The BH3 domain of BAD fused to the Antennapedia peptide induces apoptosis via its alpha helical structure and independent of Bcl-2

Since the over-expression of Bcl-2 is a common cause of multi-drug resistan ce, cytotoxic peptides that overcome the effects of Bcl-2 may be clinically useful. We harnessed the death-promoting alpha helical properties of the B H3 domain of BAD by fusing it to the Antennapedia (ANT) domain, which allow s for cell entry (ANTBH3BAD). Treatment of 32D cells with the ANTBH3BAD pep tide results in a 99% inhibition of colony formation. No significant toxici ty is observed after treatment with ANT or BH3BAD alone. A mutant fusion pe ptide unable to bind Bcl-2 induces cell death as effectively as the wild-ty pe ANTBH3BAD, Furthermore, 32D cells over-expressing Bcl-2 show no resistan ce to the ANTBH3BAD peptide, Therefore, the toxicity of the peptide was ind ependent of the Bcl-2 pathway, We demonstrate that the toxicity of the pept ide is due to its alpha helicity that disrupts mitochondrial function. Sinc e this peptide overcomes major forms of drug resistance, it may be therapeu tically useful if appropriately targeted to malignant cells.