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Eur J Pharmacol. 2017 Apr 5;800:40-47. doi: 10.1016/j.ejphar.2017.02.024. Epub 2017 Feb 20.

Chloroquine blocks the Kir4.1 channels by an open-pore blocking mechanism.

Author information

1
Unidad de Investigación "Carlos Méndez" del Centro U. de Investigaciones Biomédicas de la Universidad de Colima, Mexico.
2
Conacyt - Universidad Autónoma de San Luis Potosí. Facultad de Medicina, Ave. V. Carranza 2405, San Luis Potosí, SLP 78290 Mexico.
3
Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico.
4
Department of Physiology and Biophysics, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA.
5
Unidad de Investigación "Carlos Méndez" del Centro U. de Investigaciones Biomédicas de la Universidad de Colima, Mexico. Electronic address: tania@ucol.mx.

Abstract

Kir4.1 channels have been implicated in various physiological processes, mainly in the K+ homeostasis of the central nervous system and in the control of glial function and neuronal excitability. Even though, pharmacological research of these channels is very limited. Chloroquine (CQ) is an amino quinolone derivative known to inhibit Kir2.1 and Kir6.2 channels with different action mechanism and binding site. Here, we employed patch-clamp methods, mutagenesis analysis, and molecular modeling to characterize the molecular pharmacology of Kir4.1 inhibition by CQ. We found that this drug inhibits Kir4.1 channels heterologously expressed in HEK-293 cells. CQ produced a fast-onset voltage-dependent pore-blocking effect on these channels. In inside-out patches, CQ showed notable higher potency (IC50 ≈0.5μM at +50mV) and faster onset of block when compared to whole-cell configuration (IC50 ≈7μM at +60mV). Also, CQ showed a voltage-dependent unblock with repolarization. These results suggest that the drug directly blocks Kir4.1 channels by a pore-plugging mechanism. Moreover, we found that two residues (Thr128 and Glu158), facing the central cavity and located within the transmembrane pore, are particularly important structural determinants of CQ block. This evidence was similar to what was previously reported with Kir6.2, but distinct from the interaction site (cytoplasmic pore) CQ-Kir2.1. Thus, our findings highlight the diversity of interaction sites and mechanisms that underlie amino quinolone inhibition of Kir channels.

KEYWORDS:

Cationic amphiphilic drugs; Chloroquine; Kir4.1 channels

PMID:
28216048
DOI:
10.1016/j.ejphar.2017.02.024
[Indexed for MEDLINE]

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