UCSF

The activity-regulated cytoskeleton-associated protein, Arc, is known to promote the internalization of surface AMPA-type glutamate receptors in neurons and is thought to do so via physical interactions with the endocytic machinery. However, the specific molecular pathway linking Arc to the trafficking of AMPA receptors remains unknown. In this study, we find that Arc knockdown in cultured rat cortical neurons slows the rate of endocytosis of pHluorin-tagged GluA1 AMPA receptor subunits in response to direct AMPA receptor activation but has no effect on the endocytosis of pHluorin-tagged GluA2 in response to either AMPA or NMDA stimulation. We further demonstrate that this effect is specific to the AMPA-induced endocytosis of homomeric GluA1 receptors and that Arc knockdown has no effect on the rapid endocytosis of heteromeric AMPA receptors containing both GluA1 and GluA2. We report a novel binding interaction between Arc and the E3 ubiquitin ligase Nedd4-1 as identified in an unbiased yeast two-hybrid screen and show that the effect of reduced Arc expression on GluA1 endocytosis is occluded both by Nedd4-1 knockdown and by a variant of GluA1 that can not be ubiquitinated by Nedd4-1. Together, our results demonstrate a subtype-specific role for Arc in the endocytic response to direct AMPA receptor stimulation in cultured cortical neurons and suggest that this specificity may be conferred by the substrate preference of Nedd4-1.