Structural Basis of a Potent Peptide Inhibitor Designed for Kv1.3 Channel, a Therapeutic Target of Autoimmune Disease*

The potassium channel Kv1.3 is an attractive pharmacological target for immunomodulation of T cell-mediated autoimmune diseases. Potent and selective blockers of Kv1.3 are potential therapeutics for treating these diseases. Here we describe the design of a new peptide inhibitor that is potent and selective for Kv1.3. Three residues (Gly11, Ile28, and Asp33) of a scorpion toxin BmKTX were substituted by Arg11, Thr28, and His33, resulting in a new peptide, named ADWX-1. The ADWX-1 peptide blocked Kv1.3 with picomolar affinity (IC50, 1.89 pm), showing a 100-fold increase in activity compared with the native BmKTX toxin. The ADWX-1 also displayed good selectivity on Kv1.3 over related Kv1.1 and Kv1.2 channels. Furthermore, alanine-scanning mutagenesis was carried out to map the functional residues of ADWX-1 in blocking Kv1.3. Moreover, computational simulation was used to build a structural model of the ADWX-1-Kv1.3 complex. This model suggests that all mutated residues are favorable for both the high potency and selectivity of ADWX-1 toward Kv1.3. While Arg11 of ADWX-1 interacts with Asp386 in Kv1.3, Thr28 and His33 of ADWX-1 locate right above the selectivity filter-S6 linker of Kv1.3. Together, our data indicate that the specific ADWX-1 peptide would be a viable lead in the therapy of T cell-mediated autoimmune diseases, and the successful design of ADWX-1 suggests that rational design based on the structural model of the peptide-channel complex should accelerate the development of diagnostic and therapeutic agents for human channelopathies.

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