title: The subspine organization of actin fibers regulates the structure and plasticity of dendritic spines.
abstract: Synapse function and plasticity depend on the physical structure of dendritic spines as determined by the actin cytoskeleton. We have investigated the organization of filamentous (F-) actin within individual spines on CA1 pyramidal neurons in rat hippocampal slices. Using two-photon photoactivation of green fluorescent protein fused to beta-actin, we found that a dynamic pool of F-actin at the tip of the spine quickly treadmilled to generate an expansive force. The size of a stable F-actin pool at the base of the spine depended on spine volume. Repeated two-photon uncaging of glutamate formed a third pool of F-actin and enlarged the spine. The spine often released this "enlargement pool" into the dendritic shaft, but the pool had to be physically confined by a spine neck for the enlargement to be long-lasting. Ca2+/calmodulin-dependent protein kinase II regulated this confinement. Thus, spines have an elaborate mechanical nature that is regulated by actin fibers.
authors.affiliation: Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Honkura
authors.forename: Masanori
authors.initials: M
authors.lastname: Matsuzaki
authors.forename: Jun
authors.initials: J
authors.lastname: Noguchi
authors.forename: Graham C R
authors.initials: GC
authors.lastname: Ellis-Davies
authors.forename: Haruo
authors.initials: H
authors.lastname: Kasai
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000502:physiology; D000199:Actins / Q000737:chemistry* / Q000502:physiology*; D000818:Animals; D049229:Dendritic Spines / Q000737:chemistry* / Q000502:physiology*; D006801:Humans; D009473:Neuronal Plasticity / Q000502:physiology*; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000199:Actins