A Dominant Negative Isoform of the Long QT Syndrome 1 Gene Product

Demolombe, Sophie; Baró, Isabelle; Péreón, Yann; Bliek, Jet; Mohammad-Panah, Raha; Pollard, H.; Morid, Shabnam; Mannens, Marcel; Wilde, Arthur A.M.; Barhanin, Jacques; Charpentier, Flavien; Escande, Denis

doi:10.1074/jbc.273.12.6837

Cited by 84 publications

(66 citation statements)

References 21 publications

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“…One of the two alternatively spliced KvLQT1 variants forms the functional K ϩ channel. The other, a COOH-terminal truncated isoform, does not possess channel function but exerts a strong dominant-negative effect on channel function (4). It has been shown that transgenic mice overexpressing the truncated isoform develop several interesting cardiac arrhythmias (5) and that, in humans with the recessive form of the long QT syndrome (Jervell and Lange-Nielsen syndrome), mutations in the dominant-negative isoform correlate with the phenotype of the cardiac arrhythmia (24).…”

Section: Discussionmentioning

confidence: 99%

cAMP-dependent activation of the renal-specific Na⁺-K⁺-2Cl⁻cotransporter is mediated by regulation of cotransporter trafficking

Meade

Hoover

Plata

et al. 2003

American Journal of Physiology-Renal Physiology

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. cAMP-dependent activation of the renal-specific Na ϩ -K ϩ -2Cl Ϫ cotransporter is mediated by regulation of cotransporter trafficking. Am J Physiol Renal Physiol 284: F1145-F1154, 2003. First published February 25, 2003 10.1152/ajprenal.00421.2002The murine apical bumetanide-sensitive Na ϩ -K ϩ -2Cl Ϫ cotransporter gene (mBSC1) exhibits two spliced isoform products that differ at the COOH-terminal domain. A long COOH-terminal isoform (L-mBSC1) encodes the Na ϩ -K ϩ -2Cl Ϫ cotransporter, and a short isoform (S-mBSC1) exerts a dominant-negative effect on L-mBSC1 cotransporter activity that is abrogated by cAMP. However, the mechanism of this dominant-negative effect was not clear. In this study, we used confocal microscopic analysis of an enhanced green fluorescent protein (EGFP) fusion construct (L-mBSC1-EGFP) expressed to characterize the surface expression of the L-BSC1 isoform in Xenopus laevis oocytes. Functional expression was also assessed in L-mBSC1-injected oocytes by measuring the bumetanide-sensitive 86 Rb ϩ uptake. Oocytes injected with L-mBSC1-EGFP cRNA developed a distinct plasma membrane-associated fluorescence that colocalized with the fluorescent membrane dye FM 4-64. The fluorescence intensity in L-mBSC1-EGFP oocytes did not change after cAMP was added to the extracellular medium. In contrast, L-mBSC1-EGFP fluorescence intensity was reduced in a dose-dependent manner, with coexpression of S-mBSC1. The inhibitory effect of S-mBSC1 was abrogated by cAMP. Finally, the exocytosis inhibitor colchicine blocked the effect of cAMP on the L-mBSC1-EGFP/S-mBSC1-coinjected oocytes. All changes in L-mBSC1 surface expression correlated with modification of bumetanide-sensitive 86 Rb ϩ uptake. Our data suggest that the dominant-negative effect of S-mBSC1 on L-mBSC1 transport function is due to the effects of the cotransporter on trafficking.

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Section: Discussionmentioning

confidence: 99%

cAMP-dependent activation of the renal-specific Na⁺-K⁺-2Cl⁻cotransporter is mediated by regulation of cotransporter trafficking

Meade

Hoover

Plata

et al. 2003

American Journal of Physiology-Renal Physiology

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“…Native cardiac transcripts encoding truncated versions of the human KCNQ1 channel selectively suppress KCNQ1 currents in a manner analogous to SK3-1B. 63,64 Similarly, native transcripts encoding nonfunctional variants of several other types of channels have been reported to silence their functional counterparts. These include KCNQ2, 65 Kv8.1, 66 Kv9.1 and Kv9.2, 67 and Ca v 2.2.…”

Section: Discussionmentioning

confidence: 99%

Novel truncated isoform of SK3 potassium channel is a potent dominant-negative regulator of SK currents: implications in schizophrenia

et al. 2003

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The small-conductance calcium-activated K þ channel SK3 (SKCa3/KCNN3) regulates electrical excitability and neurotransmitter release in monoaminergic neurons, and has been implicated in schizophrenia, ataxia and anorexia nervosa. We have identified a novel SK3 transcript, SK3-1B that utilizes an alternative first exon (exon 1B), but is otherwise identical to SK3. SK3-1B, mRNA is widely distributed in human tissues and is present at 20-60% of SK3 in the brain. The SK3-1B protein lacks the N-terminus and first transmembrane segment, and begins eight residues upstream of the second transmembrane segment. When expressed alone, SK3-1B did not produce functional channels, but selectively suppressed endogenous SK3 currents in the pheochromocytoma cell line, PC12, in a dominant-negative fashion. This dominant inhibitory effect extended to other members of the SK subfamily, but not to voltage-gated K þ channels, and appears to be due to intracellular trapping of endogenous SK channels. The effect of SK3-1B expression is very similar to that produced by expression of the rare SK3 truncation allele, SK3-D, found in a patient with schizophrenia. Regulation of SK3 and SK3-1B levels may provide a potent mechanism to titrate neuronal firing rates and neurotransmitter release in monoaminergic neurons, and alterations in the relative abundance of these proteins could contribute to abnormal neuronal excitability, and to the pathogenesis of schizophrenia.

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“…Mutant truncated channel proteins with dominant-inhibitory activity underlie several channelopathies including the long QT syndrome, episodic ataxia-1, benign familial neonatal convulsion and Andersen's syndrome. Truncation mutations in KCNQ1 (KvLQT1) and KCNH2 (HERG) cause dominantly inherited forms of Long-QT syndrome via suppression of delayed rectifier K ϩ channels that contribute to the repolarization phase of the cardiac action potential (47). Similar truncation mutants of Kv1.1 underlie episodic ataxia type-1 (49,64), and truncation mutants of KCNQ2 and KCNQ3 are responsible for benign familial neonatal convulsion.…”

Section: Dominant-negative Suppression By Sk3-1c Is Associated With Imentioning

confidence: 99%

“…tissues (7, 16, 22, 40 -49). However, experiments in heterologous expression systems have shown them to act as specific dominant-negative suppressors of their functional counterparts (7,16,22,42,(45)(46)(47)(48). Since SK3-1C did not produce functional channels when expressed heterologously in mammalian cells (data not shown), we used the approach described for other non-functional K ϩ channel isoforms to ascertain whether SK3-1C exhibits dominantinhibitory activity.…”

Section: Sk3-1c Transcripts Are Present In Human Hematopoietic and Mumentioning

confidence: 99%

SK3-1C, a Dominant-negative Suppressor of SKCa and IKCa Channels

Kolski-Andreaco

Tomita

Shakkottai

et al. 2004

Journal of Biological Chemistry

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Small conductance Ca 2؉ -activated K ؉ channels, products of the SK1-SK3 genes, regulate membrane excitability both within and outside the nervous system. We report the characterization of a SK3 variant (SK3-1C) that differs from SK3 by utilizing an alternative first exon (exon 1C) in place of exon 1A used by SK3, but is otherwise identical to SK3. Quantitative RT-PCR detected abundant expression of SK3-1C transcripts in human lymphoid tissues, skeletal muscle, trachea, and salivary gland but not the nervous system. SK3-1C did not produce functional channels when expressed alone in mammalian cells, but suppressed SK1, SK2, SK3, and IKCa1 channels, but not BK Ca or K V channels. Confocal microscopy revealed that SK3-1C sequestered SK3 protein intracellularly. Dominant-inhibitory activity of SK3-1C was not due to a nonspecific calmodulin sponge effect since overexpression of calmodulin did not reverse SK3-1C-mediated intracellular trapping of SK3 protein, and calmodulin-Ca 2؉ -dependent inactivation of Ca V channels was not affected by SK3-1C overexpression. Deletion analysis identified a dominant-inhibitory segment in the SK3-1C C terminus that resembles tetramerization-coiled-coiled domains reported to enhance tetramer stability and selectivity of multimerization of many K ؉ channels. SK3-1C may therefore suppress calmodulin-gated SK Ca /IK Ca channels by trapping these channel proteins intracellularly via subunit interactions mediated by the dominant-inhibitory segment and thereby reduce functional channel expression on the cell surface. Such family-wide dominant-negative suppression by SK3-1C provides a powerful mechanism to titrate membrane excitability and is a useful approach to define the functional in vivo role of these channels in diverse tissues by their targeted silencing.

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A Dominant Negative Isoform of the Long QT Syndrome 1 Gene Product

Cited by 84 publications

References 21 publications

cAMP-dependent activation of the renal-specific Na⁺-K⁺-2Cl⁻cotransporter is mediated by regulation of cotransporter trafficking

cAMP-dependent activation of the renal-specific Na⁺-K⁺-2Cl⁻cotransporter is mediated by regulation of cotransporter trafficking

Novel truncated isoform of SK3 potassium channel is a potent dominant-negative regulator of SK currents: implications in schizophrenia

SK3-1C, a Dominant-negative Suppressor of SKCa and IKCa Channels

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A Dominant Negative Isoform of the Long QT Syndrome 1 Gene Product

Cited by 84 publications

References 21 publications

cAMP-dependent activation of the renal-specific Na+-K+-2Cl−cotransporter is mediated by regulation of cotransporter trafficking

cAMP-dependent activation of the renal-specific Na+-K+-2Cl−cotransporter is mediated by regulation of cotransporter trafficking

Novel truncated isoform of SK3 potassium channel is a potent dominant-negative regulator of SK currents: implications in schizophrenia

SK3-1C, a Dominant-negative Suppressor of SKCa and IKCa Channels

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cAMP-dependent activation of the renal-specific Na⁺-K⁺-2Cl⁻cotransporter is mediated by regulation of cotransporter trafficking

cAMP-dependent activation of the renal-specific Na⁺-K⁺-2Cl⁻cotransporter is mediated by regulation of cotransporter trafficking