Effect of phospholipid surface charge on the conductance and gating of a Ca2+-activated K+ channel in planar lipid bilayers

Moczydlowski, Edward; Álvarez, Osvaldo; Vergara, Cecilia; Latorre, Ramón

doi:10.1007/bf01868701

Cited by 146 publications

(124 citation statements)

References 33 publications

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“…Gating of voltage-gated ion channels is known to be affected by local electrostatic environments based on the concentrations of ions, phospholipids, and sugars surrounding the voltage sensor (27)(28)(29)(30). Phosphoinositides have negative charges on phosphate groups.…”

Section: Discussionmentioning

confidence: 99%

Enzyme Domain Affects the Movement of the Voltage Sensor in Ascidian and Zebrafish Voltage-sensing Phosphatases

Hossain

Iwasaki

Okochi

et al. 2008

Journal of Biological Chemistry

113

166

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The ascidian voltage-sensing phosphatase (Ci-VSP) consists of the voltage sensor domain (VSD) and a cytoplasmic phosphatase region that has significant homology to the phosphatase and tensin homolog deleted on chromosome TEN (PTEN).The phosphatase activity of Ci-VSP is modified by the conformational change of the VSD. In many proteins, two protein modules are bidirectionally coupled, but it is unknown whether the phosphatase domain could affect the movement of the VSD in VSP. We addressed this issue by whole-cell patch recording of gating currents from a teleost VSP (Dr-VSP) cloned from Danio rerio expressed in tsA201 cells. Replacement of a critical cysteine residue, in the phosphatase active center of Dr-VSP, by serine sharpened both ON-and OFF-gating currents. Similar changes were produced by treatment with phosphatase inhibitors, pervanadate and orthovanadate, that constitutively bind to cysteine in the active catalytic center of phosphatases. The distinct kinetics of gating currents dependent on enzyme activity were not because of altered phosphatidylinositol 4,5-bisphosphate levels, because the kinetics of gating current did not change by depletion of phosphatidylinositol 4,5-bisphosphate, as reported by coexpressed KCNQ2/3 channels. These results indicate that the movement of the VSD is influenced by the enzymatic state of the cytoplasmic domain, providing an important clue for understanding mechanisms of coupling between the VSD and its effector.Voltage-gated ion channels play an important role in electrical activities and cell signaling of muscles and nerves. The first four transmembrane regions (S1-S4) are conserved among all the voltage-gated channels and operate as the voltage sensor, thus called the voltage sensor domain (VSD) 4 (1). The VSD regulates the operation of the downstream pore domain, consisting of the two transmembrane segments (S5-S6) and a loop that provides an ion permeation pathway. The VSD has several positively charged residues interspersed with two hydrophobic residues in the fourth transmembrane segment, called S4, that plays critical roles in voltage sensing (1-4). Recently resolution of the crystal structure of voltage-gated potassium channels (5, 6) and biophysical measurements of the movement of specific sites of the VSD (3) have led to proposed models for the operation of the VSD (7). However, the VSD has long been studied as a structure unique to voltage-gated ion channels.We have recently identified a protein, Ci-VSP, that contains the VSD but not the pore domain (8). Ci-VSP has the following two modules in its structure: the transmembrane spanning region that corresponds to the VSD of voltage-gated ion channels and the cytoplasmic region with homology to the phosphatase and tensin homolog deleted on chromosome TEN (PTEN), a PtdIns(3,4,5)P 3 phosphatase (9). The VSD of Ci-VSP exhibits gating currents that indicate the conformational change in response to membrane voltage, and the phosphoinositide phosphatase activity is voltage-dependently regulated (8). This is the first ...

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Section: Discussionmentioning

confidence: 99%

Enzyme Domain Affects the Movement of the Voltage Sensor in Ascidian and Zebrafish Voltage-sensing Phosphatases

Hossain

Iwasaki

Okochi

et al. 2008

Journal of Biological Chemistry

113

166

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“…Local electrostatic effects have now been documented in several different channels reconstituted into planar bilayers (Bell and Miller, 1984;Moczydlowski et al, 1985;Affolter and Coronado, 1986). Recently, Green and co-workers (1987) reported similar experiments on Na + channels and demonstrated the existence of a region of high negative charge near the binding site for tetrodotoxin.…”

Section: Discussionmentioning

confidence: 99%

Charybdotoxin block of single Ca2+-activated K+ channels. Effects of channel gating, voltage, and ionic strength.

Anderson

MacKinnon

Smith

et al. 1988

The Journal of General Physiology

247

155

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Charybdotoxin (CTX), a small, basic protein from scorpion venom, strongly inhibits the conduction of K ions through high-conductance, Ca2+-activated K + channels. The interaction of CTX with Ca2+-activated K + channels from rat skeletal muscle plasma membranes was studied by inserting single channels into uncharged planar phospholipid bilayers. CTX blocks K § conduction by binding to the external side of the channel, with an apparent dissociation constant of ---10 nM at physiological ionic strength. The dwelltime distributions of both blocked and unblocked states are single-exponential. The toxin association rate varies linearly with the CTX concentration, and the dissociation rate is independent of it. CTX is competent to block both open and closed channels; the association rate is sevenfold faster for the open channel, while the dissociation rate is the same for both channel conformations. Membrane depolarization enhances the CTX dissociation rate e-fold/28 mV; if the channel's open probability is maintained constant as voltage varies, then the toxin association rate is voltage independent. Increasing the external solution ionic strength from 20 to 300 mM (with K § Na +, or arginine +) reduces the association rate by two orders of magnitude, with little effect on the dissociation rate. We conclude that CTX binding to the Ca2+-activated K § channel is a bimolecular process, and that the CTX interaction senses both voltage and the channel's conformational state. We further propose that a region of fixed negative charge exists near the channel's CTX-binding site. INTRODUGTIONThe high-conductance, Ca~+-activated K + channel is present in the plasma membranes of many types of cells, both excitable and inexcitable (Latorre, 1086). Its

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“…The plasma membrane is a highly heterogeneous environment in which lipid domains exist that can serve important roles in cell function (Welti and Glaser, 1994;Bevers et al, 1999; London, 2002). Thus, modification of the lipid environment can alter BK channel activity (Moczydlowski et al, 1985;Clarke et al, 2002) as well as the sensitivity of this channel to EtOH (Crowley et al, 2003). However, although it is known that lipid composition varies from region to region in the brain (Chavko et al, 1993), variability between dendrites and soma within the same neuron has not been reported to our knowledge.…”

Section: Etoh Effects On Bk Channels and Its Compartmentalizationmentioning

confidence: 94%

Somatic Localization of a Specific Large-Conductance Calcium-Activated Potassium Channel Subtype Controls Compartmentalized Ethanol Sensitivity in the Nucleus Accumbens

Martin¹,

Puig²,

Pietrzykowski³

et al. 2004

J. Neurosci.

121

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Alcohol is an addictive drug that targets a variety of ion channels and receptors. To address whether the effects of alcohol are compartment specific (soma vs dendrite), we examined the effects of ethanol (EtOH) on large-conductance calcium-activated potassium channels (BK) in cell bodies and dendrites of freshly isolated neurons from the rat nucleus accumbens (NAcc), a region known to be critical for the development of addiction. Compartment-specific drug action was indeed observed. Clinically relevant concentrations of EtOH increased somatic but not dendritic BK channel open probability. Electrophysiological single-channel recordings and pharmacological analysis of the BK channel in excised patches from each region indicated a number of differences, suggestive of a compartment-specific expression of the ␤4 subunit of the BK channel, that might explain the differential alcohol sensitivity. These parameters included activation kinetics, calcium dependency, and toxin blockade. Reverse transcription-PCR showed that both BK channel ␤1 and ␤4 subunit mRNAs are found in the NAcc, although the signal for ␤1 is significantly weaker. Immunohistochemistry revealed that ␤1 subunits were found in both soma and dendrites, whereas ␤4 appeared restricted to the soma. These findings suggest that the ␤4 subunit may confer EtOH sensitivity to somatic BK channels, whereas the absence of ␤4 in the dendrite results in insensitivity to the drug. Consistent with this idea, acute EtOH potentiated ␣␤4 BK currents in transfected human embryonic kidney cells, whereas it failed to alter ␣␤1 BK channel-mediated currents. Finally, an EtOH concentration (50 mM) that increased BK channel open probability strongly decreased the duration of somatic-generated action potential in NAcc neurons.

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Effect of phospholipid surface charge on the conductance and gating of a Ca2+-activated K+ channel in planar lipid bilayers

Cited by 146 publications

References 33 publications

Enzyme Domain Affects the Movement of the Voltage Sensor in Ascidian and Zebrafish Voltage-sensing Phosphatases

Enzyme Domain Affects the Movement of the Voltage Sensor in Ascidian and Zebrafish Voltage-sensing Phosphatases

Charybdotoxin block of single Ca2+-activated K+ channels. Effects of channel gating, voltage, and ionic strength.

Somatic Localization of a Specific Large-Conductance Calcium-Activated Potassium Channel Subtype Controls Compartmentalized Ethanol Sensitivity in the Nucleus Accumbens

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