Translocation of CaMKII to dendritic microtubules supports the plasticity of local synapses

The processing of excitatory synaptic inputs involves compartmentalized dendritic Ca²⁺ oscillations. The downstream signaling evoked by these local Ca²⁺ transients and their impact on local synaptic development and remodeling are unknown. Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is an important decoder of Ca²⁺ signals and mediator of synaptic plasticity. In addition to its known accumulation at spines, we observed with live imaging the dynamic recruitment of CaMKII to dendritic subdomains adjacent to activated synapses in cultured hippocampal neurons. This localized and transient enrichment of CaMKII to dendritic sites coincided spatially and temporally with dendritic Ca²⁺ transients. We show that it involved an interaction with microtubular elements, required activation of the kinase, and led to localized dendritic CaMKII autophosphorylation. This process was accompanied by the adjacent remodeling of spines and synaptic AMPA receptor insertion. Replacement of endogenous CaMKII with a mutant that cannot translocate within dendrites lessened this activity-dependent synaptic plasticity. Thus, CaMKII could decode compartmental dendritic Ca²⁺ transients to support remodeling of local synapses.