WIN 17317-3, a New High-Affinity Probe for Voltage-Gated Sodium Channels
- 1 August 1999
- journal article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 38 (34), 11137-11146
- https://doi.org/10.1021/bi990336p
Abstract
The iminodihydroquinoline WIN 17317-3 was previously shown to inhibit selectively the voltage-gated potassium channels, Kv1.3 and Kv1.4 [Hill, R. J., et al. (1995) Mol.Pharmacol.48, 98−104; Nguyen, A., et al. (1996) Mol.Pharmacol.50, 1672−1679]. Since these channels are found in brain, radiolabeled WIN 17317-3 was synthesized to probe neuronal Kv1 channels. In rat brain synaptic membranes, [3H]WIN 17317-3 binds reversibly and saturably to a single class of high-affinity sites (Kd 2.2 ± 0.3 nM; Bmax 5.4 ± 0.2 pmol/mg of protein). However, the interaction of [3H]WIN 17317-3 with brain membranes is not sensitive to any of several well-characterized potassium channel ligands. Rather, binding is modulated by numerous structurally unrelated sodium channel effectors (e.g., channel toxins, local anesthetics, antiarrhythmics, and cardiotonics). The potency and rank order of effectiveness of these agents in affecting [3H]WIN 17317-3 binding is consistent with their known abilities to modify sodium channel activity. Autoradiograms of rat brain sections indicate that the distribution of [3H]WIN 17317-3 binding sites is in excellent agreement with that of sodium channels. Furthermore, WIN 17317-3 inhibits sodium currents in CHO cells stably transfected with the rat brain IIA sodium channel with high affinity (Ki 9 nM), as well as agonist-stimulated 22Na uptake in this cell line. WIN 17317-3 interacts similarly with skeletal muscle sodium channels but is a weaker inhibitor of the cardiac sodium channel. Together, these results demonstrate that WIN 17317-3 is a new, high-affinity, subtype-selective ligand for sodium channels and is a potent blocker of brain IIA sodium channels.Keywords
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