Max Planck Institute for Dynamics and Self-Organization -- Department for Nonlinear Dynamics and Network Dynamics Group
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BCCN Sonderseminar

Tuesday, 27.09.2011 17 c.t.

Non-equilibrium molecular transport in spiny dendrites and its role in synaptic plasticity

by Dr. Dmitry Tsigankov
from Bernstein Center for Computational Neuroscience, Goettingen

Contact person: Fred Wolf

Location

Ludwig Prandtl Hörsaal, Am Faßberg 11 AI-Gebäude

Abstract

Molecules in neurons are often in a state far from equilibrium. Here we investigate such a case of non-equilibrium molecular transport between spines in neuronal dendrites. When the molecules interact inside the spines of a dendrite, the corresponding trapping times inside the spines become much longer than the diffusion times in the dendritic shaft. Due to the separation of time scales inter-spine molecular dynamics can be formulated as a process called “zero-range” in non-equilibrium statistical physics. In biology, this situation is realized for the scaffolding protein PSD-95, the most abundant molecule in post-synaptic density (PSD) located in the spine, where it forms a cluster to which the membrane synaptic receptors are bound. The amount of PSD-95 molecules inside an individual spine determines the size of the cluster and thus is strongly correlated with the synaptic strength. Here, we discuss the stationary distributions of PSD cluster sizes that emerge from inter-spine molecular dynamics. Our results suggest that spines are competing for a shared pool of PSD-95 molecules in a weak “winner-take-all” regime that is restrained by the finite lifetimes of the PSD-95 molecules. Furthermore, we propose that in the model non-equilibrium inter-spine dynamics of PSD-95 molecules can provide the basis for locally controlled synaptic plasticity through activity-dependent ubiquitination of PSD-95. Thus local rapid destruction of a fraction of the PSD-95 cluster can lead to its growth due to self-organization phenomena, providing the molecular mechanism for maintenance of late long-term potentiation (LTP). In this scenario, the geometrical filling fraction of the PSD cluster is an important characteristic of the synapse that carries the information of the previous LTP events.

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