Modulation of calcium-activated potassium channels (original) (raw)
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Pharmacological Reviews, 2005
Elimination of the BK Ca channel's high-affinity Ca 2ϩ sensitivity. J Gen Physiol 120:173-189. Cox DH (2005) The BK Ca channel's Ca 2ϩ -binding sites, multiple sites, multiple ions. J Gen Physiol 125:253-255. Faber ESL and Sah P (2003) Calcium-activated potassium channels: multiple contributions to neuronal function. Neuroscientist 9:181-194. Fanger CM, Ghanshani S, Logsdon NJ, Rauer H, Kalman K, Zhou J, Beckingham K, Chandy KG, Cahalan MD, and Aiyar J (1999) Calmodulin mediates calciumdependent activation of the intermediate conductance K Ca channel, IK Ca 1. J Biol Chem 274:5746 -5754. Ishii TM, Silvia C, Hirschberg B, Bond CT, Adelman JP, and Maylie J (1997) A human intermediate conductance calcium-activated potassium channel. Proc Natl Acad Sci USA 94:11651-11656. Joiner WJ, Tang MD, Wang LY, Dworetzky SI, Boissard CG, Gan L, Gribkoff VK, and Kaczmarek LK (1998) Formation of intermediate-conductance calciumactivated potassium channels by interaction of Slack and Slo subunits. Nat Neurosci 1:462-469. Joiner WJ, Wang LY, Tang MD, and Kaczmarek LK hSK4, a member of a novel subfamily of calcium-activated potassium channels. Proc Natl Acad Sci USA 94:11013-11018. Kohler M, Hirschberg B, Bond CT, Kinzie JM, Marrion NV, Maylie J, and Adelman JP (1996) Small-conductance, calcium-activated potassium channels from mammalian brain. Science 273:1709 -1714. Lingle CJ (2002) Setting the stage for molecular dissection of the regulatory components of BK channels. J Gen Physiol 120:261-265. Magleby KL (2003) Gating mechanism of BK (Slo1) channels: so near, yet so far. J Gen Physiol 121:81-96. Moczydlowski EG (2004) BK channel news: full coverage on the calcium bowl. J Gen Physiol 123:471-473. Schreiber M and Salkoff L (1997) A novel calcium-sensing domain in the BK channel. Biophys J 73:1355-1363. Schreiber M, Wei A, Yuan A, Gaut J, Saito M, and Salkoff L (1998) Slo3, a novel pH-sensitive K ϩ channel from mammalian spermatocytes. J Biol Chem 273:3509 -3516. Schumacher MA, Rivard AF, Bachinger HP, and Adelman JP (2001) Structure of the gating domain of a Ca 2ϩ -activated K ϩ channel complexed with Ca 2ϩ /calmodulin. Nature (Lond) 410:1120 -1124. (2002) Mechanism of magnesium activation of calcium-activated potassium channels. Nature (Lond) 418:876 -880. Stocker M (2004) Ca 2ϩ -activated Kϩ channels: molecular determinants and function of the SK family. Nat Rev Neurosci 5:758 -770. Weiger TM, Hermann A, and Levitan IB (2002) Modulation of calcium-activated potassium channels. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 188:79 -87. Xia XM, Fakler B, Rivard A, Wayman G, Johnson-Pais T, Keen JE, Ishii T, Hirschberg B, Bond CT, Lutsenko S, et al. (1998) Mechanism of calcium gating in small-conductance calcium-activated potassium channels. Nature (Lond) 395:503-507. Xia XM, Zeng X, and Lingle CJ (2002) Multiple regulatory sites in large-conductance calcium-activated potassium channels. Nature (Lond) 418:880 -884. Yuan A, Santi CM, Wei A, Wang ZW, Pollak K, Nonet M, Kaczmarek L, Crowder CM, and Salkoff L (2003) The sodium-activated potassium channel is encoded by a member of the Slo gene family. Neuron 37:765-773. IUPHAR HGNC Other K
Proceedings of the National Academy of Sciences, 1996
The pore-forming α subunit of large conductance voltage- and Ca 2+ -sensitive K (MaxiK) channels is regulated by a β subunit that has two membrane-spanning regions separated by an extracellular loop. To investigate the structural determinants in the pore-forming α subunit necessary for β-subunit modulation, we made chimeric constructs between a human MaxiK channel and the Drosophila homologue, which we show is insensitive to β-subunit modulation, and analyzed the topology of the α subunit. A comparison of multiple sequence alignments with hydrophobicity plots revealed that MaxiK channel α subunits have a unique hydrophobic segment (S0) at the N terminus. This segment is in addition to the six putative transmembrane segments (S1–S6) usually found in voltage-dependent ion channels. The transmembrane nature of this unique S0 region was demonstrated by in vitro translation experiments. Moreover, normal functional expression of signal sequence fusions and in vitro N-linked glycosylation ...
Controlling potassium channel activities: Interplay between the membrane and intracellular factors
Proceedings of the National Academy of Sciences of the United States of America, 2001
Neural signaling is based on the regulated timing and extent of channel opening; therefore, it is important to understand how ion channels open and close in response to neurotransmitters and intracellular messengers. Here, we examine this question for potassium channels, an extraordinarily diverse group of ion channels. Voltage-gated potassium (Kv) channels control action-potential waveforms and neuronal firing patterns by opening and closing in response to membrane-potential changes. These effects can be strongly modulated by cytoplasmic factors such as kinases, phosphatases, and small GTPases. A Kv alpha subunit contains six transmembrane segments, including an intrinsic voltage sensor. In contrast, inwardly rectifying potassium (Kir) channels have just two transmembrane segments in each of its four pore-lining alpha subunits. A variety of intracellular second messengers mediate transmitter and metabolic regulation of Kir channels. For example, Kir3 (GIRK) channels open on binding...
Pharmacological Reviews, 2003
This summary article presents an overview of the molecular relationships among the voltage-gated potassium channels and a standard nomenclature for them, which is derived from the IUPHAR Compendium of Voltage-Gated Ion Channels. 1 The complete Compendium, including data tables for each member of the potassium channel family can be found at http://www.iuphar-db.org/iuphar-ic/. Almost a decade ago, a standardized nomenclature for the six-transmembrane domain (TM), voltage-gated K ϩ channel genes-the K V naming system-was widely adopted . This nomenclature was based on deduced phylogenetic relationships; channels that shared 65% sequence identity being assigned to one subfamily. A parallel nomenclature-KCN-was developed by the Human Genome Organisation (HUGO) . Since then, the K ϩ channel superfamily of genes has greatly expanded, requiring an update of the naming system.
Proceedings of the National Academy of Sciences, 1999
Voltage-dependent and calcium-sensitive K ؉ (MaxiK) channels are key regulators of neuronal excitability, secretion, and vascular tone because of their ability to sense transmembrane voltage and intracellular Ca 2؉ . In most tissues, their stimulation results in a noninactivating hyperpolarizing K ؉ current that reduces excitability. In addition to noninactivating MaxiK currents, an inactivating MaxiK channel phenotype is found in cells like chromaffin cells and hippocampal neurons. The molecular determinants underlying inactivating MaxiK channels remain unknown. Herein, we report a transmembrane  subunit (2) that yields inactivating MaxiK currents on coexpression with the pore-forming ␣ subunit of MaxiK channels. Intracellular application of trypsin as well as deletion of 19 N-terminal amino acids of the 2 subunit abolished inactivation of the ␣ subunit. Conversely, fusion of these N-terminal amino acids to the noninactivating smooth muscle 1 subunit leads to an inactivating phenotype of MaxiK channels. Furthermore, addition of a synthetic N-terminal peptide of the 2 subunit causes inactivation of the MaxiK channel ␣ subunit by occluding its K ؉ -conducting pore resembling the inactivation caused by the ''ball'' peptide in voltage-dependent K ؉ channels. Thus, the inactivating phenotype of MaxiK channels in native tissues can result from the association with different  subunits.
IUPHAR/BPS Guide to Pharmacology CITE, 2019
Calcium- and sodium- activated potassium channels are members of the 6TM family of K channels which comprises the voltage-gated KV subfamilies, including the KCNQ subfamily, the EAG subfamily (which includes herg channels), the Ca2+-activated Slo subfamily (actually with 6 or 7TM) and the Ca2+- and Na+-activated SK subfamily (nomenclature as agreed by the NC-IUPHAR Subcommittee on Calcium- and sodium-activated potassium channels [124]). As for the 2TM family, the pore-forming a subunits form tetramers and heteromeric channels may be formed within subfamilies (e.g. KV1.1 with KV1.2; KCNQ2 with KCNQ3).
Proceedings of the National Academy of Sciences, 1999
Voltage-dependent and calcium-sensitive K + (MaxiK) channels are key regulators of neuronal excitability, secretion, and vascular tone because of their ability to sense transmembrane voltage and intracellular Ca 2+ . In most tissues, their stimulation results in a noninactivating hyperpolarizing K + current that reduces excitability. In addition to noninactivating MaxiK currents, an inactivating MaxiK channel phenotype is found in cells like chromaffin cells and hippocampal neurons. The molecular determinants underlying inactivating MaxiK channels remain unknown. Herein, we report a transmembrane β subunit (β2) that yields inactivating MaxiK currents on coexpression with the pore-forming α subunit of MaxiK channels. Intracellular application of trypsin as well as deletion of 19 N-terminal amino acids of the β2 subunit abolished inactivation of the α subunit. Conversely, fusion of these N-terminal amino acids to the noninactivating smooth muscle β1 subunit leads to an inactivating ph...
Calcium-activated potassium channels expressed from cloned complementary DNAs
Neuron, 1992
Calcium-activated potassium channels were expressed in Xenopus oocytes by injection of RNA transcribed in vitro from complementary DNAs derived from the s/o locus of Drosophila melanogaster. Many cDNAs were found that encode closely related proteinsof about 1200 aa. The predicted sequences of these proteins differ by thesubstitution of blocksof aminoacids at five identified positions within the putative intracellular region between residues 327 and 797. Excised inside-out membrane patches showed potassium channel openings only with micromolar calcium present at the cytoplasmic side; activity increased steeply both with depolarization and with increasing calcium concentration. The singlechannel conductance was 126 pS with symmetrical potassium concentrations. The mean open time of the channels was clearly different for channels having different subsituent blocks of amino acids. The results suggest that alternative splicing gives rise to a large family of functionally diverse, calcium-activated potassium channels.