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G protein modulation of K2P potassium channel TASK-2

A role of basic residues in the C terminus domain

  • Ion channels, receptors and transporters
  • Published:
Pflügers Archiv - European Journal of Physiology Aims and scope Submit manuscript

Abstract

TASK-2 (K2P5.1) is a background K+ channel opened by extra- or intracellular alkalinisation that plays a role in renal bicarbonate handling, central chemoreception and cell volume regulation. Here, we present results that suggest that TASK-2 is also modulated by Gβγ subunits of heterotrimeric G protein. TASK-2 was strongly inhibited when GTP-γ-S was used as a replacement for intracellular GTP. No inhibition was present using GDP-β-S instead. Purified Gβγ introduced intracellularly also inhibited TASK-2 independently of whether GTP or GDP-β-S was present. The effects of GTP-γ-S and Gβγ subunits were abolished by neutralisation of TASK-2 C terminus double lysine residues K257–K258 or K296–K297. Use of membrane yeast two hybrid (MYTH) experiments and immunoprecipitation assays using tagged proteins gave evidence for a physical interaction between Gβ1 and Gβ2 subunits and TASK-2, in agreement with expression of these subunits in proximal tubule cells. Co-immunoprecipitation was impeded by mutating C terminus K257–K258 (but not K296–K297) to alanines. Gating by extra- or intracellular pH was unaltered in GTP-γ-S-insensitive TASK-2-K257A-K258A mutant. Shrinking TASK-2-expressing cells in hypertonic solution decreased the current to 36 % of its initial value. The same manoeuvre had a significantly diminished effect on TASK-2-K257A-K258A- or TASK-2-K296-K297-expressing cells, or in cells containing intracellular GDP-β-S. Our data are compatible with the concept that TASK-2 channels are modulated by Gβγ subunits of heterotrimeric G protein. We propose that this modulation is a novel way in which TASK-2 can be tuned to its physiological functions.

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Notes

  1. There is a discrepancy between single channel conductance for I K, vol estimated from noise analysis of macroscopic current in Ehrlich cells giving a value of 5.5 pS [46], which compares with 15 pS for TASK-2 by direct single channel current measurement [49], both at 0 mV and under quasi-physiological K+ gradient. The only difference was the lower K+ intracellular concentration used in Ehrlich cells (116 mM) compared with the expressed channel (150 mM). The difference might point to different channels, but a decision on this will have to await single channel measurements in Ehrlich cells.

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Acknowledgements

We are grateful to Drs. Jürgen Daut (Marburg), Stéphane A. Laporte (Montréal) and Carlos B. González (Valdivia) for cDNAs for TASK-3, and AT1 and V1a receptors. Mauricio Bórquez is acknowledged for his help with some of the experiments. Financial support was obtained from Fondecyt grants 1090478 and 3085021. The Centro de Estudios Científicos (CECS) is funded by the Chilean Government through the Centres of Excellence Base Financing Program of Conicyt.

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  1. Carolina Añazco

    Present address: Nephrology & Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA

  2. Gaspar Peña-Münzenmayer

    Present address: National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20892, USA

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  1. Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile

    Carolina Añazco, Gaspar Peña-Münzenmayer, Carla Araya, L. Pablo Cid, Francisco V. Sepúlveda & María Isabel Niemeyer

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C. Añazco and G. Peña-Münzenmayer should be considered joint first authors.

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Añazco, C., Peña-Münzenmayer, G., Araya, C. et al. G protein modulation of K2P potassium channel TASK-2. Pflugers Arch - Eur J Physiol 465, 1715–1726 (2013). https://doi.org/10.1007/s00424-013-1314-0

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