Abstract
Alterations in expression patterns of α4β2 nicotinic acetylcholine receptors have been demonstrated to alter cholinergic neurotransmission and are implicated in neurologic disorders, including autism, nicotine addiction, Alzheimer’s disease, and Parkinson’s disease. Positive allosteric modulators (PAMs) represent promising new leads in the development of therapeutic agents for the treatment of these disorders. This study investigates the involvement of the β2-containing subunit interfaces of α4β2 receptors in the modulation of acetylcholine (ACh)-induced responses by the PAM desformylflustrabromine (dFBr). Eight amino acids on the principal face of the β2 subunit were mutated to alanine to explore the involvement of this region in the potentiation of ACh-induced currents by dFBr. ACh-induced responses obtained from wild-type and mutant α4β2 receptors expressed in Xenopus laevis oocytes were recorded in the presence and absence of dFBr using two-electrode voltage clamp electrophysiology. Wild-type and mutant receptors were expressed in both high and low ACh sensitivity isoforms by using biased injection ratios of 1:5 or 5:1 α4 to β2 complementary RNA. Mutations were made in the B, C, and A loops of the principal face of the β2 subunit, which are regions not involved in the binding of ACh. Mutant β2(Y120A) significantly eliminated dFBr potency in both isoform preparations. Several other mutations altered dFBr potentiation levels in both preparations. Our findings support the involvement of the principal face of the β2 subunit in dFBr modulation of ACh-induced responses. Findings from this study will aid in the improved design of dFBr-like PAMs for potential therapeutic use.
Footnotes
- Received February 23, 2015.
- Accepted May 22, 2015.
This research was supported bythe National Institutes of Health National Center for Research Resources ([Grant 5P20-RR016466], Alaska Institutional Development Award Network of Biomedical Research Excellence Program); and the National Institutes of Health National Institutes of Neurologic Disorders and Stroke [Grant 1R01-NS066059].
Weltzin MM (2011) Investigation of the Allosteric Modulators Desformylflustrabromine and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) Interactions on Nicotinic Acetylcholine Receptors. Doctoral dissertation, University of Alaska Fairbanks, Fairbanks, AK.
Part of this work was presented as follows: Weltzin MM and Schulte MK (2011) Non-orthosteric subunit faces are involved in α4β2 nAChR responses to acetylcholine and desformylflustrabromine in high and low sensitive receptor preparations. Neuroscience 2011; 2011 Nov 12–16; Washington, DC.
- Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics
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