Differential phospholipase C‐dependent modulation of TASK and TREK two‐pore domain K+ channels in rat thalamocortical relay neurons. (3rd November 2014)

• Record Type: Journal Article
• Authors: Bista, Pawan; Pawlowski, Matthias; Cerina, Manuela; Ehling, Petra; Leist, Michael; Meuth, Patrick; Aissaoui, Ania; Borsotto, Marc; Heurteaux, Catherine; Decher, Niels; Pape, Hans‐Christian; Oliver, Dominik; Meuth, Sven G.; Budde, Thomas
• Is Part Of: Journal of physiology. Volume 593:Number 1(2015:Jan.)
• Page Start: 127
• Page End: 144
• Publication Date: 2014-11-03
• Subjects: Physiology -- Periodicals; 612.005
• DOI: 10.1113/jphysiol.2014.276527
• Languages: English
• ISSNs: 0022-3751

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="tjp6386-sec-0010" sec-type="section"> <title>Key points</title> <p> <list id="tjp6386-list-0001" list-type="bullet"> <list-item> <p>During the behavioural states of sleep and wakefulness thalamocortical relay neurons fire action potentials in high frequency bursts or tonic sequences, respectively.</p> </list-item> <list-item> <p>The modulation of specific K<sup>+</sup> channel types, termed TASK and TREK, allows these neurons to switch between the two modes of activity.</p> </list-item> <list-item> <p>In this study we show that the signalling lipids phosphatidylinositol 4, 5‐bisphosphate (PIP<sub>2</sub>) and diacylglycerol (DAG), which are components of their membrane environment, switch on and shut off TREK and TASK channels, respectively.</p> </list-item> <list-item> <p>These channel modulations contribute to a better understanding of the molecular basis of the effects of neurotransmitters such as ACh which are released by the brainstem arousal system.</p> </list-item> <list-item> <p>The present report introduces PIP<sub>2</sub> and DAG as new elements of signal transduction in the thalamus.</p> </list-item> </list> </p> </sec> <sec id="tjp6386-sec-0020" sec-type="section"> <title>Abstract</title> <p>The activity of two‐pore domain potassium channels (K<sub>2P</sub>) regulates the excitability and firing modes of thalamocortical (TC) neurons. In particular, the inhibition of two‐pore domain weakly inwardly rectifying K<sup>+</sup> channel (TWIK)‐related acid‐sensitive K<sup>+</sup> (TASK) channels and TWIK‐related K<sup>+</sup> (TREK) channels, as a consequence of the stimulation of muscarinic ACh receptors (MAChRs) which are coupled to phosphoinositide‐specific phospholipase C (PLCβ), induces a shift from burst to tonic firing. By using a whole cell patch‐clamp approach, the contribution of the membrane‐bound second messenger molecules phosphatidylinositol 4, 5‐bisphosphate (PIP<sub>2</sub>) and diacylglycerol (DAG) acting downstream of PLCβ was probed. The standing outward current (<italic>I</italic><sub>SO</sub>) was used to monitor the current through TASK and TREK channels in TC neurons. By exploiting different manoeuvres to change the intracellular PIP<sub>2</sub> level in TC neurons, we here show that the scavenging of PIP<sub>2</sub> (by neomycin) results in an increased muscarinic effect on <italic>I</italic><sub>SO</sub> whereas increased availability of PIP<sub>2</sub> (inclusion to the patch pipette; histone‐based carrier) decreased muscarinic signalling. The degree of muscarinic inhibition specifically depends on phosphatidylinositol phosphate (PIP) and PIP<sub>2</sub> but no other phospholipids (phosphatidic acid, phosphatidylserine). The use of specific blockers revealed that PIP<sub>2</sub> is targeting TREK but not TASK channels. Furthermore, we demonstrate that the inhibition of TASK channels is induced by the application of the DAG analogue 1‐oleoyl‐2‐acetyl‐<italic>sn</italic>‐glycerol (OAG). Under current clamp conditions the activation of MAChRs and PLCβ as well as the application of OAG resulted in membrane depolarization, while PIP<sub>2</sub> application via histone carrier induced a hyperpolarization. These results demonstrate a differential role of PIP<sub>2</sub> and DAG in K<sub>2P</sub> channel modulation in native neurons which allows a fine‐tuned inhibition of TREK (via PIP<sub>2</sub> depletion) and TASK (via DAG) channels following MAChR stimulation.</p> </sec> </abstract>