An aggregation-removal model for the formation and size determination of post-synaptic scaffold domains

PLoS Comput Biol. 2017 Apr 24;13(4):e1005516. doi: 10.1371/journal.pcbi.1005516. eCollection 2017 Apr.

Abstract

The formation and stability of synapses are key questions in neuroscience. Post-synaptic domains have been classically conceived as resulting from local insertion and turnover of proteins at the synapse. However, insertion is likely to occur outside the post-synaptic domains and advances in single-molecule imaging have shown that proteins diffuse in the plane of the membrane prior to their accumulation at synapses. We quantitatively investigated this scenario using computer simulations and mathematical analysis, taking for definiteness the specific case of inhibitory synapse components, i.e., the glycine receptor (GlyR) and the associated gephyrin scaffolding protein. The observed domain sizes of scaffold clusters can be explained by a dynamic balance between the aggregation of gephyrin proteins diffusing while bound to GlyR and their turnover at the neuron membrane. We also predict the existence of extrasynaptic clusters with a characteristic size distribution that significantly contribute to the size fluctuations of synaptic domains. New super-resolution data for gephyrin proteins established the existence of extrasynaptic clusters the sizes of which are consistent with the model predictions in a range of model parameters. At a general level, our results highlight aggregation with removal as a non-equilibrium phase separation which produces structures of tunable size.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carrier Proteins / chemistry
  • Carrier Proteins / metabolism
  • Cells, Cultured
  • Computer Simulation
  • Membrane Proteins / chemistry
  • Membrane Proteins / metabolism
  • Models, Neurological*
  • Neurons / metabolism*
  • Particle Size
  • Rats, Sprague-Dawley
  • Receptors, Glycine / chemistry
  • Receptors, Glycine / metabolism
  • Spinal Cord / cytology
  • Synapses / chemistry*
  • Synapses / metabolism*

Substances

  • Carrier Proteins
  • Membrane Proteins
  • Receptors, Glycine
  • gephyrin

Grant support

JR was supported by a research fellowship from the Deutsche Forschungsgemeinschaft (RA 2571/1-1; http://www.dfg.de). PCR was supported by a Marie Curie International Incoming Fellowship within the 7th European Community Framework Programme (https://ec.europa.eu/research/fp7/). LGA was supported by the Human Brain Project. The experimental work was supported by Agence Nationale de la Recherche (Syntaptune), the ERC advanced research grant (PlasltInhib) and the “Investissements d’Avenir” program (ANR-10-LABX-54 MEMO LIFE). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.