Department of Biochemistry and Molecular Biology and Physiology, Faculty of Sciences, University of Valladolid, E-47011 Valladolid, Spain.
Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, 0379 Oslo, Norway.
Toxins (Basel). 2021 Jan 30;13(2):102. doi: 10.3390/toxins13020102.
Ebulin l is an A-B toxin, and despite the presence of a B chain, this toxin displays much less toxicity to cells than the potent A-B toxin ricin. Here, we studied the binding, mechanisms of endocytosis, and intracellular pathway followed by ebulin l and compared it with ricin. COS-1 cells and HeLa cells with inducible synthesis of a mutant dynamin (K44A) were used in this study. The transport of these toxins was measured using radioactively or fluorescently labeled toxins. The data show that ebulin l binds to cells to a lesser extent than ricin. Moreover, the expression of mutant dynamin does not affect the endocytosis, degradation, or toxicity of ebulin l. However, the inhibition of clathrin-coated pit formation by acidification of the cytosol reduced ebulin l endocytosis but not toxicity. Remarkably, unlike ricin, ebulin l is not transported through the Golgi apparatus to intoxicate the cells and ebulin l induces apoptosis as the predominant cell death mechanism. Therefore, after binding to cells, ebulin l is taken up by clathrin-dependent and -independent endocytosis into the endosomal/lysosomal system, but there is no apparent role for clathrin and dynamin in productive intracellular routing leading to intoxication.
埃博霉素 l 是一种 A-B 毒素，尽管存在 B 链，但与强效的 A-B 毒素蓖麻毒素相比，这种毒素对细胞的毒性要小得多。在这里，我们研究了埃博霉素 l 的结合、内吞作用机制和细胞内途径，并将其与蓖麻毒素进行了比较。本研究使用了可诱导合成突变体动力蛋白（K44A）的 COS-1 细胞和 HeLa 细胞。使用放射性或荧光标记的毒素测量这些毒素的转运。数据表明，埃博霉素 l 与细胞的结合程度低于蓖麻毒素。此外，突变型动力蛋白的表达并不影响埃博霉素 l 的内吞作用、降解或毒性。然而，通过酸化细胞质来抑制网格蛋白包被小窝的形成会减少埃博霉素 l 的内吞作用，但不会降低其毒性。值得注意的是，与蓖麻毒素不同，埃博霉素 l 不会通过高尔基体运输到细胞中使其中毒，并且埃博霉素 l 诱导细胞凋亡是主要的细胞死亡机制。因此，埃博霉素 l 与细胞结合后，通过网格蛋白依赖和非依赖的内吞作用进入内体/溶酶体系统，但在导致中毒的有效细胞内路由中，网格蛋白和动力蛋白似乎没有明显作用。
