Interactions between Toxoplasma gondii and its host cells: function of the penetration-enhancing factor of toxoplasma
Interactions between Toxoplasma gondii and its host cells: function of the penetration-enhancing factor of toxoplasma
复制标题
弓形虫与其宿主细胞的相互作用：弓形虫渗透增强因子的功能
作者：
E. Lycke;K. Carlberg;R. Norrby
从弓形虫裂殖子中提取的分子量为70，000至150，000的蛋白质增强裂殖子穿透宿主细胞。裂殖子穿透的最适pH和温度与那些有利于穿透增强蛋白的作用相一致。此外，依赖于钙和镁存在的裂殖子的渗透，无论是在存在或不存在这种蛋白质。没有发现证据表明，由蛋白质引起的渗透增强作用是由于宿主细胞（HeLa）的吞噬能力增加或裂殖子的运动性改善。电子显微镜显示，蛋白质，在高浓度下，引起细胞质膜的破坏。在低100倍的浓度下，仍然引起渗透的显著增强，但没有观察到这种作用。然而，周围的空泡穿透寄生虫似乎小于裂殖子穿透的文化，没有渗透增强因子，限制空泡的膜表现出更频繁的不连续性。研究了几种已知酶的促渗作用。然而，这些酶似乎都不对应于弓形虫的渗透增强蛋白。弓形虫裂殖子进入宿主细胞的模式进行了讨论。它的结论是，吞噬作用必须发挥不太重要的作用，裂殖子积极穿透宿主细胞的细胞质膜。渗透被认为是机械和化学作用的结果。有人建议，由裂殖子释放的渗透增强因子的酶促功能是重要的。被穿透的裂殖子的液泡膜似乎是在穿透完成后在细胞中新形成的。
A protein with a molecular weight of 70,000 to 150,000 which was extracted from merozoites of Toxoplasma gondii enhanced the host cell penetration of the merozoites. The optimal pH and temperature for penetration of merozoites coincided with those favoring the action of the penetration-enhancing protein. In addition, a dependence on Ca and Mg existed for penetration of merozoites, either in the presence or absence of this protein. No evidence was found that indicated that the enhancing effect on penetration elicited by the protein was due to increased phagocytic capacity of host cells (HeLa) or improved motility of the merozoites. Electron microscopy demonstrated that the protein, in high concentration, caused disruption of cytoplasmic membranes. In a 100-fold-lower concentration, which still caused a marked enhancement of penetration, no such effect was observed. However, the vacuoles surrounding the penetrated parasites seemed smaller than for merozoites penetrating in cultures to which no penetration-enhancing factor was given, and the membranes limiting the vacuoles demonstrated discontinuities more often. The penetration-enchancing effect of some known enzymes was studies. However, none of these enzymes seemed to correspond to the penetration-enhancing protein of toxoplasma. The mode of entry of toxoplasma merozoites into host cells is discussed. It is concluded that phagocytosis must play a less important role and that merozoites actively penetrate the cytoplasmic membranes of the host cells. The penetration is proposed to be a result of combined mechanical and chemical actions. It is suggested that an enzymatic function of the penetration-enhancing factor released by the merozoites is of importance. The membrane limiting the vacuole of a penetrated merozoite seems to be newly formed in the cell after penetration is completed.