Ebulin l Is Internalized in Cells by Both Clathrin-Dependent and -Independent Mechanisms and Does Not Require Clathrin or Dynamin for Intoxication

• Published in: Toxins Vol. 13; no. 2; p. 102
• Main Authors: Iglesias, Rosario, Ferreras, José M, Llorente, Alicia, Citores, Lucía
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 30-01-2021; MDPI
• Subjects: Acidification; Apoptosis; Binding; Binding sites; Cell death; Chemical bonds; Clathrin; Cytosol; Cytotoxicity; Dynamin; ebulin; Endocytosis; Golgi apparatus; Intoxication; Intracellular; intracellular transport; Mutants; Protein synthesis; Proteins; Ricin; Toxicity; Toxins; intracellular transport; clathrin; lectin; ricin; ribosome-inactivating protein; apoptosis; endocytosis; ebulin; rRNA N-glycosylase; dynamin
• ISSN: 2072-6651; 2072-6651
• 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.