Darren Finkelstein

Mentors: Justin Du Bois and Bianxiao Cui

Research Summary

Voltage-gated sodium ion channels (NaVs) are large transmembrane proteins that are integral for electrical signaling and nerve conduction. Regulation and maintenance of NaVs in the cellular membrane is vital for proper neuronal function. Investigations of NaV regulation and trafficking, including channel turnover, membrane translocation and transport, inspire the design of chemical tools for selective labeling of NaVs. NaV fluorescent protein conjugates suffer from diminished protein expression levels and improper channel gating kinetics. We have prepared small molecule-based NaV probes patterned after (+)-saxitoxin (STX), a naturally occurring guanidinium toxin, which are selective, reversible, and low nanomolar inhibitors of certain NaV subtypes. Our efforts have given way to both fluorescent and affinity-based toxin derivatives. One of these, a novel trifunctional electrophilic STX derivative bearing both a cysteine-reactive maleimide moiety and fluorescent coumarin dye, has been demonstrated to covalently attach to NaVs and to irreversibly block ion conduction. Whole-cell electrophysiology recordings and fluorescent imaging studies with both recombinant NaV subtypes and primary neuronal cells can confirm that NaV labeling is exclusive to membrane channels. The design, characterization, and application of this and other STX-based probes represent a promising avenue for the study of NaV dynamics.