Cellular and Molecular Life Sciences CMLS

, Volume 54, Issue 8, pp 866–875

The effect of monensin and chloroquine on the endocytosis and toxicity of chimeric toxins

  • R. Ippoliti
  • P. Ginobbi
  • E. Lendaro
  • I. D'Agostino
  • D. Ombres
  • P. A. Benedetti
  • M. Brunori
  • G. Citro

DOI: 10.1007/s000180050214

Cite this article as:
Ippoliti, R., Ginobbi, P., Lendaro, E. et al. CMLS, Cell. Mol. Life Sci. (1998) 54: 866. doi:10.1007/s000180050214

Abstract.

The toxicity of two conjugates containing ribosome-inactivating proteins (RIPs, i.e. saporin and ricin-A chain x-linked to transferrin) has been measured on a prostatic cancer line (PC3) naturally overexpressing the transferrin receptor, in the presence of monensin and chloroquine. This paper investigates whether the increased toxicity of Tf-RIPs induced by monensin and chloroquine may be due to alterations of the normal endocytotic pathway of the complexes mediated by the transferrin receptor. Monensin, besides inducing alkalinization of normally acid intracellular compartments, causes an accumulation of the receptor-bound Tf-RIP in a perinuclear region contiguous to the cisternae of the trans-Golgi network. Chloroquine, though increasing the intracellular pH, seems not to modify the endocytotic pathway of these chimeric molecules. We believe that the enhanced toxicity of the Tf-RIPs may be related to intracellular alkalinization (i.e. endosomal or lysosomal pH) rather than to the effects on the recycling of transferrin receptor-bound toxins. We conclude that the efficacy of chimeric toxins may be modulated not only by the carrier used for their engineering but also by addition of drugs able to influence the stability and activation of the toxins inside the cell.

Key words. Ricin; transferrin; monensin; chloroquine; endocytosis; chimeras; cancer. 

Copyright information

© Birkhäuser Verlag Basel, 1998

Authors and Affiliations

  • R. Ippoliti
    • 1
  • P. Ginobbi
    • 2
  • E. Lendaro
    • 1
  • I. D'Agostino
    • 1
  • D. Ombres
    • 2
  • P. A. Benedetti
    • 3
  • M. Brunori
    • 1
  • G. Citro
    • 2
  1. 1.Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Biochemical Sciences ‘A. Rossi-Fanelli’, University of Rome ‘La Sapienza’, P. le Aldo Moro 5, I-00185 Rome (Italy), Fax +39 6 4440062, e-mail: ippoliti@axrma.uniroma1.itIT
  2. 2.Experimental Chemotherapy Laboratory, Regina Elena Cancer Institute, Rome (Italy)IT
  3. 3.CNR Biophysics Institute, Pisa (Italy)IT

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