Eric Honore - Academia.edu (original) (raw)

Papers by Eric Honore

An alternative to force

eLife, 2015

Researchers have discovered a synthetic small molecule that activates a mechanosensitive ion chan... more Researchers have discovered a synthetic small molecule that activates a mechanosensitive ion channel involved in a blood disorder.

An intracellular proton sensor commands lipid- and mechano-gating of the K(+) channel TREK-1

The EMBO journal, Jan 17, 2002

The 2P domain K(+) channel TREK-1 is widely expres sed in the nervous system. It is opened by a v... more The 2P domain K(+) channel TREK-1 is widely expres sed in the nervous system. It is opened by a variety of physical and chemical stimuli including membrane stretch, intracellular acidosis and polyunsaturated fatty acids. This activation can be reversed by PKA-mediated phosphorylation. The C-terminal domain of TREK-1 is critical for its polymodal function. We demonstrate that the conversion of a specific glutamate residue (E306) to an alanine in this region locks TREK-1 in the open configuration and abolishes the cAMP/PKA down-modulation. The E306A substitution mimics intracellular acidosis and rescues both lipid- and mechano-sensitivity of a loss-of-function truncated TREK-1 mutant. We conclude that protonation of E306 tunes the TREK-1 mechanical setpoint and thus sets lipid sensitivity.

Inhalational anesthetics activate two-pore-domain background K+ channels

Nature neuroscience, 1999

Volatile anesthetics produce safe, reversible unconsciousness, amnesia and analgesia via hyperpol... more Volatile anesthetics produce safe, reversible unconsciousness, amnesia and analgesia via hyperpolarization of mammalian neurons. In molluscan pacemaker neurons, they activate an inhibitory synaptic K+ current (IKAn), proposed to be important in general anesthesia. Here we show that TASK and TREK-1, two recently cloned mammalian two-P-domain K+ channels similar to IKAn in biophysical properties, are activated by volatile general anesthetics. Chloroform, diethyl ether, halothane and isoflurane activated TREK-1, whereas only halothane and isoflurane activated TASK. Carboxy (C)-terminal regions were critical for anesthetic activation in both channels. Thus both TREK-1 and TASK are possibly important target sites for these agents.

Leak or background K + selective channels -defined by a lack of voltage-and time-dependency, and ... more Leak or background K + selective channels -defined by a lack of voltage-and time-dependency, and with a linear current to voltage relationship in a symmetrical K + gradient -play an essential role in setting the resting membrane potential, tuning the action potential duration and modulating the responsiveness to synaptic inputs. Regulation of background K + channels by neurotransmitters and second messengers is central for synaptic function 1,2 . The most extensively studied native background K + channel is the S channel in the marine snail Aplysia sensory neurones 1 . Closing of the S-type background K + channel by 5-HT receptor activation is involved in presynaptic sensitization, a simple form of learning 2 . Additionally, neuronal background K + channels are the targets of an important class of pharmacological agents, the volatile general anaesthetics 3-7 .

AA arachidonic acid 4-AP 4 aminopyridine CPZ chlorpromazine DOHA docosahexaenoic acid ETYA eicosa... more AA arachidonic acid 4-AP 4 aminopyridine CPZ chlorpromazine DOHA docosahexaenoic acid ETYA eicosatetraynoic acid FA fatty acid LP lysophospholipids LPC lysophosphatidylcholine NMDA N-methyl D aspartate PAF platelet activating factor P domain pore domain PUFA polyunsaturated fatty acids S channel serotonin-sensitive K + channel TASK TWIK-related acid-sensitive K + channel TEA tetraethylammonium TMS transmembrane segments TNP trinitrophenol TRAAK TWIK-1 related arachidonic acid-stimulated K + channel TREK TWIK-1 related K + channel TWIK-1 tandem of P domains in a weak inward rectifying K + channel

mechano-gated K₂P channel TREK-1

Regulation of the Mechano‐Gated K2P Channel TREK‐1 by Membrane Phospholipids

Current Topics in Membranes, 2007

This chapter discusses the regulation of the mechano-gated K(2P) channel, TREK-1 by membrane phos... more This chapter discusses the regulation of the mechano-gated K(2P) channel, TREK-1 by membrane phospholipids. TREK-1 (KCNK2 or K2P2.1) is a polymodal K(+) channel that is activated by membrane stretch, intracellular acidosis, heat, and cellular lipids, such as arachidonic acid (AA). Phospholipids, including PIP2, exert a dual dose-dependent effect on TREK-1. Low concentrations transform the mechanogated K(+) channel TREK-1 into a leak K(+) channel. The phospholipid-sensing domain is a positively charged cluster in the proximal C-terminal domain. This region also encompasses the proton sensor E306 that is required for the activation of TREK-1 by cytosolic acidosis. Protonation of E306 increases channel-phospholipid interaction leading to TREK-1 opening without direct-mechanical stimulation. At higher concentrations, intracellular phospholipids inhibit channel activation by stretch, intracellular acidosis, and AA. Binding endogenous negative inner leaflet phospholipids with polylysine reduces the inhibition and reveals channel stimulation by exogenous intracellular phospholipids. Both stimulatory and inhibitory effects are observed with phosphatidylinositol (PI), phosphatidylethanolamine (PE), phosphatidylserine (PS), and phosphatidic acid (PA), but not diacylglycerol (DG), suggesting that the phosphate at position 3 is required, although the net charge is not critical. Membrane phospholipids, including PIP2, are major regulators of TREK-1 channel activity.

Cell Reports, 2012

How renal epithelial cells respond to increased pressure and the link with kidney disease states ... more How renal epithelial cells respond to increased pressure and the link with kidney disease states remain poorly understood. Pkd1 knockout or expression of a PC2 pathogenic mutant, mimicking the autosomal dominant polycystic kidney disease, dramatically enhances mechanical stress-induced tubular apoptotic cell death. We show the presence of a stretch-activated K + channel dependent on the TREK-2 K 2P subunit in proximal convoluted tubule epithelial cells. Our findings further demonstrate that polycystins protect renal epithelial cells against apoptosis in response to mechanical stress, and this function is mediated through the opening of stretch-activated K 2P channels. Thus, to our knowledge, we establish for the first time, both in vitro and in vivo, a functional relationship between mechanotransduction and mechanoprotection. We propose that this mechanism is at play in other important pathologies associated with apoptosis and in which pressure or flow stimulation is altered, including heart failure or atherosclerosis.

Trends in Neurosciences, 2007

Trends in Cardiovascular Medicine, 2006

A mammalian two pore domain mechano-gated S-like K+ channel

The EMBO Journal, 1998

Aplysia S-type K+ channels of sensory neurons play a dominant role in presynaptic facilitation an... more Aplysia S-type K+ channels of sensory neurons play a dominant role in presynaptic facilitation and behavioural sensitization. They are closed by serotonin via cAMP-dependent phosphorylation, whereas they are opened by arachidonic acid, volatile general anaesthetics and mechanical stimulation. We have identified a cloned mammalian two P domain K+ channel sharing the properties of the S channel. In addition, the recombinant channel is opened by lipid bilayer amphipathic crenators, while it is closed by cup-formers. The cytoplasmic C-terminus contains a charged region critical for chemical and mechanical activation, as well as a phosphorylation site required for cAMP inhibition.

The EMBO Journal, 2005

TREK-1 (KCNK2 or K 2P 2.1) is a mechanosensitive K 2P channel that is opened by membrane stretch ... more TREK-1 (KCNK2 or K 2P 2.1) is a mechanosensitive K 2P channel that is opened by membrane stretch as well as cell swelling. Here, we demonstrate that membrane phospholipids, including PIP 2 , control channel gating and transform TREK-1 into a leak K þ conductance. A carboxy-terminal positively charged cluster is the phospholipid-sensing domain that interacts with the plasma membrane. This region also encompasses the proton sensor E306 that is required for activation of TREK-1 by cytosolic acidosis. Protonation of E306 drastically tightens channel-phospholipid interaction and leads to TREK-1 opening at atmospheric pressure. The TREK-1-phospholipid interaction is critical for channel mechano-, pH i -and voltage-dependent gating.

Progress in Biophysics and Molecular Biology, 2008

Proceedings of the National Academy of Sciences, 2006

The neuronal mechano-gated K2P channels TREK-1 and TRAAK show pronounced desensitization within 1... more The neuronal mechano-gated K2P channels TREK-1 and TRAAK show pronounced desensitization within 100 ms of membrane stretch. Desensitization persists in the presence of cytoskeleton disrupting agents, upon patch excision, and when channels are expressed in membrane blebs. Mechanosensitive currents evoked with a variety of complex stimulus protocols were globally fit to a four-state cyclic kinetic model in detailed balance, without the need to introduce adaptation of the stimulus. However, we show that patch stress can be a complex function of time and stimulation history. The kinetic model couples desensitization to activation, so that gentle conditioning stimuli do not cause desensitization. Prestressing the channels with pressure, amphipaths, intracellular acidosis, or the E306A mutation reduces the peak-to-steady-state ratio by changing the preexponential terms of the rate constants, increasing the steady-state current amplitude. The mechanical responsivity can be accounted for by a change of in-plane area of Ϸ2 nm 2 between the closed and open conformations. Desensitization and its regulation by chemical messengers is predicted to condition the physiological role of K2P channels.

Susceptibility of cloned K+ channels to reactive oxygen species

Proceedings of the National Academy of Sciences, 1995

Free radical-induced oxidant stress has been implicated in a number of physiological and pathophy... more Free radical-induced oxidant stress has been implicated in a number of physiological and pathophysiological states including ischemia and reperfusion-induced dysrhythmia in the heart, apoptosis of T lymphocytes, phagocytosis, and neurodegeneration. We have studied the effects of oxidant stress on the native K+ channel from T lymphocytes and on K+ channels cloned from cardiac, brain, and T-lymphocyte cells and expressed in Xenopus oocytes. The activity of three Shaker K+ channels (Kv1.3, Kv1.4, and Kv1.5), one Shaw channel (Kv3.4), and one inward rectifier K+ channel (IRK3) was drastically inhibited by photoactivation of rose bengal, a classical generator of reactive oxygen species. Other channel types (such as Shaker K+ channel Kv1.2, Shab channels Kv2.1 and Kv2.2, Shal channel Kv4.1, inward rectifiers IRK1 and ROMK1, and hIsK) were completely resistant to this treatment. On the other hand tert-butyl hydroperoxide, another generator of reactive oxygen species, removed the fast inactivation processes of Kv1.4 and Kv3.4 but did not alter other channels. Xanthine/xanthine oxidase system had no effect on all channels studied. Thus, we show that different types of K+ channels are differently modified by reactive oxygen species, an observation that might be of importance in disease states.

Proceedings of the National Academy of Sciences, 1994

The present work shows that arachidonic acid and some other long chain polyunsaturated fatty acid... more The present work shows that arachidonic acid and some other long chain polyunsaturated fatty acids such as docosahexaenoic acid, which is abundant in fish oil, produce a direct open channel block of the major voltagedependent K+ channel (Kv1.5) cloned in cardiac cells. The inhibitory action of these selected fatty acids is seen when they are applied extracellularly but not when they are included in

Pflügers Archiv - European Journal of Physiology, 2010

Mechano-gated ion channels play a key physiological role in cardiac, arterial, and skeletal myocy... more Mechano-gated ion channels play a key physiological role in cardiac, arterial, and skeletal myocytes. For instance, opening of the non-selective stretch-activated cation channels in smooth muscle cells is involved in the pressure-dependent myogenic constriction of resistance arteries. These channels are also implicated in major pathologies, including cardiac hypertrophy or Duchenne muscular dystrophy. Seminal work in prokaryotes and invertebrates highlighted the role of transient receptor potential (TRP) channels in mechanosensory transduction. In mammals, recent findings have shown that the canonical TRPC1 and TRPC6 channels are key players in muscle mechanotransduction. In the present review, we will focus on the functional properties of TRPC1 and TRPC6 channels, on their mechano-gating, regulation by interacting cytoskeletal and scaffolding proteins, physiological role and implication in associated diseases.

Pflügers Archiv - European Journal of Physiology, 2007

TREK-1 is an unconventional K + channel that is activated by both physical and chemical stimuli. ... more TREK-1 is an unconventional K + channel that is activated by both physical and chemical stimuli. In this study, we show that the inner leaflet membrane phospholipids, including PIP 2 , exert a mixed stimulatory and inhibitory effect on TREK-1. Intra-cellular phospholipids inhibit basal channel activity and activation by membrane stretch, intracellular acidosis and arachidonic acid. However, binding of endogenous negative inner leaflet phospholipids with polylysine reduces inhibition and reveals channel stimulation by exogenous intra-cellular phospholipids. A similar effect is observed with PI, PE, PS and PA, unlike DG, demonstrating that the phosphate at position 3 is required although the global charge of the molecule is not critical. Inhibition depends on the distal C-terminal domain that conditions channel mechano-sensitivity, but is independent of the positively charged PIP 2 stimulatory site in the proximal Cterminal domain. This is, to our knowledge, the first report of an ion channel dually regulated by membrane phospholipids.

Pflügers Archiv - European Journal of Physiology, 2008

Mechano-gated ion channels are implicated in a variety of key physiological functions ranging fro... more Mechano-gated ion channels are implicated in a variety of key physiological functions ranging from touch sensitivity to arterial pressure regulation. Seminal work in prokaryotes and invertebrates provided strong evidence for the role of specific ion channels in volume regulation, touch sensitivity, or hearing, specifically the mechanosensitive channel subunits of large and small conductances (MscL and MscS), the mechanosensory channel subunits (MEC) and the transient receptor potential channel subunits (TRP). In mammals, recent studies further indicate that members of the TRP channel family may also be considered as possible candidate mechanosensors responding to either tension, flow, or changes in cell volume. However, contradictory results have challenged whether these TRP channels, including TRPC1 and TRPC6, are directly activated by mechanical stimulation. In the present review, we will focus on the mechanosensory function of TRP channels, discuss whether a direct or indirect mechanism is at play, and focus on the proposed role for these channels in the arterial myogenic response to changes in intraluminal pressure.