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Solubilization of sodium channel from human brain
C de Rycker1, C Grandfils, L Bettendorff
1Laboratoire de Biochimie Générale et Comparée, Université de Liège, Belgium.
Journal of Neurochemistry
|February 1, 1989
Summary
Researchers identified and characterized tetrodotoxin (TTX) receptors in human brain homogenates. Optimal conditions for solubilizing these TTX receptors using Nonidet P-40 were determined, enhancing future studies.
Area of Science:
- Neuroscience
- Pharmacology
- Biochemistry
Background:
- Tetrodotoxin (TTX) is a potent neurotoxin known to block voltage-gated sodium channels.
- Understanding TTX binding sites in the human brain is crucial for neurological research and drug development.
- Previous studies have focused on TTX interactions in non-human tissues, necessitating human brain-specific characterization.
Purpose of the Study:
- To characterize the binding properties of [3H]tetrodotoxin in human brain homogenates.
- To investigate the solubilization of the tetrodotoxin receptor from human brain membranes.
- To determine optimal conditions for maintaining the binding activity of the solubilized tetrodotoxin receptor.
Main Methods:
- Radioligand binding assays using [3H]tetrodotoxin to determine binding affinity (KD) and receptor density (Bmax).
- Detergent-based solubilization of membrane proteins using Nonidet P-40.
- Optimization of solubilization parameters including detergent concentration, pH, and duration.
- Assessment of binding activity in the presence of exogenous lipids like phosphatidylcholine.
Main Results:
- [3H]Tetrodotoxin binds to a single class of receptor sites in human brain homogenates with a KD of 9.1 nM and Bmax of 5.9 pmol/mg protein at 0°C.
- Nonidet P-40 effectively solubilizes up to 38% of TTX receptor sites.
- Optimal solubilization occurs within 15 minutes at pH 6.8.
- Exogenous phosphatidylcholine stabilizes the soluble receptor, particularly at a phosphatidylcholine/detergent ratio of 1:5.
Conclusions:
- A specific tetrodotoxin receptor exists in the human brain with defined binding characteristics.
- Nonidet P-40 is an effective detergent for solubilizing this receptor, with specific parameters optimizing yield and stability.
- The addition of phosphatidylcholine is critical for preserving the binding activity of the solubilized tetrodotoxin receptor, facilitating further biochemical and functional studies.