The trafficking proteins Vacuolar Protein Sorting 35 and Neurobeachin interact with the glycine receptor β-subunit

Inhibitory glycine receptors (GlyRs) are densely packed in the postsynaptic membrane due to a high-affinity interaction of their beta-subunits with the scaffolding protein gephyrin. Here, we used an affinity-based proteomic approach to identify the trafficking proteins Vacuolar Protein Sorting 35 (Vps35) and Neurobeachin (Nbea) as novel GlyR beta-subunit (GlyR beta) interacting proteins in rat brain. Recombinant Vps35 and a central fragment of Nbea bound to the large intracellular loop of GlyR beta in glutathione-S-transferase pull-downs; in addition, Vps35 displayed binding to gephyrin. Immunocytochemical staining of spinal cord sections revealed Nbea immunoreactivity apposed to and colocalizing with marker proteins of inhibitory synapses. Our data are consistent with roles of Vps35 and Nbea in the retrieval and post-Golgi trafficking of synaptic GlyRs and possibly other neurotransmitter receptors. (C) 2011 Elsevier Inc. All rights reserved.