Effects of lobeline, a nicotinic receptor ligand, on the cloned Kv1.5.
Summary of "Effects of lobeline, a nicotinic receptor ligand, on the cloned Kv1.5."
The goal of the present study was to examine the effects of lobeline, an agonist at nicotinic receptors, on cloned Kv channels, Kv1.5, Kv3.1, Kv4.3, and human ether-a-gogo-related gene (HERG), which are stably expressed in Chinese hamster ovary (CHO) or human embryonic kidney 293 (HEK293) cells. Whole-cell patch-clamp experiments revealed that lobeline accelerated the decay rate of Kv1.5 inactivation, decreasing the current amplitude at the end of the pulse in a concentration-dependent manner with a half-maximal inhibitory concentration (IC(50)) value of 15.1 muM. Using a time constant for the time course of drug-channel interaction, the apparent association (k ( +1)), and dissociation rate (k (-1)) constants were 2.4 muMu(-1) s(-1) and 40.9 s(-1), respectively. The calculated K ( D ) was 17.0 muMu. Lobeline slowed the decay rate of the tail current, resulting in a tail crossover phenomenon. The inhibition of Kv1.5 by lobeline steeply increased at potentials between -10 and +10 mV, which corresponds to the voltage range of channel activation. At more depolarized potentials a weaker voltage dependence was observed (delta = 0.26). The voltage dependence of the steady-state activation curve was not affected by lobeline, but lobeline shifted the steady-state inactivation curve of Kv1.5 in the hyperpolarizing direction. Lobeline produced use-dependent inhibition of Kv1.5 at frequencies of 1 and 2 Hz, and slowed the recovery from inactivation. Lobeline also inhibited Kv3.1, Kv4.3, and HERG in a concentration-dependent manner, with IC(50) values of 21.7, 28.2, and 0.34 muM, respectively. These results indicate that lobeline produces a concentration-, time-, voltage-, and use-dependent inhibition of Kv1.5, which can be interpreted as an open-channel block mechanism.
Affiliation
Department of Physiology, Medical Research Center, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, Seoul, 137-701, South Korea.
Journal Details
This article was published in the following journal.
Name: Pflugers Archiv : European journal of physiology
ISSN: 1432-2013
Pages:
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/20734202
- DOI: http://dx.doi.org/10.1007/s00424-010-0868-3
Medical and Biotech [MESH] Definitions
Lobeline
An alkaloid that has actions similar to NICOTINE on nicotinic cholinergic receptors but is less potent. It has been proposed for a variety of therapeutic uses including in respiratory disorders, peripheral vascular disorders, insomnia, and smoking cessation.
Nicotinic Agonists
Drugs that bind to and activate nicotinic cholinergic receptors (RECEPTORS, NICOTINIC). Nicotinic agonists act at postganglionic nicotinic receptors, at neuroeffector junctions in the peripheral nervous system, and at nicotinic receptors in the central nervous system. Agents that function as neuromuscular depolarizing blocking agents are included here because they activate nicotinic receptors, although they are used clinically to block nicotinic transmission.
Osteoprotegerin
A secreted member of the TNF receptor superfamily that negatively regulates osteoclastogenesis. It is a soluble decoy receptor of RANK LIGAND that inhibits both CELL DIFFERENTIATION and function of OSTEOCLASTS by inhibiting the interaction between RANK LIGAND and RECEPTOR ACTIVATOR OF NUCLEAR FACTOR-KAPPA B.
Nicotinic Antagonists
Drugs that bind to nicotinic cholinergic receptors (RECEPTORS, NICOTINIC) and block the actions of acetylcholine or cholinergic agonists. Nicotinic antagonists block synaptic transmission at autonomic ganglia, the skeletal neuromuscular junction, and at central nervous system nicotinic synapses.
Receptor, Erbb-2
A cell surface protein-tyrosine kinase receptor that is found to be overexpressed in a significant number of adenocarcinomas. It has extensive homology to and can heterodimerize with the EGF receptor (RECEPTOR, EPIDERMAL GROWTH FACTOR), the erbB-3 receptor (RECEPTOR, ERBB-3) and the erbB-4 receptor. Activation of the erbB-2 receptor occurs during heterodimer formation with a ligand-bound erbB receptor family members.
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