G protein modulation of K2P potassium channel TASK-2
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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.
KeywordsTASK-2 G protein Background conductance Patch-clamp Cell volume regulation
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.
- 7.Cid LP, Niemeyer MI, Ramírez A, Sepúlveda FV (2000) Splice variants of a ClC-2 chloride channel with differing functional characteristics. Am J Physiol 279:C1198–C1210Google Scholar
- 8.Cid LP, Roa-Rojas HA, Niemeyer MI, González W, Araki M, Araki K, Sepúlveda FV (2013) TASK-2: a K2P K+ channel with complex regulation and diverse physiological functions. Front Physiol (submitted):Google Scholar
- 15.Doroshenko P (1991) Second messengers mediating activation of chloride current by intracellular GTP gamma S in bovine chromaffin cells. J Physiol (London) 436:725–738Google Scholar
- 18.Estévez AY, Bond T, Strange K (2001) Regulation of ICl, swell in neuroblastoma cells by G protein signaling pathway. Am J Physiol 281:C89–C98Google Scholar
- 19.Flores CA, Cid LP, Niemeyer MI, Sepúlveda FV (2011) B lymphocytes taken to task: a role for a background conductance K2P K+ channel in B cells. Focus on "Expression of TASK-2 and its upregulation by B cell receptor stimulation in WEHI-231 mouse immature B cells". Am J Physiol Cell Physiol 300:C976–C978PubMedCrossRefGoogle Scholar
- 20.Gestreau C, Heitzmann D, Thomas J, Dubreuil V, Bandulik S, Reichold M, Bendahhou S, Pierson P, Sterner C, Peyronnet-Roux J, Benfriha C, Tegtmeier I, Ehnes H, Georgieff M, Lesage F, Brunet JF, Goridis C, Warth R, Barhanin J (2010) Task2 potassium channels set central respiratory CO2 and O2 sensitivity. Proc Natl Acad Sci U S A 107:2325–2330PubMedCrossRefGoogle Scholar
- 22.Hara-Chikuma M, Verkman AS (2006) Aquaporin-1 facilitates epithelial cell migration in kidney proximal tubule. J Am Soc Nephrol 17:39–45Google Scholar
- 59.Warth R, Barrière H, Meneton P, Bloch M, Thomas J, Tauc M, Heitzmann D, Romeo E, Verrey F, Mengual R, Guy N, Bendahhou S, Lesage F, Poujeol P, Barhanin J (2004) Proximal renal tubular acidosis in TASK2 K+ channel-deficient mice reveals a mechanism for stabilizing bicarbonate transport. Proc Natl Acad Sci U S A 101:8215–8220PubMedCrossRefGoogle Scholar