Our Research - Structural Cell Biology

Molecular rulers in the nervous system

Contactin 1 - neurofascin 155 complex — Contactin 1 and neurofascin 155 control the 7.4 nm distance in the myelin-axon interface

Our ability to move and feel depends on the interaction of neurons and the fatty substance myelin. Two large glycoproteins, neurofascin 155 on the myelin surface and contactin 1 on the neuron surface, each consisting of ten domains, glue the cells together and keep them a tiny bit apart to create just the right conditions for conduction. We zoomed in on the proteins and showed, by X-ray crystallography, small-angle X-ray scattering, interaction experiments, native mass spectrometry and cellular assays that neurofascin 155 and contactin 1 interact using two domains furthest away from the two cell surfaces and that glycans regulate this interaction. One side of the protein acts as the calibrated spacer and the other side contains the flexibility that allows the molecules to reach out over larger distances if they need to, for example in the synapse.

L.M. Chataigner, C. Gogou, M.A. den Boer, C.P. Frias, D.M. Thies-Weesie, J.C. Granneman, A.J. Heck, D.H. Meijer and B.J. Janssen. (2022) ‘Structural insights into the contactin 1 - neurofascin 155 adhesion complex.’ Nature Comms 13:6607 1-17

Teneurin dimer adhesion and conformational changes

Teneurin dimer conformational changes — Ten4 dimer calcium-dependent conformational change

Teneurin transmembrane proteins interact at the neuronal cell surface and between cells to organize synapse formation and wiring of the nervous system. Using a hybrid approach of cryo-EM, X-ray crystallography, small-angle X-ray scattering and cellular assays, together with the group of Dimphna Meijer (Technical University Delft), we show that the Teneurin4 (Ten4) dimer has a compact form in the presence of physiological calcium and undergoes a conformational change when calcium is removed. The compact dimer form supports adhesion between cells and may lead to larger-order organization of the proteins.

D.H. Meijer#, C.P. Frias, J.W. Beugelink, Y.N. Deurloo and B.J. Janssen#. (2022) ‘Teneurin4 dimer structures reveal a calcium-stabilized compact conformation supporting homomeric trans-interactions.’ The EMBO Journal e107505

Teneurin intercellular adhesion — The compact Teneurin4 dimer in cell-cell adhesion

Receptor-ligand interaction mosaic

The Notch-Jagged receptor-ligand system has critical roles in the development and function of many tissues and is associated with several cancers. How the 40 domain Notch1 and 19 domain Jagged1 extracellular regions interact to trigger signaling was not resolved. By using a combination of structural biology, quantitative interaction experiments and cross-linking mass-spectrometry in collaboration with the group of Richard Scheltema (UU) we uncovered an unexpected and intricate interaction mosaic. Functionally important domains, previously thought to be distal, are interacting in the complex, implying an additional level of control in the activation of Notch1 signaling.

M.R. Zeronian*, O. Klykov*, J. Portell I de Montserrat, M.J. Konijnenberg, A. Gaur, R.A. Scheltema# and B.J. Janssen#. (2021) ‘Notch-Jagged signaling complex defined by an interaction mosaic.’ Proc Natl Acad Sci U S A. 27;118(30)

Receptor conformational plasticity and ligand binding

A SorCS2 dimer binds two NGF dimers in a 2:4 stoichiometry

The SorCS2-proneurotrophin signaling system is vital for fundamental functions of our brain, such as metabolic regulation, neuronal wiring and long-term memory formation, and its dysfunction is strongly linked to bipolar disorder, schizophrenia and ADHD.

The structures of unliganded SorCS2 ectodomain and of SorCS2 in complex with nerve growth factor (NGF) reveal the six-domain composition of SorCS2 and substantial SorCS2 plasticity. The NGF dimer binds to a SorCS2 ten-bladed beta-propeller and may trigger a large SorCS2 conformational change.

Ligand bound and free SorCS2 have different conformations

N. Leloup, L.M.P. Chataigner and B.J. Janssen. (2018) ‘Structural insights into SorCS2-Nerve Growth Factor complex formation.’ Nature Comms 9:2979 1-10

A synaptic adhesion molecule with an unusual fold

Cryo-EM reveals an intricate Teneurin 3 domain arrangement

Teneurins help in the development and function of our brain. Their extracellular part can, for example, span the synapse to control its organization and partner matching. In a collaboration with Elena Seiradake (University of Oxford) we have solved the cryo-EM structure of the Teneurin 3 extracellular core. Unusual for an adhesion molecule, the structure reveals a super-fold with eight sub-domains in an intricate arrangement. This Teneurin structure is the first structure solved with the Talos Arctica electron microscope at Utrecht University.

V.A. Jackson, D.H. Meijer, M. Carrasquero, L.S. van Bezouwen, E.D. Lowe, C. Kleanthous, B.J. Janssen and E. Seiradake. (2018) ‘Structures of Teneurin adhesion receptors reveal an ancient fold for cell-cell interaction.’ Nature Comms 9:1079 1-9

Receptor oligomeric and conformational changes control tissue homeostasis

Sortilin dimerizes and undergoes a conformational change at low pH to trigger release of endocytosed cargo's

The transmembrane receptor Sortilin controls the homeostasis of tissues in our body, including our nervous system. Sortilin recognizes and binds a broad range of protein and peptide molecules at the extracellular space between cells. It then shuttles this cargo to the cell inside and releases these ligands for degradation in lysosomes. Sortilin itself is transported back to the cell surface for another round of cargo shuttling.

By using a combination of structural, biophysical and cellular tools we have shown that low pH-induced Sortilin dimerization and conformational change trigger the release of cargo.

N. Leloup, P. Lössl, D.H. Meijer, M. Brennich, A.J. Heck, D.M. Thies-Weesie and B.J. Janssen. (2017) ‘Low pH-induced conformational change and dimerization of sortilin triggers endocytosed ligand release.’ Nature Comms 8:1708 1-16

Protein conformations and interactions in control of adhesion

Cis and trans interactions of MAG and neuronal gangliosides regulate adhesion and signaling in our nervous system

To ensure that nerves can transmit signals rapidly through our nervous system, they are enwrapped by a fatty substance called myelin. The protein myelin-associated glycoprotein (MAG) is responsible for the connection and communication between neurons and myelin-forming cells. When neurons are damaged, for example due to spinal cord injury or a stroke, MAG actively inhibits recovery.

We resolved 3-dimensional structures of the MAG part that bridges the neuronal and myelin cell membranes and that of MAG in complex with its neuronal ligand, a glycolipid. These structures reveal how MAG recognizes its ligand and show that MAG dimerizes through its membrane-proximal domains. Both the MAG dimer formation and the interaction with the glycolipid are important for MAG signaling.

M.F. Pronker, S. Lemstra, J. Snijder, A.J. Heck, D.M. Thies-Weesie, R.J. pasterkamp and B.J. Janssen. (2016) 'Structural basis of myelin-associated glycoprotein adhesion and signalling.' Nature Comms 7:13584 1-3