Stochastic Lattice Model of Synaptic Protein Domains on Cell Membranes

In chemical synapses, neurotransmitter receptor proteins and their associated scaffolds are found in localized domains, which are complex molecular assemblies. The size, stability and plasticity of these domains play a vital role in modulating signal transmission across chemical synapses. Similar to other types of membrane protein domains, synaptic domains are characterized by crowding and low protein copy numbers. As a result, they exhibit stochastic, collective fluctuations that cannot be explained by mean-field methods. Using kinetic Monte Carlo simulations, we study a stochastic lattice model of the reaction-diffusion dynamics at synaptic domains. For simplicity, only receptors and scaffolds are considered. First and foremost, we have observed the self-assembly of synaptic domains. On this basis, we systematically explore the mechanisms underlying their fluctuations in size, lifetime and molecular occupancy. Our work aims to provide a physical understanding of quantitative experimental data on synaptic domains, which are now available and describe both single-molecular and collective dynamics.