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Dendrotoxin-binding brain membrane protein displays a K+ channel activity that is stimulated by both cAMP-dependent
1Centre de Biochimie du Centre National de la Recherche Scientifique, Parc Valrose, Nice, France.
Abstract:
The purified protein that binds the K+ channel ligands dendrotoxin I and mast cell degranulating peptide can be phosphorylated by cAMP-dependent protein kinase and by an endogenous protein kinase, which may be a specific K+ channel kinase. Phosphorylations take place on the toxin-binding subunit, a polypeptide of 76-80 kDa. Phosphorylation by both kinases leads to activation of the reconstituted dendrotoxin-sensitive K+ channel.
Insights
The purified protein binding K+ channel toxins can be phosphorylated, activating the channel. This phosphorylation occurs on the toxin-binding subunit by protein kinases.
Area of Science:
- Biochemistry
- Molecular Biology
- Neuroscience
Background:
- Potassium channels (K+) are crucial for neuronal excitability.
- Dendrotoxin I and mast cell degranulating peptide are known ligands that interact with specific K+ channels.
- Regulation of K+ channel activity by post-translational modifications like phosphorylation is a key area of research.
Purpose of the Study:
- To investigate the phosphorylation of the K+ channel toxin-binding protein.
- To identify the kinases involved in this phosphorylation process.
- To determine the functional consequences of phosphorylation on K+ channel activity.
Main Methods:
- Protein purification of the K+ channel toxin-binding subunit.
- In vitro kinase assays using cAMP-dependent protein kinase and an endogenous kinase.
- Electrophysiological reconstitution assays to measure channel activity.
Main Results:
- The purified toxin-binding protein subunit (76-80 kDa) undergoes phosphorylation.
- Both cAMP-dependent protein kinase and an endogenous protein kinase (potentially a specific K+ channel kinase) phosphorylate the subunit.
- Phosphorylation by either kinase leads to the activation of the reconstituted dendrotoxin-sensitive K+ channel.
Conclusions:
- The toxin-binding subunit of the K+ channel is a substrate for protein kinases.
- Phosphorylation is a regulatory mechanism that can modulate K+ channel function, specifically activating dendrotoxin-sensitive channels.
- This finding suggests a novel pathway for regulating neuronal excitability via K+ channel phosphorylation.