The original description of type I (asymmetric) synapses by Gray (1959). (A) Schematic ...
Cartoon representaton of GAG-induced clustering of RPTPsigma, a pre-synaptic receptor (Coles et al, ...
Recombinant expression of a post-synaptic ionotropic glutamate receptor.
Early days of electron microscopy revealed "a band of electron scattering extracellular material" that fills the 20-25 nm cleft separating the plasma membranes of two neurons engaged in a typical chemical synapse in the central nervous system (CNS). Fifty years of progress in neuroscience and molecular biology have greatly improved our understanding of the composition, function and sometimes structure of individual components of this "band". It is now clear that a multitude of adhesion molecules, neurotransmitter and other cell-surface receptors, proteoglycans and secreted proteins establish a complex network of interactions spanning the synaptic cleft. Little is known, however, about the higher order organization of the cleft molecules, once incorporated in a trans-synaptic network of interactions, and virtually nothing about the functional consequences, in both normal and pathological circumstances, of such supra-molecular arrangements.
This project will combine innovative structural biology and molecular neuroscience. Focusing on a prototypical trans-synaptic complex (several options are available, please email if interested in further details) that integrates adhesive and signalling functions, you will solve crystal structures of individual components and complexes and characterize their higher order assemblies by cryo-electron tomography. Molecular level information will be integrated in a functional context (synapse formation assays) and analyzed by fluorescence and X-ray microscopy. The aim is to decipher important principles of synaptic organization and investigate the structural plasticity of trans-synaptic protein assemblies in response to neuronal activity.
My laboratory is based in the Division of Structural Biology, at the Wellcome Trust Centre for Human Genetics. We have full access to a first-class infrastructure for automated large-scale protein production using mammalian cells (and occasionally employ other systems as required), protein purification, high-throughput crystallization, state-of the art cryo-electron microscopy/tomography and live-cell fluorescence microscopy, as well as synchrotron radiation facilities (including the nearby Diamond). Close interactions with collaborators in the UK and abroad will facilitate a broad range of functional experiments and provide further training opportunities.
Protein Science & Structural Biology and Physiology, Cellular & Molecular Biology
Project reference number: 345
| Name | Department | Institution | Country | |
|---|---|---|---|---|
| Dr Alexandru R Aricescu | Structural Biology | Oxford University | UK | radu@strubi.ox.ac.uk |
2011. Proteoglycan-specific molecular switch for RPTPσ clustering and neuronal extension. Science, 332 (6028), pp. 484-8. Read abstract | Read more
Heparan and chondroitin sulfate proteoglycans (HSPGs and CSPGs, respectively) regulate numerous cell surface signaling events, with typically opposite effects on cell function. CSPGs inhibit nerve regeneration through receptor protein tyrosine phosphatase sigma (RPTPσ). Here we report that RPTPσ acts bimodally in sensory neuron extension, mediating CSPG inhibition and HSPG growth promotion. Crystallographic analyses of a shared HSPG-CSPG binding site reveal a conformational plasticity that can accommodate diverse glycosaminoglycans with comparable affinities. Heparan sulfate and analogs induced RPTPσ ectodomain oligomerization in solution, which was inhibited by chondroitin sulfate. RPTPσ and HSPGs colocalize in puncta on sensory neurons in culture, whereas CSPGs occupy the extracellular matrix. These results lead to a model where proteoglycans can exert opposing effects on neuronal extension by competing to control the oligomerization of a common receptor. Hide abstract
2011. Structural basis for cell surface patterning through NetrinG-NGL interactions. EMBO J., 30 (21), pp. 4479-88. Read abstract | Read more
Brain wiring depends on cells making highly localized and selective connections through surface protein-protein interactions, including those between NetrinGs and NetrinG ligands (NGLs). The NetrinGs are members of the structurally uncharacterized netrin family. We present a comprehensive crystallographic analysis comprising NetrinG1-NGL1 and NetrinG2-NGL2 complexes, unliganded NetrinG2 and NGL3. Cognate NetrinG-NGL interactions depend on three specificity-conferring NetrinG loops, clasped tightly by matching NGL surfaces. We engineered these NGL surfaces to implant custom-made affinities for NetrinG1 and NetrinG2. In a cellular patterning assay, we demonstrate that NetrinG-binding selectivity can direct the sorting of a mixed population of NGLs into discrete cell surface subdomains. These results provide a molecular model for selectivity-based patterning in a neuronal recognition system, dysregulation of which is associated with severe neuropsychological disorders. Hide abstract
2010. An extracellular steric seeding mechanism for Eph-ephrin signaling platform assembly. Nat. Struct. Mol. Biol., 17 (4), pp. 398-402. Read abstract | Read more
Erythropoetin-producing hepatoma (Eph) receptors are cell-surface protein tyrosine kinases mediating cell-cell communication. Upon activation, they form signaling clusters. We report crystal structures of the full ectodomain of human EphA2 (eEphA2) both alone and in complex with the receptor-binding domain of the ligand ephrinA5 (ephrinA5 RBD). Unliganded eEphA2 forms linear arrays of staggered parallel receptors involving two patches of residues conserved across A-class Ephs. eEphA2-ephrinA5 RBD forms a more elaborate assembly, whose interfaces include the same conserved regions on eEphA2, but rearranged to accommodate ephrinA5 RBD. Cell-surface expression of mutant EphA2s showed that these interfaces are critical for localization at cell-cell contacts and activation-dependent degradation. Our results suggest a 'nucleation' mechanism whereby a limited number of ligand-receptor interactions 'seed' an arrangement of receptors which can propagate into extended signaling arrays. Hide abstract
2009. Crystal structure of the GluR2 amino-terminal domain provides insights into the architecture and assembly of ionotropic glutamate receptors. J. Mol. Biol., 392 (5), pp. 1125-32. Read abstract | Read more
Ionotropic glutamate receptors are functionally diverse but have a common architecture, including the 400-residue amino-terminal domain (ATD). We report a 1.8-A resolution crystal structure of human GluR2-ATD. This dimeric structure provides a mechanism for how the ATDs can drive receptor assembly and subtype-restricted composition. Lattice contacts in a 4.1-A resolution crystal form reveal a tetrameric (dimer-dimer) arrangement consistent with previous cellular and cryo-electron microscopic data for full-length AMPA receptors. Hide abstract