Mechanism of BK Channel Inhibition by the Opioid Agonist Loperamide

Vouga, Alexandre G.; Rockman, Michael E.; Jacobson, Marlene A.; Rothberg, Brad S.

doi:10.1016/j.bpj.2018.11.2919

Cited by 3 publications

(5 citation statements)

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“…The agonists included were BC5 (18), NS1619 (52, 53) and Cym04 (52). The antagonists were charybdotoxin (ChTX) (46), iberiotoxin (IbTX) (47), loperamide (LOP) (48), paxilline (PAX) (49), and TEA (50, 51). The endogenous modulators were Heme (54), protons (H + ) (55), lipids (56), carbon monoxide (CO) (57), kinases (58) and ethanol (EtOH) (59).…”

Section: Methodsmentioning

confidence: 99%

Section: Pharmacological and Intracellular Modulatorsmentioning

confidence: 99%

“…The agonists included were BC5 (Guohui Zhang et al, 2022), NS1619 (Gessner et al, 2012), NS11201 (Rockman et al, 2020) and Cym04 (Gessner et al, 2012). The antagonists were charybdotoxin (ChTX) (Qiu et al, 2009), iberiotoxin (IbTX) (Yu et al, 2016), loperamide (LOP) (Vouga et al, 2019), paxilline (PAX) (Zhou et al, 2020), and TEA (Crouzy et al, 2001;Lenaeus et al, 2005). The endogenous modulators were Heme (Tang et al, 2003), protons (H + ) (Hou et al, 2009), lipids (Xia et al, 2004), carbon monoxide (CO) (Hou et al, 2008), kinases (Yan et al, 2008) and ethanol (EtOH) (Bukiya et al, 2014).…”

Section: Pharmacological and Intracellular Modulatorsmentioning

confidence: 99%

“…To determine if HP variants were located near sites of modulation, binding sites and residues involved in modulation sites were localized with respect to HP variants within the BK channel structure. The inhibitors included in this analysis were charybdotoxin (ChTX)(Qiu et al 2009), iberiotoxin (IbTX)(Yu et al 2016), loperamide (LOP)(Vouga et al 2019), paxilline (PAX)(Zhou et al 2020) and TEA(Crouzy et al 2001, Lenaeus et al 2005. The agonists were BC5 (Guohui Zhang1 et al 2022), NS1619(Gessner et al 2012), NS11201(Rockman et al 2020) and Cym04(Gessner et al 2012).…”

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confidence: 99%

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Structural mapping of patient-associatedKCNMA1gene variants

Moldenhauer,

Tammen,

Meredith

2023

Preprint

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KCNMA1 linked channelopathy is a neurological disorder produced by malfunctioning of the BK channel, characterized by seizure, motor abnormalities, and neurodevelopmental disability. Twenty-one KCNMA1 patient-associated variants have been classified as gain-of-function (GOF) or loss of function (LOF) in BK channel activity, and the remaining ~40% are variants of uncertain significance (VUS). To address the physical relationships, this study analyzed KCNMA1 missense variants within the context of BK channel cryoEM structures. Clusters of LOF variants were identified in the pore, within the AC region (RCK1), and near the Ca2+ bowl (RCK2), overlapping with sites of pharmacological or endogenous modulation. However, no clustering relationship was found for GOF variants. Next, variants were analyzed with widely used pathogenicity algorithms. The individual performances of REVEL, Mutpred, MetaLR, and CADD/PHRED were compared for each variant, incorporating them into a weighted summation model (WSM). The WSM component was integrated with BK channel structural parameters in a modular algorithm to generate a 'KCNMA1 meta score' (KMS). KMS performance showed a 7% difference from the highest performing individual algorithm (REVEL). Several functionally uncharacterized variants that showed different predictions between KMS and REVEL were assessed further using electrophysiological recordings of BK currents. Two KMS positive; REVEL negative variants were confirmed pathogenic (M578T and D965V), and one KMS negative; REVEL positive variant was confirmed non pathogenic (D800Y). However, KMS failed to accurately categorize two variants (E656A and K457E). Thus, although incorporation of structural data within the KMS algorithm results in a small performance improvement, its predictive capabilities will be increased as more disease delineated variants are functionally tested, new structural components are available, and novel functional modules are developed.

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Section: Methodsmentioning

confidence: 99%

Section: Pharmacological and Intracellular Modulatorsmentioning

confidence: 99%

Section: Pharmacological and Intracellular Modulatorsmentioning

confidence: 99%

mentioning

confidence: 99%

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Structural mapping of patient-associatedKCNMA1gene variants

Moldenhauer,

Tammen,

Meredith

2023

Preprint

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“…We initially observed, in a fluorescence-based cellular assay, that LOP is a potent inhibitor of BK channel–mediated thallium flux ( Vouga et al, 2019 ). Using patch-clamp electrophysiology, we now find that LOP leads to a reversible time- and dose-dependent inhibition of voltage-activated BK current over a wide range of cytosolic [Ca 2+ ], with a half-maximal inhibitory concentration (IC 50 ) of ~1 µM for open channels.…”

Section: Introductionmentioning

confidence: 99%

State-dependent inhibition of BK channels by the opioid agonist loperamide

Vouga

Rockman

Yan

et al. 2021

Journal of General Physiology

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Large-conductance Ca2+-activated K+ (BK) channels control a range of physiological functions, and their dysfunction is linked to human disease. We have found that the widely used drug loperamide (LOP) can inhibit activity of BK channels composed of either α-subunits (BKα channels) or α-subunits plus the auxiliary γ1-subunit (BKα/γ1 channels), and here we analyze the molecular mechanism of LOP action. LOP applied at the cytosolic side of the membrane rapidly and reversibly inhibited BK current, an effect that appeared as a decay in voltage-activated BK currents. The apparent affinity for LOP decreased with hyperpolarization in a manner consistent with LOP behaving as an inhibitor of open, activated channels. Increasing LOP concentration reduced the half-maximal activation voltage, consistent with relative stabilization of the LOP-inhibited open state. Single-channel recordings revealed that LOP did not reduce unitary BK channel current, but instead decreased BK channel open probability and mean open times. LOP elicited use-dependent inhibition, in which trains of brief depolarizing steps lead to accumulated reduction of BK current, whereas single brief depolarizing steps do not. The principal effects of LOP on BK channel gating are described by a mechanism in which LOP acts as a state-dependent pore blocker. Our results suggest that therapeutic doses of LOP may act in part by inhibiting K+ efflux through intestinal BK channels.

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