ATP inhibition of a mouse brain large‐conductance K<sup>+</sup> (mslo) channel variant by a mechanism independent of protein phosphorylation

Clark, Alan G.; Hall, Sarah; Shipston, Michael J.

doi:10.1111/j.1469-7793.1999.045aa.x

Cited by 21 publications

(14 citation statements)

References 31 publications

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“…The cloning and subcloning of the three splice variants have been described previously (ZERO and STREX-1 (22); and ZERO1/ 4⌬C, also referred to as mB2 (21,25)). ZERO lacks inserts at mammalian splice sites 1-5 and STREX-1 channels are identical except for a 59-amino acid cysteine-rich insert at mammalian splice site 2.…”

Section: Methodsmentioning

confidence: 99%

Alternative Splicing Switches Potassium Channel Sensitivity to Protein Phosphorylation

Tian

Duncan

Hammond

et al. 2001

Journal of Biological Chemistry

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Alternative exon splicing and reversible protein phosphorylation of large conductance calcium-activated potassium (BK) channels represent fundamental control mechanisms for the regulation of cellular excitability. BK channels are encoded by a single gene that undergoes extensive, hormonally regulated exon splicing. In native tissues BK channels display considerable diversity and plasticity in their regulation by cAMP-dependent protein kinase (PKA). Differential regulation of alternatively spliced BK channels by PKA may provide a molecular basis for the diversity and plasticity of BK channel sensitivities to PKA. Here we demonstrate that PKA activates BK channels lacking splice inserts (ZERO) but inhibits channels expressing a 59-amino acid exon at splice site 2 (STREX-1). Channel activation is dependent upon a conserved C-terminal PKA consensus motif (S869), whereas inhibition is mediated via a STREX-1 exon-specific PKA consensus site. Thus, alternative splicing acts as a molecular switch to determine the sensitivity of potassium channels to protein phosphorylation.Large conductance calcium-and voltage-activated potassium (BK) 1 channels link intracellular chemical signaling events with the electrical properties of excitable cells in the endocrine, nervous, and vascular systems (1-3). BK channels are further potently modulated by reversible protein phosphorylation (4 -7). In native tissues BK channels display considerable diversity and plasticity in their regulation by reversible protein phosphorylation. For example, cAMP-dependent protein kinase (PKA) phosphorylation activates BK channels in smooth muscle cells and many neurones but inhibits channel activity in endocrine cells of the anterior pituitary (5, 7-11). Furthermore, the direction of channel regulation by PKA can be modified during challenges to homeostasis (9 -11).The pore-forming ␣-subunits of BK channels are derived from a single gene (Slo) that undergoes extensive alternative splicing to produce channels with distinct phenotypes (12-15). Importantly, alternative splicing of the ␣-subunit is dynamically regulated in adults, for example during stress or pregnancy (15, 16). Thus the diversity and plasticity of responses to PKA-dependent protein phosphorylation observed between BK channels in native tissues may result either from differential modulation of alternatively spliced BK channel ␣-subunits (12-15) or through their interaction with different signaling complexes and ␤-subunits (17-19).To address whether BK channel alternative splice variants are differentially regulated by PKA-mediated protein phosphorylation, we have examined the regulation of three mouse (mslo) BK channel variants (20 -22) expressed in HEK293 cells. BK channels are regulated by multiple protein kinase signaling pathways (5,19,23,24). We have thus assayed the functional regulation of BK channel splice variants by directly activating PKA that remains closely associated with the channels in excised inside-out patches. EXPERIMENTAL PROCEDURESMolecular and Cell Biology-cDNAs encod...

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Section: Methodsmentioning

confidence: 99%

Alternative Splicing Switches Potassium Channel Sensitivity to Protein Phosphorylation

Tian

Duncan

Hammond

et al. 2001

Journal of Biological Chemistry

Self Cite

196

248

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“…(20,21) These splice variants give rise to channels with different functional properties, including calcium sensitivity, single-channel conductance, and regulation by intracellular signaling pathways. (22)(23)(24)(25) In addition, association of the Slo ␣-subunit with accessory subunits modulates channel characteristics or their cellular distribution. (26 -29) Large-conductance calcium-activated potassium channels also are subject to modulation by protein kinases, (26,30 -32) phosphatases, (33,34) and other signaling proteins.…”

Section: Introductionmentioning

confidence: 99%

Prostaglandin E2 Induces Interaction Between hSlo Potassium Channel and Syk Tyrosine Kinase in Osteosarcoma Cells

Rezzonico

Schmid-Alliana

Romey

et al. 2002

Journal of Bone and Mineral Research

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Prostaglandins (PGs) are important mediators of bone response to growth factors, hormones, inflammation, or mechanical strains. In this study, we show that in MG63 osteosarcoma cells, prostaglandin E 2 (PGE 2 ) produces the opening of a large conductance Ca 2؉ -dependent K ؉ channel (BK). This PGE 2 -mediated channel opening induces the recruitment of various tyrosine-phosphorylated proteins on the hSlo ␣-subunit of BK. Because the C-terminal domain of hSlo encompasses an immunoreceptor tyrosine-based activation motif (ITAM), we show that the Syk nonreceptor tyrosine kinase, reported yet to be expressed mainly in hematopoietic cells, is expressed also in osteoblastic cells, and recruited on this ITAM after a PGE 2 -induced docking/activation process. We show that Syk/hSlo association is dependent of an upstream Src-related tyrosine kinase activity, in accord with the classical two-step model described for immune receptors.

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“…In addition to a voltage and Ca 2+ dependency, BK channel activity can be modulated by changes in intracellular pH, Mg 2+ , ATP levels and phosphorylation via cyclic nucleotide-dependent kinases [1,2,4]. Thus, the low P o of BK channels recorded here from cultured type I SLFs under on-cell configuration may be attributable to the effects of one or more of these factors under resting or cultured conditions.…”

Section: Discussionmentioning

confidence: 83%

A voltage- and Ca2+-dependent big conductance K channel in cochlear spiral ligament fibrocytes

Liang

Niedzielski

Schulte

et al. 2003

Pflugers Arch - Eur J Physiol

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Evidence is accruing that spiral ligament fibrocytes (SLFs) play an important role in cochlear K(+) homeostasis, but little direct physiological data is available to support this concept. Here we report the presence and characterization of a voltage- and Ca(2+)-dependent big-conductance K (BK) channel in type I SLFs cultured from the gerbil cochlea. A single-channel conductance of 298+/-5.6 pS (n=28) was measured under symmetrical K(+). Membrane potentials for half-maximal open probability (P(o)) were -67, -45 and 85 mV with cytosolic free-Ca(2+) levels of 0.7 mM, 10 microM and 1 microM, respectively (n=8-14). The Hill coefficient for Ca(2+) affinity was 1.9 at a membrane potential of 60 mV (n=6). The BK channel showed very low activity (P(o)=0.0019, n=5) under normal physiological conditions, suggesting a low resting intracellular free [Ca(2+)]. Pharmacological results fit well with the profile of classic BK channels. The estimated half-maximal inhibitory concentration and Hill coefficient for tetraethylammonium were 0.086+/-0.021 mM and 0.99, respectively (n=4-9). In whole cell recordings, the voltage-activated outward K current was inhibited 85.7+/-4.5% (n=6) by 0.1 microM iberiotoxin. A steady-state kinetic model with two open and two closed stages best described the BK gating process (tau(o1) 0.23+/-0.08 ms, tau(o2) 1.40+/-0.32 ms; tau(c1) 0.26+/-0.09 ms, tau(c2) 3.10+/-1.2 ms; n=11). RT-PCR analyses revealed a splice variant of the BK channel alpha subunit in cultured type I SLFs and freshly isolated spiral ligament tissues. The BK channel is likely to play a major role in regulating the membrane potential of type I SLFs, which may in turn influence K(+) recycling dynamics in the mammalian cochlea.

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ATP inhibition of a mouse brain large‐conductance K⁺ (mslo) channel variant by a mechanism independent of protein phosphorylation

Abstract: Large conductance calcium-and voltage-activated potassium (BK) channels play a fundamental role in many physiological processes including action potential repolarization, modulation of calcium signals, hormone release and regulation of vascular tone (

Cited by 21 publications

References 31 publications

Alternative Splicing Switches Potassium Channel Sensitivity to Protein Phosphorylation

Alternative Splicing Switches Potassium Channel Sensitivity to Protein Phosphorylation

Prostaglandin E2 Induces Interaction Between hSlo Potassium Channel and Syk Tyrosine Kinase in Osteosarcoma Cells

A voltage- and Ca2+-dependent big conductance K channel in cochlear spiral ligament fibrocytes

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ATP inhibition of a mouse brain large‐conductance K+ (mslo) channel variant by a mechanism independent of protein phosphorylation

Abstract: Large conductance calcium-and voltage-activated potassium (BK) channels play a fundamental role in many physiological processes including action potential repolarization, modulation of calcium signals, hormone release and regulation of vascular tone (

Cited by 21 publications

References 31 publications

Alternative Splicing Switches Potassium Channel Sensitivity to Protein Phosphorylation

Alternative Splicing Switches Potassium Channel Sensitivity to Protein Phosphorylation

Prostaglandin E2 Induces Interaction Between hSlo Potassium Channel and Syk Tyrosine Kinase in Osteosarcoma Cells

A voltage- and Ca2+-dependent big conductance K channel in cochlear spiral ligament fibrocytes

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ATP inhibition of a mouse brain large‐conductance K⁺ (mslo) channel variant by a mechanism independent of protein phosphorylation