Regulation of synaptic inhibition by phosphodependent binding of the AP2 complex to a YECL motif in the [GABA.sub.A] receptor [gamma]2 subunit

The regulation of the number of [gamma]2-subunit-containing GAB[A.sub.A] receptors (GAB[A.sub.A]RS) present at synapses is critical for correct synaptic inhibition and animal behavior. This regulation occurs, in part, by the controlled removal of receptors from the membrane in clathrin-coated vesicles, but it remains unclear how clathrin recruitment to surface [gamma]2-subunit-containing GAB[A.sub.A]RS is regulated. Here, we identify a [gamma]2-subunit-specific Yxx[phi]-type-binding motif for the clathrin adaptor protein, AP2, which is located within a site for [gamma]2-subunit tyrosine phosphorylation. Blocking GAB[A.sub.A]R-AP2 interactions via this motif increases synaptic responses within minutes. Crystallographic and biochemical studies reveal that phosphorylation of the Yxx[phi] motif inhibits AP2 binding, leading to increased surface receptor number. In addition, the crystal structure provides an explanation for the high affinity of this motif for AP2 and suggests that [gamma]2-subunit-containing heteromeric GAB[A.sub.A]RS may be internalized as dimers or multimers. These data define a mechanism for tyrosine kinase regulation of GAB[A.sub.A]R surface levels and synaptic inhibition. endocytosis | phosphorylation | structure | synaptic transmission | tyrosine kinase