Synapses et dynamique moléculaire La synapse, une nanomachine stochastique

Molecules are starlings in the sky

IBEns

Inserm

Institut de Biologie de l’Ecole Normale Supérieure

Communication between neurons take place at synapses

PRD PRD

Most synaptic receptors form microdomains stabilized by scaffolds
23

Spinal cord neuron

Inhibitory Synapse

Neuroligin 2/3

Betz et al. Since 1984

Excitatory Synapse

In fact, a network of molecular interactions, and some data on molecular localization

Inhibitory Synapse

Excitatory Synapse

Constraints & cell biology

• Turnover of receptors (global and local) • The number of receptors varies (development and plasticity) • Most receptors are inserted and removed at non-synaptic loci

Singer-Nicholson the fluid mosaic model (1972) Diffusion result from a collective behavior of proteins and lipids

QD

GFP-GPI

Renner J Neurosci 2009

Singer-Nicholson the fluid mosaic model (1972) Diffusion result from a collective behavior of proteins and lipids

QD

GFP-GPI

homer QD

+

From Kusumi Cultured hippocampal neurons (24 DIV) Renner J Neurosci 2009

Membrane exploration & dynamics of GlyR-Qdots

13 Hz

Cumul. probability

75 ms integration

1

Diffusion

0.5

μm2/s 10-3

Cultured spinal cord neuron

10-2

10-1

Dahan, Lévi et al. Science 03

The “in-out” equilibrium at steady state

Ehrensperger & al. Biophys. J 2007

Stable synapse and kinetics at equilibrium

k1

insertion

Rx

Rz

RzSz

k2

k3

k3

k4

internalization

RzSz*

RxSx Triller and Choquet Neuron 2008 Ehrensperger Biophys. J 2007

The synapse paradox: plasticity despite stability, stability despite plasticity Compatibility between itinerant receptors and stable postsynaptic structure

Stabilization

Dynamic Equilibrium Regulated confinement

Synaptic activity modify intracellular calcium & control GlyR lateral diffusion

F / F0

Ctx

TTX

1.0 0.8 0.5 0.2

0

5

10

15

D (μm2 s-1)

25

30sec

TTX

0.7 0.5 0.3 0.1

Ctl 100

4-AP 50mM and TTX 1mM

20

200

300

400

500

Nb frames

9div spinal cord neurons loaded with Fluo4

Cultured spinal cord neurons

Sabine Lévi et al. Neuron 2008

Activity regulates GABAA
2R confinement at synapses Activity

Activity x10-2

Control (245)

MSD (μm2)

10

10

CNQX+AP5(145) TTX(221) 5

5

Control (747) 4AP(486) St+SR(174) Time (s) 0

0 0

0.5

1.0

1.5

0

0.5

1.0

1.5

Hippocampal neurons 21 days IV Bannai et al Neuron 2009

Correlation between Ca2+ and GABA
2R Mobility

Winthin synapses

x10-1 0.4

Conf. size (μm)

Dmedian (μm2/s)

0.4 0.3 0.2 0.1

0.5

1.0

1.5

0.3

0.2

0.5

2.0

Norm. Fluo-4 Intensity

Control 4AP

St+Gz

TTX 4AP+St+Gz

1.0

1.5

2.0

Norm. Fluo-4 Intensity

CNQX+APV 4AP+EGTA

4AP+CNQX

4AP+APV

4AP+ 2APB+ Ry

4AP+TTX

4AP+ nife 4AP+CNQX+APV

Bannai et al Neuron 2009

Reactive Ca2+ tuning of excitation/inhibition

AMPAR

GABAR

Mobility

Ca2+

Confinement

Ca2+ Borgdorf & Choquet 2002,Tardin et al. 2003

Bannai et al Neuron 2009

Diffusion parameters & “synaptic reactivity” GABA receptor: anti-homeostatic reactivity


 


hippocampal neurons


 


S327

Ca2+ CaM

CN

Ca PO N3

“Synaptic Reactivity” results form the diffusion in the PM Lateral diffusion is regulated by biological process --> Rapid and reversible regulation of synaptic inhibiton

The scale jump

Anatomic

Inserm IBEns Marianne Cécile Claire Patricia Géraldine Kim Toru

RENNER CHARRIER RIBRAULT MACHADO GOUZER GEROW SHINOUE

CNRS Bordeaux Daniel CHOQUET

BSI Riken Institute Wako Shi Katsuhro MIKOSHIBA Hiroko BANNAI Thomas LAUNEY

Andrea Damien Chistian Claude Hiroko Sabine

Institut de Biologie de L
Ecole Normale Supérieure DUMOULIN ALCOR SPECHT SCHWEIZER* BANNAI* LEVI*

CNRS-LKB Physic Dpt ENS Maxime DAHAN Marie-Virginie EHRENSPERGER ESPCI-Univ René Descartes Paris Ken SEKIMOTO Mathematic & Biology Dpt ENS David HOLCMAN CNRS-LPS Physic Dpt ENS Rava A. DA SILVEIRA