ADF/Cofilin-Mediated Actin Dynamics Regulate AMPA Receptor Trafficking during Synaptic Plasticity

Dendritic spines undergo actin-based growth and shrinkage during synaptic plasticity. The actin depolymerizing factor (ADF)/cofilin family of actin-associated proteins plays important roles in spine plasticity. Elevated ADF/cofilin activities often lead to reduced spine size and immature spine morphology, but can enhance synaptic potentiation in some cases. Therefore ADF/cofilin may exert distinct effects on postsynaptic structure and function. Here we report that ADF/cofilin-mediated actin dynamics regulate AMPA receptor (AMPAR) trafficking during synaptic potentiation, which is distinct from actin's structural role in spine morphology. We find that elevated ADF/cofilin activity markedly enhances surface addition of AMPARs after chemically-induced LTP (cLTP), whereas inhibition of ADF/cofilin abolishes AMPAR addition. Our data further show that cLTP elicits a temporal sequence of ADF/cofilin dephosphorylation and phosphorylation that underlies AMPAR trafficking and spine enlargement. These findings suggest a novel role for temporally-regulated ADF/cofilin activities in postsynaptic modifications of receptor number and spine size during synaptic plasticity.