Abstract:The activity of many proteins depends on the phosphoinositide (PI) content of the membrane. E.g., dynamic changes of the concentration of PI(4,5)P2 are cellular signals that regulate ion channels. The susceptibility of a channel to such dynamics depends on its affinity for PI(4,5)P2. Yet, measuring affinities for endogenous PIs has not been possible directly, but has relied largely on the response to soluble analogs, which may not quantitatively reflect binding to native lipids. Voltage-sensitive phosphatases … Show more
“…The mean time to the 70% maximum current (T 70 ) for R333K, R345K, R353K and R435Kwas 22.8 ± 3.7, 24.1 ± 1.9, 32.1 ± 2.6, and 17.9 ± 1.5 s, respectively (p<0.05 vs WT:9.5 ± 3.1 s). The slowed recovery after VSP reflects the reduced PIP 2 affinity (Rjasanow et al, 2015), further supporting for the reduced PIP 2 affinity of RK mutants. Taken together, these data suggest that methylation of KCNQ2 channel regulates its interaction with PIP 2 .10.7554/eLife.17159.022Figure 7.Methylation of KCNQ2 determines its PIP 2 affinity.( a ) Pooled data show 10 μM neomycin-induced rundown of WT (●) and R333K (○) KCNQ2 currents.…”
KCNQ channels are critical determinants of neuronal excitability, thus emerging as a novel target of anti-epileptic drugs. To date, the mechanisms of KCNQ channel modulation have been mostly characterized to be inhibitory via Gq-coupled receptors, Ca2+/CaM, and protein kinase C. Here we demonstrate that methylation of KCNQ by protein arginine methyltransferase 1 (Prmt1) positively regulates KCNQ channel activity, thereby preventing neuronal hyperexcitability. Prmt1+/- mice exhibit epileptic seizures. Methylation of KCNQ2 channels at 4 arginine residues by Prmt1 enhances PIP2 binding, and Prmt1 depletion lowers PIP2 affinity of KCNQ2 channels and thereby the channel activities. Consistently, exogenous PIP2 addition to Prmt1+/- neurons restores KCNQ currents and neuronal excitability to the WT level. Collectively, we propose that Prmt1-dependent facilitation of KCNQ-PIP2 interaction underlies the positive regulation of KCNQ activity by arginine methylation, which may serve as a key target for prevention of neuronal hyperexcitability and seizures.DOI:
http://dx.doi.org/10.7554/eLife.17159.001
“…The mean time to the 70% maximum current (T 70 ) for R333K, R345K, R353K and R435Kwas 22.8 ± 3.7, 24.1 ± 1.9, 32.1 ± 2.6, and 17.9 ± 1.5 s, respectively (p<0.05 vs WT:9.5 ± 3.1 s). The slowed recovery after VSP reflects the reduced PIP 2 affinity (Rjasanow et al, 2015), further supporting for the reduced PIP 2 affinity of RK mutants. Taken together, these data suggest that methylation of KCNQ2 channel regulates its interaction with PIP 2 .10.7554/eLife.17159.022Figure 7.Methylation of KCNQ2 determines its PIP 2 affinity.( a ) Pooled data show 10 μM neomycin-induced rundown of WT (●) and R333K (○) KCNQ2 currents.…”
KCNQ channels are critical determinants of neuronal excitability, thus emerging as a novel target of anti-epileptic drugs. To date, the mechanisms of KCNQ channel modulation have been mostly characterized to be inhibitory via Gq-coupled receptors, Ca2+/CaM, and protein kinase C. Here we demonstrate that methylation of KCNQ by protein arginine methyltransferase 1 (Prmt1) positively regulates KCNQ channel activity, thereby preventing neuronal hyperexcitability. Prmt1+/- mice exhibit epileptic seizures. Methylation of KCNQ2 channels at 4 arginine residues by Prmt1 enhances PIP2 binding, and Prmt1 depletion lowers PIP2 affinity of KCNQ2 channels and thereby the channel activities. Consistently, exogenous PIP2 addition to Prmt1+/- neurons restores KCNQ currents and neuronal excitability to the WT level. Collectively, we propose that Prmt1-dependent facilitation of KCNQ-PIP2 interaction underlies the positive regulation of KCNQ activity by arginine methylation, which may serve as a key target for prevention of neuronal hyperexcitability and seizures.DOI:
http://dx.doi.org/10.7554/eLife.17159.001
“…The degree of current inhibition rises with depolarisation with a V 1/2 value of 20 ± 2.2 mV. This voltage-sensitivity has been shown to be the consequence of the phosphatase titrating PI(4,5)P 2 in the plasma membrane as the PIP will decrease with increasing depolarisation4447. On the basis of its voltage sensitivity in these DrVSP co-expression experiments, the apparent affinity of TASK-2 for PI(4,5)P 2 should be close to that of Kv7.3 and Kir2.147.…”
Section: Resultsmentioning
confidence: 99%
“…It is well known that differences in the kinetics of deactivation of K + channels by VSPs reflect differences in the affinities of said channels for PI(4,5)P 2 . For example deactivation of Kir2.1-R228Q, a mutant channel with independently demonstrated weakened interaction with PI(4,5)P 2 as compared with WT Kir2.1, occurs with a faster time course upon VSP activation than in the WT channels47. We first examined TASK-2 channels carrying deletions in their C-terminus eliminating different portions of the C-terminus: Δ316, Δ417 and Δ455.…”
Section: Resultsmentioning
confidence: 99%
“…This result, apparently surprising in view of the well characterised requirement of an interaction of a polybasic motif in its C terminus and the most abundant phosphoinositide in the plasma membrane, PI(4,5)P 2 5455, has been explained on the basis of a lack of phospholipid specificity in the effect on TREK-122. It is puzzling that PI(4,5)P 2 apparent affinity of TASK-2 judged from the voltage-dependence of DrVSP effect47 would put this K 2P channel in a high affinity category together with Kir2.151 and Kv7.34956 (diC8 PI(4,5)P 2 EC 50 3–6 μM). Affinity for the long-chain PI(4,5)P 2 that is dephosphorylated by DrVSP may, however, be different from that for shorter diC8 form.…”
Section: Discussionmentioning
confidence: 99%
“…Based on the EC 50 for activation by diC8 PIP(4,5)P 2 , TASK-2 “affinity” would be intermediate and similar to that of the Kv7.2/Kv7.3 complex49. However, judged by the V 0.5 of the VSP effect it would be close to that of the higher affinity Kv7.347.…”
Two-pore domain K2P K+ channels responsible for the background K+ conductance and the resting membrane potential, are also finely regulated by a variety of chemical, physical and physiological stimuli. Hormones and transmitters acting through Gq protein-coupled receptors (GqPCRs) modulate the activity of various K2P channels but the signalling involved has remained elusive, in particular whether dynamic regulation by membrane PI(4,5)P2, common among other classes of K+ channels, affects K2P channels is controversial. Here we show that K2P K+ channel TASK-2 requires PI(4,5)P2 for activity, a dependence that accounts for its run down in the absence of intracellular ATP and its full recovery by addition of exogenous PI(4,5)P2, its inhibition by low concentrations of polycation PI scavengers, and inhibition by PI(4,5)P2 depletion from the membrane. Comprehensive mutagenesis suggests that PI(4,5)P2 interaction with TASK-2 takes place at C-terminus where three basic aminoacids are identified as being part of a putative binding site.
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