Related Experiment Video
Updated: Jul 30, 2025
05:31
A Fluorescent Screening Assay for Identifying Modulators of GIRK Channels
Published on: April 24, 2012
14.4K
Oxidation Driven Reversal of PIP2-dependent Gating in GIRK2 Channels
Sun-Joo Lee1, Shoji Maeda2, Jian Gao1
1Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA.
Function (Oxford, England)
|May 11, 2023
Summary
Oxidation alters G protein-gated inward rectifier potassium (GIRK) channel function, causing loss of ligand sensitivity and increased basal activity. Specific cysteine residues are identified as key contributors to these oxidative effects.
Area of Science:
- Molecular and Cellular Physiology
- Ion Channel Function and Regulation
Background:
- G protein-gated inward rectifier K+ (GIRK, Kir3) channels are crucial for cellular electrical signaling, modulated by phosphoinositol-4,5-bisphosphate (PIP2), Gβγ, and Na+.
- Physiological conditions maintain GIRK channels in a low basal activity state with normal ligand sensitivity.
Purpose of the Study:
- To investigate the impact of oxidative stress on GIRK2 channel activity and ligand responsiveness.
- To identify molecular determinants responsible for altered GIRK channel function under oxidizing conditions.
Main Methods:
- Purification and functional characterization of GIRK2 channels under reducing and oxidizing environments.
- Site-directed mutagenesis of specific cysteine residues (C65 and C190) within the GIRK2 channel.
- Assessment of channel activity, PIP2, and Na+ dependence, and response to PIP2 inhibition.
Main Results:
- Oxidizing conditions induce anomalous GIRK2 channel behavior, including loss of PIP2 and Na+-dependent activation.
- Elevated basal channel activity and paradoxical inhibition by PIP2 were observed under oxidation.
- Mutagenesis revealed C65 is critical for PIP2/Na+-dependent activity loss, while C190 mediates elevated basal activity.
Conclusions:
- Oxidation significantly disrupts GIRK channel gating mechanisms and ligand interactions.
- Specific cysteine residues are redox-sensitive sites that dictate GIRK channel function under oxidative stress.
- Findings provide mechanistic insight into previous anomalous observations and highlight potential pathophysiological roles of GIRK channel oxidation.
Related Concept Videos
01:30Ligand-Gated Ion Channel Receptor: Gating Mechanism
2.3K
Ligand-gated ion channels are transmembrane proteins that play a vital role in intercellular communication and functions of the nervous system. They allow the influx of ions across the membrane once the neurotransmitter binds, allowing the subsequent transmission of electrical excitation across the neurons. Other ligand-gated ion channels, like the γ-aminobutyric acid (GABA) receptor, permit anions like chloride into the cells on the binding of the GABA molecule. Their entry into the cell...
2.3K
01:11IP3/DAG Signaling Pathway
12.2K
Membrane lipids such as phosphatidylinositol (PI) are precursors for several membrane-bound and soluble second messengers. Specific kinases phosphorylate PI and produce phosphorylated inositol phospholipids. One such inositol phospholipids are the phosphatidylinositol-4,5 bisphosphate [PI(4,5)P2], present in the inner half of the lipid bilayer. Upon ligand binding, GPCR stimulates Gq proteins to turn on phospholipase Cꞵ. Activated phospholipase Cꞵ cleaves PI(4,5)P2 and...
12.2K
01:42Phosphoinositides and PIPs
8.6K
Phosphoinositides are a group of phospholipids containing a glycerol backbone with two fatty acid chains and a phosphate attached to a myoinositol sugar ring. The inositol head group extends into the cytoplasm, where it is modified by adding phosphate groups to form phosphatidylinositol phosphates or PIPs.
Different phosphoinositides are synthesized and recruited on the cytosolic face of the plasma membrane. The localization of specific phosphoinositides concentrated in separate membrane...
Different phosphoinositides are synthesized and recruited on the cytosolic face of the plasma membrane. The localization of specific phosphoinositides concentrated in separate membrane...
8.6K
01:21G-Protein Gated Ion Channels
4.6K
GPCRs are primarily responsible for our sense of smell, taste, and vision. The binding of a sensory stimulus activates GPCR to stimulate effector proteins, many of which are ion channels in the sensory organs. GPCRs modulate the opening and closing of the target ion channels either directly by binding them, or by releasing second messengers that activate these channels. As ions move across the membrane, the membrane potential is altered, which induces an appropriate response.
Sensory...
Sensory...
4.6K
01:19Ligand-gated Ion Channels
12.5K
Ligand-gated ion channels are transmembrane proteins with a channel for ions to pass through and a binding site for a ligand. The channel opens only when a ligand attaches to the binding site.
Three Subfamilies of Ligand-gated Ion Channels
Ligand-gated ion channels fall into three subfamilies. The 'Cys-loop' includes the nicotinic acetylcholine receptors, γ-aminobutyric acid (GABA), glycine, and 5-hydroxytryptamine receptors. The second one is the 'Pore-loop' channels that...
Three Subfamilies of Ligand-gated Ion Channels
Ligand-gated ion channels fall into three subfamilies. The 'Cys-loop' includes the nicotinic acetylcholine receptors, γ-aminobutyric acid (GABA), glycine, and 5-hydroxytryptamine receptors. The second one is the 'Pore-loop' channels that...
12.5K
01:12Mechanically-gated Ion Channels
6.5K
Mechanically-gated ion channels are proteins found in eukaryotic and prokaryotic cell membranes that open in response to mechanical stress. Tension, compression, swelling, and shear stress can alter the conformation of the protein, opening a transmembrane channel that allows the passage of ions for signal transmission. In eukaryotes, mechanically-gated channels are distributed in several regions like the neurons, lungs, skin, bladder, and heart, where they play critical roles in numerous...
6.5K