Dendritic Spines

Organization and function of neuronal circuits require not only the interaction between the intrinsic components of the individual neurons but also the synaptic interactions that incorporate them into functional entities. Dendritic spines are the major sites for excitatory synaptic transmission, and are considered as the basic unit of information transfer in nervous system. Structural plasticity of dendritic spines is highly associated with functional plasticity, playing critical roles in learning and memory.
Here, we explored mechanisms underlying PKCα and structural plasticity of dendritic spines. We examined the spatiotemporal activation of actin regulators with 2pFLIM, including small GTPases Rac1, Cdc42 and Ras, in the presence or absence of PKCα during single-spine structural plasticity. Removal of PKCα expression in the postsynapse attenuated Rac1 activation during structural plasticity without affecting Ras or Cdc42 activity. Moreover, disruption of a PDZ binding domain within PKCα led to impaired Rac1 activation and deficits in structural spine remodeling. This work described that PKCα regulates the activation of Rac1, but not Ras or Cdc42, during sLTP of dendritic spines, and this modulation relies on PKCα’s PDZ-binding motif.

Dendritic spines are the major sites for receiving excitatory synaptic inputs and play important roles in neuronal signal transduction, memory storage and neuronal circuit organization. Structural plasticity of dendritic spines is correlated with functional plasticity, and is critical for learning and memory. Visualization of the changes of dendritic spines at the ultrastructural level that specifically correlated with their function changes in high throughput would shed light on detailed mechanisms of synaptic plasticity.
Here we developed a correlative light and electron microscopy workflow which combines two-photon MNI-glutamate uncaging, pre-embedding immunolabeling, Automatic Tape-collecting Ultramicrotome sectioning and scanning electron microscopy imaging. This method bridges two different visualization platforms, directly linking ultrastructure and function at the level of individual synapses. With this method, we successfully relocated single dendritic spines that underwent long-term potentiation (LTP) induced by two-photon MNI-glutamate uncaging, and visualized their ultrastructures and AMPA receptors distribution at different phases of LTP in high throughput.