PORTFOLIO

The administration of medication is more efficient if the respective drug can be delivered in a targeted way to the exact cells or tissues of the body on which the medication is intended to act on. The delivery of effectors to the cytoplasm of target cells is therefore an important problem in medicine (drug delivery) and biotechnology. Here, we will explore the use of bacterial contractile injection systems (BCIS) as a novel delivery vehicle. These BCIS are recently-discovered bacteriophage-like particles that inject their payload into target cells. Our recent efforts identified potential effectors and showed that some BCIS can accommodate large effector payloads. In an interdisciplinary approach, we will 1) investigate the mechanism of effector targeting/binding in the inner tube and 2) re-engineer the system to accommodate novel effectors of choice. The results will help to develop a bioinformatic tool, which can be used to design novel effectors for the translocation by BCIS in the future. In sum, the project could lead to the availability of re-engineered systems that are effective for antibiotic treatment or drug delivery.

Innovative approach:
Based on their contractile, membrane-perforating properties, BCIS have been proposed for an application as novel antibacterial agents. The lack of knowledge on how considerable amounts of effectors can be loaded into a BCIS, however, has prevented to engineer them for the use for effector delivery to eukaryotic cells. This project will pave the way to load BCIS with many copies of an effector of choice.

Impact on drug delivery strategies and biotechnological applications:
The groundwork of this project to understand effector binding to the BCIS will have major impact on the function of BCIS in general. The possibility to predict how a given effector has to be engineered in order for it to be delivered to the target presents a novel strategy for effector delivery. This is significant for drug delivery to organisms, as well as for biotechnological tools that can be used for research. The design of cell line-specific BCIS will be the next step in the future, enabled by the work proposed in this project. This vision has great potential, since it might allow targeted treatment of only diseased cells (e.g. cancer cells).

We identified the protein 615 as an effector molecule that is delivered by BCIS to cells of a tubeworm larva. We elucidated that the protein 615 is localized inside the inner tube of the BCIS. The protein 605 is likely a targeting factor that guides 615 to the inner tube. This way of loading a BCIS with an effector is novel and presents the possibility to accommodate a high payload per BCIS. Our results also discovered that the 615 N-terminus seems to play a role in guiding the effector to the lumen of the inner tube of the BCIS. We are now in the process to investigate how these findings can be exploited to load effectors of choice and translocate them into target cells. Further exciting results indicate that the so-called “tail pins” might play a role in the binding of the BCIS to target cells. Present and future work will explore whether the re-engineering of the tail pins will allow us to specifically target a certain cell type, which can be important for the efficient delivery of drugs. We envision that our results will pave the way for BCIS being broadly used as a novel vehicle for specific and efficient delivery of drugs.

Sophie A Howard, Alain Filloux, Imperial College London, United Kingdom Bacterial Protein Secretion: Looking inside an injection system
*Ericson CF, *Eisenstein F, Medeiros JM, Malter KE, Calvalcanti G, Zeller RW, Newman DK, Pilhofer M, Shikuma NJ A contractile injection system stimulates tubeworm metamorphosis by translocating a proteinaceous effector
*Shikuma NJ, *Antoshechkin I, Medeiros JM, Pilhofer M, Newman DK Stepwise Metamorphosis of the Tubeworm Hydroides elegans is Mediated by a Bacterial Inducer and MAPK Signaling
*Shikuma NJ,*Pilhofer M, Weiss GL, Hadfield MG, Jensen GJ, Newman DK Marine tubeworm metamorphosis induced by arrays of bacterial phage tail-like structures

Tube Worm Larvae Use Prickly Bacterial Flowers to Choose Home, Scientific American, May 2015
Settlement Signal, The Scientist, January 2014
The Tale of a Tubeworm and a Biofilm, American Society For Microbiology, April 2014