The distribution of synaptic strengths and possible mechanism for synaptic plasticity arise in the model of inter-spine molecular transport of PSD-95 molecules.
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1
Frankfurt Institute for Advanced Studies, Germany
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2
Max-Planck Institute for Dynamics and Self-Organization, Germany
The scaffolding protein PSD-95 is the most abundant molecule in the 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 PSD cluster and is strongly correlated with the synaptic strength. It is observed that these molecules have high turnover rates and that neighboring spines are constantly exchanging individual molecules.
Here we present a model of non-equilibrium molecular transport between spines in neuronal dendrites describing the dynamics of PSD-95 molecules. When the molecules interact with each other inside the spines of a dendrite due to binding to PSD cluster, the corresponding trapping times inside the spines depend on the size of the PSD cluster and become much longer than the diffusion times in the dendritic shaft. This allows us to obtain the stationary distributions of PSD cluster sizes that emerge from such 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) required for synaptic plasticity. In this scenario, the geometrical filling fraction of the PSD cluster is suggested to be an important characteristic of the synapse that carries the information of the previous LTP events.
Acknowledgements
This work was supported by the German Federal Ministry of Education and Research (BMBF) (01GQ0430).
References
1. Gray NW, Weimer RM, Bureau I, Svoboda K. PLoS Biol. Nov;4(11):e370. (2006)
2. Santamaria F, Wils S, De Schutter E, Augustine GJ. Neuron Nov 22;52(4):635-48. (2006)
3. Evans MR and Hanney T, J. Phys. A: Math. Gen. 39 R195-R240, (2005).
Keywords:
dendritic molecular transport,
LTP,
Model,
post-synaptic denstity,
PSD-95,
synaptic plasticity,
synaptic weights
Conference:
Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012.
Presentation Type:
Poster
Topic:
Learning, plasticity, memory
Citation:
Tsigankov
D and
Eule
S
(2012). The distribution of synaptic strengths and possible mechanism for synaptic plasticity arise in the model of inter-spine molecular transport of PSD-95 molecules..
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference 2012.
doi: 10.3389/conf.fncom.2012.55.00156
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Received:
11 May 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Dr. Dmitry Tsigankov, Frankfurt Institute for Advanced Studies, Frankfurt, 60438, Germany, dmitry@nld.ds.mpg.de