Recombinant receptor-binding domain of diphtheria toxin increases the potency of curcumin by enhancing cellular uptake.
Diphtheria toxin (DT) binds to a specific cell surface receptor, gets internalized, and causes cytotoxicity through its catalytic domain. The toxicity of DT is used in several therapeutic molecules. Here, we have exploited the receptor-binding ability of DT to increase cellular uptake of curcumin, a hydrophobic molecule with low bioavailability and cellular uptake. We have expressed only the receptor-binding domain of DT (RDT) in Escherichia coli. Purified RDT binds to the receptor with an affinity equivalent to that of full-length DT. It also binds to curcumin forming a curcumin-RDT complex, and this increases the fluorescence intensity and fluorescence lifetime of curcumin. The curcumin-RDT complex binds to the receptor and associates with human glioblastoma cells (U-87 MG) expressing the receptor. The cellular uptake of curcumin is higher for the curcumin-RDT complex than curcumin alone. This increase in uptake enhances the antiproliferative effect of curcumin and induces apoptosis of these cells even at a lower dose.
Department of Biotechnology and ‡Department of Chemistry, Indian Institute of Technology Guwahati , Guwahati, 781039 India.
Ashok
A
Kumar
Gopal
G
Das
Biplab
B
Bose
D000970:Antineoplastic Agents / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D003474:Curcumin / Q000494:pharmacology*; D004167:Diphtheria Toxin / Q000378:metabolism*; D004337:Drug Carriers; D005434:Flow Cytometry; D005909:Glioblastoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008856:Microscopy, Fluorescence; D011485:Protein Binding; D011487:Protein Conformation; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism*; D020349:Surface Plasmon Resonance; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D004167:Diphtheria Toxin; D004337:Drug Carriers; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D003474:Curcumin