Inhibition of human ether a go-go potassium channels by Ca2+/calmodulin

Schönherr, Roland; Löber, Karsten; Heinemann, Stefan

doi:10.1093/emboj/19.13.3263

Cited by 126 publications

(203 citation statements)

References 36 publications

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“…This is in keeping with Keen's proposal (21). Moreover, using this assay, we were unable to detect an interaction of CaM with baits known to interact with Ca 2ϩ -CaM but not with apo-CaM (baits such as the C-terminal region of the NMDA receptor (18); the Eag potassium channel (28); and the CaM binding site of myosin light chain kinase (7)). Conversely, when neurogranin, which binds to apo-CaM but not to Ca 2ϩ -CaM, was used (7), a clear interaction could be seen (Fig.…”

Section: Determinants In Cam That Are Required For Binding Tosupporting

confidence: 83%

The Identification and Characterization of a Noncontinuous Calmodulin-binding Site in Noninactivating Voltage-dependent KCNQ Potassium Channels

Yus-Nájera

Santana-Castro

Villarroel

2002

Journal of Biological Chemistry

189

266

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We show here that in a yeast two-hybrid assay calmodulin (CaM) interacts with the intracellular C-terminal region of several members of the KCNQ family of potassium channels. CaM co-immunoprecipitates with KCNQ2, KCNQ3, or KCNQ5 subunits better in the absence than in the presence of Ca 2؉ . Moreover, in twohybrid assays where it is possible to detect interactions with apo-CaM but not with Ca 2؉ -bound calmodulin, we localized the CaM-binding site to a region that is predicted to contain two ␣-helices (A and B). These two helices encompass ϳ85 amino acids, and in KCNQ2 they are separated by a dispensable stretch of ϳ130 amino acids. Within this CaM-binding domain, we found an IQ-like CaM-binding motif in helix A and two overlapping consensus 1-5-10 CaM-binding motifs in helix B. Point mutations in helix A or B were capable of abolishing CaM binding in the two-hybrid assay. Moreover, glutathione S-transferase fusion proteins containing helices A and B were capable of binding to CaM, indicating that the interaction with KCNQ channels is direct. Fulllength CaM (both N and C lobes) and a functional EF-1 hand were required for these interactions to occur. These observations suggest that apo-CaM is bound to neuronal KCNQ channels at low resting Ca 2؉ levels and that this interaction is disturbed when the [Ca 2؉ ] is raised. Thus, we propose that CaM acts as a mediator in the Ca 2؉ -dependent modulation of KCNQ channels.The KCNQ transmembrane proteins are members of a family of voltage-dependent potassium selective channels that are involved in the control of cellular excitability. Remarkably, mutations in four of the five known members of this family have been associated with different hereditary human disorders. While mutations in the KCNQ1 subunit (KvQT1) lead to arrhythmia in the human long QT syndrome, mutations in KCNQ2 or KCNQ3 are associated with a benign form of epilepsy. It has also been shown that KCNQ4 is mutated in a dominant form of progressive hearing loss (1).With regards to the normal physiology of this protein family, the KCNQ2 and KCNQ3 subunits have been shown to form M-type potassium channels whose expression is restricted to neuronal tissue (2). Moreover, in some brain areas and neuronal tissues, KCNQ4 and KCNQ5 also contribute to the formation of M channels, suggesting that the different combinations of KCNQ subunits may be in part responsible for the diversity of M channel properties (1). The M current (I M ) is a subthreshold noninactivating voltage-dependent potassium current that is found in many neuronal cell types. The M current controls membrane excitability, and it has been shown to be modulated by a variety of intracellular signals that in turn dramatically affect the firing rate of neurons. Among those intracellular signals, Ca 2ϩ has been shown to mediate the inhibition of I M by B 2 bradykinin receptors in sympathetic neurons (3). Indeed, intracellular Ca 2ϩ can suppress the activity of M channels under conditions that do not support enzymatic activities such as phosphorylation (4). Th...

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Section: Determinants In Cam That Are Required For Binding Tosupporting

confidence: 83%

The Identification and Characterization of a Noncontinuous Calmodulin-binding Site in Noninactivating Voltage-dependent KCNQ Potassium Channels

Yus-Nájera

Santana-Castro

Villarroel

2002

Journal of Biological Chemistry

189

266

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“…X16002). Overlap-extension mutagenesis as described previously (40) was performed to generate the following constructs: Kv1.4Δ2-110, C13S, H16A, H35A, and combinations thereof.…”

Section: Methodsmentioning

confidence: 99%

Heme impairs the ball-and-chain inactivation of potassium channels

Sahoo

Goradia

Ohlenschläger

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Significance Heme, traditionally viewed as a stable protein cofactor such as in hemoglobin, also serves as an acute signaling molecule and is cytotoxic at high concentrations. Here, we show that free intracellular heme potently enhances A-type potassium channel function. Such channels determine action potential frequency in excitable cells, and their dysfunction often contributes to pathological hyperexcitability, such as in pain and epilepsy. Binding of free heme at nanomolar concentrations to the “ball-and-chain” N terminus of A-type potassium channels, which typically closes the channels, introduces a stable structure in the otherwise disordered region and allows for a greater efflux of potassium ions, thus reducing cellular excitability. Heme therefore could be a powerful negative-feedback regulator in brain and muscle function.

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“…The ubiquitous Ca 2ϩ -binding protein CaM was identified as the Ca 2ϩ sensor protein that activates K Ca channels in response to rising [Ca 2ϩ ] i but closes EAG channels. This reverse action is regulated by CaM binding to the C terminus of hEAG1 (24) and to the ␣-subunit of small conductance K Ca channels (25). Interestingly the TRPV6 protein also binds CaM in a Ca 2ϩ -dependent manner (8), which makes it an attractive candidate for the Ca 2ϩ sensor.…”

Section: Camentioning

confidence: 99%

The Recombinant Human TRPV6 Channel Functions as Ca2+Sensor in Human Embryonic Kidney and Rat Basophilic Leukemia Cells

Bödding

Wissenbach

Flockerzi

2002

Journal of Biological Chemistry

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The activation mechanism of the recently cloned human transient receptor potential vanilloid type 6 (TRPV6) channel, originally termed Ca 2؉ transporterlike protein and Ca 2؉ transporter type 1, was investigated in whole-cell patch-clamp experiments using transiently transfected human embryonic kidney and rat basophilic leukemia cells. The TRPV6-mediated currents are highly Ca 2؉ -selective, show a strong inward rectification, and reverse at positive potentials, which is similar to store-operated Ca 2؉ entry in electrically nonexcitable cells. Calcium is involved in a multitude of intracellular signal transduction mechanisms ranging from contraction to secretion. To achieve a high bandwidth of signal transmission with sometimes even opposing effects, cells need to control the spatio-temporal resolution of their Ca 2ϩ signals (1). In nonexcitable cells the rise in [Ca 2ϩ ] i 1 during stimulation of G-proteincoupled receptors or receptor tyrosine kinases is regulated in a complex fashion by Ca 2ϩ release from endogenous IP 3 -sensitive stores followed by store-operated Ca 2ϩ influx across the plasma membrane. One of the best characterized store-operated Ca 2ϩ entry pathways is the Ca 2ϩ release-activated Ca 2ϩ current, termed I CRAC (2, 3).The molecular identity of store-operated channels is a matter of debate. Several members of the TRP family, a group of Ca 2ϩ permeable channels related to the Drosophila melanogaster TRP gene product, have been implicated in store-dependent cation influx (4, 5). However, so far, none of the trp genes has been shown to encode channels with the ion-permeation properties and the sensitivity to store depleting agents of CRAC channels.The family of the trp genes in vertebrates can be divided into three subfamilies, based on similarities in the structures of the encoded proteins (6), the TRPC, the TRPM, and the TRPV subfamilies. Members of the TRPV subfamily appear to be regulated by physical or chemical stimuli such as heat, osmotic, or mechanical stress. The recently cloned human TRPV6 gene product (GenBank TM accession no. CAC20417), formerly called CaT-L or TRP8 (7, 8) or CaT1 (9), belongs into this group. Human TRPV6 channels (7), like rat TRPV6 (formerly called rat CaT1; Ref. 10) and rabbit TRPV5 channels (former ECaC for epithelial Ca 2ϩ channel; Ref. 11), show a high Ca 2ϩ selectivity, Ca 2ϩ and Na ϩ permeation properties indicative of an anomalous mole fraction behavior, and current-voltage relationships similar to CRAC channels.Recently these common features between TRPV6 and CRAC channels were demonstrated by two groups (12, 13). In addition Voets et al. (13) also revealed several differences between I CRAC in RBL cells and TRPV6-mediated Ca 2ϩ currents when expressed in HEK cells, including insensitivity of TRPV6 channels to store depletion and the effect of intracellular Mg 2ϩ , which causes voltage-dependent block of TRPV6, but not of CRAC channels. In contrast, Yue et al. (12) demonstrated activation of TRPV6 channels in CHO cells by depletion of calcium stores with...

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Inhibition of human ether a go-go potassium channels by Ca2+/calmodulin

Cited by 126 publications

References 36 publications

The Identification and Characterization of a Noncontinuous Calmodulin-binding Site in Noninactivating Voltage-dependent KCNQ Potassium Channels

The Identification and Characterization of a Noncontinuous Calmodulin-binding Site in Noninactivating Voltage-dependent KCNQ Potassium Channels

Heme impairs the ball-and-chain inactivation of potassium channels

The Recombinant Human TRPV6 Channel Functions as Ca2+Sensor in Human Embryonic Kidney and Rat Basophilic Leukemia Cells

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