Kvβ Subunit Oxidoreductase Activity and Kv1 Potassium Channel Trafficking

Campomanes, Claire R.; Carroll, Karen; Manganas, Louis N.; Hershberger, Marcia E.; Gong, Belvin; Antonucci-Durgan, Dana; Rhodes, Kenneth J.; Trimmer, James S.

doi:10.1074/jbc.m110276200

Cited by 87 publications

(82 citation statements)

References 53 publications

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“…3B) (23, 24). We focused on these two sites because extensive previous work shows that mutations at these residues impair redox sensing without influencing protein expression or trafficking (23,24,30). To confirm that the Drosophila Hk D260 and K289 mutations do not affect protein expression or trafficking, they were tested in a GFP-tagged K isoform of Hk, and they express at equivalent or higher levels relative to WT Hk with no discernible changes in cellular protein distribution (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Structural analysis of fly and mammalian Kvβ proteins reveal that they are functional AKRs (17)(18)(19)(20)(21), measured by using heterologous expression systems (22)(23)(24). To determine whether the loss of the CRY-mediated l-LNv light response in hk −/− is a result of the loss of the redox sensor in this Kvβ subunit, we tested a matrix of genetic rescue experiments in the hk −/− genetic background by LNv-targeted expression of functional WT Hk or point mutants that disable the enzymatic activity of Kvβ without affecting protein expression levels (23,24,30). Fig.…”

Section: Resultsmentioning

confidence: 99%

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CRYPTOCHROME-mediated phototransduction by modulation of the potassium ion channel β-subunit redox sensor

Fogle

Baik

Houl

et al. 2015

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

121

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Blue light activation of the photoreceptor CRYPTOCHROME (CRY) evokes rapid depolarization and increased action potential firing in a subset of circadian and arousal neurons in Drosophila melanogaster. Here we show that acute arousal behavioral responses to blue light significantly differ in mutants lacking CRY, as well as mutants with disrupted opsin-based phototransduction. Lightactivated CRY couples to membrane depolarization via a well conserved redox sensor of the voltage-gated potassium (K + ) channel β-subunit (Kvβ) Hyperkinetic (Hk). The neuronal light response is almost completely absent in hk −/− mutants, but is functionally rescued by genetically targeted neuronal expression of WT Hk, but not by Hk point mutations that disable Hk redox sensor function. Multiple K + channel α-subunits that coassemble with Hk, including Shaker, Ether-a-go-go, and Ether-a-go-go-related gene, are ion conducting channels for CRY/Hk-coupled light response. Light activation of CRY is transduced to membrane depolarization, increased firing rate, and acute behavioral responses by the Kvβ subunit redox sensor.phototransduction | potassium channel | redox | cryptochrome

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

CRYPTOCHROME-mediated phototransduction by modulation of the potassium ion channel β-subunit redox sensor

Fogle

Baik

Houl

et al. 2015

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

121

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“…brane. To test this possibility live and nonpermeablized cells were treated with proteinase K, which is known to cleave extracellular exposed ectodomains (9,22). To ensure that the proteinase K cleavage is surface limited, all immunoblots were stripped and reprobed for an endogenous intracellular protein, CASK.…”

Section: Resultsmentioning

confidence: 99%

Identification of a COOH-terminal Segment Involved in Maturation and Stability of Human Ether-a-go-go-related Gene Potassium Channels

Akhavan

Atanasiu

Shrier

2003

Journal of Biological Chemistry

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Mutations in the potassium channel encoded by the human ether-a-go-go-related gene (HERG) have been linked to the congenital long QT syndrome (LQTS), a cardiac disease associated with an increased preponderance of ventricular arrhythmias and sudden death. The COOH terminus of HERG harbors a large number of LQTS mutations and its removal prevents functional expression for reasons that remain unknown. In this study, we show that the COOH terminus of HERG is required for normal trafficking of the ion channel. We have identified a region critical for trafficking between residues 860 and 899 that includes a novel missense mutation at amino acid 861 (HERG N861I ). Truncations or deletion of residues 860 -899, characterized in six different expression systems including a cardiac cell line, resulted in decreased expression levels and an absence of the mature glycosylated form of the HERG protein. Deletion of this region did not interfere with the formation of tetramers but caused retention of the assembled ion channels within the endoplasmic reticulum. Consequently, removal of residues 860 -899 resulted in the absence of the ion channels from the cell surface and a more rapid turnover rate than the wild type channels, which was evident very early in biogenesis. This study reveals a novel role of the COOH terminus in the normal biogenesis of HERG channels and suggests defective trafficking as a common mechanism for abnormal channel function resulting from mutations of critical COOH-terminal residues, including the LQTS mutant HERG N861I . The long QT syndrome (LQTS)1 is a congenital heart disorder characterized by delayed cardiac action potential repolarization and a prolongation of the QT interval. This leads to an increased susceptibility of the heart to potentially sustained ventricular tachyarrhythmias that cause syncope and sudden death. Molecular genetic studies have identified five genes linked to LQTS including the human ether-a-go-go-related gene (HERG) (1). HERG encodes the ␣-subunit of the rapidly activating delayed rectifier current I Kr and consists of six transmembrane domains as well as NH 2 -and COOH-terminal cytoplasmic tails (2, 3). Over 90 mutations distributed throughout HERG have been linked to the LQTS, most of which reside in the intracellular tail regions of the channel protein (4, 5). Earlier electrophysiological and structural analysis have emphasized abnormal HERG function as a common manifestation of mutations in the NH 2 terminus (6 -8). In contrast, studies of COOH-terminal mutations suggest that the pathology is because of the absence of HERG channels from the cell surface (9 -12). This phenotype may be caused by improper folding of newly synthesized HERG polypeptides, in a fashion similar to that described for the ⌬F508 allele of CFTR (CFTR⌬F508). CFTR⌬F508 is recognized by the endoplasmic reticulum (ER) quality control machinery and is rapidly degraded before being processed in the Golgi apparatus (13). As a consequence, these molecules are prevented from journeying through the secretory ...

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“…As a first step toward characterizing Kv1.2 phosphorylation, we subjected endogenous Kv1.2 in crude rat brain membranes (RBM) and recombinant rat Kv1.2 expressed in HEK293 cells to digestion with alkaline phosphatase (AP). Kv1.2 was expressed in HEK293 cells without and with auxiliary Kv␤2 subunits to alter the relative proportions of ER and cell-surface pools (13)(14)(15). The high M r cell-surface form of both native brain Kv1.2 and recombinant Kv1.2 from HEK293 cells underwent large shifts in M r upon AP treatment ( Fig.…”

Section: Kv12 Is Phosphorylated Inmentioning

confidence: 99%

Trafficking-dependent phosphorylation of Kv1.2 regulates voltage-gated potassium channel cell surface expression

Yang¹,

Vacher²,

Park³

et al. 2007

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

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Kv1.2 ␣-subunits are components of low-threshold, rapidly activating voltage-gated potassium (Kv) channels in mammalian neurons. Expression and localization of Kv channels is regulated by trafficking signals encoded in their primary structure. Kv1.2 is unique in lacking strong trafficking signals and in exhibiting dramatic cell-specific differences in trafficking, which is suggestive of conditional trafficking signals. Here we show that a cluster of cytoplasmic C-terminal phosphorylation sites regulates Kv1.2 trafficking. Using tandem MS to analyze Kv1.2 purified from rat, human, and mouse brain, we identified in each sample in vivo phosphoserine (pS) phosphorylation sites at pS434, pS440, and pS441, as well as doubly phosphorylated pS440/pS441. We also found these sites, as well as pS449, on recombinant Kv1.2 expressed in heterologous cells. We found that phosphorylation at pS440/pS441 is present only on the post-endoplasmic reticulum (ER)/cell surface pool of Kv1.2 and is not detectable on newly synthesized and ER-localized Kv1.2, on which we did observe pS449 phosphorylation. Elimination of PS440/PS441 phosphorylation by mutation reduces cell-surface expression efficiency and functional expression of homomeric Kv1.2 channels. Interestingly, mutation of S449 reduces phosphorylation at pS440/pS441 and also decreases Kv1.2 cell-surface expression efficiency and functional expression. These mutations also suppress trafficking of Kv1.2/ Kv1.4 heteromeric channels, suggesting that incorporation of Kv1.2 into heteromeric complexes confers conditional phosphorylation-dependent trafficking to diverse Kv channel complexes. These data support Kv1.2 phosphorylation at these clustered C-terminal sites as playing an important role in regulating trafficking of Kv1.2-containing Kv channels.ion channel ͉ mass spectrometry ͉ proteomics ͉ brain ͉ phosphospecific V oltage-gated potassium, or Kv, channels that form as tetramers of Kv1 ␣-subunits play important and diverse roles in regulating excitability of axons, nerve terminals, and dendrites of mammalian neurons (1). The major Kv1 ␣-subunits in mammalian brain, Kv1.1, Kv1.2, and Kv1.4, are found predominantly in heterotetrameric channel complexes (2-4). Homotetrameric Kv1.2 channels form low-threshold, sustained-or delayed-rectifier Kv channels (5) and, when coassembled with other Kv1 ␣-subunits, can generate a diverse array of channel subtypes (6). In mammalian brain, Kv1.2 is found prominently along unmyelinated axons, in nerve terminals and/or in preterminal axon segments, at axon initial segments, and at juxtaparanodes of myelinated axons, but it is also present in the dendrites of some neurons (7). The physiological importance of Kv1.2 is underscored by the recent finding that Kv1.2 knockout mice have enhanced seizure susceptibility and die in the third postnatal week (8).Biosynthetic trafficking of Kv1 channels from their site of translation in the rough endoplasmic reticulum (ER) to the cell surface is governed by a set of intrinsic targeting motifs encoded in primary s...

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Kvβ Subunit Oxidoreductase Activity and Kv1 Potassium Channel Trafficking

Cited by 87 publications

References 53 publications

CRYPTOCHROME-mediated phototransduction by modulation of the potassium ion channel β-subunit redox sensor

CRYPTOCHROME-mediated phototransduction by modulation of the potassium ion channel β-subunit redox sensor

Identification of a COOH-terminal Segment Involved in Maturation and Stability of Human Ether-a-go-go-related Gene Potassium Channels

Trafficking-dependent phosphorylation of Kv1.2 regulates voltage-gated potassium channel cell surface expression

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