Protein kinase C shifts the voltage dependence of KCNQ/M channels expressed in <i>Xenopus</i> oocytes

Nakajo, Koichi; Kubo, Yoshihiro

doi:10.1113/jphysiol.2005.094995

Cited by 45 publications

(55 citation statements)

References 34 publications

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“…Electrophysiological experiments show that, in HEK cells, PP2A-Bg increases the KCNQ2wt current amplitude (Figure 3). Since in HEK cells, KCNQ2 preferentially exists in a phosphorylated/inactive state, 23 these results suggest that PP2A, via its Bg-regulatory subunit stimulates the dephosphorylation of KCNQ2wt, and then increases channel activity. This current increase is not observed with the Q2-3H2-spliced isoform suggesting, in this case, a regulation pathway different from that of the wt channel.…”

Section: Pp2a-bc and Kcnq2 In Bipolar Diseasementioning

confidence: 81%

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PP2A-Bγ subunit and KCNQ2 K+ channels in bipolar disorder

Borsotto

Cavarec²,

Bouillot³

et al. 2006

Pharmacogenomics J

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Many bipolar affective disorder (BD) susceptibility loci have been identified but the molecular mechanisms responsible for the disease remain to be elucidated. In the locus 4p16, several candidate genes were identified but none of them was definitively shown to be associated with BD. In this region, the PPP2R2C gene encodes the Bg-regulatory subunit of the protein phosphatase 2A (PP2A-Bg). First, we identified, in two different populations, single nucleotide polymorphisms and risk haplotypes for this gene that are associated to BD. Then, we used the Bg subunit as bait to screen a human brain cDNA library with the yeast two-hybrid technique. This led us to two new splice variants of KCNQ2 channels and to the KCNQ2 channel itself. This unusual K þ channel has particularly interesting functional properties and belongs to a channel family that is already known to be implicated in several other monogenic diseases. In one of the BD populations, we also found a genetic association between the KCNQ2 gene and BD. We show that KCNQ2 splice variants differ from native channels by their shortened C-terminal sequences and are unique as they are active and exert a dominant-negative effect on KCNQ2 wild-type (wt) channel activity. We also show that the PP2A-Bg subunit significantly increases the current generated by KCNQ2wt, a channel normally inhibited by phosphorylation. The kinase glycogen synthase kinase 3 beta (GSK3b) is considered as an interesting target of lithium, the classical drug used in BD. GSK3b phosphorylates the KCNQ2 channel and this phosphorylation is decreased by Li þ .

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Section: Pp2a-bc and Kcnq2 In Bipolar Diseasementioning

confidence: 81%

“…A possible explanation of these results is that in HEK cells KCNQ2 channels are mostly present in a hyperphosphorylated/inactive state. 23 Thus, increasing the level of PP2A-Bg subunit, and consequently phosphatase activity, would be expected to lead to an increase of the channel activity.…”

Section: Cos Cell Expression Of Kcnq2wt and Splice Variant Channelsmentioning

confidence: 99%

PP2A-Bγ subunit and KCNQ2 K+ channels in bipolar disorder

Borsotto

Cavarec²,

Bouillot³

et al. 2006

Pharmacogenomics J

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“…PMA, a PKC activator, has been shown to produce a positive shift in the voltage dependence of KCNQ2 channels, while chelerythrine, a PKC inhibitor, attenuated the shift induced by muscarinic stimulation in the Xenopus oocytes expression system [9] . In results consistent with the previous studies, we also found that the effect of PMA on the KCNQ4 channels was antagonized by pretreatment with a PKC inhibitor, BIMI.…”

Section: Discussionmentioning

confidence: 99%

“…Effect of PKC activator on the KCNQ4 current PKC is an important regulator of KCNQ channels, as shown in previous work [9] . To test whether activation of PKC leads to a functional change of the KCNQ4 current in a Xenopus oocyte model system, PMA (a PKC activator) and BIMI (a PKC inhibitor) were used in this study.…”

Section: Human Kcnq4 Currents In Xenopus Oocytesmentioning

confidence: 99%

“…The inhibition of the metabolism of DAG by DAG kinase blockers cannot mimic the effect of muscarinic modulation by muscarinic agonist, and it has been suggested Functional study of the effect of phosphatase inhibitors on KCNQ4 channels expressed in Xenopus oocytes Tzu-rong SU 1 , Cay-huyen CHEN 2 , Shih-jen HUANG 2 , Chun-yi LEE 2 , Mao-chang SU 3 , Gwan-hong CHEN 4 , Shuan-yow LI 4 , Jiannjou YANG 4 , Min-jon LIN 4, * that activated PKC and its targets are not essential players in the acute muscarinic modulation of KCNQ channels in mammalian expression systems [8] . By contrast, the activation of PKC induced a large positive shift in the conductance-voltage curve for KCNQ channels expressed in Xenopus oocytes [9] . The activation of PKC had a different effect on KCNQ channels expressed in mammalian cells and Xenopus oocytes, which could be due to the different intracellular environment and basal levels of channel phosphorylation.…”

Section: Introductionmentioning

confidence: 99%

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Functional study of the effect of phosphatase inhibitors on KCNQ4 channels expressed in Xenopus oocytes

Su¹,

Chen²,

Huang³

et al. 2009

Acta Pharmacol Sin

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npg Introduction KCNQ4, a novel potassium channel, plays a part in regulating the membrane potential and function of various cell types in the body [1] . The KCNQ4 current is a low-threshold, slow activating and noninactivating current that is expressed in the outer hair cells of the cochlea, brain, and heart. Mutations in KCNQ4 give rise to an inherited syndrome of deafness [2] . Therefore, the regulatory pathways of KCNQ4 channels play an important role in adjusting the function of outer hair cells. The KCNQ gene subfamily is composed of five K + channels, KCNQ1 to KCNQ5. The KCNQ4 channel was included in the Kv nomenclature as Kv 7.4 (voltage-gated potassium channel subunit Kv7.4) [3] . The heteromers of KCNQ2/KCNQ3 underlie the neuronal M-current, which modulates neuronal excitability. Many intracellular messengers, eg, PIP2, IP3, diacylglycerol (DAG), calmodulin, calcineurin, activators/inhibitors of PKC, tyrosine kinases, and myosin light chain kinase, have been reported to modulate M currents [4][5][6] . Moreover, the A-kinase-anchoring protein AKAP150, which binds PKC, facilitates the inhibition of KCNQ2 current [7] . Analysis of recombinant KCNQ2 channels suggests that targeting of PKC through association with AKAP150 is important for inhibition. However, the effect of PKC activation on KCNQ channels is still controversial [8] . The inhibition of the metabolism of DAG by DAG kinase blockers cannot mimic the effect of muscarinic modulation by muscarinic agonist, and it has been suggested Aim: KCNQ4 channels play an important part in adjusting the function of cochlear outer hair cells. The aim of this study was to investigate the effects of ser/thr phosphatase inhibitors on human KCNQ4 channels expressed in Xenopus laevis oocytes. Methods: Synthetic cRNA encoding human KCNQ4 channels was injected into Xenopus oocytes. We used a two-electrode voltage clamp to measure the ion currents in the oocytes. Results: Wild-type KCNQ4 expressed in Xenopus oocytes showed the typical properties of slow activation kinetics and low threshold activation. The outward K + current was almost completely blocked by a KCNQ4 blocker, linopirdine (0.25 mmol/L). BIMI (a PKC inhibitor) prevented the effects of PMA (a PKC activator) on the KCNQ4 current, indicating that PKC may be involved in the regulation of KCNQ4 expressed in the Xenopus oocyte system. Treatment with the ser/thr phosphatase inhibitors, cyclosporine (2 µmol/L), calyculin A (2 µmol/L) or okadaic acid (1 µmol/L), caused a significant positive shift in V 1/2 and a decrease in the conductance of KCNQ4 channels. The V 1/2 was shifted from -14.6±0.5 to -6.4±0.4 mV by cyclosporine, -18.8±0.5 to -9.2±0.4 mV by calyculin A, and -14.1±0.5 to -0.7±0.6 mV by okadaic acid. Moreover, the effects of these phosphatase inhibitors (okadaic acid or calyculin A) on the induction of a positive shift of V 1/2 were augmented by further addition of PMA. Conclusion: These results indicate that ser/thr phosphatase inhibitors can induce a shift to more positive potentials of the activation ...

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Updating In Vivo and In Vitro Phosphorylation and Methylation Sites of Voltage-Gated Kv7.2 Potassium Channels

et al. 2017

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Voltage-gated Kv7.2 potassium channels regulate neuronal excitability. The gating of these channels is tightly controlled by various mediators and neurotransmitters acting via G protein-coupled receptors; the underlying signaling cascades involve phosphatidylinositol-4,5-bisphosphate (PIP ), Ca /calmodulin, and phosphorylation. Recent studies found that the PIP sensitivity of Kv7.2 channels is affected by two posttranslational modifications, phosphorylation and methylation, harboured within putative PIP -binding domains. In this study, we updated phosphorylation and methylation sites in Kv7.2 either heterologously expressed in mammalian cells or as GST-fusion proteins exposed to recombinant protein kinases by using LC-MS/MS. In vitro kinase assays revealed that CDK5, protein kinase C (PKC) alpha, PKA, p38 MAPK, CamKIIα, and GSK3β could mediate phosphorylation. Taken together, we provided a comprehensive map of phosphorylation and methylation in Kv7.2 within protein-protein and protein-lipid interaction domains. This may help to interpret the functional roles of individual PTM sites in Kv7.2 channels. All MS data are available via ProteomeXchange with the identifier PXD005567.

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Protein kinase C shifts the voltage dependence of KCNQ/M channels expressed in Xenopus oocytes

Cited by 45 publications

References 34 publications

PP2A-Bγ subunit and KCNQ2 K+ channels in bipolar disorder

PP2A-Bγ subunit and KCNQ2 K+ channels in bipolar disorder

Functional study of the effect of phosphatase inhibitors on KCNQ4 channels expressed in Xenopus oocytes

Updating In Vivo and In Vitro Phosphorylation and Methylation Sites of Voltage-Gated Kv7.2 Potassium Channels

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