基转移酶，以及一种从肌醇磷脂中释放神经酰胺或甘油脂质的磷脂酶C。这些酶可能参与重塑反应，导致成熟糖蛋白或糖基磷脂酰肌醇的锚定，并有助于质膜的转化，这是细长锥鞭毛体向圆形无鞭毛体分化的必要步骤。肌醇磷酸神经酰胺尤其是糖基磷脂酰肌醇的合成受到金担子素A的抑制，金担子素A是一种已知的真菌肌醇磷酸神经酰胺合酶抑制剂。如中间形式出现增加和无鞭毛体形式的特征性标志物Ssp4糖蛋白表达降低所示，该抗生素损害了酸性pH条件下锥鞭毛体的分化。金担子素A对酸性pH条件下正在分化的锥鞭毛体也有毒性，但对维持在中性pH条件下的锥鞭毛体无毒。我们的数据表明，肌醇磷酸神经酰胺与克氏锥虫的分化有关，其代谢可能为抗寄生虫疗法的开发提供重要靶点。
