TY - JOUR T1 - Engineering a Stable and Selective Peptide Blocker of the Kv1.3 Channel in T Lymphocytes JF - Molecular Pharmacology JO - Mol Pharmacol SP - 762 LP - 773 DO - 10.1124/mol.108.052704 VL - 75 IS - 4 AU - M. W. Pennington AU - C. Beeton AU - C. A. Galea AU - B. J. Smith AU - V. Chi AU - K. P. Monaghan AU - A. Garcia AU - S. Rangaraju AU - A. Giuffrida AU - D. Plank AU - G. Crossley AU - D. Nugent AU - I. Khaytin AU - Y. LeFievre AU - I. Peshenko AU - C. Dixon AU - S. Chauhan AU - A. Orzel AU - T. Inoue AU - X. Hu AU - R. V. Moore AU - R. S. Norton AU - K. G. Chandy Y1 - 2009/04/01 UR - http://molpharm.aspetjournals.org/content/75/4/762.abstract N2 - Kv1.3 potassium channels maintain the membrane potential of effector memory (TEM) 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 Lys411 of the channel. ShK-192 blocks Kv1.3 with an IC50 of 140 pM and exhibits greater than 100-fold selectivity over closely related channels. After a single subcutaneous injection of 100 μg/kg, ∼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 TEM cells and suppresses delayed type hypersensitivity when administered at 10 or 100 μg/kg by subcutaneous injection once daily. ShK-192 has potential as a therapeutic for autoimmune diseases mediated by TEM cells. The American Society for Pharmacology and Experimental Therapeutics ER -