Injection of Affibodies by a Self-Organizing Bacterial Syringe to Interfere with Intracellular Signaling.

Photorhabdus luminescens produces a syringe-like toxin complex to inject toxic enzymes into cells. We demonstrated that the recombinant Photorhabdus toxin complex (PTC) can be engineered for translocation of foreign cargo proteins across cellular membranes. We showed that the system is suitable for injection of trimeric affibodies into mammalian cells in order to influence crucial signaling pathways. As proof of principle, we inhibited Ras-driven tumor cell proliferation by injection of an affibody which interacts with the Ras binding domain of Raf kinase. The system described here could be applicable to target a wide range of signaling molecules for cell biological or therapeutic intervention.