Optochemical Proximity Labeling for Mapping Endogenous Receptor Networks in the Live Mouse Brain

Elucidating the protein-protein interaction networks (interactomes) of neurotransmitter receptors is essential for understanding complex brain functions such as learning and memory. However, conventional analytical approaches often require genetic modification, which can potentially perturb physiological functions, and they generally lack sufficient temporal resolution to track dynamic interaction changes in vivo. Here, we describe representative experimental protocols for PhoxID, a recently developed light-driven proximity labeling technique. This method enables the identification of interactomes of endogenous neurotransmitter receptors, such as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, type A γ-aminobutyric acid (GABA_A) receptors, and glutamate receptor ionotropic δ2 (GluD2) in the living mouse brain with high spatiotemporal resolution. In principle, PhoxID can be applied to virtually any protein target, and it is therefore expected to develop into a powerful research tool for dissecting brain function at the molecular level.