Referenced in: none

Automatically associated channels: Kv1.3

Title: Engineering a stable and selective peptide blocker of the Kv1.3 channel in T lymphocytes.

Authors: M W Pennington, C Beeton, C A Galea, B J Smith, V Chi, K P Monaghan, A Garcia, S Rangaraju, A Giuffrida, D Plank, G Crossley, D Nugent, I Khaytin, Y Lefievre, I Peshenko, C Dixon, S Chauhan, A Orzel, T Inoue, X Hu, R V Moore, R S Norton, K G Chandy

Journal, date & volume: Mol. Pharmacol., 2009 Apr , 75, 762-73

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/19122005

Abstract
Kv1.3 potassium channels maintain the membrane potential of effector memory (T(EM)) T cells that are important mediators of multiple sclerosis, type 1 diabetes mellitus, and rheumatoid arthritis. The polypeptide ShK-170 (ShK-L5), containing an N-terminal phosphotyrosine extension of the Stichodactyla helianthus ShK toxin, is a potent and selective blocker of these channels. However, a stability study of ShK-170 showed minor pH-related hydrolysis and oxidation byproducts that were exacerbated by increasing temperatures. We therefore engineered a series of analogs to minimize the formation of these byproducts. The analog with the greatest stability, ShK-192, contains a nonhydrolyzable phosphotyrosine surrogate, a methionine isostere, and a C-terminal amide. ShK-192 shows the same overall fold as ShK, and there is no evidence of any interaction between the N-terminal adduct and the rest of the peptide. The docking configuration of ShK-192 in Kv1.3 shows the N-terminal para-phosphonophenylalanine group lying at the junction of two channel monomers to form a salt bridge with Lys(411) of the channel. ShK-192 blocks Kv1.3 with an IC(50) of 140 pM and exhibits greater than 100-fold selectivity over closely related channels. After a single subcutaneous injection of 100 microg/kg, approximately 100 to 200 pM concentrations of active peptide is detectable in the blood of Lewis rats 24, 48, and 72 h after the injection. ShK-192 effectively inhibits the proliferation of T(EM) cells and suppresses delayed type hypersensitivity when administered at 10 or 100 microg/kg by subcutaneous injection once daily. ShK-192 has potential as a therapeutic for autoimmune diseases mediated by T(EM) cells.