Spatiotemporal maps of CaMKII in dendritic spines

Abstract

The calcium calmodulin dependent kinase (CaMKII) is important for long-term potentiation at dendritic spines. Photo-activatable GFP (PaGFP) - CaMKII fusions were used to map CaMKII movements between and within spines in dissociated hippocampal neurons. Photo-activated PaGFP (GFP*) generated in the shaft spread uniformly, but was retained for about 1 s in spines. The differential localization of GFP*-CaMKII isoforms was visualized with hundred nanometer precision frame to frame using de-noising algorithms. GFP*-CaMKIIα localized to the tips of mushroom spines. The spatiotemporal profiles of native and kinase defective GFP*-CaMKIIβ, differed markedly from GFP*-CaMKIIα and mutant GFP*-CaMKIIβ lacking the association domain. CaMKIIβ bound to cortical actin in the dendrite and the stable actin network in spine bodies. Glutamate produced a transiently localized GFP*-CaMKIIα fraction and a soluble GFP*-CaMKIIβ fraction in spine bodies. Single molecule simulations of the interplay between diffusion and biochemistry of GFP* species were guided by the spatiotemporal maps and set limits on binding parameters. They highlighted the role of spine morphology in modulating bound CaMKII lifetimes. The long residence times of GFP*-CaMKIIβ relative to GFP*-CaMKIIα followed as consequence of more binding sites on the actin cytoskeleton than the post-synaptic density. These factors combined to retain CaMKII for tens of seconds, sufficient to outlast the calcium transients triggered by glutamate, without invoking complex biochemistry.

β-adrenergic signaling broadly contributes to LTP induction

“…In constructing the spine molecular signature, we evaluated molecules that are implicated in synaptic tagging, AMPA receptor insertion, actin remodeling and structural plasticity [ 72 , 79 – 82 ] ( Fig 13 ). Blocking CaMKII activity [ 61 – 63 ] has been shown to block tagging, and CaMKII also is implicated in the actin remodeling underlying structural plasticity [ 83 – 85 ] by triggering SynGAP dispersion from synaptic spines [ 86 ]. PKA is required for synaptic tagging [ 56 , 66 , 87 , 88 ] and is implicated in structural plasticity.…”

Synaptic Signaling in Learning and Memory

“…These high levels of expression, at least 10 times higher than those of other signaling enzymes, are a specialization of excitatory neurons, which represent most of the mass of the forebrain (Sik et al 1998). CaMKII is present throughout the cytosol of somas, axons, and dendrites, including spines in which it is present both in the cytosol and the PSD Chen et al 2005;Khan et al 2012). Activation of synaptic NMDARs increases association of CaMKII with spines and the PSD; however, the role and mechanism of this translocation are still incompletely understood (Khan et al 2012).…”

“…CaMKII is present throughout the cytosol of somas, axons, and dendrites, including spines in which it is present both in the cytosol and the PSD Chen et al 2005;Khan et al 2012). Activation of synaptic NMDARs increases association of CaMKII with spines and the PSD; however, the role and mechanism of this translocation are still incompletely understood (Khan et al 2012).…”

Membrane and actin reorganization in electropulse-induced cell fusion

“…Smoldyn is a particle-based stochastic simulation tool for reaction-diffusion systems in user-defined geometries. This tool has recently been used to simulate sequestration of CaMKII in neural dendritic spines (Khan et al, 2012) and to investigate diffusion constraints in the nuclear membrane of budding yeast during cell division (Boettcher et al, 2012). …”