Division of Experimental Medicine, National Cancer Institute, Rio de Janeiro, Brazil.
Cell Mol Life Sci. 2010 May;67(10):1653-9. doi: 10.1007/s00018-010-0291-0. Epub 2010 Feb 7.
Different death-styles have been described in unicellular organisms. In most cases they evolve with phenotypic features similar to apoptotic death of animal cells, such as phosphatidylserine (PS) exposure, oligonucleosomal DNA fragmentation, and loss of mitochondrial transmembrane potential, hinting that similar mechanisms operate in both situations. However, the biochemical pathways underlying death in unicellular organisms are still unclear. Host recognition of PS exposed on the surface of unicellular parasites is an important feature of the process of infection and progression of the disease. Here, we discuss data showing that entirely different mechanisms of PS exposure co-exist during the life-cycle of Leishmania amazonensis: in the case of promastigotes, a sub-population dies by apoptosis; in the case of amastigotes, the entire population exposes PS, not necessarily followed by apoptotic death. This phenomenon has been called apoptotic mimicry. The elusive caspase-like activities described in protozoa are also discussed.
不同的死亡方式已在单细胞生物中被描述。在大多数情况下,它们的表型特征与动物细胞凋亡性死亡相似,例如磷脂酰丝氨酸(PS)暴露、寡核苷酸体 DNA 片段化以及线粒体跨膜电势丧失,这表明类似的机制在两种情况下都起作用。然而,单细胞生物中死亡的生化途径仍不清楚。宿主对单细胞寄生虫表面暴露的 PS 的识别是感染和疾病进展过程的一个重要特征。在这里,我们讨论了一些数据,这些数据表明在莱什曼原虫属(Leishmania amazonensis)的生命周期中,完全不同的 PS 暴露机制同时存在:在前鞭毛体的情况下,亚群通过凋亡死亡;在无鞭毛体的情况下,整个群体暴露 PS,不一定随后发生凋亡性死亡。这种现象被称为凋亡模拟。也讨论了在原生动物中描述的难以捉摸的半胱天冬酶样活性。
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