Dataset Information

? Subunits Control the Effects of Human Kv4.3 Potassium Channel Phosphorylation.

ABSTRACT: The transient outward K⁺ current, I_to, activates early in the cardiac myocyte action potential, to begin repolarization. Human I_to is generated primarily by two Kv4.3 potassium channel ? subunit splice variants (Kv4.3L and Kv4.3S) that diverge only by a C-terminal, membrane-proximal, 19-residue stretch unique to Kv4.3L. Protein kinase C (PKC) phosphorylation of threonine 504 within the Kv4.3L-specific 19-residues mediates ?-adrenergic inhibition of I_to in human heart. Kv4.3 is regulated in human heart by various ? subunits, including cytosolic KChIP2b and transmembrane KCNEs, yet their impact on the functional effects of human Kv4.3 phosphorylation has not been reported. Here, this gap in knowledge was addressed using human Kv4.3 splice variants, T504 mutants, and human ? subunits. Subunits were co-expressed in Xenopus laevis oocytes and analyzed by two-electrode voltage-clamp, using phorbol 12-myristate 13-acetate (PMA) to stimulate PKC. Unexpectedly, KChIP2b removed the inhibitory effect of PKC on Kv4.3L (but not Kv4.3L threonine phosphorylation by PKC per-se), while co-expression with KCNE2, but not KCNE4, restored PKC-dependent inhibition of Kv4.3L-KChIP2b to quantitatively resemble previously reported effects of ?-adrenergic modulation of human ventricular I_to. In addition, PKC accelerated recovery from inactivation of Kv4.3L-KChIP2b channels and, interestingly, of both Kv4.3L and Kv4.3S alone. Thus, ? subunits regulate the response of human Kv4.3 to PKC phosphorylation and provide a potential mechanism for modifying the response of I_to to ?-adrenergic regulation in vivo.

SUBMITTER: Abbott GW

PROVIDER: S-EPMC5585193 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

β Subunits Control the Effects of Human Kv4.3 Potassium Channel Phosphorylation.

Abbott Geoffrey W GW

Frontiers in physiology 20170901

The transient outward K+ current, Ito, activates early in the cardiac myocyte action potential, to begin repolarization. Human Ito is generated primarily by two Kv4.3 potassium channel α subunit splice variants (Kv4.3L and Kv4.3S) that diverge only by a C-terminal, membrane-proximal, 19-residue stretch unique to Kv4.3L. Protein kinase C (PKC) phosphorylation of threonine 504 within the Kv4.3L-specific 19-residues mediates α-adrenergic inhibition of ...[more]

PMID: 28919864

Similar Datasets

Project description:Kv4 pore-forming subunits co-assemble with ?-subunits including KChIP2 and DPP6 and the resultant complexes conduct cardiac transient outward K+ current (Ito). Compound NS5806 has been shown to potentate Ito in canine cardiomyocytes; however, its effects on Ito in other species yet to be determined. We found that NS5806 inhibited native Ito in a concentration-dependent manner (0.1~30 ?M) in both mouse ventricular cardiomyocytes and human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), but potentiated Ito in the canine cardiomyocytes. In HEK293 cells co-transfected with cloned Kv4.3 (or Kv4.2) and ?-subunit KChIP2, NS5806 significantly increased the peak current amplitude and slowed the inactivation. In contrast, NS5806 suppressed the current and accelerated inactivation of the channels when cells were co-transfected with Kv4.3 (or Kv4.2), KChIP2 and another ?-subunit, DPP6-L (long isoform). Western blot analysis showed that DPP6-L was dominantly expressed in both mouse ventricular myocardium and hiPSC-CMs, while it was almost undetectable in canine ventricular myocardium. In addition, low level of DPP6-S expression was found in canine heart, whereas levels of KChIP2 expression were comparable among all three species. siRNA knockdown of DPP6 antagonized the Ito inhibition by NS5806 in hiPSC-CMs. Molecular docking simulation suggested that DPP6-L may associate with KChIP2 subunits. Mutations of putative KChIP2-interacting residues of DPP6-L reversed the inhibitory effect of NS5806 into potentiation of the current. We conclude that a pharmacological modulator can elicit opposite regulatory effects on Kv4 channel complex among different species, depending on the presence of distinct ?-subunits. These findings provide novel insight into the molecular design and regulation of cardiac Ito. Since Ito is a potential therapeutic target for treatment of multiple cardiovascular diseases, our data will facilitate the development of new therapeutic Ito modulators.

Dataset Information

? Subunits Control the Effects of Human Kv4.3 Potassium Channel Phosphorylation.

Publications

β Subunits Control the Effects of Human Kv4.3 Potassium Channel Phosphorylation.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets