Identifying synaptic proteins by in vivo BioID from mouse brain

Abstract

Two anatomically and functionally distinct types of synapses are present in the central nervous system, excitatory synapses, and inhibitory synapses. Purification and analysis of the protein complex at the excitatory postsynapses have led to fundamental insights into neurobiology. In contrast, the biochemical purification and analysis of the inhibitory postsynaptic density have been largely intractable. The recently developed method called BioID employs the biotin ligase mutant, BirA*, fused to a bait protein to label and capture proximal proteins. We adapted the BioID approach to enable in vivo BioID, or iBioID of inhibitory synaptic complexes in the mouse brain. This protocol describes the iBioID method to allow synaptic bait proteins to target synaptic complexes, label, and purify biotinylated proteins from the mouse brain. This technique can be easily adapted to target other substructures in vivo that have been difficult to purify and analyze in the past.