Identification of an essential binding site for local anesthetics in the ‘side pockets´ of Kv1 channels

Abstract

Background and Purpose: Local anesthetics block sodium and a variety of potassium channels. Although previous studies identified a residue in the pore signature sequence together with three residues in the S6 segment as a putative binding site, the precise molecular basis of Kv potassium channel inhibition by local anesthetics remained unknown. Kv crystal structures predict that some of these residues point away from the central cavity and face into a drug binding site called 'side pockets . Thus, the question arises whether the binding site of local anesthetics is exclusively located in the central cavity or also involves the 'side pockets . Experimental Approach: A systematic functional alanine mutagenesis approach, scanning 58 mutants, in concert with in silico docking experiments and molecular dynamics simulations were utilized to elucidate the binding site of bupivacaine and ropivacaine. Key Results: Kv1.5 inhibition by local anesthetics requires binding to the central cavity and the 'side pockets , where the latter requires interactions with residues of the S5 and the backside of the S6 segment. Mutations in the 'side pockets remove stereoselectivity of Kv1.5 inhibition by bupivacaine. Strikingly, while we found that binding to the 'side pockets is conserved for the different local anesthetics, the binding mode in the central cavity and the 'side pockets shows considerable variations. Conclusion and Implications: Local anesthetics bind to the central cavity and the 'side pockets which provides a crucial key for the molecular understanding of their Kv channel affinity and stereoselectivity, as well as their spectrum of side effects.

Rational Design, Synthesis, and In-Silico Evaluation of Homologous Local Anesthetic Compounds as TASK-1 Channel Blockers

“…The higher affinity of these blockers for TASK-1 channels suggests that TASK-1 could be an unrecognized molecular target of Kv1.5 blockers, effective in AF [11]. In the case of local anesthetics (LAs), it has been observed that bupivacaine and ropivacaine, which block Kv1.5 [12,[14][15][16][17], also act as blockers in TASK-1. In addition, LA lidocaine blockade has been reported on the TASK-1 channel [13,18] (Figure 1).…”