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Calcium-Activated Potassium Channel

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John P. Adelman – 1st expert on this subject based on the ideXlab platform

  • Gene structure and chromosome mapping of the human small-conductance Calcium-Activated Potassium Channel SK1 gene (KCNN1).
    Cytogenetic and Genome Research, 1999
    Co-Authors: Michael Litt, Chris T. Bond, Dante M. Lamorticella, John P. Adelman

    Abstract:

    Abstract. Small-conductance, Calcium-Activated Potassium Channels contribute to the afterhyperpolarization in central neurons and other cell types. Because these Channels regulate neurona

  • A human intermediate conductance Calcium-Activated Potassium Channel
    Proceedings of the National Academy of Sciences of the United States of America, 1997
    Co-Authors: Takahiro M. Ishii, Christopher P. Silvia, Birgit Hirschberg, Chris T. Bond, John P. Adelman, James Maylie

    Abstract:

    An intermediate conductance Calcium-Activated Potassium Channel, hIK1, was cloned from human pancreas. The predicted amino acid sequence is related to, but distinct from, the small conductance Calcium-Activated Potassium Channel subfamily, which is ≈50% conserved. hIK1 mRNA was detected in peripheral tissues but not in brain. Expression of hIK1 in Xenopus oocytes gave rise to inwardly rectifying Potassium currents, which were activated by submicromolar concentrations of intracellular calcium (K0.5 = 0.3 μM). Although the K0.5 for calcium was similar to that of small conductance Calcium-Activated Potassium Channels, the slope factor derived from the Hill equation was significantly reduced (1.7 vs. 3.5). Single-Channel current amplitudes reflected the macroscopic inward rectification and revealed a conductance level of 39 pS in the inward direction. hIK1 currents were reversibly blocked by charybdotoxin (Ki = 2.5 nM) and clotrimazole (Ki = 24.8 nM) but were minimally affected by apamin (100 nM), iberiotoxin (50 nM), or ketoconazole (10 μM). These biophysical and pharmacological properties are consistent with native intermediate conductance Calcium-Activated Potassium Channels, including the erythrocyte Gardos Channel.

  • determinants of apamin and d tubocurarine block in sk Potassium Channels
    Journal of Biological Chemistry, 1997
    Co-Authors: Takahiro M. Ishii, James Maylie, John P. Adelman

    Abstract:

    Abstract Small conductance Calcium-Activated Potassium Channels show a distinct pharmacology. Some, but not all, are blocked by the peptide toxin apamin, and apamin-sensitive Channels are also blocked by d-tubocurarine. Cloned SK Channels (small conductance Calcium-Activated Potassium Channel) recapitulate these properties. We have investigated the structural basis for these differences and found that two amino acid residues on either side of the deep pore are the primary determinants of sensitivity to apamin and differential block by d-tubocurarine. Therefore, the pharmacology of SK Channels compared with other Potassium Channels correlates with structural differences in the outer pore region. However, introduction of a tyrosine residue in the position analogous to that which determines sensitivity to external tetraethylammonium for voltage-gated Potassium Channels endows SK Channels with an equivalent tetraethylammonium sensitivity, indicating that the outer vestibules of the pores are similar. The pharmacology of Channels formed in oocytes coinjected with SK1 and SK2 mRNAs, or with SK1-SK2 dimer mRNA, show that SK subunits may form heteromeric Channels.

Wieslawa Jarmuszkiewicz – 2nd expert on this subject based on the ideXlab platform

  • A large-conductance Calcium-Activated Potassium Channel in potato tuber mitochondria
    Biochemical Journal, 2009
    Co-Authors: Izabela Koszela-piotrowska, Karolina Matkovic, Adam Szewczyk, Wieslawa Jarmuszkiewicz

    Abstract:

    In the present study, we describe the existence of a novel Potassium Channel in the plant (potato tuber) mitochondrial inner membrane. We found that substances known to modulate large-conductance Calcium-Activated Potassium Channel activity influenced the bioenergetics of potato tuber mitochondria. In isolated mitochondria, Ca2+ and NS1619 (a Potassium Channel opener) were found to depolarize the mitochondrial membrane potential and to stimulate resting respiration. These effects were blocked by iberiotoxin (a Potassium Channel inhibitor) in a Potassium-dependent manner. Additionally, the electrophysiological properties of the large-conductance Potassium Channel present in the potato tuber inner mitochondrial membrane are described in a reconstituted system, using planar lipid bilayers. After incorporation in 50/450 mM KCl gradient solutions, we recorded large-conductance Potassium Channel activity with conductance from 502 ± 15 to 615 ± 12 pS. The probability of Channel opening was increased by Ca2+ and reduced by iberiotoxin. Immunological analysis with antibodies raised against the mammalian plasma membrane large-conductance Ca2+-dependent K+ Channel identified a pore-forming α subunit and an auxiliary β2 subunit of the Channel in potato tuber mitochondrial inner membrane. These results suggest that a large-conductance Calcium-Activated Potassium Channel similar to that of mammalian mitochondria is present in potato tuber mitochondria.

  • A large-conductance Calcium-Activated Potassium Channel in potato (Solanum tuberosum) tuber mitochondria.
    Biochemical Journal, 2009
    Co-Authors: Izabela Koszela-piotrowska, Karolina Matkovic, Adam Szewczyk, Wieslawa Jarmuszkiewicz

    Abstract:

    : In the present study, we describe the existence of a novel Potassium Channel in the plant [potato (Solanum tuberosum) tuber] mitochondrial inner membrane. We found that substances known to modulate large-conductance Calcium-Activated Potassium Channel activity influenced the bioenergetics of potato tuber mitochondria. In isolated mitochondria, Ca2+ and NS1619 {1,3-dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2H-ben-zimidazole-2-one; a Potassium Channel opener} were found to depolarize the mitochondrial membrane potential and to stimulate resting respiration. These effects were blocked by iberiotoxin (a Potassium Channel inhibitor) in a Potassium-dependent manner. Additionally, the electrophysiological properties of the large-conductance Potassium Channel present in the potato tuber inner mitochondrial membrane are described in a reconstituted system, using planar lipid bilayers. After incorporation in 50/450 mM KCl gradient solutions, we recorded large-conductance Potassium Channel activity with conductance from 502+/-15 to 615+/-12 pS. The probability of Channel opening was increased by Ca2+ and reduced by iberiotoxin. Immunological analysis with antibodies raised against the mammalian plasma-membrane large-conductance Ca2+-dependent K+ Channel identified a pore-forming alpha subunit and an auxiliary beta2 subunit of the Channel in potato tuber mitochondrial inner membrane. These results suggest that a large-conductance Calcium-Activated Potassium Channel similar to that of mammalian mitochondria is present in potato tuber mitochondria.

A Schaefer – 3rd expert on this subject based on the ideXlab platform

  • Polymorphisms in the fetal progesterone receptor and a Calcium-Activated Potassium Channel isoform are associated with preterm birth in an Argentinian population
    Journal of Perinatology, 2013
    Co-Authors: P C Mann, Margaret E. Cooper, Kelli K. Ryckman, Belén Comas, Juan Antonio Gili, S Crumley, Elise N.a. Bream, Heather M. Byers, Travis L. Piester, A Schaefer

    Abstract:

    Objective: To investigate genetic etiologies of preterm birth (PTB) in Argentina through evaluation of single-nucleotide polymorphisms (SNPs) in candidate genes and population genetic admixture. Study Design: Genotyping was performed in 389 families. Maternal, paternal and fetal effects were studied separately. Mitochondrial DNA (mtDNA) was sequenced in 50 males and 50 females. Y-chromosome anthropological markers were evaluated in 50 males. Result: Fetal association with PTB was found in the progesterone receptor ( PGR , rs1942836; P =0.004). Maternal association with PTB was found in small conductance calcium activated Potassium Channel isoform 3 ( KCNN3 , rs883319; P =0.01). Gestational age associated with PTB in PGR rs1942836 at 32–36 weeks ( P =0.0004). MtDNA sequencing determined 88 individuals had Amerindian consistent haplogroups. Two individuals had Amerindian Y-chromosome consistent haplotypes. Conclusion: This study replicates single locus fetal associations with PTB in PGR , maternal association in KCNN3 , and demonstrates possible effects for divergent racial admixture on PTB.

  • Polymorphisms in the fetal progesterone receptor and a Calcium-Activated Potassium Channel isoform are associated with preterm birth in an Argentinian population
    Journal of Perinatology, 2012
    Co-Authors: P C Mann, Margaret E. Cooper, Kelli K. Ryckman, Belén Comas, Juan Antonio Gili, S Crumley, Elise N.a. Bream, Heather M. Byers, Travis L. Piester, A Schaefer

    Abstract:

    Polymorphisms in the fetal progesterone receptor and a Calcium-Activated Potassium Channel isoform are associated with preterm birth in an Argentinian population