Cloning, expression, and distribution of a Ca(2+)-activated K+ channel beta-subunit from human brain.

Tseng-Crank, Julie; Godinot, Nathalie; Johansen, Teit E.; Ahring, Philip K.; Strøbæk, Dorte; Mertz, Robert J.; Foster, Christine D.; Olesen, Søren‐Peter; Reinhart, Peter H.

doi:10.1073/pnas.93.17.9200

Cited by 151 publications

(135 citation statements)

References 44 publications

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“…Functional expression of channel proteins was determined by activation of iberiotoxin sensitive outward currents. As reported previously (30,31), average currents recorded from oocytes injected with both channel subunit cRNAs were larger at all voltages than those recorded from oocytes injected with hSlo alone (3225.8 Ϯ 256.9 nA (n ϭ 25) versus 2671.9 Ϯ 365.5 nA (n ϭ 14) at 60 mV). As shown in Fig.…”

Section: Reconstitution Of ␤ 2 -Adrenergic Stimulation Of Maxi-k Chanmentioning

confidence: 51%

Reconstitution of β-Adrenergic Modulation of Large Conductance, Calcium-activated Potassium (Maxi-K) Channels in Xenopus Oocytes

Nara

Dhulipala

Wang

et al. 1998

Journal of Biological Chemistry

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The human large conductance, calcium-activated potassium (maxi-K) channel (␣ and ␤ subunits) and ␤ 2 -adrenergic receptor genes were coexpressed in Xenopus oocytes in order to study the mechanism of ␤-adrenergic modulation of channel function. Isoproterenol and forskolin increased maxi-K potassium channel currents in voltage-clamped oocytes expressing the receptor and both channel subunits by 33 ؎ 5% and 35 ؎ 8%, respectively, without affecting current activation or inactivation. The percentage of stimulation by isoproterenol and forskolin was not different in oocytes coexpressing the ␣ and ␤ subunits versus those expressing the only the ␣ subunit, suggesting that the ␣ subunit is the target for regulation. The stimulatory effect of isoproterenol was almost completely blocked by intracellular injection of the cyclic AMP dependent protein kinase (cAMP-PK) regulatory subunit, whereas injection of a cyclic GMP dependent protein kinase inhibitory peptide had little effect, indicating that cellular coupling of ␤ 2 -adrenergic receptors to maxi-K channels involves endogenous cAMP-PK. Mutation of one of several potential consensus cAMP-PK phosphorylation sites (serine 869) on the ␣ subunit almost completely inhibited ␤-adrenergic receptor/channel stimulatory coupling, whereas forskolin still stimulated currents moderately (16 ؎ 4%). These data demonstrate that physiological coupling between ␤ 2 receptors and maxi-K channels occurs by the cAMP-PK mediated phosphorylation of serine 869 on the ␣ subunit on the channel.Hormones and neurotransmitters alter cellular excitability in part through the modulation of plasmalemmal ion channel function. Two prominent mechanisms by which hormone/neurotransmitter receptor occupation results in the modulation of membrane ion channels are the phosphorylation of one or more residues of the target channel protein(s) (for review see Ref. 1), and the binding of a heterotrimeric G protein subunit to a modulatory channel domain (for review see Ref.2). Stimulation of ␤ 2 receptors relaxes smooth muscle by modulating the activity of several protein targets (3). One prominent target of ␤ 2 adrenergic signaling in smooth muscle is the large conductance, calcium-activated potassium (maxi-K) 1 channel, the activity of which is markedly increased following receptor binding (4 -7). Modulation of maxi-K channel activity appears to be a functionally important component of ␤-adrenergic relaxation of smooth muscle, since charybdotoxin and iberiotoxin, selective peptide inhibitors of maxi-K channels, markedly inhibit the relaxant ability of isoproterenol and other ␤-adrenergic agents (8 -10). The molecular mechanism by which channel modulation occurs is unclear, however, since studies have indicated that single maxi-K channels are regulated by phosphorylation and by phosphorylation-independent G protein interactions (5,6,(11)(12)(13)(14). Further, with respect to channel phosphorylation, maxi-K channel stimulation has been attributed to channel phosphorylation by cAMP-dependent protein kinase (5,6,11,15,...

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Section: Reconstitution Of ␤ 2 -Adrenergic Stimulation Of Maxi-k Chanmentioning

confidence: 51%

Reconstitution of β-Adrenergic Modulation of Large Conductance, Calcium-activated Potassium (Maxi-K) Channels in Xenopus Oocytes

Nara

Dhulipala

Wang

et al. 1998

Journal of Biological Chemistry

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“…Tissue Distribution of ␤ Subunit mRNA-The ␤1 subunit expression is enriched in smooth muscle, particularly aorta, but shows very little expression in brain or other tissues that do not contain smooth muscle (25,28). In order to determine where H␤2, H␤3, and H␤4 are expressed, we hybridized specific cDNA probes for each to a battery of mRNAs on Northern blots (Fig.…”

Section: Resultsmentioning

confidence: 99%

Cloning and Functional Characterization of Novel Large Conductance Calcium-activated Potassium Channel β Subunits, hKCNMB3 and hKCNMB4

Brenner¹,

Jegla²,

Wickenden³

et al. 2000

Journal of Biological Chemistry

455

603

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We present the cloning and characterization of two novel calcium-activated potassium channel ␤ subunits, hKCNMB3 and hKCNMB4, that are enriched in the testis and brain, respectively. We compare and contrast the steady state and kinetic properties of these ␤ subunits with the previously cloned mouse ␤1 (mKCNMB1) and the human ␤2 subunit (hKCNMB2). Once inactivation is removed, we find that hKCNMB2 has properties similar to mKCNMB1. hKCNMB2 slows Hslo1 channel gating and shifts the current-voltage relationship to more negative potentials. hKCNMB3 and hKCNMB4 have distinct effects on slo currents not observed with mKCNMB1 and hKCNMB2. Although we found that hKCNMB3 does interact with Hslo channels, its effects on Hslo1 channel properties were slight, increasing Hslo1 activation rates. In contrast, hKCNMB4 slows Hslo1 gating kinetics, and modulates the apparent calcium sensitivity of Hslo1. We found that the different effects of the ␤ subunits on some Hslo1 channel properties are calcium-dependent. mKCNMB1 and hKCNMB2 slow activation at 1 M but not at 10 M free calcium concentrations. hKC-NMB4 decreases Hslo1 channel openings at low calcium concentrations but increases channel openings at high calcium concentrations. These results suggest that ␤ subunits in diverse tissue types fine-tune slo channel properties to the needs of a particular cell.The large conductance calcium-activated potassium channel (BK) 1 is a unique member of the six transmembrane domain potassium channel family that is activated by voltage and calcium. BK channels are composed of a pore-forming ␣ subunit (1, 2) and, in some tissues, are tightly associated with an accessory ␤ subunit (3, 4). BK channels have diverse physiological properties with tissue-specific distribution. In neurons, BK channels are functionally colocalized with calcium channels (5, 6), shape action potential wave forms (7,8), and modulate neurotransmitter release (9, 10). In smooth muscle, BK channels regulate constriction in arteries (11), uterine contraction (12), and filtration rate in the kidney (13). Unlike other potassium channel families, BK channels can as yet only be attributed to a single gene, slowpoke (slo), that encodes the poreforming ␣ subunit of the channel. In light of the broad tissue localization and diverse functional properties, it is not surprising that a number of mechanisms have been identified that alter slo channel properties. These include alternative splicing of the slo RNA (14 -18), heteromeric assembly with other subunits (slak) (19), and modification by phosphorylation/dephosphorylation (20 -22) and oxidation/reduction (23).In addition, accessory ␤ subunits are a means of generating BK channel diversity. Coexpression of the ␤1 subunit in Xenopus oocytes increases the apparent calcium sensitivity, slows activation kinetics, and increases charybdotoxin binding affinity (24 -27). ␤1 subunit mRNA is enriched in smooth muscle (28) and can account for the apparent increased calcium sensitivity of BK channels in that tissue relative to skeletal muscl...

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“…To elucidate the mechanism of the CO action, we applied CO gas or the CO donor reagent [Ru(CO) 3 Cl 2 ] 2 (12,16,22) to heterologously expressed channels composed of the pore-forming subunit Slo1 alone, as well as those composed of Slo1 and ␤1, the predominant auxiliary subunit in smooth muscle cells (23). In both channel types, CO gas and the CO donor consistently and repeatedly increased open probability in the virtual absence of Ca 2ϩ in the cell-free excised patch configuration in a fully reversible manner without altering the unitary current amplitude [ Fig.…”

Section: Resultsmentioning

confidence: 99%

The RCK1 high-affinity Ca ²⁺ sensor confers carbon monoxide sensitivity to Slo1 BK channels

Hou

Heinemann

et al. 2008

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

105

126

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Carbon monoxide (CO) is a lethal gas, but it is also increasingly recognized as a physiological signaling molecule capable of regulating a variety of proteins. Among them, large-conductance Ca 2؉ -and voltage-gated K ؉ (Slo1 BK) channels, important in vasodilation and neuronal firing, have been suggested to be directly stimulated by CO. However, the molecular mechanism of the stimulatory action of CO on the Slo1 BK channel has not been clearly elucidated. We report here that CO reliably and repeatedly activates Slo1 BK channels in excised membrane patches in the absence of Ca 2؉ in a voltage-sensor-independent manner. The stimulatory action of CO on the Slo1 BK channel requires an aspartic acid and two histidine residues located in the cytoplasmic RCK1 domain, and the effect persists under the conditions known to inhibit the conventional interaction between CO and heme in other proteins. We propose that CO acts as a partial agonist for the high-affinity divalent cation sensor in the RCK1 domain of the Slo1 BK channel.C arbon monoxide (CO) is a deadly poisonous gas. However, CO is physiologically produced during the course of heme catabolism by heme oxygenases (HMOXs) in an oxygendependent manner, and it is increasingly recognized as a biological signaling molecule important in numerous physiological and pathophysiological processes, including synaptic plasticity, regulation of vascular tone, and tumor proliferation (1). To regulate the wide array of cellular functions, CO typically exerts its action by binding to the reduced heme iron center (Fe 2ϩ ) in hemoproteins (2, 3), thereby altering the way the heme prosthetic group is coordinated (4). The heme-dependent action of CO is exemplified by its stimulatory effect on soluble guanylate cyclase, in which binding of CO to the reduced heme iron center increases the catalytic activity, leading to an enhanced production of cGMP (4, 5).Large-conductance Ca 2ϩ -and voltage-activated K ϩ (Slo1 BK or K Ca 1.1) channels, important in many physiological phenomena, including oxygen sensing, vasodilation, and neuronal firing (6, 7), are also stimulated by . The modulation of Slo1 BK channels by CO is physiologically and pathophysiologically important. For example, the stimulatory effect of CO on Slo1 BK channels underlies its well documented vasodilatory effect (9,11,(13)(14)(15), and the use of CO has been suggested as a potential therapeutic strategy against pulmonary hypertension (11). Production of CO by HMOXs requires oxygen (1), and this oxygen dependence raises the possibility that changes in cellular oxygen tension regulate the Slo1 BK channel activity indirectly by regulating the availability of CO (16). HMOX-2, one member of the HMOX family, may colocalize with Slo1 to allow efficient modulation of the channel by CO according to the local oxygen level (16).Gating of the Slo1 BK channel involves allosteric interactions among the main pore gate, voltage sensor domains, and cytoplasmic RCK1 and RCK2 domains with multiple divalent cation sensors (17,18). Although incre...

show abstract

Cloning, expression, and distribution of a Ca(2+)-activated K+ channel beta-subunit from human brain.

Abstract: We have cloned and expressed a Ca2+-

Cited by 151 publications

References 44 publications

Reconstitution of β-Adrenergic Modulation of Large Conductance, Calcium-activated Potassium (Maxi-K) Channels in Xenopus Oocytes

Reconstitution of β-Adrenergic Modulation of Large Conductance, Calcium-activated Potassium (Maxi-K) Channels in Xenopus Oocytes

Cloning and Functional Characterization of Novel Large Conductance Calcium-activated Potassium Channel β Subunits, hKCNMB3 and hKCNMB4

The RCK1 high-affinity Ca ²⁺ sensor confers carbon monoxide sensitivity to Slo1 BK channels

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Cloning, expression, and distribution of a Ca(2+)-activated K+ channel beta-subunit from human brain.

Abstract: We have cloned and expressed a Ca2+-

Cited by 151 publications

References 44 publications

Reconstitution of β-Adrenergic Modulation of Large Conductance, Calcium-activated Potassium (Maxi-K) Channels in Xenopus Oocytes

Reconstitution of β-Adrenergic Modulation of Large Conductance, Calcium-activated Potassium (Maxi-K) Channels in Xenopus Oocytes

Cloning and Functional Characterization of Novel Large Conductance Calcium-activated Potassium Channel β Subunits, hKCNMB3 and hKCNMB4

The RCK1 high-affinity Ca 2+ sensor confers carbon monoxide sensitivity to Slo1 BK channels

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The RCK1 high-affinity Ca ²⁺ sensor confers carbon monoxide sensitivity to Slo1 BK channels