CELL BIOLOGY OF THE NEURON Polarity ... - Tavernarakis Lab
CELL BIOLOGY OF THE NEURON Polarity ... - Tavernarakis Lab
CELL BIOLOGY OF THE NEURON Polarity ... - Tavernarakis Lab
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Cell Biology of the Neuron: <strong>Polarity</strong>, Plasticity and Regeneration, Crete 2011<br />
Evidence for a Mechanical Coupling between N-<br />
Cadherin Adhesions and F-Actin in Shaping Dendritic<br />
Spines<br />
Anaël Chazeau, Katalin Czondor, Mikael Garcia, Grégory Giannone, Olivier<br />
Thoumine<br />
Interdisciplinary Institute for NeuroScience UMR 5297<br />
The dynamic morphology of dendritic spines is controlled by both the actin<br />
cytoskeleton and adhesive molecules such as cadherins. We tested here the<br />
hypothesis that actin remodeling in dendritic spines could be regulated by Ncadherin<br />
adhesion and myosin contractility.<br />
We first examined the localization of N-cadherin, actin and myosin in primary<br />
hippocampal neurons by STED microscopy. Actin-GFP and N-cadherin-DsRed<br />
co-localized mainly at the head of dendritic spines, suggesting a tight association<br />
between the two proteins. In contrast, MLC (myosin light chain)-GFP was more<br />
localized at the spine base, suggesting a role for myosin II in pulling actin<br />
filaments rearward.<br />
We then characterized, the basal motility index of dendritic spines using time<br />
lapse imaging of actin-GFP, upon treatment to increase myosin II activity, or<br />
expression of an N-cadherin mutant. N-Cadherin mutants’ dendritic spines had a<br />
higher motility index than N-Cadherin-WT spines, suggesting that the mechanical<br />
connection between post-synaptic N-cadherin and actin is stabilizing dendritic<br />
spines. Activation of myosin II induced a retraction of actin-GFP spots from the<br />
tip to the base of the spine, suggesting a role for myosin II in generating<br />
retrograde F-actin flow in dendritic spines. Furthermore, for N-Cadherin mutants<br />
the proportion of spines retracting was higher than for N-Cadherin-WT spines. To<br />
refine our understanding of actin flow and motility, we are performing single<br />
molecule experiments (actin-mEos) using PALM.<br />
Taken together, these data show that actin remodeling and flow in dendritic<br />
spines is regulated by N-cadherin adhesion and myosin contractility, suggesting a<br />
tight mechanical coupling between these three molecules.<br />
Presented by: Chazeau, Anaël<br />
99<br />
Poster No 017<br />
Green Session