ML335 inhibits TWIK2 channel-mediated potassium efflux and attenuates mitochondrial damage in MSU crystal-induced inflammation.

BACKGROUND: Activation of the NLRP3 inflammasome is critical in the inflammatory response to gout. Potassium ion (K+) efflux mediated by the TWIK2 channel is an important upstream mechanism for NLRP3 inflammasome activation. Therefore, the TWIK2 channel may be a promising therapeutic target for MSU crystal-induced inflammation. In the present study, we investigated the effect of ML335, a known K2P channel modulator, on MSU crystal-induced inflammatory responses and its underlying molecular mechanisms. METHODS: By molecular docking, we calculated the binding energies and inhibition constants of five K2P channel modulators (Hydroxychloroquine, Fluoxetine, DCPIB, ML365 and ML335) with TWIK2. Intracellular potassium ion concentration and mitochondrial function were assessed by flow cytometry. The interaction between MARCH5 and SIRT3 was demonstrated by immunoprecipitation and Western blotting assay. MSU suspensions were injected into mouse paw and peritoneal cavity to induce acute gout model. RESULTS: ML335 has the highest binding energy and the lowest inhibition constant with TWIK2 in the five calculated K2P channel modulators. In comparison, among these five compounds, ML335 efficiently inhibited the release of IL-1ß from MSU crystal-treated BMDMs. ML335 decreased MSU crystal-induced K+ efflux mainly dependent on TWIK2 channel. More importantly, ML335 can effectively inhibit the expression of the mitochondrial E3 ubiquitin ligase MARCH5 induced by MSU crystals, and MARCH5 can interact with the SIRT3 protein. ML335 blocked MSU crystal-induced ubiquitination of SIRT3 protein by MARCH5. In addition, ML335 improved mitochondrial dynamics homeostasis and mitochondrial function by inhibiting MARCH5 protein expression. ML335 attenuated the inflammatory response induced by MSU crystals in vivo and in vitro. CONCLUSION: Inhibition of TWIK2-mediated K+ efflux by ML335 alleviated mitochondrial injury via suppressing March5 expression, suggesting that ML335 may be an effective candidate for the future treatment of gout.

Development of covalent chemogenetic K2P channel activators.

K2P potassium channels regulate excitability by affecting cellular resting membrane potential in the brain, cardiovascular system, immune cells, and sensory organs. Despite their important roles in anesthesia, arrhythmia, pain, hypertension, sleep, and migraine, the ability to control K2P function remains limited. Here, we describe a chemogenetic strategy termed CATKLAMP (covalent activation of TREK family K+ channels to clamp membrane potential) that leverages the discovery of a K2P modulator pocket site that reacts with electrophile-bearing derivatives of a TREK subfamily small-molecule activator, ML335, to activate the channel irreversibly. We show that CATKLAMP can be used to probe fundamental aspects of K2P function, as a switch to silence neuronal firing, and is applicable to all TREK subfamily members. Together, our findings exemplify a means to alter K2P channel activity that should facilitate molecular and systems level studies of K2P function and enable the search for new K2P modulators.

The TREK-1 potassium channel is a potential pharmacological target for vasorelaxation in pulmonary hypertension.

BACKGROUND AND PURPOSE: Pulmonary arterial hypertension (PAH) is a progressive disease in which chronic membrane potential (Em) depolarisation of the pulmonary arterial smooth muscle cells (PASMCs) causes calcium overload, a key pathological alteration. Under resting conditions, the negative Em is mainly set by two pore domain potassium (K2P) channels, of which the TASK-1 has been extensively investigated. EXPERIMENTAL APPROACH: Ion channel currents and membrane potential of primary cultured human(h) PASMCs were measured using the voltage- and current clamp methods. Intracellular [Ca2+] was monitored using fluorescent microscopy. Pulmonary BP and vascular tone measurements were also performed ex vivo using a rat PAH model. KEY RESULTS: TREK-1 was the most abundantly expressed K2P in hPASMCs of healthy donors and idiopathic(I) PAH patients. Background K+-current was similar in hPASMCs for both groups and significantly enhanced by the TREK activator ML-335. In donor hPASMCs, siRNA silencing or pharmacological inhibition of TREK-1 caused depolarisation, reminiscent of the electrophysiological phenotype of idiopathic PAH. ML-335 hyperpolarised donor hPASMCs and normalised the Em of IPAH hPASMCs. A close link was found between TREK-1 activity and intracellular Ca2+-signalling using a channel activator, ML-335, and an inhibitor, spadin. In the rat, ML-335 relaxed isolated pre-constricted pulmonary arteries and significantly decreased pulmonary arterial pressure in the isolated perfused lung. CONCLUSIONS AND IMPLICATIONS: These data suggest that TREK-1is a key factor in Em setting and Ca2+ homeostasis of hPASMC, and therefore, essential for maintenance of a low resting pulmonary vascular tone. Thus TREK-1 may represent a new therapeutic target for PAH.

The Polysite Pharmacology of TREK K2P Channels.

K2P (KCNK) potassium channels form "background" or "leak" currents that have critical roles in cell excitability control in the brain, cardiovascular system, and somatosensory neurons. Similar to many ion channel families, studies of K2Ps have been limited by poor pharmacology. Of six K2P subfamilies, the thermo- and mechanosensitive TREK subfamily comprising K2P2.1 (TREK-1), K2P4.1 (TRAAK), and K2P10.1 (TREK-2) are the first to have structures determined for each subfamily member. These structural studies have revealed key architectural features that underlie K2P function and have uncovered sites residing at every level of the channel structure with respect to the membrane where small molecules or lipids can control channel function. This polysite pharmacology within a relatively small (~70 kDa) ion channel comprises four structurally defined modulator binding sites that occur above (Keystone inhibitor site), at the level of (K2P modulator pocket), and below (Fenestration and Modulatory lipid sites) the C-type selectivity filter gate that is at the heart of K2P function. Uncovering this rich structural landscape provides the framework for understanding and developing subtype-selective modulators to probe K2P function that may provide leads for drugs for anesthesia, pain, arrhythmia, ischemia, and migraine.