Membrane signaling complexes : role of transmembrane domain interactions – interferenceTM

The significance of selected receptor transmembrane domains interactions was evaluated using different techniques. A genetic screening assay in bacteria was developed to evidence the interactions, some of which were further characterized using computer modelisation. Finally various biochemical and imaging techniques were used to demonstrate inhibitory effects of synthetic peptides in cell cuture and animal models.

A summary of the main results of this project :
• A bacterial genetic screening system and computer modeling demonstrated new interactions between the transmembrane domains of Neuropilins and Plexins.
• Inhibitory synthetic molecules (peptides) were characterized for these receptors in cellular and animal models of breast and brain cancer.
• Another synthetic peptide was also shown to inhibit a growth factor receptor in a breast cancer model.
• Computer modeling defined precisely the involved interaction motifs, which will pave the way for the design of smaller and potentially more efficient inhibitory molecules.
• The development of a bacterial genetic screening system should allow for a more systematic discovery of such interactions, that could be targeted by specific inhibitors.

This work will permit the development of novel molecules, targeting functional interactions between transmembrane domains of many receptors important in human diseases. Our approach was proven as effective in the case of two different families of such receptors. The combination of methods as diverse as computer modeling, bacterial genetic screening and sophisticated cellular biology and imaging techniques deserves further expansion .

This project has yielded so far one publication in an international journal, and four more manuscripts are currently under review
• Duneau JP, Sturgis JN. Lateral organization of biological membranes: role of long-range interactions. Eur Biophys J. (2013) 42: 843-50.
• Alexia Arpel, Paul Sawma, Caroline Spenlé, Norbert Garnier, Inés Velázquez-Quesada, Thomas Hussenet, Samia Aci-Sèche,4, Nadège Baumlin, Monique Genest, David Brasse, Pierre Hubert, Gérard Crémel, Gertraud Orend, Patrice Laquerrière and Dominique Bagnard.
Transmembrane domain targeting peptide antagonizing ErbB2/Neu inhibits breast tumor growth and metastasis.
• Samia Aci-Sèche, Paul Sawma, Pierre Hubert, James Sturgis, Dominique Bagnard, Laurent Jacob, Monique Genest and Norbert Garnier. Transmembrane recognition of the semaphorin
co-receptors neuropilin 1 and plexin A1. Coarse-grained simulations.
• Paul Sawma, Lise Roth, Cécile Blanchard, Dominique Bagnard, Gérard Crémel, Emmanuelle Bouveret, Jean-Pierre Duneau, James Sturgis and Pierre Hubert. Homotypic and heterotypic interactions between transmembrane helices of proteins involved in receptor tyrosine kinase
and neuropilin signaling.
• Laurent Jacob, Paul Sawma, Norbert Garnier, Lionel Meyer, Justine Fritz, Thomas Hussenet, Caroline Spenlé, Jacky Goetz, Julien Vermot, Aurore Fernandez, Nadège Baumlin, Samia Aci- Sèche, Gertraud Orend, Pierre Kehrli, Guy Roussel, Gérard Crémel, Monique Genest, Pierre Hubert and Dominique Bagnard. Inhibition of Plexin-A1-mediated brain tumor growth and tumor-associated angiogenesis using transmembrane domain targeting peptide.

Three academic groups representing cell biology, molecular biophysics and computational chemistry propose to investigate neuropilins signalling platforms and their potential as drug targets. Neuropilins are cell surface receptors that play a central role in the development and maintenance of the nervous and vascular systems. Signal mediation relies on their interactions with multiple other membrane proteins, interactions that are at the centre of this request. The assembly of these signalling complexes is poorly understood to date, although neuropilins play a role in diseases of the nervous system, as well as cancer, and are considered as promising drug targets.

The Strasbourg (D. Bagnard) and Marseille (J. Sturgis, P. Hubert) groups have recently demonstrated that a peptide corresponding to the native transmembrane (TM) sequence of neuropilin 1 inhibits selectively neuropilin signalling both in vitro and in vivo (Roth et al. Mol. Biol. Cell 2008; Nasarre et al. Oncogene 2010). This short peptide is an extremely potent antagonist in all assays performed so far, it is thus a very promising venture to explore in greater details the molecular mechanisms of signaling platforms assembly through TM interactions by biochemical, biophysical anf computer modeling techniques; as well as determining the pharmacological properties of selected peptides or peptidomimetic stuctures.

Focusing on the role of the TM domains is a novel research avenue that will certainly be useful in many areas of membrane biology and biotechnology while possessing an extraordinary therapeutic potential in the long run.