Endocytosis and intracellular localisation of type 1 ribosome-inactivating protein saporin-S6

A. Bolognesi, L. Polito, V. Scicchitano, C. Orrico, G. Pasquinelli, S. Musiani, S. Santi, M. Riccio, M. Bortolotti, Maria Giulia Battelli

Research output: Contribution to journalArticlepeer-review


Saporin-S6 is a single-chain ribosome-inactivating protein (RIP) that has low toxicity in cells and animals. When the protein is bound to a carrier that facilitates cellular uptake, the protein becomes highly and selectively toxic to the cellular target of the carrier. Thus, saporin-S6 is one of the most widely used RIPs in the preparation of immunoconjugates for anti-cancer therapy. The endocytosis of saporin-S6 by the neoplastic HeLa cells and the subsequent intracellular trafficking were investigated by confocal microscopy that utilises indirect immunofluorescence analysis and transmission electron microscopy that utilises a direct assay with gold-conjugated saporin-S6 and an indirect immunoelectron microscopy assay. Our results indicate that saporin-S6 was taken up by cells mainly through receptor-independent endocytosis. Confocal microscopy analysis showed around 30% co-localisation of saporin-S6 with the endosomal compartment and less than 10% co-localisation with the Golgi apparatus. The pathway identified by the immunofluorescence assay and transmission electron microscopy displayed a progressive accumulation of saporin-S6 in perinuclear vesicular structures. The main findings of this work are the following: i) the nuclear localisation of saporin-S6 and ii) the presence of DNA gaps resulting from abasic sites in HeLa nuclei after intoxication with saporin-S6.

Original languageEnglish
Pages (from-to)97-109
Number of pages13
JournalJournal of Biological Regulators and Homeostatic Agents
Issue number1
Publication statusPublished - Jan 2012


  • Anti-cancer drugs
  • Endocytosis
  • Intracellular trafficking
  • Saporin-S6
  • Type I ribosome-inactivating proteins

ASJC Scopus subject areas

  • Oncology
  • Endocrinology, Diabetes and Metabolism
  • Physiology (medical)
  • Immunology and Allergy
  • Immunology
  • Endocrinology
  • Physiology
  • Cancer Research


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