Structure-function studies of neuropilin signaling complexes

Ligand-mediated clustering of cell surface receptor domains into precise geometric architectures is required to elicit intracellular signaling cascades. One example is Neuropilin, which is a non-signalling transmembrane glycoprotein shared between important biological processes such as axon guidance, angiogenesis, and cell adhesion. Although the cell biology, biochemistry, and genetics of Neuropilin and related family members are well characterized through extensive studies, limited structural information is available on the interactions of neuropilin with its cellular receptors and ligands.  Our research is focussed on providing a stuctural basis for understanding and further exploring the multifaceted interactions of human neuropilins with their cellular receptors and ligands, which have important implications to cancer development. We use crystallography in combination with electron microscopy and biochemical experiments to provide a detailed view of these interactions and contribute to the understanding of the molecular mechanisms of receptor activation. Structural characterization of these interactions at atomic resolution is pivotal to both basic and applied research in this field, as novel strategies targeting such interfaces have a much greater selectivity for tumor tissue and decreased risk of side effects, compared to conventional cancer treatments.

Projects

1.Neuropilin-VEGF-VEGFR-interactions

Vascular endothelial growth factors, VEGFs, regulate blood and lymph vessel formation during embryonic development and in wound healing, and maintain vessel homeostasis in adult organisms. VEGF family proteins are expressed in multiple isoforms with distinct receptor specificity and biological activity.
VEGF receptor (VEGFR) tyrosine kinases signal to downstream targets upon ligand-induced tyrosine phosphorylation. Neuropilins and heparan sulfate proteoglycans act as coreceptors that lack enzymatic activity, yet modulate signal output by VEGF receptors. We are interested in the structural aspects of the binding of neuropilin-1 and -2 to their VEGF ligands associated with angiogenesis.

2. Signaling initiation by class 3 semaphorins

Axon guidance represents a key stage in the formation of a neural network. Axons are guided by a variety of guidance factors, such as semaphorins, ephrins and netrin. Plexins function as receptors for the repulsive axonal guidance molecules semaphorins. Intracellular domains of plexins are responsible for initiating cellular signal transduction inducing axon repulsion. Neuropilins are co-receptors in the semaphorin/plexin signaling complex.
Sema3A binds with high affinity exclusively to Nrp-1 and mediates the repulsion of sensory axons and growth cone collapse through Nrp-1 in vitro and in vivo. By contrast, Sema3F binds with high affinity and signals exclusively through Nrp-2, while other class 3 semaphorins, such as Sema3B, bind to and transduce signals through both neuropilins.
In growth cones, Nrp-1 and PlexA1 form a receptor complex for Sema3A. The molecular mechanisms that govern this network of interactions are still poorly understood. We are interested in the organization of the Nrp-1/PlexA1/Sema3A receptor complex in general, and especially in the features that govern ligand-receptor specificity in these receptor complexes. We are employing structural and biophysical methods to investigate the nature of these interactions.

People

Andrea Prota (Project leader)

Felix Grünewald (Ph.D. Student)

Dominik Frei (Ph.D. Student)

Hanna Sundström (Postdoc)

Selected Publications

Cébe-Suarez, S., Grünewald, F., Jaussi, R., Li, X., Claesson-Welsh, L., Spillmann, D., Mercer, A.A., Prota, A.E., Ballmer-Hofer, K., Orf virus VEGF-E NZ2 promotes paracellular NRP-1/VEGFR-2 coreceptor assembly via the peptide RPPR, FASEB J 2008, 22, 3078-86

Wagner, A., Pieren, M., Schulze-Briese, C., Ballmer-Hofer, K. and Prota, A.E., Structure Determination of VEGF-E by Sulfur-SAD, Acta Cryst. D62,
1430-1434 (2006)

Prota, A.E., Pieren, M., Ruch, C., Kostrewa, D., Wagner, A., Biedermann, K., Winkler, F.K. and Ballmer-Hofer, K., Crystal Structure of the Orf Virus NZ2 Variant of VEGF-E: Implications for Receptor Specificity, J Biol Chem. 2006, Jul 14;281(28):19578-87.

Lingaraju, G.M., Sartori, A.A., Kostrewa, D., Prota, A.E., Jiricny, J. and Winkler, F.K., A DNA glycosylase from Pyrobaculum aerophilum with a novel 8-oxoguanine binding mode and a noncanonical helix-hairpin-helix structure, Structure (Camb) 2005, Jan;13(1): 87-89

Cavalli, A., Prota, A.E., Stehle, T., Dermody, T.S., Recanatini, M., Folkers, G. and Scapozza, L., A molecular dynamics study of reovirus attachment protein s1 reveals conformational changes in σ1 structure, Biophysical Journal 2004, June;86(6): 3423-31

Prota, A.E., Campbell, J.A., Schelling, P., Forrest, J.C., Watson, M.J., Peters, T.R., Aurrand-Lions, M., Imhof, B.A., Dermody, T.S. and Stehle, T., Crystal Structure of human Junction Adhesion Molecule 1: Implications for reovirus binding, PNAS 2003 Apr 29; 100 (9):5366-71

Prota, A.E., Sage, D., Stehle, T. and Fingeroth, J., The Crystal Structure of human CD21: Implications for Epstein-Barr virus and C3d binding, PNAS 2002 Aug 6;99(16):10641-46

Prota, A.E., Chappell, J.D., Dermody, T.S. and Stehle, T., Crystal Structure Of Reovirus Attachment Protein σ1 Reveals Evolutionary Relationship To Adenovirus Fiber, EMBO J. Vol.21 No.2 (2002) 1-11

Address

Paul Scherrer Institut
Biomolecular Research
Structural Biology / OFLC 103
CH-5232 Villigen-PSI
Switzerland

Phone:      +41-56-310-5160
Fax:          +41-56-310-5288
E-mail: andrea.prota at psi.ch