Regulation of AMPA receptor GluR1 subunit surface expression by a 4.1N-linked actin cytoskeletal association

The synaptic localization, clustering, and immobilization of neurotransmitt er receptors and ion channels play important roles in synapse formation and synaptic transmission. Although several proteins have been identified that interact with AMPA receptors and that may regulate their synaptic targetin g, little is known about the interaction of AMPA receptors with the cytoske leton. In studies examining the interaction of the AMPA receptor GluR1 subu nit with neuronal proteins, we determined that GluR1 interacts with the 4.1 G and 4.1N proteins, homologs of the erythrocyte membrane cytoskeletal prot ein 4.1. Using the yeast two-hybrid system and a heterologous cell system, we demonstrated that both 4.1G and 4.1N bind to a membrane proximal region of the GluR1 C terminus, and that a region within the C-terminal domain of 4.1G or 4.1N is sufficient to mediate the interaction. We also found that 4 .1N can associate with GluR1 in vivo and colocalizes with AMPA receptors at excitatory synapses. Disruption of the interaction of GluR1 with 4.1N or d isruption of actin filaments decreased the surface expression of GluR1 in h eterologous cells. Moreover, disruption of actin filaments in cultured cort ical neurons dramatically reduced the level of surface AMPA receptors. Thes e results suggest that protein 4.1N may link AMPA receptors to the actin cy toskeleton.