AsKC11, a Kunitz Peptide from Anemonia sulcata, Is a Novel Activator of G Protein-Coupled Inward-Rectifier Potassium Channels.

Dongchen An,László Béress,Irina Gladkikh,Steve Peigneur,Ernesto Lopes Pinheiro-Junior,Jan Tytgat,Eivind A B Undheim,Elena Leychenko

doi:10.3390/md20020140

Abstract

(1) Background: G protein-coupled inward-rectifier potassium (GIRK) channels, especially neuronal GIRK1/2 channels, have been the focus of intense research interest for developing drugs against brain diseases. In this context, venom peptides that selectively activate GIRK channels can be seen as a new source for drug development. Here, we report on the identification and electrophysiological characterization of a novel activator of GIRK1/2 channels, AsKC11, found in the venom of the sea anemone Anemonia sulcata. (2) Methods: AsKC11 was purified from the sea anemone venom by reverse-phase chromatography and the sequence was identified by mass spectrometry. Using the two-electrode voltage-clamp technique, the activity of AsKC11 on GIRK1/2 channels was studied and its selectivity for other potassium channels was investigated. (3) Results: AsKC11, a Kunitz peptide found in the venom of A. sulcata, is the first peptide shown to directly activate neuronal GIRK1/2 channels independent from Gi/o protein activity, without affecting the inward-rectifier potassium channel (IRK1) and with only a minor effect on KV1.6 channels. Thus, AsKC11 is a novel activator of GIRK channels resulting in larger K+ currents because of an increased chord conductance. (4) Conclusions: These discoveries provide new insights into a novel class of GIRK activators.

Highlights

GIRK channels are activated by binding of the βγ subunit of Gi/o proteins (Gi/o(βγ)) which disassociates from the Gi/o(α) subunit following the activation of pertussis toxin (PTX)-sensitive G protein-coupled receptors (GPCRs) [6,7]
The activation of GIRK channels by GPCRs is a crucial part of signal transduction evoked by a diversity of GPCR agonists, including endogenous neurotransmitters such as acetylcholine, dopamine, opioids, serotonin, somatostatin, adenosine, and GABA, as well as exogenous molecules, such as WIN55,212-2 and CP55,940, which are the agonists of cannabinoid receptors [1,2,7,8]
To identify the novel activator of GIRK1/2 channels, we first tested the effects of venom fractions previously purified from the venom of Anemonia sulcata [25] on whole-cell currents in oocytes expressing GIRK1/2 channels

Summary

Introduction

G protein-coupled inward-rectifier potassium (GIRK/Kir3) channels are members of a large family of inward-rectifying potassium (Kir1-7) channels, which have been studied intensively for nearly three decades [1,2,3]. GIRK channels are activated by binding of the βγ subunit of Gi/o proteins (Gi/o(βγ)) which disassociates from the Gi/o(α) subunit following the activation of PTX-sensitive G protein-coupled receptors (GPCRs) [6,7]. The activation of GIRK channels by GPCRs is a crucial part of signal transduction evoked by a diversity of GPCR agonists, including endogenous neurotransmitters such as acetylcholine, dopamine, opioids, serotonin, somatostatin, adenosine, and GABA, as well as exogenous molecules, such as WIN55,212-2 and CP55,940, which are the agonists of cannabinoid receptors [1,2,7,8]

Methods

Results

Conclusion