TY - JOUR T1 - Kir Channel Blockages by Proflavine Derivatives via Multiple Modes of Interaction JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.117.111377 SP - mol.117.111377 AU - Atsushi Inanobe AU - Hideaki Itamochi AU - Yoshihisa Kurachi Y1 - 2018/01/01 UR - http://molpharm.aspetjournals.org/content/early/2018/04/12/mol.117.111377.abstract N2 - Many compounds inhibit tetrameric and pseudo-tetrameric cation channels by associating with the central cavity located in the middle of the membrane plane. They traverse the ion conduction pathway from intracellular side and access to the cavity. Previously we reported that the bacteriostatic agent, proflavine, preferentially blocked a subset of Kir channels. However, the development of the inhibition of Kir1.1 by the compound was obviously different from that operating in Kir3.2 as a pore blocker. To gain mechanistic insights into the compound-channel interaction, we analyzed its chemical specificity, subunit selectivity, and voltage dependency using 13 different combinations of Kir-channel family members and 11 proflavine derivatives. The Kir-channel family members were classified into three groups: (1) Kir2.2, Kir3.x, Kir4.2, and Kir6.2Δ36, which exhibited Kir3.2-type inhibition (slow on-set and recovery, irreversible and voltage-dependent blockage); (2) Kir1.1 and Kir4.1/Kir5.1 (prompt on-set and recovery, reversible and voltage-independent blockage); and (3) Kir2.1, Kir2.3, Kir4.1, and Kir7.1 (no response). The degree of current inhibition depended on the combination of compounds and channels. Chimera between proflavine-sensitive Kir1.1 and -insensitive Kir4.1 revealed that the extracellular portion of Kir1.1 is crucial for the recognition of proflavine derivative, acrinol. In conclusion, preferential blockage of Kir-channel family members by proflavine derivatives is based on multiple modes of action. This raises the possibility to design subunit-specific inhibitors. ER -