An Apoptosis-Inducing Peptidic Heptad That Efficiently Clusters Death Receptor 5

Multivalent ligands of death receptors hold particular promise as tumor cell-specific therapeutic agents because they induce an apoptotic cascade in cancerous cells. Herein, we present a modular approach to generate death receptor 5 (DR5) binding constructs comprising multiple copies of DR5 targeting peptide (DR5TP) covalently bound to biomolecular scaffolds of peptidic nature. This strategy allows for efficient oligomerization of synthetic DR5TP-derived peptides in different spatial orientations using a set of enzyme-promoted conjugations or recombinant production. Heptameric constructs based on a short (60-75 residues) scaffold of a C-terminal oligomerization domain of human C4b binding protein showed remarkable proapoptotic activity (EC50=3 nm) when DR5TP was ligated to its carboxy terminus. Our data support the notion that inter-ligand distance, relative spatial orientation and copy number of receptor-binding modules are key prerequisites for receptor activation and cell killing.