Nanoscale segregation of actin nucleation and elongation factors determines dendritic spine protrusion

• Published in: The EMBO journal 2014-12, Vol.33 (23), p.2745-2764
• Main Authors: Chazeau, Anaël, Mehidi, Amine, Nair, Deepak, Gautier, Jérémie J, Leduc, Cécile, Chamma, Ingrid, Kage, Frieda, Kechkar, Adel, Thoumine, Olivier, Rottner, Klemens, Choquet, Daniel, Gautreau, Alexis, Sibarita, Jean-Baptiste, Giannone, Grégory
• Format: Article
• Language: English
• Subjects: Actin-Related Protein 2-3 Complex - metabolism; Actins - metabolism; Adaptor Proteins, Signal Transducing - metabolism; Animals; branched F-actin regulators; Cells, Cultured; Cytoskeleton; dendritic spine; Dendritic Spines - metabolism; Dendritic Spines - physiology; Dendritic Spines - ultrastructure; EMBO27; Models, Biological; Molecular biology; Morphology; Nerve Tissue Proteins - metabolism; Nucleation; Polymerase Chain Reaction; Post-Synaptic Density - metabolism; postsynaptic density; Proteins; Rats; Rats, Sprague-Dawley; single protein tracking; Spine; Statistics, Nonparametric; super-resolution microscopy; Synaptic Transmission - physiology
• ISSN: 0261-4189; 1460-2075
• DOI: 10.15252/embj.201488837

Actin dynamics drive morphological remodeling of neuronal dendritic spines and changes in synaptic transmission. Yet, the spatiotemporal coordination of actin regulators in spines is unknown. Using single protein tracking and super‐resolution imaging, we revealed the nanoscale organization and dynamics of branched F‐actin regulators in spines. Branched F‐actin nucleation occurs at the PSD vicinity, while elongation occurs at the tip of finger‐like protrusions. This spatial segregation differs from lamellipodia where both branched F‐actin nucleation and elongation occur at protrusion tips. The PSD is a persistent confinement zone for IRSp53 and the WAVE complex, an activator of the Arp2/3 complex. In contrast, filament elongators like VASP and formin‐like protein‐2 move outwards from the PSD with protrusion tips. Accordingly, Arp2/3 complexes associated with F‐actin are immobile and surround the PSD. Arp2/3 and Rac1 GTPase converge to the PSD, respectively, by cytosolic and free‐diffusion on the membrane. Enhanced Rac1 activation and Shank3 over‐expression, both associated with spine enlargement, induce delocalization of the WAVE complex from the PSD. Thus, the specific localization of branched F‐actin regulators in spines might be reorganized during spine morphological remodeling often associated with synaptic plasticity. Synopsis Super‐resolution microscopy reveals how nanoscale organization of F‐actin regulators correlates with changes in neuronal dendritic spine morphology. Branched F‐actin nucleation occurs at the vicinity of the postsynapse density, while elongation occurs at the tip of finger‐like protrusions. Spine morphing and motility are supported by finger‐like protrusions. Actin elongators, VASP and FMNL2, move outwards from the PSD with membrane protrusion tips. The PSD is a persistent confinement zone for IRSp53 and the WAVE complex, being an organization center of branched F‐actin nucleation. Actin elongation from immobile Arp2/3 close to the PSD is not generating a concerted fast rearward flow of Arp2/3 and F‐actin in spines. Dendritic spine enlargement induced by long‐lasting enhancement of Rac1 or Shank3 functions is associated with delocalization of the WAVE complex from the PSD. Graphical Abstract Super‐resolution microscopy reveals how nanoscale organization of F‐actin regulators correlates with changes in neuronal dendritic spine morphology. Branched F‐actin nucleation occurs at the vicinity of the postsynapse density, while elongatio