Pentameric ligand gated ion channels' intracellular domain interaction with RIC3 chaperone.

Abstract

Pentameric ligand-gated ion channels (pLGICs) are cys-loop receptors important in transduction of electrical signals between neurons in the peripheral and central nervous system. Their significant role in neurotransmission has increased the research in neuropharmacology. Members of this protein family are found in mammals, but also in prokaryotes that can often incorporate additional domains whose roles are largely uncharacterized. pLGICs include nicotinic acetylcholinereceptors, gamma-amino butyric acid A receptors, glycine receptors and type 3 serotonin receptors (5HT3). These receptors are integral membrane protein complexes composed of five subunits that surround the central pore. Each subunit incorporates a large extracellular domain which contains the agonist-binding site, four transmembrane segments (TM1-4) which form the ion pore, a large intracellular domain (ICD) between TM3 and TM4, and a short extracellular C-terminal region. The ionotropic serotonin subtype-3 (5-HT3) receptor is of current interest as a therapeutic target in the treatment of alcohol abuse. Selective pharmacological antagonists reduce alcohol consumption in preclinical and clinical models. To date only two applications have been fully realized in the clinic: the treatment of emesis and irritable-bowel syndrome. Competitive antagonists, called setrons, target 5HT3R, are used in the management of nausea and vomiting associated with radiation and chemotherapies in cancer patients. These drugs interact with off-target subunits of the receptor and consequently lead to many undesired effects including headache and drowsiness. In order to understand and characterize effective control of neurotransmitter-gated pLGICs, we have explored the interaction of 5HT3R with RIC-3 chaperone which mediates functional expression of the channels. In the present study, synthetic pLGIC peptides were used to probe and characterize the interaction with RIC-3 in native sources such as mouse brains and neuronal cell lines.