Properties of single two‐pore domain TREK‐2 channels expressed in mammalian cells

Kang, Dawon; Choe, Changyong; Cavanaugh, Eric J.; Kim, Dong‐Hee

doi:10.1113/jphysiol.2007.136150

Cited by 33 publications

(34 citation statements)

References 32 publications

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“…The single-channel conductance of TREK-2 reportedly varies depending on the length of the N terminus, with shorter splice variants and truncations stabilizing a larger, ∼250 pS conductance with similar rectification (50,51). Therefore, given the truncated N terminus of the purified protein used in these studies, the single-channel conductances that we found here (in 200 mM KCl) are entirely consistent with those expected for TREK-2.…”

Section: Resultssupporting

confidence: 82%

Asymmetric mechanosensitivity in a eukaryotic ion channel

Clausen

Jarerattanachat

Carpenter

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Living organisms perceive and respond to a diverse range of mechanical stimuli. A variety of mechanosensitive ion channels have evolved to facilitate these responses, but the molecular mechanisms underlying their exquisite sensitivity to different forces within the membrane remains unclear. TREK-2 is a mammalian twopore domain (K2P) K + channel important for mechanosensation, and recent studies have shown how increased membrane tension favors a more expanded conformation of the channel within the membrane. These channels respond to a complex range of mechanical stimuli, however, and it is uncertain how differences in tension between the inner and outer leaflets of the membrane contribute to this process. To examine this, we have combined computational approaches with functional studies of oppositely oriented single channels within the same lipid bilayer. Our results reveal how the asymmetric structure of TREK-2 allows it to distinguish a broad profile of forces within the membrane, and illustrate the mechanisms that eukaryotic mechanosensitive ion channels may use to detect and fine-tune their responses to different mechanical stimuli.any forms of sensory perception in higher organisms depend on the rapid conversion of mechanical and physical stimuli into the electrochemical language of nerve and muscle cells (1). These transduction mechanisms often involve "mechanosensitive" (MS) ion channels that are able to rapidly convert physicomechanical stimuli into the electrical signals required for complex physiological responses (e.g., touch, pain, hearing, proprioception), as well those mechanical signals that play key roles in development and cell-cell communication (2). The enormous complexity and diversity of these sensory responses suggests that a variety of molecular mechanisms are likely responsible; for example, while some channels are regulated via physical coupling to proteins of the cytoskeleton and/or cell matrix, others respond directly to changes in lipid membrane tension (3). The precise structural and physical mechanisms underlying these processes remain poorly understood, however (4-6).Our current understanding of how membrane tension directly regulates ion channel gating is largely derived from studies of prokaryotic MS ion channels involved in the control of bacterial turgor pressure (7,8). The open state of these MS channels has a larger cross-sectional area than the closed state within the membrane, and stretch-induced changes in the forces within the bilayer stabilize the expanded open-state conformation. This is commonly referred to as the force-from-lipid principle of mechanosensitivity (9). Similar physical principles are thought to regulate many eukaryotic MS channels (5, 10).Typically, the functional activity of MS ion channels is examined in pipette-based patch-clamp recordings in which negative or positive pressures are used to alter bilayer tension. These pressure changes stretch the membrane to alter the lateral pressure profile, the complex profile of forces that vary with location acro...

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Section: Resultssupporting

confidence: 82%

Asymmetric mechanosensitivity in a eukaryotic ion channel

Clausen

Jarerattanachat

Carpenter

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…TREK-2 is the closest homolog of TREK-1, sharing more than 60 % amino acid identity, and is regulated in an identical manner in response to intracellular acidic pH i , polyunsaturated fatty acids, membrane stretch, and temperature [1,8,14,18,22,28]. In contrast to our previous reports, other groups reported that TREK-1 is activated by PI(4,5)P 2 .…”

Section: Introductioncontrasting

confidence: 72%

Inhibition of TREK-2 K+ channels by PI(4,5)P2: an intrinsic mode of regulation by intracellular ATP via phosphatidylinositol kinase

Woo

Shin

Kim

et al. 2016

Pflugers Arch - Eur J Physiol

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TWIK-related two-pore domain K(+) channels 1 and 2 (TREKs) are activated under various physicochemical conditions. However, the directions in which they are regulated by PI(4,5)P2 and intracellular ATP are not clearly presented yet. In this study, we investigated the effects of ATP and PI(4,5)P2 on overexpressed TREKs (HEK293T and COS-7) and endogenously expressed TREK-2 (mouse astrocytes and WEHI-231 B cells). In all of these cells, both TREK-1 and TREK-2 currents were spontaneously increased by dialysis with ATP-free pipette solution for whole-cell recording (ITREK-1,w-c and ITREK-2w-c) or by membrane excision for inside-out patch clamping without ATP (ITREK-1,i-o and ITREK-2,i-o). Steady state ITREK-2,i-o was reversibly decreased by 3 mM ATP applied to the cytoplasmic side, and this reduction was prevented by wortmannin, a PI-kinase inhibitor. An exogenous application of PI(4,5)P2 inhibited the spontaneously increased ITREKs,i-o, suggesting that intrinsic PI(4,5)P2 maintained by intracellular ATP and PI kinase may set the basal activity of TREKs in the intact cells. The inhibition of intrinsic TREK-2 by ATP was more prominent in WEHI-231 cells than astrocytes. Interestingly, unspecific screening of negative charges by poly-L-lysine also inhibited ITREK-2,i-o. Application of PI(4,5)P2 after the poly-L-lysine treatment showed dose-dependent dual effects, initial activation and subsequent inhibition of ITREK-2,i-o at low and high concentrations, respectively. In HEK293T cells coexpressing TREK-2 and a voltage-sensitive PI(4,5)P2 phosphatase, sustained depolarization increased ITREK-2,w-c initially (<5 s) but then decreased the current below the control level. In HEK293T cells coexpressing TREK-2 and type 3 muscarinic receptor, application of carbachol induced transient activation and sustained suppression of ITREK-2,w-c and cell-attached ITREK-2. The inhibition of TREK-2 by unspecific electrostatic quenching, extensive dephosphorylation, or sustained hydrolysis of PI(4,5)P2 suggests the existence of dual regulatory modes that depend on PI(4,5)P2 concentration.

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“…32, 33 Quantitative studies revealed that the TRESK K + channel is most abundant in the DRG. 32 DRG neurons of TRESK functional knockout mice showed augmented excitability, suggesting that the TRESK K + channel plays an important role in regulating resting membrane potential and excitability of DRG neurons.…”

Section: Discussionmentioning

confidence: 99%

RETRACTED: Increased Activation of the TRESK K+ Mediates Vago-Vagal Reflex Malfunction in Diabetic Rats

et al. 2016

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BACKGROUND & AIMS Patients with diabetes have defects in the vagal afferent pathway that result in abnormal gastrointestinal function. We investigated whether selective increased activation of the 2 pore domain potassium channel TRESK contributes to nodose ganglia (NG) malfunction, disrupting gastrointestinal function in diabetic rats. METHODS We conducted whole-cell current-clamp and single-unit recordings in NG neurons from diabetes-prone BioBreeding/Worcester rats and streptozotocin-induced diabetic (STZ-D) rats and compared with control rats. NG neurons in rats or cultured NG neurons were exposed to pharmacologic antagonists and/or transfected with small hairpin or small interfering RNAs that reduced expression of TRESK. We then made electrophysiologic recordings and studied gastrointestinal functions. RESULTS We observed reduced input resistance, hyperpolarized membrane potential, and increased current threshold to elicit action potentiation in NG neurons of STZ-D rats compared to controls. NG neuron excitability was similarly altered in diabetes-prone rats. In vivo single-unit NG neuronal discharges in response to 30 and 60 pmol cholecystokinin octapeptide were significantly lower in STZ-D rats compared to controls. Reducing expression of the TRESK K+ channel restored NG excitability in vitro and in vivo, as well as CCK8-stimulated secretion of pancreatic enzymes and secretin-induced gastrointestinal motility, which are mediated by vagovagal reflexes. These abnormalities resulted from increased intracellular Ca2+ in the NG, activating calcineurin, which, in turn, bound to an NFAT-like docking site on the TRESK protein, resulting in neuronal membrane hyperpolarization. Conclusions In 2 rate models of diabetes, we found that activation of the TRESK K+ channel reduced NG excitability and disrupted gastrointestinal functions.

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Properties of single two‐pore domain TREK‐2 channels expressed in mammalian cells

Cited by 33 publications

References 32 publications

Asymmetric mechanosensitivity in a eukaryotic ion channel

Asymmetric mechanosensitivity in a eukaryotic ion channel

Inhibition of TREK-2 K+ channels by PI(4,5)P2: an intrinsic mode of regulation by intracellular ATP via phosphatidylinositol kinase

RETRACTED: Increased Activation of the TRESK K+ Mediates Vago-Vagal Reflex Malfunction in Diabetic Rats

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