Activity dependent regulation of Na,K‐ATPase α3 mobility in the postsynaptic membrane

Abstract

The rapid changes in intracellular Na+ concentration due to excitatory synaptic activity by AMPA receptors are offset by the Na,K‐ATPase which is responsible for restoring the membrane potential and for maintaining a low intracellular level of sodium. Many recent studies describe the dynamics of AMPA receptor diffusion which should consequently modulate the influx of Na+. Though regulation of AMPA receptors and Na,K‐ATPase are likely coordinated, a direct link has never been investigated. In this study we use live cell imaging methods to examine population and single molecule movement of the Na,K‐ATPase a3 isoform and explore a functional regulation associated with AMPA receptor activity. Using Super Ecliptic pHluorin‐tagged al3 and FRAP we measured population mobility in cultured hippocampal neurons. We found that a majority of the Na,K‐ATPase molecules in the dendritic membrane are in lateral diffusion. With quantum dot labeling, we measured the single molecule diffusion in the extrasynaptic and synaptic membranes. After AMPA receptor stimulation the mobility of a3 was significantly increased in both the extrasynaptic and synaptic membranes. Using TTX to inhibit neuronal activity we observed a decreased mobility in the extrasynaptic and synaptic membranes. The alterations seen in response to changes in synaptic activity demonstrate that a3 is functionally regulated in the dendritic membrane.