A Novel Polyarginine Containing Smac Peptide Conjugate that Mediates Cell Death in Tumor and Healthy Cells

作者：Steffen Markus Heckl, Alexander Sturzu, Marc Regenbogen, Alexander Beck, Gong Fei-l, Alireza Gharabaghi, Hartmut Echner · 发表于：Medicinal Chemistry · 年份：2008 · DOI：10.2174/157340608784872217 · 被引用次数：16 · 研究领域：Chemical Synthesis and Analysis、RNA Interference and Gene Delivery、Synthesis and Characterization of Heterocyclic Compounds

The seven N-terminal amino acids AVPIAQK (SmacN7) of the mitochondrial protein Smac (second mitochondria-derived activator of caspase) promote caspase activation by binding specifically to inhibitor of apoptosis proteins (IAPs) and blocking their inhibitory activity. SmacN7 cannot pass through the cell membrane, but to be of therapeutic use it would be essential for it to enter the cell. To achieve transmembrane transport of SmacN7 we coupled it to a novel fluorescein isothiocyanate (FITC)-labelled transmembrane transport peptide RRRRK(FITC)RRRR via ss-alanine to produce the conjugate AVPIAQKssA RRRRK(FITC)RRRR. Because IAPs are much more strongly expressed in the cytoplasm of tumor cells, we expected this conjugate to produce staining of the cytoplasm, and for this to be stronger in tumor cells than in healthy cells. Surprisingly, we found strong nuclear uptake of the Smac conjugate and of the transport peptide alone without subsequent release in both tumor cells and healthy cells from the bladder, prostate, and brain. This was accompanied by cell death. In contrast to expectations, it appears that the apoptotic effects observed do not result from the SmacN7 cargo alone.