PKC and AMPK regulation of Kv1.5 potassium channels

Key points Progression of hypoxic pulmonary hypertension is thought to be due, in part, to suppression of voltage‐gated potassium channels (Kv) in pulmonary arterial smooth muscle by hypoxia, although the precise molecular mechanisms have been unclear.AMP‐activated protein kinase (AMPK) has been proposed to couple inhibition of mitochondrial metabolism by hypoxia to acute hypoxic pulmonary vasoconstriction and progression of pulmonary hypertension.Inhibition of complex I of the mitochondrial electron transport chain activated AMPK and inhibited Kv1.5 channels in pulmonary arterial myocytes.AMPK activation by 5‐aminoimidazole‐4‐carboxamide riboside, A769662 or C13 attenuated Kv1.5 currents in pulmonary arterial myocytes, and this effect was non‐additive with respect to Kv1.5 inhibition by hypoxia and mitochondrial poisons.Recombinant AMPK phosphorylated recombinant human Kv1.5 channels in cell‐free assays, and inhibited K+ currents when introduced into HEK 293 cells stably expressing Kv1.5.These results suggest that AMPK is the primary mediator of reductions in Kv1.5 channels following inhibition of mitochondrial oxidative phosphorylation during hypoxia and by mitochondrial poisons. AbstractProgression of hypoxic pulmonary hypertension is thought to be due, in part, to suppression of voltage‐gated potassium channels (Kv) in pulmonary arterial smooth muscle cells that is mediated by the inhibition of mitochondrial oxidative phosphorylation. We sought to determine the role in this process of the AMP‐activated protein kinase (AMPK), which is intimately coupled to mitochondrial function due to its activation by LKB1‐dependent phosphorylation in response to increases in the cellular AMP:ATP and/or ADP:ATP ratios. Inhibition of complex I of the mitochondrial electron transport chain using phenformin activated AMPK and inhibited Kv currents in pulmonary arterial myocytes, consistent with previously reported effects of mitochondrial inhibitors. Myocyte Kv currents were also markedly inhibited upon AMPK activation by A769662, 5‐aminoimidazole‐4‐carboxamide riboside and C13 and by intracellular dialysis from a patch‐pipette of activated (thiophosphorylated) recombinant AMPK heterotrimers (α2β2γ1 or α1β1γ1). Hypoxia and inhibitors of mitochondrial oxidative phosphorylation reduced AMPK‐sensitive K+ currents, which were also blocked by the selective Kv1.5 channel inhibitor diphenyl phosphine oxide‐1 but unaffected by the presence of the BKCa channel blocker paxilline. Moreover, recombinant human Kv1.5 channels were phosphorylated by AMPK in cell‐free assays, and K+ currents carried by Kv1.5 stably expressed in HEK 293 cells were inhibited by intracellular dialysis of AMPK heterotrimers and by A769662, the effects of which were blocked by compound C. We conclude that AMPK mediates Kv channel inhibition by hypoxia in pulmonary arterial myocytes, at least in part, through phosphorylation of Kv1.5 and/or an associated protein.

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“…; Andersen et al . ). Further studies will be aimed at identifying the AMPK phosphorylation sites on K v 1.5 and on associated β subunits.…”

Section: Discussionmentioning

confidence: 97%

AMP‐activated protein kinase inhibits K_v1.5 channel currents of pulmonary arterial myocytes in response to hypoxia and inhibition of mitochondrial oxidative phosphorylation

Moral-Sanz

Mahmoud

Eldstrom

et al. 2016

The Journal of Physiology

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“…This is the first report on aplysiatoxin derivatives with different absolute configurations at C9-C12 (1: 9S, 10R, 11S, 12S; 2: 9R, 10S, 11R, 12R) exhibiting potent potassium channel Kv1.5 blocking activities (IC 50 = 1.22 ± 0.22 µM and 2.85 ± 0.29 µM, respectively). It has been reported that activation of protein kinase C (PKC) may cause inhibition of Kv1.5 ion channels [37], while some of the aplysiatoxins can activate PKC kinase [10][11][12]38]. The classical structures of ATXs (debromoaplysiatoxin, neo-debromoaplysiatoxin A) have a PKC kinase recognition region and a conformational control region [39], and may possess the PKC activation as well as Kv1.5 inhibition activities.…”

Section: Resultsmentioning

confidence: 99%

Two New Neo-debromoaplysiatoxins—A Pair of Stereoisomers Exhibiting Potent Kv1.5 Ion Channel Inhibition Activities

et al. 2019

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A pair of stereoisomers possessing novel structures with 6/6/5 fused-ring systems, neo-debromoaplysiatoxin E (1) and neo-debromoaplysiatoxin F (2), were isolated from the marine cyanobacterium Lyngbya sp. Their structures were elucidated using various spectroscopic techniques including high resolution electrospray ionization mass spectroscopy (HRESIMS) and nuclear magnetic resonance (NMR). The absolute stereochemistry was determined by calculated electronic circular dichroism (ECD) and gauge-independent atomic orbital (GIAO) NMR shift calculation followed by DP4+ analysis. Significantly, this is the first report on aplysiatoxin derivatives with different absolute configurations at C9-C12 (1: 9S, 10R, 11S, 12S; 2: 9R, 10S, 11R, 12R). Compounds 1 and 2 exhibited potent blocking activities against Kv1.5 with IC 50 values of 1.22 ± 0.22 µM and 2.85 ± 0.29 µM, respectively.

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“…Furthermore, as noted above, the fact that AMPK is a serine threonine kinase suggested the capacity for regulation of processes outside of metabolism such as ion channel activity ( Figure 1), which our findings (Evans et al, 2005c;Ikematsu et al, 2011;Ross et al, 2011) and those of others have since confirmed. For example, AMPK may phosphorylate and "inactivate" the pore forming alpha subunit of multiple Ca 2+activated potassium channels (KCa1.1 and KCa3.1) (Klein et al, 2009;Ross et al, 2011), the voltage-gated potassium channel Kv1.5 (Andersen et al, 2015;Mia et al, 2012;Moral-Sanz et al, 2016) and the ATP-inhibited KATP channel (Kir6.2) (Chang et al, 2009), or may phosphorylate and "activate" Kv2.1 alpha subunits . Thereby AMPK has the potential to increase or decrease cell excitability, in a manner determined by both the cell-specific expression of its subunits and members of the ion channel superfamily, providing the capacity for system-level adjustments to whole-body metabolic status (Evans, 2006a).…”

Section: The Amp-activated Protein Kinasementioning

confidence: 99%

AMPK breathing and oxygen supply

Evans

2019

Respiratory Physiology & Neurobiology

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Regulation of breathing is critical to our capacity to accommodate deficits in oxygen availability and demand during, for example, sleep and ascent to altitude. Key to this are two reflex responses, hypoxic pulmonary vasoconstriction (HPV), which aids ventilation-perfusion matching at the lungs, and the hypoxic ventilatory response (HVR) which accelerates ventilation. In 2004 I proposed that HPV might be mediated by the AMP-activated protein kinase, which governs cell autonomous metabolic homeostasis. Pharmacological evidence was presented in support of this view, and the hypothesis extended to incorporate a role for AMPK in regulating carotid body afferent input responses during hypoxia and thus the HVR. The present article reviews our subsequent findings on these matters and those of others, which provide strong support for the view that AMPK mediates HPV. AMPK is also critical to the HVR, but against our expectations it is not required for carotid body activation during hypoxia. Contrary to current consensus in this respect, our findings suggest that AMPK deficiency blocks the HVR at the level of the brainstem, even when afferent input responses from the carotid body are normal. We have therefore revised our hypothesis on the HVR, now proposing that AMPK integrates local hypoxic stress at defined loci within the brainstem respiratory network with an index of peripheral hypoxic status, namely afferent chemosensory inputs. Nevertheless, in general outcomes are consistent with the original hypothesis, that the role of AMPK has evolved, through natural selection, to extend to the regulation of breathing, and thus oxygen and energy (ATP) supply to the whole body.

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PKC and AMPK regulation of Kv1.5 potassium channels

Cited by 31 publications

References 35 publications

AMP‐activated protein kinase inhibits K_v1.5 channel currents of pulmonary arterial myocytes in response to hypoxia and inhibition of mitochondrial oxidative phosphorylation

AMP‐activated protein kinase inhibits K_v1.5 channel currents of pulmonary arterial myocytes in response to hypoxia and inhibition of mitochondrial oxidative phosphorylation

Two New Neo-debromoaplysiatoxins—A Pair of Stereoisomers Exhibiting Potent Kv1.5 Ion Channel Inhibition Activities

AMPK breathing and oxygen supply

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PKC and AMPK regulation of Kv1.5 potassium channels

Cited by 31 publications

References 35 publications

AMP‐activated protein kinase inhibits Kv1.5 channel currents of pulmonary arterial myocytes in response to hypoxia and inhibition of mitochondrial oxidative phosphorylation

AMP‐activated protein kinase inhibits Kv1.5 channel currents of pulmonary arterial myocytes in response to hypoxia and inhibition of mitochondrial oxidative phosphorylation

Two New Neo-debromoaplysiatoxins—A Pair of Stereoisomers Exhibiting Potent Kv1.5 Ion Channel Inhibition Activities

AMPK breathing and oxygen supply

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AMP‐activated protein kinase inhibits K_v1.5 channel currents of pulmonary arterial myocytes in response to hypoxia and inhibition of mitochondrial oxidative phosphorylation

AMP‐activated protein kinase inhibits K_v1.5 channel currents of pulmonary arterial myocytes in response to hypoxia and inhibition of mitochondrial oxidative phosphorylation