Chemically Modified ω-Agatoxin IVA Enables Exploration of P/Q-Type Voltage-Dependent Calcium Channels.

P/Q-type voltage-dependent calcium channels (VDCCs) are involved in the regulation of neurotransmitter release and in the integration of dendritic inputs in the central nervous system (CNS). However, their precise localization and protein networks in the CNS remain elusive due to the lack of molecular tools applicable to the delicate and complex three-dimensional environment of the living brain. In this study, we synthesized peptide-based probes using ω-agatoxin IVA (AgTX), a specific channel blocker for P/Q-type VDCCs derived from the funnel-web spider Agelenopsis aperta. The far-red fluorophore-conjugated AgTX probe allowed the visualization of P/Q-type VDCCs in mouse cerebellum at subcellular spatial resolution by CLSM imaging. Moreover, by using a photosensitizer-conjugated AgTX, we successfully conducted photooxidation-driven proximity labeling of P/Q-type VDCCs in fixed mouse brain tissues.