PT  - JOURNAL ARTICLE
AU  - Jeet Kalia
AU  - Kenton Swartz
TI  - Elucidating the Molecular Basis of Action of a Classical Drug: Guanidine Compounds as Inhibitors of Voltage-gated Potassium Channels
AID  - 10.1124/mol.111.074989
DP  - 2011 Sep 16
TA  - Molecular Pharmacology
PG  - mol.111.074989
4099  - http://molpharm.aspetjournals.org/content/early/2011/09/16/mol.111.074989.short
4100  - http://molpharm.aspetjournals.org/content/early/2011/09/16/mol.111.074989.full
AB  - Guanidine and its alkyl analogs stimulate the neuromuscular junction presynaptically by inhibiting voltage-gated potassium (Kv) channels, leading to enhanced release of acetylcholine in the synaptic cleft. This stimulatory effect of guanidine underlies its use in the therapy for the neuromuscular diseases, myasthenic syndrome of Lambert-Eaton and botulism. The therapeutic use of guanidine is limited, however, due to side effects that accompany its administration. Therefore, the design of guanidine analogs with improved therapeutic indices is desirable. Progress towards this goal is hindered by the lack of knowledge of the mechanism by which these molecules inhibit Kv channels. Here we examine an array of possible mechanisms, including charge screening, disruption of the protein lipid interfaces, direct interaction with the voltage sensors and pore-binding. Our results demonstrate that guanidines bind within the intracellular pore of the channel, and perturb a hydrophobic subunit interface to stabilize a closed state of the channel. This mechanism provides a foundation for the design of guanidine analogs for the therapeutic intervention of neuromuscular diseases.