Antagonistic Effect of a Cytoplasmic Domain on the Basal Activity of Polymodal Potassium Channels

TREK/TRAAK channels are polymodal K+ channels that convert very diverse stimuli, including bioactive lipids, mechanical stretch and temperature, into electrical signals. The nature of the structural changes that regulate their activity remains an open question. Here, we show that a cytoplasmic domain (the proximal C-ter domain, pCt) exerts antagonistic effects in TREK1 and TRAAK. In basal conditions, pCt favors activity in TREK1 whereas it impairs TRAAK activity. Using the conformation-dependent binding of fluoxetine, we show that TREK1 and TRAAK conformations at rest are different, and under the influence of pCt. Finally, we show that depleting PIP2 in live cells has a more pronounced inhibitory effect on TREK1 than on TRAAK. This differential regulation of TREK1 and TRAAK is related to a previously unrecognized PIP2-binding site (R329, R330, and R331) present within TREK1 pCt, but not in TRAAK pCt. Collectively, these new data point out pCt as a major regulatory domain of these channels and suggest that the binding of PIP2 to the pCt of TREK1 results in the stabilization of the conductive conformation in basal conditions

Régulation fonctionnelle des canaux calcium sensibles au potentiel par la sous-unité auxiliaire b

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

The family of K 2P channels: salient structural and functional properties

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Reversibility of the Ca2+ Channel α1–β Subunit Interaction

International audienc

Antibodies against the beta subunit of voltage-dependent calcium channels in Lambert-Eaton myasthenic syndrome

International audienceLambert-Eaton myasthenic syndrome is an autoimmune disease that impairs neuromuscular transmission. Several studies suggest that neurotransmitter release is reduced by an immune response directed against the calcium channel complex of nerve terminals. The immunoglobulin G fractions from Lambert-Eaton myasthenic syndrome patients immunoprecipitate solubilized neuronal N-and P/Q-type channels and in certain cases brain, skeletal and cardiac muscle L-type channels [El Far O. et al.]. These channel immunoprecipitation assays are considered as useful for the diagnosis of this syndrome. In this study, we demonstrate that two predominant neuronal voltage-dependent calcium channel subunits (3 and 4 , of mol. wt 58,000) are general targets of Lambert-Eaton myasthenic syndrome autoantibodies. Of 20 disease sera tested, 55% were able to immunoprecipitate 35 S-labeled subunits. All five patients affected with small-cell lung carcinoma were positive for the-subunit immunoprecipitation assay. Interestingly, only a fraction of the-subunit-positive sera was also able to immunoprecipitate N-and P/Q-type channels, suggesting that several of the-subunit epitopes are masked in native channels. In accordance with this observation, we found that several-positive sera were able to prevent the interaction between calcium channel 1 and subunits in vitro. In cases where sera were able to immunoprecipitate subunits, N-and P/Q-type channels, the immunoprecipitation of both channel types was either partially or entirely mediated by-subunit antibodies. Our results suggest that assays based on the immunoprecipitation of subunits can be used as an additional test to assist in the diagnosis of Lambert-Eaton myasthenic syndrome. 1999 IBRO. Published by Elsevier Science Ltd

Silent but not dumb: how cellular trafficking and pore gating modulate expression of TWIK1 and THIK2

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Silencing of the Tandem Pore Domain Halothane-inhibited K + Channel 2 (THIK2) Relies on Combined Intracellular Retention and Low Intrinsic Activity at the Plasma Membrane

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Mechanistic basis of the dynamic response of TWIK1 ionic selectivity to pH

Abstract Highly selective for K+ at neutral pH, the TWIK1 channel becomes permeable to Na+ upon acidification. Using molecular dynamics simulations, we identify a network of residues involved in this unique property. Between the open and closed states previously observed by electron microscopy, molecular dynamics simulations show that the channel undergoes conformational changes between pH 7.5–6 involving residues His122, Glu235, Lys246 and Phe109. A complex network of interactions surrounding the selectivity filter at high pH transforms into a simple set of stronger interactions at low pH. In particular, His122 protonated by acidification moves away from Lys246 and engages in a salt bridge with Glu235. In addition, stacking interactions between Phe109 and His122, which stabilize the selectivity filter in its K+-selective state at high pH, disappear upon acidification. This leads to dissociation of the Phe109 aromatic side chain from this network, resulting in the Na+-permeable conformation of the channel

Sensing pressure in the cardiovascular system: Gq-coupled mechanoreceptors and TRP channels.

International audienceDespite the central physiological importance of cardiovascular mechanotransduction, the molecular identities of the sensors and the signaling pathways have long remained elusive. Indeed, how pressure is transduced into cellular excitation has only recently started to emerge. In both arterial and cardiac myocytes, the diacylglycerol-sensitive canonical transient receptor potential (TRPC) subunits are proposed to underlie the stretch-activated depolarizing cation channels. An indirect mechanism of activation through a ligand-independent conformational switch of Gq-coupled receptors by mechanical stress is invoked. Such a mechanism involving the angiotensin type 1 receptor and TRPC6 is proposed to trigger the arterial myogenic response to intraluminal pressure. TRPC6 is also involved in load-induced cardiac hypertrophy. In this review, we will focus on the molecular basis of pressure sensing in the cardiovascular system and associated disease states