Efficient cellular uptake of recombinant murine Hoxc8 homeoprotein in COS-7 cells.

In order to analyze the self-delivery activity of Hoxc8, recombinant Hoxc8 protein (rHoxc8) was designed to be expressed and purified in E. coli as a glutathione S-transferase and green fluorescent protein-fused form (GST-GFP-Hoxc8). After purification using glutathione sepharose beads, the 82 kDa fusion protein was separated on the SDS-PAGE gel and confirmed by detecting the fluorescence through luminescent image analyzer. When rHoxc8 was added to culture media for 30 h, most of the COS-7 cells contained the fusion proteins, showing green fluorescence under the fluorescent microscope. When the efficiency of cellular uptake was examined after Hoechst staining, almost 100% of the cells exhibited the GFP signal, revealing that rHoxc8 can traverse the cellular membrane of COS-7 cells efficiently, suggesting that the rHoxc8 could be applied in the development of efficient and useful delivery vectors for therapeutic molecules.